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         p = skip_prefix(item.buf, "action=");
 113         if (!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         p = skip_prefix(item.buf, "timeout=");
 119         if (!p)
 120                 return error("client sent bogus timeout line: %s", item.buf);
 121         *timeout = atoi(p);
 122
 123         if (credential_read(c, fh) < 0)
 124                 return -1;
 125         return 0;
 126 }
 127
 128 static void serve_one_client(FILE *in, FILE *out)
 129 {
 130         struct credential c = CREDENTIAL_INIT;
 131         struct strbuf action = STRBUF_INIT;
 132         int timeout = -1;
 133
 134         if (read_request(in, &c, &action, &timeout) < 0)
 135                 /* ignore error */ ;
 136         else if (!strcmp(action.buf, "get")) {
 137                 struct credential_cache_entry *e = lookup_credential(&c);
 138                 if (e) {
 139                         fprintf(out, "username=%s\n", e->item.username);
 140                         fprintf(out, "password=%s\n", e->item.password);
 141                 }
 142         }
 143         else if (!strcmp(action.buf, "exit"))
 144                 exit(0);
 145         else if (!strcmp(action.buf, "erase"))
 146                 remove_credential(&c);
 147         else if (!strcmp(action.buf, "store")) {
 148                 if (timeout < 0)
 149                         warning("cache client didn't specify a timeout");
 150                 else if (!c.username || !c.password)
 151                         warning("cache client gave us a partial credential");
 152                 else {
 153                         remove_credential(&c);
 154                         cache_credential(&c, timeout);
 155                 }
 156         }
 157         else
 158                 warning("cache client sent unknown action: %s", action.buf);
 159
 160         credential_clear(&c);
 161         strbuf_release(&action);
 162 }
 163
 164 static int serve_cache_loop(int fd)
 165 {
 166         struct pollfd pfd;
 167         unsigned long wakeup;
 168
 169         wakeup = check_expirations();
 170         if (!wakeup)
 171                 return 0;
 172
 173         pfd.fd = fd;
 174         pfd.events = POLLIN;
 175         if (poll(&pfd, 1, 1000 * wakeup) < 0) {
 176                 if (errno != EINTR)
 177                         die_errno("poll failed");
 178                 return 1;
 179         }
 180
 181         if (pfd.revents & POLLIN) {
 182                 int client, client2;
 183                 FILE *in, *out;
 184
 185                 client = accept(fd, NULL, NULL);
 186                 if (client < 0) {
 187                         warning("accept failed: %s", strerror(errno));
 188                         return 1;
 189                 }
 190                 client2 = dup(client);
 191                 if (client2 < 0) {
 192                         warning("dup failed: %s", strerror(errno));
 193                         close(client);
 194                         return 1;
 195                 }
 196
 197                 in = xfdopen(client, "r");
 198                 out = xfdopen(client2, "w");
 199                 serve_one_client(in, out);
 200                 fclose(in);
 201                 fclose(out);
 202         }
 203         return 1;
 204 }
 205
 206 static void serve_cache(const char *socket_path)
 207 {
 208         int fd;
 209
 210         fd = unix_stream_listen(socket_path);
 211         if (fd < 0)
 212                 die_errno("unable to bind to '%s'", socket_path);
 213
 214         printf("ok\n");
 215         fclose(stdout);
 216
 217         while (serve_cache_loop(fd))
 218                 ; /* nothing */
 219
 220         close(fd);
 221         unlink(socket_path);
 222 }
 223
 224 static const char permissions_advice[] =
 225 "The permissions on your socket directory are too loose; other\n"
 226 "users may be able to read your cached credentials. Consider running:\n"
 227 "\n"
 228 "       chmod 0700 %s";
 229 static void check_socket_directory(const char *path)
 230 {
 231         struct stat st;
 232         char *path_copy = xstrdup(path);
 233         char *dir = dirname(path_copy);
 234
 235         if (!stat(dir, &st)) {
 236                 if (st.st_mode & 077)
 237                         die(permissions_advice, dir);
 238                 free(path_copy);
 239                 return;
 240         }
 241
 242         /*
 243          * We must be sure to create the directory with the correct mode,
 244          * not just chmod it after the fact; otherwise, there is a race
 245          * condition in which somebody can chdir to it, sleep, then try to open
 246          * our protected socket.
 247          */
 248         if (safe_create_leading_directories_const(dir) < 0)
 249                 die_errno("unable to create directories for '%s'", dir);
 250         if (mkdir(dir, 0700) < 0)
 251                 die_errno("unable to mkdir '%s'", dir);
 252         free(path_copy);
 253 }
 254
 255 int main(int argc, const char **argv)
 256 {
 257         socket_path = argv[1];
 258
 259         if (!socket_path)
 260                 die("usage: git-credential-cache--daemon <socket_path>");
 261         check_socket_directory(socket_path);
 262
 263         atexit(cleanup_socket);
 264         sigchain_push_common(cleanup_socket_on_signal);
 265
 266         serve_cache(socket_path);
 267
 268         return 0;
 269 }