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