daemon.c

   1 #include "cache.h"
   2 #include "pkt-line.h"
   3 #include "exec_cmd.h"
   4 #include "interpolate.h"
   5
   6 #include <syslog.h>
   7
   8 #ifndef HOST_NAME_MAX
   9 #define HOST_NAME_MAX 256
  10 #endif
  11
  12 #ifndef NI_MAXSERV
  13 #define NI_MAXSERV 32
  14 #endif
  15
  16 static int log_syslog;
  17 static int verbose;
  18 static int reuseaddr;
  19
  20 static const char daemon_usage[] =
  21 "git-daemon [--verbose] [--syslog] [--export-all]\n"
  22 "           [--timeout=n] [--init-timeout=n] [--strict-paths]\n"
  23 "           [--base-path=path] [--base-path-relaxed]\n"
  24 "           [--user-path | --user-path=path]\n"
  25 "           [--interpolated-path=path]\n"
  26 "           [--reuseaddr] [--detach] [--pid-file=file]\n"
  27 "           [--[enable|disable|allow-override|forbid-override]=service]\n"
  28 "           [--inetd | [--listen=host_or_ipaddr] [--port=n]\n"
  29 "                      [--user=user [--group=group]]\n"
  30 "           [directory...]";
  31
  32 /* List of acceptable pathname prefixes */
  33 static char **ok_paths;
  34 static int strict_paths;
  35
  36 /* If this is set, git-daemon-export-ok is not required */
  37 static int export_all_trees;
  38
  39 /* Take all paths relative to this one if non-NULL */
  40 static char *base_path;
  41 static char *interpolated_path;
  42 static int base_path_relaxed;
  43
  44 /* Flag indicating client sent extra args. */
  45 static int saw_extended_args;
  46
  47 /* If defined, ~user notation is allowed and the string is inserted
  48  * after ~user/.  E.g. a request to git://host/~alice/frotz would
  49  * go to /home/alice/pub_git/frotz with --user-path=pub_git.
  50  */
  51 static const char *user_path;
  52
  53 /* Timeout, and initial timeout */
  54 static unsigned int timeout;
  55 static unsigned int init_timeout;
  56
  57 /*
  58  * Static table for now.  Ugh.
  59  * Feel free to make dynamic as needed.
  60  */
  61 #define INTERP_SLOT_HOST        (0)
  62 #define INTERP_SLOT_CANON_HOST  (1)
  63 #define INTERP_SLOT_IP          (2)
  64 #define INTERP_SLOT_PORT        (3)
  65 #define INTERP_SLOT_DIR         (4)
  66 #define INTERP_SLOT_PERCENT     (5)
  67
  68 static struct interp interp_table[] = {
  69         { "%H", 0},
  70         { "%CH", 0},
  71         { "%IP", 0},
  72         { "%P", 0},
  73         { "%D", 0},
  74         { "%%", 0},
  75 };
  76
  77
  78 static void logreport(int priority, const char *err, va_list params)
  79 {
  80         /* We should do a single write so that it is atomic and output
  81          * of several processes do not get intermingled. */
  82         char buf[1024];
  83         int buflen;
  84         int maxlen, msglen;
  85
  86         /* sizeof(buf) should be big enough for "[pid] \n" */
  87         buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());
  88
  89         maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
  90         msglen = vsnprintf(buf + buflen, maxlen, err, params);
  91
  92         if (log_syslog) {
  93                 syslog(priority, "%s", buf);
  94                 return;
  95         }
  96
  97         /* maxlen counted our own LF but also counts space given to
  98          * vsnprintf for the terminating NUL.  We want to make sure that
  99          * we have space for our own LF and NUL after the "meat" of the
 100          * message, so truncate it at maxlen - 1.
 101          */
 102         if (msglen > maxlen - 1)
 103                 msglen = maxlen - 1;
 104         else if (msglen < 0)
 105                 msglen = 0; /* Protect against weird return values. */
 106         buflen += msglen;
 107
 108         buf[buflen++] = '\n';
 109         buf[buflen] = '\0';
 110
 111         write_in_full(2, buf, buflen);
 112 }
 113
 114 static void logerror(const char *err, ...)
 115 {
 116         va_list params;
 117         va_start(params, err);
 118         logreport(LOG_ERR, err, params);
 119         va_end(params);
 120 }
 121
 122 static void loginfo(const char *err, ...)
 123 {
 124         va_list params;
 125         if (!verbose)
 126                 return;
 127         va_start(params, err);
 128         logreport(LOG_INFO, err, params);
 129         va_end(params);
 130 }
 131
 132 static void NORETURN daemon_die(const char *err, va_list params)
 133 {
 134         logreport(LOG_ERR, err, params);
 135         exit(1);
 136 }
 137
 138 static int avoid_alias(char *p)
 139 {
 140         int sl, ndot;
 141
 142         /*
 143          * This resurrects the belts and suspenders paranoia check by HPA
 144          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 145          * does not do getcwd() based path canonicalizations.
 146          *
 147          * sl becomes true immediately after seeing '/' and continues to
 148          * be true as long as dots continue after that without intervening
 149          * non-dot character.
 150          */
 151         if (!p || (*p != '/' && *p != '~'))
 152                 return -1;
 153         sl = 1; ndot = 0;
 154         p++;
 155
 156         while (1) {
 157                 char ch = *p++;
 158                 if (sl) {
 159                         if (ch == '.')
 160                                 ndot++;
 161                         else if (ch == '/') {
 162                                 if (ndot < 3)
 163                                         /* reject //, /./ and /../ */
 164                                         return -1;
 165                                 ndot = 0;
 166                         }
 167                         else if (ch == 0) {
 168                                 if (0 < ndot && ndot < 3)
 169                                         /* reject /.$ and /..$ */
 170                                         return -1;
 171                                 return 0;
 172                         }
 173                         else
 174                                 sl = ndot = 0;
 175                 }
 176                 else if (ch == 0)
 177                         return 0;
 178                 else if (ch == '/') {
 179                         sl = 1;
 180                         ndot = 0;
 181                 }
 182         }
 183 }
 184
 185 static char *path_ok(struct interp *itable)
 186 {
 187         static char rpath[PATH_MAX];
 188         static char interp_path[PATH_MAX];
 189         int retried_path = 0;
 190         char *path;
 191         char *dir;
 192
 193         dir = itable[INTERP_SLOT_DIR].value;
 194
 195         if (avoid_alias(dir)) {
 196                 logerror("'%s': aliased", dir);
 197                 return NULL;
 198         }
 199
 200         if (*dir == '~') {
 201                 if (!user_path) {
 202                         logerror("'%s': User-path not allowed", dir);
 203                         return NULL;
 204                 }
 205                 if (*user_path) {
 206                         /* Got either "~alice" or "~alice/foo";
 207                          * rewrite them to "~alice/%s" or
 208                          * "~alice/%s/foo".
 209                          */
 210                         int namlen, restlen = strlen(dir);
 211                         char *slash = strchr(dir, '/');
 212                         if (!slash)
 213                                 slash = dir + restlen;
 214                         namlen = slash - dir;
 215                         restlen -= namlen;
 216                         loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
 217                         snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
 218                                  namlen, dir, user_path, restlen, slash);
 219                         dir = rpath;
 220                 }
 221         }
 222         else if (interpolated_path && saw_extended_args) {
 223                 if (*dir != '/') {
 224                         /* Allow only absolute */
 225                         logerror("'%s': Non-absolute path denied (interpolated-path active)", dir);
 226                         return NULL;
 227                 }
 228
 229                 interpolate(interp_path, PATH_MAX, interpolated_path,
 230                             interp_table, ARRAY_SIZE(interp_table));
 231                 loginfo("Interpolated dir '%s'", interp_path);
 232
 233                 dir = interp_path;
 234         }
 235         else if (base_path) {
 236                 if (*dir != '/') {
 237                         /* Allow only absolute */
 238                         logerror("'%s': Non-absolute path denied (base-path active)", dir);
 239                         return NULL;
 240                 }
 241                 snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
 242                 dir = rpath;
 243         }
 244
 245         do {
 246                 path = enter_repo(dir, strict_paths);
 247                 if (path)
 248                         break;
 249
 250                 /*
 251                  * if we fail and base_path_relaxed is enabled, try without
 252                  * prefixing the base path
 253                  */
 254                 if (base_path && base_path_relaxed && !retried_path) {
 255                         dir = itable[INTERP_SLOT_DIR].value;
 256                         retried_path = 1;
 257                         continue;
 258                 }
 259                 break;
 260         } while (1);
 261
 262         if (!path) {
 263                 logerror("'%s': unable to chdir or not a git archive", dir);
 264                 return NULL;
 265         }
 266
 267         if ( ok_paths && *ok_paths ) {
 268                 char **pp;
 269                 int pathlen = strlen(path);
 270
 271                 /* The validation is done on the paths after enter_repo
 272                  * appends optional {.git,.git/.git} and friends, but
 273                  * it does not use getcwd().  So if your /pub is
 274                  * a symlink to /mnt/pub, you can whitelist /pub and
 275                  * do not have to say /mnt/pub.
 276                  * Do not say /pub/.
 277                  */
 278                 for ( pp = ok_paths ; *pp ; pp++ ) {
 279                         int len = strlen(*pp);
 280                         if (len <= pathlen &&
 281                             !memcmp(*pp, path, len) &&
 282                             (path[len] == '\0' ||
 283                              (!strict_paths && path[len] == '/')))
 284                                 return path;
 285                 }
 286         }
 287         else {
 288                 /* be backwards compatible */
 289                 if (!strict_paths)
 290                         return path;
 291         }
 292
 293         logerror("'%s': not in whitelist", path);
 294         return NULL;            /* Fallthrough. Deny by default */
 295 }
 296
 297 typedef int (*daemon_service_fn)(void);
 298 struct daemon_service {
 299         const char *name;
 300         const char *config_name;
 301         daemon_service_fn fn;
 302         int enabled;
 303         int overridable;
 304 };
 305
 306 static struct daemon_service *service_looking_at;
 307 static int service_enabled;
 308
 309 static int git_daemon_config(const char *var, const char *value, void *cb)
 310 {
 311         if (!prefixcmp(var, "daemon.") &&
 312             !strcmp(var + 7, service_looking_at->config_name)) {
 313                 service_enabled = git_config_bool(var, value);
 314                 return 0;
 315         }
 316
 317         /* we are not interested in parsing any other configuration here */
 318         return 0;
 319 }
 320
 321 static int run_service(struct interp *itable, struct daemon_service *service)
 322 {
 323         const char *path;
 324         int enabled = service->enabled;
 325
 326         loginfo("Request %s for '%s'",
 327                 service->name,
 328                 itable[INTERP_SLOT_DIR].value);
 329
 330         if (!enabled && !service->overridable) {
 331                 logerror("'%s': service not enabled.", service->name);
 332                 errno = EACCES;
 333                 return -1;
 334         }
 335
 336         if (!(path = path_ok(itable)))
 337                 return -1;
 338
 339         /*
 340          * Security on the cheap.
 341          *
 342          * We want a readable HEAD, usable "objects" directory, and
 343          * a "git-daemon-export-ok" flag that says that the other side
 344          * is ok with us doing this.
 345          *
 346          * path_ok() uses enter_repo() and does whitelist checking.
 347          * We only need to make sure the repository is exported.
 348          */
 349
 350         if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
 351                 logerror("'%s': repository not exported.", path);
 352                 errno = EACCES;
 353                 return -1;
 354         }
 355
 356         if (service->overridable) {
 357                 service_looking_at = service;
 358                 service_enabled = -1;
 359                 git_config(git_daemon_config, NULL);
 360                 if (0 <= service_enabled)
 361                         enabled = service_enabled;
 362         }
 363         if (!enabled) {
 364                 logerror("'%s': service not enabled for '%s'",
 365                          service->name, path);
 366                 errno = EACCES;
 367                 return -1;
 368         }
 369
 370         /*
 371          * We'll ignore SIGTERM from now on, we have a
 372          * good client.
 373          */
 374         signal(SIGTERM, SIG_IGN);
 375
 376         return service->fn();
 377 }
 378
 379 static int upload_pack(void)
 380 {
 381         /* Timeout as string */
 382         char timeout_buf[64];
 383
 384         snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);
 385
 386         /* git-upload-pack only ever reads stuff, so this is safe */
 387         execl_git_cmd("upload-pack", "--strict", timeout_buf, ".", NULL);
 388         return -1;
 389 }
 390
 391 static int upload_archive(void)
 392 {
 393         execl_git_cmd("upload-archive", ".", NULL);
 394         return -1;
 395 }
 396
 397 static int receive_pack(void)
 398 {
 399         execl_git_cmd("receive-pack", ".", NULL);
 400         return -1;
 401 }
 402
 403 static struct daemon_service daemon_service[] = {
 404         { "upload-archive", "uploadarch", upload_archive, 0, 1 },
 405         { "upload-pack", "uploadpack", upload_pack, 1, 1 },
 406         { "receive-pack", "receivepack", receive_pack, 0, 1 },
 407 };
 408
 409 static void enable_service(const char *name, int ena)
 410 {
 411         int i;
 412         for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
 413                 if (!strcmp(daemon_service[i].name, name)) {
 414                         daemon_service[i].enabled = ena;
 415                         return;
 416                 }
 417         }
 418         die("No such service %s", name);
 419 }
 420
 421 static void make_service_overridable(const char *name, int ena)
 422 {
 423         int i;
 424         for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
 425                 if (!strcmp(daemon_service[i].name, name)) {
 426                         daemon_service[i].overridable = ena;
 427                         return;
 428                 }
 429         }
 430         die("No such service %s", name);
 431 }
 432
 433 /*
 434  * Separate the "extra args" information as supplied by the client connection.
 435  * Any resulting data is squirreled away in the given interpolation table.
 436  */
 437 static void parse_extra_args(struct interp *table, char *extra_args, int buflen)
 438 {
 439         char *val;
 440         int vallen;
 441         char *end = extra_args + buflen;
 442
 443         while (extra_args < end && *extra_args) {
 444                 saw_extended_args = 1;
 445                 if (strncasecmp("host=", extra_args, 5) == 0) {
 446                         val = extra_args + 5;
 447                         vallen = strlen(val) + 1;
 448                         if (*val) {
 449                                 /* Split <host>:<port> at colon. */
 450                                 char *host = val;
 451                                 char *port = strrchr(host, ':');
 452                                 if (port) {
 453                                         *port = 0;
 454                                         port++;
 455                                         interp_set_entry(table, INTERP_SLOT_PORT, port);
 456                                 }
 457                                 interp_set_entry(table, INTERP_SLOT_HOST, host);
 458                         }
 459
 460                         /* On to the next one */
 461                         extra_args = val + vallen;
 462                 }
 463         }
 464 }
 465
 466 static void fill_in_extra_table_entries(struct interp *itable)
 467 {
 468         char *hp;
 469
 470         /*
 471          * Replace literal host with lowercase-ized hostname.
 472          */
 473         hp = interp_table[INTERP_SLOT_HOST].value;
 474         if (!hp)
 475                 return;
 476         for ( ; *hp; hp++)
 477                 *hp = tolower(*hp);
 478
 479         /*
 480          * Locate canonical hostname and its IP address.
 481          */
 482 #ifndef NO_IPV6
 483         {
 484                 struct addrinfo hints;
 485                 struct addrinfo *ai, *ai0;
 486                 int gai;
 487                 static char addrbuf[HOST_NAME_MAX + 1];
 488
 489                 memset(&hints, 0, sizeof(hints));
 490                 hints.ai_flags = AI_CANONNAME;
 491
 492                 gai = getaddrinfo(interp_table[INTERP_SLOT_HOST].value, 0, &hints, &ai0);
 493                 if (!gai) {
 494                         for (ai = ai0; ai; ai = ai->ai_next) {
 495                                 struct sockaddr_in *sin_addr = (void *)ai->ai_addr;
 496
 497                                 inet_ntop(AF_INET, &sin_addr->sin_addr,
 498                                           addrbuf, sizeof(addrbuf));
 499                                 interp_set_entry(interp_table,
 500                                                  INTERP_SLOT_CANON_HOST, ai->ai_canonname);
 501                                 interp_set_entry(interp_table,
 502                                                  INTERP_SLOT_IP, addrbuf);
 503                                 break;
 504                         }
 505                         freeaddrinfo(ai0);
 506                 }
 507         }
 508 #else
 509         {
 510                 struct hostent *hent;
 511                 struct sockaddr_in sa;
 512                 char **ap;
 513                 static char addrbuf[HOST_NAME_MAX + 1];
 514
 515                 hent = gethostbyname(interp_table[INTERP_SLOT_HOST].value);
 516
 517                 ap = hent->h_addr_list;
 518                 memset(&sa, 0, sizeof sa);
 519                 sa.sin_family = hent->h_addrtype;
 520                 sa.sin_port = htons(0);
 521                 memcpy(&sa.sin_addr, *ap, hent->h_length);
 522
 523                 inet_ntop(hent->h_addrtype, &sa.sin_addr,
 524                           addrbuf, sizeof(addrbuf));
 525
 526                 interp_set_entry(interp_table, INTERP_SLOT_CANON_HOST, hent->h_name);
 527                 interp_set_entry(interp_table, INTERP_SLOT_IP, addrbuf);
 528         }
 529 #endif
 530 }
 531
 532
 533 static int execute(struct sockaddr *addr)
 534 {
 535         static char line[1000];
 536         int pktlen, len, i;
 537
 538         if (addr) {
 539                 char addrbuf[256] = "";
 540                 int port = -1;
 541
 542                 if (addr->sa_family == AF_INET) {
 543                         struct sockaddr_in *sin_addr = (void *) addr;
 544                         inet_ntop(addr->sa_family, &sin_addr->sin_addr, addrbuf, sizeof(addrbuf));
 545                         port = ntohs(sin_addr->sin_port);
 546 #ifndef NO_IPV6
 547                 } else if (addr && addr->sa_family == AF_INET6) {
 548                         struct sockaddr_in6 *sin6_addr = (void *) addr;
 549
 550                         char *buf = addrbuf;
 551                         *buf++ = '['; *buf = '\0'; /* stpcpy() is cool */
 552                         inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(addrbuf) - 1);
 553                         strcat(buf, "]");
 554
 555                         port = ntohs(sin6_addr->sin6_port);
 556 #endif
 557                 }
 558                 loginfo("Connection from %s:%d", addrbuf, port);
 559         }
 560
 561         alarm(init_timeout ? init_timeout : timeout);
 562         pktlen = packet_read_line(0, line, sizeof(line));
 563         alarm(0);
 564
 565         len = strlen(line);
 566         if (pktlen != len)
 567                 loginfo("Extended attributes (%d bytes) exist <%.*s>",
 568                         (int) pktlen - len,
 569                         (int) pktlen - len, line + len + 1);
 570         if (len && line[len-1] == '\n') {
 571                 line[--len] = 0;
 572                 pktlen--;
 573         }
 574
 575         /*
 576          * Initialize the path interpolation table for this connection.
 577          */
 578         interp_clear_table(interp_table, ARRAY_SIZE(interp_table));
 579         interp_set_entry(interp_table, INTERP_SLOT_PERCENT, "%");
 580
 581         if (len != pktlen) {
 582             parse_extra_args(interp_table, line + len + 1, pktlen - len - 1);
 583             fill_in_extra_table_entries(interp_table);
 584         }
 585
 586         for (i = 0; i < ARRAY_SIZE(daemon_service); i++) {
 587                 struct daemon_service *s = &(daemon_service[i]);
 588                 int namelen = strlen(s->name);
 589                 if (!prefixcmp(line, "git-") &&
 590                     !strncmp(s->name, line + 4, namelen) &&
 591                     line[namelen + 4] == ' ') {
 592                         /*
 593                          * Note: The directory here is probably context sensitive,
 594                          * and might depend on the actual service being performed.
 595                          */
 596                         interp_set_entry(interp_table,
 597                                          INTERP_SLOT_DIR, line + namelen + 5);
 598                         return run_service(interp_table, s);
 599                 }
 600         }
 601
 602         logerror("Protocol error: '%s'", line);
 603         return -1;
 604 }
 605
 606
 607 /*
 608  * We count spawned/reaped separately, just to avoid any
 609  * races when updating them from signals. The SIGCHLD handler
 610  * will only update children_reaped, and the fork logic will
 611  * only update children_spawned.
 612  *
 613  * MAX_CHILDREN should be a power-of-two to make the modulus
 614  * operation cheap. It should also be at least twice
 615  * the maximum number of connections we will ever allow.
 616  */
 617 #define MAX_CHILDREN 128
 618
 619 static int max_connections = 25;
 620
 621 /* These are updated by the signal handler */
 622 static volatile unsigned int children_reaped;
 623 static pid_t dead_child[MAX_CHILDREN];
 624
 625 /* These are updated by the main loop */
 626 static unsigned int children_spawned;
 627 static unsigned int children_deleted;
 628
 629 static struct child {
 630         pid_t pid;
 631         int addrlen;
 632         struct sockaddr_storage address;
 633 } live_child[MAX_CHILDREN];
 634
 635 static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
 636 {
 637         live_child[idx].pid = pid;
 638         live_child[idx].addrlen = addrlen;
 639         memcpy(&live_child[idx].address, addr, addrlen);
 640 }
 641
 642 /*
 643  * Walk from "deleted" to "spawned", and remove child "pid".
 644  *
 645  * We move everything up by one, since the new "deleted" will
 646  * be one higher.
 647  */
 648 static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
 649 {
 650         struct child n;
 651
 652         deleted %= MAX_CHILDREN;
 653         spawned %= MAX_CHILDREN;
 654         if (live_child[deleted].pid == pid) {
 655                 live_child[deleted].pid = -1;
 656                 return;
 657         }
 658         n = live_child[deleted];
 659         for (;;) {
 660                 struct child m;
 661                 deleted = (deleted + 1) % MAX_CHILDREN;
 662                 if (deleted == spawned)
 663                         die("could not find dead child %d\n", pid);
 664                 m = live_child[deleted];
 665                 live_child[deleted] = n;
 666                 if (m.pid == pid)
 667                         return;
 668                 n = m;
 669         }
 670 }
 671
 672 /*
 673  * This gets called if the number of connections grows
 674  * past "max_connections".
 675  *
 676  * We _should_ start off by searching for connections
 677  * from the same IP, and if there is some address wth
 678  * multiple connections, we should kill that first.
 679  *
 680  * As it is, we just "randomly" kill 25% of the connections,
 681  * and our pseudo-random generator sucks too. I have no
 682  * shame.
 683  *
 684  * Really, this is just a place-holder for a _real_ algorithm.
 685  */
 686 static void kill_some_children(int signo, unsigned start, unsigned stop)
 687 {
 688         start %= MAX_CHILDREN;
 689         stop %= MAX_CHILDREN;
 690         while (start != stop) {
 691                 if (!(start & 3))
 692                         kill(live_child[start].pid, signo);
 693                 start = (start + 1) % MAX_CHILDREN;
 694         }
 695 }
 696
 697 static void check_dead_children(void)
 698 {
 699         unsigned spawned, reaped, deleted;
 700
 701         spawned = children_spawned;
 702         reaped = children_reaped;
 703         deleted = children_deleted;
 704
 705         while (deleted < reaped) {
 706                 pid_t pid = dead_child[deleted % MAX_CHILDREN];
 707                 const char *dead = pid < 0 ? " (with error)" : "";
 708
 709                 if (pid < 0)
 710                         pid = -pid;
 711
 712                 /* XXX: Custom logging, since we don't wanna getpid() */
 713                 if (verbose) {
 714                         if (log_syslog)
 715                                 syslog(LOG_INFO, "[%d] Disconnected%s",
 716                                                 pid, dead);
 717                         else
 718                                 fprintf(stderr, "[%d] Disconnected%s\n",
 719                                                 pid, dead);
 720                 }
 721                 remove_child(pid, deleted, spawned);
 722                 deleted++;
 723         }
 724         children_deleted = deleted;
 725 }
 726
 727 static void check_max_connections(void)
 728 {
 729         for (;;) {
 730                 int active;
 731                 unsigned spawned, deleted;
 732
 733                 check_dead_children();
 734
 735                 spawned = children_spawned;
 736                 deleted = children_deleted;
 737
 738                 active = spawned - deleted;
 739                 if (active <= max_connections)
 740                         break;
 741
 742                 /* Kill some unstarted connections with SIGTERM */
 743                 kill_some_children(SIGTERM, deleted, spawned);
 744                 if (active <= max_connections << 1)
 745                         break;
 746
 747                 /* If the SIGTERM thing isn't helping use SIGKILL */
 748                 kill_some_children(SIGKILL, deleted, spawned);
 749                 sleep(1);
 750         }
 751 }
 752
 753 static void handle(int incoming, struct sockaddr *addr, int addrlen)
 754 {
 755         pid_t pid = fork();
 756
 757         if (pid) {
 758                 unsigned idx;
 759
 760                 close(incoming);
 761                 if (pid < 0)
 762                         return;
 763
 764                 idx = children_spawned % MAX_CHILDREN;
 765                 children_spawned++;
 766                 add_child(idx, pid, addr, addrlen);
 767
 768                 check_max_connections();
 769                 return;
 770         }
 771
 772         dup2(incoming, 0);
 773         dup2(incoming, 1);
 774         close(incoming);
 775
 776         exit(execute(addr));
 777 }
 778
 779 static void child_handler(int signo)
 780 {
 781         for (;;) {
 782                 int status;
 783                 pid_t pid = waitpid(-1, &status, WNOHANG);
 784
 785                 if (pid > 0) {
 786                         unsigned reaped = children_reaped;
 787                         if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
 788                                 pid = -pid;
 789                         dead_child[reaped % MAX_CHILDREN] = pid;
 790                         children_reaped = reaped + 1;
 791                         continue;
 792                 }
 793                 break;
 794         }
 795 }
 796
 797 static int set_reuse_addr(int sockfd)
 798 {
 799         int on = 1;
 800
 801         if (!reuseaddr)
 802                 return 0;
 803         return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
 804                           &on, sizeof(on));
 805 }
 806
 807 #ifndef NO_IPV6
 808
 809 static int socksetup(char *listen_addr, int listen_port, int **socklist_p)
 810 {
 811         int socknum = 0, *socklist = NULL;
 812         int maxfd = -1;
 813         char pbuf[NI_MAXSERV];
 814         struct addrinfo hints, *ai0, *ai;
 815         int gai;
 816         long flags;
 817
 818         sprintf(pbuf, "%d", listen_port);
 819         memset(&hints, 0, sizeof(hints));
 820         hints.ai_family = AF_UNSPEC;
 821         hints.ai_socktype = SOCK_STREAM;
 822         hints.ai_protocol = IPPROTO_TCP;
 823         hints.ai_flags = AI_PASSIVE;
 824
 825         gai = getaddrinfo(listen_addr, pbuf, &hints, &ai0);
 826         if (gai)
 827                 die("getaddrinfo() failed: %s\n", gai_strerror(gai));
 828
 829         for (ai = ai0; ai; ai = ai->ai_next) {
 830                 int sockfd;
 831
 832                 sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 833                 if (sockfd < 0)
 834                         continue;
 835                 if (sockfd >= FD_SETSIZE) {
 836                         error("too large socket descriptor.");
 837                         close(sockfd);
 838                         continue;
 839                 }
 840
 841 #ifdef IPV6_V6ONLY
 842                 if (ai->ai_family == AF_INET6) {
 843                         int on = 1;
 844                         setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
 845                                    &on, sizeof(on));
 846                         /* Note: error is not fatal */
 847                 }
 848 #endif
 849
 850                 if (set_reuse_addr(sockfd)) {
 851                         close(sockfd);
 852                         continue;
 853                 }
 854
 855                 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
 856                         close(sockfd);
 857                         continue;       /* not fatal */
 858                 }
 859                 if (listen(sockfd, 5) < 0) {
 860                         close(sockfd);
 861                         continue;       /* not fatal */
 862                 }
 863
 864                 flags = fcntl(sockfd, F_GETFD, 0);
 865                 if (flags >= 0)
 866                         fcntl(sockfd, F_SETFD, flags | FD_CLOEXEC);
 867
 868                 socklist = xrealloc(socklist, sizeof(int) * (socknum + 1));
 869                 socklist[socknum++] = sockfd;
 870
 871                 if (maxfd < sockfd)
 872                         maxfd = sockfd;
 873         }
 874
 875         freeaddrinfo(ai0);
 876
 877         *socklist_p = socklist;
 878         return socknum;
 879 }
 880
 881 #else /* NO_IPV6 */
 882
 883 static int socksetup(char *listen_addr, int listen_port, int **socklist_p)
 884 {
 885         struct sockaddr_in sin;
 886         int sockfd;
 887         long flags;
 888
 889         memset(&sin, 0, sizeof sin);
 890         sin.sin_family = AF_INET;
 891         sin.sin_port = htons(listen_port);
 892
 893         if (listen_addr) {
 894                 /* Well, host better be an IP address here. */
 895                 if (inet_pton(AF_INET, listen_addr, &sin.sin_addr.s_addr) <= 0)
 896                         return 0;
 897         } else {
 898                 sin.sin_addr.s_addr = htonl(INADDR_ANY);
 899         }
 900
 901         sockfd = socket(AF_INET, SOCK_STREAM, 0);
 902         if (sockfd < 0)
 903                 return 0;
 904
 905         if (set_reuse_addr(sockfd)) {
 906                 close(sockfd);
 907                 return 0;
 908         }
 909
 910         if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
 911                 close(sockfd);
 912                 return 0;
 913         }
 914
 915         if (listen(sockfd, 5) < 0) {
 916                 close(sockfd);
 917                 return 0;
 918         }
 919
 920         flags = fcntl(sockfd, F_GETFD, 0);
 921         if (flags >= 0)
 922                 fcntl(sockfd, F_SETFD, flags | FD_CLOEXEC);
 923
 924         *socklist_p = xmalloc(sizeof(int));
 925         **socklist_p = sockfd;
 926         return 1;
 927 }
 928
 929 #endif
 930
 931 static int service_loop(int socknum, int *socklist)
 932 {
 933         struct pollfd *pfd;
 934         int i;
 935
 936         pfd = xcalloc(socknum, sizeof(struct pollfd));
 937
 938         for (i = 0; i < socknum; i++) {
 939                 pfd[i].fd = socklist[i];
 940                 pfd[i].events = POLLIN;
 941         }
 942
 943         signal(SIGCHLD, child_handler);
 944
 945         for (;;) {
 946                 int i;
 947                 int timeout;
 948
 949                 /*
 950                  * This 1-sec timeout could lead to idly looping but it is
 951                  * here so that children culled in child_handler() are reported
 952                  * without too much delay.  We could probably set up a pipe
 953                  * to ourselves that we poll, and write to the fd from child_handler()
 954                  * to wake us up (and consume it when the poll() returns...
 955                  */
 956                 timeout = (children_spawned != children_deleted) ? 1000 : -1;
 957                 i = poll(pfd, socknum, timeout);
 958                 if (i < 0) {
 959                         if (errno != EINTR) {
 960                                 error("poll failed, resuming: %s",
 961                                       strerror(errno));
 962                                 sleep(1);
 963                         }
 964                         continue;
 965                 }
 966                 if (i == 0) {
 967                         check_dead_children();
 968                         continue;
 969                 }
 970
 971                 for (i = 0; i < socknum; i++) {
 972                         if (pfd[i].revents & POLLIN) {
 973                                 struct sockaddr_storage ss;
 974                                 unsigned int sslen = sizeof(ss);
 975                                 int incoming = accept(pfd[i].fd, (struct sockaddr *)&ss, &sslen);
 976                                 if (incoming < 0) {
 977                                         switch (errno) {
 978                                         case EAGAIN:
 979                                         case EINTR:
 980                                         case ECONNABORTED:
 981                                                 continue;
 982                                         default:
 983                                                 die("accept returned %s", strerror(errno));
 984                                         }
 985                                 }
 986                                 handle(incoming, (struct sockaddr *)&ss, sslen);
 987                         }
 988                 }
 989         }
 990 }
 991
 992 /* if any standard file descriptor is missing open it to /dev/null */
 993 static void sanitize_stdfds(void)
 994 {
 995         int fd = open("/dev/null", O_RDWR, 0);
 996         while (fd != -1 && fd < 2)
 997                 fd = dup(fd);
 998         if (fd == -1)
 999                 die("open /dev/null or dup failed: %s", strerror(errno));
1000         if (fd > 2)
1001                 close(fd);
1002 }
1003
1004 static void daemonize(void)
1005 {
1006         switch (fork()) {
1007                 case 0:
1008                         break;
1009                 case -1:
1010                         die("fork failed: %s", strerror(errno));
1011                 default:
1012                         exit(0);
1013         }
1014         if (setsid() == -1)
1015                 die("setsid failed: %s", strerror(errno));
1016         close(0);
1017         close(1);
1018         close(2);
1019         sanitize_stdfds();
1020 }
1021
1022 static void store_pid(const char *path)
1023 {
1024         FILE *f = fopen(path, "w");
1025         if (!f)
1026                 die("cannot open pid file %s: %s", path, strerror(errno));
1027         if (fprintf(f, "%d\n", getpid()) < 0 || fclose(f) != 0)
1028                 die("failed to write pid file %s: %s", path, strerror(errno));
1029 }
1030
1031 static int serve(char *listen_addr, int listen_port, struct passwd *pass, gid_t gid)
1032 {
1033         int socknum, *socklist;
1034
1035         socknum = socksetup(listen_addr, listen_port, &socklist);
1036         if (socknum == 0)
1037                 die("unable to allocate any listen sockets on host %s port %u",
1038                     listen_addr, listen_port);
1039
1040         if (pass && gid &&
1041             (initgroups(pass->pw_name, gid) || setgid (gid) ||
1042              setuid(pass->pw_uid)))
1043                 die("cannot drop privileges");
1044
1045         return service_loop(socknum, socklist);
1046 }
1047
1048 int main(int argc, char **argv)
1049 {
1050         int listen_port = 0;
1051         char *listen_addr = NULL;
1052         int inetd_mode = 0;
1053         const char *pid_file = NULL, *user_name = NULL, *group_name = NULL;
1054         int detach = 0;
1055         struct passwd *pass = NULL;
1056         struct group *group;
1057         gid_t gid = 0;
1058         int i;
1059
1060         /* Without this we cannot rely on waitpid() to tell
1061          * what happened to our children.
1062          */
1063         signal(SIGCHLD, SIG_DFL);
1064
1065         for (i = 1; i < argc; i++) {
1066                 char *arg = argv[i];
1067
1068                 if (!prefixcmp(arg, "--listen=")) {
1069                     char *p = arg + 9;
1070                     char *ph = listen_addr = xmalloc(strlen(arg + 9) + 1);
1071                     while (*p)
1072                         *ph++ = tolower(*p++);
1073                     *ph = 0;
1074                     continue;
1075                 }
1076                 if (!prefixcmp(arg, "--port=")) {
1077                         char *end;
1078                         unsigned long n;
1079                         n = strtoul(arg+7, &end, 0);
1080                         if (arg[7] && !*end) {
1081                                 listen_port = n;
1082                                 continue;
1083                         }
1084                 }
1085                 if (!strcmp(arg, "--inetd")) {
1086                         inetd_mode = 1;
1087                         log_syslog = 1;
1088                         continue;
1089                 }
1090                 if (!strcmp(arg, "--verbose")) {
1091                         verbose = 1;
1092                         continue;
1093                 }
1094                 if (!strcmp(arg, "--syslog")) {
1095                         log_syslog = 1;
1096                         continue;
1097                 }
1098                 if (!strcmp(arg, "--export-all")) {
1099                         export_all_trees = 1;
1100                         continue;
1101                 }
1102                 if (!prefixcmp(arg, "--timeout=")) {
1103                         timeout = atoi(arg+10);
1104                         continue;
1105                 }
1106                 if (!prefixcmp(arg, "--init-timeout=")) {
1107                         init_timeout = atoi(arg+15);
1108                         continue;
1109                 }
1110                 if (!strcmp(arg, "--strict-paths")) {
1111                         strict_paths = 1;
1112                         continue;
1113                 }
1114                 if (!prefixcmp(arg, "--base-path=")) {
1115                         base_path = arg+12;
1116                         continue;
1117                 }
1118                 if (!strcmp(arg, "--base-path-relaxed")) {
1119                         base_path_relaxed = 1;
1120                         continue;
1121                 }
1122                 if (!prefixcmp(arg, "--interpolated-path=")) {
1123                         interpolated_path = arg+20;
1124                         continue;
1125                 }
1126                 if (!strcmp(arg, "--reuseaddr")) {
1127                         reuseaddr = 1;
1128                         continue;
1129                 }
1130                 if (!strcmp(arg, "--user-path")) {
1131                         user_path = "";
1132                         continue;
1133                 }
1134                 if (!prefixcmp(arg, "--user-path=")) {
1135                         user_path = arg + 12;
1136                         continue;
1137                 }
1138                 if (!prefixcmp(arg, "--pid-file=")) {
1139                         pid_file = arg + 11;
1140                         continue;
1141                 }
1142                 if (!strcmp(arg, "--detach")) {
1143                         detach = 1;
1144                         log_syslog = 1;
1145                         continue;
1146                 }
1147                 if (!prefixcmp(arg, "--user=")) {
1148                         user_name = arg + 7;
1149                         continue;
1150                 }
1151                 if (!prefixcmp(arg, "--group=")) {
1152                         group_name = arg + 8;
1153                         continue;
1154                 }
1155                 if (!prefixcmp(arg, "--enable=")) {
1156                         enable_service(arg + 9, 1);
1157                         continue;
1158                 }
1159                 if (!prefixcmp(arg, "--disable=")) {
1160                         enable_service(arg + 10, 0);
1161                         continue;
1162                 }
1163                 if (!prefixcmp(arg, "--allow-override=")) {
1164                         make_service_overridable(arg + 17, 1);
1165                         continue;
1166                 }
1167                 if (!prefixcmp(arg, "--forbid-override=")) {
1168                         make_service_overridable(arg + 18, 0);
1169                         continue;
1170                 }
1171                 if (!strcmp(arg, "--")) {
1172                         ok_paths = &argv[i+1];
1173                         break;
1174                 } else if (arg[0] != '-') {
1175                         ok_paths = &argv[i];
1176                         break;
1177                 }
1178
1179                 usage(daemon_usage);
1180         }
1181
1182         if (log_syslog) {
1183                 openlog("git-daemon", 0, LOG_DAEMON);
1184                 set_die_routine(daemon_die);
1185         }
1186
1187         if (inetd_mode && (group_name || user_name))
1188                 die("--user and --group are incompatible with --inetd");
1189
1190         if (inetd_mode && (listen_port || listen_addr))
1191                 die("--listen= and --port= are incompatible with --inetd");
1192         else if (listen_port == 0)
1193                 listen_port = DEFAULT_GIT_PORT;
1194
1195         if (group_name && !user_name)
1196                 die("--group supplied without --user");
1197
1198         if (user_name) {
1199                 pass = getpwnam(user_name);
1200                 if (!pass)
1201                         die("user not found - %s", user_name);
1202
1203                 if (!group_name)
1204                         gid = pass->pw_gid;
1205                 else {
1206                         group = getgrnam(group_name);
1207                         if (!group)
1208                                 die("group not found - %s", group_name);
1209
1210                         gid = group->gr_gid;
1211                 }
1212         }
1213
1214         if (strict_paths && (!ok_paths || !*ok_paths))
1215                 die("option --strict-paths requires a whitelist");
1216
1217         if (base_path) {
1218                 struct stat st;
1219
1220                 if (stat(base_path, &st) || !S_ISDIR(st.st_mode))
1221                         die("base-path '%s' does not exist or "
1222                             "is not a directory", base_path);
1223         }
1224
1225         if (inetd_mode) {
1226                 struct sockaddr_storage ss;
1227                 struct sockaddr *peer = (struct sockaddr *)&ss;
1228                 socklen_t slen = sizeof(ss);
1229
1230                 freopen("/dev/null", "w", stderr);
1231
1232                 if (getpeername(0, peer, &slen))
1233                         peer = NULL;
1234
1235                 return execute(peer);
1236         }
1237
1238         if (detach)
1239                 daemonize();
1240         else
1241                 sanitize_stdfds();
1242
1243         if (pid_file)
1244                 store_pid(pid_file);
1245
1246         return serve(listen_addr, listen_port, pass, gid);
1247 }