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