path.c

   1 /*
   2  * I'm tired of doing "vsnprintf()" etc just to open a
   3  * file, so here's a "return static buffer with printf"
   4  * interface for paths.
   5  *
   6  * It's obviously not thread-safe. Sue me. But it's quite
   7  * useful for doing things like
   8  *
   9  *   f = open(mkpath("%s/%s.git", base, name), O_RDONLY);
  10  *
  11  * which is what it's designed for.
  12  */
  13 #include "cache.h"
  14
  15 static char bad_path[] = "/bad-path/";
  16
  17 static char *get_pathname(void)
  18 {
  19         static char pathname_array[4][PATH_MAX];
  20         static int index;
  21         return pathname_array[3 & ++index];
  22 }
  23
  24 static char *cleanup_path(char *path)
  25 {
  26         /* Clean it up */
  27         if (!memcmp(path, "./", 2)) {
  28                 path += 2;
  29                 while (*path == '/')
  30                         path++;
  31         }
  32         return path;
  33 }
  34
  35 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  36 {
  37         va_list args;
  38         unsigned len;
  39
  40         va_start(args, fmt);
  41         len = vsnprintf(buf, n, fmt, args);
  42         va_end(args);
  43         if (len >= n) {
  44                 strlcpy(buf, bad_path, n);
  45                 return buf;
  46         }
  47         return cleanup_path(buf);
  48 }
  49
  50 static char *git_vsnpath(char *buf, size_t n, const char *fmt, va_list args)
  51 {
  52         const char *git_dir = get_git_dir();
  53         size_t len;
  54
  55         len = strlen(git_dir);
  56         if (n < len + 1)
  57                 goto bad;
  58         memcpy(buf, git_dir, len);
  59         if (len && !is_dir_sep(git_dir[len-1]))
  60                 buf[len++] = '/';
  61         len += vsnprintf(buf + len, n - len, fmt, args);
  62         if (len >= n)
  63                 goto bad;
  64         return cleanup_path(buf);
  65 bad:
  66         strlcpy(buf, bad_path, n);
  67         return buf;
  68 }
  69
  70 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  71 {
  72         va_list args;
  73         va_start(args, fmt);
  74         (void)git_vsnpath(buf, n, fmt, args);
  75         va_end(args);
  76         return buf;
  77 }
  78
  79 char *git_pathdup(const char *fmt, ...)
  80 {
  81         char path[PATH_MAX];
  82         va_list args;
  83         va_start(args, fmt);
  84         (void)git_vsnpath(path, sizeof(path), fmt, args);
  85         va_end(args);
  86         return xstrdup(path);
  87 }
  88
  89 char *mkpath(const char *fmt, ...)
  90 {
  91         va_list args;
  92         unsigned len;
  93         char *pathname = get_pathname();
  94
  95         va_start(args, fmt);
  96         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  97         va_end(args);
  98         if (len >= PATH_MAX)
  99                 return bad_path;
 100         return cleanup_path(pathname);
 101 }
 102
 103 char *git_path(const char *fmt, ...)
 104 {
 105         const char *git_dir = get_git_dir();
 106         char *pathname = get_pathname();
 107         va_list args;
 108         unsigned len;
 109
 110         len = strlen(git_dir);
 111         if (len > PATH_MAX-100)
 112                 return bad_path;
 113         memcpy(pathname, git_dir, len);
 114         if (len && git_dir[len-1] != '/')
 115                 pathname[len++] = '/';
 116         va_start(args, fmt);
 117         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 118         va_end(args);
 119         if (len >= PATH_MAX)
 120                 return bad_path;
 121         return cleanup_path(pathname);
 122 }
 123
 124
 125 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
 126 int git_mkstemp(char *path, size_t len, const char *template)
 127 {
 128         const char *tmp;
 129         size_t n;
 130
 131         tmp = getenv("TMPDIR");
 132         if (!tmp)
 133                 tmp = "/tmp";
 134         n = snprintf(path, len, "%s/%s", tmp, template);
 135         if (len <= n) {
 136                 errno = ENAMETOOLONG;
 137                 return -1;
 138         }
 139         return mkstemp(path);
 140 }
 141
 142 /* git_mkstemps() - create tmp file with suffix honoring TMPDIR variable. */
 143 int git_mkstemps(char *path, size_t len, const char *template, int suffix_len)
 144 {
 145         const char *tmp;
 146         size_t n;
 147
 148         tmp = getenv("TMPDIR");
 149         if (!tmp)
 150                 tmp = "/tmp";
 151         n = snprintf(path, len, "%s/%s", tmp, template);
 152         if (len <= n) {
 153                 errno = ENAMETOOLONG;
 154                 return -1;
 155         }
 156         return mkstemps(path, suffix_len);
 157 }
 158
 159 int validate_headref(const char *path)
 160 {
 161         struct stat st;
 162         char *buf, buffer[256];
 163         unsigned char sha1[20];
 164         int fd;
 165         ssize_t len;
 166
 167         if (lstat(path, &st) < 0)
 168                 return -1;
 169
 170         /* Make sure it is a "refs/.." symlink */
 171         if (S_ISLNK(st.st_mode)) {
 172                 len = readlink(path, buffer, sizeof(buffer)-1);
 173                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 174                         return 0;
 175                 return -1;
 176         }
 177
 178         /*
 179          * Anything else, just open it and try to see if it is a symbolic ref.
 180          */
 181         fd = open(path, O_RDONLY);
 182         if (fd < 0)
 183                 return -1;
 184         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 185         close(fd);
 186
 187         /*
 188          * Is it a symbolic ref?
 189          */
 190         if (len < 4)
 191                 return -1;
 192         if (!memcmp("ref:", buffer, 4)) {
 193                 buf = buffer + 4;
 194                 len -= 4;
 195                 while (len && isspace(*buf))
 196                         buf++, len--;
 197                 if (len >= 5 && !memcmp("refs/", buf, 5))
 198                         return 0;
 199         }
 200
 201         /*
 202          * Is this a detached HEAD?
 203          */
 204         if (!get_sha1_hex(buffer, sha1))
 205                 return 0;
 206
 207         return -1;
 208 }
 209
 210 static char *user_path(char *buf, char *path, int sz)
 211 {
 212         struct passwd *pw;
 213         char *slash;
 214         int len, baselen;
 215
 216         if (!path || path[0] != '~')
 217                 return NULL;
 218         path++;
 219         slash = strchr(path, '/');
 220         if (path[0] == '/' || !path[0]) {
 221                 pw = getpwuid(getuid());
 222         }
 223         else {
 224                 if (slash) {
 225                         *slash = 0;
 226                         pw = getpwnam(path);
 227                         *slash = '/';
 228                 }
 229                 else
 230                         pw = getpwnam(path);
 231         }
 232         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 233                 return NULL;
 234         baselen = strlen(pw->pw_dir);
 235         memcpy(buf, pw->pw_dir, baselen);
 236         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 237                 buf[baselen-1] = 0;
 238                 baselen--;
 239         }
 240         if (slash && slash[1]) {
 241                 len = strlen(slash);
 242                 if (sz <= baselen + len)
 243                         return NULL;
 244                 memcpy(buf + baselen, slash, len + 1);
 245         }
 246         return buf;
 247 }
 248
 249 /*
 250  * First, one directory to try is determined by the following algorithm.
 251  *
 252  * (0) If "strict" is given, the path is used as given and no DWIM is
 253  *     done. Otherwise:
 254  * (1) "~/path" to mean path under the running user's home directory;
 255  * (2) "~user/path" to mean path under named user's home directory;
 256  * (3) "relative/path" to mean cwd relative directory; or
 257  * (4) "/absolute/path" to mean absolute directory.
 258  *
 259  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 260  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 261  * what we try.
 262  *
 263  * Second, we try chdir() to that.  Upon failure, we return NULL.
 264  *
 265  * Then, we try if the current directory is a valid git repository.
 266  * Upon failure, we return NULL.
 267  *
 268  * If all goes well, we return the directory we used to chdir() (but
 269  * before ~user is expanded), avoiding getcwd() resolving symbolic
 270  * links.  User relative paths are also returned as they are given,
 271  * except DWIM suffixing.
 272  */
 273 char *enter_repo(char *path, int strict)
 274 {
 275         static char used_path[PATH_MAX];
 276         static char validated_path[PATH_MAX];
 277
 278         if (!path)
 279                 return NULL;
 280
 281         if (!strict) {
 282                 static const char *suffix[] = {
 283                         ".git/.git", "/.git", ".git", "", NULL,
 284                 };
 285                 int len = strlen(path);
 286                 int i;
 287                 while ((1 < len) && (path[len-1] == '/')) {
 288                         path[len-1] = 0;
 289                         len--;
 290                 }
 291                 if (PATH_MAX <= len)
 292                         return NULL;
 293                 if (path[0] == '~') {
 294                         if (!user_path(used_path, path, PATH_MAX))
 295                                 return NULL;
 296                         strcpy(validated_path, path);
 297                         path = used_path;
 298                 }
 299                 else if (PATH_MAX - 10 < len)
 300                         return NULL;
 301                 else {
 302                         path = strcpy(used_path, path);
 303                         strcpy(validated_path, path);
 304                 }
 305                 len = strlen(path);
 306                 for (i = 0; suffix[i]; i++) {
 307                         strcpy(path + len, suffix[i]);
 308                         if (!access(path, F_OK)) {
 309                                 strcat(validated_path, suffix[i]);
 310                                 break;
 311                         }
 312                 }
 313                 if (!suffix[i] || chdir(path))
 314                         return NULL;
 315                 path = validated_path;
 316         }
 317         else if (chdir(path))
 318                 return NULL;
 319
 320         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 321             validate_headref("HEAD") == 0) {
 322                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 323                 check_repository_format();
 324                 return path;
 325         }
 326
 327         return NULL;
 328 }
 329
 330 int set_shared_perm(const char *path, int mode)
 331 {
 332         struct stat st;
 333         int tweak, shared, orig_mode;
 334
 335         if (!shared_repository) {
 336                 if (mode)
 337                         return chmod(path, mode & ~S_IFMT);
 338                 return 0;
 339         }
 340         if (!mode) {
 341                 if (lstat(path, &st) < 0)
 342                         return -1;
 343                 mode = st.st_mode;
 344                 orig_mode = mode;
 345         } else
 346                 orig_mode = 0;
 347         if (shared_repository < 0)
 348                 shared = -shared_repository;
 349         else
 350                 shared = shared_repository;
 351         tweak = shared;
 352
 353         if (!(mode & S_IWUSR))
 354                 tweak &= ~0222;
 355         if (mode & S_IXUSR)
 356                 /* Copy read bits to execute bits */
 357                 tweak |= (tweak & 0444) >> 2;
 358         if (shared_repository < 0)
 359                 mode = (mode & ~0777) | tweak;
 360         else
 361                 mode |= tweak;
 362
 363         if (S_ISDIR(mode)) {
 364                 /* Copy read bits to execute bits */
 365                 mode |= (shared & 0444) >> 2;
 366                 mode |= FORCE_DIR_SET_GID;
 367         }
 368
 369         if (((shared_repository < 0
 370               ? (orig_mode & (FORCE_DIR_SET_GID | 0777))
 371               : (orig_mode & mode)) != mode) &&
 372             chmod(path, (mode & ~S_IFMT)) < 0)
 373                 return -2;
 374         return 0;
 375 }
 376
 377 const char *make_relative_path(const char *abs, const char *base)
 378 {
 379         static char buf[PATH_MAX + 1];
 380         int baselen;
 381         if (!base)
 382                 return abs;
 383         baselen = strlen(base);
 384         if (prefixcmp(abs, base))
 385                 return abs;
 386         if (abs[baselen] == '/')
 387                 baselen++;
 388         else if (base[baselen - 1] != '/')
 389                 return abs;
 390         strcpy(buf, abs + baselen);
 391         return buf;
 392 }
 393
 394 /*
 395  * It is okay if dst == src, but they should not overlap otherwise.
 396  *
 397  * Performs the following normalizations on src, storing the result in dst:
 398  * - Ensures that components are separated by '/' (Windows only)
 399  * - Squashes sequences of '/'.
 400  * - Removes "." components.
 401  * - Removes ".." components, and the components the precede them.
 402  * Returns failure (non-zero) if a ".." component appears as first path
 403  * component anytime during the normalization. Otherwise, returns success (0).
 404  *
 405  * Note that this function is purely textual.  It does not follow symlinks,
 406  * verify the existence of the path, or make any system calls.
 407  */
 408 int normalize_path_copy(char *dst, const char *src)
 409 {
 410         char *dst0;
 411
 412         if (has_dos_drive_prefix(src)) {
 413                 *dst++ = *src++;
 414                 *dst++ = *src++;
 415         }
 416         dst0 = dst;
 417
 418         if (is_dir_sep(*src)) {
 419                 *dst++ = '/';
 420                 while (is_dir_sep(*src))
 421                         src++;
 422         }
 423
 424         for (;;) {
 425                 char c = *src;
 426
 427                 /*
 428                  * A path component that begins with . could be
 429                  * special:
 430                  * (1) "." and ends   -- ignore and terminate.
 431                  * (2) "./"           -- ignore them, eat slash and continue.
 432                  * (3) ".." and ends  -- strip one and terminate.
 433                  * (4) "../"          -- strip one, eat slash and continue.
 434                  */
 435                 if (c == '.') {
 436                         if (!src[1]) {
 437                                 /* (1) */
 438                                 src++;
 439                         } else if (is_dir_sep(src[1])) {
 440                                 /* (2) */
 441                                 src += 2;
 442                                 while (is_dir_sep(*src))
 443                                         src++;
 444                                 continue;
 445                         } else if (src[1] == '.') {
 446                                 if (!src[2]) {
 447                                         /* (3) */
 448                                         src += 2;
 449                                         goto up_one;
 450                                 } else if (is_dir_sep(src[2])) {
 451                                         /* (4) */
 452                                         src += 3;
 453                                         while (is_dir_sep(*src))
 454                                                 src++;
 455                                         goto up_one;
 456                                 }
 457                         }
 458                 }
 459
 460                 /* copy up to the next '/', and eat all '/' */
 461                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 462                         *dst++ = c;
 463                 if (is_dir_sep(c)) {
 464                         *dst++ = '/';
 465                         while (is_dir_sep(c))
 466                                 c = *src++;
 467                         src--;
 468                 } else if (!c)
 469                         break;
 470                 continue;
 471
 472         up_one:
 473                 /*
 474                  * dst0..dst is prefix portion, and dst[-1] is '/';
 475                  * go up one level.
 476                  */
 477                 dst--;  /* go to trailing '/' */
 478                 if (dst <= dst0)
 479                         return -1;
 480                 /* Windows: dst[-1] cannot be backslash anymore */
 481                 while (dst0 < dst && dst[-1] != '/')
 482                         dst--;
 483         }
 484         *dst = '\0';
 485         return 0;
 486 }
 487
 488 /*
 489  * path = Canonical absolute path
 490  * prefix_list = Colon-separated list of absolute paths
 491  *
 492  * Determines, for each path in prefix_list, whether the "prefix" really
 493  * is an ancestor directory of path.  Returns the length of the longest
 494  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 495  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 496  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 497  * are not considered to be their own ancestors.  path must be in a
 498  * canonical form: empty components, or "." or ".." components are not
 499  * allowed.  prefix_list may be null, which is like "".
 500  */
 501 int longest_ancestor_length(const char *path, const char *prefix_list)
 502 {
 503         char buf[PATH_MAX+1];
 504         const char *ceil, *colon;
 505         int len, max_len = -1;
 506
 507         if (prefix_list == NULL || !strcmp(path, "/"))
 508                 return -1;
 509
 510         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 511                 for (colon = ceil; *colon && *colon != PATH_SEP; colon++);
 512                 len = colon - ceil;
 513                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 514                         continue;
 515                 strlcpy(buf, ceil, len+1);
 516                 if (normalize_path_copy(buf, buf) < 0)
 517                         continue;
 518                 len = strlen(buf);
 519                 if (len > 0 && buf[len-1] == '/')
 520                         buf[--len] = '\0';
 521
 522                 if (!strncmp(path, buf, len) &&
 523                     path[len] == '/' &&
 524                     len > max_len) {
 525                         max_len = len;
 526                 }
 527         }
 528
 529         return max_len;
 530 }
 531
 532 /* strip arbitrary amount of directory separators at end of path */
 533 static inline int chomp_trailing_dir_sep(const char *path, int len)
 534 {
 535         while (len && is_dir_sep(path[len - 1]))
 536                 len--;
 537         return len;
 538 }
 539
 540 /*
 541  * If path ends with suffix (complete path components), returns the
 542  * part before suffix (sans trailing directory separators).
 543  * Otherwise returns NULL.
 544  */
 545 char *strip_path_suffix(const char *path, const char *suffix)
 546 {
 547         int path_len = strlen(path), suffix_len = strlen(suffix);
 548
 549         while (suffix_len) {
 550                 if (!path_len)
 551                         return NULL;
 552
 553                 if (is_dir_sep(path[path_len - 1])) {
 554                         if (!is_dir_sep(suffix[suffix_len - 1]))
 555                                 return NULL;
 556                         path_len = chomp_trailing_dir_sep(path, path_len);
 557                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 558                 }
 559                 else if (path[--path_len] != suffix[--suffix_len])
 560                         return NULL;
 561         }
 562
 563         if (path_len && !is_dir_sep(path[path_len - 1]))
 564                 return NULL;
 565         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 566 }