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         if (!only_use_symrefs) {
 125                 unlink(git_HEAD);
 126                 if (!symlink(refs_heads_master, git_HEAD))
 127                         return 0;
 128                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
 129         }
 130 #endif
 131
 132         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 133         if (sizeof(ref) <= len) {
 134                 error("refname too long: %s", refs_heads_master);
 135                 return -1;
 136         }
 137         lockpath = mkpath("%s.lock", git_HEAD);
 138         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
 139         written = write(fd, ref, len);
 140         close(fd);
 141         if (written != len) {
 142                 unlink(lockpath);
 143                 error("Unable to write to %s", lockpath);
 144                 return -2;
 145         }
 146         if (rename(lockpath, git_HEAD) < 0) {
 147                 unlink(lockpath);
 148                 error("Unable to create %s", git_HEAD);
 149                 return -3;
 150         }
 151         return 0;
 152 }
 153
 154 int read_ref(const char *filename, unsigned char *sha1)
 155 {
 156         if (resolve_ref(filename, sha1, 1))
 157                 return 0;
 158         return -1;
 159 }
 160
 161 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 162 {
 163         int retval = 0;
 164         DIR *dir = opendir(git_path("%s", base));
 165
 166         if (dir) {
 167                 struct dirent *de;
 168                 int baselen = strlen(base);
 169                 char *path = xmalloc(baselen + 257);
 170
 171                 if (!strncmp(base, "./", 2)) {
 172                         base += 2;
 173                         baselen -= 2;
 174                 }
 175                 memcpy(path, base, baselen);
 176                 if (baselen && base[baselen-1] != '/')
 177                         path[baselen++] = '/';
 178
 179                 while ((de = readdir(dir)) != NULL) {
 180                         unsigned char sha1[20];
 181                         struct stat st;
 182                         int namelen;
 183
 184                         if (de->d_name[0] == '.')
 185                                 continue;
 186                         namelen = strlen(de->d_name);
 187                         if (namelen > 255)
 188                                 continue;
 189                         memcpy(path + baselen, de->d_name, namelen+1);
 190                         if (stat(git_path("%s", path), &st) < 0)
 191                                 continue;
 192                         if (S_ISDIR(st.st_mode)) {
 193                                 retval = do_for_each_ref(path, fn);
 194                                 if (retval)
 195                                         break;
 196                                 continue;
 197                         }
 198                         if (read_ref(git_path("%s", path), sha1) < 0)
 199                                 continue;
 200                         if (!has_sha1_file(sha1))
 201                                 continue;
 202                         retval = fn(path, sha1);
 203                         if (retval)
 204                                 break;
 205                 }
 206                 free(path);
 207                 closedir(dir);
 208         }
 209         return retval;
 210 }
 211
 212 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 213 {
 214         unsigned char sha1[20];
 215         if (!read_ref(git_path("HEAD"), sha1))
 216                 return fn("HEAD", sha1);
 217         return 0;
 218 }
 219
 220 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 221 {
 222         return do_for_each_ref("refs", fn);
 223 }
 224
 225 static char *ref_file_name(const char *ref)
 226 {
 227         char *base = get_refs_directory();
 228         int baselen = strlen(base);
 229         int reflen = strlen(ref);
 230         char *ret = xmalloc(baselen + 2 + reflen);
 231         sprintf(ret, "%s/%s", base, ref);
 232         return ret;
 233 }
 234
 235 static char *ref_lock_file_name(const char *ref)
 236 {
 237         char *base = get_refs_directory();
 238         int baselen = strlen(base);
 239         int reflen = strlen(ref);
 240         char *ret = xmalloc(baselen + 7 + reflen);
 241         sprintf(ret, "%s/%s.lock", base, ref);
 242         return ret;
 243 }
 244
 245 int get_ref_sha1(const char *ref, unsigned char *sha1)
 246 {
 247         const char *filename;
 248
 249         if (check_ref_format(ref))
 250                 return -1;
 251         filename = git_path("refs/%s", ref);
 252         return read_ref(filename, sha1);
 253 }
 254
 255 static int lock_ref_file(const char *filename, const char *lock_filename,
 256                          const unsigned char *old_sha1)
 257 {
 258         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 259         unsigned char current_sha1[20];
 260         int retval;
 261         if (fd < 0) {
 262                 return error("Couldn't open lock file for %s: %s",
 263                              filename, strerror(errno));
 264         }
 265         retval = read_ref(filename, current_sha1);
 266         if (old_sha1) {
 267                 if (retval) {
 268                         close(fd);
 269                         unlink(lock_filename);
 270                         return error("Could not read the current value of %s",
 271                                      filename);
 272                 }
 273                 if (memcmp(current_sha1, old_sha1, 20)) {
 274                         close(fd);
 275                         unlink(lock_filename);
 276                         error("The current value of %s is %s",
 277                               filename, sha1_to_hex(current_sha1));
 278                         return error("Expected %s",
 279                                      sha1_to_hex(old_sha1));
 280                 }
 281         } else {
 282                 if (!retval) {
 283                         close(fd);
 284                         unlink(lock_filename);
 285                         return error("Unexpectedly found a value of %s for %s",
 286                                      sha1_to_hex(current_sha1), filename);
 287                 }
 288         }
 289         return fd;
 290 }
 291
 292 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 293 {
 294         char *filename;
 295         char *lock_filename;
 296         int retval;
 297         if (check_ref_format(ref))
 298                 return -1;
 299         filename = ref_file_name(ref);
 300         lock_filename = ref_lock_file_name(ref);
 301         retval = lock_ref_file(filename, lock_filename, old_sha1);
 302         free(filename);
 303         free(lock_filename);
 304         return retval;
 305 }
 306
 307 static int write_ref_file(const char *filename,
 308                           const char *lock_filename, int fd,
 309                           const unsigned char *sha1)
 310 {
 311         char *hex = sha1_to_hex(sha1);
 312         char term = '\n';
 313         if (write(fd, hex, 40) < 40 ||
 314             write(fd, &term, 1) < 1) {
 315                 error("Couldn't write %s\n", filename);
 316                 close(fd);
 317                 return -1;
 318         }
 319         close(fd);
 320         rename(lock_filename, filename);
 321         return 0;
 322 }
 323
 324 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 325 {
 326         char *filename;
 327         char *lock_filename;
 328         int retval;
 329         if (fd < 0)
 330                 return -1;
 331         if (check_ref_format(ref))
 332                 return -1;
 333         filename = ref_file_name(ref);
 334         lock_filename = ref_lock_file_name(ref);
 335         retval = write_ref_file(filename, lock_filename, fd, sha1);
 336         free(filename);
 337         free(lock_filename);
 338         return retval;
 339 }
 340
 341 /*
 342  * Make sure "ref" is something reasonable to have under ".git/refs/";
 343  * We do not like it if:
 344  *
 345  * - any path component of it begins with ".", or
 346  * - it has double dots "..", or
 347  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 348  * - it ends with a "/".
 349  */
 350
 351 static inline int bad_ref_char(int ch)
 352 {
 353         return (((unsigned) ch) <= ' ' ||
 354                 ch == '~' || ch == '^' || ch == ':');
 355 }
 356
 357 int check_ref_format(const char *ref)
 358 {
 359         int ch, level;
 360         const char *cp = ref;
 361
 362         level = 0;
 363         while (1) {
 364                 while ((ch = *cp++) == '/')
 365                         ; /* tolerate duplicated slashes */
 366                 if (!ch)
 367                         return -1; /* should not end with slashes */
 368
 369                 /* we are at the beginning of the path component */
 370                 if (ch == '.' || bad_ref_char(ch))
 371                         return -1;
 372
 373                 /* scan the rest of the path component */
 374                 while ((ch = *cp++) != 0) {
 375                         if (bad_ref_char(ch))
 376                                 return -1;
 377                         if (ch == '/')
 378                                 break;
 379                         if (ch == '.' && *cp == '.')
 380                                 return -1;
 381                 }
 382                 level++;
 383                 if (!ch) {
 384                         if (level < 2)
 385                                 return -1; /* at least of form "heads/blah" */
 386                         return 0;
 387                 }
 388         }
 389 }
 390
 391 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 392 {
 393         char *filename;
 394         char *lock_filename;
 395         int fd;
 396         int retval;
 397         if (check_ref_format(ref))
 398                 return -1;
 399         filename = ref_file_name(ref);
 400         lock_filename = ref_lock_file_name(ref);
 401         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 402         if (fd < 0) {
 403                 error("Writing %s", lock_filename);
 404                 perror("Open");
 405         }
 406         retval = write_ref_file(filename, lock_filename, fd, sha1);
 407         free(filename);
 408         free(lock_filename);
 409         return retval;
 410 }