credential-cache--daemon.c

   1 #include "cache.h"
   2 #include "credential.h"
   3 #include "unix-socket.h"
   4 #include "sigchain.h"
   5 #include "parse-options.h"
   6
   7 static const char *socket_path;
   8
   9 static void cleanup_socket(void)
  10 {
  11         if (socket_path)
  12                 unlink(socket_path);
  13 }
  14
  15 static void cleanup_socket_on_signal(int sig)
  16 {
  17         cleanup_socket();
  18         sigchain_pop(sig);
  19         raise(sig);
  20 }
  21
  22 struct credential_cache_entry {
  23         struct credential item;
  24         unsigned long expiration;
  25 };
  26 static struct credential_cache_entry *entries;
  27 static int entries_nr;
  28 static int entries_alloc;
  29
  30 static void cache_credential(struct credential *c, int timeout)
  31 {
  32         struct credential_cache_entry *e;
  33
  34         ALLOC_GROW(entries, entries_nr + 1, entries_alloc);
  35         e = &entries[entries_nr++];
  36
  37         /* take ownership of pointers */
  38         memcpy(&e->item, c, sizeof(*c));
  39         memset(c, 0, sizeof(*c));
  40         e->expiration = time(NULL) + timeout;
  41 }
  42
  43 static struct credential_cache_entry *lookup_credential(const struct credential *c)
  44 {
  45         int i;
  46         for (i = 0; i < entries_nr; i++) {
  47                 struct credential *e = &entries[i].item;
  48                 if (credential_match(c, e))
  49                         return &entries[i];
  50         }
  51         return NULL;
  52 }
  53
  54 static void remove_credential(const struct credential *c)
  55 {
  56         struct credential_cache_entry *e;
  57
  58         e = lookup_credential(c);
  59         if (e)
  60                 e->expiration = 0;
  61 }
  62
  63 static int check_expirations(void)
  64 {
  65         static unsigned long wait_for_entry_until;
  66         int i = 0;
  67         unsigned long now = time(NULL);
  68         unsigned long next = (unsigned long)-1;
  69
  70         /*
  71          * Initially give the client 30 seconds to actually contact us
  72          * and store a credential before we decide there's no point in
  73          * keeping the daemon around.
  74          */
  75         if (!wait_for_entry_until)
  76                 wait_for_entry_until = now + 30;
  77
  78         while (i < entries_nr) {
  79                 if (entries[i].expiration <= now) {
  80                         entries_nr--;
  81                         credential_clear(&entries[i].item);
  82                         if (i != entries_nr)
  83                                 memcpy(&entries[i], &entries[entries_nr], sizeof(*entries));
  84                         /*
  85                          * Stick around 30 seconds in case a new credential
  86                          * shows up (e.g., because we just removed a failed
  87                          * one, and we will soon get the correct one).
  88                          */
  89                         wait_for_entry_until = now + 30;
  90                 }
  91                 else {
  92                         if (entries[i].expiration < next)
  93                                 next = entries[i].expiration;
  94                         i++;
  95                 }
  96         }
  97
  98         if (!entries_nr) {
  99                 if (wait_for_entry_until <= now)
 100                         return 0;
 101                 next = wait_for_entry_until;
 102         }
 103
 104         return next - now;
 105 }
 106
 107 static int read_request(FILE *fh, struct credential *c,
 108                         struct strbuf *action, int *timeout) {
 109         static struct strbuf item = STRBUF_INIT;
 110         const char *p;
 111
 112         strbuf_getline(&item, fh, '\n');
 113         if (!skip_prefix(item.buf, "action=", &p))
 114                 return error("client sent bogus action line: %s", item.buf);
 115         strbuf_addstr(action, p);
 116
 117         strbuf_getline(&item, fh, '\n');
 118         if (!skip_prefix(item.buf, "timeout=", &p))
 119                 return error("client sent bogus timeout line: %s", item.buf);
 120         *timeout = atoi(p);
 121
 122         if (credential_read(c, fh) < 0)
 123                 return -1;
 124         return 0;
 125 }
 126
 127 static void serve_one_client(FILE *in, FILE *out)
 128 {
 129         struct credential c = CREDENTIAL_INIT;
 130         struct strbuf action = STRBUF_INIT;
 131         int timeout = -1;
 132
 133         if (read_request(in, &c, &action, &timeout) < 0)
 134                 /* ignore error */ ;
 135         else if (!strcmp(action.buf, "get")) {
 136                 struct credential_cache_entry *e = lookup_credential(&c);
 137                 if (e) {
 138                         fprintf(out, "username=%s\n", e->item.username);
 139                         fprintf(out, "password=%s\n", e->item.password);
 140                 }
 141         }
 142         else if (!strcmp(action.buf, "exit"))
 143                 exit(0);
 144         else if (!strcmp(action.buf, "erase"))
 145                 remove_credential(&c);
 146         else if (!strcmp(action.buf, "store")) {
 147                 if (timeout < 0)
 148                         warning("cache client didn't specify a timeout");
 149                 else if (!c.username || !c.password)
 150                         warning("cache client gave us a partial credential");
 151                 else {
 152                         remove_credential(&c);
 153                         cache_credential(&c, timeout);
 154                 }
 155         }
 156         else
 157                 warning("cache client sent unknown action: %s", action.buf);
 158
 159         credential_clear(&c);
 160         strbuf_release(&action);
 161 }
 162
 163 static int serve_cache_loop(int fd)
 164 {
 165         struct pollfd pfd;
 166         unsigned long wakeup;
 167
 168         wakeup = check_expirations();
 169         if (!wakeup)
 170                 return 0;
 171
 172         pfd.fd = fd;
 173         pfd.events = POLLIN;
 174         if (poll(&pfd, 1, 1000 * wakeup) < 0) {
 175                 if (errno != EINTR)
 176                         die_errno("poll failed");
 177                 return 1;
 178         }
 179
 180         if (pfd.revents & POLLIN) {
 181                 int client, client2;
 182                 FILE *in, *out;
 183
 184                 client = accept(fd, NULL, NULL);
 185                 if (client < 0) {
 186                         warning("accept failed: %s", strerror(errno));
 187                         return 1;
 188                 }
 189                 client2 = dup(client);
 190                 if (client2 < 0) {
 191                         warning("dup failed: %s", strerror(errno));
 192                         close(client);
 193                         return 1;
 194                 }
 195
 196                 in = xfdopen(client, "r");
 197                 out = xfdopen(client2, "w");
 198                 serve_one_client(in, out);
 199                 fclose(in);
 200                 fclose(out);
 201         }
 202         return 1;
 203 }
 204
 205 static void serve_cache(const char *socket_path, int debug)
 206 {
 207         int fd;
 208
 209         fd = unix_stream_listen(socket_path);
 210         if (fd < 0)
 211                 die_errno("unable to bind to '%s'", socket_path);
 212
 213         printf("ok\n");
 214         fclose(stdout);
 215         if (!debug) {
 216                 if (!freopen("/dev/null", "w", stderr))
 217                         die_errno("unable to point stderr to /dev/null");
 218         }
 219
 220         while (serve_cache_loop(fd))
 221                 ; /* nothing */
 222
 223         close(fd);
 224         unlink(socket_path);
 225 }
 226
 227 static const char permissions_advice[] =
 228 "The permissions on your socket directory are too loose; other\n"
 229 "users may be able to read your cached credentials. Consider running:\n"
 230 "\n"
 231 "       chmod 0700 %s";
 232 static void check_socket_directory(const char *path)
 233 {
 234         struct stat st;
 235         char *path_copy = xstrdup(path);
 236         char *dir = dirname(path_copy);
 237
 238         if (!stat(dir, &st)) {
 239                 if (st.st_mode & 077)
 240                         die(permissions_advice, dir);
 241                 free(path_copy);
 242                 return;
 243         }
 244
 245         /*
 246          * We must be sure to create the directory with the correct mode,
 247          * not just chmod it after the fact; otherwise, there is a race
 248          * condition in which somebody can chdir to it, sleep, then try to open
 249          * our protected socket.
 250          */
 251         if (safe_create_leading_directories_const(dir) < 0)
 252                 die_errno("unable to create directories for '%s'", dir);
 253         if (mkdir(dir, 0700) < 0)
 254                 die_errno("unable to mkdir '%s'", dir);
 255         free(path_copy);
 256 }
 257
 258 int main(int argc, const char **argv)
 259 {
 260         static const char *usage[] = {
 261                 "git-credential-cache--daemon [opts] <socket_path>",
 262                 NULL
 263         };
 264         int debug = 0;
 265         const struct option options[] = {
 266                 OPT_BOOL(0, "debug", &debug,
 267                          N_("print debugging messages to stderr")),
 268                 OPT_END()
 269         };
 270
 271         argc = parse_options(argc, argv, NULL, options, usage, 0);
 272         socket_path = argv[0];
 273
 274         if (!socket_path)
 275                 usage_with_options(usage, options);
 276         check_socket_directory(socket_path);
 277
 278         atexit(cleanup_socket);
 279         sigchain_push_common(cleanup_socket_on_signal);
 280
 281         serve_cache(socket_path, debug);
 282
 283         return 0;
 284 }