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 #include "string-list.h"
  16
  17 #ifndef get_st_mode_bits
  18 /*
  19  * The replacement lstat(2) we use on Cygwin is incomplete and
  20  * may return wrong permission bits. Most of the time we do not care,
  21  * but the callsites of this wrapper do care.
  22  */
  23 int get_st_mode_bits(const char *path, int *mode)
  24 {
  25         struct stat st;
  26         if (lstat(path, &st) < 0)
  27                 return -1;
  28         *mode = st.st_mode;
  29         return 0;
  30 }
  31 #endif
  32
  33 static char bad_path[] = "/bad-path/";
  34
  35 static char *get_pathname(void)
  36 {
  37         static char pathname_array[4][PATH_MAX];
  38         static int index;
  39         return pathname_array[3 & ++index];
  40 }
  41
  42 static char *cleanup_path(char *path)
  43 {
  44         /* Clean it up */
  45         if (!memcmp(path, "./", 2)) {
  46                 path += 2;
  47                 while (*path == '/')
  48                         path++;
  49         }
  50         return path;
  51 }
  52
  53 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  54 {
  55         va_list args;
  56         unsigned len;
  57
  58         va_start(args, fmt);
  59         len = vsnprintf(buf, n, fmt, args);
  60         va_end(args);
  61         if (len >= n) {
  62                 strlcpy(buf, bad_path, n);
  63                 return buf;
  64         }
  65         return cleanup_path(buf);
  66 }
  67
  68 static char *vsnpath(char *buf, size_t n, const char *fmt, va_list args)
  69 {
  70         const char *git_dir = get_git_dir();
  71         size_t len;
  72
  73         len = strlen(git_dir);
  74         if (n < len + 1)
  75                 goto bad;
  76         memcpy(buf, git_dir, len);
  77         if (len && !is_dir_sep(git_dir[len-1]))
  78                 buf[len++] = '/';
  79         len += vsnprintf(buf + len, n - len, fmt, args);
  80         if (len >= n)
  81                 goto bad;
  82         return cleanup_path(buf);
  83 bad:
  84         strlcpy(buf, bad_path, n);
  85         return buf;
  86 }
  87
  88 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  89 {
  90         char *ret;
  91         va_list args;
  92         va_start(args, fmt);
  93         ret = vsnpath(buf, n, fmt, args);
  94         va_end(args);
  95         return ret;
  96 }
  97
  98 char *git_pathdup(const char *fmt, ...)
  99 {
 100         char path[PATH_MAX], *ret;
 101         va_list args;
 102         va_start(args, fmt);
 103         ret = vsnpath(path, sizeof(path), fmt, args);
 104         va_end(args);
 105         return xstrdup(ret);
 106 }
 107
 108 char *mkpathdup(const char *fmt, ...)
 109 {
 110         char *path;
 111         struct strbuf sb = STRBUF_INIT;
 112         va_list args;
 113
 114         va_start(args, fmt);
 115         strbuf_vaddf(&sb, fmt, args);
 116         va_end(args);
 117         path = xstrdup(cleanup_path(sb.buf));
 118
 119         strbuf_release(&sb);
 120         return path;
 121 }
 122
 123 char *mkpath(const char *fmt, ...)
 124 {
 125         va_list args;
 126         unsigned len;
 127         char *pathname = get_pathname();
 128
 129         va_start(args, fmt);
 130         len = vsnprintf(pathname, PATH_MAX, fmt, args);
 131         va_end(args);
 132         if (len >= PATH_MAX)
 133                 return bad_path;
 134         return cleanup_path(pathname);
 135 }
 136
 137 char *git_path(const char *fmt, ...)
 138 {
 139         char *pathname = get_pathname();
 140         va_list args;
 141         char *ret;
 142
 143         va_start(args, fmt);
 144         ret = vsnpath(pathname, PATH_MAX, fmt, args);
 145         va_end(args);
 146         return ret;
 147 }
 148
 149 void home_config_paths(char **global, char **xdg, char *file)
 150 {
 151         char *xdg_home = getenv("XDG_CONFIG_HOME");
 152         char *home = getenv("HOME");
 153         char *to_free = NULL;
 154
 155         if (!home) {
 156                 if (global)
 157                         *global = NULL;
 158         } else {
 159                 if (!xdg_home) {
 160                         to_free = mkpathdup("%s/.config", home);
 161                         xdg_home = to_free;
 162                 }
 163                 if (global)
 164                         *global = mkpathdup("%s/.gitconfig", home);
 165         }
 166
 167         if (!xdg_home)
 168                 *xdg = NULL;
 169         else
 170                 *xdg = mkpathdup("%s/git/%s", xdg_home, file);
 171
 172         free(to_free);
 173 }
 174
 175 char *git_path_submodule(const char *path, const char *fmt, ...)
 176 {
 177         char *pathname = get_pathname();
 178         struct strbuf buf = STRBUF_INIT;
 179         const char *git_dir;
 180         va_list args;
 181         unsigned len;
 182
 183         len = strlen(path);
 184         if (len > PATH_MAX-100)
 185                 return bad_path;
 186
 187         strbuf_addstr(&buf, path);
 188         if (len && path[len-1] != '/')
 189                 strbuf_addch(&buf, '/');
 190         strbuf_addstr(&buf, ".git");
 191
 192         git_dir = read_gitfile(buf.buf);
 193         if (git_dir) {
 194                 strbuf_reset(&buf);
 195                 strbuf_addstr(&buf, git_dir);
 196         }
 197         strbuf_addch(&buf, '/');
 198
 199         if (buf.len >= PATH_MAX)
 200                 return bad_path;
 201         memcpy(pathname, buf.buf, buf.len + 1);
 202
 203         strbuf_release(&buf);
 204         len = strlen(pathname);
 205
 206         va_start(args, fmt);
 207         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 208         va_end(args);
 209         if (len >= PATH_MAX)
 210                 return bad_path;
 211         return cleanup_path(pathname);
 212 }
 213
 214 int validate_headref(const char *path)
 215 {
 216         struct stat st;
 217         char *buf, buffer[256];
 218         unsigned char sha1[20];
 219         int fd;
 220         ssize_t len;
 221
 222         if (lstat(path, &st) < 0)
 223                 return -1;
 224
 225         /* Make sure it is a "refs/.." symlink */
 226         if (S_ISLNK(st.st_mode)) {
 227                 len = readlink(path, buffer, sizeof(buffer)-1);
 228                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 229                         return 0;
 230                 return -1;
 231         }
 232
 233         /*
 234          * Anything else, just open it and try to see if it is a symbolic ref.
 235          */
 236         fd = open(path, O_RDONLY);
 237         if (fd < 0)
 238                 return -1;
 239         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 240         close(fd);
 241
 242         /*
 243          * Is it a symbolic ref?
 244          */
 245         if (len < 4)
 246                 return -1;
 247         if (!memcmp("ref:", buffer, 4)) {
 248                 buf = buffer + 4;
 249                 len -= 4;
 250                 while (len && isspace(*buf))
 251                         buf++, len--;
 252                 if (len >= 5 && !memcmp("refs/", buf, 5))
 253                         return 0;
 254         }
 255
 256         /*
 257          * Is this a detached HEAD?
 258          */
 259         if (!get_sha1_hex(buffer, sha1))
 260                 return 0;
 261
 262         return -1;
 263 }
 264
 265 static struct passwd *getpw_str(const char *username, size_t len)
 266 {
 267         struct passwd *pw;
 268         char *username_z = xmalloc(len + 1);
 269         memcpy(username_z, username, len);
 270         username_z[len] = '\0';
 271         pw = getpwnam(username_z);
 272         free(username_z);
 273         return pw;
 274 }
 275
 276 /*
 277  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 278  * then it is a newly allocated string. Returns NULL on getpw failure or
 279  * if path is NULL.
 280  */
 281 char *expand_user_path(const char *path)
 282 {
 283         struct strbuf user_path = STRBUF_INIT;
 284         const char *first_slash = strchrnul(path, '/');
 285         const char *to_copy = path;
 286
 287         if (path == NULL)
 288                 goto return_null;
 289         if (path[0] == '~') {
 290                 const char *username = path + 1;
 291                 size_t username_len = first_slash - username;
 292                 if (username_len == 0) {
 293                         const char *home = getenv("HOME");
 294                         if (!home)
 295                                 goto return_null;
 296                         strbuf_add(&user_path, home, strlen(home));
 297                 } else {
 298                         struct passwd *pw = getpw_str(username, username_len);
 299                         if (!pw)
 300                                 goto return_null;
 301                         strbuf_add(&user_path, pw->pw_dir, strlen(pw->pw_dir));
 302                 }
 303                 to_copy = first_slash;
 304         }
 305         strbuf_add(&user_path, to_copy, strlen(to_copy));
 306         return strbuf_detach(&user_path, NULL);
 307 return_null:
 308         strbuf_release(&user_path);
 309         return NULL;
 310 }
 311
 312 /*
 313  * First, one directory to try is determined by the following algorithm.
 314  *
 315  * (0) If "strict" is given, the path is used as given and no DWIM is
 316  *     done. Otherwise:
 317  * (1) "~/path" to mean path under the running user's home directory;
 318  * (2) "~user/path" to mean path under named user's home directory;
 319  * (3) "relative/path" to mean cwd relative directory; or
 320  * (4) "/absolute/path" to mean absolute directory.
 321  *
 322  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 323  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 324  * what we try.
 325  *
 326  * Second, we try chdir() to that.  Upon failure, we return NULL.
 327  *
 328  * Then, we try if the current directory is a valid git repository.
 329  * Upon failure, we return NULL.
 330  *
 331  * If all goes well, we return the directory we used to chdir() (but
 332  * before ~user is expanded), avoiding getcwd() resolving symbolic
 333  * links.  User relative paths are also returned as they are given,
 334  * except DWIM suffixing.
 335  */
 336 const char *enter_repo(const char *path, int strict)
 337 {
 338         static char used_path[PATH_MAX];
 339         static char validated_path[PATH_MAX];
 340
 341         if (!path)
 342                 return NULL;
 343
 344         if (!strict) {
 345                 static const char *suffix[] = {
 346                         "/.git", "", ".git/.git", ".git", NULL,
 347                 };
 348                 const char *gitfile;
 349                 int len = strlen(path);
 350                 int i;
 351                 while ((1 < len) && (path[len-1] == '/'))
 352                         len--;
 353
 354                 if (PATH_MAX <= len)
 355                         return NULL;
 356                 strncpy(used_path, path, len); used_path[len] = 0 ;
 357                 strcpy(validated_path, used_path);
 358
 359                 if (used_path[0] == '~') {
 360                         char *newpath = expand_user_path(used_path);
 361                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 362                                 free(newpath);
 363                                 return NULL;
 364                         }
 365                         /*
 366                          * Copy back into the static buffer. A pity
 367                          * since newpath was not bounded, but other
 368                          * branches of the if are limited by PATH_MAX
 369                          * anyway.
 370                          */
 371                         strcpy(used_path, newpath); free(newpath);
 372                 }
 373                 else if (PATH_MAX - 10 < len)
 374                         return NULL;
 375                 len = strlen(used_path);
 376                 for (i = 0; suffix[i]; i++) {
 377                         struct stat st;
 378                         strcpy(used_path + len, suffix[i]);
 379                         if (!stat(used_path, &st) &&
 380                             (S_ISREG(st.st_mode) ||
 381                             (S_ISDIR(st.st_mode) && is_git_directory(used_path)))) {
 382                                 strcat(validated_path, suffix[i]);
 383                                 break;
 384                         }
 385                 }
 386                 if (!suffix[i])
 387                         return NULL;
 388                 gitfile = read_gitfile(used_path) ;
 389                 if (gitfile)
 390                         strcpy(used_path, gitfile);
 391                 if (chdir(used_path))
 392                         return NULL;
 393                 path = validated_path;
 394         }
 395         else if (chdir(path))
 396                 return NULL;
 397
 398         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 399             validate_headref("HEAD") == 0) {
 400                 set_git_dir(".");
 401                 check_repository_format();
 402                 return path;
 403         }
 404
 405         return NULL;
 406 }
 407
 408 int set_shared_perm(const char *path, int mode)
 409 {
 410         int tweak, shared, orig_mode;
 411
 412         if (!shared_repository) {
 413                 if (mode)
 414                         return chmod(path, mode & ~S_IFMT);
 415                 return 0;
 416         }
 417         if (!mode) {
 418                 if (get_st_mode_bits(path, &mode) < 0)
 419                         return -1;
 420                 orig_mode = mode;
 421         } else
 422                 orig_mode = 0;
 423         if (shared_repository < 0)
 424                 shared = -shared_repository;
 425         else
 426                 shared = shared_repository;
 427         tweak = shared;
 428
 429         if (!(mode & S_IWUSR))
 430                 tweak &= ~0222;
 431         if (mode & S_IXUSR)
 432                 /* Copy read bits to execute bits */
 433                 tweak |= (tweak & 0444) >> 2;
 434         if (shared_repository < 0)
 435                 mode = (mode & ~0777) | tweak;
 436         else
 437                 mode |= tweak;
 438
 439         if (S_ISDIR(mode)) {
 440                 /* Copy read bits to execute bits */
 441                 mode |= (shared & 0444) >> 2;
 442                 mode |= FORCE_DIR_SET_GID;
 443         }
 444
 445         if (((shared_repository < 0
 446               ? (orig_mode & (FORCE_DIR_SET_GID | 0777))
 447               : (orig_mode & mode)) != mode) &&
 448             chmod(path, (mode & ~S_IFMT)) < 0)
 449                 return -2;
 450         return 0;
 451 }
 452
 453 const char *relative_path(const char *abs, const char *base)
 454 {
 455         static char buf[PATH_MAX + 1];
 456         int i = 0, j = 0;
 457
 458         if (!base || !base[0])
 459                 return abs;
 460         while (base[i]) {
 461                 if (is_dir_sep(base[i])) {
 462                         if (!is_dir_sep(abs[j]))
 463                                 return abs;
 464                         while (is_dir_sep(base[i]))
 465                                 i++;
 466                         while (is_dir_sep(abs[j]))
 467                                 j++;
 468                         continue;
 469                 } else if (abs[j] != base[i]) {
 470                         return abs;
 471                 }
 472                 i++;
 473                 j++;
 474         }
 475         if (
 476             /* "/foo" is a prefix of "/foo" */
 477             abs[j] &&
 478             /* "/foo" is not a prefix of "/foobar" */
 479             !is_dir_sep(base[i-1]) && !is_dir_sep(abs[j])
 480            )
 481                 return abs;
 482         while (is_dir_sep(abs[j]))
 483                 j++;
 484         if (!abs[j])
 485                 strcpy(buf, ".");
 486         else
 487                 strcpy(buf, abs + j);
 488         return buf;
 489 }
 490
 491 /*
 492  * It is okay if dst == src, but they should not overlap otherwise.
 493  *
 494  * Performs the following normalizations on src, storing the result in dst:
 495  * - Ensures that components are separated by '/' (Windows only)
 496  * - Squashes sequences of '/'.
 497  * - Removes "." components.
 498  * - Removes ".." components, and the components the precede them.
 499  * Returns failure (non-zero) if a ".." component appears as first path
 500  * component anytime during the normalization. Otherwise, returns success (0).
 501  *
 502  * Note that this function is purely textual.  It does not follow symlinks,
 503  * verify the existence of the path, or make any system calls.
 504  */
 505 int normalize_path_copy(char *dst, const char *src)
 506 {
 507         char *dst0;
 508
 509         if (has_dos_drive_prefix(src)) {
 510                 *dst++ = *src++;
 511                 *dst++ = *src++;
 512         }
 513         dst0 = dst;
 514
 515         if (is_dir_sep(*src)) {
 516                 *dst++ = '/';
 517                 while (is_dir_sep(*src))
 518                         src++;
 519         }
 520
 521         for (;;) {
 522                 char c = *src;
 523
 524                 /*
 525                  * A path component that begins with . could be
 526                  * special:
 527                  * (1) "." and ends   -- ignore and terminate.
 528                  * (2) "./"           -- ignore them, eat slash and continue.
 529                  * (3) ".." and ends  -- strip one and terminate.
 530                  * (4) "../"          -- strip one, eat slash and continue.
 531                  */
 532                 if (c == '.') {
 533                         if (!src[1]) {
 534                                 /* (1) */
 535                                 src++;
 536                         } else if (is_dir_sep(src[1])) {
 537                                 /* (2) */
 538                                 src += 2;
 539                                 while (is_dir_sep(*src))
 540                                         src++;
 541                                 continue;
 542                         } else if (src[1] == '.') {
 543                                 if (!src[2]) {
 544                                         /* (3) */
 545                                         src += 2;
 546                                         goto up_one;
 547                                 } else if (is_dir_sep(src[2])) {
 548                                         /* (4) */
 549                                         src += 3;
 550                                         while (is_dir_sep(*src))
 551                                                 src++;
 552                                         goto up_one;
 553                                 }
 554                         }
 555                 }
 556
 557                 /* copy up to the next '/', and eat all '/' */
 558                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 559                         *dst++ = c;
 560                 if (is_dir_sep(c)) {
 561                         *dst++ = '/';
 562                         while (is_dir_sep(c))
 563                                 c = *src++;
 564                         src--;
 565                 } else if (!c)
 566                         break;
 567                 continue;
 568
 569         up_one:
 570                 /*
 571                  * dst0..dst is prefix portion, and dst[-1] is '/';
 572                  * go up one level.
 573                  */
 574                 dst--;  /* go to trailing '/' */
 575                 if (dst <= dst0)
 576                         return -1;
 577                 /* Windows: dst[-1] cannot be backslash anymore */
 578                 while (dst0 < dst && dst[-1] != '/')
 579                         dst--;
 580         }
 581         *dst = '\0';
 582         return 0;
 583 }
 584
 585 /*
 586  * path = Canonical absolute path
 587  * prefixes = string_list containing normalized, absolute paths without
 588  * trailing slashes (except for the root directory, which is denoted by "/").
 589  *
 590  * Determines, for each path in prefixes, whether the "prefix"
 591  * is an ancestor directory of path.  Returns the length of the longest
 592  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 593  * is an ancestor.  (Note that this means 0 is returned if prefixes is
 594  * ["/"].) "/foo" is not considered an ancestor of "/foobar".  Directories
 595  * are not considered to be their own ancestors.  path must be in a
 596  * canonical form: empty components, or "." or ".." components are not
 597  * allowed.
 598  */
 599 int longest_ancestor_length(const char *path, struct string_list *prefixes)
 600 {
 601         int i, max_len = -1;
 602
 603         if (!strcmp(path, "/"))
 604                 return -1;
 605
 606         for (i = 0; i < prefixes->nr; i++) {
 607                 const char *ceil = prefixes->items[i].string;
 608                 int len = strlen(ceil);
 609
 610                 if (len == 1 && ceil[0] == '/')
 611                         len = 0; /* root matches anything, with length 0 */
 612                 else if (!strncmp(path, ceil, len) && path[len] == '/')
 613                         ; /* match of length len */
 614                 else
 615                         continue; /* no match */
 616
 617                 if (len > max_len)
 618                         max_len = len;
 619         }
 620
 621         return max_len;
 622 }
 623
 624 /* strip arbitrary amount of directory separators at end of path */
 625 static inline int chomp_trailing_dir_sep(const char *path, int len)
 626 {
 627         while (len && is_dir_sep(path[len - 1]))
 628                 len--;
 629         return len;
 630 }
 631
 632 /*
 633  * If path ends with suffix (complete path components), returns the
 634  * part before suffix (sans trailing directory separators).
 635  * Otherwise returns NULL.
 636  */
 637 char *strip_path_suffix(const char *path, const char *suffix)
 638 {
 639         int path_len = strlen(path), suffix_len = strlen(suffix);
 640
 641         while (suffix_len) {
 642                 if (!path_len)
 643                         return NULL;
 644
 645                 if (is_dir_sep(path[path_len - 1])) {
 646                         if (!is_dir_sep(suffix[suffix_len - 1]))
 647                                 return NULL;
 648                         path_len = chomp_trailing_dir_sep(path, path_len);
 649                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 650                 }
 651                 else if (path[--path_len] != suffix[--suffix_len])
 652                         return NULL;
 653         }
 654
 655         if (path_len && !is_dir_sep(path[path_len - 1]))
 656                 return NULL;
 657         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 658 }
 659
 660 int daemon_avoid_alias(const char *p)
 661 {
 662         int sl, ndot;
 663
 664         /*
 665          * This resurrects the belts and suspenders paranoia check by HPA
 666          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 667          * does not do getcwd() based path canonicalization.
 668          *
 669          * sl becomes true immediately after seeing '/' and continues to
 670          * be true as long as dots continue after that without intervening
 671          * non-dot character.
 672          */
 673         if (!p || (*p != '/' && *p != '~'))
 674                 return -1;
 675         sl = 1; ndot = 0;
 676         p++;
 677
 678         while (1) {
 679                 char ch = *p++;
 680                 if (sl) {
 681                         if (ch == '.')
 682                                 ndot++;
 683                         else if (ch == '/') {
 684                                 if (ndot < 3)
 685                                         /* reject //, /./ and /../ */
 686                                         return -1;
 687                                 ndot = 0;
 688                         }
 689                         else if (ch == 0) {
 690                                 if (0 < ndot && ndot < 3)
 691                                         /* reject /.$ and /..$ */
 692                                         return -1;
 693                                 return 0;
 694                         }
 695                         else
 696                                 sl = ndot = 0;
 697                 }
 698                 else if (ch == 0)
 699                         return 0;
 700                 else if (ch == '/') {
 701                         sl = 1;
 702                         ndot = 0;
 703                 }
 704         }
 705 }
 706
 707 int offset_1st_component(const char *path)
 708 {
 709         if (has_dos_drive_prefix(path))
 710                 return 2 + is_dir_sep(path[2]);
 711         return is_dir_sep(path[0]);
 712 }