Merge branch 'tb/object-access-overflow-protection'

[git/debian.git] / serve.c

#include "git-compat-util.h"
#include "repository.h"
#include "config.h"
#include "hash-ll.h"
#include "pkt-line.h"
#include "version.h"
#include "ls-refs.h"
#include "protocol-caps.h"
#include "serve.h"
#include "upload-pack.h"
#include "bundle-uri.h"
#include "trace2.h"

static int advertise_sid = -1;
static int client_hash_algo = GIT_HASH_SHA1;

static int always_advertise(struct repository *r UNUSED,
                            struct strbuf *value UNUSED)
{
        return 1;
}

static int agent_advertise(struct repository *r UNUSED,
                           struct strbuf *value)
{
        if (value)
                strbuf_addstr(value, git_user_agent_sanitized());
        return 1;
}

static int object_format_advertise(struct repository *r,
                                   struct strbuf *value)
{
        if (value)
                strbuf_addstr(value, r->hash_algo->name);
        return 1;
}

static void object_format_receive(struct repository *r UNUSED,
                                  const char *algo_name)
{
        if (!algo_name)
                die("object-format capability requires an argument");

        client_hash_algo = hash_algo_by_name(algo_name);
        if (client_hash_algo == GIT_HASH_UNKNOWN)
                die("unknown object format '%s'", algo_name);
}

static int session_id_advertise(struct repository *r, struct strbuf *value)
{
        if (advertise_sid == -1 &&
            repo_config_get_bool(r, "transfer.advertisesid", &advertise_sid))
                advertise_sid = 0;
        if (!advertise_sid)
                return 0;
        if (value)
                strbuf_addstr(value, trace2_session_id());
        return 1;
}

static void session_id_receive(struct repository *r UNUSED,
                               const char *client_sid)
{
        if (!client_sid)
                client_sid = "";
        trace2_data_string("transfer", NULL, "client-sid", client_sid);
}

struct protocol_capability {
        /*
         * The name of the capability.  The server uses this name when
         * advertising this capability, and the client uses this name to
         * specify this capability.
         */
        const char *name;

        /*
         * Function queried to see if a capability should be advertised.
         * Optionally a value can be specified by adding it to 'value'.
         * If a value is added to 'value', the server will advertise this
         * capability as "<name>=<value>" instead of "<name>".
         */
        int (*advertise)(struct repository *r, struct strbuf *value);

        /*
         * Function called when a client requests the capability as a command.
         * Will be provided a struct packet_reader 'request' which it should
         * use to read the command specific part of the request.  Every command
         * MUST read until a flush packet is seen before sending a response.
         *
         * This field should be NULL for capabilities which are not commands.
         */
        int (*command)(struct repository *r, struct packet_reader *request);

        /*
         * Function called when a client requests the capability as a
         * non-command. This may be NULL if the capability does nothing.
         *
         * For a capability of the form "foo=bar", the value string points to
         * the content after the "=" (i.e., "bar"). For simple capabilities
         * (just "foo"), it is NULL.
         */
        void (*receive)(struct repository *r, const char *value);
};

static struct protocol_capability capabilities[] = {
        {
                .name = "agent",
                .advertise = agent_advertise,
        },
        {
                .name = "ls-refs",
                .advertise = ls_refs_advertise,
                .command = ls_refs,
        },
        {
                .name = "fetch",
                .advertise = upload_pack_advertise,
                .command = upload_pack_v2,
        },
        {
                .name = "server-option",
                .advertise = always_advertise,
        },
        {
                .name = "object-format",
                .advertise = object_format_advertise,
                .receive = object_format_receive,
        },
        {
                .name = "session-id",
                .advertise = session_id_advertise,
                .receive = session_id_receive,
        },
        {
                .name = "object-info",
                .advertise = always_advertise,
                .command = cap_object_info,
        },
        {
                .name = "bundle-uri",
                .advertise = bundle_uri_advertise,
                .command = bundle_uri_command,
        },
};

void protocol_v2_advertise_capabilities(void)
{
        struct strbuf capability = STRBUF_INIT;
        struct strbuf value = STRBUF_INIT;
        int i;

        /* serve by default supports v2 */
        packet_write_fmt(1, "version 2\n");

        for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
                struct protocol_capability *c = &capabilities[i];

                if (c->advertise(the_repository, &value)) {
                        strbuf_addstr(&capability, c->name);

                        if (value.len) {
                                strbuf_addch(&capability, '=');
                                strbuf_addbuf(&capability, &value);
                        }

                        strbuf_addch(&capability, '\n');
                        packet_write(1, capability.buf, capability.len);
                }

                strbuf_reset(&capability);
                strbuf_reset(&value);
        }

        packet_flush(1);
        strbuf_release(&capability);
        strbuf_release(&value);
}

static struct protocol_capability *get_capability(const char *key, const char **value)
{
        int i;

        if (!key)
                return NULL;

        for (i = 0; i < ARRAY_SIZE(capabilities); i++) {
                struct protocol_capability *c = &capabilities[i];
                const char *out;
                if (!skip_prefix(key, c->name, &out))
                        continue;
                if (!*out) {
                        *value = NULL;
                        return c;
                }
                if (*out++ == '=') {
                        *value = out;
                        return c;
                }
        }

        return NULL;
}

static int receive_client_capability(const char *key)
{
        const char *value;
        const struct protocol_capability *c = get_capability(key, &value);

        if (!c || c->command || !c->advertise(the_repository, NULL))
                return 0;

        if (c->receive)
                c->receive(the_repository, value);
        return 1;
}

static int parse_command(const char *key, struct protocol_capability **command)
{
        const char *out;

        if (skip_prefix(key, "command=", &out)) {
                const char *value;
                struct protocol_capability *cmd = get_capability(out, &value);

                if (*command)
                        die("command '%s' requested after already requesting command '%s'",
                            out, (*command)->name);
                if (!cmd || !cmd->advertise(the_repository, NULL) || !cmd->command || value)
                        die("invalid command '%s'", out);

                *command = cmd;
                return 1;
        }

        return 0;
}

enum request_state {
        PROCESS_REQUEST_KEYS,
        PROCESS_REQUEST_DONE,
};

static int process_request(void)
{
        enum request_state state = PROCESS_REQUEST_KEYS;
        struct packet_reader reader;
        int seen_capability_or_command = 0;
        struct protocol_capability *command = NULL;

        packet_reader_init(&reader, 0, NULL, 0,
                           PACKET_READ_CHOMP_NEWLINE |
                           PACKET_READ_GENTLE_ON_EOF |
                           PACKET_READ_DIE_ON_ERR_PACKET);

        /*
         * Check to see if the client closed their end before sending another
         * request.  If so we can terminate the connection.
         */
        if (packet_reader_peek(&reader) == PACKET_READ_EOF)
                return 1;
        reader.options &= ~PACKET_READ_GENTLE_ON_EOF;

        while (state != PROCESS_REQUEST_DONE) {
                switch (packet_reader_peek(&reader)) {
                case PACKET_READ_EOF:
                        BUG("Should have already died when seeing EOF");
                case PACKET_READ_NORMAL:
                        if (parse_command(reader.line, &command) ||
                            receive_client_capability(reader.line))
                                seen_capability_or_command = 1;
                        else
                                die("unknown capability '%s'", reader.line);

                        /* Consume the peeked line */
                        packet_reader_read(&reader);
                        break;
                case PACKET_READ_FLUSH:
                        /*
                         * If no command and no keys were given then the client
                         * wanted to terminate the connection.
                         */
                        if (!seen_capability_or_command)
                                return 1;

                        /*
                         * The flush packet isn't consume here like it is in
                         * the other parts of this switch statement.  This is
                         * so that the command can read the flush packet and
                         * see the end of the request in the same way it would
                         * if command specific arguments were provided after a
                         * delim packet.
                         */
                        state = PROCESS_REQUEST_DONE;
                        break;
                case PACKET_READ_DELIM:
                        /* Consume the peeked line */
                        packet_reader_read(&reader);

                        state = PROCESS_REQUEST_DONE;
                        break;
                case PACKET_READ_RESPONSE_END:
                        BUG("unexpected response end packet");
                }
        }

        if (!command)
                die("no command requested");

        if (client_hash_algo != hash_algo_by_ptr(the_repository->hash_algo))
                die("mismatched object format: server %s; client %s\n",
                    the_repository->hash_algo->name,
                    hash_algos[client_hash_algo].name);

        command->command(the_repository, &reader);

        return 0;
}

void protocol_v2_serve_loop(int stateless_rpc)
{
        if (!stateless_rpc)
                protocol_v2_advertise_capabilities();

        /*
         * If stateless-rpc was requested then exit after
         * a single request/response exchange
         */
        if (stateless_rpc) {
                process_request();
        } else {
                for (;;)
                        if (process_request())
                                break;
        }
}