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 "cache.h"
  11
  12 #ifndef O_NOATIME
  13 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
  14 #define O_NOATIME 01000000
  15 #else
  16 #define O_NOATIME 0
  17 #endif
  18 #endif
  19
  20 static unsigned int sha1_file_open_flag = O_NOATIME;
  21
  22 static unsigned hexval(char c)
  23 {
  24         if (c >= '0' && c <= '9')
  25                 return c - '0';
  26         if (c >= 'a' && c <= 'f')
  27                 return c - 'a' + 10;
  28         if (c >= 'A' && c <= 'F')
  29                 return c - 'A' + 10;
  30         return ~0;
  31 }
  32
  33 int get_sha1_hex(const char *hex, unsigned char *sha1)
  34 {
  35         int i;
  36         for (i = 0; i < 20; i++) {
  37                 unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  38                 if (val & ~0xff)
  39                         return -1;
  40                 *sha1++ = val;
  41                 hex += 2;
  42         }
  43         return 0;
  44 }
  45
  46 int get_sha1_file(const char *path, unsigned char *result)
  47 {
  48         char buffer[60];
  49         int fd = open(path, O_RDONLY);
  50         int len;
  51
  52         if (fd < 0)
  53                 return -1;
  54         len = read(fd, buffer, sizeof(buffer));
  55         close(fd);
  56         if (len < 40)
  57                 return -1;
  58         return get_sha1_hex(buffer, result);
  59 }
  60
  61 int get_sha1(const char *str, unsigned char *sha1)
  62 {
  63         static char pathname[PATH_MAX];
  64         static const char *prefix[] = {
  65                 "",
  66                 "refs",
  67                 "refs/tags",
  68                 "refs/heads",
  69                 "refs/snap",
  70                 NULL
  71         };
  72         const char *gitdir;
  73         const char **p;
  74
  75         if (!get_sha1_hex(str, sha1))
  76                 return 0;
  77
  78         gitdir = ".git";
  79         for (p = prefix; *p; p++) {
  80                 snprintf(pathname, sizeof(pathname), "%s/%s/%s", gitdir, *p, str);
  81                 if (!get_sha1_file(pathname, sha1))
  82                         return 0;
  83         }
  84
  85         return -1;
  86 }
  87
  88 char * sha1_to_hex(const unsigned char *sha1)
  89 {
  90         static char buffer[50];
  91         static const char hex[] = "0123456789abcdef";
  92         char *buf = buffer;
  93         int i;
  94
  95         for (i = 0; i < 20; i++) {
  96                 unsigned int val = *sha1++;
  97                 *buf++ = hex[val >> 4];
  98                 *buf++ = hex[val & 0xf];
  99         }
 100         return buffer;
 101 }
 102
 103 static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
 104 {
 105         int i;
 106         for (i = 0; i < 20; i++) {
 107                 static char hex[] = "0123456789abcdef";
 108                 unsigned int val = sha1[i];
 109                 char *pos = pathbuf + i*2 + (i > 0);
 110                 *pos++ = hex[val >> 4];
 111                 *pos = hex[val & 0xf];
 112         }
 113 }
 114
 115 /*
 116  * NOTE! This returns a statically allocated buffer, so you have to be
 117  * careful about using it. Do a "strdup()" if you need to save the
 118  * filename.
 119  *
 120  * Also note that this returns the location for creating.  Reading
 121  * SHA1 file can happen from any alternate directory listed in the
 122  * SHA1_FILE_DIRECTORIES environment variable if it is not found in
 123  * the primary object database.
 124  */
 125 char *sha1_file_name(const unsigned char *sha1)
 126 {
 127         static char *name, *base;
 128
 129         if (!base) {
 130                 char *sha1_file_directory = get_object_directory();
 131                 int len = strlen(sha1_file_directory);
 132                 base = xmalloc(len + 60);
 133                 memcpy(base, sha1_file_directory, len);
 134                 memset(base+len, 0, 60);
 135                 base[len] = '/';
 136                 base[len+3] = '/';
 137                 name = base + len + 1;
 138         }
 139         fill_sha1_path(name, sha1);
 140         return base;
 141 }
 142
 143 static struct alternate_object_database
 144 {
 145         char *base;
 146         char *name;
 147 } *alt_odb;
 148
 149 static void prepare_alt_odb(void)
 150 {
 151         int pass, totlen, i;
 152         void *buf;
 153         const char *cp, *last;
 154         char *op = 0;
 155         const char *alt = getenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
 156
 157         for (totlen = pass = 0; pass < 2; pass++) {
 158                 last = alt;
 159                 i = 0;
 160                 do {
 161                         cp = strchr(last, ':') ? : last + strlen(last);
 162                         if (last != cp) {
 163                                 /* 43 = 40-byte + 2 '/' + terminating NUL */
 164                                 int pfxlen = cp - last;
 165                                 int entlen = pfxlen + 43;
 166                                 if (pass == 0)
 167                                         totlen += entlen;
 168                                 else {
 169                                         alt_odb[i].base = op;
 170                                         alt_odb[i].name = op + pfxlen + 1;
 171                                         memcpy(op, last, pfxlen);
 172                                         op[pfxlen] = op[pfxlen + 3] = '/';
 173                                         op[entlen-1] = 0;
 174                                         op += entlen;
 175                                 }
 176                                 i++;
 177                         }
 178                         while (*cp && *cp == ':')
 179                                 cp++;
 180                         last = cp;
 181                 } while (*cp);
 182                 if (pass)
 183                         break;
 184                 alt_odb = buf = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
 185                 alt_odb[i].base = alt_odb[i].name = 0;
 186                 op = (char*)(&alt_odb[i+1]);
 187         }
 188 }
 189
 190 static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 191 {
 192         int i;
 193         char *name = sha1_file_name(sha1);
 194
 195         if (!stat(name, st))
 196                 return name;
 197         if (!alt_odb)
 198                 prepare_alt_odb();
 199         for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
 200                 fill_sha1_path(name, sha1);
 201                 if (!stat(alt_odb[i].base, st))
 202                         return alt_odb[i].base;
 203         }
 204         return NULL;
 205 }
 206
 207 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
 208 {
 209         char header[100];
 210         unsigned char real_sha1[20];
 211         SHA_CTX c;
 212
 213         SHA1_Init(&c);
 214         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 215         SHA1_Update(&c, map, size);
 216         SHA1_Final(real_sha1, &c);
 217         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 218 }
 219
 220 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 221 {
 222         struct stat st;
 223         void *map;
 224         int fd;
 225         char *filename = find_sha1_file(sha1, &st);
 226
 227         if (!filename) {
 228                 error("cannot map sha1 file %s", sha1_to_hex(sha1));
 229                 return NULL;
 230         }
 231
 232         fd = open(filename, O_RDONLY | sha1_file_open_flag);
 233         if (fd < 0) {
 234                 /* See if it works without O_NOATIME */
 235                 switch (sha1_file_open_flag) {
 236                 default:
 237                         fd = open(filename, O_RDONLY);
 238                         if (fd >= 0)
 239                                 break;
 240                 /* Fallthrough */
 241                 case 0:
 242                         perror(filename);
 243                         return NULL;
 244                 }
 245
 246                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 247                 sha1_file_open_flag = 0;
 248         }
 249         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 250         close(fd);
 251         if (-1 == (int)(long)map)
 252                 return NULL;
 253         *size = st.st_size;
 254         return map;
 255 }
 256
 257 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 258 {
 259         int ret, bytes;
 260         z_stream stream;
 261         char buffer[8192];
 262         char *buf;
 263
 264         /* Get the data stream */
 265         memset(&stream, 0, sizeof(stream));
 266         stream.next_in = map;
 267         stream.avail_in = mapsize;
 268         stream.next_out = buffer;
 269         stream.avail_out = sizeof(buffer);
 270
 271         inflateInit(&stream);
 272         ret = inflate(&stream, 0);
 273         if (ret < Z_OK)
 274                 return NULL;
 275         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 276                 return NULL;
 277
 278         bytes = strlen(buffer) + 1;
 279         buf = xmalloc(*size);
 280
 281         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 282         bytes = stream.total_out - bytes;
 283         if (bytes < *size && ret == Z_OK) {
 284                 stream.next_out = buf + bytes;
 285                 stream.avail_out = *size - bytes;
 286                 while (inflate(&stream, Z_FINISH) == Z_OK)
 287                         /* nothing */;
 288         }
 289         inflateEnd(&stream);
 290         return buf;
 291 }
 292
 293 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 294 {
 295         unsigned long mapsize;
 296         void *map, *buf;
 297
 298         map = map_sha1_file(sha1, &mapsize);
 299         if (map) {
 300                 buf = unpack_sha1_file(map, mapsize, type, size);
 301                 munmap(map, mapsize);
 302                 return buf;
 303         }
 304         return NULL;
 305 }
 306
 307 void *read_object_with_reference(const unsigned char *sha1,
 308                                  const unsigned char *required_type,
 309                                  unsigned long *size,
 310                                  unsigned char *actual_sha1_return)
 311 {
 312         char type[20];
 313         void *buffer;
 314         unsigned long isize;
 315         unsigned char actual_sha1[20];
 316
 317         memcpy(actual_sha1, sha1, 20);
 318         while (1) {
 319                 int ref_length = -1;
 320                 const char *ref_type = NULL;
 321
 322                 buffer = read_sha1_file(actual_sha1, type, &isize);
 323                 if (!buffer)
 324                         return NULL;
 325                 if (!strcmp(type, required_type)) {
 326                         *size = isize;
 327                         if (actual_sha1_return)
 328                                 memcpy(actual_sha1_return, actual_sha1, 20);
 329                         return buffer;
 330                 }
 331                 /* Handle references */
 332                 else if (!strcmp(type, "commit"))
 333                         ref_type = "tree ";
 334                 else if (!strcmp(type, "tag"))
 335                         ref_type = "object ";
 336                 else {
 337                         free(buffer);
 338                         return NULL;
 339                 }
 340                 ref_length = strlen(ref_type);
 341
 342                 if (memcmp(buffer, ref_type, ref_length) ||
 343                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
 344                         free(buffer);
 345                         return NULL;
 346                 }
 347                 /* Now we have the ID of the referred-to object in
 348                  * actual_sha1.  Check again. */
 349         }
 350 }
 351
 352 int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 353 {
 354         int size;
 355         char *compressed;
 356         z_stream stream;
 357         unsigned char sha1[20];
 358         SHA_CTX c;
 359         char *filename;
 360         static char tmpfile[PATH_MAX];
 361         char hdr[50];
 362         int fd, hdrlen, ret;
 363
 364         /* Generate the header */
 365         hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
 366
 367         /* Sha1.. */
 368         SHA1_Init(&c);
 369         SHA1_Update(&c, hdr, hdrlen);
 370         SHA1_Update(&c, buf, len);
 371         SHA1_Final(sha1, &c);
 372
 373         if (returnsha1)
 374                 memcpy(returnsha1, sha1, 20);
 375
 376         filename = sha1_file_name(sha1);
 377         fd = open(filename, O_RDONLY);
 378         if (fd >= 0) {
 379                 /*
 380                  * FIXME!!! We might do collision checking here, but we'd
 381                  * need to uncompress the old file and check it. Later.
 382                  */
 383                 close(fd);
 384                 return 0;
 385         }
 386
 387         if (errno != ENOENT) {
 388                 fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
 389                 return -1;
 390         }
 391
 392         snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
 393
 394         fd = mkstemp(tmpfile);
 395         if (fd < 0) {
 396                 fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
 397                 return -1;
 398         }
 399
 400         /* Set it up */
 401         memset(&stream, 0, sizeof(stream));
 402         deflateInit(&stream, Z_BEST_COMPRESSION);
 403         size = deflateBound(&stream, len+hdrlen);
 404         compressed = xmalloc(size);
 405
 406         /* Compress it */
 407         stream.next_out = compressed;
 408         stream.avail_out = size;
 409
 410         /* First header.. */
 411         stream.next_in = hdr;
 412         stream.avail_in = hdrlen;
 413         while (deflate(&stream, 0) == Z_OK)
 414                 /* nothing */
 415
 416         /* Then the data itself.. */
 417         stream.next_in = buf;
 418         stream.avail_in = len;
 419         while (deflate(&stream, Z_FINISH) == Z_OK)
 420                 /* nothing */;
 421         deflateEnd(&stream);
 422         size = stream.total_out;
 423
 424         if (write(fd, compressed, size) != size)
 425                 die("unable to write file");
 426         fchmod(fd, 0444);
 427         close(fd);
 428
 429         ret = link(tmpfile, filename);
 430         if (ret < 0) {
 431                 ret = errno;
 432
 433                 /*
 434                  * Coda hack - coda doesn't like cross-directory links,
 435                  * so we fall back to a rename, which will mean that it
 436                  * won't be able to check collisions, but that's not a
 437                  * big deal.
 438                  *
 439                  * When this succeeds, we just return 0. We have nothing
 440                  * left to unlink.
 441                  */
 442                 if (ret == EXDEV && !rename(tmpfile, filename))
 443                         return 0;
 444         }
 445         unlink(tmpfile);
 446         if (ret) {
 447                 if (ret != EEXIST) {
 448                         fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
 449                         return -1;
 450                 }
 451                 /* FIXME!!! Collision check here ? */
 452         }
 453
 454         return 0;
 455 }
 456
 457 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 458 {
 459         char *filename = sha1_file_name(sha1);
 460
 461         int local;
 462         z_stream stream;
 463         unsigned char real_sha1[20];
 464         char buf[4096];
 465         char discard[4096];
 466         int ret;
 467         SHA_CTX c;
 468
 469         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 470
 471         if (local < 0)
 472                 return error("Couldn't open %s\n", filename);
 473
 474         memset(&stream, 0, sizeof(stream));
 475
 476         inflateInit(&stream);
 477
 478         SHA1_Init(&c);
 479
 480         do {
 481                 ssize_t size;
 482                 size = read(fd, buf, 4096);
 483                 if (size <= 0) {
 484                         close(local);
 485                         unlink(filename);
 486                         if (!size)
 487                                 return error("Connection closed?");
 488                         perror("Reading from connection");
 489                         return -1;
 490                 }
 491                 write(local, buf, size);
 492                 stream.avail_in = size;
 493                 stream.next_in = buf;
 494                 do {
 495                         stream.next_out = discard;
 496                         stream.avail_out = sizeof(discard);
 497                         ret = inflate(&stream, Z_SYNC_FLUSH);
 498                         SHA1_Update(&c, discard, sizeof(discard) -
 499                                     stream.avail_out);
 500                 } while (stream.avail_in && ret == Z_OK);
 501
 502         } while (ret == Z_OK);
 503         inflateEnd(&stream);
 504
 505         close(local);
 506         SHA1_Final(real_sha1, &c);
 507         if (ret != Z_STREAM_END) {
 508                 unlink(filename);
 509                 return error("File %s corrupted", sha1_to_hex(sha1));
 510         }
 511         if (memcmp(sha1, real_sha1, 20)) {
 512                 unlink(filename);
 513                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 514         }
 515
 516         return 0;
 517 }
 518
 519 int has_sha1_file(const unsigned char *sha1)
 520 {
 521         struct stat st;
 522         return !!find_sha1_file(sha1, &st);
 523 }
 524
 525 int index_fd(unsigned char *sha1, int fd, struct stat *st)
 526 {
 527         unsigned long size = st->st_size;
 528         void *buf;
 529         int ret;
 530
 531         buf = "";
 532         if (size)
 533                 buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 534         close(fd);
 535         if ((int)(long)buf == -1)
 536                 return -1;
 537
 538         ret = write_sha1_file(buf, size, "blob", sha1);
 539         if (size)
 540                 munmap(buf, size);
 541         return ret;
 542 }