sha1_file.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  *
   6  * This handles basic git sha1 object files - packing, unpacking,
   7  * creation etc.
   8  */
   9 #include "cache.h"
  10
  11 #ifndef O_NOATIME
  12 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  13 #define O_NOATIME 01000000
  14 #else
  15 #define O_NOATIME 0
  16 #endif
  17 #endif
  18
  19 static unsigned int sha1_file_open_flag = O_NOATIME;
  20
  21 static unsigned hexval(char c)
  22 {
  23         if (c >= '0' && c <= '9')
  24                 return c - '0';
  25         if (c >= 'a' && c <= 'f')
  26                 return c - 'a' + 10;
  27         if (c >= 'A' && c <= 'F')
  28                 return c - 'A' + 10;
  29         return ~0;
  30 }
  31
  32 int get_sha1_hex(const char *hex, unsigned char *sha1)
  33 {
  34         int i;
  35         for (i = 0; i < 20; i++) {
  36                 unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  37                 if (val & ~0xff)
  38                         return -1;
  39                 *sha1++ = val;
  40                 hex += 2;
  41         }
  42         return 0;
  43 }
  44
  45 static int get_sha1_file(const char *path, unsigned char *result)
  46 {
  47         char buffer[60];
  48         int fd = open(path, O_RDONLY);
  49         int len;
  50
  51         if (fd < 0)
  52                 return -1;
  53         len = read(fd, buffer, sizeof(buffer));
  54         close(fd);
  55         if (len < 40)
  56                 return -1;
  57         return get_sha1_hex(buffer, result);
  58 }
  59
  60 static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir;
  61 static void setup_git_env(void)
  62 {
  63         git_dir = gitenv(GIT_DIR_ENVIRONMENT);
  64         if (!git_dir)
  65                 git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
  66         git_object_dir = gitenv(DB_ENVIRONMENT);
  67         if (!git_object_dir) {
  68                 git_object_dir = xmalloc(strlen(git_dir) + 9);
  69                 sprintf(git_object_dir, "%s/objects", git_dir);
  70         }
  71         git_refs_dir = xmalloc(strlen(git_dir) + 6);
  72         sprintf(git_refs_dir, "%s/refs", git_dir);
  73         git_index_file = gitenv(INDEX_ENVIRONMENT);
  74         if (!git_index_file) {
  75                 git_index_file = xmalloc(strlen(git_dir) + 7);
  76                 sprintf(git_index_file, "%s/index", git_dir);
  77         }
  78 }
  79
  80 char *get_object_directory(void)
  81 {
  82         if (!git_object_dir)
  83                 setup_git_env();
  84         return git_object_dir;
  85 }
  86
  87 char *get_refs_directory(void)
  88 {
  89         if (!git_refs_dir)
  90                 setup_git_env();
  91         return git_refs_dir;
  92 }
  93
  94 char *get_index_file(void)
  95 {
  96         if (!git_index_file)
  97                 setup_git_env();
  98         return git_index_file;
  99 }
 100
 101 int get_sha1(const char *str, unsigned char *sha1)
 102 {
 103         static char pathname[PATH_MAX];
 104         static const char *prefix[] = {
 105                 "",
 106                 "refs",
 107                 "refs/tags",
 108                 "refs/heads",
 109                 "refs/snap",
 110                 NULL
 111         };
 112         const char **p;
 113
 114         if (!get_sha1_hex(str, sha1))
 115                 return 0;
 116
 117         if (!git_dir)
 118                 setup_git_env();
 119         for (p = prefix; *p; p++) {
 120                 snprintf(pathname, sizeof(pathname), "%s/%s/%s",
 121                          git_dir, *p, str);
 122                 if (!get_sha1_file(pathname, sha1))
 123                         return 0;
 124         }
 125
 126         return -1;
 127 }
 128
 129 char * sha1_to_hex(const unsigned char *sha1)
 130 {
 131         static char buffer[50];
 132         static const char hex[] = "0123456789abcdef";
 133         char *buf = buffer;
 134         int i;
 135
 136         for (i = 0; i < 20; i++) {
 137                 unsigned int val = *sha1++;
 138                 *buf++ = hex[val >> 4];
 139                 *buf++ = hex[val & 0xf];
 140         }
 141         return buffer;
 142 }
 143
 144 static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 145 {
 146         int i;
 147         for (i = 0; i < 20; i++) {
 148                 static char hex[] = "0123456789abcdef";
 149                 unsigned int val = sha1[i];
 150                 char *pos = pathbuf + i*2 + (i > 0);
 151                 *pos++ = hex[val >> 4];
 152                 *pos = hex[val & 0xf];
 153         }
 154 }
 155
 156 /*
 157  * NOTE! This returns a statically allocated buffer, so you have to be
 158  * careful about using it. Do a "strdup()" if you need to save the
 159  * filename.
 160  *
 161  * Also note that this returns the location for creating.  Reading
 162  * SHA1 file can happen from any alternate directory listed in the
 163  * DB_ENVIRONMENT environment variable if it is not found in
 164  * the primary object database.
 165  */
 166 char *sha1_file_name(const unsigned char *sha1)
 167 {
 168         static char *name, *base;
 169
 170         if (!base) {
 171                 const char *sha1_file_directory = get_object_directory();
 172                 int len = strlen(sha1_file_directory);
 173                 base = xmalloc(len + 60);
 174                 memcpy(base, sha1_file_directory, len);
 175                 memset(base+len, 0, 60);
 176                 base[len] = '/';
 177                 base[len+3] = '/';
 178                 name = base + len + 1;
 179         }
 180         fill_sha1_path(name, sha1);
 181         return base;
 182 }
 183
 184 static struct alternate_object_database {
 185         char *base;
 186         char *name;
 187 } *alt_odb;
 188
 189 /*
 190  * Prepare alternate object database registry.
 191  * alt_odb points at an array of struct alternate_object_database.
 192  * This array is terminated with an element that has both its base
 193  * and name set to NULL.  alt_odb[n] comes from n'th non-empty
 194  * element from colon separated ALTERNATE_DB_ENVIRONMENT environment
 195  * variable, and its base points at a statically allocated buffer
 196  * that contains "/the/directory/corresponding/to/.git/objects/...",
 197  * while its name points just after the slash at the end of
 198  * ".git/objects/" in the example above, and has enough space to hold
 199  * 40-byte hex SHA1, an extra slash for the first level indirection,
 200  * and the terminating NUL.
 201  * This function allocates the alt_odb array and all the strings
 202  * pointed by base fields of the array elements with one xmalloc();
 203  * the string pool immediately follows the array.
 204  */
 205 static void prepare_alt_odb(void)
 206 {
 207         int pass, totlen, i;
 208         const char *cp, *last;
 209         char *op = NULL;
 210         const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
 211
 212         /* The first pass counts how large an area to allocate to
 213          * hold the entire alt_odb structure, including array of
 214          * structs and path buffers for them.  The second pass fills
 215          * the structure and prepares the path buffers for use by
 216          * fill_sha1_path().
 217          */
 218         for (totlen = pass = 0; pass < 2; pass++) {
 219                 last = alt;
 220                 i = 0;
 221                 do {
 222                         cp = strchr(last, ':') ? : last + strlen(last);
 223                         if (last != cp) {
 224                                 /* 43 = 40-byte + 2 '/' + terminating NUL */
 225                                 int pfxlen = cp - last;
 226                                 int entlen = pfxlen + 43;
 227                                 if (pass == 0)
 228                                         totlen += entlen;
 229                                 else {
 230                                         alt_odb[i].base = op;
 231                                         alt_odb[i].name = op + pfxlen + 1;
 232                                         memcpy(op, last, pfxlen);
 233                                         op[pfxlen] = op[pfxlen + 3] = '/';
 234                                         op[entlen-1] = 0;
 235                                         op += entlen;
 236                                 }
 237                                 i++;
 238                         }
 239                         while (*cp && *cp == ':')
 240                                 cp++;
 241                         last = cp;
 242                 } while (*cp);
 243                 if (pass)
 244                         break;
 245                 alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
 246                 alt_odb[i].base = alt_odb[i].name = NULL;
 247                 op = (char*)(&alt_odb[i+1]);
 248         }
 249 }
 250
 251 static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 252 {
 253         int i;
 254         char *name = sha1_file_name(sha1);
 255
 256         if (!stat(name, st))
 257                 return name;
 258         if (!alt_odb)
 259                 prepare_alt_odb();
 260         for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
 261                 fill_sha1_path(name, sha1);
 262                 if (!stat(alt_odb[i].base, st))
 263                         return alt_odb[i].base;
 264         }
 265         return NULL;
 266 }
 267
 268 int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
 269 {
 270         char header[100];
 271         unsigned char real_sha1[20];
 272         SHA_CTX c;
 273
 274         SHA1_Init(&c);
 275         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 276         SHA1_Update(&c, map, size);
 277         SHA1_Final(real_sha1, &c);
 278         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 279 }
 280
 281 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 282 {
 283         struct stat st;
 284         void *map;
 285         int fd;
 286         char *filename = find_sha1_file(sha1, &st);
 287
 288         if (!filename) {
 289                 error("cannot map sha1 file %s", sha1_to_hex(sha1));
 290                 return NULL;
 291         }
 292
 293         fd = open(filename, O_RDONLY | sha1_file_open_flag);
 294         if (fd < 0) {
 295                 /* See if it works without O_NOATIME */
 296                 switch (sha1_file_open_flag) {
 297                 default:
 298                         fd = open(filename, O_RDONLY);
 299                         if (fd >= 0)
 300                                 break;
 301                 /* Fallthrough */
 302                 case 0:
 303                         perror(filename);
 304                         return NULL;
 305                 }
 306
 307                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 308                 sha1_file_open_flag = 0;
 309         }
 310         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 311         close(fd);
 312         if (-1 == (int)(long)map)
 313                 return NULL;
 314         *size = st.st_size;
 315         return map;
 316 }
 317
 318 int unpack_sha1_header(z_stream *stream, void *map, unsigned long mapsize, void *buffer, unsigned long size)
 319 {
 320         /* Get the data stream */
 321         memset(stream, 0, sizeof(*stream));
 322         stream->next_in = map;
 323         stream->avail_in = mapsize;
 324         stream->next_out = buffer;
 325         stream->avail_out = size;
 326
 327         inflateInit(stream);
 328         return inflate(stream, 0);
 329 }
 330
 331 void *unpack_sha1_rest(z_stream *stream, void *buffer, unsigned long size)
 332 {
 333         int bytes = strlen(buffer) + 1;
 334         unsigned char *buf = xmalloc(1+size);
 335
 336         memcpy(buf, buffer + bytes, stream->total_out - bytes);
 337         bytes = stream->total_out - bytes;
 338         if (bytes < size) {
 339                 stream->next_out = buf + bytes;
 340                 stream->avail_out = size - bytes;
 341                 while (inflate(stream, Z_FINISH) == Z_OK)
 342                         /* nothing */;
 343         }
 344         buf[size] = 0;
 345         inflateEnd(stream);
 346         return buf;
 347 }
 348
 349 /*
 350  * We used to just use "sscanf()", but that's actually way
 351  * too permissive for what we want to check. So do an anal
 352  * object header parse by hand.
 353  */
 354 int parse_sha1_header(char *hdr, char *type, unsigned long *sizep)
 355 {
 356         int i;
 357         unsigned long size;
 358
 359         /*
 360          * The type can be at most ten bytes (including the
 361          * terminating '\0' that we add), and is followed by
 362          * a space.
 363          */
 364         i = 10;
 365         for (;;) {
 366                 char c = *hdr++;
 367                 if (c == ' ')
 368                         break;
 369                 if (!--i)
 370                         return -1;
 371                 *type++ = c;
 372         }
 373         *type = 0;
 374
 375         /*
 376          * The length must follow immediately, and be in canonical
 377          * decimal format (ie "010" is not valid).
 378          */
 379         size = *hdr++ - '0';
 380         if (size > 9)
 381                 return -1;
 382         if (size) {
 383                 for (;;) {
 384                         unsigned long c = *hdr - '0';
 385                         if (c > 9)
 386                                 break;
 387                         hdr++;
 388                         size = size * 10 + c;
 389                 }
 390         }
 391         *sizep = size;
 392
 393         /*
 394          * The length must be followed by a zero byte
 395          */
 396         return *hdr ? -1 : 0;
 397 }
 398
 399 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 400 {
 401         int ret;
 402         z_stream stream;
 403         char hdr[8192];
 404
 405         ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 406         if (ret < Z_OK || parse_sha1_header(hdr, type, size) < 0)
 407                 return NULL;
 408
 409         return unpack_sha1_rest(&stream, hdr, *size);
 410 }
 411
 412 int sha1_file_size(const unsigned char *sha1, unsigned long *sizep)
 413 {
 414         int ret, status;
 415         unsigned long mapsize, size;
 416         void *map;
 417         z_stream stream;
 418         char hdr[64], type[20];
 419
 420         map = map_sha1_file(sha1, &mapsize);
 421         if (!map)
 422                 return -1;
 423         ret = unpack_sha1_header(&stream, map, mapsize, hdr, sizeof(hdr));
 424         if (ret < Z_OK || parse_sha1_header(hdr, type, &size) < 0)
 425                 status = -1;
 426         else {
 427                 status = 0;
 428                 *sizep = size;
 429         }
 430         inflateEnd(&stream);
 431         munmap(map, mapsize);
 432         return status;
 433 }
 434
 435 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 436 {
 437         unsigned long mapsize;
 438         void *map, *buf;
 439
 440         map = map_sha1_file(sha1, &mapsize);
 441         if (map) {
 442                 buf = unpack_sha1_file(map, mapsize, type, size);
 443                 munmap(map, mapsize);
 444                 return buf;
 445         }
 446         return NULL;
 447 }
 448
 449 void *read_object_with_reference(const unsigned char *sha1,
 450                                  const char *required_type,
 451                                  unsigned long *size,
 452                                  unsigned char *actual_sha1_return)
 453 {
 454         char type[20];
 455         void *buffer;
 456         unsigned long isize;
 457         unsigned char actual_sha1[20];
 458
 459         memcpy(actual_sha1, sha1, 20);
 460         while (1) {
 461                 int ref_length = -1;
 462                 const char *ref_type = NULL;
 463
 464                 buffer = read_sha1_file(actual_sha1, type, &isize);
 465                 if (!buffer)
 466                         return NULL;
 467                 if (!strcmp(type, required_type)) {
 468                         *size = isize;
 469                         if (actual_sha1_return)
 470                                 memcpy(actual_sha1_return, actual_sha1, 20);
 471                         return buffer;
 472                 }
 473                 /* Handle references */
 474                 else if (!strcmp(type, "commit"))
 475                         ref_type = "tree ";
 476                 else if (!strcmp(type, "tag"))
 477                         ref_type = "object ";
 478                 else {
 479                         free(buffer);
 480                         return NULL;
 481                 }
 482                 ref_length = strlen(ref_type);
 483
 484                 if (memcmp(buffer, ref_type, ref_length) ||
 485                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
 486                         free(buffer);
 487                         return NULL;
 488                 }
 489                 /* Now we have the ID of the referred-to object in
 490                  * actual_sha1.  Check again. */
 491         }
 492 }
 493
 494 int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 495 {
 496         int size;
 497         unsigned char *compressed;
 498         z_stream stream;
 499         unsigned char sha1[20];
 500         SHA_CTX c;
 501         char *filename;
 502         static char tmpfile[PATH_MAX];
 503         unsigned char hdr[50];
 504         int fd, hdrlen, ret;
 505
 506         /* Generate the header */
 507         hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
 508
 509         /* Sha1.. */
 510         SHA1_Init(&c);
 511         SHA1_Update(&c, hdr, hdrlen);
 512         SHA1_Update(&c, buf, len);
 513         SHA1_Final(sha1, &c);
 514
 515         if (returnsha1)
 516                 memcpy(returnsha1, sha1, 20);
 517
 518         filename = sha1_file_name(sha1);
 519         fd = open(filename, O_RDONLY);
 520         if (fd >= 0) {
 521                 /*
 522                  * FIXME!!! We might do collision checking here, but we'd
 523                  * need to uncompress the old file and check it. Later.
 524                  */
 525                 close(fd);
 526                 return 0;
 527         }
 528
 529         if (errno != ENOENT) {
 530                 fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
 531                 return -1;
 532         }
 533
 534         snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
 535
 536         fd = mkstemp(tmpfile);
 537         if (fd < 0) {
 538                 fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
 539                 return -1;
 540         }
 541
 542         /* Set it up */
 543         memset(&stream, 0, sizeof(stream));
 544         deflateInit(&stream, Z_BEST_COMPRESSION);
 545         size = deflateBound(&stream, len+hdrlen);
 546         compressed = xmalloc(size);
 547
 548         /* Compress it */
 549         stream.next_out = compressed;
 550         stream.avail_out = size;
 551
 552         /* First header.. */
 553         stream.next_in = hdr;
 554         stream.avail_in = hdrlen;
 555         while (deflate(&stream, 0) == Z_OK)
 556                 /* nothing */;
 557
 558         /* Then the data itself.. */
 559         stream.next_in = buf;
 560         stream.avail_in = len;
 561         while (deflate(&stream, Z_FINISH) == Z_OK)
 562                 /* nothing */;
 563         deflateEnd(&stream);
 564         size = stream.total_out;
 565
 566         if (write(fd, compressed, size) != size)
 567                 die("unable to write file");
 568         fchmod(fd, 0444);
 569         close(fd);
 570         free(compressed);
 571
 572         ret = link(tmpfile, filename);
 573         if (ret < 0) {
 574                 ret = errno;
 575
 576                 /*
 577                  * Coda hack - coda doesn't like cross-directory links,
 578                  * so we fall back to a rename, which will mean that it
 579                  * won't be able to check collisions, but that's not a
 580                  * big deal.
 581                  *
 582                  * When this succeeds, we just return 0. We have nothing
 583                  * left to unlink.
 584                  */
 585                 if (ret == EXDEV && !rename(tmpfile, filename))
 586                         return 0;
 587         }
 588         unlink(tmpfile);
 589         if (ret) {
 590                 if (ret != EEXIST) {
 591                         fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
 592                         return -1;
 593                 }
 594                 /* FIXME!!! Collision check here ? */
 595         }
 596
 597         return 0;
 598 }
 599
 600 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 601 {
 602         char *filename = sha1_file_name(sha1);
 603
 604         int local;
 605         z_stream stream;
 606         unsigned char real_sha1[20];
 607         unsigned char buf[4096];
 608         unsigned char discard[4096];
 609         int ret;
 610         SHA_CTX c;
 611
 612         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 613
 614         if (local < 0)
 615                 return error("Couldn't open %s\n", filename);
 616
 617         memset(&stream, 0, sizeof(stream));
 618
 619         inflateInit(&stream);
 620
 621         SHA1_Init(&c);
 622
 623         do {
 624                 ssize_t size;
 625                 size = read(fd, buf, 4096);
 626                 if (size <= 0) {
 627                         close(local);
 628                         unlink(filename);
 629                         if (!size)
 630                                 return error("Connection closed?");
 631                         perror("Reading from connection");
 632                         return -1;
 633                 }
 634                 write(local, buf, size);
 635                 stream.avail_in = size;
 636                 stream.next_in = buf;
 637                 do {
 638                         stream.next_out = discard;
 639                         stream.avail_out = sizeof(discard);
 640                         ret = inflate(&stream, Z_SYNC_FLUSH);
 641                         SHA1_Update(&c, discard, sizeof(discard) -
 642                                     stream.avail_out);
 643                 } while (stream.avail_in && ret == Z_OK);
 644
 645         } while (ret == Z_OK);
 646         inflateEnd(&stream);
 647
 648         close(local);
 649         SHA1_Final(real_sha1, &c);
 650         if (ret != Z_STREAM_END) {
 651                 unlink(filename);
 652                 return error("File %s corrupted", sha1_to_hex(sha1));
 653         }
 654         if (memcmp(sha1, real_sha1, 20)) {
 655                 unlink(filename);
 656                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 657         }
 658
 659         return 0;
 660 }
 661
 662 int has_sha1_file(const unsigned char *sha1)
 663 {
 664         struct stat st;
 665         return !!find_sha1_file(sha1, &st);
 666 }
 667
 668 int index_fd(unsigned char *sha1, int fd, struct stat *st)
 669 {
 670         unsigned long size = st->st_size;
 671         void *buf;
 672         int ret;
 673
 674         buf = "";
 675         if (size)
 676                 buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 677         close(fd);
 678         if ((int)(long)buf == -1)
 679                 return -1;
 680
 681         ret = write_sha1_file(buf, size, "blob", sha1);
 682         if (size)
 683                 munmap(buf, size);
 684         return ret;
 685 }