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