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