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)
  84 {
  85         unsigned char real_sha1[20];
  86         SHA_CTX c;
  87
  88         SHA1_Init(&c);
  89         SHA1_Update(&c, map, size);
  90         SHA1_Final(real_sha1, &c);
  91         return memcmp(sha1, real_sha1, 20) ? -1 : 0;
  92 }
  93
  94 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
  95 {
  96         char *filename = sha1_file_name(sha1);
  97         int fd = open(filename, O_RDONLY);
  98         struct stat st;
  99         void *map;
 100
 101         if (fd < 0) {
 102                 perror(filename);
 103                 return NULL;
 104         }
 105         if (fstat(fd, &st) < 0) {
 106                 close(fd);
 107                 return NULL;
 108         }
 109         map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
 110         close(fd);
 111         if (-1 == (int)(long)map)
 112                 return NULL;
 113         *size = st.st_size;
 114         return map;
 115 }
 116
 117 void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
 118 {
 119         int ret, bytes;
 120         z_stream stream;
 121         char buffer[8192];
 122         char *buf;
 123
 124         /* Get the data stream */
 125         memset(&stream, 0, sizeof(stream));
 126         stream.next_in = map;
 127         stream.avail_in = mapsize;
 128         stream.next_out = buffer;
 129         stream.avail_out = sizeof(buffer);
 130
 131         inflateInit(&stream);
 132         ret = inflate(&stream, 0);
 133         if (sscanf(buffer, "%10s %lu", type, size) != 2)
 134                 return NULL;
 135
 136         bytes = strlen(buffer) + 1;
 137         buf = malloc(*size);
 138         if (!buf)
 139                 return NULL;
 140
 141         memcpy(buf, buffer + bytes, stream.total_out - bytes);
 142         bytes = stream.total_out - bytes;
 143         if (bytes < *size && ret == Z_OK) {
 144                 stream.next_out = buf + bytes;
 145                 stream.avail_out = *size - bytes;
 146                 while (inflate(&stream, Z_FINISH) == Z_OK)
 147                         /* nothing */;
 148         }
 149         inflateEnd(&stream);
 150         return buf;
 151 }
 152
 153 void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
 154 {
 155         unsigned long mapsize;
 156         void *map, *buf;
 157
 158         map = map_sha1_file(sha1, &mapsize);
 159         if (map) {
 160                 buf = unpack_sha1_file(map, mapsize, type, size);
 161                 munmap(map, mapsize);
 162                 return buf;
 163         }
 164         return NULL;
 165 }
 166
 167 int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
 168 {
 169         int size;
 170         char *compressed;
 171         z_stream stream;
 172         unsigned char sha1[20];
 173         SHA_CTX c;
 174
 175         /* Set it up */
 176         memset(&stream, 0, sizeof(stream));
 177         deflateInit(&stream, Z_BEST_COMPRESSION);
 178         size = deflateBound(&stream, len);
 179         compressed = malloc(size);
 180
 181         /* Compress it */
 182         stream.next_in = buf;
 183         stream.avail_in = len;
 184         stream.next_out = compressed;
 185         stream.avail_out = size;
 186         while (deflate(&stream, Z_FINISH) == Z_OK)
 187                 /* nothing */;
 188         deflateEnd(&stream);
 189         size = stream.total_out;
 190
 191         /* Sha1.. */
 192         SHA1_Init(&c);
 193         SHA1_Update(&c, compressed, size);
 194         SHA1_Final(sha1, &c);
 195
 196         if (write_sha1_buffer(sha1, compressed, size) < 0)
 197                 return -1;
 198         if (returnsha1)
 199                 memcpy(returnsha1, sha1, 20);
 200         return 0;
 201 }
 202
 203 static inline int collision_check(char *filename, void *buf, unsigned int size)
 204 {
 205 #ifdef COLLISION_CHECK
 206         void *map;
 207         int fd = open(filename, O_RDONLY);
 208         struct stat st;
 209         int cmp;
 210
 211         /* Unreadable object, or object went away? Strange. */
 212         if (fd < 0)
 213                 return -1;
 214
 215         if (fstat(fd, &st) < 0 || size != st.st_size)
 216                 return -1;
 217
 218         map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
 219         close(fd);
 220         if (map == MAP_FAILED)
 221                 return -1;
 222         cmp = memcmp(buf, map, size);
 223         munmap(map, size);
 224         if (cmp)
 225                 return -1;
 226 #endif
 227         return 0;
 228 }
 229
 230 int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
 231 {
 232         char *filename = sha1_file_name(sha1);
 233         int fd;
 234
 235         fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 236         if (fd < 0) {
 237                 if (errno != EEXIST)
 238                         return -1;
 239                 if (collision_check(filename, buf, size))
 240                         return error("SHA1 collision detected!"
 241                                         " This is bad, bad, BAD!\a\n");
 242                 return 0;
 243         }
 244         write(fd, buf, size);
 245         close(fd);
 246         return 0;
 247 }