refs.c

   1 #include "refs.h"
   2 #include "cache.h"
   3
   4 #include <errno.h>
   5
   6 /* We allow "recursive" symbolic refs. Only within reason, though */
   7 #define MAXDEPTH 5
   8
   9 #ifndef USE_SYMLINK_HEAD
  10 #define USE_SYMLINK_HEAD 1
  11 #endif
  12
  13 int validate_symref(const char *path)
  14 {
  15         struct stat st;
  16         char *buf, buffer[256];
  17         int len, fd;
  18
  19         if (lstat(path, &st) < 0)
  20                 return -1;
  21
  22         /* Make sure it is a "refs/.." symlink */
  23         if (S_ISLNK(st.st_mode)) {
  24                 len = readlink(path, buffer, sizeof(buffer)-1);
  25                 if (len >= 5 && !memcmp("refs/", buffer, 5))
  26                         return 0;
  27                 return -1;
  28         }
  29
  30         /*
  31          * Anything else, just open it and try to see if it is a symbolic ref.
  32          */
  33         fd = open(path, O_RDONLY);
  34         if (fd < 0)
  35                 return -1;
  36         len = read(fd, buffer, sizeof(buffer)-1);
  37         close(fd);
  38
  39         /*
  40          * Is it a symbolic ref?
  41          */
  42         if (len < 4 || memcmp("ref:", buffer, 4))
  43                 return -1;
  44         buf = buffer + 4;
  45         len -= 4;
  46         while (len && isspace(*buf))
  47                 buf++, len--;
  48         if (len >= 5 && !memcmp("refs/", buf, 5))
  49                 return 0;
  50         return -1;
  51 }
  52
  53 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  54 {
  55         int depth = MAXDEPTH, len;
  56         char buffer[256];
  57
  58         for (;;) {
  59                 struct stat st;
  60                 char *buf;
  61                 int fd;
  62
  63                 if (--depth < 0)
  64                         return NULL;
  65
  66                 /* Special case: non-existing file.
  67                  * Not having the refs/heads/new-branch is OK
  68                  * if we are writing into it, so is .git/HEAD
  69                  * that points at refs/heads/master still to be
  70                  * born.  It is NOT OK if we are resolving for
  71                  * reading.
  72                  */
  73                 if (lstat(path, &st) < 0) {
  74                         if (reading || errno != ENOENT)
  75                                 return NULL;
  76                         memset(sha1, 0, 20);
  77                         return path;
  78                 }
  79
  80                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
  81                 if (S_ISLNK(st.st_mode)) {
  82                         len = readlink(path, buffer, sizeof(buffer)-1);
  83                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  84                                 path = git_path("%.*s", len, buffer);
  85                                 continue;
  86                         }
  87                 }
  88
  89                 /*
  90                  * Anything else, just open it and try to use it as
  91                  * a ref
  92                  */
  93                 fd = open(path, O_RDONLY);
  94                 if (fd < 0)
  95                         return NULL;
  96                 len = read(fd, buffer, sizeof(buffer)-1);
  97                 close(fd);
  98
  99                 /*
 100                  * Is it a symbolic ref?
 101                  */
 102                 if (len < 4 || memcmp("ref:", buffer, 4))
 103                         break;
 104                 buf = buffer + 4;
 105                 len -= 4;
 106                 while (len && isspace(*buf))
 107                         buf++, len--;
 108                 while (len && isspace(buf[len-1]))
 109                         buf[--len] = 0;
 110                 path = git_path("%.*s", len, buf);
 111         }
 112         if (len < 40 || get_sha1_hex(buffer, sha1))
 113                 return NULL;
 114         return path;
 115 }
 116
 117 int create_symref(const char *git_HEAD, const char *refs_heads_master)
 118 {
 119         const char *lockpath;
 120         char ref[1000];
 121         int fd, len, written;
 122
 123 #if USE_SYMLINK_HEAD
 124         unlink(git_HEAD);
 125         if (!symlink(refs_heads_master, git_HEAD))
 126                 return 0;
 127         fprintf(stderr, "no symlink - falling back to symbolic ref\n");
 128 #endif
 129
 130         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 131         if (sizeof(ref) <= len) {
 132                 error("refname too long: %s", refs_heads_master);
 133                 return -1;
 134         }
 135         lockpath = mkpath("%s.lock", git_HEAD);
 136         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
 137         written = write(fd, ref, len);
 138         close(fd);
 139         if (written != len) {
 140                 unlink(lockpath);
 141                 error("Unable to write to %s", lockpath);
 142                 return -2;
 143         }
 144         if (rename(lockpath, git_HEAD) < 0) {
 145                 unlink(lockpath);
 146                 error("Unable to create %s", git_HEAD);
 147                 return -3;
 148         }
 149         return 0;
 150 }
 151
 152 int read_ref(const char *filename, unsigned char *sha1)
 153 {
 154         if (resolve_ref(filename, sha1, 1))
 155                 return 0;
 156         return -1;
 157 }
 158
 159 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 160 {
 161         int retval = 0;
 162         DIR *dir = opendir(git_path("%s", base));
 163
 164         if (dir) {
 165                 struct dirent *de;
 166                 int baselen = strlen(base);
 167                 char *path = xmalloc(baselen + 257);
 168
 169                 if (!strncmp(base, "./", 2)) {
 170                         base += 2;
 171                         baselen -= 2;
 172                 }
 173                 memcpy(path, base, baselen);
 174                 if (baselen && base[baselen-1] != '/')
 175                         path[baselen++] = '/';
 176
 177                 while ((de = readdir(dir)) != NULL) {
 178                         unsigned char sha1[20];
 179                         struct stat st;
 180                         int namelen;
 181
 182                         if (de->d_name[0] == '.')
 183                                 continue;
 184                         namelen = strlen(de->d_name);
 185                         if (namelen > 255)
 186                                 continue;
 187                         memcpy(path + baselen, de->d_name, namelen+1);
 188                         if (stat(git_path("%s", path), &st) < 0)
 189                                 continue;
 190                         if (S_ISDIR(st.st_mode)) {
 191                                 retval = do_for_each_ref(path, fn);
 192                                 if (retval)
 193                                         break;
 194                                 continue;
 195                         }
 196                         if (read_ref(git_path("%s", path), sha1) < 0)
 197                                 continue;
 198                         if (!has_sha1_file(sha1))
 199                                 continue;
 200                         retval = fn(path, sha1);
 201                         if (retval)
 202                                 break;
 203                 }
 204                 free(path);
 205                 closedir(dir);
 206         }
 207         return retval;
 208 }
 209
 210 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 211 {
 212         unsigned char sha1[20];
 213         if (!read_ref(git_path("HEAD"), sha1))
 214                 return fn("HEAD", sha1);
 215         return 0;
 216 }
 217
 218 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 219 {
 220         return do_for_each_ref("refs", fn);
 221 }
 222
 223 static char *ref_file_name(const char *ref)
 224 {
 225         char *base = get_refs_directory();
 226         int baselen = strlen(base);
 227         int reflen = strlen(ref);
 228         char *ret = xmalloc(baselen + 2 + reflen);
 229         sprintf(ret, "%s/%s", base, ref);
 230         return ret;
 231 }
 232
 233 static char *ref_lock_file_name(const char *ref)
 234 {
 235         char *base = get_refs_directory();
 236         int baselen = strlen(base);
 237         int reflen = strlen(ref);
 238         char *ret = xmalloc(baselen + 7 + reflen);
 239         sprintf(ret, "%s/%s.lock", base, ref);
 240         return ret;
 241 }
 242
 243 int get_ref_sha1(const char *ref, unsigned char *sha1)
 244 {
 245         const char *filename;
 246
 247         if (check_ref_format(ref))
 248                 return -1;
 249         filename = git_path("refs/%s", ref);
 250         return read_ref(filename, sha1);
 251 }
 252
 253 static int lock_ref_file(const char *filename, const char *lock_filename,
 254                          const unsigned char *old_sha1)
 255 {
 256         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 257         unsigned char current_sha1[20];
 258         int retval;
 259         if (fd < 0) {
 260                 return error("Couldn't open lock file for %s: %s",
 261                              filename, strerror(errno));
 262         }
 263         retval = read_ref(filename, current_sha1);
 264         if (old_sha1) {
 265                 if (retval) {
 266                         close(fd);
 267                         unlink(lock_filename);
 268                         return error("Could not read the current value of %s",
 269                                      filename);
 270                 }
 271                 if (memcmp(current_sha1, old_sha1, 20)) {
 272                         close(fd);
 273                         unlink(lock_filename);
 274                         error("The current value of %s is %s",
 275                               filename, sha1_to_hex(current_sha1));
 276                         return error("Expected %s",
 277                                      sha1_to_hex(old_sha1));
 278                 }
 279         } else {
 280                 if (!retval) {
 281                         close(fd);
 282                         unlink(lock_filename);
 283                         return error("Unexpectedly found a value of %s for %s",
 284                                      sha1_to_hex(current_sha1), filename);
 285                 }
 286         }
 287         return fd;
 288 }
 289
 290 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 291 {
 292         char *filename;
 293         char *lock_filename;
 294         int retval;
 295         if (check_ref_format(ref))
 296                 return -1;
 297         filename = ref_file_name(ref);
 298         lock_filename = ref_lock_file_name(ref);
 299         retval = lock_ref_file(filename, lock_filename, old_sha1);
 300         free(filename);
 301         free(lock_filename);
 302         return retval;
 303 }
 304
 305 static int write_ref_file(const char *filename,
 306                           const char *lock_filename, int fd,
 307                           const unsigned char *sha1)
 308 {
 309         char *hex = sha1_to_hex(sha1);
 310         char term = '\n';
 311         if (write(fd, hex, 40) < 40 ||
 312             write(fd, &term, 1) < 1) {
 313                 error("Couldn't write %s\n", filename);
 314                 close(fd);
 315                 return -1;
 316         }
 317         close(fd);
 318         rename(lock_filename, filename);
 319         return 0;
 320 }
 321
 322 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 323 {
 324         char *filename;
 325         char *lock_filename;
 326         int retval;
 327         if (fd < 0)
 328                 return -1;
 329         if (check_ref_format(ref))
 330                 return -1;
 331         filename = ref_file_name(ref);
 332         lock_filename = ref_lock_file_name(ref);
 333         retval = write_ref_file(filename, lock_filename, fd, sha1);
 334         free(filename);
 335         free(lock_filename);
 336         return retval;
 337 }
 338
 339 /*
 340  * Make sure "ref" is something reasonable to have under ".git/refs/";
 341  * We do not like it if:
 342  *
 343  * - any path component of it begins with ".", or
 344  * - it has double dots "..", or
 345  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 346  * - it ends with a "/".
 347  */
 348
 349 static inline int bad_ref_char(int ch)
 350 {
 351         return (((unsigned) ch) <= ' ' ||
 352                 ch == '~' || ch == '^' || ch == ':');
 353 }
 354
 355 int check_ref_format(const char *ref)
 356 {
 357         int ch, level;
 358         const char *cp = ref;
 359
 360         level = 0;
 361         while (1) {
 362                 while ((ch = *cp++) == '/')
 363                         ; /* tolerate duplicated slashes */
 364                 if (!ch)
 365                         return -1; /* should not end with slashes */
 366
 367                 /* we are at the beginning of the path component */
 368                 if (ch == '.' || bad_ref_char(ch))
 369                         return -1;
 370
 371                 /* scan the rest of the path component */
 372                 while ((ch = *cp++) != 0) {
 373                         if (bad_ref_char(ch))
 374                                 return -1;
 375                         if (ch == '/')
 376                                 break;
 377                         if (ch == '.' && *cp == '.')
 378                                 return -1;
 379                 }
 380                 level++;
 381                 if (!ch) {
 382                         if (level < 2)
 383                                 return -1; /* at least of form "heads/blah" */
 384                         return 0;
 385                 }
 386         }
 387 }
 388
 389 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 390 {
 391         char *filename;
 392         char *lock_filename;
 393         int fd;
 394         int retval;
 395         if (check_ref_format(ref))
 396                 return -1;
 397         filename = ref_file_name(ref);
 398         lock_filename = ref_lock_file_name(ref);
 399         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 400         if (fd < 0) {
 401                 error("Writing %s", lock_filename);
 402                 perror("Open");
 403         }
 404         retval = write_ref_file(filename, lock_filename, fd, sha1);
 405         free(filename);
 406         free(lock_filename);
 407         return retval;
 408 }