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 (sscanf(buffer, "%10s %lu", type, size) != 2)
 159                 return NULL;
 160
 161         bytes = strlen(buffer) + 1;
 162         buf = malloc(*size);
 163         if (!buf)
 164                 return NULL;
 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_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
 193                                          unsigned long *size,
 194                                          unsigned char *tree_sha1_return)
 195 {
 196         char type[20];
 197         void *buffer;
 198         unsigned long isize;
 199         int was_commit = 0;
 200         unsigned char tree_sha1[20];
 201
 202         buffer = read_sha1_file(sha1, type, &isize);
 203
 204         /*
 205          * We might have read a commit instead of a tree, in which case
 206          * we parse out the tree_sha1 and attempt to read from there.
 207          * (buffer + 5) is because the tree sha1 is always at offset 5
 208          * in a commit record ("tree ").
 209          */
 210         if (buffer &&
 211             !strcmp(type, "commit") &&
 212             !get_sha1_hex(buffer + 5, tree_sha1)) {
 213                 free(buffer);
 214                 buffer = read_sha1_file(tree_sha1, type, &isize);
 215                 was_commit = 1;
 216         }
 217
 218         /*
 219          * Now do we have something and if so is it a tree?
 220          */
 221         if (!buffer || strcmp(type, "tree")) {
 222                 free(buffer);
 223                 return NULL;
 224         }
 225
 226         *size = isize;
 227         if (tree_sha1_return)
 228                 memcpy(tree_sha1_return, was_commit ? tree_sha1 : sha1, 20);
 229         return buffer;
 230 }
 231
 232 int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
 233 {
 234         int size;
 235         char *compressed;
 236         z_stream stream;
 237         unsigned char sha1[20];
 238         SHA_CTX c;
 239         char *filename;
 240         int fd;
 241
 242         /* Sha1.. */
 243         SHA1_Init(&c);
 244         SHA1_Update(&c, buf, len);
 245         SHA1_Final(sha1, &c);
 246
 247         if (returnsha1)
 248                 memcpy(returnsha1, sha1, 20);
 249
 250         filename = sha1_file_name(sha1);
 251         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 252         if (fd < 0) {
 253                 if (errno != EEXIST)
 254                         return -1;
 255
 256                 /*
 257                  * We might do collision checking here, but we'd need to
 258                  * uncompress the old file and check it. Later.
 259                  */
 260                 return 0;
 261         }
 262
 263         /* Set it up */
 264         memset(&stream, 0, sizeof(stream));
 265         deflateInit(&stream, Z_BEST_COMPRESSION);
 266         size = deflateBound(&stream, len);
 267         compressed = malloc(size);
 268
 269         /* Compress it */
 270         stream.next_in = buf;
 271         stream.avail_in = len;
 272         stream.next_out = compressed;
 273         stream.avail_out = size;
 274         while (deflate(&stream, Z_FINISH) == Z_OK)
 275                 /* nothing */;
 276         deflateEnd(&stream);
 277         size = stream.total_out;
 278
 279         if (write(fd, compressed, size) != size)
 280                 die("unable to write file");
 281         close(fd);
 282
 283         return 0;
 284 }
 285
 286 static inline int collision_check(char *filename, void *buf, unsigned int size)
 287 {
 288 #ifdef COLLISION_CHECK
 289         void *map;
 290         int fd = open(filename, O_RDONLY);
 291         struct stat st;
 292         int cmp;
 293
 294         /* Unreadable object, or object went away? Strange. */
 295         if (fd < 0)
 296                 return -1;
 297
 298         if (fstat(fd, &st) < 0 || size != st.st_size)
 299                 return -1;
 300
 301         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 302         close(fd);
 303         if (map == MAP_FAILED)
 304                 return -1;
 305         cmp = memcmp(buf, map, size);
 306         munmap(map, size);
 307         if (cmp)
 308                 return -1;
 309 #endif
 310         return 0;
 311 }
 312
 313 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 314 {
 315         char *filename = sha1_file_name(sha1);
 316         int fd;
 317
 318         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 319         if (fd < 0) {
 320                 if (errno != EEXIST)
 321                         return -1;
 322                 if (collision_check(filename, buf, size))
 323                         return error("SHA1 collision detected!"
 324                                         " This is bad, bad, BAD!\a\n");
 325                 return 0;
 326         }
 327         write(fd, buf, size);
 328         close(fd);
 329         return 0;
 330 }