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