path.c

   1 /*
   2  * I'm tired of doing "vsnprintf()" etc just to open a
   3  * file, so here's a "return static buffer with printf"
   4  * interface for paths.
   5  *
   6  * It's obviously not thread-safe. Sue me. But it's quite
   7  * useful for doing things like
   8  *
   9  *   f = open(mkpath("%s/%s.git", base, name), O_RDONLY);
  10  *
  11  * which is what it's designed for.
  12  */
  13 #include "cache.h"
  14 #include "strbuf.h"
  15
  16 static char bad_path[] = "/bad-path/";
  17
  18 static char *get_pathname(void)
  19 {
  20         static char pathname_array[4][PATH_MAX];
  21         static int index;
  22         return pathname_array[3 & ++index];
  23 }
  24
  25 static char *cleanup_path(char *path)
  26 {
  27         /* Clean it up */
  28         if (!memcmp(path, "./", 2)) {
  29                 path += 2;
  30                 while (*path == '/')
  31                         path++;
  32         }
  33         return path;
  34 }
  35
  36 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  37 {
  38         va_list args;
  39         unsigned len;
  40
  41         va_start(args, fmt);
  42         len = vsnprintf(buf, n, fmt, args);
  43         va_end(args);
  44         if (len >= n) {
  45                 strlcpy(buf, bad_path, n);
  46                 return buf;
  47         }
  48         return cleanup_path(buf);
  49 }
  50
  51 static char *git_vsnpath(char *buf, size_t n, const char *fmt, va_list args)
  52 {
  53         const char *git_dir = get_git_dir();
  54         size_t len;
  55
  56         len = strlen(git_dir);
  57         if (n < len + 1)
  58                 goto bad;
  59         memcpy(buf, git_dir, len);
  60         if (len && !is_dir_sep(git_dir[len-1]))
  61                 buf[len++] = '/';
  62         len += vsnprintf(buf + len, n - len, fmt, args);
  63         if (len >= n)
  64                 goto bad;
  65         return cleanup_path(buf);
  66 bad:
  67         strlcpy(buf, bad_path, n);
  68         return buf;
  69 }
  70
  71 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  72 {
  73         va_list args;
  74         va_start(args, fmt);
  75         (void)git_vsnpath(buf, n, fmt, args);
  76         va_end(args);
  77         return buf;
  78 }
  79
  80 char *git_pathdup(const char *fmt, ...)
  81 {
  82         char path[PATH_MAX];
  83         va_list args;
  84         va_start(args, fmt);
  85         (void)git_vsnpath(path, sizeof(path), fmt, args);
  86         va_end(args);
  87         return xstrdup(path);
  88 }
  89
  90 char *mkpath(const char *fmt, ...)
  91 {
  92         va_list args;
  93         unsigned len;
  94         char *pathname = get_pathname();
  95
  96         va_start(args, fmt);
  97         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  98         va_end(args);
  99         if (len >= PATH_MAX)
 100                 return bad_path;
 101         return cleanup_path(pathname);
 102 }
 103
 104 char *git_path(const char *fmt, ...)
 105 {
 106         const char *git_dir = get_git_dir();
 107         char *pathname = get_pathname();
 108         va_list args;
 109         unsigned len;
 110
 111         len = strlen(git_dir);
 112         if (len > PATH_MAX-100)
 113                 return bad_path;
 114         memcpy(pathname, git_dir, len);
 115         if (len && git_dir[len-1] != '/')
 116                 pathname[len++] = '/';
 117         va_start(args, fmt);
 118         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 119         va_end(args);
 120         if (len >= PATH_MAX)
 121                 return bad_path;
 122         return cleanup_path(pathname);
 123 }
 124
 125
 126 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
 127 int git_mkstemp(char *path, size_t len, const char *template)
 128 {
 129         const char *tmp;
 130         size_t n;
 131
 132         tmp = getenv("TMPDIR");
 133         if (!tmp)
 134                 tmp = "/tmp";
 135         n = snprintf(path, len, "%s/%s", tmp, template);
 136         if (len <= n) {
 137                 errno = ENAMETOOLONG;
 138                 return -1;
 139         }
 140         return mkstemp(path);
 141 }
 142
 143 /* git_mkstemps() - create tmp file with suffix honoring TMPDIR variable. */
 144 int git_mkstemps(char *path, size_t len, const char *template, int suffix_len)
 145 {
 146         const char *tmp;
 147         size_t n;
 148
 149         tmp = getenv("TMPDIR");
 150         if (!tmp)
 151                 tmp = "/tmp";
 152         n = snprintf(path, len, "%s/%s", tmp, template);
 153         if (len <= n) {
 154                 errno = ENAMETOOLONG;
 155                 return -1;
 156         }
 157         return mkstemps(path, suffix_len);
 158 }
 159
 160 /* Adapted from libiberty's mkstemp.c. */
 161
 162 #undef TMP_MAX
 163 #define TMP_MAX 16384
 164
 165 int git_mkstemps_mode(char *pattern, int suffix_len, int mode)
 166 {
 167         static const char letters[] =
 168                 "abcdefghijklmnopqrstuvwxyz"
 169                 "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 170                 "0123456789";
 171         static const int num_letters = 62;
 172         uint64_t value;
 173         struct timeval tv;
 174         char *template;
 175         size_t len;
 176         int fd, count;
 177
 178         len = strlen(pattern);
 179
 180         if (len < 6 + suffix_len) {
 181                 errno = EINVAL;
 182                 return -1;
 183         }
 184
 185         if (strncmp(&pattern[len - 6 - suffix_len], "XXXXXX", 6)) {
 186                 errno = EINVAL;
 187                 return -1;
 188         }
 189
 190         /*
 191          * Replace pattern's XXXXXX characters with randomness.
 192          * Try TMP_MAX different filenames.
 193          */
 194         gettimeofday(&tv, NULL);
 195         value = ((size_t)(tv.tv_usec << 16)) ^ tv.tv_sec ^ getpid();
 196         template = &pattern[len - 6 - suffix_len];
 197         for (count = 0; count < TMP_MAX; ++count) {
 198                 uint64_t v = value;
 199                 /* Fill in the random bits. */
 200                 template[0] = letters[v % num_letters]; v /= num_letters;
 201                 template[1] = letters[v % num_letters]; v /= num_letters;
 202                 template[2] = letters[v % num_letters]; v /= num_letters;
 203                 template[3] = letters[v % num_letters]; v /= num_letters;
 204                 template[4] = letters[v % num_letters]; v /= num_letters;
 205                 template[5] = letters[v % num_letters]; v /= num_letters;
 206
 207                 fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
 208                 if (fd > 0)
 209                         return fd;
 210                 /*
 211                  * Fatal error (EPERM, ENOSPC etc).
 212                  * It doesn't make sense to loop.
 213                  */
 214                 if (errno != EEXIST)
 215                         break;
 216                 /*
 217                  * This is a random value.  It is only necessary that
 218                  * the next TMP_MAX values generated by adding 7777 to
 219                  * VALUE are different with (module 2^32).
 220                  */
 221                 value += 7777;
 222         }
 223         /* We return the null string if we can't find a unique file name.  */
 224         pattern[0] = '\0';
 225         errno = EINVAL;
 226         return -1;
 227 }
 228
 229 int git_mkstemp_mode(char *pattern, int mode)
 230 {
 231         /* mkstemp is just mkstemps with no suffix */
 232         return git_mkstemps_mode(pattern, 0, mode);
 233 }
 234
 235 int gitmkstemps(char *pattern, int suffix_len)
 236 {
 237         return git_mkstemps_mode(pattern, suffix_len, 0600);
 238 }
 239
 240 int validate_headref(const char *path)
 241 {
 242         struct stat st;
 243         char *buf, buffer[256];
 244         unsigned char sha1[20];
 245         int fd;
 246         ssize_t len;
 247
 248         if (lstat(path, &st) < 0)
 249                 return -1;
 250
 251         /* Make sure it is a "refs/.." symlink */
 252         if (S_ISLNK(st.st_mode)) {
 253                 len = readlink(path, buffer, sizeof(buffer)-1);
 254                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 255                         return 0;
 256                 return -1;
 257         }
 258
 259         /*
 260          * Anything else, just open it and try to see if it is a symbolic ref.
 261          */
 262         fd = open(path, O_RDONLY);
 263         if (fd < 0)
 264                 return -1;
 265         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 266         close(fd);
 267
 268         /*
 269          * Is it a symbolic ref?
 270          */
 271         if (len < 4)
 272                 return -1;
 273         if (!memcmp("ref:", buffer, 4)) {
 274                 buf = buffer + 4;
 275                 len -= 4;
 276                 while (len && isspace(*buf))
 277                         buf++, len--;
 278                 if (len >= 5 && !memcmp("refs/", buf, 5))
 279                         return 0;
 280         }
 281
 282         /*
 283          * Is this a detached HEAD?
 284          */
 285         if (!get_sha1_hex(buffer, sha1))
 286                 return 0;
 287
 288         return -1;
 289 }
 290
 291 static struct passwd *getpw_str(const char *username, size_t len)
 292 {
 293         struct passwd *pw;
 294         char *username_z = xmalloc(len + 1);
 295         memcpy(username_z, username, len);
 296         username_z[len] = '\0';
 297         pw = getpwnam(username_z);
 298         free(username_z);
 299         return pw;
 300 }
 301
 302 /*
 303  * Return a string with ~ and ~user expanded via getpw*.  If buf != NULL,
 304  * then it is a newly allocated string. Returns NULL on getpw failure or
 305  * if path is NULL.
 306  */
 307 char *expand_user_path(const char *path)
 308 {
 309         struct strbuf user_path = STRBUF_INIT;
 310         const char *first_slash = strchrnul(path, '/');
 311         const char *to_copy = path;
 312
 313         if (path == NULL)
 314                 goto return_null;
 315         if (path[0] == '~') {
 316                 const char *username = path + 1;
 317                 size_t username_len = first_slash - username;
 318                 if (username_len == 0) {
 319                         const char *home = getenv("HOME");
 320                         strbuf_add(&user_path, home, strlen(home));
 321                 } else {
 322                         struct passwd *pw = getpw_str(username, username_len);
 323                         if (!pw)
 324                                 goto return_null;
 325                         strbuf_add(&user_path, pw->pw_dir, strlen(pw->pw_dir));
 326                 }
 327                 to_copy = first_slash;
 328         }
 329         strbuf_add(&user_path, to_copy, strlen(to_copy));
 330         return strbuf_detach(&user_path, NULL);
 331 return_null:
 332         strbuf_release(&user_path);
 333         return NULL;
 334 }
 335
 336 /*
 337  * First, one directory to try is determined by the following algorithm.
 338  *
 339  * (0) If "strict" is given, the path is used as given and no DWIM is
 340  *     done. Otherwise:
 341  * (1) "~/path" to mean path under the running user's home directory;
 342  * (2) "~user/path" to mean path under named user's home directory;
 343  * (3) "relative/path" to mean cwd relative directory; or
 344  * (4) "/absolute/path" to mean absolute directory.
 345  *
 346  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 347  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 348  * what we try.
 349  *
 350  * Second, we try chdir() to that.  Upon failure, we return NULL.
 351  *
 352  * Then, we try if the current directory is a valid git repository.
 353  * Upon failure, we return NULL.
 354  *
 355  * If all goes well, we return the directory we used to chdir() (but
 356  * before ~user is expanded), avoiding getcwd() resolving symbolic
 357  * links.  User relative paths are also returned as they are given,
 358  * except DWIM suffixing.
 359  */
 360 char *enter_repo(char *path, int strict)
 361 {
 362         static char used_path[PATH_MAX];
 363         static char validated_path[PATH_MAX];
 364
 365         if (!path)
 366                 return NULL;
 367
 368         if (!strict) {
 369                 static const char *suffix[] = {
 370                         ".git/.git", "/.git", ".git", "", NULL,
 371                 };
 372                 int len = strlen(path);
 373                 int i;
 374                 while ((1 < len) && (path[len-1] == '/')) {
 375                         path[len-1] = 0;
 376                         len--;
 377                 }
 378                 if (PATH_MAX <= len)
 379                         return NULL;
 380                 if (path[0] == '~') {
 381                         char *newpath = expand_user_path(path);
 382                         if (!newpath || (PATH_MAX - 10 < strlen(newpath))) {
 383                                 free(newpath);
 384                                 return NULL;
 385                         }
 386                         /*
 387                          * Copy back into the static buffer. A pity
 388                          * since newpath was not bounded, but other
 389                          * branches of the if are limited by PATH_MAX
 390                          * anyway.
 391                          */
 392                         strcpy(used_path, newpath); free(newpath);
 393                         strcpy(validated_path, path);
 394                         path = used_path;
 395                 }
 396                 else if (PATH_MAX - 10 < len)
 397                         return NULL;
 398                 else {
 399                         path = strcpy(used_path, path);
 400                         strcpy(validated_path, path);
 401                 }
 402                 len = strlen(path);
 403                 for (i = 0; suffix[i]; i++) {
 404                         strcpy(path + len, suffix[i]);
 405                         if (!access(path, F_OK)) {
 406                                 strcat(validated_path, suffix[i]);
 407                                 break;
 408                         }
 409                 }
 410                 if (!suffix[i] || chdir(path))
 411                         return NULL;
 412                 path = validated_path;
 413         }
 414         else if (chdir(path))
 415                 return NULL;
 416
 417         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 418             validate_headref("HEAD") == 0) {
 419                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 420                 check_repository_format();
 421                 return path;
 422         }
 423
 424         return NULL;
 425 }
 426
 427 int set_shared_perm(const char *path, int mode)
 428 {
 429         struct stat st;
 430         int tweak, shared, orig_mode;
 431
 432         if (!shared_repository) {
 433                 if (mode)
 434                         return chmod(path, mode & ~S_IFMT);
 435                 return 0;
 436         }
 437         if (!mode) {
 438                 if (lstat(path, &st) < 0)
 439                         return -1;
 440                 mode = st.st_mode;
 441                 orig_mode = mode;
 442         } else
 443                 orig_mode = 0;
 444         if (shared_repository < 0)
 445                 shared = -shared_repository;
 446         else
 447                 shared = shared_repository;
 448         tweak = shared;
 449
 450         if (!(mode & S_IWUSR))
 451                 tweak &= ~0222;
 452         if (mode & S_IXUSR)
 453                 /* Copy read bits to execute bits */
 454                 tweak |= (tweak & 0444) >> 2;
 455         if (shared_repository < 0)
 456                 mode = (mode & ~0777) | tweak;
 457         else
 458                 mode |= tweak;
 459
 460         if (S_ISDIR(mode)) {
 461                 /* Copy read bits to execute bits */
 462                 mode |= (shared & 0444) >> 2;
 463                 mode |= FORCE_DIR_SET_GID;
 464         }
 465
 466         if (((shared_repository < 0
 467               ? (orig_mode & (FORCE_DIR_SET_GID | 0777))
 468               : (orig_mode & mode)) != mode) &&
 469             chmod(path, (mode & ~S_IFMT)) < 0)
 470                 return -2;
 471         return 0;
 472 }
 473
 474 const char *make_relative_path(const char *abs, const char *base)
 475 {
 476         static char buf[PATH_MAX + 1];
 477         int i = 0, j = 0;
 478
 479         if (!base || !base[0])
 480                 return abs;
 481         while (base[i]) {
 482                 if (is_dir_sep(base[i])) {
 483                         if (!is_dir_sep(abs[j]))
 484                                 return abs;
 485                         while (is_dir_sep(base[i]))
 486                                 i++;
 487                         while (is_dir_sep(abs[j]))
 488                                 j++;
 489                         continue;
 490                 } else if (abs[j] != base[i]) {
 491                         return abs;
 492                 }
 493                 i++;
 494                 j++;
 495         }
 496         if (
 497             /* "/foo" is a prefix of "/foo" */
 498             abs[j] &&
 499             /* "/foo" is not a prefix of "/foobar" */
 500             !is_dir_sep(base[i-1]) && !is_dir_sep(abs[j])
 501            )
 502                 return abs;
 503         while (is_dir_sep(abs[j]))
 504                 j++;
 505         if (!abs[j])
 506                 strcpy(buf, ".");
 507         else
 508                 strcpy(buf, abs + j);
 509         return buf;
 510 }
 511
 512 /*
 513  * It is okay if dst == src, but they should not overlap otherwise.
 514  *
 515  * Performs the following normalizations on src, storing the result in dst:
 516  * - Ensures that components are separated by '/' (Windows only)
 517  * - Squashes sequences of '/'.
 518  * - Removes "." components.
 519  * - Removes ".." components, and the components the precede them.
 520  * Returns failure (non-zero) if a ".." component appears as first path
 521  * component anytime during the normalization. Otherwise, returns success (0).
 522  *
 523  * Note that this function is purely textual.  It does not follow symlinks,
 524  * verify the existence of the path, or make any system calls.
 525  */
 526 int normalize_path_copy(char *dst, const char *src)
 527 {
 528         char *dst0;
 529
 530         if (has_dos_drive_prefix(src)) {
 531                 *dst++ = *src++;
 532                 *dst++ = *src++;
 533         }
 534         dst0 = dst;
 535
 536         if (is_dir_sep(*src)) {
 537                 *dst++ = '/';
 538                 while (is_dir_sep(*src))
 539                         src++;
 540         }
 541
 542         for (;;) {
 543                 char c = *src;
 544
 545                 /*
 546                  * A path component that begins with . could be
 547                  * special:
 548                  * (1) "." and ends   -- ignore and terminate.
 549                  * (2) "./"           -- ignore them, eat slash and continue.
 550                  * (3) ".." and ends  -- strip one and terminate.
 551                  * (4) "../"          -- strip one, eat slash and continue.
 552                  */
 553                 if (c == '.') {
 554                         if (!src[1]) {
 555                                 /* (1) */
 556                                 src++;
 557                         } else if (is_dir_sep(src[1])) {
 558                                 /* (2) */
 559                                 src += 2;
 560                                 while (is_dir_sep(*src))
 561                                         src++;
 562                                 continue;
 563                         } else if (src[1] == '.') {
 564                                 if (!src[2]) {
 565                                         /* (3) */
 566                                         src += 2;
 567                                         goto up_one;
 568                                 } else if (is_dir_sep(src[2])) {
 569                                         /* (4) */
 570                                         src += 3;
 571                                         while (is_dir_sep(*src))
 572                                                 src++;
 573                                         goto up_one;
 574                                 }
 575                         }
 576                 }
 577
 578                 /* copy up to the next '/', and eat all '/' */
 579                 while ((c = *src++) != '\0' && !is_dir_sep(c))
 580                         *dst++ = c;
 581                 if (is_dir_sep(c)) {
 582                         *dst++ = '/';
 583                         while (is_dir_sep(c))
 584                                 c = *src++;
 585                         src--;
 586                 } else if (!c)
 587                         break;
 588                 continue;
 589
 590         up_one:
 591                 /*
 592                  * dst0..dst is prefix portion, and dst[-1] is '/';
 593                  * go up one level.
 594                  */
 595                 dst--;  /* go to trailing '/' */
 596                 if (dst <= dst0)
 597                         return -1;
 598                 /* Windows: dst[-1] cannot be backslash anymore */
 599                 while (dst0 < dst && dst[-1] != '/')
 600                         dst--;
 601         }
 602         *dst = '\0';
 603         return 0;
 604 }
 605
 606 /*
 607  * path = Canonical absolute path
 608  * prefix_list = Colon-separated list of absolute paths
 609  *
 610  * Determines, for each path in prefix_list, whether the "prefix" really
 611  * is an ancestor directory of path.  Returns the length of the longest
 612  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 613  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 614  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 615  * are not considered to be their own ancestors.  path must be in a
 616  * canonical form: empty components, or "." or ".." components are not
 617  * allowed.  prefix_list may be null, which is like "".
 618  */
 619 int longest_ancestor_length(const char *path, const char *prefix_list)
 620 {
 621         char buf[PATH_MAX+1];
 622         const char *ceil, *colon;
 623         int len, max_len = -1;
 624
 625         if (prefix_list == NULL || !strcmp(path, "/"))
 626                 return -1;
 627
 628         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 629                 for (colon = ceil; *colon && *colon != PATH_SEP; colon++);
 630                 len = colon - ceil;
 631                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 632                         continue;
 633                 strlcpy(buf, ceil, len+1);
 634                 if (normalize_path_copy(buf, buf) < 0)
 635                         continue;
 636                 len = strlen(buf);
 637                 if (len > 0 && buf[len-1] == '/')
 638                         buf[--len] = '\0';
 639
 640                 if (!strncmp(path, buf, len) &&
 641                     path[len] == '/' &&
 642                     len > max_len) {
 643                         max_len = len;
 644                 }
 645         }
 646
 647         return max_len;
 648 }
 649
 650 /* strip arbitrary amount of directory separators at end of path */
 651 static inline int chomp_trailing_dir_sep(const char *path, int len)
 652 {
 653         while (len && is_dir_sep(path[len - 1]))
 654                 len--;
 655         return len;
 656 }
 657
 658 /*
 659  * If path ends with suffix (complete path components), returns the
 660  * part before suffix (sans trailing directory separators).
 661  * Otherwise returns NULL.
 662  */
 663 char *strip_path_suffix(const char *path, const char *suffix)
 664 {
 665         int path_len = strlen(path), suffix_len = strlen(suffix);
 666
 667         while (suffix_len) {
 668                 if (!path_len)
 669                         return NULL;
 670
 671                 if (is_dir_sep(path[path_len - 1])) {
 672                         if (!is_dir_sep(suffix[suffix_len - 1]))
 673                                 return NULL;
 674                         path_len = chomp_trailing_dir_sep(path, path_len);
 675                         suffix_len = chomp_trailing_dir_sep(suffix, suffix_len);
 676                 }
 677                 else if (path[--path_len] != suffix[--suffix_len])
 678                         return NULL;
 679         }
 680
 681         if (path_len && !is_dir_sep(path[path_len - 1]))
 682                 return NULL;
 683         return xstrndup(path, chomp_trailing_dir_sep(path, path_len));
 684 }
 685
 686 int daemon_avoid_alias(const char *p)
 687 {
 688         int sl, ndot;
 689
 690         /*
 691          * This resurrects the belts and suspenders paranoia check by HPA
 692          * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
 693          * does not do getcwd() based path canonicalizations.
 694          *
 695          * sl becomes true immediately after seeing '/' and continues to
 696          * be true as long as dots continue after that without intervening
 697          * non-dot character.
 698          */
 699         if (!p || (*p != '/' && *p != '~'))
 700                 return -1;
 701         sl = 1; ndot = 0;
 702         p++;
 703
 704         while (1) {
 705                 char ch = *p++;
 706                 if (sl) {
 707                         if (ch == '.')
 708                                 ndot++;
 709                         else if (ch == '/') {
 710                                 if (ndot < 3)
 711                                         /* reject //, /./ and /../ */
 712                                         return -1;
 713                                 ndot = 0;
 714                         }
 715                         else if (ch == 0) {
 716                                 if (0 < ndot && ndot < 3)
 717                                         /* reject /.$ and /..$ */
 718                                         return -1;
 719                                 return 0;
 720                         }
 721                         else
 722                                 sl = ndot = 0;
 723                 }
 724                 else if (ch == 0)
 725                         return 0;
 726                 else if (ch == '/') {
 727                         sl = 1;
 728                         ndot = 0;
 729                 }
 730         }
 731 }