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 const char *sha1_file_directory = NULL;
  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 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 int get_parent(int index, const char *str, unsigned char *result)
  64 {
  65         unsigned char sha1[20];
  66         char *buffer;
  67         unsigned long size, offset;
  68         int ret;
  69
  70         if (get_sha1(str, sha1) < 0)
  71                 return -1;
  72         buffer = read_object_with_reference(sha1, "commit", &size, NULL);
  73         if (!buffer)
  74                 return -1;
  75         ret = -1;
  76         offset = 46;
  77         for (;;) {
  78                 if (offset + 48 > size)
  79                         break;
  80                 if (memcmp(buffer + offset, "parent ", 7))
  81                         break;
  82                 if (index > 0) {
  83                         offset += 48;
  84                         index--;
  85                         continue;
  86                 }
  87                 ret = get_sha1_hex(buffer + offset + 7, result);
  88                 break;
  89         }
  90         free(buffer);
  91         return ret;
  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 *gitdir;
 106         const char **p;
 107
 108         if (!get_sha1_hex(str, sha1))
 109                 return 0;
 110
 111         switch (*str) {
 112         case '/':
 113                 if (!get_sha1_file(str, sha1))
 114                         return 0;
 115                 break;
 116         case '-':
 117                 return get_parent(0, str+1, sha1);
 118         case '0' ... '9':
 119                 if (str[1] == '-')
 120                         return get_parent(*str - '0', str+2, sha1);
 121                 break;
 122         }
 123
 124         gitdir = ".git";
 125         for (p = prefix; *p; p++) {
 126                 snprintf(pathname, sizeof(pathname), "%s/%s/%s", gitdir, *p, str);
 127                 if (!get_sha1_file(pathname, sha1))
 128                         return 0;
 129         }
 130
 131         return -1;
 132 }
 133
 134 char * sha1_to_hex(const unsigned char *sha1)
 135 {
 136         static char buffer[50];
 137         static const char hex[] = "0123456789abcdef";
 138         char *buf = buffer;
 139         int i;
 140
 141         for (i = 0; i < 20; i++) {
 142                 unsigned int val = *sha1++;
 143                 *buf++ = hex[val >> 4];
 144                 *buf++ = hex[val & 0xf];
 145         }
 146         return buffer;
 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 char *sha1_file_name(const unsigned char *sha1)
 155 {
 156         int i;
 157         static char *name, *base;
 158
 159         if (!base) {
 160                 char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
 161                 int len = strlen(sha1_file_directory);
 162                 base = xmalloc(len + 60);
 163                 memcpy(base, sha1_file_directory, len);
 164                 memset(base+len, 0, 60);
 165                 base[len] = '/';
 166                 base[len+3] = '/';
 167                 name = base + len + 1;
 168         }
 169         for (i = 0; i < 20; i++) {
 170                 static char hex[] = "0123456789abcdef";
 171                 unsigned int val = sha1[i];
 172                 char *pos = name + i*2 + (i > 0);
 173                 *pos++ = hex[val >> 4];
 174                 *pos = hex[val & 0xf];
 175         }
 176         return base;
 177 }
 178
 179 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
 180 {
 181         char header[100];
 182         unsigned char real_sha1[20];
 183         SHA_CTX c;
 184
 185         SHA1_Init(&c);
 186         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 187         SHA1_Update(&c, map, size);
 188         SHA1_Final(real_sha1, &c);
 189         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 190 }
 191
 192 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 193 {
 194         char *filename = sha1_file_name(sha1);
 195         struct stat st;
 196         void *map;
 197         int fd;
 198
 199         fd = open(filename, O_RDONLY | sha1_file_open_flag);
 200         if (fd < 0) {
 201                 /* See if it works without O_NOATIME */
 202                 switch (sha1_file_open_flag) {
 203                 default:
 204                         fd = open(filename, O_RDONLY);
 205                         if (fd >= 0)
 206                                 break;
 207                 /* Fallthrough */
 208                 case 0:
 209                         perror(filename);
 210                         return NULL;
 211                 }
 212
 213                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 214                 sha1_file_open_flag = 0;
 215         }
 216         if (fstat(fd, &st) < 0) {
 217                 close(fd);
 218                 return NULL;
 219         }
 220         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 221         close(fd);
 222         if (-1 == (int)(long)map)
 223                 return NULL;
 224         *size = st.st_size;
 225         return map;
 226 }
 227
 228 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 229 {
 230         int ret, bytes;
 231         z_stream stream;
 232         char buffer[8192];
 233         char *buf;
 234
 235         /* Get the data stream */
 236         memset(&stream, 0, sizeof(stream));
 237         stream.next_in = map;
 238         stream.avail_in = mapsize;
 239         stream.next_out = buffer;
 240         stream.avail_out = sizeof(buffer);
 241
 242         inflateInit(&stream);
 243         ret = inflate(&stream, 0);
 244         if (ret < Z_OK)
 245                 return NULL;
 246         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 247                 return NULL;
 248
 249         bytes = strlen(buffer) + 1;
 250         buf = xmalloc(*size);
 251
 252         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 253         bytes = stream.total_out - bytes;
 254         if (bytes < *size && ret == Z_OK) {
 255                 stream.next_out = buf + bytes;
 256                 stream.avail_out = *size - bytes;
 257                 while (inflate(&stream, Z_FINISH) == Z_OK)
 258                         /* nothing */;
 259         }
 260         inflateEnd(&stream);
 261         return buf;
 262 }
 263
 264 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 265 {
 266         unsigned long mapsize;
 267         void *map, *buf;
 268
 269         map = map_sha1_file(sha1, &mapsize);
 270         if (map) {
 271                 buf = unpack_sha1_file(map, mapsize, type, size);
 272                 munmap(map, mapsize);
 273                 return buf;
 274         }
 275         return NULL;
 276 }
 277
 278 void *read_object_with_reference(const unsigned char *sha1,
 279                                  const unsigned char *required_type,
 280                                  unsigned long *size,
 281                                  unsigned char *actual_sha1_return)
 282 {
 283         char type[20];
 284         void *buffer;
 285         unsigned long isize;
 286         unsigned char actual_sha1[20];
 287
 288         memcpy(actual_sha1, sha1, 20);
 289         while (1) {
 290                 int ref_length = -1;
 291                 const char *ref_type = NULL;
 292
 293                 buffer = read_sha1_file(actual_sha1, type, &isize);
 294                 if (!buffer)
 295                         return NULL;
 296                 if (!strcmp(type, required_type)) {
 297                         *size = isize;
 298                         if (actual_sha1_return)
 299                                 memcpy(actual_sha1_return, actual_sha1, 20);
 300                         return buffer;
 301                 }
 302                 /* Handle references */
 303                 else if (!strcmp(type, "commit"))
 304                         ref_type = "tree ";
 305                 else if (!strcmp(type, "tag"))
 306                         ref_type = "object ";
 307                 else {
 308                         free(buffer);
 309                         return NULL;
 310                 }
 311                 ref_length = strlen(ref_type);
 312
 313                 if (memcmp(buffer, ref_type, ref_length) ||
 314                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
 315                         free(buffer);
 316                         return NULL;
 317                 }
 318                 /* Now we have the ID of the referred-to object in
 319                  * actual_sha1.  Check again. */
 320         }
 321 }
 322
 323 int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 324 {
 325         int size;
 326         char *compressed;
 327         z_stream stream;
 328         unsigned char sha1[20];
 329         SHA_CTX c;
 330         char *filename;
 331         char hdr[50];
 332         int fd, hdrlen;
 333
 334         /* Generate the header */
 335         hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
 336
 337         /* Sha1.. */
 338         SHA1_Init(&c);
 339         SHA1_Update(&c, hdr, hdrlen);
 340         SHA1_Update(&c, buf, len);
 341         SHA1_Final(sha1, &c);
 342
 343         if (returnsha1)
 344                 memcpy(returnsha1, sha1, 20);
 345
 346         filename = sha1_file_name(sha1);
 347         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 348         if (fd < 0) {
 349                 if (errno != EEXIST)
 350                         return -1;
 351
 352                 /*
 353                  * We might do collision checking here, but we'd need to
 354                  * uncompress the old file and check it. Later.
 355                  */
 356                 return 0;
 357         }
 358
 359         /* Set it up */
 360         memset(&stream, 0, sizeof(stream));
 361         deflateInit(&stream, Z_BEST_COMPRESSION);
 362         size = deflateBound(&stream, len+hdrlen);
 363         compressed = xmalloc(size);
 364
 365         /* Compress it */
 366         stream.next_out = compressed;
 367         stream.avail_out = size;
 368
 369         /* First header.. */
 370         stream.next_in = hdr;
 371         stream.avail_in = hdrlen;
 372         while (deflate(&stream, 0) == Z_OK)
 373                 /* nothing */
 374
 375         /* Then the data itself.. */
 376         stream.next_in = buf;
 377         stream.avail_in = len;
 378         while (deflate(&stream, Z_FINISH) == Z_OK)
 379                 /* nothing */;
 380         deflateEnd(&stream);
 381         size = stream.total_out;
 382
 383         if (write(fd, compressed, size) != size)
 384                 die("unable to write file");
 385         close(fd);
 386
 387         return 0;
 388 }
 389
 390 static inline int collision_check(char *filename, void *buf, unsigned int size)
 391 {
 392 #ifdef COLLISION_CHECK
 393         void *map;
 394         int fd = open(filename, O_RDONLY);
 395         struct stat st;
 396         int cmp;
 397
 398         /* Unreadable object, or object went away? Strange. */
 399         if (fd < 0)
 400                 return -1;
 401
 402         if (fstat(fd, &st) < 0 || size != st.st_size)
 403                 return -1;
 404
 405         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 406         close(fd);
 407         if (map == MAP_FAILED)
 408                 return -1;
 409         cmp = memcmp(buf, map, size);
 410         munmap(map, size);
 411         if (cmp)
 412                 return -1;
 413 #endif
 414         return 0;
 415 }
 416
 417 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 418 {
 419         char *filename = sha1_file_name(sha1);
 420         int fd;
 421
 422         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 423         if (fd < 0) {
 424                 if (errno != EEXIST)
 425                         return -1;
 426                 if (collision_check(filename, buf, size))
 427                         return error("SHA1 collision detected!"
 428                                         " This is bad, bad, BAD!\a\n");
 429                 return 0;
 430         }
 431         write(fd, buf, size);
 432         close(fd);
 433         return 0;
 434 }
 435
 436 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 437 {
 438         char *filename = sha1_file_name(sha1);
 439
 440         int local;
 441         z_stream stream;
 442         unsigned char real_sha1[20];
 443         char buf[4096];
 444         char discard[4096];
 445         int ret;
 446         SHA_CTX c;
 447
 448         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 449
 450         if (local < 0)
 451                 return error("Couldn't open %s\n", filename);
 452
 453         memset(&stream, 0, sizeof(stream));
 454
 455         inflateInit(&stream);
 456
 457         SHA1_Init(&c);
 458
 459         do {
 460                 ssize_t size;
 461                 size = read(fd, buf, 4096);
 462                 if (size <= 0) {
 463                         close(local);
 464                         unlink(filename);
 465                         if (!size)
 466                                 return error("Connection closed?");
 467                         perror("Reading from connection");
 468                         return -1;
 469                 }
 470                 write(local, buf, size);
 471                 stream.avail_in = size;
 472                 stream.next_in = buf;
 473                 do {
 474                         stream.next_out = discard;
 475                         stream.avail_out = sizeof(discard);
 476                         ret = inflate(&stream, Z_SYNC_FLUSH);
 477                         SHA1_Update(&c, discard, sizeof(discard) -
 478                                     stream.avail_out);
 479                 } while (stream.avail_in && ret == Z_OK);
 480
 481         } while (ret == Z_OK);
 482         inflateEnd(&stream);
 483
 484         close(local);
 485         SHA1_Final(real_sha1, &c);
 486         if (ret != Z_STREAM_END) {
 487                 unlink(filename);
 488                 return error("File %s corrupted", sha1_to_hex(sha1));
 489         }
 490         if (memcmp(sha1, real_sha1, 20)) {
 491                 unlink(filename);
 492                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 493         }
 494
 495         return 0;
 496 }
 497
 498 int has_sha1_file(const unsigned char *sha1)
 499 {
 500         char *filename = sha1_file_name(sha1);
 501         struct stat st;
 502
 503         if (!stat(filename, &st))
 504                 return 1;
 505         return 0;
 506 }