credential-cache--daemon.c

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