daemon.c

   1 #include <signal.h>
   2 #include <sys/wait.h>
   3 #include <sys/socket.h>
   4 #include <sys/time.h>
   5 #include <sys/poll.h>
   6 #include <netdb.h>
   7 #include <netinet/in.h>
   8 #include <arpa/inet.h>
   9 #include <syslog.h>
  10 #include "pkt-line.h"
  11 #include "cache.h"
  12 #include "exec_cmd.h"
  13
  14 static int log_syslog;
  15 static int verbose;
  16 static int reuseaddr;
  17
  18 static const char daemon_usage[] =
  19 "git-daemon [--verbose] [--syslog] [--inetd | --port=n] [--export-all]\n"
  20 "           [--timeout=n] [--init-timeout=n] [--strict-paths]\n"
  21 "           [--base-path=path] [--user-path | --user-path=path]\n"
  22 "           [--reuseaddr] [directory...]";
  23
  24 /* List of acceptable pathname prefixes */
  25 static char **ok_paths = NULL;
  26 static int strict_paths = 0;
  27
  28 /* If this is set, git-daemon-export-ok is not required */
  29 static int export_all_trees = 0;
  30
  31 /* Take all paths relative to this one if non-NULL */
  32 static char *base_path = NULL;
  33
  34 /* If defined, ~user notation is allowed and the string is inserted
  35  * after ~user/.  E.g. a request to git://host/~alice/frotz would
  36  * go to /home/alice/pub_git/frotz with --user-path=pub_git.
  37  */
  38 static char *user_path = NULL;
  39
  40 /* Timeout, and initial timeout */
  41 static unsigned int timeout = 0;
  42 static unsigned int init_timeout = 0;
  43
  44 static void logreport(int priority, const char *err, va_list params)
  45 {
  46         /* We should do a single write so that it is atomic and output
  47          * of several processes do not get intermingled. */
  48         char buf[1024];
  49         int buflen;
  50         int maxlen, msglen;
  51
  52         /* sizeof(buf) should be big enough for "[pid] \n" */
  53         buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());
  54
  55         maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
  56         msglen = vsnprintf(buf + buflen, maxlen, err, params);
  57
  58         if (log_syslog) {
  59                 syslog(priority, "%s", buf);
  60                 return;
  61         }
  62
  63         /* maxlen counted our own LF but also counts space given to
  64          * vsnprintf for the terminating NUL.  We want to make sure that
  65          * we have space for our own LF and NUL after the "meat" of the
  66          * message, so truncate it at maxlen - 1.
  67          */
  68         if (msglen > maxlen - 1)
  69                 msglen = maxlen - 1;
  70         else if (msglen < 0)
  71                 msglen = 0; /* Protect against weird return values. */
  72         buflen += msglen;
  73
  74         buf[buflen++] = '\n';
  75         buf[buflen] = '\0';
  76
  77         write(2, buf, buflen);
  78 }
  79
  80 static void logerror(const char *err, ...)
  81 {
  82         va_list params;
  83         va_start(params, err);
  84         logreport(LOG_ERR, err, params);
  85         va_end(params);
  86 }
  87
  88 static void loginfo(const char *err, ...)
  89 {
  90         va_list params;
  91         if (!verbose)
  92                 return;
  93         va_start(params, err);
  94         logreport(LOG_INFO, err, params);
  95         va_end(params);
  96 }
  97
  98 static int avoid_alias(char *p)
  99 {
 100         int sl, ndot;
 101
 102         /*
 103          * This resurrects the belts and suspenders paranoia check by HPA
 104          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 105          * does not do getcwd() based path canonicalizations.
 106          *
 107          * sl becomes true immediately after seeing '/' and continues to
 108          * be true as long as dots continue after that without intervening
 109          * non-dot character.
 110          */
 111         if (!p || (*p != '/' && *p != '~'))
 112                 return -1;
 113         sl = 1; ndot = 0;
 114         p++;
 115
 116         while (1) {
 117                 char ch = *p++;
 118                 if (sl) {
 119                         if (ch == '.')
 120                                 ndot++;
 121                         else if (ch == '/') {
 122                                 if (ndot < 3)
 123                                         /* reject //, /./ and /../ */
 124                                         return -1;
 125                                 ndot = 0;
 126                         }
 127                         else if (ch == 0) {
 128                                 if (0 < ndot && ndot < 3)
 129                                         /* reject /.$ and /..$ */
 130                                         return -1;
 131                                 return 0;
 132                         }
 133                         else
 134                                 sl = ndot = 0;
 135                 }
 136                 else if (ch == 0)
 137                         return 0;
 138                 else if (ch == '/') {
 139                         sl = 1;
 140                         ndot = 0;
 141                 }
 142         }
 143 }
 144
 145 static char *path_ok(char *dir)
 146 {
 147         static char rpath[PATH_MAX];
 148         char *path;
 149
 150         if (avoid_alias(dir)) {
 151                 logerror("'%s': aliased", dir);
 152                 return NULL;
 153         }
 154
 155         if (*dir == '~') {
 156                 if (!user_path) {
 157                         logerror("'%s': User-path not allowed", dir);
 158                         return NULL;
 159                 }
 160                 if (*user_path) {
 161                         /* Got either "~alice" or "~alice/foo";
 162                          * rewrite them to "~alice/%s" or
 163                          * "~alice/%s/foo".
 164                          */
 165                         int namlen, restlen = strlen(dir);
 166                         char *slash = strchr(dir, '/');
 167                         if (!slash)
 168                                 slash = dir + restlen;
 169                         namlen = slash - dir;
 170                         restlen -= namlen;
 171                         loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
 172                         snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
 173                                  namlen, dir, user_path, restlen, slash);
 174                         dir = rpath;
 175                 }
 176         }
 177         else if (base_path) {
 178                 if (*dir != '/') {
 179                         /* Allow only absolute */
 180                         logerror("'%s': Non-absolute path denied (base-path active)", dir);
 181                         return NULL;
 182                 }
 183                 else {
 184                         snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
 185                         dir = rpath;
 186                 }
 187         }
 188
 189         path = enter_repo(dir, strict_paths);
 190
 191         if (!path) {
 192                 logerror("'%s': unable to chdir or not a git archive", dir);
 193                 return NULL;
 194         }
 195
 196         if ( ok_paths && *ok_paths ) {
 197                 char **pp;
 198                 int pathlen = strlen(path);
 199
 200                 /* The validation is done on the paths after enter_repo
 201                  * appends optional {.git,.git/.git} and friends, but
 202                  * it does not use getcwd().  So if your /pub is
 203                  * a symlink to /mnt/pub, you can whitelist /pub and
 204                  * do not have to say /mnt/pub.
 205                  * Do not say /pub/.
 206                  */
 207                 for ( pp = ok_paths ; *pp ; pp++ ) {
 208                         int len = strlen(*pp);
 209                         if (len <= pathlen &&
 210                             !memcmp(*pp, path, len) &&
 211                             (path[len] == '\0' ||
 212                              (!strict_paths && path[len] == '/')))
 213                                 return path;
 214                 }
 215         }
 216         else {
 217                 /* be backwards compatible */
 218                 if (!strict_paths)
 219                         return path;
 220         }
 221
 222         logerror("'%s': not in whitelist", path);
 223         return NULL;            /* Fallthrough. Deny by default */
 224 }
 225
 226 static int upload(char *dir)
 227 {
 228         /* Timeout as string */
 229         char timeout_buf[64];
 230         const char *path;
 231
 232         loginfo("Request for '%s'", dir);
 233
 234         if (!(path = path_ok(dir)))
 235                 return -1;
 236
 237         /*
 238          * Security on the cheap.
 239          *
 240          * We want a readable HEAD, usable "objects" directory, and
 241          * a "git-daemon-export-ok" flag that says that the other side
 242          * is ok with us doing this.
 243          *
 244          * path_ok() uses enter_repo() and does whitelist checking.
 245          * We only need to make sure the repository is exported.
 246          */
 247
 248         if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
 249                 logerror("'%s': repository not exported.", path);
 250                 errno = EACCES;
 251                 return -1;
 252         }
 253
 254         /*
 255          * We'll ignore SIGTERM from now on, we have a
 256          * good client.
 257          */
 258         signal(SIGTERM, SIG_IGN);
 259
 260         snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);
 261
 262         /* git-upload-pack only ever reads stuff, so this is safe */
 263         execl_git_cmd("upload-pack", "--strict", timeout_buf, ".", NULL);
 264         return -1;
 265 }
 266
 267 static int execute(void)
 268 {
 269         static char line[1000];
 270         int len;
 271
 272         alarm(init_timeout ? init_timeout : timeout);
 273         len = packet_read_line(0, line, sizeof(line));
 274         alarm(0);
 275
 276         if (len && line[len-1] == '\n')
 277                 line[--len] = 0;
 278
 279         if (!strncmp("git-upload-pack ", line, 16))
 280                 return upload(line+16);
 281
 282         logerror("Protocol error: '%s'", line);
 283         return -1;
 284 }
 285
 286
 287 /*
 288  * We count spawned/reaped separately, just to avoid any
 289  * races when updating them from signals. The SIGCHLD handler
 290  * will only update children_reaped, and the fork logic will
 291  * only update children_spawned.
 292  *
 293  * MAX_CHILDREN should be a power-of-two to make the modulus
 294  * operation cheap. It should also be at least twice
 295  * the maximum number of connections we will ever allow.
 296  */
 297 #define MAX_CHILDREN 128
 298
 299 static int max_connections = 25;
 300
 301 /* These are updated by the signal handler */
 302 static volatile unsigned int children_reaped = 0;
 303 static pid_t dead_child[MAX_CHILDREN];
 304
 305 /* These are updated by the main loop */
 306 static unsigned int children_spawned = 0;
 307 static unsigned int children_deleted = 0;
 308
 309 static struct child {
 310         pid_t pid;
 311         int addrlen;
 312         struct sockaddr_storage address;
 313 } live_child[MAX_CHILDREN];
 314
 315 static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
 316 {
 317         live_child[idx].pid = pid;
 318         live_child[idx].addrlen = addrlen;
 319         memcpy(&live_child[idx].address, addr, addrlen);
 320 }
 321
 322 /*
 323  * Walk from "deleted" to "spawned", and remove child "pid".
 324  *
 325  * We move everything up by one, since the new "deleted" will
 326  * be one higher.
 327  */
 328 static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
 329 {
 330         struct child n;
 331
 332         deleted %= MAX_CHILDREN;
 333         spawned %= MAX_CHILDREN;
 334         if (live_child[deleted].pid == pid) {
 335                 live_child[deleted].pid = -1;
 336                 return;
 337         }
 338         n = live_child[deleted];
 339         for (;;) {
 340                 struct child m;
 341                 deleted = (deleted + 1) % MAX_CHILDREN;
 342                 if (deleted == spawned)
 343                         die("could not find dead child %d\n", pid);
 344                 m = live_child[deleted];
 345                 live_child[deleted] = n;
 346                 if (m.pid == pid)
 347                         return;
 348                 n = m;
 349         }
 350 }
 351
 352 /*
 353  * This gets called if the number of connections grows
 354  * past "max_connections".
 355  *
 356  * We _should_ start off by searching for connections
 357  * from the same IP, and if there is some address wth
 358  * multiple connections, we should kill that first.
 359  *
 360  * As it is, we just "randomly" kill 25% of the connections,
 361  * and our pseudo-random generator sucks too. I have no
 362  * shame.
 363  *
 364  * Really, this is just a place-holder for a _real_ algorithm.
 365  */
 366 static void kill_some_children(int signo, unsigned start, unsigned stop)
 367 {
 368         start %= MAX_CHILDREN;
 369         stop %= MAX_CHILDREN;
 370         while (start != stop) {
 371                 if (!(start & 3))
 372                         kill(live_child[start].pid, signo);
 373                 start = (start + 1) % MAX_CHILDREN;
 374         }
 375 }
 376
 377 static void check_max_connections(void)
 378 {
 379         for (;;) {
 380                 int active;
 381                 unsigned spawned, reaped, deleted;
 382
 383                 spawned = children_spawned;
 384                 reaped = children_reaped;
 385                 deleted = children_deleted;
 386
 387                 while (deleted < reaped) {
 388                         pid_t pid = dead_child[deleted % MAX_CHILDREN];
 389                         remove_child(pid, deleted, spawned);
 390                         deleted++;
 391                 }
 392                 children_deleted = deleted;
 393
 394                 active = spawned - deleted;
 395                 if (active <= max_connections)
 396                         break;
 397
 398                 /* Kill some unstarted connections with SIGTERM */
 399                 kill_some_children(SIGTERM, deleted, spawned);
 400                 if (active <= max_connections << 1)
 401                         break;
 402
 403                 /* If the SIGTERM thing isn't helping use SIGKILL */
 404                 kill_some_children(SIGKILL, deleted, spawned);
 405                 sleep(1);
 406         }
 407 }
 408
 409 static void handle(int incoming, struct sockaddr *addr, int addrlen)
 410 {
 411         pid_t pid = fork();
 412         char addrbuf[256] = "";
 413         int port = -1;
 414
 415         if (pid) {
 416                 unsigned idx;
 417
 418                 close(incoming);
 419                 if (pid < 0)
 420                         return;
 421
 422                 idx = children_spawned % MAX_CHILDREN;
 423                 children_spawned++;
 424                 add_child(idx, pid, addr, addrlen);
 425
 426                 check_max_connections();
 427                 return;
 428         }
 429
 430         dup2(incoming, 0);
 431         dup2(incoming, 1);
 432         close(incoming);
 433
 434         if (addr->sa_family == AF_INET) {
 435                 struct sockaddr_in *sin_addr = (void *) addr;
 436                 inet_ntop(AF_INET, &sin_addr->sin_addr, addrbuf, sizeof(addrbuf));
 437                 port = sin_addr->sin_port;
 438
 439 #ifndef NO_IPV6
 440         } else if (addr->sa_family == AF_INET6) {
 441                 struct sockaddr_in6 *sin6_addr = (void *) addr;
 442
 443                 char *buf = addrbuf;
 444                 *buf++ = '['; *buf = '\0'; /* stpcpy() is cool */
 445                 inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(addrbuf) - 1);
 446                 strcat(buf, "]");
 447
 448                 port = sin6_addr->sin6_port;
 449 #endif
 450         }
 451         loginfo("Connection from %s:%d", addrbuf, port);
 452
 453         exit(execute());
 454 }
 455
 456 static void child_handler(int signo)
 457 {
 458         for (;;) {
 459                 int status;
 460                 pid_t pid = waitpid(-1, &status, WNOHANG);
 461
 462                 if (pid > 0) {
 463                         unsigned reaped = children_reaped;
 464                         dead_child[reaped % MAX_CHILDREN] = pid;
 465                         children_reaped = reaped + 1;
 466                         /* XXX: Custom logging, since we don't wanna getpid() */
 467                         if (verbose) {
 468                                 char *dead = "";
 469                                 if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
 470                                         dead = " (with error)";
 471                                 if (log_syslog)
 472                                         syslog(LOG_INFO, "[%d] Disconnected%s", pid, dead);
 473                                 else
 474                                         fprintf(stderr, "[%d] Disconnected%s\n", pid, dead);
 475                         }
 476                         continue;
 477                 }
 478                 break;
 479         }
 480 }
 481
 482 static int set_reuse_addr(int sockfd)
 483 {
 484         int on = 1;
 485
 486         if (!reuseaddr)
 487                 return 0;
 488         return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
 489                           &on, sizeof(on));
 490 }
 491
 492 #ifndef NO_IPV6
 493
 494 static int socksetup(int port, int **socklist_p)
 495 {
 496         int socknum = 0, *socklist = NULL;
 497         int maxfd = -1;
 498         char pbuf[NI_MAXSERV];
 499
 500         struct addrinfo hints, *ai0, *ai;
 501         int gai;
 502
 503         sprintf(pbuf, "%d", port);
 504         memset(&hints, 0, sizeof(hints));
 505         hints.ai_family = AF_UNSPEC;
 506         hints.ai_socktype = SOCK_STREAM;
 507         hints.ai_protocol = IPPROTO_TCP;
 508         hints.ai_flags = AI_PASSIVE;
 509
 510         gai = getaddrinfo(NULL, pbuf, &hints, &ai0);
 511         if (gai)
 512                 die("getaddrinfo() failed: %s\n", gai_strerror(gai));
 513
 514         for (ai = ai0; ai; ai = ai->ai_next) {
 515                 int sockfd;
 516                 int *newlist;
 517
 518                 sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 519                 if (sockfd < 0)
 520                         continue;
 521                 if (sockfd >= FD_SETSIZE) {
 522                         error("too large socket descriptor.");
 523                         close(sockfd);
 524                         continue;
 525                 }
 526
 527 #ifdef IPV6_V6ONLY
 528                 if (ai->ai_family == AF_INET6) {
 529                         int on = 1;
 530                         setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
 531                                    &on, sizeof(on));
 532                         /* Note: error is not fatal */
 533                 }
 534 #endif
 535
 536                 if (set_reuse_addr(sockfd)) {
 537                         close(sockfd);
 538                         return 0;       /* not fatal */
 539                 }
 540
 541                 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
 542                         close(sockfd);
 543                         continue;       /* not fatal */
 544                 }
 545                 if (listen(sockfd, 5) < 0) {
 546                         close(sockfd);
 547                         continue;       /* not fatal */
 548                 }
 549
 550                 newlist = realloc(socklist, sizeof(int) * (socknum + 1));
 551                 if (!newlist)
 552                         die("memory allocation failed: %s", strerror(errno));
 553
 554                 socklist = newlist;
 555                 socklist[socknum++] = sockfd;
 556
 557                 if (maxfd < sockfd)
 558                         maxfd = sockfd;
 559         }
 560
 561         freeaddrinfo(ai0);
 562
 563         *socklist_p = socklist;
 564         return socknum;
 565 }
 566
 567 #else /* NO_IPV6 */
 568
 569 static int socksetup(int port, int **socklist_p)
 570 {
 571         struct sockaddr_in sin;
 572         int sockfd;
 573
 574         sockfd = socket(AF_INET, SOCK_STREAM, 0);
 575         if (sockfd < 0)
 576                 return 0;
 577
 578         memset(&sin, 0, sizeof sin);
 579         sin.sin_family = AF_INET;
 580         sin.sin_addr.s_addr = htonl(INADDR_ANY);
 581         sin.sin_port = htons(port);
 582
 583         if (set_reuse_addr(sockfd)) {
 584                 close(sockfd);
 585                 return 0;
 586         }
 587
 588         if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
 589                 close(sockfd);
 590                 return 0;
 591         }
 592
 593         if (listen(sockfd, 5) < 0) {
 594                 close(sockfd);
 595                 return 0;
 596         }
 597
 598         *socklist_p = xmalloc(sizeof(int));
 599         **socklist_p = sockfd;
 600         return 1;
 601 }
 602
 603 #endif
 604
 605 static int service_loop(int socknum, int *socklist)
 606 {
 607         struct pollfd *pfd;
 608         int i;
 609
 610         pfd = xcalloc(socknum, sizeof(struct pollfd));
 611
 612         for (i = 0; i < socknum; i++) {
 613                 pfd[i].fd = socklist[i];
 614                 pfd[i].events = POLLIN;
 615         }
 616
 617         signal(SIGCHLD, child_handler);
 618
 619         for (;;) {
 620                 int i;
 621
 622                 if (poll(pfd, socknum, -1) < 0) {
 623                         if (errno != EINTR) {
 624                                 error("poll failed, resuming: %s",
 625                                       strerror(errno));
 626                                 sleep(1);
 627                         }
 628                         continue;
 629                 }
 630
 631                 for (i = 0; i < socknum; i++) {
 632                         if (pfd[i].revents & POLLIN) {
 633                                 struct sockaddr_storage ss;
 634                                 unsigned int sslen = sizeof(ss);
 635                                 int incoming = accept(pfd[i].fd, (struct sockaddr *)&ss, &sslen);
 636                                 if (incoming < 0) {
 637                                         switch (errno) {
 638                                         case EAGAIN:
 639                                         case EINTR:
 640                                         case ECONNABORTED:
 641                                                 continue;
 642                                         default:
 643                                                 die("accept returned %s", strerror(errno));
 644                                         }
 645                                 }
 646                                 handle(incoming, (struct sockaddr *)&ss, sslen);
 647                         }
 648                 }
 649         }
 650 }
 651
 652 static int serve(int port)
 653 {
 654         int socknum, *socklist;
 655
 656         socknum = socksetup(port, &socklist);
 657         if (socknum == 0)
 658                 die("unable to allocate any listen sockets on port %u", port);
 659
 660         return service_loop(socknum, socklist);
 661 }
 662
 663 int main(int argc, char **argv)
 664 {
 665         int port = DEFAULT_GIT_PORT;
 666         int inetd_mode = 0;
 667         int i;
 668
 669         for (i = 1; i < argc; i++) {
 670                 char *arg = argv[i];
 671
 672                 if (!strncmp(arg, "--port=", 7)) {
 673                         char *end;
 674                         unsigned long n;
 675                         n = strtoul(arg+7, &end, 0);
 676                         if (arg[7] && !*end) {
 677                                 port = n;
 678                                 continue;
 679                         }
 680                 }
 681                 if (!strcmp(arg, "--inetd")) {
 682                         inetd_mode = 1;
 683                         log_syslog = 1;
 684                         continue;
 685                 }
 686                 if (!strcmp(arg, "--verbose")) {
 687                         verbose = 1;
 688                         continue;
 689                 }
 690                 if (!strcmp(arg, "--syslog")) {
 691                         log_syslog = 1;
 692                         continue;
 693                 }
 694                 if (!strcmp(arg, "--export-all")) {
 695                         export_all_trees = 1;
 696                         continue;
 697                 }
 698                 if (!strncmp(arg, "--timeout=", 10)) {
 699                         timeout = atoi(arg+10);
 700                         continue;
 701                 }
 702                 if (!strncmp(arg, "--init-timeout=", 15)) {
 703                         init_timeout = atoi(arg+15);
 704                         continue;
 705                 }
 706                 if (!strcmp(arg, "--strict-paths")) {
 707                         strict_paths = 1;
 708                         continue;
 709                 }
 710                 if (!strncmp(arg, "--base-path=", 12)) {
 711                         base_path = arg+12;
 712                         continue;
 713                 }
 714                 if (!strcmp(arg, "--reuseaddr")) {
 715                         reuseaddr = 1;
 716                         continue;
 717                 }
 718                 if (!strcmp(arg, "--user-path")) {
 719                         user_path = "";
 720                         continue;
 721                 }
 722                 if (!strncmp(arg, "--user-path=", 12)) {
 723                         user_path = arg + 12;
 724                         continue;
 725                 }
 726                 if (!strcmp(arg, "--")) {
 727                         ok_paths = &argv[i+1];
 728                         break;
 729                 } else if (arg[0] != '-') {
 730                         ok_paths = &argv[i];
 731                         break;
 732                 }
 733
 734                 usage(daemon_usage);
 735         }
 736
 737         if (log_syslog)
 738                 openlog("git-daemon", 0, LOG_DAEMON);
 739
 740         if (strict_paths && (!ok_paths || !*ok_paths)) {
 741                 if (!inetd_mode)
 742                         die("git-daemon: option --strict-paths requires a whitelist");
 743
 744                 logerror("option --strict-paths requires a whitelist");
 745                 exit (1);
 746         }
 747
 748         if (inetd_mode) {
 749                 fclose(stderr); //FIXME: workaround
 750                 return execute();
 751         }
 752
 753         return serve(port);
 754 }