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 #include "strbuf.h"
  15
  16 static char bad_path[] = "/bad-path/";
  17
  18 static char *get_pathname(void)
  19 {
  20         static char pathname_array[4][PATH_MAX];
  21         static int index;
  22         return pathname_array[3 & ++index];
  23 }
  24
  25 static char *cleanup_path(char *path)
  26 {
  27         /* Clean it up */
  28         if (!memcmp(path, "./", 2)) {
  29                 path += 2;
  30                 while (*path == '/')
  31                         path++;
  32         }
  33         return path;
  34 }
  35
  36 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  37 {
  38         va_list args;
  39         unsigned len;
  40
  41         va_start(args, fmt);
  42         len = vsnprintf(buf, n, fmt, args);
  43         va_end(args);
  44         if (len >= n) {
  45                 strlcpy(buf, bad_path, n);
  46                 return buf;
  47         }
  48         return cleanup_path(buf);
  49 }
  50
  51 static char *git_vsnpath(char *buf, size_t n, const char *fmt, va_list args)
  52 {
  53         const char *git_dir = get_git_dir();
  54         size_t len;
  55
  56         len = strlen(git_dir);
  57         if (n < len + 1)
  58                 goto bad;
  59         memcpy(buf, git_dir, len);
  60         if (len && !is_dir_sep(git_dir[len-1]))
  61                 buf[len++] = '/';
  62         len += vsnprintf(buf + len, n - len, fmt, args);
  63         if (len >= n)
  64                 goto bad;
  65         return cleanup_path(buf);
  66 bad:
  67         strlcpy(buf, bad_path, n);
  68         return buf;
  69 }
  70
  71 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  72 {
  73         va_list args;
  74         va_start(args, fmt);
  75         (void)git_vsnpath(buf, n, fmt, args);
  76         va_end(args);
  77         return buf;
  78 }
  79
  80 char *git_pathdup(const char *fmt, ...)
  81 {
  82         char path[PATH_MAX];
  83         va_list args;
  84         va_start(args, fmt);
  85         (void)git_vsnpath(path, sizeof(path), fmt, args);
  86         va_end(args);
  87         return xstrdup(path);
  88 }
  89
  90 char *mkpath(const char *fmt, ...)
  91 {
  92         va_list args;
  93         unsigned len;
  94         char *pathname = get_pathname();
  95
  96         va_start(args, fmt);
  97         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  98         va_end(args);
  99         if (len >= PATH_MAX)
 100                 return bad_path;
 101         return cleanup_path(pathname);
 102 }
 103
 104 char *git_path(const char *fmt, ...)
 105 {
 106         const char *git_dir = get_git_dir();
 107         char *pathname = get_pathname();
 108         va_list args;
 109         unsigned len;
 110
 111         len = strlen(git_dir);
 112         if (len > PATH_MAX-100)
 113                 return bad_path;
 114         memcpy(pathname, git_dir, len);
 115         if (len && git_dir[len-1] != '/')
 116                 pathname[len++] = '/';
 117         va_start(args, fmt);
 118         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 119         va_end(args);
 120         if (len >= PATH_MAX)
 121                 return bad_path;
 122         return cleanup_path(pathname);
 123 }
 124
 125 char *git_path_submodule(const char *path, const char *fmt, ...)
 126 {
 127         char *pathname = get_pathname();
 128         struct strbuf buf = STRBUF_INIT;
 129         const char *git_dir;
 130         va_list args;
 131         unsigned len;
 132
 133         len = strlen(path);
 134         if (len > PATH_MAX-100)
 135                 return bad_path;
 136
 137         strbuf_addstr(&buf, path);
 138         if (len && path[len-1] != '/')
 139                 strbuf_addch(&buf, '/');
 140         strbuf_addstr(&buf, ".git");
 141
 142         git_dir = read_gitfile(buf.buf);
 143         if (git_dir) {
 144                 strbuf_reset(&buf);
 145                 strbuf_addstr(&buf, git_dir);
 146         }
 147         strbuf_addch(&buf, '/');
 148
 149         if (buf.len >= PATH_MAX)
 150                 return bad_path;
 151         memcpy(pathname, buf.buf, buf.len + 1);
 152
 153         strbuf_release(&buf);
 154         len = strlen(pathname);
 155
 156         va_start(args, fmt);
 157         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 158         va_end(args);
 159         if (len >= PATH_MAX)
 160                 return bad_path;
 161         return cleanup_path(pathname);
 162 }
 163
 164 int validate_headref(const char *path)
 165 {
 166         struct stat st;
 167         char *buf, buffer[256];
 168         unsigned char sha1[20];
 169         int fd;
 170         ssize_t len;
 171
 172         if (lstat(path, &st) < 0)
 173                 return -1;
 174
 175         /* Make sure it is a "refs/.." symlink */
 176         if (S_ISLNK(st.st_mode)) {
 177                 len = readlink(path, buffer, sizeof(buffer)-1);
 178                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 179                         return 0;
 180                 return -1;
 181         }
 182
 183         /*
 184          * Anything else, just open it and try to see if it is a symbolic ref.
 185          */
 186         fd = open(path, O_RDONLY);
 187         if (fd < 0)
 188                 return -1;
 189         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 190         close(fd);
 191
 192         /*
 193          * Is it a symbolic ref?
 194          */
 195         if (len < 4)
 196                 return -1;
 197         if (!memcmp("ref:", buffer, 4)) {
 198                 buf = buffer + 4;
 199                 len -= 4;
 200                 while (len && isspace(*buf))
 201                         buf++, len--;
 202                 if (len >= 5 && !memcmp("refs/", buf, 5))
 203                         return 0;
 204         }
 205
 206         /*
 207          * Is this a detached HEAD?
 208          */
 209         if (!get_sha1_hex(buffer, sha1))
 210                 return 0;
 211
 212         return -1;
 213 }
 214
 215 static struct passwd *getpw_str(const char *username, size_t len)
 216 {
 217         struct passwd *pw;
 218         char *username_z = xmalloc(len + 1);
 219         memcpy(username_z, username, len);
 220         username_z[len] = '\0';
 221         pw = getpwnam(username_z);
 222         free(username_z);
 223         return pw;
 224 }
 225
 226 /*
 227  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 228  * then it is a newly allocated string. Returns NULL on getpw failure or
 229  * if path is NULL.
 230  */
 231 char *expand_user_path(const char *path)
 232 {
 233         struct strbuf user_path = STRBUF_INIT;
 234         const char *first_slash = strchrnul(path, '/');
 235         const char *to_copy = path;
 236
 237         if (path == NULL)
 238                 goto return_null;
 239         if (path[0] == '~') {
 240                 const char *username = path + 1;
 241                 size_t username_len = first_slash - username;
 242                 if (username_len == 0) {
 243                         const char *home = get_home_directory();
 244                         if (!home)
 245                                 goto return_null;
 246                         strbuf_add(&user_path, home, strlen(home));
 247                 } else {
 248                         struct passwd *pw = getpw_str(username, username_len);
 249                         if (!pw)
 250                                 goto return_null;
 251                         strbuf_add(&user_path, pw->pw_dir, strlen(pw->pw_dir));
 252                 }
 253                 to_copy = first_slash;
 254         }
 255         strbuf_add(&user_path, to_copy, strlen(to_copy));
 256         return strbuf_detach(&user_path, NULL);
 257 return_null:
 258         strbuf_release(&user_path);
 259         return NULL;
 260 }
 261
 262 /*
 263  * First, one directory to try is determined by the following algorithm.
 264  *
 265  * (0) If "strict" is given, the path is used as given and no DWIM is
 266  *     done. Otherwise:
 267  * (1) "~/path" to mean path under the running user's home directory;
 268  * (2) "~user/path" to mean path under named user's home directory;
 269  * (3) "relative/path" to mean cwd relative directory; or
 270  * (4) "/absolute/path" to mean absolute directory.
 271  *
 272  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 273  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 274  * what we try.
 275  *
 276  * Second, we try chdir() to that.  Upon failure, we return NULL.
 277  *
 278  * Then, we try if the current directory is a valid git repository.
 279  * Upon failure, we return NULL.
 280  *
 281  * If all goes well, we return the directory we used to chdir() (but
 282  * before ~user is expanded), avoiding getcwd() resolving symbolic
 283  * links.  User relative paths are also returned as they are given,
 284  * except DWIM suffixing.
 285  */
 286 const char *enter_repo(const char *path, int strict)
 287 {
 288         static char used_path[PATH_MAX];
 289         static char validated_path[PATH_MAX];
 290
 291         if (!path)
 292                 return NULL;
 293
 294         if (!strict) {
 295                 static const char *suffix[] = {
 296                         ".git/.git", "/.git", ".git", "", NULL,
 297                 };
 298                 const char *gitfile;
 299                 int len = strlen(path);
 300                 int i;
 301                 while ((1 < len) && (path[len-1] == '/'))
 302                         len--;
 303
 304                 if (PATH_MAX <= len)
 305                         return NULL;
 306                 strncpy(used_path, path, len); used_path[len] = 0 ;
 307                 strcpy(validated_path, used_path);
 308
 309                 if (used_path[0] == '~') {
 310                         char *newpath = expand_user_path(used_path);
 311                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 312                                 free(newpath);
 313                                 return NULL;
 314                         }
 315                         /*
 316                          * Copy back into the static buffer. A pity
 317                          * since newpath was not bounded, but other
 318                          * branches of the if are limited by PATH_MAX
 319                          * anyway.
 320                          */
 321                         strcpy(used_path, newpath); free(newpath);
 322                 }
 323                 else if (PATH_MAX - 10 < len)
 324                         return NULL;
 325                 len = strlen(used_path);
 326                 for (i = 0; suffix[i]; i++) {
 327                         strcpy(used_path + len, suffix[i]);
 328                         if (!access(used_path, F_OK)) {
 329                                 strcat(validated_path, suffix[i]);
 330                                 break;
 331                         }
 332                 }
 333                 if (!suffix[i])
 334                         return NULL;
 335                 gitfile = read_gitfile(used_path) ;
 336                 if (gitfile)
 337                         strcpy(used_path, gitfile);
 338                 if (chdir(used_path))
 339                         return NULL;
 340                 path = validated_path;
 341         }
 342         else if (chdir(path))
 343                 return NULL;
 344
 345         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 346             validate_headref("HEAD") == 0) {
 347                 set_git_dir(".");
 348                 check_repository_format();
 349                 return path;
 350         }
 351
 352         return NULL;
 353 }
 354
 355 int set_shared_perm(const char *path, int mode)
 356 {
 357         struct stat st;
 358         int tweak, shared, orig_mode;
 359
 360         if (!shared_repository) {
 361                 if (mode)
 362                         return chmod(path, mode & ~S_IFMT);
 363                 return 0;
 364         }
 365         if (!mode) {
 366                 if (lstat(path, &st) < 0)
 367                         return -1;
 368                 mode = st.st_mode;
 369                 orig_mode = mode;
 370         } else
 371                 orig_mode = 0;
 372         if (shared_repository < 0)
 373                 shared = -shared_repository;
 374         else
 375                 shared = shared_repository;
 376         tweak = shared;
 377
 378         if (!(mode & S_IWUSR))
 379                 tweak &= ~0222;
 380         if (mode & S_IXUSR)
 381                 /* Copy read bits to execute bits */
 382                 tweak |= (tweak & 0444) >> 2;
 383         if (shared_repository < 0)
 384                 mode = (mode & ~0777) | tweak;
 385         else
 386                 mode |= tweak;
 387
 388         if (S_ISDIR(mode)) {
 389                 /* Copy read bits to execute bits */
 390                 mode |= (shared & 0444) >> 2;
 391                 mode |= FORCE_DIR_SET_GID;
 392         }
 393
 394         if (((shared_repository < 0
 395               ? (orig_mode & (FORCE_DIR_SET_GID | 0777))
 396               : (orig_mode & mode)) != mode) &&
 397             chmod(path, (mode & ~S_IFMT)) < 0)
 398                 return -2;
 399         return 0;
 400 }
 401
 402 const char *relative_path(const char *abs, const char *base)
 403 {
 404         static char buf[PATH_MAX + 1];
 405         int i = 0, j = 0;
 406
 407         if (!base || !base[0])
 408                 return abs;
 409         while (base[i]) {
 410                 if (is_dir_sep(base[i])) {
 411                         if (!is_dir_sep(abs[j]))
 412                                 return abs;
 413                         while (is_dir_sep(base[i]))
 414                                 i++;
 415                         while (is_dir_sep(abs[j]))
 416                                 j++;
 417                         continue;
 418                 } else if (abs[j] != base[i]) {
 419                         return abs;
 420                 }
 421                 i++;
 422                 j++;
 423         }
 424         if (
 425             /* "/foo" is a prefix of "/foo" */
 426             abs[j] &&
 427             /* "/foo" is not a prefix of "/foobar" */
 428             !is_dir_sep(base[i-1]) && !is_dir_sep(abs[j])
 429            )
 430                 return abs;
 431         while (is_dir_sep(abs[j]))
 432                 j++;
 433         if (!abs[j])
 434                 strcpy(buf, ".");
 435         else
 436                 strcpy(buf, abs + j);
 437         return buf;
 438 }
 439
 440 /*
 441  * It is okay if dst == src, but they should not overlap otherwise.
 442  *
 443  * Performs the following normalizations on src, storing the result in dst:
 444  * - Ensures that components are separated by '/' (Windows only)
 445  * - Squashes sequences of '/'.
 446  * - Removes "." components.
 447  * - Removes ".." components, and the components the precede them.
 448  * Returns failure (non-zero) if a ".." component appears as first path
 449  * component anytime during the normalization. Otherwise, returns success (0).
 450  *
 451  * Note that this function is purely textual.  It does not follow symlinks,
 452  * verify the existence of the path, or make any system calls.
 453  */
 454 int normalize_path_copy(char *dst, const char *src)
 455 {
 456         char *dst0;
 457
 458         if (has_dos_drive_prefix(src)) {
 459                 *dst++ = *src++;
 460                 *dst++ = *src++;
 461         }
 462         dst0 = dst;
 463
 464         if (is_dir_sep(*src)) {
 465                 *dst++ = '/';
 466                 while (is_dir_sep(*src))
 467                         src++;
 468         }
 469
 470         for (;;) {
 471                 char c = *src;
 472
 473                 /*
 474                  * A path component that begins with . could be
 475                  * special:
 476                  * (1) "." and ends   -- ignore and terminate.
 477                  * (2) "./"           -- ignore them, eat slash and continue.
 478                  * (3) ".." and ends  -- strip one and terminate.
 479                  * (4) "../"          -- strip one, eat slash and continue.
 480                  */
 481                 if (c == '.') {
 482                         if (!src[1]) {
 483                                 /* (1) */
 484                                 src++;
 485                         } else if (is_dir_sep(src[1])) {
 486                                 /* (2) */
 487                                 src += 2;
 488                                 while (is_dir_sep(*src))
 489                                         src++;
 490                                 continue;
 491                         } else if (src[1] == '.') {
 492                                 if (!src[2]) {
 493                                         /* (3) */
 494                                         src += 2;
 495                                         goto up_one;
 496                                 } else if (is_dir_sep(src[2])) {
 497                                         /* (4) */
 498                                         src += 3;
 499                                         while (is_dir_sep(*src))
 500                                                 src++;
 501                                         goto up_one;
 502                                 }
 503                         }
 504                 }
 505
 506                 /* copy up to the next '/', and eat all '/' */
 507                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 508                         *dst++ = c;
 509                 if (is_dir_sep(c)) {
 510                         *dst++ = '/';
 511                         while (is_dir_sep(c))
 512                                 c = *src++;
 513                         src--;
 514                 } else if (!c)
 515                         break;
 516                 continue;
 517
 518         up_one:
 519                 /*
 520                  * dst0..dst is prefix portion, and dst[-1] is '/';
 521                  * go up one level.
 522                  */
 523                 dst--;  /* go to trailing '/' */
 524                 if (dst <= dst0)
 525                         return -1;
 526                 /* Windows: dst[-1] cannot be backslash anymore */
 527                 while (dst0 < dst && dst[-1] != '/')
 528                         dst--;
 529         }
 530         *dst = '\0';
 531         return 0;
 532 }
 533
 534 /*
 535  * path = Canonical absolute path
 536  * prefix_list = Colon-separated list of absolute paths
 537  *
 538  * Determines, for each path in prefix_list, whether the "prefix" really
 539  * is an ancestor directory of path.  Returns the length of the longest
 540  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 541  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 542  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 543  * are not considered to be their own ancestors.  path must be in a
 544  * canonical form: empty components, or "." or ".." components are not
 545  * allowed.  prefix_list may be null, which is like "".
 546  */
 547 int longest_ancestor_length(const char *path, const char *prefix_list)
 548 {
 549         char buf[PATH_MAX+1];
 550         const char *ceil, *colon;
 551         int len, max_len = -1;
 552
 553         if (prefix_list == NULL || !strcmp(path, "/"))
 554                 return -1;
 555
 556         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 557                 for (colon = ceil; *colon && *colon != PATH_SEP; colon++);
 558                 len = colon - ceil;
 559                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 560                         continue;
 561                 strlcpy(buf, ceil, len+1);
 562                 if (normalize_path_copy(buf, buf) < 0)
 563                         continue;
 564                 len = strlen(buf);
 565                 if (len > 0 && buf[len-1] == '/')
 566                         buf[--len] = '\0';
 567
 568                 if (!strncmp(path, buf, len) &&
 569                     path[len] == '/' &&
 570                     len > max_len) {
 571                         max_len = len;
 572                 }
 573         }
 574
 575         return max_len;
 576 }
 577
 578 /* strip arbitrary amount of directory separators at end of path */
 579 static inline int chomp_trailing_dir_sep(const char *path, int len)
 580 {
 581         while (len && is_dir_sep(path[len - 1]))
 582                 len--;
 583         return len;
 584 }
 585
 586 /*
 587  * If path ends with suffix (complete path components), returns the
 588  * part before suffix (sans trailing directory separators).
 589  * Otherwise returns NULL.
 590  */
 591 char *strip_path_suffix(const char *path, const char *suffix)
 592 {
 593         int path_len = strlen(path), suffix_len = strlen(suffix);
 594
 595         while (suffix_len) {
 596                 if (!path_len)
 597                         return NULL;
 598
 599                 if (is_dir_sep(path[path_len - 1])) {
 600                         if (!is_dir_sep(suffix[suffix_len - 1]))
 601                                 return NULL;
 602                         path_len = chomp_trailing_dir_sep(path, path_len);
 603                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 604                 }
 605                 else if (path[--path_len] != suffix[--suffix_len])
 606                         return NULL;
 607         }
 608
 609         if (path_len && !is_dir_sep(path[path_len - 1]))
 610                 return NULL;
 611         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 612 }
 613
 614 int daemon_avoid_alias(const char *p)
 615 {
 616         int sl, ndot;
 617
 618         /*
 619          * This resurrects the belts and suspenders paranoia check by HPA
 620          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 621          * does not do getcwd() based path canonicalization.
 622          *
 623          * sl becomes true immediately after seeing '/' and continues to
 624          * be true as long as dots continue after that without intervening
 625          * non-dot character.
 626          */
 627         if (!p || (*p != '/' && *p != '~'))
 628                 return -1;
 629         sl = 1; ndot = 0;
 630         p++;
 631
 632         while (1) {
 633                 char ch = *p++;
 634                 if (sl) {
 635                         if (ch == '.')
 636                                 ndot++;
 637                         else if (ch == '/') {
 638                                 if (ndot < 3)
 639                                         /* reject //, /./ and /../ */
 640                                         return -1;
 641                                 ndot = 0;
 642                         }
 643                         else if (ch == 0) {
 644                                 if (0 < ndot && ndot < 3)
 645                                         /* reject /.$ and /..$ */
 646                                         return -1;
 647                                 return 0;
 648                         }
 649                         else
 650                                 sl = ndot = 0;
 651                 }
 652                 else if (ch == 0)
 653                         return 0;
 654                 else if (ch == '/') {
 655                         sl = 1;
 656                         ndot = 0;
 657                 }
 658         }
 659 }