credential-cache--daemon.c

   1 #include "cache.h"
   2 #include "tempfile.h"
   3 #include "credential.h"
   4 #include "unix-socket.h"
   5 #include "parse-options.h"
   6
   7 static struct tempfile socket_file;
   8
   9 struct credential_cache_entry {
  10         struct credential item;
  11         unsigned long expiration;
  12 };
  13 static struct credential_cache_entry *entries;
  14 static int entries_nr;
  15 static int entries_alloc;
  16
  17 static void cache_credential(struct credential *c, int timeout)
  18 {
  19         struct credential_cache_entry *e;
  20
  21         ALLOC_GROW(entries, entries_nr + 1, entries_alloc);
  22         e = &entries[entries_nr++];
  23
  24         /* take ownership of pointers */
  25         memcpy(&e->item, c, sizeof(*c));
  26         memset(c, 0, sizeof(*c));
  27         e->expiration = time(NULL) + timeout;
  28 }
  29
  30 static struct credential_cache_entry *lookup_credential(const struct credential *c)
  31 {
  32         int i;
  33         for (i = 0; i < entries_nr; i++) {
  34                 struct credential *e = &entries[i].item;
  35                 if (credential_match(c, e))
  36                         return &entries[i];
  37         }
  38         return NULL;
  39 }
  40
  41 static void remove_credential(const struct credential *c)
  42 {
  43         struct credential_cache_entry *e;
  44
  45         e = lookup_credential(c);
  46         if (e)
  47                 e->expiration = 0;
  48 }
  49
  50 static int check_expirations(void)
  51 {
  52         static unsigned long wait_for_entry_until;
  53         int i = 0;
  54         unsigned long now = time(NULL);
  55         unsigned long next = (unsigned long)-1;
  56
  57         /*
  58          * Initially give the client 30 seconds to actually contact us
  59          * and store a credential before we decide there's no point in
  60          * keeping the daemon around.
  61          */
  62         if (!wait_for_entry_until)
  63                 wait_for_entry_until = now + 30;
  64
  65         while (i < entries_nr) {
  66                 if (entries[i].expiration <= now) {
  67                         entries_nr--;
  68                         credential_clear(&entries[i].item);
  69                         if (i != entries_nr)
  70                                 memcpy(&entries[i], &entries[entries_nr], sizeof(*entries));
  71                         /*
  72                          * Stick around 30 seconds in case a new credential
  73                          * shows up (e.g., because we just removed a failed
  74                          * one, and we will soon get the correct one).
  75                          */
  76                         wait_for_entry_until = now + 30;
  77                 }
  78                 else {
  79                         if (entries[i].expiration < next)
  80                                 next = entries[i].expiration;
  81                         i++;
  82                 }
  83         }
  84
  85         if (!entries_nr) {
  86                 if (wait_for_entry_until <= now)
  87                         return 0;
  88                 next = wait_for_entry_until;
  89         }
  90
  91         return next - now;
  92 }
  93
  94 static int read_request(FILE *fh, struct credential *c,
  95                         struct strbuf *action, int *timeout) {
  96         static struct strbuf item = STRBUF_INIT;
  97         const char *p;
  98
  99         strbuf_getline_lf(&item, fh);
 100         if (!skip_prefix(item.buf, "action=", &p))
 101                 return error("client sent bogus action line: %s", item.buf);
 102         strbuf_addstr(action, p);
 103
 104         strbuf_getline_lf(&item, fh);
 105         if (!skip_prefix(item.buf, "timeout=", &p))
 106                 return error("client sent bogus timeout line: %s", item.buf);
 107         *timeout = atoi(p);
 108
 109         if (credential_read(c, fh) < 0)
 110                 return -1;
 111         return 0;
 112 }
 113
 114 static void serve_one_client(FILE *in, FILE *out)
 115 {
 116         struct credential c = CREDENTIAL_INIT;
 117         struct strbuf action = STRBUF_INIT;
 118         int timeout = -1;
 119
 120         if (read_request(in, &c, &action, &timeout) < 0)
 121                 /* ignore error */ ;
 122         else if (!strcmp(action.buf, "get")) {
 123                 struct credential_cache_entry *e = lookup_credential(&c);
 124                 if (e) {
 125                         fprintf(out, "username=%s\n", e->item.username);
 126                         fprintf(out, "password=%s\n", e->item.password);
 127                 }
 128         }
 129         else if (!strcmp(action.buf, "exit")) {
 130                 /*
 131                  * It's important that we clean up our socket first, and then
 132                  * signal the client only once we have finished the cleanup.
 133                  * Calling exit() directly does this, because we clean up in
 134                  * our atexit() handler, and then signal the client when our
 135                  * process actually ends, which closes the socket and gives
 136                  * them EOF.
 137                  */
 138                 exit(0);
 139         }
 140         else if (!strcmp(action.buf, "erase"))
 141                 remove_credential(&c);
 142         else if (!strcmp(action.buf, "store")) {
 143                 if (timeout < 0)
 144                         warning("cache client didn't specify a timeout");
 145                 else if (!c.username || !c.password)
 146                         warning("cache client gave us a partial credential");
 147                 else {
 148                         remove_credential(&c);
 149                         cache_credential(&c, timeout);
 150                 }
 151         }
 152         else
 153                 warning("cache client sent unknown action: %s", action.buf);
 154
 155         credential_clear(&c);
 156         strbuf_release(&action);
 157 }
 158
 159 static int serve_cache_loop(int fd)
 160 {
 161         struct pollfd pfd;
 162         unsigned long wakeup;
 163
 164         wakeup = check_expirations();
 165         if (!wakeup)
 166                 return 0;
 167
 168         pfd.fd = fd;
 169         pfd.events = POLLIN;
 170         if (poll(&pfd, 1, 1000 * wakeup) < 0) {
 171                 if (errno != EINTR)
 172                         die_errno("poll failed");
 173                 return 1;
 174         }
 175
 176         if (pfd.revents & POLLIN) {
 177                 int client, client2;
 178                 FILE *in, *out;
 179
 180                 client = accept(fd, NULL, NULL);
 181                 if (client < 0) {
 182                         warning_errno("accept failed");
 183                         return 1;
 184                 }
 185                 client2 = dup(client);
 186                 if (client2 < 0) {
 187                         warning_errno("dup failed");
 188                         close(client);
 189                         return 1;
 190                 }
 191
 192                 in = xfdopen(client, "r");
 193                 out = xfdopen(client2, "w");
 194                 serve_one_client(in, out);
 195                 fclose(in);
 196                 fclose(out);
 197         }
 198         return 1;
 199 }
 200
 201 static void serve_cache(const char *socket_path, int debug)
 202 {
 203         int fd;
 204
 205         fd = unix_stream_listen(socket_path);
 206         if (fd < 0)
 207                 die_errno("unable to bind to '%s'", socket_path);
 208
 209         printf("ok\n");
 210         fclose(stdout);
 211         if (!debug) {
 212                 if (!freopen("/dev/null", "w", stderr))
 213                         die_errno("unable to point stderr to /dev/null");
 214         }
 215
 216         while (serve_cache_loop(fd))
 217                 ; /* nothing */
 218
 219         close(fd);
 220 }
 221
 222 static const char permissions_advice[] =
 223 "The permissions on your socket directory are too loose; other\n"
 224 "users may be able to read your cached credentials. Consider running:\n"
 225 "\n"
 226 "       chmod 0700 %s";
 227 static void init_socket_directory(const char *path)
 228 {
 229         struct stat st;
 230         char *path_copy = xstrdup(path);
 231         char *dir = dirname(path_copy);
 232
 233         if (!stat(dir, &st)) {
 234                 if (st.st_mode & 077)
 235                         die(permissions_advice, dir);
 236         } else {
 237                 /*
 238                  * We must be sure to create the directory with the correct mode,
 239                  * not just chmod it after the fact; otherwise, there is a race
 240                  * condition in which somebody can chdir to it, sleep, then try to open
 241                  * our protected socket.
 242                  */
 243                 if (safe_create_leading_directories_const(dir) < 0)
 244                         die_errno("unable to create directories for '%s'", dir);
 245                 if (mkdir(dir, 0700) < 0)
 246                         die_errno("unable to mkdir '%s'", dir);
 247         }
 248
 249         if (chdir(dir))
 250                 /*
 251                  * We don't actually care what our cwd is; we chdir here just to
 252                  * be a friendly daemon and avoid tying up our original cwd.
 253                  * If this fails, it's OK to just continue without that benefit.
 254                  */
 255                 ;
 256
 257         free(path_copy);
 258 }
 259
 260 int main(int argc, const char **argv)
 261 {
 262         const char *socket_path;
 263         int ignore_sighup = 0;
 264         static const char *usage[] = {
 265                 "git-credential-cache--daemon [opts] <socket_path>",
 266                 NULL
 267         };
 268         int debug = 0;
 269         const struct option options[] = {
 270                 OPT_BOOL(0, "debug", &debug,
 271                          N_("print debugging messages to stderr")),
 272                 OPT_END()
 273         };
 274
 275         git_config_get_bool("credentialcache.ignoresighup", &ignore_sighup);
 276
 277         argc = parse_options(argc, argv, NULL, options, usage, 0);
 278         socket_path = argv[0];
 279
 280         if (!socket_path)
 281                 usage_with_options(usage, options);
 282
 283         if (!is_absolute_path(socket_path))
 284                 die("socket directory must be an absolute path");
 285
 286         init_socket_directory(socket_path);
 287         register_tempfile(&socket_file, socket_path);
 288
 289         if (ignore_sighup)
 290                 signal(SIGHUP, SIG_IGN);
 291
 292         serve_cache(socket_path, debug);
 293         delete_tempfile(&socket_file);
 294
 295         return 0;
 296 }