Git 2.43.1

[alt-git.git] / imap-send.c

/*
 * git-imap-send - drops patches into an imap Drafts folder
 *                 derived from isync/mbsync - mailbox synchronizer
 *
 * Copyright (C) 2000-2002 Michael R. Elkins <me@mutt.org>
 * Copyright (C) 2002-2004 Oswald Buddenhagen <ossi@users.sf.net>
 * Copyright (C) 2004 Theodore Y. Ts'o <tytso@mit.edu>
 * Copyright (C) 2006 Mike McCormack
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, see <https://www.gnu.org/licenses/>.
 */

#include "git-compat-util.h"
#include "config.h"
#include "credential.h"
#include "gettext.h"
#include "run-command.h"
#include "parse-options.h"
#include "setup.h"
#if defined(NO_OPENSSL) && !defined(HAVE_OPENSSL_CSPRNG)
typedef void *SSL;
#endif
#ifdef USE_CURL_FOR_IMAP_SEND
#include "http.h"
#endif

#if defined(USE_CURL_FOR_IMAP_SEND)
/* Always default to curl if it's available. */
#define USE_CURL_DEFAULT 1
#else
/* We don't have curl, so continue to use the historical implementation */
#define USE_CURL_DEFAULT 0
#endif

static int verbosity;
static int use_curl = USE_CURL_DEFAULT;

static const char * const imap_send_usage[] = { "git imap-send [-v] [-q] [--[no-]curl] < <mbox>", NULL };

static struct option imap_send_options[] = {
        OPT__VERBOSITY(&verbosity),
        OPT_BOOL(0, "curl", &use_curl, "use libcurl to communicate with the IMAP server"),
        OPT_END()
};

#undef DRV_OK
#define DRV_OK          0
#define DRV_MSG_BAD     -1
#define DRV_BOX_BAD     -2
#define DRV_STORE_BAD   -3

__attribute__((format (printf, 1, 2)))
static void imap_info(const char *, ...);
__attribute__((format (printf, 1, 2)))
static void imap_warn(const char *, ...);

static char *next_arg(char **);

__attribute__((format (printf, 3, 4)))
static int nfsnprintf(char *buf, int blen, const char *fmt, ...);

static int nfvasprintf(char **strp, const char *fmt, va_list ap)
{
        int len;
        char tmp[8192];

        len = vsnprintf(tmp, sizeof(tmp), fmt, ap);
        if (len < 0)
                die("Fatal: Out of memory");
        if (len >= sizeof(tmp))
                die("imap command overflow!");
        *strp = xmemdupz(tmp, len);
        return len;
}

struct imap_server_conf {
        const char *name;
        const char *tunnel;
        const char *host;
        int port;
        const char *folder;
        const char *user;
        const char *pass;
        int use_ssl;
        int ssl_verify;
        int use_html;
        const char *auth_method;
};

static struct imap_server_conf server = {
        .ssl_verify = 1,
};

struct imap_socket {
        int fd[2];
        SSL *ssl;
};

struct imap_buffer {
        struct imap_socket sock;
        int bytes;
        int offset;
        char buf[1024];
};

struct imap_cmd;

struct imap {
        int uidnext; /* from SELECT responses */
        unsigned caps, rcaps; /* CAPABILITY results */
        /* command queue */
        int nexttag, num_in_progress, literal_pending;
        struct imap_cmd *in_progress, **in_progress_append;
        struct imap_buffer buf; /* this is BIG, so put it last */
};

struct imap_store {
        /* currently open mailbox */
        const char *name; /* foreign! maybe preset? */
        int uidvalidity;
        struct imap *imap;
        const char *prefix;
};

struct imap_cmd_cb {
        int (*cont)(struct imap_store *ctx, const char *prompt);
        void *ctx;
        char *data;
        int dlen;
};

struct imap_cmd {
        struct imap_cmd *next;
        struct imap_cmd_cb cb;
        char *cmd;
        int tag;
};

#define CAP(cap) (imap->caps & (1 << (cap)))

enum CAPABILITY {
        NOLOGIN = 0,
        UIDPLUS,
        LITERALPLUS,
        NAMESPACE,
        STARTTLS,
        AUTH_CRAM_MD5
};

static const char *cap_list[] = {
        "LOGINDISABLED",
        "UIDPLUS",
        "LITERAL+",
        "NAMESPACE",
        "STARTTLS",
        "AUTH=CRAM-MD5",
};

#define RESP_OK    0
#define RESP_NO    1
#define RESP_BAD   2

static int get_cmd_result(struct imap_store *ctx, struct imap_cmd *tcmd);


#ifndef NO_OPENSSL
static void ssl_socket_perror(const char *func)
{
        fprintf(stderr, "%s: %s\n", func, ERR_error_string(ERR_get_error(), NULL));
}
#endif

static void socket_perror(const char *func, struct imap_socket *sock, int ret)
{
#ifndef NO_OPENSSL
        if (sock->ssl) {
                int sslerr = SSL_get_error(sock->ssl, ret);
                switch (sslerr) {
                case SSL_ERROR_NONE:
                        break;
                case SSL_ERROR_SYSCALL:
                        perror("SSL_connect");
                        break;
                default:
                        ssl_socket_perror("SSL_connect");
                        break;
                }
        } else
#endif
        {
                if (ret < 0)
                        perror(func);
                else
                        fprintf(stderr, "%s: unexpected EOF\n", func);
        }
        /* mark as used to appease -Wunused-parameter with NO_OPENSSL */
        (void)sock;
}

#ifdef NO_OPENSSL
static int ssl_socket_connect(struct imap_socket *sock UNUSED,
                              int use_tls_only UNUSED,
                              int verify UNUSED)
{
        fprintf(stderr, "SSL requested but SSL support not compiled in\n");
        return -1;
}

#else

static int host_matches(const char *host, const char *pattern)
{
        if (pattern[0] == '*' && pattern[1] == '.') {
                pattern += 2;
                if (!(host = strchr(host, '.')))
                        return 0;
                host++;
        }

        return *host && *pattern && !strcasecmp(host, pattern);
}

static int verify_hostname(X509 *cert, const char *hostname)
{
        int len;
        X509_NAME *subj;
        char cname[1000];
        int i, found;
        STACK_OF(GENERAL_NAME) *subj_alt_names;

        /* try the DNS subjectAltNames */
        found = 0;
        if ((subj_alt_names = X509_get_ext_d2i(cert, NID_subject_alt_name, NULL, NULL))) {
                int num_subj_alt_names = sk_GENERAL_NAME_num(subj_alt_names);
                for (i = 0; !found && i < num_subj_alt_names; i++) {
                        GENERAL_NAME *subj_alt_name = sk_GENERAL_NAME_value(subj_alt_names, i);
                        if (subj_alt_name->type == GEN_DNS &&
                            strlen((const char *)subj_alt_name->d.ia5->data) == (size_t)subj_alt_name->d.ia5->length &&
                            host_matches(hostname, (const char *)(subj_alt_name->d.ia5->data)))
                                found = 1;
                }
                sk_GENERAL_NAME_pop_free(subj_alt_names, GENERAL_NAME_free);
        }
        if (found)
                return 0;

        /* try the common name */
        if (!(subj = X509_get_subject_name(cert)))
                return error("cannot get certificate subject");
        if ((len = X509_NAME_get_text_by_NID(subj, NID_commonName, cname, sizeof(cname))) < 0)
                return error("cannot get certificate common name");
        if (strlen(cname) == (size_t)len && host_matches(hostname, cname))
                return 0;
        return error("certificate owner '%s' does not match hostname '%s'",
                     cname, hostname);
}

static int ssl_socket_connect(struct imap_socket *sock, int use_tls_only, int verify)
{
#if (OPENSSL_VERSION_NUMBER >= 0x10000000L)
        const SSL_METHOD *meth;
#else
        SSL_METHOD *meth;
#endif
        SSL_CTX *ctx;
        int ret;
        X509 *cert;

        SSL_library_init();
        SSL_load_error_strings();

        meth = SSLv23_method();
        if (!meth) {
                ssl_socket_perror("SSLv23_method");
                return -1;
        }

        ctx = SSL_CTX_new(meth);
        if (!ctx) {
                ssl_socket_perror("SSL_CTX_new");
                return -1;
        }

        if (use_tls_only)
                SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv2 | SSL_OP_NO_SSLv3);

        if (verify)
                SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);

        if (!SSL_CTX_set_default_verify_paths(ctx)) {
                ssl_socket_perror("SSL_CTX_set_default_verify_paths");
                return -1;
        }
        sock->ssl = SSL_new(ctx);
        if (!sock->ssl) {
                ssl_socket_perror("SSL_new");
                return -1;
        }
        if (!SSL_set_rfd(sock->ssl, sock->fd[0])) {
                ssl_socket_perror("SSL_set_rfd");
                return -1;
        }
        if (!SSL_set_wfd(sock->ssl, sock->fd[1])) {
                ssl_socket_perror("SSL_set_wfd");
                return -1;
        }

#ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
        /*
         * SNI (RFC4366)
         * OpenSSL does not document this function, but the implementation
         * returns 1 on success, 0 on failure after calling SSLerr().
         */
        ret = SSL_set_tlsext_host_name(sock->ssl, server.host);
        if (ret != 1)
                warning("SSL_set_tlsext_host_name(%s) failed.", server.host);
#endif

        ret = SSL_connect(sock->ssl);
        if (ret <= 0) {
                socket_perror("SSL_connect", sock, ret);
                return -1;
        }

        if (verify) {
                /* make sure the hostname matches that of the certificate */
                cert = SSL_get_peer_certificate(sock->ssl);
                if (!cert)
                        return error("unable to get peer certificate.");
                if (verify_hostname(cert, server.host) < 0)
                        return -1;
        }

        return 0;
}
#endif

static int socket_read(struct imap_socket *sock, char *buf, int len)
{
        ssize_t n;
#ifndef NO_OPENSSL
        if (sock->ssl)
                n = SSL_read(sock->ssl, buf, len);
        else
#endif
                n = xread(sock->fd[0], buf, len);
        if (n <= 0) {
                socket_perror("read", sock, n);
                close(sock->fd[0]);
                close(sock->fd[1]);
                sock->fd[0] = sock->fd[1] = -1;
        }
        return n;
}

static int socket_write(struct imap_socket *sock, const char *buf, int len)
{
        int n;
#ifndef NO_OPENSSL
        if (sock->ssl)
                n = SSL_write(sock->ssl, buf, len);
        else
#endif
                n = write_in_full(sock->fd[1], buf, len);
        if (n != len) {
                socket_perror("write", sock, n);
                close(sock->fd[0]);
                close(sock->fd[1]);
                sock->fd[0] = sock->fd[1] = -1;
        }
        return n;
}

static void socket_shutdown(struct imap_socket *sock)
{
#ifndef NO_OPENSSL
        if (sock->ssl) {
                SSL_shutdown(sock->ssl);
                SSL_free(sock->ssl);
        }
#endif
        close(sock->fd[0]);
        close(sock->fd[1]);
}

/* simple line buffering */
static int buffer_gets(struct imap_buffer *b, char **s)
{
        int n;
        int start = b->offset;

        *s = b->buf + start;

        for (;;) {
                /* make sure we have enough data to read the \r\n sequence */
                if (b->offset + 1 >= b->bytes) {
                        if (start) {
                                /* shift down used bytes */
                                *s = b->buf;

                                assert(start <= b->bytes);
                                n = b->bytes - start;

                                if (n)
                                        memmove(b->buf, b->buf + start, n);
                                b->offset -= start;
                                b->bytes = n;
                                start = 0;
                        }

                        n = socket_read(&b->sock, b->buf + b->bytes,
                                         sizeof(b->buf) - b->bytes);

                        if (n <= 0)
                                return -1;

                        b->bytes += n;
                }

                if (b->buf[b->offset] == '\r') {
                        assert(b->offset + 1 < b->bytes);
                        if (b->buf[b->offset + 1] == '\n') {
                                b->buf[b->offset] = 0;  /* terminate the string */
                                b->offset += 2; /* next line */
                                if (0 < verbosity)
                                        puts(*s);
                                return 0;
                        }
                }

                b->offset++;
        }
        /* not reached */
}

__attribute__((format (printf, 1, 2)))
static void imap_info(const char *msg, ...)
{
        va_list va;

        if (0 <= verbosity) {
                va_start(va, msg);
                vprintf(msg, va);
                va_end(va);
                fflush(stdout);
        }
}

__attribute__((format (printf, 1, 2)))
static void imap_warn(const char *msg, ...)
{
        va_list va;

        if (-2 < verbosity) {
                va_start(va, msg);
                vfprintf(stderr, msg, va);
                va_end(va);
        }
}

static char *next_arg(char **s)
{
        char *ret;

        if (!s || !*s)
                return NULL;
        while (isspace((unsigned char) **s))
                (*s)++;
        if (!**s) {
                *s = NULL;
                return NULL;
        }
        if (**s == '"') {
                ++*s;
                ret = *s;
                *s = strchr(*s, '"');
        } else {
                ret = *s;
                while (**s && !isspace((unsigned char) **s))
                        (*s)++;
        }
        if (*s) {
                if (**s)
                        *(*s)++ = 0;
                if (!**s)
                        *s = NULL;
        }
        return ret;
}

__attribute__((format (printf, 3, 4)))
static int nfsnprintf(char *buf, int blen, const char *fmt, ...)
{
        int ret;
        va_list va;

        va_start(va, fmt);
        if (blen <= 0 || (unsigned)(ret = vsnprintf(buf, blen, fmt, va)) >= (unsigned)blen)
                BUG("buffer too small. Please report a bug.");
        va_end(va);
        return ret;
}

static struct imap_cmd *issue_imap_cmd(struct imap_store *ctx,
                                       struct imap_cmd_cb *cb,
                                       const char *fmt, va_list ap)
{
        struct imap *imap = ctx->imap;
        struct imap_cmd *cmd;
        int n, bufl;
        char buf[1024];

        cmd = xmalloc(sizeof(struct imap_cmd));
        nfvasprintf(&cmd->cmd, fmt, ap);
        cmd->tag = ++imap->nexttag;

        if (cb)
                cmd->cb = *cb;
        else
                memset(&cmd->cb, 0, sizeof(cmd->cb));

        while (imap->literal_pending)
                get_cmd_result(ctx, NULL);

        if (!cmd->cb.data)
                bufl = nfsnprintf(buf, sizeof(buf), "%d %s\r\n", cmd->tag, cmd->cmd);
        else
                bufl = nfsnprintf(buf, sizeof(buf), "%d %s{%d%s}\r\n",
                                  cmd->tag, cmd->cmd, cmd->cb.dlen,
                                  CAP(LITERALPLUS) ? "+" : "");

        if (0 < verbosity) {
                if (imap->num_in_progress)
                        printf("(%d in progress) ", imap->num_in_progress);
                if (!starts_with(cmd->cmd, "LOGIN"))
                        printf(">>> %s", buf);
                else
                        printf(">>> %d LOGIN <user> <pass>\n", cmd->tag);
        }
        if (socket_write(&imap->buf.sock, buf, bufl) != bufl) {
                free(cmd->cmd);
                free(cmd);
                if (cb)
                        free(cb->data);
                return NULL;
        }
        if (cmd->cb.data) {
                if (CAP(LITERALPLUS)) {
                        n = socket_write(&imap->buf.sock, cmd->cb.data, cmd->cb.dlen);
                        free(cmd->cb.data);
                        if (n != cmd->cb.dlen ||
                            socket_write(&imap->buf.sock, "\r\n", 2) != 2) {
                                free(cmd->cmd);
                                free(cmd);
                                return NULL;
                        }
                        cmd->cb.data = NULL;
                } else
                        imap->literal_pending = 1;
        } else if (cmd->cb.cont)
                imap->literal_pending = 1;
        cmd->next = NULL;
        *imap->in_progress_append = cmd;
        imap->in_progress_append = &cmd->next;
        imap->num_in_progress++;
        return cmd;
}

__attribute__((format (printf, 3, 4)))
static int imap_exec(struct imap_store *ctx, struct imap_cmd_cb *cb,
                     const char *fmt, ...)
{
        va_list ap;
        struct imap_cmd *cmdp;

        va_start(ap, fmt);
        cmdp = issue_imap_cmd(ctx, cb, fmt, ap);
        va_end(ap);
        if (!cmdp)
                return RESP_BAD;

        return get_cmd_result(ctx, cmdp);
}

__attribute__((format (printf, 3, 4)))
static int imap_exec_m(struct imap_store *ctx, struct imap_cmd_cb *cb,
                       const char *fmt, ...)
{
        va_list ap;
        struct imap_cmd *cmdp;

        va_start(ap, fmt);
        cmdp = issue_imap_cmd(ctx, cb, fmt, ap);
        va_end(ap);
        if (!cmdp)
                return DRV_STORE_BAD;

        switch (get_cmd_result(ctx, cmdp)) {
        case RESP_BAD: return DRV_STORE_BAD;
        case RESP_NO: return DRV_MSG_BAD;
        default: return DRV_OK;
        }
}

static int skip_imap_list_l(char **sp, int level)
{
        char *s = *sp;

        for (;;) {
                while (isspace((unsigned char)*s))
                        s++;
                if (level && *s == ')') {
                        s++;
                        break;
                }
                if (*s == '(') {
                        /* sublist */
                        s++;
                        if (skip_imap_list_l(&s, level + 1))
                                goto bail;
                } else if (*s == '"') {
                        /* quoted string */
                        s++;
                        for (; *s != '"'; s++)
                                if (!*s)
                                        goto bail;
                        s++;
                } else {
                        /* atom */
                        for (; *s && !isspace((unsigned char)*s); s++)
                                if (level && *s == ')')
                                        break;
                }

                if (!level)
                        break;
                if (!*s)
                        goto bail;
        }
        *sp = s;
        return 0;

bail:
        return -1;
}

static void skip_list(char **sp)
{
        skip_imap_list_l(sp, 0);
}

static void parse_capability(struct imap *imap, char *cmd)
{
        char *arg;
        unsigned i;

        imap->caps = 0x80000000;
        while ((arg = next_arg(&cmd)))
                for (i = 0; i < ARRAY_SIZE(cap_list); i++)
                        if (!strcmp(cap_list[i], arg))
                                imap->caps |= 1 << i;
        imap->rcaps = imap->caps;
}

static int parse_response_code(struct imap_store *ctx, struct imap_cmd_cb *cb,
                               char *s)
{
        struct imap *imap = ctx->imap;
        char *arg, *p;

        if (!s || *s != '[')
                return RESP_OK;         /* no response code */
        s++;
        if (!(p = strchr(s, ']'))) {
                fprintf(stderr, "IMAP error: malformed response code\n");
                return RESP_BAD;
        }
        *p++ = 0;
        arg = next_arg(&s);
        if (!arg) {
                fprintf(stderr, "IMAP error: empty response code\n");
                return RESP_BAD;
        }
        if (!strcmp("UIDVALIDITY", arg)) {
                if (!(arg = next_arg(&s)) || !(ctx->uidvalidity = atoi(arg))) {
                        fprintf(stderr, "IMAP error: malformed UIDVALIDITY status\n");
                        return RESP_BAD;
                }
        } else if (!strcmp("UIDNEXT", arg)) {
                if (!(arg = next_arg(&s)) || !(imap->uidnext = atoi(arg))) {
                        fprintf(stderr, "IMAP error: malformed NEXTUID status\n");
                        return RESP_BAD;
                }
        } else if (!strcmp("CAPABILITY", arg)) {
                parse_capability(imap, s);
        } else if (!strcmp("ALERT", arg)) {
                /* RFC2060 says that these messages MUST be displayed
                 * to the user
                 */
                for (; isspace((unsigned char)*p); p++);
                fprintf(stderr, "*** IMAP ALERT *** %s\n", p);
        } else if (cb && cb->ctx && !strcmp("APPENDUID", arg)) {
                if (!(arg = next_arg(&s)) || !(ctx->uidvalidity = atoi(arg)) ||
                    !(arg = next_arg(&s)) || !(*(int *)cb->ctx = atoi(arg))) {
                        fprintf(stderr, "IMAP error: malformed APPENDUID status\n");
                        return RESP_BAD;
                }
        }
        return RESP_OK;
}

static int get_cmd_result(struct imap_store *ctx, struct imap_cmd *tcmd)
{
        struct imap *imap = ctx->imap;
        struct imap_cmd *cmdp, **pcmdp;
        char *cmd;
        const char *arg, *arg1;
        int n, resp, resp2, tag;

        for (;;) {
                if (buffer_gets(&imap->buf, &cmd))
                        return RESP_BAD;

                arg = next_arg(&cmd);
                if (!arg) {
                        fprintf(stderr, "IMAP error: empty response\n");
                        return RESP_BAD;
                }
                if (*arg == '*') {
                        arg = next_arg(&cmd);
                        if (!arg) {
                                fprintf(stderr, "IMAP error: unable to parse untagged response\n");
                                return RESP_BAD;
                        }

                        if (!strcmp("NAMESPACE", arg)) {
                                /* rfc2342 NAMESPACE response. */
                                skip_list(&cmd); /* Personal mailboxes */
                                skip_list(&cmd); /* Others' mailboxes */
                                skip_list(&cmd); /* Shared mailboxes */
                        } else if (!strcmp("OK", arg) || !strcmp("BAD", arg) ||
                                   !strcmp("NO", arg) || !strcmp("BYE", arg)) {
                                if ((resp = parse_response_code(ctx, NULL, cmd)) != RESP_OK)
                                        return resp;
                        } else if (!strcmp("CAPABILITY", arg)) {
                                parse_capability(imap, cmd);
                        } else if ((arg1 = next_arg(&cmd))) {
                                ; /*
                                   * Unhandled response-data with at least two words.
                                   * Ignore it.
                                   *
                                   * NEEDSWORK: Previously this case handled '<num> EXISTS'
                                   * and '<num> RECENT' but as a probably-unintended side
                                   * effect it ignores other unrecognized two-word
                                   * responses.  imap-send doesn't ever try to read
                                   * messages or mailboxes these days, so consider
                                   * eliminating this case.
                                   */
                        } else {
                                fprintf(stderr, "IMAP error: unable to parse untagged response\n");
                                return RESP_BAD;
                        }
                } else if (!imap->in_progress) {
                        fprintf(stderr, "IMAP error: unexpected reply: %s %s\n", arg, cmd ? cmd : "");
                        return RESP_BAD;
                } else if (*arg == '+') {
                        /* This can happen only with the last command underway, as
                           it enforces a round-trip. */
                        cmdp = (struct imap_cmd *)((char *)imap->in_progress_append -
                               offsetof(struct imap_cmd, next));
                        if (cmdp->cb.data) {
                                n = socket_write(&imap->buf.sock, cmdp->cb.data, cmdp->cb.dlen);
                                FREE_AND_NULL(cmdp->cb.data);
                                if (n != (int)cmdp->cb.dlen)
                                        return RESP_BAD;
                        } else if (cmdp->cb.cont) {
                                if (cmdp->cb.cont(ctx, cmd))
                                        return RESP_BAD;
                        } else {
                                fprintf(stderr, "IMAP error: unexpected command continuation request\n");
                                return RESP_BAD;
                        }
                        if (socket_write(&imap->buf.sock, "\r\n", 2) != 2)
                                return RESP_BAD;
                        if (!cmdp->cb.cont)
                                imap->literal_pending = 0;
                        if (!tcmd)
                                return DRV_OK;
                } else {
                        tag = atoi(arg);
                        for (pcmdp = &imap->in_progress; (cmdp = *pcmdp); pcmdp = &cmdp->next)
                                if (cmdp->tag == tag)
                                        goto gottag;
                        fprintf(stderr, "IMAP error: unexpected tag %s\n", arg);
                        return RESP_BAD;
                gottag:
                        if (!(*pcmdp = cmdp->next))
                                imap->in_progress_append = pcmdp;
                        imap->num_in_progress--;
                        if (cmdp->cb.cont || cmdp->cb.data)
                                imap->literal_pending = 0;
                        arg = next_arg(&cmd);
                        if (!arg)
                                arg = "";
                        if (!strcmp("OK", arg))
                                resp = DRV_OK;
                        else {
                                if (!strcmp("NO", arg))
                                        resp = RESP_NO;
                                else /*if (!strcmp("BAD", arg))*/
                                        resp = RESP_BAD;
                                fprintf(stderr, "IMAP command '%s' returned response (%s) - %s\n",
                                        !starts_with(cmdp->cmd, "LOGIN") ?
                                                        cmdp->cmd : "LOGIN <user> <pass>",
                                                        arg, cmd ? cmd : "");
                        }
                        if ((resp2 = parse_response_code(ctx, &cmdp->cb, cmd)) > resp)
                                resp = resp2;
                        free(cmdp->cb.data);
                        free(cmdp->cmd);
                        free(cmdp);
                        if (!tcmd || tcmd == cmdp)
                                return resp;
                }
        }
        /* not reached */
}

static void imap_close_server(struct imap_store *ictx)
{
        struct imap *imap = ictx->imap;

        if (imap->buf.sock.fd[0] != -1) {
                imap_exec(ictx, NULL, "LOGOUT");
                socket_shutdown(&imap->buf.sock);
        }
        free(imap);
}

static void imap_close_store(struct imap_store *ctx)
{
        imap_close_server(ctx);
        free(ctx);
}

#ifndef NO_OPENSSL

/*
 * hexchar() and cram() functions are based on the code from the isync
 * project (https://isync.sourceforge.io/).
 */
static char hexchar(unsigned int b)
{
        return b < 10 ? '0' + b : 'a' + (b - 10);
}

#define ENCODED_SIZE(n) (4 * DIV_ROUND_UP((n), 3))
static char *cram(const char *challenge_64, const char *user, const char *pass)
{
        int i, resp_len, encoded_len, decoded_len;
        unsigned char hash[16];
        char hex[33];
        char *response, *response_64, *challenge;

        /*
         * length of challenge_64 (i.e. base-64 encoded string) is a good
         * enough upper bound for challenge (decoded result).
         */
        encoded_len = strlen(challenge_64);
        challenge = xmalloc(encoded_len);
        decoded_len = EVP_DecodeBlock((unsigned char *)challenge,
                                      (unsigned char *)challenge_64, encoded_len);
        if (decoded_len < 0)
                die("invalid challenge %s", challenge_64);
        if (!HMAC(EVP_md5(), pass, strlen(pass), (unsigned char *)challenge, decoded_len, hash, NULL))
                die("HMAC error");

        hex[32] = 0;
        for (i = 0; i < 16; i++) {
                hex[2 * i] = hexchar((hash[i] >> 4) & 0xf);
                hex[2 * i + 1] = hexchar(hash[i] & 0xf);
        }

        /* response: "<user> <digest in hex>" */
        response = xstrfmt("%s %s", user, hex);
        resp_len = strlen(response);

        response_64 = xmallocz(ENCODED_SIZE(resp_len));
        encoded_len = EVP_EncodeBlock((unsigned char *)response_64,
                                      (unsigned char *)response, resp_len);
        if (encoded_len < 0)
                die("EVP_EncodeBlock error");
        return (char *)response_64;
}

#else

static char *cram(const char *challenge_64 UNUSED,
                  const char *user UNUSED,
                  const char *pass UNUSED)
{
        die("If you want to use CRAM-MD5 authenticate method, "
            "you have to build git-imap-send with OpenSSL library.");
}

#endif

static int auth_cram_md5(struct imap_store *ctx, const char *prompt)
{
        int ret;
        char *response;

        response = cram(prompt, server.user, server.pass);

        ret = socket_write(&ctx->imap->buf.sock, response, strlen(response));
        if (ret != strlen(response))
                return error("IMAP error: sending response failed");

        free(response);

        return 0;
}

static void server_fill_credential(struct imap_server_conf *srvc, struct credential *cred)
{
        if (srvc->user && srvc->pass)
                return;

        cred->protocol = xstrdup(srvc->use_ssl ? "imaps" : "imap");
        cred->host = xstrdup(srvc->host);

        cred->username = xstrdup_or_null(srvc->user);
        cred->password = xstrdup_or_null(srvc->pass);

        credential_fill(cred);

        if (!srvc->user)
                srvc->user = xstrdup(cred->username);
        if (!srvc->pass)
                srvc->pass = xstrdup(cred->password);
}

static struct imap_store *imap_open_store(struct imap_server_conf *srvc, const char *folder)
{
        struct credential cred = CREDENTIAL_INIT;
        struct imap_store *ctx;
        struct imap *imap;
        char *arg, *rsp;
        int s = -1, preauth;

        CALLOC_ARRAY(ctx, 1);

        ctx->imap = CALLOC_ARRAY(imap, 1);
        imap->buf.sock.fd[0] = imap->buf.sock.fd[1] = -1;
        imap->in_progress_append = &imap->in_progress;

        /* open connection to IMAP server */

        if (srvc->tunnel) {
                struct child_process tunnel = CHILD_PROCESS_INIT;

                imap_info("Starting tunnel '%s'... ", srvc->tunnel);

                strvec_push(&tunnel.args, srvc->tunnel);
                tunnel.use_shell = 1;
                tunnel.in = -1;
                tunnel.out = -1;
                if (start_command(&tunnel))
                        die("cannot start proxy %s", srvc->tunnel);

                imap->buf.sock.fd[0] = tunnel.out;
                imap->buf.sock.fd[1] = tunnel.in;

                imap_info("ok\n");
        } else {
#ifndef NO_IPV6
                struct addrinfo hints, *ai0, *ai;
                int gai;
                char portstr[6];

                xsnprintf(portstr, sizeof(portstr), "%d", srvc->port);

                memset(&hints, 0, sizeof(hints));
                hints.ai_socktype = SOCK_STREAM;
                hints.ai_protocol = IPPROTO_TCP;

                imap_info("Resolving %s... ", srvc->host);
                gai = getaddrinfo(srvc->host, portstr, &hints, &ai);
                if (gai) {
                        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(gai));
                        goto bail;
                }
                imap_info("ok\n");

                for (ai0 = ai; ai; ai = ai->ai_next) {
                        char addr[NI_MAXHOST];

                        s = socket(ai->ai_family, ai->ai_socktype,
                                   ai->ai_protocol);
                        if (s < 0)
                                continue;

                        getnameinfo(ai->ai_addr, ai->ai_addrlen, addr,
                                    sizeof(addr), NULL, 0, NI_NUMERICHOST);
                        imap_info("Connecting to [%s]:%s... ", addr, portstr);

                        if (connect(s, ai->ai_addr, ai->ai_addrlen) < 0) {
                                close(s);
                                s = -1;
                                perror("connect");
                                continue;
                        }

                        break;
                }
                freeaddrinfo(ai0);
#else /* NO_IPV6 */
                struct hostent *he;
                struct sockaddr_in addr;

                memset(&addr, 0, sizeof(addr));
                addr.sin_port = htons(srvc->port);
                addr.sin_family = AF_INET;

                imap_info("Resolving %s... ", srvc->host);
                he = gethostbyname(srvc->host);
                if (!he) {
                        perror("gethostbyname");
                        goto bail;
                }
                imap_info("ok\n");

                addr.sin_addr.s_addr = *((int *) he->h_addr_list[0]);

                s = socket(PF_INET, SOCK_STREAM, 0);

                imap_info("Connecting to %s:%hu... ", inet_ntoa(addr.sin_addr), ntohs(addr.sin_port));
                if (connect(s, (struct sockaddr *)&addr, sizeof(addr))) {
                        close(s);
                        s = -1;
                        perror("connect");
                }
#endif
                if (s < 0) {
                        fputs("Error: unable to connect to server.\n", stderr);
                        goto bail;
                }

                imap->buf.sock.fd[0] = s;
                imap->buf.sock.fd[1] = dup(s);

                if (srvc->use_ssl &&
                    ssl_socket_connect(&imap->buf.sock, 0, srvc->ssl_verify)) {
                        close(s);
                        goto bail;
                }
                imap_info("ok\n");
        }

        /* read the greeting string */
        if (buffer_gets(&imap->buf, &rsp)) {
                fprintf(stderr, "IMAP error: no greeting response\n");
                goto bail;
        }
        arg = next_arg(&rsp);
        if (!arg || *arg != '*' || (arg = next_arg(&rsp)) == NULL) {
                fprintf(stderr, "IMAP error: invalid greeting response\n");
                goto bail;
        }
        preauth = 0;
        if (!strcmp("PREAUTH", arg))
                preauth = 1;
        else if (strcmp("OK", arg) != 0) {
                fprintf(stderr, "IMAP error: unknown greeting response\n");
                goto bail;
        }
        parse_response_code(ctx, NULL, rsp);
        if (!imap->caps && imap_exec(ctx, NULL, "CAPABILITY") != RESP_OK)
                goto bail;

        if (!preauth) {
#ifndef NO_OPENSSL
                if (!srvc->use_ssl && CAP(STARTTLS)) {
                        if (imap_exec(ctx, NULL, "STARTTLS") != RESP_OK)
                                goto bail;
                        if (ssl_socket_connect(&imap->buf.sock, 1,
                                               srvc->ssl_verify))
                                goto bail;
                        /* capabilities may have changed, so get the new capabilities */
                        if (imap_exec(ctx, NULL, "CAPABILITY") != RESP_OK)
                                goto bail;
                }
#endif
                imap_info("Logging in...\n");
                server_fill_credential(srvc, &cred);

                if (srvc->auth_method) {
                        struct imap_cmd_cb cb;

                        if (!strcmp(srvc->auth_method, "CRAM-MD5")) {
                                if (!CAP(AUTH_CRAM_MD5)) {
                                        fprintf(stderr, "You specified "
                                                "CRAM-MD5 as authentication method, "
                                                "but %s doesn't support it.\n", srvc->host);
                                        goto bail;
                                }
                                /* CRAM-MD5 */

                                memset(&cb, 0, sizeof(cb));
                                cb.cont = auth_cram_md5;
                                if (imap_exec(ctx, &cb, "AUTHENTICATE CRAM-MD5") != RESP_OK) {
                                        fprintf(stderr, "IMAP error: AUTHENTICATE CRAM-MD5 failed\n");
                                        goto bail;
                                }
                        } else {
                                fprintf(stderr, "Unknown authentication method:%s\n", srvc->host);
                                goto bail;
                        }
                } else {
                        if (CAP(NOLOGIN)) {
                                fprintf(stderr, "Skipping account %s@%s, server forbids LOGIN\n",
                                        srvc->user, srvc->host);
                                goto bail;
                        }
                        if (!imap->buf.sock.ssl)
                                imap_warn("*** IMAP Warning *** Password is being "
                                          "sent in the clear\n");
                        if (imap_exec(ctx, NULL, "LOGIN \"%s\" \"%s\"", srvc->user, srvc->pass) != RESP_OK) {
                                fprintf(stderr, "IMAP error: LOGIN failed\n");
                                goto bail;
                        }
                }
        } /* !preauth */

        if (cred.username)
                credential_approve(&cred);
        credential_clear(&cred);

        /* check the target mailbox exists */
        ctx->name = folder;
        switch (imap_exec(ctx, NULL, "EXAMINE \"%s\"", ctx->name)) {
        case RESP_OK:
                /* ok */
                break;
        case RESP_BAD:
                fprintf(stderr, "IMAP error: could not check mailbox\n");
                goto out;
        case RESP_NO:
                if (imap_exec(ctx, NULL, "CREATE \"%s\"", ctx->name) == RESP_OK) {
                        imap_info("Created missing mailbox\n");
                } else {
                        fprintf(stderr, "IMAP error: could not create missing mailbox\n");
                        goto out;
                }
                break;
        }

        ctx->prefix = "";
        return ctx;

bail:
        if (cred.username)
                credential_reject(&cred);
        credential_clear(&cred);

 out:
        imap_close_store(ctx);
        return NULL;
}

/*
 * Insert CR characters as necessary in *msg to ensure that every LF
 * character in *msg is preceded by a CR.
 */
static void lf_to_crlf(struct strbuf *msg)
{
        char *new_msg;
        size_t i, j;
        char lastc;

        /* First pass: tally, in j, the size of the new_msg string: */
        for (i = j = 0, lastc = '\0'; i < msg->len; i++) {
                if (msg->buf[i] == '\n' && lastc != '\r')
                        j++; /* a CR will need to be added here */
                lastc = msg->buf[i];
                j++;
        }

        new_msg = xmallocz(j);

        /*
         * Second pass: write the new_msg string.  Note that this loop is
         * otherwise identical to the first pass.
         */
        for (i = j = 0, lastc = '\0'; i < msg->len; i++) {
                if (msg->buf[i] == '\n' && lastc != '\r')
                        new_msg[j++] = '\r';
                lastc = new_msg[j++] = msg->buf[i];
        }
        strbuf_attach(msg, new_msg, j, j + 1);
}

/*
 * Store msg to IMAP.  Also detach and free the data from msg->data,
 * leaving msg->data empty.
 */
static int imap_store_msg(struct imap_store *ctx, struct strbuf *msg)
{
        struct imap *imap = ctx->imap;
        struct imap_cmd_cb cb;
        const char *prefix, *box;
        int ret;

        lf_to_crlf(msg);
        memset(&cb, 0, sizeof(cb));

        cb.dlen = msg->len;
        cb.data = strbuf_detach(msg, NULL);

        box = ctx->name;
        prefix = !strcmp(box, "INBOX") ? "" : ctx->prefix;
        ret = imap_exec_m(ctx, &cb, "APPEND \"%s%s\" ", prefix, box);
        imap->caps = imap->rcaps;
        if (ret != DRV_OK)
                return ret;

        return DRV_OK;
}

static void wrap_in_html(struct strbuf *msg)
{
        struct strbuf buf = STRBUF_INIT;
        static char *content_type = "Content-Type: text/html;\n";
        static char *pre_open = "<pre>\n";
        static char *pre_close = "</pre>\n";
        const char *body = strstr(msg->buf, "\n\n");

        if (!body)
                return; /* Headers but no body; no wrapping needed */

        body += 2;

        strbuf_add(&buf, msg->buf, body - msg->buf - 1);
        strbuf_addstr(&buf, content_type);
        strbuf_addch(&buf, '\n');
        strbuf_addstr(&buf, pre_open);
        strbuf_addstr_xml_quoted(&buf, body);
        strbuf_addstr(&buf, pre_close);

        strbuf_release(msg);
        *msg = buf;
}

static int count_messages(struct strbuf *all_msgs)
{
        int count = 0;
        char *p = all_msgs->buf;

        while (1) {
                if (starts_with(p, "From ")) {
                        p = strstr(p+5, "\nFrom: ");
                        if (!p) break;
                        p = strstr(p+7, "\nDate: ");
                        if (!p) break;
                        p = strstr(p+7, "\nSubject: ");
                        if (!p) break;
                        p += 10;
                        count++;
                }
                p = strstr(p+5, "\nFrom ");
                if (!p)
                        break;
                p++;
        }
        return count;
}

/*
 * Copy the next message from all_msgs, starting at offset *ofs, to
 * msg.  Update *ofs to the start of the following message.  Return
 * true iff a message was successfully copied.
 */
static int split_msg(struct strbuf *all_msgs, struct strbuf *msg, int *ofs)
{
        char *p, *data;
        size_t len;

        if (*ofs >= all_msgs->len)
                return 0;

        data = &all_msgs->buf[*ofs];
        len = all_msgs->len - *ofs;

        if (len < 5 || !starts_with(data, "From "))
                return 0;

        p = strchr(data, '\n');
        if (p) {
                p++;
                len -= p - data;
                *ofs += p - data;
                data = p;
        }

        p = strstr(data, "\nFrom ");
        if (p)
                len = &p[1] - data;

        strbuf_add(msg, data, len);
        *ofs += len;
        return 1;
}

static int git_imap_config(const char *var, const char *val,
                           const struct config_context *ctx, void *cb)
{

        if (!strcmp("imap.sslverify", var))
                server.ssl_verify = git_config_bool(var, val);
        else if (!strcmp("imap.preformattedhtml", var))
                server.use_html = git_config_bool(var, val);
        else if (!strcmp("imap.folder", var))
                return git_config_string(&server.folder, var, val);
        else if (!strcmp("imap.user", var))
                return git_config_string(&server.user, var, val);
        else if (!strcmp("imap.pass", var))
                return git_config_string(&server.pass, var, val);
        else if (!strcmp("imap.tunnel", var))
                return git_config_string(&server.tunnel, var, val);
        else if (!strcmp("imap.authmethod", var))
                return git_config_string(&server.auth_method, var, val);
        else if (!strcmp("imap.port", var))
                server.port = git_config_int(var, val, ctx->kvi);
        else if (!strcmp("imap.host", var)) {
                if (!val) {
                        return config_error_nonbool(var);
                } else {
                        if (starts_with(val, "imap:"))
                                val += 5;
                        else if (starts_with(val, "imaps:")) {
                                val += 6;
                                server.use_ssl = 1;
                        }
                        if (starts_with(val, "//"))
                                val += 2;
                        server.host = xstrdup(val);
                }
        } else
                return git_default_config(var, val, ctx, cb);

        return 0;
}

static int append_msgs_to_imap(struct imap_server_conf *server,
                               struct strbuf* all_msgs, int total)
{
        struct strbuf msg = STRBUF_INIT;
        struct imap_store *ctx = NULL;
        int ofs = 0;
        int r;
        int n = 0;

        ctx = imap_open_store(server, server->folder);
        if (!ctx) {
                fprintf(stderr, "failed to open store\n");
                return 1;
        }
        ctx->name = server->folder;

        fprintf(stderr, "sending %d message%s\n", total, (total != 1) ? "s" : "");
        while (1) {
                unsigned percent = n * 100 / total;

                fprintf(stderr, "%4u%% (%d/%d) done\r", percent, n, total);

                if (!split_msg(all_msgs, &msg, &ofs))
                        break;
                if (server->use_html)
                        wrap_in_html(&msg);
                r = imap_store_msg(ctx, &msg);
                if (r != DRV_OK)
                        break;
                n++;
        }
        fprintf(stderr, "\n");

        imap_close_store(ctx);

        return 0;
}

#ifdef USE_CURL_FOR_IMAP_SEND
static CURL *setup_curl(struct imap_server_conf *srvc, struct credential *cred)
{
        CURL *curl;
        struct strbuf path = STRBUF_INIT;
        char *uri_encoded_folder;

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

        curl = curl_easy_init();

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

        server_fill_credential(srvc, cred);
        curl_easy_setopt(curl, CURLOPT_USERNAME, srvc->user);
        curl_easy_setopt(curl, CURLOPT_PASSWORD, srvc->pass);

        strbuf_addstr(&path, srvc->use_ssl ? "imaps://" : "imap://");
        strbuf_addstr(&path, srvc->host);
        if (!path.len || path.buf[path.len - 1] != '/')
                strbuf_addch(&path, '/');

        uri_encoded_folder = curl_easy_escape(curl, srvc->folder, 0);
        if (!uri_encoded_folder)
                die("failed to encode server folder");
        strbuf_addstr(&path, uri_encoded_folder);
        curl_free(uri_encoded_folder);

        curl_easy_setopt(curl, CURLOPT_URL, path.buf);
        strbuf_release(&path);
        curl_easy_setopt(curl, CURLOPT_PORT, srvc->port);

        if (srvc->auth_method) {
#ifndef GIT_CURL_HAVE_CURLOPT_LOGIN_OPTIONS
                warning("No LOGIN_OPTIONS support in this cURL version");
#else
                struct strbuf auth = STRBUF_INIT;
                strbuf_addstr(&auth, "AUTH=");
                strbuf_addstr(&auth, srvc->auth_method);
                curl_easy_setopt(curl, CURLOPT_LOGIN_OPTIONS, auth.buf);
                strbuf_release(&auth);
#endif
        }

        if (!srvc->use_ssl)
                curl_easy_setopt(curl, CURLOPT_USE_SSL, (long)CURLUSESSL_TRY);

        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, srvc->ssl_verify);
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, srvc->ssl_verify);

        curl_easy_setopt(curl, CURLOPT_READFUNCTION, fread_buffer);

        curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

        if (0 < verbosity || getenv("GIT_CURL_VERBOSE"))
                http_trace_curl_no_data();
        setup_curl_trace(curl);

        return curl;
}

static int curl_append_msgs_to_imap(struct imap_server_conf *server,
                                    struct strbuf* all_msgs, int total)
{
        int ofs = 0;
        int n = 0;
        struct buffer msgbuf = { STRBUF_INIT, 0 };
        CURL *curl;
        CURLcode res = CURLE_OK;
        struct credential cred = CREDENTIAL_INIT;

        curl = setup_curl(server, &cred);
        curl_easy_setopt(curl, CURLOPT_READDATA, &msgbuf);

        fprintf(stderr, "sending %d message%s\n", total, (total != 1) ? "s" : "");
        while (1) {
                unsigned percent = n * 100 / total;
                int prev_len;

                fprintf(stderr, "%4u%% (%d/%d) done\r", percent, n, total);

                prev_len = msgbuf.buf.len;
                if (!split_msg(all_msgs, &msgbuf.buf, &ofs))
                        break;
                if (server->use_html)
                        wrap_in_html(&msgbuf.buf);
                lf_to_crlf(&msgbuf.buf);

                curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,
                                 (curl_off_t)(msgbuf.buf.len-prev_len));

                res = curl_easy_perform(curl);

                if(res != CURLE_OK) {
                        fprintf(stderr, "curl_easy_perform() failed: %s\n",
                                        curl_easy_strerror(res));
                        break;
                }

                n++;
        }
        fprintf(stderr, "\n");

        curl_easy_cleanup(curl);
        curl_global_cleanup();

        if (cred.username) {
                if (res == CURLE_OK)
                        credential_approve(&cred);
                else if (res == CURLE_LOGIN_DENIED)
                        credential_reject(&cred);
        }

        credential_clear(&cred);

        return res != CURLE_OK;
}
#endif

int cmd_main(int argc, const char **argv)
{
        struct strbuf all_msgs = STRBUF_INIT;
        int total;
        int nongit_ok;

        setup_git_directory_gently(&nongit_ok);
        git_config(git_imap_config, NULL);

        argc = parse_options(argc, (const char **)argv, "", imap_send_options, imap_send_usage, 0);

        if (argc)
                usage_with_options(imap_send_usage, imap_send_options);

#ifndef USE_CURL_FOR_IMAP_SEND
        if (use_curl) {
                warning("--curl not supported in this build");
                use_curl = 0;
        }
#elif defined(NO_OPENSSL)
        if (!use_curl) {
                warning("--no-curl not supported in this build");
                use_curl = 1;
        }
#endif

        if (!server.port)
                server.port = server.use_ssl ? 993 : 143;

        if (!server.folder) {
                fprintf(stderr, "no imap store specified\n");
                return 1;
        }
        if (!server.host) {
                if (!server.tunnel) {
                        fprintf(stderr, "no imap host specified\n");
                        return 1;
                }
                server.host = "tunnel";
        }

        /* read the messages */
        if (strbuf_read(&all_msgs, 0, 0) < 0) {
                error_errno(_("could not read from stdin"));
                return 1;
        }

        if (all_msgs.len == 0) {
                fprintf(stderr, "nothing to send\n");
                return 1;
        }

        total = count_messages(&all_msgs);
        if (!total) {
                fprintf(stderr, "no messages to send\n");
                return 1;
        }

        /* write it to the imap server */

        if (server.tunnel)
                return append_msgs_to_imap(&server, &all_msgs, total);

#ifdef USE_CURL_FOR_IMAP_SEND
        if (use_curl)
                return curl_append_msgs_to_imap(&server, &all_msgs, total);
#endif

        return append_msgs_to_imap(&server, &all_msgs, total);
}