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 static unsigned hexval(char c)
  15 {
  16         if (c >= '0' && c <= '9')
  17                 return c - '0';
  18         if (c >= 'a' && c <= 'f')
  19                 return c - 'a' + 10;
  20         if (c >= 'A' && c <= 'F')
  21                 return c - 'A' + 10;
  22         return ~0;
  23 }
  24
  25 int get_sha1_hex(const char *hex, unsigned char *sha1)
  26 {
  27         int i;
  28         for (i = 0; i < 20; i++) {
  29                 unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
  30                 if (val & ~0xff)
  31                         return -1;
  32                 *sha1++ = val;
  33                 hex += 2;
  34         }
  35         return 0;
  36 }
  37
  38 char * sha1_to_hex(const unsigned char *sha1)
  39 {
  40         static char buffer[50];
  41         static const char hex[] = "0123456789abcdef";
  42         char *buf = buffer;
  43         int i;
  44
  45         for (i = 0; i < 20; i++) {
  46                 unsigned int val = *sha1++;
  47                 *buf++ = hex[val >> 4];
  48                 *buf++ = hex[val & 0xf];
  49         }
  50         return buffer;
  51 }
  52
  53 /*
  54  * NOTE! This returns a statically allocated buffer, so you have to be
  55  * careful about using it. Do a "strdup()" if you need to save the
  56  * filename.
  57  */
  58 char *sha1_file_name(const unsigned char *sha1)
  59 {
  60         int i;
  61         static char *name, *base;
  62
  63         if (!base) {
  64                 char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
  65                 int len = strlen(sha1_file_directory);
  66                 base = malloc(len + 60);
  67                 memcpy(base, sha1_file_directory, len);
  68                 memset(base+len, 0, 60);
  69                 base[len] = '/';
  70                 base[len+3] = '/';
  71                 name = base + len + 1;
  72         }
  73         for (i = 0; i < 20; i++) {
  74                 static char hex[] = "0123456789abcdef";
  75                 unsigned int val = sha1[i];
  76                 char *pos = name + i*2 + (i > 0);
  77                 *pos++ = hex[val >> 4];
  78                 *pos = hex[val & 0xf];
  79         }
  80         return base;
  81 }
  82
  83 int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
  84 {
  85         char header[100];
  86         unsigned char real_sha1[20];
  87         SHA_CTX c;
  88
  89         SHA1_Init(&c);
  90         SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
  91         SHA1_Update(&c, map, size);
  92         SHA1_Final(real_sha1, &c);
  93         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
  94 }
  95
  96 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
  97 {
  98         char *filename = sha1_file_name(sha1);
  99         int fd = open(filename, O_RDONLY);
 100         struct stat st;
 101         void *map;
 102
 103         if (fd < 0) {
 104                 perror(filename);
 105                 return NULL;
 106         }
 107         if (fstat(fd, &st) < 0) {
 108                 close(fd);
 109                 return NULL;
 110         }
 111         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 112         close(fd);
 113         if (-1 == (int)(long)map)
 114                 return NULL;
 115         *size = st.st_size;
 116         return map;
 117 }
 118
 119 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 120 {
 121         int ret, bytes;
 122         z_stream stream;
 123         char buffer[8192];
 124         char *buf;
 125
 126         /* Get the data stream */
 127         memset(&stream, 0, sizeof(stream));
 128         stream.next_in = map;
 129         stream.avail_in = mapsize;
 130         stream.next_out = buffer;
 131         stream.avail_out = sizeof(buffer);
 132
 133         inflateInit(&stream);
 134         ret = inflate(&stream, 0);
 135         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 136                 return NULL;
 137
 138         bytes = strlen(buffer) + 1;
 139         buf = malloc(*size);
 140         if (!buf)
 141                 return NULL;
 142
 143         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 144         bytes = stream.total_out - bytes;
 145         if (bytes < *size && ret == Z_OK) {
 146                 stream.next_out = buf + bytes;
 147                 stream.avail_out = *size - bytes;
 148                 while (inflate(&stream, Z_FINISH) == Z_OK)
 149                         /* nothing */;
 150         }
 151         inflateEnd(&stream);
 152         return buf;
 153 }
 154
 155 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 156 {
 157         unsigned long mapsize;
 158         void *map, *buf;
 159
 160         map = map_sha1_file(sha1, &mapsize);
 161         if (map) {
 162                 buf = unpack_sha1_file(map, mapsize, type, size);
 163                 munmap(map, mapsize);
 164                 return buf;
 165         }
 166         return NULL;
 167 }
 168
 169 void *read_tree_with_tree_or_commit_sha1(const unsigned char *sha1,
 170                                          unsigned long *size,
 171                                          unsigned char *tree_sha1_return)
 172 {
 173         char type[20];
 174         void *buffer;
 175         unsigned long isize;
 176         int was_commit = 0;
 177         unsigned char tree_sha1[20];
 178
 179         buffer = read_sha1_file(sha1, type, &isize);
 180
 181         /*
 182          * We might have read a commit instead of a tree, in which case
 183          * we parse out the tree_sha1 and attempt to read from there.
 184          * (buffer + 5) is because the tree sha1 is always at offset 5
 185          * in a commit record ("tree ").
 186          */
 187         if (buffer &&
 188             !strcmp(type, "commit") &&
 189             !get_sha1_hex(buffer + 5, tree_sha1)) {
 190                 free(buffer);
 191                 buffer = read_sha1_file(tree_sha1, type, &isize);
 192                 was_commit = 1;
 193         }
 194
 195         /*
 196          * Now do we have something and if so is it a tree?
 197          */
 198         if (!buffer || strcmp(type, "tree")) {
 199                 free(buffer);
 200                 return NULL;
 201         }
 202
 203         *size = isize;
 204         if (tree_sha1_return)
 205                 memcpy(tree_sha1_return, was_commit ? tree_sha1 : sha1, 20);
 206         return buffer;
 207 }
 208
 209 int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
 210 {
 211         int size;
 212         char *compressed;
 213         z_stream stream;
 214         unsigned char sha1[20];
 215         SHA_CTX c;
 216         char *filename;
 217         int fd;
 218
 219         /* Sha1.. */
 220         SHA1_Init(&c);
 221         SHA1_Update(&c, buf, len);
 222         SHA1_Final(sha1, &c);
 223
 224         if (returnsha1)
 225                 memcpy(returnsha1, sha1, 20);
 226
 227         filename = sha1_file_name(sha1);
 228         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 229         if (fd < 0) {
 230                 if (errno != EEXIST)
 231                         return -1;
 232
 233                 /*
 234                  * We might do collision checking here, but we'd need to
 235                  * uncompress the old file and check it. Later.
 236                  */
 237                 return 0;
 238         }
 239
 240         /* Set it up */
 241         memset(&stream, 0, sizeof(stream));
 242         deflateInit(&stream, Z_BEST_COMPRESSION);
 243         size = deflateBound(&stream, len);
 244         compressed = malloc(size);
 245
 246         /* Compress it */
 247         stream.next_in = buf;
 248         stream.avail_in = len;
 249         stream.next_out = compressed;
 250         stream.avail_out = size;
 251         while (deflate(&stream, Z_FINISH) == Z_OK)
 252                 /* nothing */;
 253         deflateEnd(&stream);
 254         size = stream.total_out;
 255
 256         if (write(fd, compressed, size) != size)
 257                 die("unable to write file");
 258         close(fd);
 259
 260         return 0;
 261 }
 262
 263 static inline int collision_check(char *filename, void *buf, unsigned int size)
 264 {
 265 #ifdef COLLISION_CHECK
 266         void *map;
 267         int fd = open(filename, O_RDONLY);
 268         struct stat st;
 269         int cmp;
 270
 271         /* Unreadable object, or object went away? Strange. */
 272         if (fd < 0)
 273                 return -1;
 274
 275         if (fstat(fd, &st) < 0 || size != st.st_size)
 276                 return -1;
 277
 278         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 279         close(fd);
 280         if (map == MAP_FAILED)
 281                 return -1;
 282         cmp = memcmp(buf, map, size);
 283         munmap(map, size);
 284         if (cmp)
 285                 return -1;
 286 #endif
 287         return 0;
 288 }
 289
 290 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 291 {
 292         char *filename = sha1_file_name(sha1);
 293         int fd;
 294
 295         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 296         if (fd < 0) {
 297                 if (errno != EEXIST)
 298                         return -1;
 299                 if (collision_check(filename, buf, size))
 300                         return error("SHA1 collision detected!"
 301                                         " This is bad, bad, BAD!\a\n");
 302                 return 0;
 303         }
 304         write(fd, buf, size);
 305         close(fd);
 306         return 0;
 307 }