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 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
  10 {
  11         int depth = MAXDEPTH, len;
  12         char buffer[256];
  13
  14         for (;;) {
  15                 struct stat st;
  16                 char *buf;
  17                 int fd;
  18
  19                 if (--depth < 0)
  20                         return NULL;
  21
  22                 /* Special case: non-existing file.
  23                  * Not having the refs/heads/new-branch is OK
  24                  * if we are writing into it, so is .git/HEAD
  25                  * that points at refs/heads/master still to be
  26                  * born.  It is NOT OK if we are resolving for
  27                  * reading.
  28                  */
  29                 if (lstat(path, &st) < 0) {
  30                         if (reading || errno != ENOENT)
  31                                 return NULL;
  32                         memset(sha1, 0, 20);
  33                         return path;
  34                 }
  35
  36                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
  37                 if (S_ISLNK(st.st_mode)) {
  38                         len = readlink(path, buffer, sizeof(buffer)-1);
  39                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
  40                                 path = git_path("%.*s", len, buffer);
  41                                 continue;
  42                         }
  43                 }
  44
  45                 /*
  46                  * Anything else, just open it and try to use it as
  47                  * a ref
  48                  */
  49                 fd = open(path, O_RDONLY);
  50                 if (fd < 0)
  51                         return NULL;
  52                 len = read(fd, buffer, sizeof(buffer)-1);
  53                 close(fd);
  54
  55                 /*
  56                  * Is it a symbolic ref?
  57                  */
  58                 if (len < 4 || memcmp("ref:", buffer, 4))
  59                         break;
  60                 buf = buffer + 4;
  61                 len -= 4;
  62                 while (len && isspace(*buf))
  63                         buf++, len--;
  64                 while (len && isspace(buf[len-1]))
  65                         buf[--len] = 0;
  66                 path = git_path("%.*s", len, buf);
  67         }
  68         if (len < 40 || get_sha1_hex(buffer, sha1))
  69                 return NULL;
  70         return path;
  71 }
  72
  73 int create_symref(const char *git_HEAD, const char *refs_heads_master)
  74 {
  75         const char *lockpath;
  76         char ref[1000];
  77         int fd, len, written;
  78
  79 #ifndef NO_SYMLINK_HEAD
  80         if (prefer_symlink_refs) {
  81                 unlink(git_HEAD);
  82                 if (!symlink(refs_heads_master, git_HEAD))
  83                         return 0;
  84                 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
  85         }
  86 #endif
  87
  88         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
  89         if (sizeof(ref) <= len) {
  90                 error("refname too long: %s", refs_heads_master);
  91                 return -1;
  92         }
  93         lockpath = mkpath("%s.lock", git_HEAD);
  94         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
  95         written = write(fd, ref, len);
  96         close(fd);
  97         if (written != len) {
  98                 unlink(lockpath);
  99                 error("Unable to write to %s", lockpath);
 100                 return -2;
 101         }
 102         if (rename(lockpath, git_HEAD) < 0) {
 103                 unlink(lockpath);
 104                 error("Unable to create %s", git_HEAD);
 105                 return -3;
 106         }
 107         return 0;
 108 }
 109
 110 int read_ref(const char *filename, unsigned char *sha1)
 111 {
 112         if (resolve_ref(filename, sha1, 1))
 113                 return 0;
 114         return -1;
 115 }
 116
 117 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1), int trim)
 118 {
 119         int retval = 0;
 120         DIR *dir = opendir(git_path("%s", base));
 121
 122         if (dir) {
 123                 struct dirent *de;
 124                 int baselen = strlen(base);
 125                 char *path = xmalloc(baselen + 257);
 126
 127                 if (!strncmp(base, "./", 2)) {
 128                         base += 2;
 129                         baselen -= 2;
 130                 }
 131                 memcpy(path, base, baselen);
 132                 if (baselen && base[baselen-1] != '/')
 133                         path[baselen++] = '/';
 134
 135                 while ((de = readdir(dir)) != NULL) {
 136                         unsigned char sha1[20];
 137                         struct stat st;
 138                         int namelen;
 139
 140                         if (de->d_name[0] == '.')
 141                                 continue;
 142                         namelen = strlen(de->d_name);
 143                         if (namelen > 255)
 144                                 continue;
 145                         memcpy(path + baselen, de->d_name, namelen+1);
 146                         if (stat(git_path("%s", path), &st) < 0)
 147                                 continue;
 148                         if (S_ISDIR(st.st_mode)) {
 149                                 retval = do_for_each_ref(path, fn, trim);
 150                                 if (retval)
 151                                         break;
 152                                 continue;
 153                         }
 154                         if (read_ref(git_path("%s", path), sha1) < 0) {
 155                                 error("%s points nowhere!", path);
 156                                 continue;
 157                         }
 158                         if (!has_sha1_file(sha1)) {
 159                                 error("%s does not point to a valid "
 160                                       "commit object!", path);
 161                                 continue;
 162                         }
 163                         retval = fn(path + trim, sha1);
 164                         if (retval)
 165                                 break;
 166                 }
 167                 free(path);
 168                 closedir(dir);
 169         }
 170         return retval;
 171 }
 172
 173 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 174 {
 175         unsigned char sha1[20];
 176         if (!read_ref(git_path("HEAD"), sha1))
 177                 return fn("HEAD", sha1);
 178         return 0;
 179 }
 180
 181 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 182 {
 183         return do_for_each_ref("refs", fn, 0);
 184 }
 185
 186 int for_each_tag_ref(int (*fn)(const char *path, const unsigned char *sha1))
 187 {
 188         return do_for_each_ref("refs/tags", fn, 10);
 189 }
 190
 191 int for_each_branch_ref(int (*fn)(const char *path, const unsigned char *sha1))
 192 {
 193         return do_for_each_ref("refs/heads", fn, 11);
 194 }
 195
 196 int for_each_remote_ref(int (*fn)(const char *path, const unsigned char *sha1))
 197 {
 198         return do_for_each_ref("refs/remotes", fn, 13);
 199 }
 200
 201 int get_ref_sha1(const char *ref, unsigned char *sha1)
 202 {
 203         if (check_ref_format(ref))
 204                 return -1;
 205         return read_ref(git_path("refs/%s", ref), sha1);
 206 }
 207
 208 /*
 209  * Make sure "ref" is something reasonable to have under ".git/refs/";
 210  * We do not like it if:
 211  *
 212  * - any path component of it begins with ".", or
 213  * - it has double dots "..", or
 214  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 215  * - it ends with a "/".
 216  */
 217
 218 static inline int bad_ref_char(int ch)
 219 {
 220         return (((unsigned) ch) <= ' ' ||
 221                 ch == '~' || ch == '^' || ch == ':' ||
 222                 /* 2.13 Pattern Matching Notation */
 223                 ch == '?' || ch == '*' || ch == '[');
 224 }
 225
 226 int check_ref_format(const char *ref)
 227 {
 228         int ch, level;
 229         const char *cp = ref;
 230
 231         level = 0;
 232         while (1) {
 233                 while ((ch = *cp++) == '/')
 234                         ; /* tolerate duplicated slashes */
 235                 if (!ch)
 236                         return -1; /* should not end with slashes */
 237
 238                 /* we are at the beginning of the path component */
 239                 if (ch == '.' || bad_ref_char(ch))
 240                         return -1;
 241
 242                 /* scan the rest of the path component */
 243                 while ((ch = *cp++) != 0) {
 244                         if (bad_ref_char(ch))
 245                                 return -1;
 246                         if (ch == '/')
 247                                 break;
 248                         if (ch == '.' && *cp == '.')
 249                                 return -1;
 250                 }
 251                 level++;
 252                 if (!ch) {
 253                         if (level < 2)
 254                                 return -1; /* at least of form "heads/blah" */
 255                         return 0;
 256                 }
 257         }
 258 }
 259
 260 static struct ref_lock* verify_lock(struct ref_lock *lock,
 261         const unsigned char *old_sha1, int mustexist)
 262 {
 263         char buf[40];
 264         int nr, fd = open(lock->ref_file, O_RDONLY);
 265         if (fd < 0 && (mustexist || errno != ENOENT)) {
 266                 error("Can't verify ref %s", lock->ref_file);
 267                 unlock_ref(lock);
 268                 return NULL;
 269         }
 270         nr = read(fd, buf, 40);
 271         close(fd);
 272         if (nr != 40 || get_sha1_hex(buf, lock->old_sha1) < 0) {
 273                 error("Can't verify ref %s", lock->ref_file);
 274                 unlock_ref(lock);
 275                 return NULL;
 276         }
 277         if (memcmp(lock->old_sha1, old_sha1, 20)) {
 278                 error("Ref %s is at %s but expected %s", lock->ref_file,
 279                         sha1_to_hex(lock->old_sha1), sha1_to_hex(old_sha1));
 280                 unlock_ref(lock);
 281                 return NULL;
 282         }
 283         return lock;
 284 }
 285
 286 static struct ref_lock* lock_ref_sha1_basic(const char *path,
 287         int plen,
 288         const unsigned char *old_sha1, int mustexist)
 289 {
 290         struct ref_lock *lock;
 291
 292         lock = xcalloc(1, sizeof(struct ref_lock));
 293         lock->lock_fd = -1;
 294
 295         plen = strlen(path) - plen;
 296         path = resolve_ref(path, lock->old_sha1, mustexist);
 297         if (!path) {
 298                 error("Can't read ref %s", path);
 299                 unlock_ref(lock);
 300                 return NULL;
 301         }
 302
 303         lock->ref_file = strdup(path);
 304         lock->lock_file = strdup(mkpath("%s.lock", lock->ref_file));
 305
 306         if (safe_create_leading_directories(lock->lock_file))
 307                 die("unable to create directory for %s", lock->lock_file);
 308         lock->lock_fd = open(lock->lock_file,
 309                 O_WRONLY | O_CREAT | O_EXCL, 0666);
 310         if (lock->lock_fd < 0) {
 311                 error("Couldn't open lock file %s: %s",
 312                         lock->lock_file, strerror(errno));
 313                 unlock_ref(lock);
 314                 return NULL;
 315         }
 316
 317         return old_sha1 ? verify_lock(lock, old_sha1, mustexist) : lock;
 318 }
 319
 320 struct ref_lock* lock_ref_sha1(const char *ref,
 321         const unsigned char *old_sha1, int mustexist)
 322 {
 323         if (check_ref_format(ref))
 324                 return NULL;
 325         return lock_ref_sha1_basic(git_path("refs/%s", ref),
 326                 strlen(ref), old_sha1, mustexist);
 327 }
 328
 329 struct ref_lock* lock_any_ref_for_update(const char *ref,
 330         const unsigned char *old_sha1, int mustexist)
 331 {
 332         return lock_ref_sha1_basic(git_path("%s", ref),
 333                 strlen(ref), old_sha1, mustexist);
 334 }
 335
 336 void unlock_ref (struct ref_lock *lock)
 337 {
 338         if (lock->lock_fd >= 0) {
 339                 close(lock->lock_fd);
 340                 unlink(lock->lock_file);
 341         }
 342         if (lock->ref_file)
 343                 free(lock->ref_file);
 344         if (lock->lock_file)
 345                 free(lock->lock_file);
 346         free(lock);
 347 }
 348
 349 int write_ref_sha1(struct ref_lock *lock,
 350         const unsigned char *sha1, const char *logmsg)
 351 {
 352         static char term = '\n';
 353
 354         if (!lock)
 355                 return -1;
 356         if (!memcmp(lock->old_sha1, sha1, 20)) {
 357                 unlock_ref(lock);
 358                 return 0;
 359         }
 360         if (write(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 ||
 361             write(lock->lock_fd, &term, 1) != 1
 362                 || close(lock->lock_fd) < 0) {
 363                 error("Couldn't write %s", lock->lock_file);
 364                 unlock_ref(lock);
 365                 return -1;
 366         }
 367         if (rename(lock->lock_file, lock->ref_file) < 0) {
 368                 error("Couldn't set %s", lock->ref_file);
 369                 unlock_ref(lock);
 370                 return -1;
 371         }
 372         lock->lock_fd = -1;
 373         unlock_ref(lock);
 374         return 0;
 375 }