credential-cache--daemon.c

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