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