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 #if USE_SYMLINK_HEAD
 120         unlink(git_HEAD);
 121         return symlink(refs_heads_master, git_HEAD);
 122 #else
 123         const char *lockpath;
 124         char ref[1000];
 125         int fd, len, written;
 126
 127         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
 128         if (sizeof(ref) <= len) {
 129                 error("refname too long: %s", refs_heads_master);
 130                 return -1;
 131         }
 132         lockpath = mkpath("%s.lock", git_HEAD);
 133         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
 134         written = write(fd, ref, len);
 135         close(fd);
 136         if (written != len) {
 137                 unlink(lockpath);
 138                 error("Unable to write to %s", lockpath);
 139                 return -2;
 140         }
 141         if (rename(lockpath, git_HEAD) < 0) {
 142                 unlink(lockpath);
 143                 error("Unable to create %s", git_HEAD);
 144                 return -3;
 145         }
 146         return 0;
 147 #endif
 148 }
 149
 150 int read_ref(const char *filename, unsigned char *sha1)
 151 {
 152         if (resolve_ref(filename, sha1, 1))
 153                 return 0;
 154         return -1;
 155 }
 156
 157 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
 158 {
 159         int retval = 0;
 160         DIR *dir = opendir(git_path("%s", base));
 161
 162         if (dir) {
 163                 struct dirent *de;
 164                 int baselen = strlen(base);
 165                 char *path = xmalloc(baselen + 257);
 166
 167                 if (!strncmp(base, "./", 2)) {
 168                         base += 2;
 169                         baselen -= 2;
 170                 }
 171                 memcpy(path, base, baselen);
 172                 if (baselen && base[baselen-1] != '/')
 173                         path[baselen++] = '/';
 174
 175                 while ((de = readdir(dir)) != NULL) {
 176                         unsigned char sha1[20];
 177                         struct stat st;
 178                         int namelen;
 179
 180                         if (de->d_name[0] == '.')
 181                                 continue;
 182                         namelen = strlen(de->d_name);
 183                         if (namelen > 255)
 184                                 continue;
 185                         memcpy(path + baselen, de->d_name, namelen+1);
 186                         if (stat(git_path("%s", path), &st) < 0)
 187                                 continue;
 188                         if (S_ISDIR(st.st_mode)) {
 189                                 retval = do_for_each_ref(path, fn);
 190                                 if (retval)
 191                                         break;
 192                                 continue;
 193                         }
 194                         if (read_ref(git_path("%s", path), sha1) < 0)
 195                                 continue;
 196                         if (!has_sha1_file(sha1))
 197                                 continue;
 198                         retval = fn(path, sha1);
 199                         if (retval)
 200                                 break;
 201                 }
 202                 free(path);
 203                 closedir(dir);
 204         }
 205         return retval;
 206 }
 207
 208 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
 209 {
 210         unsigned char sha1[20];
 211         if (!read_ref(git_path("HEAD"), sha1))
 212                 return fn("HEAD", sha1);
 213         return 0;
 214 }
 215
 216 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
 217 {
 218         return do_for_each_ref("refs", fn);
 219 }
 220
 221 static char *ref_file_name(const char *ref)
 222 {
 223         char *base = get_refs_directory();
 224         int baselen = strlen(base);
 225         int reflen = strlen(ref);
 226         char *ret = xmalloc(baselen + 2 + reflen);
 227         sprintf(ret, "%s/%s", base, ref);
 228         return ret;
 229 }
 230
 231 static char *ref_lock_file_name(const char *ref)
 232 {
 233         char *base = get_refs_directory();
 234         int baselen = strlen(base);
 235         int reflen = strlen(ref);
 236         char *ret = xmalloc(baselen + 7 + reflen);
 237         sprintf(ret, "%s/%s.lock", base, ref);
 238         return ret;
 239 }
 240
 241 int get_ref_sha1(const char *ref, unsigned char *sha1)
 242 {
 243         const char *filename;
 244
 245         if (check_ref_format(ref))
 246                 return -1;
 247         filename = git_path("refs/%s", ref);
 248         return read_ref(filename, sha1);
 249 }
 250
 251 static int lock_ref_file(const char *filename, const char *lock_filename,
 252                          const unsigned char *old_sha1)
 253 {
 254         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 255         unsigned char current_sha1[20];
 256         int retval;
 257         if (fd < 0) {
 258                 return error("Couldn't open lock file for %s: %s",
 259                              filename, strerror(errno));
 260         }
 261         retval = read_ref(filename, current_sha1);
 262         if (old_sha1) {
 263                 if (retval) {
 264                         close(fd);
 265                         unlink(lock_filename);
 266                         return error("Could not read the current value of %s",
 267                                      filename);
 268                 }
 269                 if (memcmp(current_sha1, old_sha1, 20)) {
 270                         close(fd);
 271                         unlink(lock_filename);
 272                         error("The current value of %s is %s",
 273                               filename, sha1_to_hex(current_sha1));
 274                         return error("Expected %s",
 275                                      sha1_to_hex(old_sha1));
 276                 }
 277         } else {
 278                 if (!retval) {
 279                         close(fd);
 280                         unlink(lock_filename);
 281                         return error("Unexpectedly found a value of %s for %s",
 282                                      sha1_to_hex(current_sha1), filename);
 283                 }
 284         }
 285         return fd;
 286 }
 287
 288 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
 289 {
 290         char *filename;
 291         char *lock_filename;
 292         int retval;
 293         if (check_ref_format(ref))
 294                 return -1;
 295         filename = ref_file_name(ref);
 296         lock_filename = ref_lock_file_name(ref);
 297         retval = lock_ref_file(filename, lock_filename, old_sha1);
 298         free(filename);
 299         free(lock_filename);
 300         return retval;
 301 }
 302
 303 static int write_ref_file(const char *filename,
 304                           const char *lock_filename, int fd,
 305                           const unsigned char *sha1)
 306 {
 307         char *hex = sha1_to_hex(sha1);
 308         char term = '\n';
 309         if (write(fd, hex, 40) < 40 ||
 310             write(fd, &term, 1) < 1) {
 311                 error("Couldn't write %s\n", filename);
 312                 close(fd);
 313                 return -1;
 314         }
 315         close(fd);
 316         rename(lock_filename, filename);
 317         return 0;
 318 }
 319
 320 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 321 {
 322         char *filename;
 323         char *lock_filename;
 324         int retval;
 325         if (fd < 0)
 326                 return -1;
 327         if (check_ref_format(ref))
 328                 return -1;
 329         filename = ref_file_name(ref);
 330         lock_filename = ref_lock_file_name(ref);
 331         retval = write_ref_file(filename, lock_filename, fd, sha1);
 332         free(filename);
 333         free(lock_filename);
 334         return retval;
 335 }
 336
 337 /*
 338  * Make sure "ref" is something reasonable to have under ".git/refs/";
 339  * We do not like it if:
 340  *
 341  * - any path component of it begins with ".", or
 342  * - it has double dots "..", or
 343  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
 344  * - it ends with a "/".
 345  */
 346
 347 static inline int bad_ref_char(int ch)
 348 {
 349         return (((unsigned) ch) <= ' ' ||
 350                 ch == '~' || ch == '^' || ch == ':');
 351 }
 352
 353 int check_ref_format(const char *ref)
 354 {
 355         int ch, level;
 356         const char *cp = ref;
 357
 358         level = 0;
 359         while (1) {
 360                 while ((ch = *cp++) == '/')
 361                         ; /* tolerate duplicated slashes */
 362                 if (!ch)
 363                         return -1; /* should not end with slashes */
 364
 365                 /* we are at the beginning of the path component */
 366                 if (ch == '.' || bad_ref_char(ch))
 367                         return -1;
 368
 369                 /* scan the rest of the path component */
 370                 while ((ch = *cp++) != 0) {
 371                         if (bad_ref_char(ch))
 372                                 return -1;
 373                         if (ch == '/')
 374                                 break;
 375                         if (ch == '.' && *cp == '.')
 376                                 return -1;
 377                 }
 378                 level++;
 379                 if (!ch) {
 380                         if (level < 2)
 381                                 return -1; /* at least of form "heads/blah" */
 382                         return 0;
 383                 }
 384         }
 385 }
 386
 387 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
 388 {
 389         char *filename;
 390         char *lock_filename;
 391         int fd;
 392         int retval;
 393         if (check_ref_format(ref))
 394                 return -1;
 395         filename = ref_file_name(ref);
 396         lock_filename = ref_lock_file_name(ref);
 397         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
 398         if (fd < 0) {
 399                 error("Writing %s", lock_filename);
 400                 perror("Open");
 401         }
 402         retval = write_ref_file(filename, lock_filename, fd, sha1);
 403         free(filename);
 404         free(lock_filename);
 405         return retval;
 406 }