documentation: add some commas where they are helpful

[git.git] / http.c

#include "git-compat-util.h"
#include "git-curl-compat.h"
#include "hex.h"
#include "http.h"
#include "config.h"
#include "pack.h"
#include "sideband.h"
#include "run-command.h"
#include "url.h"
#include "urlmatch.h"
#include "credential.h"
#include "version.h"
#include "pkt-line.h"
#include "gettext.h"
#include "trace.h"
#include "transport.h"
#include "packfile.h"
#include "protocol.h"
#include "string-list.h"
#include "object-file.h"
#include "object-store-ll.h"

static struct trace_key trace_curl = TRACE_KEY_INIT(CURL);
static int trace_curl_data = 1;
static int trace_curl_redact = 1;
long int git_curl_ipresolve = CURL_IPRESOLVE_WHATEVER;
int active_requests;
int http_is_verbose;
ssize_t http_post_buffer = 16 * LARGE_PACKET_MAX;

static int min_curl_sessions = 1;
static int curl_session_count;
static int max_requests = -1;
static CURLM *curlm;
static CURL *curl_default;

#define PREV_BUF_SIZE 4096

char curl_errorstr[CURL_ERROR_SIZE];

static int curl_ssl_verify = -1;
static int curl_ssl_try;
static const char *curl_http_version = NULL;
static const char *ssl_cert;
static const char *ssl_cert_type;
static const char *ssl_cipherlist;
static const char *ssl_version;
static struct {
        const char *name;
        long ssl_version;
} sslversions[] = {
        { "sslv2", CURL_SSLVERSION_SSLv2 },
        { "sslv3", CURL_SSLVERSION_SSLv3 },
        { "tlsv1", CURL_SSLVERSION_TLSv1 },
#ifdef GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_0
        { "tlsv1.0", CURL_SSLVERSION_TLSv1_0 },
        { "tlsv1.1", CURL_SSLVERSION_TLSv1_1 },
        { "tlsv1.2", CURL_SSLVERSION_TLSv1_2 },
#endif
#ifdef GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_3
        { "tlsv1.3", CURL_SSLVERSION_TLSv1_3 },
#endif
};
static const char *ssl_key;
static const char *ssl_key_type;
static const char *ssl_capath;
static const char *curl_no_proxy;
#ifdef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
static const char *ssl_pinnedkey;
#endif
static const char *ssl_cainfo;
static long curl_low_speed_limit = -1;
static long curl_low_speed_time = -1;
static int curl_ftp_no_epsv;
static const char *curl_http_proxy;
static const char *http_proxy_authmethod;

static const char *http_proxy_ssl_cert;
static const char *http_proxy_ssl_key;
static const char *http_proxy_ssl_ca_info;
static struct credential proxy_cert_auth = CREDENTIAL_INIT;
static int proxy_ssl_cert_password_required;

static struct {
        const char *name;
        long curlauth_param;
} proxy_authmethods[] = {
        { "basic", CURLAUTH_BASIC },
        { "digest", CURLAUTH_DIGEST },
        { "negotiate", CURLAUTH_GSSNEGOTIATE },
        { "ntlm", CURLAUTH_NTLM },
        { "anyauth", CURLAUTH_ANY },
        /*
         * CURLAUTH_DIGEST_IE has no corresponding command-line option in
         * curl(1) and is not included in CURLAUTH_ANY, so we leave it out
         * here, too
         */
};
#ifdef CURLGSSAPI_DELEGATION_FLAG
static const char *curl_deleg;
static struct {
        const char *name;
        long curl_deleg_param;
} curl_deleg_levels[] = {
        { "none", CURLGSSAPI_DELEGATION_NONE },
        { "policy", CURLGSSAPI_DELEGATION_POLICY_FLAG },
        { "always", CURLGSSAPI_DELEGATION_FLAG },
};
#endif

static struct credential proxy_auth = CREDENTIAL_INIT;
static const char *curl_proxyuserpwd;
static const char *curl_cookie_file;
static int curl_save_cookies;
struct credential http_auth = CREDENTIAL_INIT;
static int http_proactive_auth;
static const char *user_agent;
static int curl_empty_auth = -1;

enum http_follow_config http_follow_config = HTTP_FOLLOW_INITIAL;

static struct credential cert_auth = CREDENTIAL_INIT;
static int ssl_cert_password_required;
static unsigned long http_auth_methods = CURLAUTH_ANY;
static int http_auth_methods_restricted;
/* Modes for which empty_auth cannot actually help us. */
static unsigned long empty_auth_useless =
        CURLAUTH_BASIC
        | CURLAUTH_DIGEST_IE
        | CURLAUTH_DIGEST;

static struct curl_slist *pragma_header;
static struct curl_slist *no_pragma_header;
static struct string_list extra_http_headers = STRING_LIST_INIT_DUP;

static struct curl_slist *host_resolutions;

static struct active_request_slot *active_queue_head;

static char *cached_accept_language;

static char *http_ssl_backend;

static int http_schannel_check_revoke = 1;
/*
 * With the backend being set to `schannel`, setting sslCAinfo would override
 * the Certificate Store in cURL v7.60.0 and later, which is not what we want
 * by default.
 */
static int http_schannel_use_ssl_cainfo;

size_t fread_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
{
        size_t size = eltsize * nmemb;
        struct buffer *buffer = buffer_;

        if (size > buffer->buf.len - buffer->posn)
                size = buffer->buf.len - buffer->posn;
        memcpy(ptr, buffer->buf.buf + buffer->posn, size);
        buffer->posn += size;

        return size / eltsize;
}

int seek_buffer(void *clientp, curl_off_t offset, int origin)
{
        struct buffer *buffer = clientp;

        if (origin != SEEK_SET)
                BUG("seek_buffer only handles SEEK_SET");
        if (offset < 0 || offset >= buffer->buf.len) {
                error("curl seek would be outside of buffer");
                return CURL_SEEKFUNC_FAIL;
        }

        buffer->posn = offset;
        return CURL_SEEKFUNC_OK;
}

size_t fwrite_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
{
        size_t size = eltsize * nmemb;
        struct strbuf *buffer = buffer_;

        strbuf_add(buffer, ptr, size);
        return nmemb;
}

/*
 * A folded header continuation line starts with any number of spaces or
 * horizontal tab characters (SP or HTAB) as per RFC 7230 section 3.2.
 * It is not a continuation line if the line starts with any other character.
 */
static inline int is_hdr_continuation(const char *ptr, const size_t size)
{
        return size && (*ptr == ' ' || *ptr == '\t');
}

static size_t fwrite_wwwauth(char *ptr, size_t eltsize, size_t nmemb, void *p UNUSED)
{
        size_t size = eltsize * nmemb;
        struct strvec *values = &http_auth.wwwauth_headers;
        struct strbuf buf = STRBUF_INIT;
        const char *val;
        size_t val_len;

        /*
         * Header lines may not come NULL-terminated from libcurl so we must
         * limit all scans to the maximum length of the header line, or leverage
         * strbufs for all operations.
         *
         * In addition, it is possible that header values can be split over
         * multiple lines as per RFC 7230. 'Line folding' has been deprecated
         * but older servers may still emit them. A continuation header field
         * value is identified as starting with a space or horizontal tab.
         *
         * The formal definition of a header field as given in RFC 7230 is:
         *
         * header-field   = field-name ":" OWS field-value OWS
         *
         * field-name     = token
         * field-value    = *( field-content / obs-fold )
         * field-content  = field-vchar [ 1*( SP / HTAB ) field-vchar ]
         * field-vchar    = VCHAR / obs-text
         *
         * obs-fold       = CRLF 1*( SP / HTAB )
         *                ; obsolete line folding
         *                ; see Section 3.2.4
         */

        /* Start of a new WWW-Authenticate header */
        if (skip_iprefix_mem(ptr, size, "www-authenticate:", &val, &val_len)) {
                strbuf_add(&buf, val, val_len);

                /*
                 * Strip the CRLF that should be present at the end of each
                 * field as well as any trailing or leading whitespace from the
                 * value.
                 */
                strbuf_trim(&buf);

                strvec_push(values, buf.buf);
                http_auth.header_is_last_match = 1;
                goto exit;
        }

        /*
         * This line could be a continuation of the previously matched header
         * field. If this is the case then we should append this value to the
         * end of the previously consumed value.
         */
        if (http_auth.header_is_last_match && is_hdr_continuation(ptr, size)) {
                /*
                 * Trim the CRLF and any leading or trailing from this line.
                 */
                strbuf_add(&buf, ptr, size);
                strbuf_trim(&buf);

                /*
                 * At this point we should always have at least one existing
                 * value, even if it is empty. Do not bother appending the new
                 * value if this continuation header is itself empty.
                 */
                if (!values->nr) {
                        BUG("should have at least one existing header value");
                } else if (buf.len) {
                        char *prev = xstrdup(values->v[values->nr - 1]);

                        /* Join two non-empty values with a single space. */
                        const char *const sp = *prev ? " " : "";

                        strvec_pop(values);
                        strvec_pushf(values, "%s%s%s", prev, sp, buf.buf);
                        free(prev);
                }

                goto exit;
        }

        /* Not a continuation of a previously matched auth header line. */
        http_auth.header_is_last_match = 0;

        /*
         * If this is a HTTP status line and not a header field, this signals
         * a different HTTP response. libcurl writes all the output of all
         * response headers of all responses, including redirects.
         * We only care about the last HTTP request response's headers so clear
         * the existing array.
         */
        if (skip_iprefix_mem(ptr, size, "http/", &val, &val_len))
                strvec_clear(values);

exit:
        strbuf_release(&buf);
        return size;
}

size_t fwrite_null(char *ptr UNUSED, size_t eltsize UNUSED, size_t nmemb,
                   void *data UNUSED)
{
        return nmemb;
}

static void closedown_active_slot(struct active_request_slot *slot)
{
        active_requests--;
        slot->in_use = 0;
}

static void finish_active_slot(struct active_request_slot *slot)
{
        closedown_active_slot(slot);
        curl_easy_getinfo(slot->curl, CURLINFO_HTTP_CODE, &slot->http_code);

        if (slot->finished)
                (*slot->finished) = 1;

        /* Store slot results so they can be read after the slot is reused */
        if (slot->results) {
                slot->results->curl_result = slot->curl_result;
                slot->results->http_code = slot->http_code;
                curl_easy_getinfo(slot->curl, CURLINFO_HTTPAUTH_AVAIL,
                                  &slot->results->auth_avail);

                curl_easy_getinfo(slot->curl, CURLINFO_HTTP_CONNECTCODE,
                        &slot->results->http_connectcode);
        }

        /* Run callback if appropriate */
        if (slot->callback_func)
                slot->callback_func(slot->callback_data);
}

static void xmulti_remove_handle(struct active_request_slot *slot)
{
        curl_multi_remove_handle(curlm, slot->curl);
}

static void process_curl_messages(void)
{
        int num_messages;
        struct active_request_slot *slot;
        CURLMsg *curl_message = curl_multi_info_read(curlm, &num_messages);

        while (curl_message != NULL) {
                if (curl_message->msg == CURLMSG_DONE) {
                        int curl_result = curl_message->data.result;
                        slot = active_queue_head;
                        while (slot != NULL &&
                               slot->curl != curl_message->easy_handle)
                                slot = slot->next;
                        if (slot) {
                                xmulti_remove_handle(slot);
                                slot->curl_result = curl_result;
                                finish_active_slot(slot);
                        } else {
                                fprintf(stderr, "Received DONE message for unknown request!\n");
                        }
                } else {
                        fprintf(stderr, "Unknown CURL message received: %d\n",
                                (int)curl_message->msg);
                }
                curl_message = curl_multi_info_read(curlm, &num_messages);
        }
}

static int http_options(const char *var, const char *value,
                        const struct config_context *ctx, void *data)
{
        if (!strcmp("http.version", var)) {
                return git_config_string(&curl_http_version, var, value);
        }
        if (!strcmp("http.sslverify", var)) {
                curl_ssl_verify = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.sslcipherlist", var))
                return git_config_string(&ssl_cipherlist, var, value);
        if (!strcmp("http.sslversion", var))
                return git_config_string(&ssl_version, var, value);
        if (!strcmp("http.sslcert", var))
                return git_config_pathname(&ssl_cert, var, value);
        if (!strcmp("http.sslcerttype", var))
                return git_config_string(&ssl_cert_type, var, value);
        if (!strcmp("http.sslkey", var))
                return git_config_pathname(&ssl_key, var, value);
        if (!strcmp("http.sslkeytype", var))
                return git_config_string(&ssl_key_type, var, value);
        if (!strcmp("http.sslcapath", var))
                return git_config_pathname(&ssl_capath, var, value);
        if (!strcmp("http.sslcainfo", var))
                return git_config_pathname(&ssl_cainfo, var, value);
        if (!strcmp("http.sslcertpasswordprotected", var)) {
                ssl_cert_password_required = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.ssltry", var)) {
                curl_ssl_try = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.sslbackend", var)) {
                free(http_ssl_backend);
                http_ssl_backend = xstrdup_or_null(value);
                return 0;
        }

        if (!strcmp("http.schannelcheckrevoke", var)) {
                http_schannel_check_revoke = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp("http.schannelusesslcainfo", var)) {
                http_schannel_use_ssl_cainfo = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp("http.minsessions", var)) {
                min_curl_sessions = git_config_int(var, value, ctx->kvi);
                if (min_curl_sessions > 1)
                        min_curl_sessions = 1;
                return 0;
        }
        if (!strcmp("http.maxrequests", var)) {
                max_requests = git_config_int(var, value, ctx->kvi);
                return 0;
        }
        if (!strcmp("http.lowspeedlimit", var)) {
                curl_low_speed_limit = (long)git_config_int(var, value, ctx->kvi);
                return 0;
        }
        if (!strcmp("http.lowspeedtime", var)) {
                curl_low_speed_time = (long)git_config_int(var, value, ctx->kvi);
                return 0;
        }

        if (!strcmp("http.noepsv", var)) {
                curl_ftp_no_epsv = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.proxy", var))
                return git_config_string(&curl_http_proxy, var, value);

        if (!strcmp("http.proxyauthmethod", var))
                return git_config_string(&http_proxy_authmethod, var, value);

        if (!strcmp("http.proxysslcert", var))
                return git_config_string(&http_proxy_ssl_cert, var, value);

        if (!strcmp("http.proxysslkey", var))
                return git_config_string(&http_proxy_ssl_key, var, value);

        if (!strcmp("http.proxysslcainfo", var))
                return git_config_string(&http_proxy_ssl_ca_info, var, value);

        if (!strcmp("http.proxysslcertpasswordprotected", var)) {
                proxy_ssl_cert_password_required = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp("http.cookiefile", var))
                return git_config_pathname(&curl_cookie_file, var, value);
        if (!strcmp("http.savecookies", var)) {
                curl_save_cookies = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp("http.postbuffer", var)) {
                http_post_buffer = git_config_ssize_t(var, value, ctx->kvi);
                if (http_post_buffer < 0)
                        warning(_("negative value for http.postBuffer; defaulting to %d"), LARGE_PACKET_MAX);
                if (http_post_buffer < LARGE_PACKET_MAX)
                        http_post_buffer = LARGE_PACKET_MAX;
                return 0;
        }

        if (!strcmp("http.useragent", var))
                return git_config_string(&user_agent, var, value);

        if (!strcmp("http.emptyauth", var)) {
                if (value && !strcmp("auto", value))
                        curl_empty_auth = -1;
                else
                        curl_empty_auth = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp("http.delegation", var)) {
#ifdef CURLGSSAPI_DELEGATION_FLAG
                return git_config_string(&curl_deleg, var, value);
#else
                warning(_("Delegation control is not supported with cURL < 7.22.0"));
                return 0;
#endif
        }

        if (!strcmp("http.pinnedpubkey", var)) {
#ifdef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
                return git_config_pathname(&ssl_pinnedkey, var, value);
#else
                warning(_("Public key pinning not supported with cURL < 7.39.0"));
                return 0;
#endif
        }

        if (!strcmp("http.extraheader", var)) {
                if (!value) {
                        return config_error_nonbool(var);
                } else if (!*value) {
                        string_list_clear(&extra_http_headers, 0);
                } else {
                        string_list_append(&extra_http_headers, value);
                }
                return 0;
        }

        if (!strcmp("http.curloptresolve", var)) {
                if (!value) {
                        return config_error_nonbool(var);
                } else if (!*value) {
                        curl_slist_free_all(host_resolutions);
                        host_resolutions = NULL;
                } else {
                        host_resolutions = curl_slist_append(host_resolutions, value);
                }
                return 0;
        }

        if (!strcmp("http.followredirects", var)) {
                if (value && !strcmp(value, "initial"))
                        http_follow_config = HTTP_FOLLOW_INITIAL;
                else if (git_config_bool(var, value))
                        http_follow_config = HTTP_FOLLOW_ALWAYS;
                else
                        http_follow_config = HTTP_FOLLOW_NONE;
                return 0;
        }

        /* Fall back on the default ones */
        return git_default_config(var, value, ctx, data);
}

static int curl_empty_auth_enabled(void)
{
        if (curl_empty_auth >= 0)
                return curl_empty_auth;

        /*
         * In the automatic case, kick in the empty-auth
         * hack as long as we would potentially try some
         * method more exotic than "Basic" or "Digest".
         *
         * But only do this when this is our second or
         * subsequent request, as by then we know what
         * methods are available.
         */
        if (http_auth_methods_restricted &&
            (http_auth_methods & ~empty_auth_useless))
                return 1;
        return 0;
}

static void init_curl_http_auth(CURL *result)
{
        if (!http_auth.username || !*http_auth.username) {
                if (curl_empty_auth_enabled())
                        curl_easy_setopt(result, CURLOPT_USERPWD, ":");
                return;
        }

        credential_fill(&http_auth);

        curl_easy_setopt(result, CURLOPT_USERNAME, http_auth.username);
        curl_easy_setopt(result, CURLOPT_PASSWORD, http_auth.password);
}

/* *var must be free-able */
static void var_override(const char **var, char *value)
{
        if (value) {
                free((void *)*var);
                *var = xstrdup(value);
        }
}

static void set_proxyauth_name_password(CURL *result)
{
                curl_easy_setopt(result, CURLOPT_PROXYUSERNAME,
                        proxy_auth.username);
                curl_easy_setopt(result, CURLOPT_PROXYPASSWORD,
                        proxy_auth.password);
}

static void init_curl_proxy_auth(CURL *result)
{
        if (proxy_auth.username) {
                if (!proxy_auth.password)
                        credential_fill(&proxy_auth);
                set_proxyauth_name_password(result);
        }

        var_override(&http_proxy_authmethod, getenv("GIT_HTTP_PROXY_AUTHMETHOD"));

        if (http_proxy_authmethod) {
                int i;
                for (i = 0; i < ARRAY_SIZE(proxy_authmethods); i++) {
                        if (!strcmp(http_proxy_authmethod, proxy_authmethods[i].name)) {
                                curl_easy_setopt(result, CURLOPT_PROXYAUTH,
                                                proxy_authmethods[i].curlauth_param);
                                break;
                        }
                }
                if (i == ARRAY_SIZE(proxy_authmethods)) {
                        warning("unsupported proxy authentication method %s: using anyauth",
                                        http_proxy_authmethod);
                        curl_easy_setopt(result, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
                }
        }
        else
                curl_easy_setopt(result, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
}

static int has_cert_password(void)
{
        if (ssl_cert == NULL || ssl_cert_password_required != 1)
                return 0;
        if (!cert_auth.password) {
                cert_auth.protocol = xstrdup("cert");
                cert_auth.host = xstrdup("");
                cert_auth.username = xstrdup("");
                cert_auth.path = xstrdup(ssl_cert);
                credential_fill(&cert_auth);
        }
        return 1;
}

#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD
static int has_proxy_cert_password(void)
{
        if (http_proxy_ssl_cert == NULL || proxy_ssl_cert_password_required != 1)
                return 0;
        if (!proxy_cert_auth.password) {
                proxy_cert_auth.protocol = xstrdup("cert");
                proxy_cert_auth.host = xstrdup("");
                proxy_cert_auth.username = xstrdup("");
                proxy_cert_auth.path = xstrdup(http_proxy_ssl_cert);
                credential_fill(&proxy_cert_auth);
        }
        return 1;
}
#endif

#ifdef GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE
static void set_curl_keepalive(CURL *c)
{
        curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);
}

#else
static int sockopt_callback(void *client, curl_socket_t fd, curlsocktype type)
{
        int ka = 1;
        int rc;
        socklen_t len = (socklen_t)sizeof(ka);

        if (type != CURLSOCKTYPE_IPCXN)
                return 0;

        rc = setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&ka, len);
        if (rc < 0)
                warning_errno("unable to set SO_KEEPALIVE on socket");

        return CURL_SOCKOPT_OK;
}

static void set_curl_keepalive(CURL *c)
{
        curl_easy_setopt(c, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
}
#endif

/* Return 1 if redactions have been made, 0 otherwise. */
static int redact_sensitive_header(struct strbuf *header, size_t offset)
{
        int ret = 0;
        const char *sensitive_header;

        if (trace_curl_redact &&
            (skip_iprefix(header->buf + offset, "Authorization:", &sensitive_header) ||
             skip_iprefix(header->buf + offset, "Proxy-Authorization:", &sensitive_header))) {
                /* The first token is the type, which is OK to log */
                while (isspace(*sensitive_header))
                        sensitive_header++;
                while (*sensitive_header && !isspace(*sensitive_header))
                        sensitive_header++;
                /* Everything else is opaque and possibly sensitive */
                strbuf_setlen(header,  sensitive_header - header->buf);
                strbuf_addstr(header, " <redacted>");
                ret = 1;
        } else if (trace_curl_redact &&
                   skip_iprefix(header->buf + offset, "Cookie:", &sensitive_header)) {
                struct strbuf redacted_header = STRBUF_INIT;
                const char *cookie;

                while (isspace(*sensitive_header))
                        sensitive_header++;

                cookie = sensitive_header;

                while (cookie) {
                        char *equals;
                        char *semicolon = strstr(cookie, "; ");
                        if (semicolon)
                                *semicolon = 0;
                        equals = strchrnul(cookie, '=');
                        if (!equals) {
                                /* invalid cookie, just append and continue */
                                strbuf_addstr(&redacted_header, cookie);
                                continue;
                        }
                        strbuf_add(&redacted_header, cookie, equals - cookie);
                        strbuf_addstr(&redacted_header, "=<redacted>");
                        if (semicolon) {
                                /*
                                 * There are more cookies. (Or, for some
                                 * reason, the input string ends in "; ".)
                                 */
                                strbuf_addstr(&redacted_header, "; ");
                                cookie = semicolon + strlen("; ");
                        } else {
                                cookie = NULL;
                        }
                }

                strbuf_setlen(header, sensitive_header - header->buf);
                strbuf_addbuf(header, &redacted_header);
                ret = 1;
        }
        return ret;
}

static int match_curl_h2_trace(const char *line, const char **out)
{
        const char *p;

        /*
         * curl prior to 8.1.0 gives us:
         *
         *     h2h3 [<header-name>: <header-val>]
         *
         * Starting in 8.1.0, the first token became just "h2".
         */
        if (skip_iprefix(line, "h2h3 [", out) ||
            skip_iprefix(line, "h2 [", out))
                return 1;

        /*
         * curl 8.3.0 uses:
         *   [HTTP/2] [<stream-id>] [<header-name>: <header-val>]
         * where <stream-id> is numeric.
         */
        if (skip_iprefix(line, "[HTTP/2] [", &p)) {
                while (isdigit(*p))
                        p++;
                if (skip_prefix(p, "] [", out))
                        return 1;
        }

        return 0;
}

/* Redact headers in info */
static void redact_sensitive_info_header(struct strbuf *header)
{
        const char *sensitive_header;

        if (trace_curl_redact &&
            match_curl_h2_trace(header->buf, &sensitive_header)) {
                if (redact_sensitive_header(header, sensitive_header - header->buf)) {
                        /* redaction ate our closing bracket */
                        strbuf_addch(header, ']');
                }
        }
}

static void curl_dump_header(const char *text, unsigned char *ptr, size_t size, int hide_sensitive_header)
{
        struct strbuf out = STRBUF_INIT;
        struct strbuf **headers, **header;

        strbuf_addf(&out, "%s, %10.10ld bytes (0x%8.8lx)\n",
                text, (long)size, (long)size);
        trace_strbuf(&trace_curl, &out);
        strbuf_reset(&out);
        strbuf_add(&out, ptr, size);
        headers = strbuf_split_max(&out, '\n', 0);

        for (header = headers; *header; header++) {
                if (hide_sensitive_header)
                        redact_sensitive_header(*header, 0);
                strbuf_insertstr((*header), 0, text);
                strbuf_insertstr((*header), strlen(text), ": ");
                strbuf_rtrim((*header));
                strbuf_addch((*header), '\n');
                trace_strbuf(&trace_curl, (*header));
        }
        strbuf_list_free(headers);
        strbuf_release(&out);
}

static void curl_dump_data(const char *text, unsigned char *ptr, size_t size)
{
        size_t i;
        struct strbuf out = STRBUF_INIT;
        unsigned int width = 60;

        strbuf_addf(&out, "%s, %10.10ld bytes (0x%8.8lx)\n",
                text, (long)size, (long)size);
        trace_strbuf(&trace_curl, &out);

        for (i = 0; i < size; i += width) {
                size_t w;

                strbuf_reset(&out);
                strbuf_addf(&out, "%s: ", text);
                for (w = 0; (w < width) && (i + w < size); w++) {
                        unsigned char ch = ptr[i + w];

                        strbuf_addch(&out,
                                       (ch >= 0x20) && (ch < 0x80)
                                       ? ch : '.');
                }
                strbuf_addch(&out, '\n');
                trace_strbuf(&trace_curl, &out);
        }
        strbuf_release(&out);
}

static void curl_dump_info(char *data, size_t size)
{
        struct strbuf buf = STRBUF_INIT;

        strbuf_add(&buf, data, size);

        redact_sensitive_info_header(&buf);
        trace_printf_key(&trace_curl, "== Info: %s", buf.buf);

        strbuf_release(&buf);
}

static int curl_trace(CURL *handle UNUSED, curl_infotype type,
                      char *data, size_t size,
                      void *userp UNUSED)
{
        const char *text;
        enum { NO_FILTER = 0, DO_FILTER = 1 };

        switch (type) {
        case CURLINFO_TEXT:
                curl_dump_info(data, size);
                break;
        case CURLINFO_HEADER_OUT:
                text = "=> Send header";
                curl_dump_header(text, (unsigned char *)data, size, DO_FILTER);
                break;
        case CURLINFO_DATA_OUT:
                if (trace_curl_data) {
                        text = "=> Send data";
                        curl_dump_data(text, (unsigned char *)data, size);
                }
                break;
        case CURLINFO_SSL_DATA_OUT:
                if (trace_curl_data) {
                        text = "=> Send SSL data";
                        curl_dump_data(text, (unsigned char *)data, size);
                }
                break;
        case CURLINFO_HEADER_IN:
                text = "<= Recv header";
                curl_dump_header(text, (unsigned char *)data, size, NO_FILTER);
                break;
        case CURLINFO_DATA_IN:
                if (trace_curl_data) {
                        text = "<= Recv data";
                        curl_dump_data(text, (unsigned char *)data, size);
                }
                break;
        case CURLINFO_SSL_DATA_IN:
                if (trace_curl_data) {
                        text = "<= Recv SSL data";
                        curl_dump_data(text, (unsigned char *)data, size);
                }
                break;

        default:                /* we ignore unknown types by default */
                return 0;
        }
        return 0;
}

void http_trace_curl_no_data(void)
{
        trace_override_envvar(&trace_curl, "1");
        trace_curl_data = 0;
}

void setup_curl_trace(CURL *handle)
{
        if (!trace_want(&trace_curl))
                return;
        curl_easy_setopt(handle, CURLOPT_VERBOSE, 1L);
        curl_easy_setopt(handle, CURLOPT_DEBUGFUNCTION, curl_trace);
        curl_easy_setopt(handle, CURLOPT_DEBUGDATA, NULL);
}

static void proto_list_append(struct strbuf *list, const char *proto)
{
        if (!list)
                return;
        if (list->len)
                strbuf_addch(list, ',');
        strbuf_addstr(list, proto);
}

static long get_curl_allowed_protocols(int from_user, struct strbuf *list)
{
        long bits = 0;

        if (is_transport_allowed("http", from_user)) {
                bits |= CURLPROTO_HTTP;
                proto_list_append(list, "http");
        }
        if (is_transport_allowed("https", from_user)) {
                bits |= CURLPROTO_HTTPS;
                proto_list_append(list, "https");
        }
        if (is_transport_allowed("ftp", from_user)) {
                bits |= CURLPROTO_FTP;
                proto_list_append(list, "ftp");
        }
        if (is_transport_allowed("ftps", from_user)) {
                bits |= CURLPROTO_FTPS;
                proto_list_append(list, "ftps");
        }

        return bits;
}

#ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
static int get_curl_http_version_opt(const char *version_string, long *opt)
{
        int i;
        static struct {
                const char *name;
                long opt_token;
        } choice[] = {
                { "HTTP/1.1", CURL_HTTP_VERSION_1_1 },
                { "HTTP/2", CURL_HTTP_VERSION_2 }
        };

        for (i = 0; i < ARRAY_SIZE(choice); i++) {
                if (!strcmp(version_string, choice[i].name)) {
                        *opt = choice[i].opt_token;
                        return 0;
                }
        }

        warning("unknown value given to http.version: '%s'", version_string);
        return -1; /* not found */
}

#endif

static CURL *get_curl_handle(void)
{
        CURL *result = curl_easy_init();

        if (!result)
                die("curl_easy_init failed");

        if (!curl_ssl_verify) {
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYPEER, 0);
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYHOST, 0);
        } else {
                /* Verify authenticity of the peer's certificate */
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYPEER, 1);
                /* The name in the cert must match whom we tried to connect */
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYHOST, 2);
        }

#ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
    if (curl_http_version) {
                long opt;
                if (!get_curl_http_version_opt(curl_http_version, &opt)) {
                        /* Set request use http version */
                        curl_easy_setopt(result, CURLOPT_HTTP_VERSION, opt);
                }
    }
#endif

        curl_easy_setopt(result, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
        curl_easy_setopt(result, CURLOPT_HTTPAUTH, CURLAUTH_ANY);

#ifdef CURLGSSAPI_DELEGATION_FLAG
        if (curl_deleg) {
                int i;
                for (i = 0; i < ARRAY_SIZE(curl_deleg_levels); i++) {
                        if (!strcmp(curl_deleg, curl_deleg_levels[i].name)) {
                                curl_easy_setopt(result, CURLOPT_GSSAPI_DELEGATION,
                                                curl_deleg_levels[i].curl_deleg_param);
                                break;
                        }
                }
                if (i == ARRAY_SIZE(curl_deleg_levels))
                        warning("Unknown delegation method '%s': using default",
                                curl_deleg);
        }
#endif

        if (http_ssl_backend && !strcmp("schannel", http_ssl_backend) &&
            !http_schannel_check_revoke) {
#ifdef GIT_CURL_HAVE_CURLSSLOPT_NO_REVOKE
                curl_easy_setopt(result, CURLOPT_SSL_OPTIONS, CURLSSLOPT_NO_REVOKE);
#else
                warning(_("CURLSSLOPT_NO_REVOKE not supported with cURL < 7.44.0"));
#endif
        }

        if (http_proactive_auth)
                init_curl_http_auth(result);

        if (getenv("GIT_SSL_VERSION"))
                ssl_version = getenv("GIT_SSL_VERSION");
        if (ssl_version && *ssl_version) {
                int i;
                for (i = 0; i < ARRAY_SIZE(sslversions); i++) {
                        if (!strcmp(ssl_version, sslversions[i].name)) {
                                curl_easy_setopt(result, CURLOPT_SSLVERSION,
                                                 sslversions[i].ssl_version);
                                break;
                        }
                }
                if (i == ARRAY_SIZE(sslversions))
                        warning("unsupported ssl version %s: using default",
                                ssl_version);
        }

        if (getenv("GIT_SSL_CIPHER_LIST"))
                ssl_cipherlist = getenv("GIT_SSL_CIPHER_LIST");
        if (ssl_cipherlist != NULL && *ssl_cipherlist)
                curl_easy_setopt(result, CURLOPT_SSL_CIPHER_LIST,
                                ssl_cipherlist);

        if (ssl_cert)
                curl_easy_setopt(result, CURLOPT_SSLCERT, ssl_cert);
        if (ssl_cert_type)
                curl_easy_setopt(result, CURLOPT_SSLCERTTYPE, ssl_cert_type);
        if (has_cert_password())
                curl_easy_setopt(result, CURLOPT_KEYPASSWD, cert_auth.password);
        if (ssl_key)
                curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);
        if (ssl_key_type)
                curl_easy_setopt(result, CURLOPT_SSLKEYTYPE, ssl_key_type);
        if (ssl_capath)
                curl_easy_setopt(result, CURLOPT_CAPATH, ssl_capath);
#ifdef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
        if (ssl_pinnedkey)
                curl_easy_setopt(result, CURLOPT_PINNEDPUBLICKEY, ssl_pinnedkey);
#endif
        if (http_ssl_backend && !strcmp("schannel", http_ssl_backend) &&
            !http_schannel_use_ssl_cainfo) {
                curl_easy_setopt(result, CURLOPT_CAINFO, NULL);
#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO
                curl_easy_setopt(result, CURLOPT_PROXY_CAINFO, NULL);
#endif
        } else if (ssl_cainfo != NULL || http_proxy_ssl_ca_info != NULL) {
                if (ssl_cainfo)
                        curl_easy_setopt(result, CURLOPT_CAINFO, ssl_cainfo);
#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO
                if (http_proxy_ssl_ca_info)
                        curl_easy_setopt(result, CURLOPT_PROXY_CAINFO, http_proxy_ssl_ca_info);
#endif
        }

        if (curl_low_speed_limit > 0 && curl_low_speed_time > 0) {
                curl_easy_setopt(result, CURLOPT_LOW_SPEED_LIMIT,
                                 curl_low_speed_limit);
                curl_easy_setopt(result, CURLOPT_LOW_SPEED_TIME,
                                 curl_low_speed_time);
        }

        curl_easy_setopt(result, CURLOPT_MAXREDIRS, 20);
        curl_easy_setopt(result, CURLOPT_POSTREDIR, CURL_REDIR_POST_ALL);

#ifdef GIT_CURL_HAVE_CURLOPT_PROTOCOLS_STR
        {
                struct strbuf buf = STRBUF_INIT;

                get_curl_allowed_protocols(0, &buf);
                curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS_STR, buf.buf);
                strbuf_reset(&buf);

                get_curl_allowed_protocols(-1, &buf);
                curl_easy_setopt(result, CURLOPT_PROTOCOLS_STR, buf.buf);
                strbuf_release(&buf);
        }
#else
        curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS,
                         get_curl_allowed_protocols(0, NULL));
        curl_easy_setopt(result, CURLOPT_PROTOCOLS,
                         get_curl_allowed_protocols(-1, NULL));
#endif

        if (getenv("GIT_CURL_VERBOSE"))
                http_trace_curl_no_data();
        setup_curl_trace(result);
        if (getenv("GIT_TRACE_CURL_NO_DATA"))
                trace_curl_data = 0;
        if (!git_env_bool("GIT_TRACE_REDACT", 1))
                trace_curl_redact = 0;

        curl_easy_setopt(result, CURLOPT_USERAGENT,
                user_agent ? user_agent : git_user_agent());

        if (curl_ftp_no_epsv)
                curl_easy_setopt(result, CURLOPT_FTP_USE_EPSV, 0);

        if (curl_ssl_try)
                curl_easy_setopt(result, CURLOPT_USE_SSL, CURLUSESSL_TRY);

        /*
         * CURL also examines these variables as a fallback; but we need to query
         * them here in order to decide whether to prompt for missing password (cf.
         * init_curl_proxy_auth()).
         *
         * Unlike many other common environment variables, these are historically
         * lowercase only. It appears that CURL did not know this and implemented
         * only uppercase variants, which was later corrected to take both - with
         * the exception of http_proxy, which is lowercase only also in CURL. As
         * the lowercase versions are the historical quasi-standard, they take
         * precedence here, as in CURL.
         */
        if (!curl_http_proxy) {
                if (http_auth.protocol && !strcmp(http_auth.protocol, "https")) {
                        var_override(&curl_http_proxy, getenv("HTTPS_PROXY"));
                        var_override(&curl_http_proxy, getenv("https_proxy"));
                } else {
                        var_override(&curl_http_proxy, getenv("http_proxy"));
                }
                if (!curl_http_proxy) {
                        var_override(&curl_http_proxy, getenv("ALL_PROXY"));
                        var_override(&curl_http_proxy, getenv("all_proxy"));
                }
        }

        if (curl_http_proxy && curl_http_proxy[0] == '\0') {
                /*
                 * Handle case with the empty http.proxy value here to keep
                 * common code clean.
                 * NB: empty option disables proxying at all.
                 */
                curl_easy_setopt(result, CURLOPT_PROXY, "");
        } else if (curl_http_proxy) {
                if (starts_with(curl_http_proxy, "socks5h"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS5_HOSTNAME);
                else if (starts_with(curl_http_proxy, "socks5"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS5);
                else if (starts_with(curl_http_proxy, "socks4a"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS4A);
                else if (starts_with(curl_http_proxy, "socks"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS4);
#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD
                else if (starts_with(curl_http_proxy, "https")) {
                        curl_easy_setopt(result, CURLOPT_PROXYTYPE, CURLPROXY_HTTPS);

                        if (http_proxy_ssl_cert)
                                curl_easy_setopt(result, CURLOPT_PROXY_SSLCERT, http_proxy_ssl_cert);

                        if (http_proxy_ssl_key)
                                curl_easy_setopt(result, CURLOPT_PROXY_SSLKEY, http_proxy_ssl_key);

                        if (has_proxy_cert_password())
                                curl_easy_setopt(result, CURLOPT_PROXY_KEYPASSWD, proxy_cert_auth.password);
                }
#endif
                if (strstr(curl_http_proxy, "://"))
                        credential_from_url(&proxy_auth, curl_http_proxy);
                else {
                        struct strbuf url = STRBUF_INIT;
                        strbuf_addf(&url, "http://%s", curl_http_proxy);
                        credential_from_url(&proxy_auth, url.buf);
                        strbuf_release(&url);
                }

                if (!proxy_auth.host)
                        die("Invalid proxy URL '%s'", curl_http_proxy);

                curl_easy_setopt(result, CURLOPT_PROXY, proxy_auth.host);
                var_override(&curl_no_proxy, getenv("NO_PROXY"));
                var_override(&curl_no_proxy, getenv("no_proxy"));
                curl_easy_setopt(result, CURLOPT_NOPROXY, curl_no_proxy);
        }
        init_curl_proxy_auth(result);

        set_curl_keepalive(result);

        return result;
}

static void set_from_env(const char **var, const char *envname)
{
        const char *val = getenv(envname);
        if (val)
                *var = val;
}

void http_init(struct remote *remote, const char *url, int proactive_auth)
{
        char *low_speed_limit;
        char *low_speed_time;
        char *normalized_url;
        struct urlmatch_config config = URLMATCH_CONFIG_INIT;

        config.section = "http";
        config.key = NULL;
        config.collect_fn = http_options;
        config.cascade_fn = git_default_config;
        config.cb = NULL;

        http_is_verbose = 0;
        normalized_url = url_normalize(url, &config.url);

        git_config(urlmatch_config_entry, &config);
        free(normalized_url);
        string_list_clear(&config.vars, 1);

#ifdef GIT_CURL_HAVE_CURLSSLSET_NO_BACKENDS
        if (http_ssl_backend) {
                const curl_ssl_backend **backends;
                struct strbuf buf = STRBUF_INIT;
                int i;

                switch (curl_global_sslset(-1, http_ssl_backend, &backends)) {
                case CURLSSLSET_UNKNOWN_BACKEND:
                        strbuf_addf(&buf, _("Unsupported SSL backend '%s'. "
                                            "Supported SSL backends:"),
                                            http_ssl_backend);
                        for (i = 0; backends[i]; i++)
                                strbuf_addf(&buf, "\n\t%s", backends[i]->name);
                        die("%s", buf.buf);
                case CURLSSLSET_NO_BACKENDS:
                        die(_("Could not set SSL backend to '%s': "
                              "cURL was built without SSL backends"),
                            http_ssl_backend);
                case CURLSSLSET_TOO_LATE:
                        die(_("Could not set SSL backend to '%s': already set"),
                            http_ssl_backend);
                case CURLSSLSET_OK:
                        break; /* Okay! */
                }
        }
#endif

        if (curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK)
                die("curl_global_init failed");

        http_proactive_auth = proactive_auth;

        if (remote && remote->http_proxy)
                curl_http_proxy = xstrdup(remote->http_proxy);

        if (remote)
                var_override(&http_proxy_authmethod, remote->http_proxy_authmethod);

        pragma_header = curl_slist_append(http_copy_default_headers(),
                "Pragma: no-cache");
        no_pragma_header = curl_slist_append(http_copy_default_headers(),
                "Pragma:");

        {
                char *http_max_requests = getenv("GIT_HTTP_MAX_REQUESTS");
                if (http_max_requests)
                        max_requests = atoi(http_max_requests);
        }

        curlm = curl_multi_init();
        if (!curlm)
                die("curl_multi_init failed");

        if (getenv("GIT_SSL_NO_VERIFY"))
                curl_ssl_verify = 0;

        set_from_env(&ssl_cert, "GIT_SSL_CERT");
        set_from_env(&ssl_cert_type, "GIT_SSL_CERT_TYPE");
        set_from_env(&ssl_key, "GIT_SSL_KEY");
        set_from_env(&ssl_key_type, "GIT_SSL_KEY_TYPE");
        set_from_env(&ssl_capath, "GIT_SSL_CAPATH");
        set_from_env(&ssl_cainfo, "GIT_SSL_CAINFO");

        set_from_env(&user_agent, "GIT_HTTP_USER_AGENT");

        low_speed_limit = getenv("GIT_HTTP_LOW_SPEED_LIMIT");
        if (low_speed_limit)
                curl_low_speed_limit = strtol(low_speed_limit, NULL, 10);
        low_speed_time = getenv("GIT_HTTP_LOW_SPEED_TIME");
        if (low_speed_time)
                curl_low_speed_time = strtol(low_speed_time, NULL, 10);

        if (curl_ssl_verify == -1)
                curl_ssl_verify = 1;

        curl_session_count = 0;
        if (max_requests < 1)
                max_requests = DEFAULT_MAX_REQUESTS;

        set_from_env(&http_proxy_ssl_cert, "GIT_PROXY_SSL_CERT");
        set_from_env(&http_proxy_ssl_key, "GIT_PROXY_SSL_KEY");
        set_from_env(&http_proxy_ssl_ca_info, "GIT_PROXY_SSL_CAINFO");

        if (getenv("GIT_PROXY_SSL_CERT_PASSWORD_PROTECTED"))
                proxy_ssl_cert_password_required = 1;

        if (getenv("GIT_CURL_FTP_NO_EPSV"))
                curl_ftp_no_epsv = 1;

        if (url) {
                credential_from_url(&http_auth, url);
                if (!ssl_cert_password_required &&
                    getenv("GIT_SSL_CERT_PASSWORD_PROTECTED") &&
                    starts_with(url, "https://"))
                        ssl_cert_password_required = 1;
        }

        curl_default = get_curl_handle();
}

void http_cleanup(void)
{
        struct active_request_slot *slot = active_queue_head;

        while (slot != NULL) {
                struct active_request_slot *next = slot->next;
                if (slot->curl) {
                        xmulti_remove_handle(slot);
                        curl_easy_cleanup(slot->curl);
                }
                free(slot);
                slot = next;
        }
        active_queue_head = NULL;

        curl_easy_cleanup(curl_default);

        curl_multi_cleanup(curlm);
        curl_global_cleanup();

        string_list_clear(&extra_http_headers, 0);

        curl_slist_free_all(pragma_header);
        pragma_header = NULL;

        curl_slist_free_all(no_pragma_header);
        no_pragma_header = NULL;

        curl_slist_free_all(host_resolutions);
        host_resolutions = NULL;

        if (curl_http_proxy) {
                free((void *)curl_http_proxy);
                curl_http_proxy = NULL;
        }

        if (proxy_auth.password) {
                memset(proxy_auth.password, 0, strlen(proxy_auth.password));
                FREE_AND_NULL(proxy_auth.password);
        }

        free((void *)curl_proxyuserpwd);
        curl_proxyuserpwd = NULL;

        free((void *)http_proxy_authmethod);
        http_proxy_authmethod = NULL;

        if (cert_auth.password) {
                memset(cert_auth.password, 0, strlen(cert_auth.password));
                FREE_AND_NULL(cert_auth.password);
        }
        ssl_cert_password_required = 0;

        if (proxy_cert_auth.password) {
                memset(proxy_cert_auth.password, 0, strlen(proxy_cert_auth.password));
                FREE_AND_NULL(proxy_cert_auth.password);
        }
        proxy_ssl_cert_password_required = 0;

        FREE_AND_NULL(cached_accept_language);
}

struct active_request_slot *get_active_slot(void)
{
        struct active_request_slot *slot = active_queue_head;
        struct active_request_slot *newslot;

        int num_transfers;

        /* Wait for a slot to open up if the queue is full */
        while (active_requests >= max_requests) {
                curl_multi_perform(curlm, &num_transfers);
                if (num_transfers < active_requests)
                        process_curl_messages();
        }

        while (slot != NULL && slot->in_use)
                slot = slot->next;

        if (!slot) {
                newslot = xmalloc(sizeof(*newslot));
                newslot->curl = NULL;
                newslot->in_use = 0;
                newslot->next = NULL;

                slot = active_queue_head;
                if (!slot) {
                        active_queue_head = newslot;
                } else {
                        while (slot->next != NULL)
                                slot = slot->next;
                        slot->next = newslot;
                }
                slot = newslot;
        }

        if (!slot->curl) {
                slot->curl = curl_easy_duphandle(curl_default);
                curl_session_count++;
        }

        active_requests++;
        slot->in_use = 1;
        slot->results = NULL;
        slot->finished = NULL;
        slot->callback_data = NULL;
        slot->callback_func = NULL;
        curl_easy_setopt(slot->curl, CURLOPT_COOKIEFILE, curl_cookie_file);
        if (curl_save_cookies)
                curl_easy_setopt(slot->curl, CURLOPT_COOKIEJAR, curl_cookie_file);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, pragma_header);
        curl_easy_setopt(slot->curl, CURLOPT_RESOLVE, host_resolutions);
        curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, curl_errorstr);
        curl_easy_setopt(slot->curl, CURLOPT_CUSTOMREQUEST, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDS, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_UPLOAD, 0);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);
        curl_easy_setopt(slot->curl, CURLOPT_FAILONERROR, 1);
        curl_easy_setopt(slot->curl, CURLOPT_RANGE, NULL);

        /*
         * Default following to off unless "ALWAYS" is configured; this gives
         * callers a sane starting point, and they can tweak for individual
         * HTTP_FOLLOW_* cases themselves.
         */
        if (http_follow_config == HTTP_FOLLOW_ALWAYS)
                curl_easy_setopt(slot->curl, CURLOPT_FOLLOWLOCATION, 1);
        else
                curl_easy_setopt(slot->curl, CURLOPT_FOLLOWLOCATION, 0);

        curl_easy_setopt(slot->curl, CURLOPT_IPRESOLVE, git_curl_ipresolve);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPAUTH, http_auth_methods);
        if (http_auth.password || curl_empty_auth_enabled())
                init_curl_http_auth(slot->curl);

        return slot;
}

int start_active_slot(struct active_request_slot *slot)
{
        CURLMcode curlm_result = curl_multi_add_handle(curlm, slot->curl);
        int num_transfers;

        if (curlm_result != CURLM_OK &&
            curlm_result != CURLM_CALL_MULTI_PERFORM) {
                warning("curl_multi_add_handle failed: %s",
                        curl_multi_strerror(curlm_result));
                active_requests--;
                slot->in_use = 0;
                return 0;
        }

        /*
         * We know there must be something to do, since we just added
         * something.
         */
        curl_multi_perform(curlm, &num_transfers);
        return 1;
}

struct fill_chain {
        void *data;
        int (*fill)(void *);
        struct fill_chain *next;
};

static struct fill_chain *fill_cfg;

void add_fill_function(void *data, int (*fill)(void *))
{
        struct fill_chain *new_fill = xmalloc(sizeof(*new_fill));
        struct fill_chain **linkp = &fill_cfg;
        new_fill->data = data;
        new_fill->fill = fill;
        new_fill->next = NULL;
        while (*linkp)
                linkp = &(*linkp)->next;
        *linkp = new_fill;
}

void fill_active_slots(void)
{
        struct active_request_slot *slot = active_queue_head;

        while (active_requests < max_requests) {
                struct fill_chain *fill;
                for (fill = fill_cfg; fill; fill = fill->next)
                        if (fill->fill(fill->data))
                                break;

                if (!fill)
                        break;
        }

        while (slot != NULL) {
                if (!slot->in_use && slot->curl != NULL
                        && curl_session_count > min_curl_sessions) {
                        curl_easy_cleanup(slot->curl);
                        slot->curl = NULL;
                        curl_session_count--;
                }
                slot = slot->next;
        }
}

void step_active_slots(void)
{
        int num_transfers;
        CURLMcode curlm_result;

        do {
                curlm_result = curl_multi_perform(curlm, &num_transfers);
        } while (curlm_result == CURLM_CALL_MULTI_PERFORM);
        if (num_transfers < active_requests) {
                process_curl_messages();
                fill_active_slots();
        }
}

void run_active_slot(struct active_request_slot *slot)
{
        fd_set readfds;
        fd_set writefds;
        fd_set excfds;
        int max_fd;
        struct timeval select_timeout;
        int finished = 0;

        slot->finished = &finished;
        while (!finished) {
                step_active_slots();

                if (slot->in_use) {
                        long curl_timeout;
                        curl_multi_timeout(curlm, &curl_timeout);
                        if (curl_timeout == 0) {
                                continue;
                        } else if (curl_timeout == -1) {
                                select_timeout.tv_sec  = 0;
                                select_timeout.tv_usec = 50000;
                        } else {
                                select_timeout.tv_sec  =  curl_timeout / 1000;
                                select_timeout.tv_usec = (curl_timeout % 1000) * 1000;
                        }

                        max_fd = -1;
                        FD_ZERO(&readfds);
                        FD_ZERO(&writefds);
                        FD_ZERO(&excfds);
                        curl_multi_fdset(curlm, &readfds, &writefds, &excfds, &max_fd);

                        /*
                         * It can happen that curl_multi_timeout returns a pathologically
                         * long timeout when curl_multi_fdset returns no file descriptors
                         * to read.  See commit message for more details.
                         */
                        if (max_fd < 0 &&
                            (select_timeout.tv_sec > 0 ||
                             select_timeout.tv_usec > 50000)) {
                                select_timeout.tv_sec  = 0;
                                select_timeout.tv_usec = 50000;
                        }

                        select(max_fd+1, &readfds, &writefds, &excfds, &select_timeout);
                }
        }

        /*
         * The value of slot->finished we set before the loop was used
         * to set our "finished" variable when our request completed.
         *
         * 1. The slot may not have been reused for another requst
         *    yet, in which case it still has &finished.
         *
         * 2. The slot may already be in-use to serve another request,
         *    which can further be divided into two cases:
         *
         * (a) If call run_active_slot() hasn't been called for that
         *     other request, slot->finished would have been cleared
         *     by get_active_slot() and has NULL.
         *
         * (b) If the request did call run_active_slot(), then the
         *     call would have updated slot->finished at the beginning
         *     of this function, and with the clearing of the member
         *     below, we would find that slot->finished is now NULL.
         *
         * In all cases, slot->finished has no useful information to
         * anybody at this point.  Some compilers warn us for
         * attempting to smuggle a pointer that is about to become
         * invalid, i.e. &finished.  We clear it here to assure them.
         */
        slot->finished = NULL;
}

static void release_active_slot(struct active_request_slot *slot)
{
        closedown_active_slot(slot);
        if (slot->curl) {
                xmulti_remove_handle(slot);
                if (curl_session_count > min_curl_sessions) {
                        curl_easy_cleanup(slot->curl);
                        slot->curl = NULL;
                        curl_session_count--;
                }
        }
        fill_active_slots();
}

void finish_all_active_slots(void)
{
        struct active_request_slot *slot = active_queue_head;

        while (slot != NULL)
                if (slot->in_use) {
                        run_active_slot(slot);
                        slot = active_queue_head;
                } else {
                        slot = slot->next;
                }
}

/* Helpers for modifying and creating URLs */
static inline int needs_quote(int ch)
{
        if (((ch >= 'A') && (ch <= 'Z'))
                        || ((ch >= 'a') && (ch <= 'z'))
                        || ((ch >= '0') && (ch <= '9'))
                        || (ch == '/')
                        || (ch == '-')
                        || (ch == '.'))
                return 0;
        return 1;
}

static char *quote_ref_url(const char *base, const char *ref)
{
        struct strbuf buf = STRBUF_INIT;
        const char *cp;
        int ch;

        end_url_with_slash(&buf, base);

        for (cp = ref; (ch = *cp) != 0; cp++)
                if (needs_quote(ch))
                        strbuf_addf(&buf, "%%%02x", ch);
                else
                        strbuf_addch(&buf, *cp);

        return strbuf_detach(&buf, NULL);
}

void append_remote_object_url(struct strbuf *buf, const char *url,
                              const char *hex,
                              int only_two_digit_prefix)
{
        end_url_with_slash(buf, url);

        strbuf_addf(buf, "objects/%.*s/", 2, hex);
        if (!only_two_digit_prefix)
                strbuf_addstr(buf, hex + 2);
}

char *get_remote_object_url(const char *url, const char *hex,
                            int only_two_digit_prefix)
{
        struct strbuf buf = STRBUF_INIT;
        append_remote_object_url(&buf, url, hex, only_two_digit_prefix);
        return strbuf_detach(&buf, NULL);
}

void normalize_curl_result(CURLcode *result, long http_code,
                           char *errorstr, size_t errorlen)
{
        /*
         * If we see a failing http code with CURLE_OK, we have turned off
         * FAILONERROR (to keep the server's custom error response), and should
         * translate the code into failure here.
         *
         * Likewise, if we see a redirect (30x code), that means we turned off
         * redirect-following, and we should treat the result as an error.
         */
        if (*result == CURLE_OK && http_code >= 300) {
                *result = CURLE_HTTP_RETURNED_ERROR;
                /*
                 * Normally curl will already have put the "reason phrase"
                 * from the server into curl_errorstr; unfortunately without
                 * FAILONERROR it is lost, so we can give only the numeric
                 * status code.
                 */
                xsnprintf(errorstr, errorlen,
                          "The requested URL returned error: %ld",
                          http_code);
        }
}

static int handle_curl_result(struct slot_results *results)
{
        normalize_curl_result(&results->curl_result, results->http_code,
                              curl_errorstr, sizeof(curl_errorstr));

        if (results->curl_result == CURLE_OK) {
                credential_approve(&http_auth);
                credential_approve(&proxy_auth);
                credential_approve(&cert_auth);
                return HTTP_OK;
        } else if (results->curl_result == CURLE_SSL_CERTPROBLEM) {
                /*
                 * We can't tell from here whether it's a bad path, bad
                 * certificate, bad password, or something else wrong
                 * with the certificate.  So we reject the credential to
                 * avoid caching or saving a bad password.
                 */
                credential_reject(&cert_auth);
                return HTTP_NOAUTH;
#ifdef GIT_CURL_HAVE_CURLE_SSL_PINNEDPUBKEYNOTMATCH
        } else if (results->curl_result == CURLE_SSL_PINNEDPUBKEYNOTMATCH) {
                return HTTP_NOMATCHPUBLICKEY;
#endif
        } else if (missing_target(results))
                return HTTP_MISSING_TARGET;
        else if (results->http_code == 401) {
                if (http_auth.username && http_auth.password) {
                        credential_reject(&http_auth);
                        return HTTP_NOAUTH;
                } else {
                        http_auth_methods &= ~CURLAUTH_GSSNEGOTIATE;
                        if (results->auth_avail) {
                                http_auth_methods &= results->auth_avail;
                                http_auth_methods_restricted = 1;
                        }
                        return HTTP_REAUTH;
                }
        } else {
                if (results->http_connectcode == 407)
                        credential_reject(&proxy_auth);
                if (!curl_errorstr[0])
                        strlcpy(curl_errorstr,
                                curl_easy_strerror(results->curl_result),
                                sizeof(curl_errorstr));
                return HTTP_ERROR;
        }
}

int run_one_slot(struct active_request_slot *slot,
                 struct slot_results *results)
{
        slot->results = results;
        if (!start_active_slot(slot)) {
                xsnprintf(curl_errorstr, sizeof(curl_errorstr),
                          "failed to start HTTP request");
                return HTTP_START_FAILED;
        }

        run_active_slot(slot);
        return handle_curl_result(results);
}

struct curl_slist *http_copy_default_headers(void)
{
        struct curl_slist *headers = NULL;
        const struct string_list_item *item;

        for_each_string_list_item(item, &extra_http_headers)
                headers = curl_slist_append(headers, item->string);

        return headers;
}

static CURLcode curlinfo_strbuf(CURL *curl, CURLINFO info, struct strbuf *buf)
{
        char *ptr;
        CURLcode ret;

        strbuf_reset(buf);
        ret = curl_easy_getinfo(curl, info, &ptr);
        if (!ret && ptr)
                strbuf_addstr(buf, ptr);
        return ret;
}

/*
 * Check for and extract a content-type parameter. "raw"
 * should be positioned at the start of the potential
 * parameter, with any whitespace already removed.
 *
 * "name" is the name of the parameter. The value is appended
 * to "out".
 */
static int extract_param(const char *raw, const char *name,
                         struct strbuf *out)
{
        size_t len = strlen(name);

        if (strncasecmp(raw, name, len))
                return -1;
        raw += len;

        if (*raw != '=')
                return -1;
        raw++;

        while (*raw && !isspace(*raw) && *raw != ';')
                strbuf_addch(out, *raw++);
        return 0;
}

/*
 * Extract a normalized version of the content type, with any
 * spaces suppressed, all letters lowercased, and no trailing ";"
 * or parameters.
 *
 * Note that we will silently remove even invalid whitespace. For
 * example, "text / plain" is specifically forbidden by RFC 2616,
 * but "text/plain" is the only reasonable output, and this keeps
 * our code simple.
 *
 * If the "charset" argument is not NULL, store the value of any
 * charset parameter there.
 *
 * Example:
 *   "TEXT/PLAIN; charset=utf-8" -> "text/plain", "utf-8"
 *   "text / plain" -> "text/plain"
 */
static void extract_content_type(struct strbuf *raw, struct strbuf *type,
                                 struct strbuf *charset)
{
        const char *p;

        strbuf_reset(type);
        strbuf_grow(type, raw->len);
        for (p = raw->buf; *p; p++) {
                if (isspace(*p))
                        continue;
                if (*p == ';') {
                        p++;
                        break;
                }
                strbuf_addch(type, tolower(*p));
        }

        if (!charset)
                return;

        strbuf_reset(charset);
        while (*p) {
                while (isspace(*p) || *p == ';')
                        p++;
                if (!extract_param(p, "charset", charset))
                        return;
                while (*p && !isspace(*p))
                        p++;
        }

        if (!charset->len && starts_with(type->buf, "text/"))
                strbuf_addstr(charset, "ISO-8859-1");
}

static void write_accept_language(struct strbuf *buf)
{
        /*
         * MAX_DECIMAL_PLACES must not be larger than 3. If it is larger than
         * that, q-value will be smaller than 0.001, the minimum q-value the
         * HTTP specification allows. See
         * http://tools.ietf.org/html/rfc7231#section-5.3.1 for q-value.
         */
        const int MAX_DECIMAL_PLACES = 3;
        const int MAX_LANGUAGE_TAGS = 1000;
        const int MAX_ACCEPT_LANGUAGE_HEADER_SIZE = 4000;
        char **language_tags = NULL;
        int num_langs = 0;
        const char *s = get_preferred_languages();
        int i;
        struct strbuf tag = STRBUF_INIT;

        /* Don't add Accept-Language header if no language is preferred. */
        if (!s)
                return;

        /*
         * Split the colon-separated string of preferred languages into
         * language_tags array.
         */
        do {
                /* collect language tag */
                for (; *s && (isalnum(*s) || *s == '_'); s++)
                        strbuf_addch(&tag, *s == '_' ? '-' : *s);

                /* skip .codeset, @modifier and any other unnecessary parts */
                while (*s && *s != ':')
                        s++;

                if (tag.len) {
                        num_langs++;
                        REALLOC_ARRAY(language_tags, num_langs);
                        language_tags[num_langs - 1] = strbuf_detach(&tag, NULL);
                        if (num_langs >= MAX_LANGUAGE_TAGS - 1) /* -1 for '*' */
                                break;
                }
        } while (*s++);

        /* write Accept-Language header into buf */
        if (num_langs) {
                int last_buf_len = 0;
                int max_q;
                int decimal_places;
                char q_format[32];

                /* add '*' */
                REALLOC_ARRAY(language_tags, num_langs + 1);
                language_tags[num_langs++] = "*"; /* it's OK; this won't be freed */

                /* compute decimal_places */
                for (max_q = 1, decimal_places = 0;
                     max_q < num_langs && decimal_places <= MAX_DECIMAL_PLACES;
                     decimal_places++, max_q *= 10)
                        ;

                xsnprintf(q_format, sizeof(q_format), ";q=0.%%0%dd", decimal_places);

                strbuf_addstr(buf, "Accept-Language: ");

                for (i = 0; i < num_langs; i++) {
                        if (i > 0)
                                strbuf_addstr(buf, ", ");

                        strbuf_addstr(buf, language_tags[i]);

                        if (i > 0)
                                strbuf_addf(buf, q_format, max_q - i);

                        if (buf->len > MAX_ACCEPT_LANGUAGE_HEADER_SIZE) {
                                strbuf_remove(buf, last_buf_len, buf->len - last_buf_len);
                                break;
                        }

                        last_buf_len = buf->len;
                }
        }

        /* free language tags -- last one is a static '*' */
        for (i = 0; i < num_langs - 1; i++)
                free(language_tags[i]);
        free(language_tags);
}

/*
 * Get an Accept-Language header which indicates user's preferred languages.
 *
 * Examples:
 *   LANGUAGE= -> ""
 *   LANGUAGE=ko:en -> "Accept-Language: ko, en; q=0.9, *; q=0.1"
 *   LANGUAGE=ko_KR.UTF-8:sr@latin -> "Accept-Language: ko-KR, sr; q=0.9, *; q=0.1"
 *   LANGUAGE=ko LANG=en_US.UTF-8 -> "Accept-Language: ko, *; q=0.1"
 *   LANGUAGE= LANG=en_US.UTF-8 -> "Accept-Language: en-US, *; q=0.1"
 *   LANGUAGE= LANG=C -> ""
 */
const char *http_get_accept_language_header(void)
{
        if (!cached_accept_language) {
                struct strbuf buf = STRBUF_INIT;
                write_accept_language(&buf);
                if (buf.len > 0)
                        cached_accept_language = strbuf_detach(&buf, NULL);
        }

        return cached_accept_language;
}

static void http_opt_request_remainder(CURL *curl, off_t pos)
{
        char buf[128];
        xsnprintf(buf, sizeof(buf), "%"PRIuMAX"-", (uintmax_t)pos);
        curl_easy_setopt(curl, CURLOPT_RANGE, buf);
}

/* http_request() targets */
#define HTTP_REQUEST_STRBUF     0
#define HTTP_REQUEST_FILE       1

static int http_request(const char *url,
                        void *result, int target,
                        const struct http_get_options *options)
{
        struct active_request_slot *slot;
        struct slot_results results;
        struct curl_slist *headers = http_copy_default_headers();
        struct strbuf buf = STRBUF_INIT;
        const char *accept_language;
        int ret;

        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);

        if (!result) {
                curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 1);
        } else {
                curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 0);
                curl_easy_setopt(slot->curl, CURLOPT_WRITEDATA, result);

                if (target == HTTP_REQUEST_FILE) {
                        off_t posn = ftello(result);
                        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
                                         fwrite);
                        if (posn > 0)
                                http_opt_request_remainder(slot->curl, posn);
                } else
                        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
                                         fwrite_buffer);
        }

        curl_easy_setopt(slot->curl, CURLOPT_HEADERFUNCTION, fwrite_wwwauth);

        accept_language = http_get_accept_language_header();

        if (accept_language)
                headers = curl_slist_append(headers, accept_language);

        strbuf_addstr(&buf, "Pragma:");
        if (options && options->no_cache)
                strbuf_addstr(&buf, " no-cache");
        if (options && options->initial_request &&
            http_follow_config == HTTP_FOLLOW_INITIAL)
                curl_easy_setopt(slot->curl, CURLOPT_FOLLOWLOCATION, 1);

        headers = curl_slist_append(headers, buf.buf);

        /* Add additional headers here */
        if (options && options->extra_headers) {
                const struct string_list_item *item;
                for_each_string_list_item(item, options->extra_headers) {
                        headers = curl_slist_append(headers, item->string);
                }
        }

        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(slot->curl, CURLOPT_ENCODING, "");
        curl_easy_setopt(slot->curl, CURLOPT_FAILONERROR, 0);

        ret = run_one_slot(slot, &results);

        if (options && options->content_type) {
                struct strbuf raw = STRBUF_INIT;
                curlinfo_strbuf(slot->curl, CURLINFO_CONTENT_TYPE, &raw);
                extract_content_type(&raw, options->content_type,
                                     options->charset);
                strbuf_release(&raw);
        }

        if (options && options->effective_url)
                curlinfo_strbuf(slot->curl, CURLINFO_EFFECTIVE_URL,
                                options->effective_url);

        curl_slist_free_all(headers);
        strbuf_release(&buf);

        return ret;
}

/*
 * Update the "base" url to a more appropriate value, as deduced by
 * redirects seen when requesting a URL starting with "url".
 *
 * The "asked" parameter is a URL that we asked curl to access, and must begin
 * with "base".
 *
 * The "got" parameter is the URL that curl reported to us as where we ended
 * up.
 *
 * Returns 1 if we updated the base url, 0 otherwise.
 *
 * Our basic strategy is to compare "base" and "asked" to find the bits
 * specific to our request. We then strip those bits off of "got" to yield the
 * new base. So for example, if our base is "http://example.com/foo.git",
 * and we ask for "http://example.com/foo.git/info/refs", we might end up
 * with "https://other.example.com/foo.git/info/refs". We would want the
 * new URL to become "https://other.example.com/foo.git".
 *
 * Note that this assumes a sane redirect scheme. It's entirely possible
 * in the example above to end up at a URL that does not even end in
 * "info/refs".  In such a case we die. There's not much we can do, such a
 * scheme is unlikely to represent a real git repository, and failing to
 * rewrite the base opens options for malicious redirects to do funny things.
 */
static int update_url_from_redirect(struct strbuf *base,
                                    const char *asked,
                                    const struct strbuf *got)
{
        const char *tail;
        size_t new_len;

        if (!strcmp(asked, got->buf))
                return 0;

        if (!skip_prefix(asked, base->buf, &tail))
                BUG("update_url_from_redirect: %s is not a superset of %s",
                    asked, base->buf);

        new_len = got->len;
        if (!strip_suffix_mem(got->buf, &new_len, tail))
                die(_("unable to update url base from redirection:\n"
                      "  asked for: %s\n"
                      "   redirect: %s"),
                    asked, got->buf);

        strbuf_reset(base);
        strbuf_add(base, got->buf, new_len);

        return 1;
}

static int http_request_reauth(const char *url,
                               void *result, int target,
                               struct http_get_options *options)
{
        int ret = http_request(url, result, target, options);

        if (ret != HTTP_OK && ret != HTTP_REAUTH)
                return ret;

        if (options && options->effective_url && options->base_url) {
                if (update_url_from_redirect(options->base_url,
                                             url, options->effective_url)) {
                        credential_from_url(&http_auth, options->base_url->buf);
                        url = options->effective_url->buf;
                }
        }

        if (ret != HTTP_REAUTH)
                return ret;

        /*
         * The previous request may have put cruft into our output stream; we
         * should clear it out before making our next request.
         */
        switch (target) {
        case HTTP_REQUEST_STRBUF:
                strbuf_reset(result);
                break;
        case HTTP_REQUEST_FILE:
                if (fflush(result)) {
                        error_errno("unable to flush a file");
                        return HTTP_START_FAILED;
                }
                rewind(result);
                if (ftruncate(fileno(result), 0) < 0) {
                        error_errno("unable to truncate a file");
                        return HTTP_START_FAILED;
                }
                break;
        default:
                BUG("Unknown http_request target");
        }

        credential_fill(&http_auth);

        return http_request(url, result, target, options);
}

int http_get_strbuf(const char *url,
                    struct strbuf *result,
                    struct http_get_options *options)
{
        return http_request_reauth(url, result, HTTP_REQUEST_STRBUF, options);
}

/*
 * Downloads a URL and stores the result in the given file.
 *
 * If a previous interrupted download is detected (i.e. a previous temporary
 * file is still around) the download is resumed.
 */
int http_get_file(const char *url, const char *filename,
                  struct http_get_options *options)
{
        int ret;
        struct strbuf tmpfile = STRBUF_INIT;
        FILE *result;

        strbuf_addf(&tmpfile, "%s.temp", filename);
        result = fopen(tmpfile.buf, "a");
        if (!result) {
                error("Unable to open local file %s", tmpfile.buf);
                ret = HTTP_ERROR;
                goto cleanup;
        }

        ret = http_request_reauth(url, result, HTTP_REQUEST_FILE, options);
        fclose(result);

        if (ret == HTTP_OK && finalize_object_file(tmpfile.buf, filename))
                ret = HTTP_ERROR;
cleanup:
        strbuf_release(&tmpfile);
        return ret;
}

int http_fetch_ref(const char *base, struct ref *ref)
{
        struct http_get_options options = {0};
        char *url;
        struct strbuf buffer = STRBUF_INIT;
        int ret = -1;

        options.no_cache = 1;

        url = quote_ref_url(base, ref->name);
        if (http_get_strbuf(url, &buffer, &options) == HTTP_OK) {
                strbuf_rtrim(&buffer);
                if (buffer.len == the_hash_algo->hexsz)
                        ret = get_oid_hex(buffer.buf, &ref->old_oid);
                else if (starts_with(buffer.buf, "ref: ")) {
                        ref->symref = xstrdup(buffer.buf + 5);
                        ret = 0;
                }
        }

        strbuf_release(&buffer);
        free(url);
        return ret;
}

/* Helpers for fetching packs */
static char *fetch_pack_index(unsigned char *hash, const char *base_url)
{
        char *url, *tmp;
        struct strbuf buf = STRBUF_INIT;

        if (http_is_verbose)
                fprintf(stderr, "Getting index for pack %s\n", hash_to_hex(hash));

        end_url_with_slash(&buf, base_url);
        strbuf_addf(&buf, "objects/pack/pack-%s.idx", hash_to_hex(hash));
        url = strbuf_detach(&buf, NULL);

        strbuf_addf(&buf, "%s.temp", sha1_pack_index_name(hash));
        tmp = strbuf_detach(&buf, NULL);

        if (http_get_file(url, tmp, NULL) != HTTP_OK) {
                error("Unable to get pack index %s", url);
                FREE_AND_NULL(tmp);
        }

        free(url);
        return tmp;
}

static int fetch_and_setup_pack_index(struct packed_git **packs_head,
        unsigned char *sha1, const char *base_url)
{
        struct packed_git *new_pack;
        char *tmp_idx = NULL;
        int ret;

        if (has_pack_index(sha1)) {
                new_pack = parse_pack_index(sha1, sha1_pack_index_name(sha1));
                if (!new_pack)
                        return -1; /* parse_pack_index() already issued error message */
                goto add_pack;
        }

        tmp_idx = fetch_pack_index(sha1, base_url);
        if (!tmp_idx)
                return -1;

        new_pack = parse_pack_index(sha1, tmp_idx);
        if (!new_pack) {
                unlink(tmp_idx);
                free(tmp_idx);

                return -1; /* parse_pack_index() already issued error message */
        }

        ret = verify_pack_index(new_pack);
        if (!ret) {
                close_pack_index(new_pack);
                ret = finalize_object_file(tmp_idx, sha1_pack_index_name(sha1));
        }
        free(tmp_idx);
        if (ret)
                return -1;

add_pack:
        new_pack->next = *packs_head;
        *packs_head = new_pack;
        return 0;
}

int http_get_info_packs(const char *base_url, struct packed_git **packs_head)
{
        struct http_get_options options = {0};
        int ret = 0;
        char *url;
        const char *data;
        struct strbuf buf = STRBUF_INIT;
        struct object_id oid;

        end_url_with_slash(&buf, base_url);
        strbuf_addstr(&buf, "objects/info/packs");
        url = strbuf_detach(&buf, NULL);

        options.no_cache = 1;
        ret = http_get_strbuf(url, &buf, &options);
        if (ret != HTTP_OK)
                goto cleanup;

        data = buf.buf;
        while (*data) {
                if (skip_prefix(data, "P pack-", &data) &&
                    !parse_oid_hex(data, &oid, &data) &&
                    skip_prefix(data, ".pack", &data) &&
                    (*data == '\n' || *data == '\0')) {
                        fetch_and_setup_pack_index(packs_head, oid.hash, base_url);
                } else {
                        data = strchrnul(data, '\n');
                }
                if (*data)
                        data++; /* skip past newline */
        }

cleanup:
        free(url);
        return ret;
}

void release_http_pack_request(struct http_pack_request *preq)
{
        if (preq->packfile) {
                fclose(preq->packfile);
                preq->packfile = NULL;
        }
        preq->slot = NULL;
        strbuf_release(&preq->tmpfile);
        free(preq->url);
        free(preq);
}

static const char *default_index_pack_args[] =
        {"index-pack", "--stdin", NULL};

int finish_http_pack_request(struct http_pack_request *preq)
{
        struct child_process ip = CHILD_PROCESS_INIT;
        int tmpfile_fd;
        int ret = 0;

        fclose(preq->packfile);
        preq->packfile = NULL;

        tmpfile_fd = xopen(preq->tmpfile.buf, O_RDONLY);

        ip.git_cmd = 1;
        ip.in = tmpfile_fd;
        strvec_pushv(&ip.args, preq->index_pack_args ?
                     preq->index_pack_args :
                     default_index_pack_args);

        if (preq->preserve_index_pack_stdout)
                ip.out = 0;
        else
                ip.no_stdout = 1;

        if (run_command(&ip)) {
                ret = -1;
                goto cleanup;
        }

cleanup:
        close(tmpfile_fd);
        unlink(preq->tmpfile.buf);
        return ret;
}

void http_install_packfile(struct packed_git *p,
                           struct packed_git **list_to_remove_from)
{
        struct packed_git **lst = list_to_remove_from;

        while (*lst != p)
                lst = &((*lst)->next);
        *lst = (*lst)->next;

        install_packed_git(the_repository, p);
}

struct http_pack_request *new_http_pack_request(
        const unsigned char *packed_git_hash, const char *base_url) {

        struct strbuf buf = STRBUF_INIT;

        end_url_with_slash(&buf, base_url);
        strbuf_addf(&buf, "objects/pack/pack-%s.pack",
                hash_to_hex(packed_git_hash));
        return new_direct_http_pack_request(packed_git_hash,
                                            strbuf_detach(&buf, NULL));
}

struct http_pack_request *new_direct_http_pack_request(
        const unsigned char *packed_git_hash, char *url)
{
        off_t prev_posn = 0;
        struct http_pack_request *preq;

        CALLOC_ARRAY(preq, 1);
        strbuf_init(&preq->tmpfile, 0);

        preq->url = url;

        strbuf_addf(&preq->tmpfile, "%s.temp", sha1_pack_name(packed_git_hash));
        preq->packfile = fopen(preq->tmpfile.buf, "a");
        if (!preq->packfile) {
                error("Unable to open local file %s for pack",
                      preq->tmpfile.buf);
                goto abort;
        }

        preq->slot = get_active_slot();
        curl_easy_setopt(preq->slot->curl, CURLOPT_WRITEDATA, preq->packfile);
        curl_easy_setopt(preq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
        curl_easy_setopt(preq->slot->curl, CURLOPT_URL, preq->url);
        curl_easy_setopt(preq->slot->curl, CURLOPT_HTTPHEADER,
                no_pragma_header);

        /*
         * If there is data present from a previous transfer attempt,
         * resume where it left off
         */
        prev_posn = ftello(preq->packfile);
        if (prev_posn>0) {
                if (http_is_verbose)
                        fprintf(stderr,
                                "Resuming fetch of pack %s at byte %"PRIuMAX"\n",
                                hash_to_hex(packed_git_hash),
                                (uintmax_t)prev_posn);
                http_opt_request_remainder(preq->slot->curl, prev_posn);
        }

        return preq;

abort:
        strbuf_release(&preq->tmpfile);
        free(preq->url);
        free(preq);
        return NULL;
}

/* Helpers for fetching objects (loose) */
static size_t fwrite_sha1_file(char *ptr, size_t eltsize, size_t nmemb,
                               void *data)
{
        unsigned char expn[4096];
        size_t size = eltsize * nmemb;
        int posn = 0;
        struct http_object_request *freq = data;
        struct active_request_slot *slot = freq->slot;

        if (slot) {
                CURLcode c = curl_easy_getinfo(slot->curl, CURLINFO_HTTP_CODE,
                                                &slot->http_code);
                if (c != CURLE_OK)
                        BUG("curl_easy_getinfo for HTTP code failed: %s",
                                curl_easy_strerror(c));
                if (slot->http_code >= 300)
                        return nmemb;
        }

        do {
                ssize_t retval = xwrite(freq->localfile,
                                        (char *) ptr + posn, size - posn);
                if (retval < 0)
                        return posn / eltsize;
                posn += retval;
        } while (posn < size);

        freq->stream.avail_in = size;
        freq->stream.next_in = (void *)ptr;
        do {
                freq->stream.next_out = expn;
                freq->stream.avail_out = sizeof(expn);
                freq->zret = git_inflate(&freq->stream, Z_SYNC_FLUSH);
                the_hash_algo->update_fn(&freq->c, expn,
                                         sizeof(expn) - freq->stream.avail_out);
        } while (freq->stream.avail_in && freq->zret == Z_OK);
        return nmemb;
}

struct http_object_request *new_http_object_request(const char *base_url,
                                                    const struct object_id *oid)
{
        char *hex = oid_to_hex(oid);
        struct strbuf filename = STRBUF_INIT;
        struct strbuf prevfile = STRBUF_INIT;
        int prevlocal;
        char prev_buf[PREV_BUF_SIZE];
        ssize_t prev_read = 0;
        off_t prev_posn = 0;
        struct http_object_request *freq;

        CALLOC_ARRAY(freq, 1);
        strbuf_init(&freq->tmpfile, 0);
        oidcpy(&freq->oid, oid);
        freq->localfile = -1;

        loose_object_path(the_repository, &filename, oid);
        strbuf_addf(&freq->tmpfile, "%s.temp", filename.buf);

        strbuf_addf(&prevfile, "%s.prev", filename.buf);
        unlink_or_warn(prevfile.buf);
        rename(freq->tmpfile.buf, prevfile.buf);
        unlink_or_warn(freq->tmpfile.buf);
        strbuf_release(&filename);

        if (freq->localfile != -1)
                error("fd leakage in start: %d", freq->localfile);
        freq->localfile = open(freq->tmpfile.buf,
                               O_WRONLY | O_CREAT | O_EXCL, 0666);
        /*
         * This could have failed due to the "lazy directory creation";
         * try to mkdir the last path component.
         */
        if (freq->localfile < 0 && errno == ENOENT) {
                char *dir = strrchr(freq->tmpfile.buf, '/');
                if (dir) {
                        *dir = 0;
                        mkdir(freq->tmpfile.buf, 0777);
                        *dir = '/';
                }
                freq->localfile = open(freq->tmpfile.buf,
                                       O_WRONLY | O_CREAT | O_EXCL, 0666);
        }

        if (freq->localfile < 0) {
                error_errno("Couldn't create temporary file %s",
                            freq->tmpfile.buf);
                goto abort;
        }

        git_inflate_init(&freq->stream);

        the_hash_algo->init_fn(&freq->c);

        freq->url = get_remote_object_url(base_url, hex, 0);

        /*
         * If a previous temp file is present, process what was already
         * fetched.
         */
        prevlocal = open(prevfile.buf, O_RDONLY);
        if (prevlocal != -1) {
                do {
                        prev_read = xread(prevlocal, prev_buf, PREV_BUF_SIZE);
                        if (prev_read>0) {
                                if (fwrite_sha1_file(prev_buf,
                                                     1,
                                                     prev_read,
                                                     freq) == prev_read) {
                                        prev_posn += prev_read;
                                } else {
                                        prev_read = -1;
                                }
                        }
                } while (prev_read > 0);
                close(prevlocal);
        }
        unlink_or_warn(prevfile.buf);
        strbuf_release(&prevfile);

        /*
         * Reset inflate/SHA1 if there was an error reading the previous temp
         * file; also rewind to the beginning of the local file.
         */
        if (prev_read == -1) {
                memset(&freq->stream, 0, sizeof(freq->stream));
                git_inflate_init(&freq->stream);
                the_hash_algo->init_fn(&freq->c);
                if (prev_posn>0) {
                        prev_posn = 0;
                        lseek(freq->localfile, 0, SEEK_SET);
                        if (ftruncate(freq->localfile, 0) < 0) {
                                error_errno("Couldn't truncate temporary file %s",
                                            freq->tmpfile.buf);
                                goto abort;
                        }
                }
        }

        freq->slot = get_active_slot();

        curl_easy_setopt(freq->slot->curl, CURLOPT_WRITEDATA, freq);
        curl_easy_setopt(freq->slot->curl, CURLOPT_FAILONERROR, 0);
        curl_easy_setopt(freq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
        curl_easy_setopt(freq->slot->curl, CURLOPT_ERRORBUFFER, freq->errorstr);
        curl_easy_setopt(freq->slot->curl, CURLOPT_URL, freq->url);
        curl_easy_setopt(freq->slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);

        /*
         * If we have successfully processed data from a previous fetch
         * attempt, only fetch the data we don't already have.
         */
        if (prev_posn>0) {
                if (http_is_verbose)
                        fprintf(stderr,
                                "Resuming fetch of object %s at byte %"PRIuMAX"\n",
                                hex, (uintmax_t)prev_posn);
                http_opt_request_remainder(freq->slot->curl, prev_posn);
        }

        return freq;

abort:
        strbuf_release(&prevfile);
        free(freq->url);
        free(freq);
        return NULL;
}

void process_http_object_request(struct http_object_request *freq)
{
        if (!freq->slot)
                return;
        freq->curl_result = freq->slot->curl_result;
        freq->http_code = freq->slot->http_code;
        freq->slot = NULL;
}

int finish_http_object_request(struct http_object_request *freq)
{
        struct stat st;
        struct strbuf filename = STRBUF_INIT;

        close(freq->localfile);
        freq->localfile = -1;

        process_http_object_request(freq);

        if (freq->http_code == 416) {
                warning("requested range invalid; we may already have all the data.");
        } else if (freq->curl_result != CURLE_OK) {
                if (stat(freq->tmpfile.buf, &st) == 0)
                        if (st.st_size == 0)
                                unlink_or_warn(freq->tmpfile.buf);
                return -1;
        }

        git_inflate_end(&freq->stream);
        the_hash_algo->final_oid_fn(&freq->real_oid, &freq->c);
        if (freq->zret != Z_STREAM_END) {
                unlink_or_warn(freq->tmpfile.buf);
                return -1;
        }
        if (!oideq(&freq->oid, &freq->real_oid)) {
                unlink_or_warn(freq->tmpfile.buf);
                return -1;
        }
        loose_object_path(the_repository, &filename, &freq->oid);
        freq->rename = finalize_object_file(freq->tmpfile.buf, filename.buf);
        strbuf_release(&filename);

        return freq->rename;
}

void abort_http_object_request(struct http_object_request *freq)
{
        unlink_or_warn(freq->tmpfile.buf);

        release_http_object_request(freq);
}

void release_http_object_request(struct http_object_request *freq)
{
        if (freq->localfile != -1) {
                close(freq->localfile);
                freq->localfile = -1;
        }
        FREE_AND_NULL(freq->url);
        if (freq->slot) {
                freq->slot->callback_func = NULL;
                freq->slot->callback_data = NULL;
                release_active_slot(freq->slot);
                freq->slot = NULL;
        }
        strbuf_release(&freq->tmpfile);
}