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 char * sha1_to_hex(const unsigned char *sha1)
  49 {
  50         static char buffer[50];
  51         static const char hex[] = "0123456789abcdef";
  52         char *buf = buffer;
  53         int i;
  54
  55         for (i = 0; i < 20; i++) {
  56                 unsigned int val = *sha1++;
  57                 *buf++ = hex[val >> 4];
  58                 *buf++ = hex[val & 0xf];
  59         }
  60         return buffer;
  61 }
  62
  63 /*
  64  * NOTE! This returns a statically allocated buffer, so you have to be
  65  * careful about using it. Do a "strdup()" if you need to save the
  66  * filename.
  67  */
  68 char *sha1_file_name(const unsigned char *sha1)
  69 {
  70         int i;
  71         static char *name, *base;
  72
  73         if (!base) {
  74                 char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
  75                 int len = strlen(sha1_file_directory);
  76                 base = xmalloc(len + 60);
  77                 memcpy(base, sha1_file_directory, len);
  78                 memset(base+len, 0, 60);
  79                 base[len] = '/';
  80                 base[len+3] = '/';
  81                 name = base + len + 1;
  82         }
  83         for (i = 0; i < 20; i++) {
  84                 static char hex[] = "0123456789abcdef";
  85                 unsigned int val = sha1[i];
  86                 char *pos = name + i*2 + (i > 0);
  87                 *pos++ = hex[val >> 4];
  88                 *pos = hex[val & 0xf];
  89         }
  90         return base;
  91 }
  92
  93 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
  94 {
  95         char header[100];
  96         unsigned char real_sha1[20];
  97         SHA_CTX c;
  98
  99         SHA1_Init(&c);
 100         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
 101         SHA1_Update(&c, map, size);
 102         SHA1_Final(real_sha1, &c);
 103         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
 104 }
 105
 106 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 107 {
 108         char *filename = sha1_file_name(sha1);
 109         struct stat st;
 110         void *map;
 111         int fd;
 112
 113         fd = open(filename, O_RDONLY | sha1_file_open_flag);
 114         if (fd < 0) {
 115                 /* See if it works without O_NOATIME */
 116                 switch (sha1_file_open_flag) {
 117                 default:
 118                         fd = open(filename, O_RDONLY);
 119                         if (fd >= 0)
 120                                 break;
 121                 /* Fallthrough */
 122                 case 0:
 123                         perror(filename);
 124                         return NULL;
 125                 }
 126
 127                 /* If it failed once, it will probably fail again. Stop using O_NOATIME */
 128                 sha1_file_open_flag = 0;
 129         }
 130         if (fstat(fd, &st) < 0) {
 131                 close(fd);
 132                 return NULL;
 133         }
 134         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 135         close(fd);
 136         if (-1 == (int)(long)map)
 137                 return NULL;
 138         *size = st.st_size;
 139         return map;
 140 }
 141
 142 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 143 {
 144         int ret, bytes;
 145         z_stream stream;
 146         char buffer[8192];
 147         char *buf;
 148
 149         /* Get the data stream */
 150         memset(&stream, 0, sizeof(stream));
 151         stream.next_in = map;
 152         stream.avail_in = mapsize;
 153         stream.next_out = buffer;
 154         stream.avail_out = sizeof(buffer);
 155
 156         inflateInit(&stream);
 157         ret = inflate(&stream, 0);
 158         if (ret < Z_OK)
 159                 return NULL;
 160         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 161                 return NULL;
 162
 163         bytes = strlen(buffer) + 1;
 164         buf = xmalloc(*size);
 165
 166         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 167         bytes = stream.total_out - bytes;
 168         if (bytes < *size && ret == Z_OK) {
 169                 stream.next_out = buf + bytes;
 170                 stream.avail_out = *size - bytes;
 171                 while (inflate(&stream, Z_FINISH) == Z_OK)
 172                         /* nothing */;
 173         }
 174         inflateEnd(&stream);
 175         return buf;
 176 }
 177
 178 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 179 {
 180         unsigned long mapsize;
 181         void *map, *buf;
 182
 183         map = map_sha1_file(sha1, &mapsize);
 184         if (map) {
 185                 buf = unpack_sha1_file(map, mapsize, type, size);
 186                 munmap(map, mapsize);
 187                 return buf;
 188         }
 189         return NULL;
 190 }
 191
 192 void *read_object_with_reference(const unsigned char *sha1,
 193                                  const unsigned char *required_type,
 194                                  unsigned long *size,
 195                                  unsigned char *actual_sha1_return)
 196 {
 197         char type[20];
 198         void *buffer;
 199         unsigned long isize;
 200         unsigned char actual_sha1[20];
 201
 202         memcpy(actual_sha1, sha1, 20);
 203         while (1) {
 204                 int ref_length = -1;
 205                 const char *ref_type = NULL;
 206
 207                 buffer = read_sha1_file(actual_sha1, type, &isize);
 208                 if (!buffer)
 209                         return NULL;
 210                 if (!strcmp(type, required_type)) {
 211                         *size = isize;
 212                         if (actual_sha1_return)
 213                                 memcpy(actual_sha1_return, actual_sha1, 20);
 214                         return buffer;
 215                 }
 216                 /* Handle references */
 217                 else if (!strcmp(type, "commit"))
 218                         ref_type = "tree ";
 219                 else if (!strcmp(type, "tag"))
 220                         ref_type = "object ";
 221                 else {
 222                         free(buffer);
 223                         return NULL;
 224                 }
 225                 ref_length = strlen(ref_type);
 226
 227                 if (memcmp(buffer, ref_type, ref_length) ||
 228                     get_sha1_hex(buffer + ref_length, actual_sha1)) {
 229                         free(buffer);
 230                         return NULL;
 231                 }
 232                 /* Now we have the ID of the referred-to object in
 233                  * actual_sha1.  Check again. */
 234         }
 235 }
 236
 237 int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 238 {
 239         int size;
 240         char *compressed;
 241         z_stream stream;
 242         unsigned char sha1[20];
 243         SHA_CTX c;
 244         char *filename;
 245         char hdr[50];
 246         int fd, hdrlen;
 247
 248         /* Generate the header */
 249         hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
 250
 251         /* Sha1.. */
 252         SHA1_Init(&c);
 253         SHA1_Update(&c, hdr, hdrlen);
 254         SHA1_Update(&c, buf, len);
 255         SHA1_Final(sha1, &c);
 256
 257         if (returnsha1)
 258                 memcpy(returnsha1, sha1, 20);
 259
 260         filename = sha1_file_name(sha1);
 261         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 262         if (fd < 0) {
 263                 if (errno != EEXIST)
 264                         return -1;
 265
 266                 /*
 267                  * We might do collision checking here, but we'd need to
 268                  * uncompress the old file and check it. Later.
 269                  */
 270                 return 0;
 271         }
 272
 273         /* Set it up */
 274         memset(&stream, 0, sizeof(stream));
 275         deflateInit(&stream, Z_BEST_COMPRESSION);
 276         size = deflateBound(&stream, len+hdrlen);
 277         compressed = xmalloc(size);
 278
 279         /* Compress it */
 280         stream.next_out = compressed;
 281         stream.avail_out = size;
 282
 283         /* First header.. */
 284         stream.next_in = hdr;
 285         stream.avail_in = hdrlen;
 286         while (deflate(&stream, 0) == Z_OK)
 287                 /* nothing */
 288
 289         /* Then the data itself.. */
 290         stream.next_in = buf;
 291         stream.avail_in = len;
 292         while (deflate(&stream, Z_FINISH) == Z_OK)
 293                 /* nothing */;
 294         deflateEnd(&stream);
 295         size = stream.total_out;
 296
 297         if (write(fd, compressed, size) != size)
 298                 die("unable to write file");
 299         close(fd);
 300
 301         return 0;
 302 }
 303
 304 static inline int collision_check(char *filename, void *buf, unsigned int size)
 305 {
 306 #ifdef COLLISION_CHECK
 307         void *map;
 308         int fd = open(filename, O_RDONLY);
 309         struct stat st;
 310         int cmp;
 311
 312         /* Unreadable object, or object went away? Strange. */
 313         if (fd < 0)
 314                 return -1;
 315
 316         if (fstat(fd, &st) < 0 || size != st.st_size)
 317                 return -1;
 318
 319         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 320         close(fd);
 321         if (map == MAP_FAILED)
 322                 return -1;
 323         cmp = memcmp(buf, map, size);
 324         munmap(map, size);
 325         if (cmp)
 326                 return -1;
 327 #endif
 328         return 0;
 329 }
 330
 331 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 332 {
 333         char *filename = sha1_file_name(sha1);
 334         int fd;
 335
 336         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 337         if (fd < 0) {
 338                 if (errno != EEXIST)
 339                         return -1;
 340                 if (collision_check(filename, buf, size))
 341                         return error("SHA1 collision detected!"
 342                                         " This is bad, bad, BAD!\a\n");
 343                 return 0;
 344         }
 345         write(fd, buf, size);
 346         close(fd);
 347         return 0;
 348 }
 349
 350 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 351 {
 352         char *filename = sha1_file_name(sha1);
 353
 354         int local;
 355         z_stream stream;
 356         unsigned char real_sha1[20];
 357         char buf[4096];
 358         char discard[4096];
 359         int ret;
 360         SHA_CTX c;
 361
 362         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 363
 364         if (local < 0)
 365                 return error("Couldn't open %s\n", filename);
 366
 367         memset(&stream, 0, sizeof(stream));
 368
 369         inflateInit(&stream);
 370
 371         SHA1_Init(&c);
 372
 373         do {
 374                 ssize_t size;
 375                 size = read(fd, buf, 4096);
 376                 if (size <= 0) {
 377                         close(local);
 378                         unlink(filename);
 379                         if (!size)
 380                                 return error("Connection closed?");
 381                         perror("Reading from connection");
 382                         return -1;
 383                 }
 384                 write(local, buf, size);
 385                 stream.avail_in = size;
 386                 stream.next_in = buf;
 387                 do {
 388                         stream.next_out = discard;
 389                         stream.avail_out = sizeof(discard);
 390                         ret = inflate(&stream, Z_SYNC_FLUSH);
 391                         SHA1_Update(&c, discard, sizeof(discard) -
 392                                     stream.avail_out);
 393                 } while (stream.avail_in && ret == Z_OK);
 394
 395         } while (ret == Z_OK);
 396         inflateEnd(&stream);
 397
 398         close(local);
 399         SHA1_Final(real_sha1, &c);
 400         if (ret != Z_STREAM_END) {
 401                 unlink(filename);
 402                 return error("File %s corrupted", sha1_to_hex(sha1));
 403         }
 404         if (memcmp(sha1, real_sha1, 20)) {
 405                 unlink(filename);
 406                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 407         }
 408
 409         return 0;
 410 }
 411
 412 int has_sha1_file(const unsigned char *sha1)
 413 {
 414         char *filename = sha1_file_name(sha1);
 415         struct stat st;
 416
 417         if (!stat(filename, &st))
 418                 return 1;
 419         return 0;
 420 }