refs.c

   1 #include "refs.h"
   2 #include "cache.h"
   3
   4 #include <errno.h>
   5 #include <ctype.h>
   6
   7 /* We allow "recursive" symbolic refs. Only within reason, though */
   8 #define MAXDEPTH 5
   9
  10 #ifndef USE_SYMLINK_HEAD
  11 #define USE_SYMLINK_HEAD 1
  12 #endif
  13
  14 int validate_symref(const char *path)
  15 {
  16         struct stat st;
  17         char *buf, buffer[256];
  18         int len, fd;
  19
  20         if (lstat(path, &st) < 0)
  21                 return -1;
  22
  23         /* Make sure it is a "refs/.." symlink */
  24         if (S_ISLNK(st.st_mode)) {
  25                 len = readlink(path, buffer, sizeof(buffer)-1);
  26                 if (len >= 5 && !memcmp("refs/", buffer, 5))
  27                         return 0;
  28                 return -1;
  29         }
  30
  31         /*
  32          * Anything else, just open it and try to see if it is a symbolic ref.
  33          */
  34         fd = open(path, O_RDONLY);
  35         if (fd < 0)
  36                 return -1;
  37         len = read(fd, buffer, sizeof(buffer)-1);
  38         close(fd);
  39
  40         /*
  41          * Is it a symbolic ref?
  42          */
  43         if (len < 4 || memcmp("ref:", buffer, 4))
  44                 return -1;
  45         buf = buffer + 4;
  46         len -= 4;
  47         while (len && isspace(*buf))
  48                 buf++, len--;
  49         if (len >= 5 && !memcmp("refs/", buf, 5))
  50                 return 0;
  51         return -1;
  52 }
  53
  54 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  55 {
  56         int depth = MAXDEPTH, len;
  57         char buffer[256];
  58
  59         for (;;) {
  60                 struct stat st;
  61                 char *buf;
  62                 int fd;
  63
  64                 if (--depth < 0)
  65                         return NULL;
  66
  67                 /* Special case: non-existing file.
  68                  * Not having the refs/heads/new-branch is OK
  69                  * if we are writing into it, so is .git/HEAD
  70                  * that points at refs/heads/master still to be
  71                  * born.  It is NOT OK if we are resolving for
  72                  * reading.
  73                  */
  74                 if (lstat(path, &st) < 0) {
  75                         if (reading || errno != ENOENT)
  76                                 return NULL;
  77                         memset(sha1, 0, 20);
  78                         return path;
  79                 }
  80
  81                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
  82                 if (S_ISLNK(st.st_mode)) {
  83                         len = readlink(path, buffer, sizeof(buffer)-1);
  84                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  85                                 path = git_path("%.*s", len, buffer);
  86                                 continue;
  87                         }
  88                 }
  89
  90                 /*
  91                  * Anything else, just open it and try to use it as
  92                  * a ref
  93                  */
  94                 fd = open(path, O_RDONLY);
  95                 if (fd < 0)
  96                         return NULL;
  97                 len = read(fd, buffer, sizeof(buffer)-1);
  98                 close(fd);
  99
 100                 /*
 101                  * Is it a symbolic ref?
 102                  */
 103                 if (len < 4 || memcmp("ref:", buffer, 4))
 104                         break;
 105                 buf = buffer + 4;
 106                 len -= 4;
 107                 while (len && isspace(*buf))
 108                         buf++, len--;
 109                 while (len && isspace(buf[len-1]))
 110                         buf[--len] = 0;
 111                 path = git_path("%.*s", len, buf);
 112         }
 113         if (len < 40 || get_sha1_hex(buffer, sha1))
 114                 return NULL;
 115         return path;
 116 }
 117
 118 int create_symref(const char *git_HEAD, const char *refs_heads_master)
 119 {
 120 #if USE_SYMLINK_HEAD
 121         unlink(git_HEAD);
 122         return symlink(refs_heads_master, git_HEAD);
 123 #else
 124         const char *lockpath;
 125         char ref[1000];
 126         int fd, len, written;
 127
 128         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 129         if (sizeof(ref) <= len) {
 130                 error("refname too long: %s", refs_heads_master);
 131                 return -1;
 132         }
 133         lockpath = mkpath("%s.lock", git_HEAD);
 134         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
 135         written = write(fd, ref, len);
 136         close(fd);
 137         if (written != len) {
 138                 unlink(lockpath);
 139                 error("Unable to write to %s", lockpath);
 140                 return -2;
 141         }
 142         if (rename(lockpath, git_HEAD) < 0) {
 143                 unlink(lockpath);
 144                 error("Unable to create %s", git_HEAD);
 145                 return -3;
 146         }
 147         return 0;
 148 #endif
 149 }
 150
 151 int read_ref(const char *filename, unsigned char *sha1)
 152 {
 153         if (resolve_ref(filename, sha1, 1))
 154                 return 0;
 155         return -1;
 156 }
 157
 158 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 159 {
 160         int retval = 0;
 161         DIR *dir = opendir(git_path("%s", base));
 162
 163         if (dir) {
 164                 struct dirent *de;
 165                 int baselen = strlen(base);
 166                 char *path = xmalloc(baselen + 257);
 167
 168                 if (!strncmp(base, "./", 2)) {
 169                         base += 2;
 170                         baselen -= 2;
 171                 }
 172                 memcpy(path, base, baselen);
 173                 if (baselen && base[baselen-1] != '/')
 174                         path[baselen++] = '/';
 175
 176                 while ((de = readdir(dir)) != NULL) {
 177                         unsigned char sha1[20];
 178                         struct stat st;
 179                         int namelen;
 180
 181                         if (de->d_name[0] == '.')
 182                                 continue;
 183                         namelen = strlen(de->d_name);
 184                         if (namelen > 255)
 185                                 continue;
 186                         memcpy(path + baselen, de->d_name, namelen+1);
 187                         if (stat(git_path("%s", path), &st) < 0)
 188                                 continue;
 189                         if (S_ISDIR(st.st_mode)) {
 190                                 retval = do_for_each_ref(path, fn);
 191                                 if (retval)
 192                                         break;
 193                                 continue;
 194                         }
 195                         if (read_ref(git_path("%s", path), sha1) < 0)
 196                                 continue;
 197                         if (!has_sha1_file(sha1))
 198                                 continue;
 199                         retval = fn(path, sha1);
 200                         if (retval)
 201                                 break;
 202                 }
 203                 free(path);
 204                 closedir(dir);
 205         }
 206         return retval;
 207 }
 208
 209 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 210 {
 211         unsigned char sha1[20];
 212         if (!read_ref(git_path("HEAD"), sha1))
 213                 return fn("HEAD", sha1);
 214         return 0;
 215 }
 216
 217 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 218 {
 219         return do_for_each_ref("refs", fn);
 220 }
 221
 222 static char *ref_file_name(const char *ref)
 223 {
 224         char *base = get_refs_directory();
 225         int baselen = strlen(base);
 226         int reflen = strlen(ref);
 227         char *ret = xmalloc(baselen + 2 + reflen);
 228         sprintf(ret, "%s/%s", base, ref);
 229         return ret;
 230 }
 231
 232 static char *ref_lock_file_name(const char *ref)
 233 {
 234         char *base = get_refs_directory();
 235         int baselen = strlen(base);
 236         int reflen = strlen(ref);
 237         char *ret = xmalloc(baselen + 7 + reflen);
 238         sprintf(ret, "%s/%s.lock", base, ref);
 239         return ret;
 240 }
 241
 242 int get_ref_sha1(const char *ref, unsigned char *sha1)
 243 {
 244         const char *filename;
 245
 246         if (check_ref_format(ref))
 247                 return -1;
 248         filename = git_path("refs/%s", ref);
 249         return read_ref(filename, sha1);
 250 }
 251
 252 static int lock_ref_file(const char *filename, const char *lock_filename,
 253                          const unsigned char *old_sha1)
 254 {
 255         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 256         unsigned char current_sha1[20];
 257         int retval;
 258         if (fd < 0) {
 259                 return error("Couldn't open lock file for %s: %s",
 260                              filename, strerror(errno));
 261         }
 262         retval = read_ref(filename, current_sha1);
 263         if (old_sha1) {
 264                 if (retval) {
 265                         close(fd);
 266                         unlink(lock_filename);
 267                         return error("Could not read the current value of %s",
 268                                      filename);
 269                 }
 270                 if (memcmp(current_sha1, old_sha1, 20)) {
 271                         close(fd);
 272                         unlink(lock_filename);
 273                         error("The current value of %s is %s",
 274                               filename, sha1_to_hex(current_sha1));
 275                         return error("Expected %s",
 276                                      sha1_to_hex(old_sha1));
 277                 }
 278         } else {
 279                 if (!retval) {
 280                         close(fd);
 281                         unlink(lock_filename);
 282                         return error("Unexpectedly found a value of %s for %s",
 283                                      sha1_to_hex(current_sha1), filename);
 284                 }
 285         }
 286         return fd;
 287 }
 288
 289 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 290 {
 291         char *filename;
 292         char *lock_filename;
 293         int retval;
 294         if (check_ref_format(ref))
 295                 return -1;
 296         filename = ref_file_name(ref);
 297         lock_filename = ref_lock_file_name(ref);
 298         retval = lock_ref_file(filename, lock_filename, old_sha1);
 299         free(filename);
 300         free(lock_filename);
 301         return retval;
 302 }
 303
 304 static int write_ref_file(const char *filename,
 305                           const char *lock_filename, int fd,
 306                           const unsigned char *sha1)
 307 {
 308         char *hex = sha1_to_hex(sha1);
 309         char term = '\n';
 310         if (write(fd, hex, 40) < 40 ||
 311             write(fd, &term, 1) < 1) {
 312                 error("Couldn't write %s\n", filename);
 313                 close(fd);
 314                 return -1;
 315         }
 316         close(fd);
 317         rename(lock_filename, filename);
 318         return 0;
 319 }
 320
 321 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 322 {
 323         char *filename;
 324         char *lock_filename;
 325         int retval;
 326         if (fd < 0)
 327                 return -1;
 328         if (check_ref_format(ref))
 329                 return -1;
 330         filename = ref_file_name(ref);
 331         lock_filename = ref_lock_file_name(ref);
 332         retval = write_ref_file(filename, lock_filename, fd, sha1);
 333         free(filename);
 334         free(lock_filename);
 335         return retval;
 336 }
 337
 338 /*
 339  * Make sure "ref" is something reasonable to have under ".git/refs/";
 340  * We do not like it if:
 341  *
 342  * - any path component of it begins with ".", or
 343  * - it has double dots "..", or
 344  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 345  * - it ends with a "/".
 346  */
 347
 348 static inline int bad_ref_char(int ch)
 349 {
 350         return (((unsigned) ch) <= ' ' ||
 351                 ch == '~' || ch == '^' || ch == ':');
 352 }
 353
 354 int check_ref_format(const char *ref)
 355 {
 356         int ch, level;
 357         const char *cp = ref;
 358
 359         level = 0;
 360         while (1) {
 361                 while ((ch = *cp++) == '/')
 362                         ; /* tolerate duplicated slashes */
 363                 if (!ch)
 364                         return -1; /* should not end with slashes */
 365
 366                 /* we are at the beginning of the path component */
 367                 if (ch == '.' || bad_ref_char(ch))
 368                         return -1;
 369
 370                 /* scan the rest of the path component */
 371                 while ((ch = *cp++) != 0) {
 372                         if (bad_ref_char(ch))
 373                                 return -1;
 374                         if (ch == '/')
 375                                 break;
 376                         if (ch == '.' && *cp == '.')
 377                                 return -1;
 378                 }
 379                 level++;
 380                 if (!ch) {
 381                         if (level < 2)
 382                                 return -1; /* at least of form "heads/blah" */
 383                         return 0;
 384                 }
 385         }
 386 }
 387
 388 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 389 {
 390         char *filename;
 391         char *lock_filename;
 392         int fd;
 393         int retval;
 394         if (check_ref_format(ref))
 395                 return -1;
 396         filename = ref_file_name(ref);
 397         lock_filename = ref_lock_file_name(ref);
 398         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 399         if (fd < 0) {
 400                 error("Writing %s", lock_filename);
 401                 perror("Open");
 402         }
 403         retval = write_ref_file(filename, lock_filename, fd, sha1);
 404         free(filename);
 405         free(lock_filename);
 406         return retval;
 407 }