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 = malloc(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 = malloc(*size);
 165         if (!buf)
 166                 return NULL;
 167
 168         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 169         bytes = stream.total_out - bytes;
 170         if (bytes < *size && ret == Z_OK) {
 171                 stream.next_out = buf + bytes;
 172                 stream.avail_out = *size - bytes;
 173                 while (inflate(&stream, Z_FINISH) == Z_OK)
 174                         /* nothing */;
 175         }
 176         inflateEnd(&stream);
 177         return buf;
 178 }
 179
 180 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 181 {
 182         unsigned long mapsize;
 183         void *map, *buf;
 184
 185         map = map_sha1_file(sha1, &mapsize);
 186         if (map) {
 187                 buf = unpack_sha1_file(map, mapsize, type, size);
 188                 munmap(map, mapsize);
 189                 return buf;
 190         }
 191         return NULL;
 192 }
 193
 194 void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
 195                                          unsigned long *size,
 196                                          unsigned char *tree_sha1_return)
 197 {
 198         char type[20];
 199         void *buffer;
 200         unsigned long isize;
 201         int was_commit = 0;
 202         unsigned char tree_sha1[20];
 203
 204         buffer = read_sha1_file(sha1, type, &isize);
 205
 206         /*
 207          * We might have read a commit instead of a tree, in which case
 208          * we parse out the tree_sha1 and attempt to read from there.
 209          * (buffer + 5) is because the tree sha1 is always at offset 5
 210          * in a commit record ("tree ").
 211          */
 212         if (buffer &&
 213             !strcmp(type, "commit") &&
 214             !get_sha1_hex(buffer + 5, tree_sha1)) {
 215                 free(buffer);
 216                 buffer = read_sha1_file(tree_sha1, type, &isize);
 217                 was_commit = 1;
 218         }
 219
 220         /*
 221          * Now do we have something and if so is it a tree?
 222          */
 223         if (!buffer || strcmp(type, "tree")) {
 224                 free(buffer);
 225                 return NULL;
 226         }
 227
 228         *size = isize;
 229         if (tree_sha1_return)
 230                 memcpy(tree_sha1_return, was_commit ? tree_sha1 : sha1, 20);
 231         return buffer;
 232 }
 233
 234 int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *returnsha1)
 235 {
 236         int size;
 237         char *compressed;
 238         z_stream stream;
 239         unsigned char sha1[20];
 240         SHA_CTX c;
 241         char *filename;
 242         char hdr[50];
 243         int fd, hdrlen;
 244
 245         /* Generate the header */
 246         hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
 247
 248         /* Sha1.. */
 249         SHA1_Init(&c);
 250         SHA1_Update(&c, hdr, hdrlen);
 251         SHA1_Update(&c, buf, len);
 252         SHA1_Final(sha1, &c);
 253
 254         if (returnsha1)
 255                 memcpy(returnsha1, sha1, 20);
 256
 257         filename = sha1_file_name(sha1);
 258         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 259         if (fd < 0) {
 260                 if (errno != EEXIST)
 261                         return -1;
 262
 263                 /*
 264                  * We might do collision checking here, but we'd need to
 265                  * uncompress the old file and check it. Later.
 266                  */
 267                 return 0;
 268         }
 269
 270         /* Set it up */
 271         memset(&stream, 0, sizeof(stream));
 272         deflateInit(&stream, Z_BEST_COMPRESSION);
 273         size = deflateBound(&stream, len+hdrlen);
 274         compressed = malloc(size);
 275
 276         /* Compress it */
 277         stream.next_out = compressed;
 278         stream.avail_out = size;
 279
 280         /* First header.. */
 281         stream.next_in = hdr;
 282         stream.avail_in = hdrlen;
 283         while (deflate(&stream, 0) == Z_OK)
 284                 /* nothing */
 285
 286         /* Then the data itself.. */
 287         stream.next_in = buf;
 288         stream.avail_in = len;
 289         while (deflate(&stream, Z_FINISH) == Z_OK)
 290                 /* nothing */;
 291         deflateEnd(&stream);
 292         size = stream.total_out;
 293
 294         if (write(fd, compressed, size) != size)
 295                 die("unable to write file");
 296         close(fd);
 297
 298         return 0;
 299 }
 300
 301 static inline int collision_check(char *filename, void *buf, unsigned int size)
 302 {
 303 #ifdef COLLISION_CHECK
 304         void *map;
 305         int fd = open(filename, O_RDONLY);
 306         struct stat st;
 307         int cmp;
 308
 309         /* Unreadable object, or object went away? Strange. */
 310         if (fd < 0)
 311                 return -1;
 312
 313         if (fstat(fd, &st) < 0 || size != st.st_size)
 314                 return -1;
 315
 316         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 317         close(fd);
 318         if (map == MAP_FAILED)
 319                 return -1;
 320         cmp = memcmp(buf, map, size);
 321         munmap(map, size);
 322         if (cmp)
 323                 return -1;
 324 #endif
 325         return 0;
 326 }
 327
 328 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 329 {
 330         char *filename = sha1_file_name(sha1);
 331         int fd;
 332
 333         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 334         if (fd < 0) {
 335                 if (errno != EEXIST)
 336                         return -1;
 337                 if (collision_check(filename, buf, size))
 338                         return error("SHA1 collision detected!"
 339                                         " This is bad, bad, BAD!\a\n");
 340                 return 0;
 341         }
 342         write(fd, buf, size);
 343         close(fd);
 344         return 0;
 345 }
 346
 347 int write_sha1_from_fd(const unsigned char *sha1, int fd)
 348 {
 349         char *filename = sha1_file_name(sha1);
 350
 351         int local;
 352         z_stream stream;
 353         unsigned char real_sha1[20];
 354         char buf[4096];
 355         char discard[4096];
 356         int ret;
 357         SHA_CTX c;
 358
 359         local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 360
 361         if (local < 0)
 362                 return error("Couldn't open %s\n", filename);
 363
 364         memset(&stream, 0, sizeof(stream));
 365
 366         inflateInit(&stream);
 367
 368         SHA1_Init(&c);
 369
 370         do {
 371                 ssize_t size;
 372                 size = read(fd, buf, 4096);
 373                 if (size <= 0) {
 374                         close(local);
 375                         unlink(filename);
 376                         if (!size)
 377                                 return error("Connection closed?");
 378                         perror("Reading from connection");
 379                         return -1;
 380                 }
 381                 write(local, buf, size);
 382                 stream.avail_in = size;
 383                 stream.next_in = buf;
 384                 do {
 385                         stream.next_out = discard;
 386                         stream.avail_out = sizeof(discard);
 387                         ret = inflate(&stream, Z_SYNC_FLUSH);
 388                         SHA1_Update(&c, discard, sizeof(discard) -
 389                                     stream.avail_out);
 390                 } while (stream.avail_in && ret == Z_OK);
 391
 392         } while (ret == Z_OK);
 393         inflateEnd(&stream);
 394
 395         close(local);
 396         SHA1_Final(real_sha1, &c);
 397         if (ret != Z_STREAM_END) {
 398                 unlink(filename);
 399                 return error("File %s corrupted", sha1_to_hex(sha1));
 400         }
 401         if (memcmp(sha1, real_sha1, 20)) {
 402                 unlink(filename);
 403                 return error("File %s has bad hash\n", sha1_to_hex(sha1));
 404         }
 405
 406         return 0;
 407 }
 408
 409 int has_sha1_file(const unsigned char *sha1)
 410 {
 411         char *filename = sha1_file_name(sha1);
 412         struct stat st;
 413
 414         if (!stat(filename, &st))
 415                 return 1;
 416         return 0;
 417 }