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 *mkpathdup(const char *fmt, ...)
  91 {
  92         char *path;
  93         struct strbuf sb = STRBUF_INIT;
  94         va_list args;
  95
  96         va_start(args, fmt);
  97         strbuf_vaddf(&sb, fmt, args);
  98         va_end(args);
  99         path = xstrdup(cleanup_path(sb.buf));
 100
 101         strbuf_release(&sb);
 102         return path;
 103 }
 104
 105 char *mkpath(const char *fmt, ...)
 106 {
 107         va_list args;
 108         unsigned len;
 109         char *pathname = get_pathname();
 110
 111         va_start(args, fmt);
 112         len = vsnprintf(pathname, PATH_MAX, fmt, args);
 113         va_end(args);
 114         if (len >= PATH_MAX)
 115                 return bad_path;
 116         return cleanup_path(pathname);
 117 }
 118
 119 char *git_path(const char *fmt, ...)
 120 {
 121         const char *git_dir = get_git_dir();
 122         char *pathname = get_pathname();
 123         va_list args;
 124         unsigned len;
 125
 126         len = strlen(git_dir);
 127         if (len > PATH_MAX-100)
 128                 return bad_path;
 129         memcpy(pathname, git_dir, len);
 130         if (len && git_dir[len-1] != '/')
 131                 pathname[len++] = '/';
 132         va_start(args, fmt);
 133         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 134         va_end(args);
 135         if (len >= PATH_MAX)
 136                 return bad_path;
 137         return cleanup_path(pathname);
 138 }
 139
 140 void home_config_paths(char **global, char **xdg, char *file)
 141 {
 142         char *xdg_home = getenv("XDG_CONFIG_HOME");
 143         char *home = getenv("HOME");
 144         char *to_free = NULL;
 145
 146         if (!home) {
 147                 if (global)
 148                         *global = NULL;
 149         } else {
 150                 if (!xdg_home) {
 151                         to_free = mkpathdup("%s/.config", home);
 152                         xdg_home = to_free;
 153                 }
 154                 if (global)
 155                         *global = mkpathdup("%s/.gitconfig", home);
 156         }
 157
 158         if (!xdg_home)
 159                 *xdg = NULL;
 160         else
 161                 *xdg = mkpathdup("%s/git/%s", xdg_home, file);
 162
 163         free(to_free);
 164 }
 165
 166 char *git_path_submodule(const char *path, const char *fmt, ...)
 167 {
 168         char *pathname = get_pathname();
 169         struct strbuf buf = STRBUF_INIT;
 170         const char *git_dir;
 171         va_list args;
 172         unsigned len;
 173
 174         len = strlen(path);
 175         if (len > PATH_MAX-100)
 176                 return bad_path;
 177
 178         strbuf_addstr(&buf, path);
 179         if (len && path[len-1] != '/')
 180                 strbuf_addch(&buf, '/');
 181         strbuf_addstr(&buf, ".git");
 182
 183         git_dir = read_gitfile(buf.buf);
 184         if (git_dir) {
 185                 strbuf_reset(&buf);
 186                 strbuf_addstr(&buf, git_dir);
 187         }
 188         strbuf_addch(&buf, '/');
 189
 190         if (buf.len >= PATH_MAX)
 191                 return bad_path;
 192         memcpy(pathname, buf.buf, buf.len + 1);
 193
 194         strbuf_release(&buf);
 195         len = strlen(pathname);
 196
 197         va_start(args, fmt);
 198         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 199         va_end(args);
 200         if (len >= PATH_MAX)
 201                 return bad_path;
 202         return cleanup_path(pathname);
 203 }
 204
 205 int validate_headref(const char *path)
 206 {
 207         struct stat st;
 208         char *buf, buffer[256];
 209         unsigned char sha1[20];
 210         int fd;
 211         ssize_t len;
 212
 213         if (lstat(path, &st) < 0)
 214                 return -1;
 215
 216         /* Make sure it is a "refs/.." symlink */
 217         if (S_ISLNK(st.st_mode)) {
 218                 len = readlink(path, buffer, sizeof(buffer)-1);
 219                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 220                         return 0;
 221                 return -1;
 222         }
 223
 224         /*
 225          * Anything else, just open it and try to see if it is a symbolic ref.
 226          */
 227         fd = open(path, O_RDONLY);
 228         if (fd < 0)
 229                 return -1;
 230         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 231         close(fd);
 232
 233         /*
 234          * Is it a symbolic ref?
 235          */
 236         if (len < 4)
 237                 return -1;
 238         if (!memcmp("ref:", buffer, 4)) {
 239                 buf = buffer + 4;
 240                 len -= 4;
 241                 while (len && isspace(*buf))
 242                         buf++, len--;
 243                 if (len >= 5 && !memcmp("refs/", buf, 5))
 244                         return 0;
 245         }
 246
 247         /*
 248          * Is this a detached HEAD?
 249          */
 250         if (!get_sha1_hex(buffer, sha1))
 251                 return 0;
 252
 253         return -1;
 254 }
 255
 256 static struct passwd *getpw_str(const char *username, size_t len)
 257 {
 258         struct passwd *pw;
 259         char *username_z = xmalloc(len + 1);
 260         memcpy(username_z, username, len);
 261         username_z[len] = '\0';
 262         pw = getpwnam(username_z);
 263         free(username_z);
 264         return pw;
 265 }
 266
 267 /*
 268  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 269  * then it is a newly allocated string. Returns NULL on getpw failure or
 270  * if path is NULL.
 271  */
 272 char *expand_user_path(const char *path)
 273 {
 274         struct strbuf user_path = STRBUF_INIT;
 275         const char *first_slash = strchrnul(path, '/');
 276         const char *to_copy = path;
 277
 278         if (path == NULL)
 279                 goto return_null;
 280         if (path[0] == '~') {
 281                 const char *username = path + 1;
 282                 size_t username_len = first_slash - username;
 283                 if (username_len == 0) {
 284                         const char *home = getenv("HOME");
 285                         if (!home)
 286                                 goto return_null;
 287                         strbuf_add(&user_path, home, strlen(home));
 288                 } else {
 289                         struct passwd *pw = getpw_str(username, username_len);
 290                         if (!pw)
 291                                 goto return_null;
 292                         strbuf_add(&user_path, pw->pw_dir, strlen(pw->pw_dir));
 293                 }
 294                 to_copy = first_slash;
 295         }
 296         strbuf_add(&user_path, to_copy, strlen(to_copy));
 297         return strbuf_detach(&user_path, NULL);
 298 return_null:
 299         strbuf_release(&user_path);
 300         return NULL;
 301 }
 302
 303 /*
 304  * First, one directory to try is determined by the following algorithm.
 305  *
 306  * (0) If "strict" is given, the path is used as given and no DWIM is
 307  *     done. Otherwise:
 308  * (1) "~/path" to mean path under the running user's home directory;
 309  * (2) "~user/path" to mean path under named user's home directory;
 310  * (3) "relative/path" to mean cwd relative directory; or
 311  * (4) "/absolute/path" to mean absolute directory.
 312  *
 313  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 314  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 315  * what we try.
 316  *
 317  * Second, we try chdir() to that.  Upon failure, we return NULL.
 318  *
 319  * Then, we try if the current directory is a valid git repository.
 320  * Upon failure, we return NULL.
 321  *
 322  * If all goes well, we return the directory we used to chdir() (but
 323  * before ~user is expanded), avoiding getcwd() resolving symbolic
 324  * links.  User relative paths are also returned as they are given,
 325  * except DWIM suffixing.
 326  */
 327 const char *enter_repo(const char *path, int strict)
 328 {
 329         static char used_path[PATH_MAX];
 330         static char validated_path[PATH_MAX];
 331
 332         if (!path)
 333                 return NULL;
 334
 335         if (!strict) {
 336                 static const char *suffix[] = {
 337                         "/.git", "", ".git/.git", ".git", NULL,
 338                 };
 339                 const char *gitfile;
 340                 int len = strlen(path);
 341                 int i;
 342                 while ((1 < len) && (path[len-1] == '/'))
 343                         len--;
 344
 345                 if (PATH_MAX <= len)
 346                         return NULL;
 347                 strncpy(used_path, path, len); used_path[len] = 0 ;
 348                 strcpy(validated_path, used_path);
 349
 350                 if (used_path[0] == '~') {
 351                         char *newpath = expand_user_path(used_path);
 352                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 353                                 free(newpath);
 354                                 return NULL;
 355                         }
 356                         /*
 357                          * Copy back into the static buffer. A pity
 358                          * since newpath was not bounded, but other
 359                          * branches of the if are limited by PATH_MAX
 360                          * anyway.
 361                          */
 362                         strcpy(used_path, newpath); free(newpath);
 363                 }
 364                 else if (PATH_MAX - 10 < len)
 365                         return NULL;
 366                 len = strlen(used_path);
 367                 for (i = 0; suffix[i]; i++) {
 368                         struct stat st;
 369                         strcpy(used_path + len, suffix[i]);
 370                         if (!stat(used_path, &st) &&
 371                             (S_ISREG(st.st_mode) ||
 372                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 373                                 strcat(validated_path, suffix[i]);
 374                                 break;
 375                         }
 376                 }
 377                 if (!suffix[i])
 378                         return NULL;
 379                 gitfile = read_gitfile(used_path) ;
 380                 if (gitfile)
 381                         strcpy(used_path, gitfile);
 382                 if (chdir(used_path))
 383                         return NULL;
 384                 path = validated_path;
 385         }
 386         else if (chdir(path))
 387                 return NULL;
 388
 389         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 390             validate_headref("HEAD") == 0) {
 391                 set_git_dir(".");
 392                 check_repository_format();
 393                 return path;
 394         }
 395
 396         return NULL;
 397 }
 398
 399 int set_shared_perm(const char *path, int mode)
 400 {
 401         struct stat st;
 402         int tweak, shared, orig_mode;
 403
 404         if (!shared_repository) {
 405                 if (mode)
 406                         return chmod(path, mode & ~S_IFMT);
 407                 return 0;
 408         }
 409         if (!mode) {
 410                 if (lstat(path, &st) < 0)
 411                         return -1;
 412                 mode = st.st_mode;
 413                 orig_mode = mode;
 414         } else
 415                 orig_mode = 0;
 416         if (shared_repository < 0)
 417                 shared = -shared_repository;
 418         else
 419                 shared = shared_repository;
 420         tweak = shared;
 421
 422         if (!(mode & S_IWUSR))
 423                 tweak &= ~0222;
 424         if (mode & S_IXUSR)
 425                 /* Copy read bits to execute bits */
 426                 tweak |= (tweak & 0444) >> 2;
 427         if (shared_repository < 0)
 428                 mode = (mode & ~0777) | tweak;
 429         else
 430                 mode |= tweak;
 431
 432         if (S_ISDIR(mode)) {
 433                 /* Copy read bits to execute bits */
 434                 mode |= (shared & 0444) >> 2;
 435                 mode |= FORCE_DIR_SET_GID;
 436         }
 437
 438         if (((shared_repository < 0
 439               ? (orig_mode & (FORCE_DIR_SET_GID | 0777))
 440               : (orig_mode & mode)) != mode) &&
 441             chmod(path, (mode & ~S_IFMT)) < 0)
 442                 return -2;
 443         return 0;
 444 }
 445
 446 const char *relative_path(const char *abs, const char *base)
 447 {
 448         static char buf[PATH_MAX + 1];
 449         int i = 0, j = 0;
 450
 451         if (!base || !base[0])
 452                 return abs;
 453         while (base[i]) {
 454                 if (is_dir_sep(base[i])) {
 455                         if (!is_dir_sep(abs[j]))
 456                                 return abs;
 457                         while (is_dir_sep(base[i]))
 458                                 i++;
 459                         while (is_dir_sep(abs[j]))
 460                                 j++;
 461                         continue;
 462                 } else if (abs[j] != base[i]) {
 463                         return abs;
 464                 }
 465                 i++;
 466                 j++;
 467         }
 468         if (
 469             /* "/foo" is a prefix of "/foo" */
 470             abs[j] &&
 471             /* "/foo" is not a prefix of "/foobar" */
 472             !is_dir_sep(base[i-1]) && !is_dir_sep(abs[j])
 473            )
 474                 return abs;
 475         while (is_dir_sep(abs[j]))
 476                 j++;
 477         if (!abs[j])
 478                 strcpy(buf, ".");
 479         else
 480                 strcpy(buf, abs + j);
 481         return buf;
 482 }
 483
 484 /*
 485  * It is okay if dst == src, but they should not overlap otherwise.
 486  *
 487  * Performs the following normalizations on src, storing the result in dst:
 488  * - Ensures that components are separated by '/' (Windows only)
 489  * - Squashes sequences of '/'.
 490  * - Removes "." components.
 491  * - Removes ".." components, and the components the precede them.
 492  * Returns failure (non-zero) if a ".." component appears as first path
 493  * component anytime during the normalization. Otherwise, returns success (0).
 494  *
 495  * Note that this function is purely textual.  It does not follow symlinks,
 496  * verify the existence of the path, or make any system calls.
 497  */
 498 int normalize_path_copy(char *dst, const char *src)
 499 {
 500         char *dst0;
 501
 502         if (has_dos_drive_prefix(src)) {
 503                 *dst++ = *src++;
 504                 *dst++ = *src++;
 505         }
 506         dst0 = dst;
 507
 508         if (is_dir_sep(*src)) {
 509                 *dst++ = '/';
 510                 while (is_dir_sep(*src))
 511                         src++;
 512         }
 513
 514         for (;;) {
 515                 char c = *src;
 516
 517                 /*
 518                  * A path component that begins with . could be
 519                  * special:
 520                  * (1) "." and ends   -- ignore and terminate.
 521                  * (2) "./"           -- ignore them, eat slash and continue.
 522                  * (3) ".." and ends  -- strip one and terminate.
 523                  * (4) "../"          -- strip one, eat slash and continue.
 524                  */
 525                 if (c == '.') {
 526                         if (!src[1]) {
 527                                 /* (1) */
 528                                 src++;
 529                         } else if (is_dir_sep(src[1])) {
 530                                 /* (2) */
 531                                 src += 2;
 532                                 while (is_dir_sep(*src))
 533                                         src++;
 534                                 continue;
 535                         } else if (src[1] == '.') {
 536                                 if (!src[2]) {
 537                                         /* (3) */
 538                                         src += 2;
 539                                         goto up_one;
 540                                 } else if (is_dir_sep(src[2])) {
 541                                         /* (4) */
 542                                         src += 3;
 543                                         while (is_dir_sep(*src))
 544                                                 src++;
 545                                         goto up_one;
 546                                 }
 547                         }
 548                 }
 549
 550                 /* copy up to the next '/', and eat all '/' */
 551                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 552                         *dst++ = c;
 553                 if (is_dir_sep(c)) {
 554                         *dst++ = '/';
 555                         while (is_dir_sep(c))
 556                                 c = *src++;
 557                         src--;
 558                 } else if (!c)
 559                         break;
 560                 continue;
 561
 562         up_one:
 563                 /*
 564                  * dst0..dst is prefix portion, and dst[-1] is '/';
 565                  * go up one level.
 566                  */
 567                 dst--;  /* go to trailing '/' */
 568                 if (dst <= dst0)
 569                         return -1;
 570                 /* Windows: dst[-1] cannot be backslash anymore */
 571                 while (dst0 < dst && dst[-1] != '/')
 572                         dst--;
 573         }
 574         *dst = '\0';
 575         return 0;
 576 }
 577
 578 /*
 579  * path = Canonical absolute path
 580  * prefix_list = Colon-separated list of absolute paths
 581  *
 582  * Determines, for each path in prefix_list, whether the "prefix" really
 583  * is an ancestor directory of path.  Returns the length of the longest
 584  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 585  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 586  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 587  * are not considered to be their own ancestors.  path must be in a
 588  * canonical form: empty components, or "." or ".." components are not
 589  * allowed.  prefix_list may be null, which is like "".
 590  */
 591 int longest_ancestor_length(const char *path, const char *prefix_list)
 592 {
 593         char buf[PATH_MAX+1];
 594         const char *ceil, *colon;
 595         int len, max_len = -1;
 596
 597         if (prefix_list == NULL || !strcmp(path, "/"))
 598                 return -1;
 599
 600         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 601                 for (colon = ceil; *colon && *colon != PATH_SEP; colon++);
 602                 len = colon - ceil;
 603                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 604                         continue;
 605                 strlcpy(buf, ceil, len+1);
 606                 if (normalize_path_copy(buf, buf) < 0)
 607                         continue;
 608                 len = strlen(buf);
 609                 if (len > 0 && buf[len-1] == '/')
 610                         buf[--len] = '\0';
 611
 612                 if (!strncmp(path, buf, len) &&
 613                     path[len] == '/' &&
 614                     len > max_len) {
 615                         max_len = len;
 616                 }
 617         }
 618
 619         return max_len;
 620 }
 621
 622 /* strip arbitrary amount of directory separators at end of path */
 623 static inline int chomp_trailing_dir_sep(const char *path, int len)
 624 {
 625         while (len && is_dir_sep(path[len - 1]))
 626                 len--;
 627         return len;
 628 }
 629
 630 /*
 631  * If path ends with suffix (complete path components), returns the
 632  * part before suffix (sans trailing directory separators).
 633  * Otherwise returns NULL.
 634  */
 635 char *strip_path_suffix(const char *path, const char *suffix)
 636 {
 637         int path_len = strlen(path), suffix_len = strlen(suffix);
 638
 639         while (suffix_len) {
 640                 if (!path_len)
 641                         return NULL;
 642
 643                 if (is_dir_sep(path[path_len - 1])) {
 644                         if (!is_dir_sep(suffix[suffix_len - 1]))
 645                                 return NULL;
 646                         path_len = chomp_trailing_dir_sep(path, path_len);
 647                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 648                 }
 649                 else if (path[--path_len] != suffix[--suffix_len])
 650                         return NULL;
 651         }
 652
 653         if (path_len && !is_dir_sep(path[path_len - 1]))
 654                 return NULL;
 655         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 656 }
 657
 658 int daemon_avoid_alias(const char *p)
 659 {
 660         int sl, ndot;
 661
 662         /*
 663          * This resurrects the belts and suspenders paranoia check by HPA
 664          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 665          * does not do getcwd() based path canonicalization.
 666          *
 667          * sl becomes true immediately after seeing '/' and continues to
 668          * be true as long as dots continue after that without intervening
 669          * non-dot character.
 670          */
 671         if (!p || (*p != '/' && *p != '~'))
 672                 return -1;
 673         sl = 1; ndot = 0;
 674         p++;
 675
 676         while (1) {
 677                 char ch = *p++;
 678                 if (sl) {
 679                         if (ch == '.')
 680                                 ndot++;
 681                         else if (ch == '/') {
 682                                 if (ndot < 3)
 683                                         /* reject //, /./ and /../ */
 684                                         return -1;
 685                                 ndot = 0;
 686                         }
 687                         else if (ch == 0) {
 688                                 if (0 < ndot && ndot < 3)
 689                                         /* reject /.$ and /..$ */
 690                                         return -1;
 691                                 return 0;
 692                         }
 693                         else
 694                                 sl = ndot = 0;
 695                 }
 696                 else if (ch == 0)
 697                         return 0;
 698                 else if (ch == '/') {
 699                         sl = 1;
 700                         ndot = 0;
 701                 }
 702         }
 703 }
 704
 705 int offset_1st_component(const char *path)
 706 {
 707         if (has_dos_drive_prefix(path))
 708                 return 2 + is_dir_sep(path[2]);
 709         return is_dir_sep(path[0]);
 710 }