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 int get_sha1(const char *str, unsigned char *sha1)
  64 {
  65         static char pathname[PATH_MAX];
  66
  67         if (!get_sha1_hex(str, sha1))
  68                 return 0;
  69         if (!get_sha1_file(str, sha1))
  70                 return 0;
  71         snprintf(pathname, sizeof(pathname), ".git/%s", str);
  72         if (!get_sha1_file(pathname, sha1))
  73                 return 0;
  74         return -1;
  75 }
  76
  77 char * sha1_to_hex(const unsigned char *sha1)
  78 {
  79         static char buffer[50];
  80         static const char hex[] = "0123456789abcdef";
  81         char *buf = buffer;
  82         int i;
  83
  84         for (i = 0; i < 20; i++) {
  85                 unsigned int val = *sha1++;
  86                 *buf++ = hex[val >> 4];
  87                 *buf++ = hex[val & 0xf];
  88         }
  89         return buffer;
  90 }
  91
  92 /*
  93  * NOTE! This returns a statically allocated buffer, so you have to be
  94  * careful about using it. Do a "strdup()" if you need to save the
  95  * filename.
  96  */
  97 char *sha1_file_name(const unsigned char *sha1)
  98 {
  99         int i;
 100         static char *name, *base;
 101
 102         if (!base) {
 103                 char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
 104                 int len = strlen(sha1_file_directory);
 105                 base = xmalloc(len + 60);
 106                 memcpy(base, sha1_file_directory, len);
 107                 memset(base+len, 0, 60);
 108                 base[len] = '/';
 109                 base[len+3] = '/';
 110                 name = base + len + 1;
 111         }
 112         for (i = 0; i < 20; i++) {
 113                 static char hex[] = "0123456789abcdef";
 114                 unsigned int val = sha1[i];
 115                 char *pos = name + i*2 + (i > 0);
 116                 *pos++ = hex[val >> 4];
 117                 *pos = hex[val & 0xf];
 118         }
 119         return base;
 120 }
 121
 122 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
 123 {
 124         char header[100];
 125         unsigned char real_sha1[20];
 126         SHA_CTX c;
 127
 128         SHA1_Init(&c);
 129         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 130         SHA1_Update(&c, map, size);
 131         SHA1_Final(real_sha1, &c);
 132         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 133 }
 134
 135 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 136 {
 137         char *filename = sha1_file_name(sha1);
 138         struct stat st;
 139         void *map;
 140         int fd;
 141
 142         fd = open(filename, O_RDONLY | sha1_file_open_flag);
 143         if (fd < 0) {
 144                 /* See if it works without O_NOATIME */
 145                 switch (sha1_file_open_flag) {
 146                 default:
 147                         fd = open(filename, O_RDONLY);
 148                         if (fd >= 0)
 149                                 break;
 150                 /* Fallthrough */
 151                 case 0:
 152                         perror(filename);
 153                         return NULL;
 154                 }
 155
 156                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 157                 sha1_file_open_flag = 0;
 158         }
 159         if (fstat(fd, &st) < 0) {
 160                 close(fd);
 161                 return NULL;
 162         }
 163         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 164         close(fd);
 165         if (-1 == (int)(long)map)
 166                 return NULL;
 167         *size = st.st_size;
 168         return map;
 169 }
 170
 171 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 172 {
 173         int ret, bytes;
 174         z_stream stream;
 175         char buffer[8192];
 176         char *buf;
 177
 178         /* Get the data stream */
 179         memset(&stream, 0, sizeof(stream));
 180         stream.next_in = map;
 181         stream.avail_in = mapsize;
 182         stream.next_out = buffer;
 183         stream.avail_out = sizeof(buffer);
 184
 185         inflateInit(&stream);
 186         ret = inflate(&stream, 0);
 187         if (ret < Z_OK)
 188                 return NULL;
 189         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 190                 return NULL;
 191
 192         bytes = strlen(buffer) + 1;
 193         buf = xmalloc(*size);
 194
 195         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 196         bytes = stream.total_out - bytes;
 197         if (bytes < *size && ret == Z_OK) {
 198                 stream.next_out = buf + bytes;
 199                 stream.avail_out = *size - bytes;
 200                 while (inflate(&stream, Z_FINISH) == Z_OK)
 201                         /* nothing */;
 202         }
 203         inflateEnd(&stream);
 204         return buf;
 205 }
 206
 207 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 208 {
 209         unsigned long mapsize;
 210         void *map, *buf;
 211
 212         map = map_sha1_file(sha1, &mapsize);
 213         if (map) {
 214                 buf = unpack_sha1_file(map, mapsize, type, size);
 215                 munmap(map, mapsize);
 216                 return buf;
 217         }
 218         return NULL;
 219 }
 220
 221 void *read_object_with_reference(const unsigned char *sha1,
 222                                  const unsigned char *required_type,
 223                                  unsigned long *size,
 224                                  unsigned char *actual_sha1_return)
 225 {
 226         char type[20];
 227         void *buffer;
 228         unsigned long isize;
 229         unsigned char actual_sha1[20];
 230
 231         memcpy(actual_sha1, sha1, 20);
 232         while (1) {
 233                 int ref_length = -1;
 234                 const char *ref_type = NULL;
 235
 236                 buffer = read_sha1_file(actual_sha1, type, &isize);
 237                 if (!buffer)
 238                         return NULL;
 239                 if (!strcmp(type, required_type)) {
 240                         *size = isize;
 241                         if (actual_sha1_return)
 242                                 memcpy(actual_sha1_return, actual_sha1, 20);
 243                         return buffer;
 244                 }
 245                 /* Handle references */
 246                 else if (!strcmp(type, "commit"))
 247                         ref_type = "tree ";
 248                 else if (!strcmp(type, "tag"))
 249                         ref_type = "object ";
 250                 else {
 251                         free(buffer);
 252                         return NULL;
 253                 }
 254                 ref_length = strlen(ref_type);
 255
 256                 if (memcmp(buffer, ref_type, ref_length) ||
 257                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
 258                         free(buffer);
 259                         return NULL;
 260                 }
 261                 /* Now we have the ID of the referred-to object in
 262                  * actual_sha1.  Check again. */
 263         }
 264 }
 265
 266 int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 267 {
 268         int size;
 269         char *compressed;
 270         z_stream stream;
 271         unsigned char sha1[20];
 272         SHA_CTX c;
 273         char *filename;
 274         char hdr[50];
 275         int fd, hdrlen;
 276
 277         /* Generate the header */
 278         hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
 279
 280         /* Sha1.. */
 281         SHA1_Init(&c);
 282         SHA1_Update(&c, hdr, hdrlen);
 283         SHA1_Update(&c, buf, len);
 284         SHA1_Final(sha1, &c);
 285
 286         if (returnsha1)
 287                 memcpy(returnsha1, sha1, 20);
 288
 289         filename = sha1_file_name(sha1);
 290         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 291         if (fd < 0) {
 292                 if (errno != EEXIST)
 293                         return -1;
 294
 295                 /*
 296                  * We might do collision checking here, but we'd need to
 297                  * uncompress the old file and check it. Later.
 298                  */
 299                 return 0;
 300         }
 301
 302         /* Set it up */
 303         memset(&stream, 0, sizeof(stream));
 304         deflateInit(&stream, Z_BEST_COMPRESSION);
 305         size = deflateBound(&stream, len+hdrlen);
 306         compressed = xmalloc(size);
 307
 308         /* Compress it */
 309         stream.next_out = compressed;
 310         stream.avail_out = size;
 311
 312         /* First header.. */
 313         stream.next_in = hdr;
 314         stream.avail_in = hdrlen;
 315         while (deflate(&stream, 0) == Z_OK)
 316                 /* nothing */
 317
 318         /* Then the data itself.. */
 319         stream.next_in = buf;
 320         stream.avail_in = len;
 321         while (deflate(&stream, Z_FINISH) == Z_OK)
 322                 /* nothing */;
 323         deflateEnd(&stream);
 324         size = stream.total_out;
 325
 326         if (write(fd, compressed, size) != size)
 327                 die("unable to write file");
 328         close(fd);
 329
 330         return 0;
 331 }
 332
 333 static inline int collision_check(char *filename, void *buf, unsigned int size)
 334 {
 335 #ifdef COLLISION_CHECK
 336         void *map;
 337         int fd = open(filename, O_RDONLY);
 338         struct stat st;
 339         int cmp;
 340
 341         /* Unreadable object, or object went away? Strange. */
 342         if (fd < 0)
 343                 return -1;
 344
 345         if (fstat(fd, &st) < 0 || size != st.st_size)
 346                 return -1;
 347
 348         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 349         close(fd);
 350         if (map == MAP_FAILED)
 351                 return -1;
 352         cmp = memcmp(buf, map, size);
 353         munmap(map, size);
 354         if (cmp)
 355                 return -1;
 356 #endif
 357         return 0;
 358 }
 359
 360 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 361 {
 362         char *filename = sha1_file_name(sha1);
 363         int fd;
 364
 365         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 366         if (fd < 0) {
 367                 if (errno != EEXIST)
 368                         return -1;
 369                 if (collision_check(filename, buf, size))
 370                         return error("SHA1 collision detected!"
 371                                         " This is bad, bad, BAD!\a\n");
 372                 return 0;
 373         }
 374         write(fd, buf, size);
 375         close(fd);
 376         return 0;
 377 }
 378
 379 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 380 {
 381         char *filename = sha1_file_name(sha1);
 382
 383         int local;
 384         z_stream stream;
 385         unsigned char real_sha1[20];
 386         char buf[4096];
 387         char discard[4096];
 388         int ret;
 389         SHA_CTX c;
 390
 391         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 392
 393         if (local < 0)
 394                 return error("Couldn't open %s\n", filename);
 395
 396         memset(&stream, 0, sizeof(stream));
 397
 398         inflateInit(&stream);
 399
 400         SHA1_Init(&c);
 401
 402         do {
 403                 ssize_t size;
 404                 size = read(fd, buf, 4096);
 405                 if (size <= 0) {
 406                         close(local);
 407                         unlink(filename);
 408                         if (!size)
 409                                 return error("Connection closed?");
 410                         perror("Reading from connection");
 411                         return -1;
 412                 }
 413                 write(local, buf, size);
 414                 stream.avail_in = size;
 415                 stream.next_in = buf;
 416                 do {
 417                         stream.next_out = discard;
 418                         stream.avail_out = sizeof(discard);
 419                         ret = inflate(&stream, Z_SYNC_FLUSH);
 420                         SHA1_Update(&c, discard, sizeof(discard) -
 421                                     stream.avail_out);
 422                 } while (stream.avail_in && ret == Z_OK);
 423
 424         } while (ret == Z_OK);
 425         inflateEnd(&stream);
 426
 427         close(local);
 428         SHA1_Final(real_sha1, &c);
 429         if (ret != Z_STREAM_END) {
 430                 unlink(filename);
 431                 return error("File %s corrupted", sha1_to_hex(sha1));
 432         }
 433         if (memcmp(sha1, real_sha1, 20)) {
 434                 unlink(filename);
 435                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 436         }
 437
 438         return 0;
 439 }
 440
 441 int has_sha1_file(const unsigned char *sha1)
 442 {
 443         char *filename = sha1_file_name(sha1);
 444         struct stat st;
 445
 446         if (!stat(filename, &st))
 447                 return 1;
 448         return 0;
 449 }