root/credential-cache--daemon.c

DEFINITIONS

1. cache_credential
2. lookup_credential
3. remove_credential
4. check_expirations
5. read_request
6. serve_one_client
7. serve_cache_loop
8. serve_cache
9. check_socket_directory
10. main

#include "cache.h"
#include "tempfile.h"
#include "credential.h"
#include "unix-socket.h"
#include "sigchain.h"
#include "parse-options.h"

static struct tempfile socket_file;

struct credential_cache_entry {
        struct credential item;
        unsigned long expiration;
};
static struct credential_cache_entry *entries;
static int entries_nr;
static int entries_alloc;

static void cache_credential(struct credential *c, int timeout)
{
        struct credential_cache_entry *e;

        ALLOC_GROW(entries, entries_nr + 1, entries_alloc);
        e = &entries[entries_nr++];

        /* take ownership of pointers */
        memcpy(&e->item, c, sizeof(*c));
        memset(c, 0, sizeof(*c));
        e->expiration = time(NULL) + timeout;
}

static struct credential_cache_entry *lookup_credential(const struct credential *c)
{
        int i;
        for (i = 0; i < entries_nr; i++) {
                struct credential *e = &entries[i].item;
                if (credential_match(c, e))
                        return &entries[i];
        }
        return NULL;
}

static void remove_credential(const struct credential *c)
{
        struct credential_cache_entry *e;

        e = lookup_credential(c);
        if (e)
                e->expiration = 0;
}

static int check_expirations(void)
{
        static unsigned long wait_for_entry_until;
        int i = 0;
        unsigned long now = time(NULL);
        unsigned long next = (unsigned long)-1;

        /*
         * Initially give the client 30 seconds to actually contact us
         * and store a credential before we decide there's no point in
         * keeping the daemon around.
         */
        if (!wait_for_entry_until)
                wait_for_entry_until = now + 30;

        while (i < entries_nr) {
                if (entries[i].expiration <= now) {
                        entries_nr--;
                        credential_clear(&entries[i].item);
                        if (i != entries_nr)
                                memcpy(&entries[i], &entries[entries_nr], sizeof(*entries));
                        /*
                         * Stick around 30 seconds in case a new credential
                         * shows up (e.g., because we just removed a failed
                         * one, and we will soon get the correct one).
                         */
                        wait_for_entry_until = now + 30;
                }
                else {
                        if (entries[i].expiration < next)
                                next = entries[i].expiration;
                        i++;
                }
        }

        if (!entries_nr) {
                if (wait_for_entry_until <= now)
                        return 0;
                next = wait_for_entry_until;
        }

        return next - now;
}

static int read_request(FILE *fh, struct credential *c,
                        struct strbuf *action, int *timeout) {
        static struct strbuf item = STRBUF_INIT;
        const char *p;

        strbuf_getline(&item, fh, '\n');
        if (!skip_prefix(item.buf, "action=", &p))
                return error("client sent bogus action line: %s", item.buf);
        strbuf_addstr(action, p);

        strbuf_getline(&item, fh, '\n');
        if (!skip_prefix(item.buf, "timeout=", &p))
                return error("client sent bogus timeout line: %s", item.buf);
        *timeout = atoi(p);

        if (credential_read(c, fh) < 0)
                return -1;
        return 0;
}

static void serve_one_client(FILE *in, FILE *out)
{
        struct credential c = CREDENTIAL_INIT;
        struct strbuf action = STRBUF_INIT;
        int timeout = -1;

        if (read_request(in, &c, &action, &timeout) < 0)
                /* ignore error */ ;
        else if (!strcmp(action.buf, "get")) {
                struct credential_cache_entry *e = lookup_credential(&c);
                if (e) {
                        fprintf(out, "username=%s\n", e->item.username);
                        fprintf(out, "password=%s\n", e->item.password);
                }
        }
        else if (!strcmp(action.buf, "exit"))
                exit(0);
        else if (!strcmp(action.buf, "erase"))
                remove_credential(&c);
        else if (!strcmp(action.buf, "store")) {
                if (timeout < 0)
                        warning("cache client didn't specify a timeout");
                else if (!c.username || !c.password)
                        warning("cache client gave us a partial credential");
                else {
                        remove_credential(&c);
                        cache_credential(&c, timeout);
                }
        }
        else
                warning("cache client sent unknown action: %s", action.buf);

        credential_clear(&c);
        strbuf_release(&action);
}

static int serve_cache_loop(int fd)
{
        struct pollfd pfd;
        unsigned long wakeup;

        wakeup = check_expirations();
        if (!wakeup)
                return 0;

        pfd.fd = fd;
        pfd.events = POLLIN;
        if (poll(&pfd, 1, 1000 * wakeup) < 0) {
                if (errno != EINTR)
                        die_errno("poll failed");
                return 1;
        }

        if (pfd.revents & POLLIN) {
                int client, client2;
                FILE *in, *out;

                client = accept(fd, NULL, NULL);
                if (client < 0) {
                        warning("accept failed: %s", strerror(errno));
                        return 1;
                }
                client2 = dup(client);
                if (client2 < 0) {
                        warning("dup failed: %s", strerror(errno));
                        close(client);
                        return 1;
                }

                in = xfdopen(client, "r");
                out = xfdopen(client2, "w");
                serve_one_client(in, out);
                fclose(in);
                fclose(out);
        }
        return 1;
}

static void serve_cache(const char *socket_path, int debug)
{
        int fd;

        fd = unix_stream_listen(socket_path);
        if (fd < 0)
                die_errno("unable to bind to '%s'", socket_path);

        printf("ok\n");
        fclose(stdout);
        if (!debug) {
                if (!freopen("/dev/null", "w", stderr))
                        die_errno("unable to point stderr to /dev/null");
        }

        while (serve_cache_loop(fd))
                ; /* nothing */

        close(fd);
}

static const char permissions_advice[] =
"The permissions on your socket directory are too loose; other\n"
"users may be able to read your cached credentials. Consider running:\n"
"\n"
"       chmod 0700 %s";
static void check_socket_directory(const char *path)
{
        struct stat st;
        char *path_copy = xstrdup(path);
        char *dir = dirname(path_copy);

        if (!stat(dir, &st)) {
                if (st.st_mode & 077)
                        die(permissions_advice, dir);
                free(path_copy);
                return;
        }

        /*
         * We must be sure to create the directory with the correct mode,
         * not just chmod it after the fact; otherwise, there is a race
         * condition in which somebody can chdir to it, sleep, then try to open
         * our protected socket.
         */
        if (safe_create_leading_directories_const(dir) < 0)
                die_errno("unable to create directories for '%s'", dir);
        if (mkdir(dir, 0700) < 0)
                die_errno("unable to mkdir '%s'", dir);
        free(path_copy);
}

int main(int argc, const char **argv)
{
        const char *socket_path;
        static const char *usage[] = {
                "git-credential-cache--daemon [opts] <socket_path>",
                NULL
        };
        int debug = 0;
        const struct option options[] = {
                OPT_BOOL(0, "debug", &debug,
                         N_("print debugging messages to stderr")),
                OPT_END()
        };

        argc = parse_options(argc, argv, NULL, options, usage, 0);
        socket_path = argv[0];

        if (!socket_path)
                usage_with_options(usage, options);

        check_socket_directory(socket_path);
        register_tempfile(&socket_file, socket_path);
        serve_cache(socket_path, debug);
        delete_tempfile(&socket_file);

        return 0;
}