credential-cache--daemon.c

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