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