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
  15 static char bad_path[] = "/bad-path/";
  16
  17 static char *get_pathname(void)
  18 {
  19         static char pathname_array[4][PATH_MAX];
  20         static int index;
  21         return pathname_array[3 & ++index];
  22 }
  23
  24 static char *cleanup_path(char *path)
  25 {
  26         /* Clean it up */
  27         if (!memcmp(path, "./", 2)) {
  28                 path += 2;
  29                 while (*path == '/')
  30                         path++;
  31         }
  32         return path;
  33 }
  34
  35 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
  36 {
  37         va_list args;
  38         unsigned len;
  39
  40         va_start(args, fmt);
  41         len = vsnprintf(buf, n, fmt, args);
  42         va_end(args);
  43         if (len >= n) {
  44                 snprintf(buf, n, bad_path);
  45                 return buf;
  46         }
  47         return cleanup_path(buf);
  48 }
  49
  50 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  51 {
  52         const char *git_dir = get_git_dir();
  53         va_list args;
  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         va_start(args, fmt);
  63         len += vsnprintf(buf + len, n - len, fmt, args);
  64         va_end(args);
  65         if (len >= n)
  66                 goto bad;
  67         return cleanup_path(buf);
  68 bad:
  69         snprintf(buf, n, bad_path);
  70         return buf;
  71 }
  72
  73 char *mkpath(const char *fmt, ...)
  74 {
  75         va_list args;
  76         unsigned len;
  77         char *pathname = get_pathname();
  78
  79         va_start(args, fmt);
  80         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  81         va_end(args);
  82         if (len >= PATH_MAX)
  83                 return bad_path;
  84         return cleanup_path(pathname);
  85 }
  86
  87 char *git_path(const char *fmt, ...)
  88 {
  89         const char *git_dir = get_git_dir();
  90         char *pathname = get_pathname();
  91         va_list args;
  92         unsigned len;
  93
  94         len = strlen(git_dir);
  95         if (len > PATH_MAX-100)
  96                 return bad_path;
  97         memcpy(pathname, git_dir, len);
  98         if (len && git_dir[len-1] != '/')
  99                 pathname[len++] = '/';
 100         va_start(args, fmt);
 101         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 102         va_end(args);
 103         if (len >= PATH_MAX)
 104                 return bad_path;
 105         return cleanup_path(pathname);
 106 }
 107
 108
 109 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
 110 int git_mkstemp(char *path, size_t len, const char *template)
 111 {
 112         const char *tmp;
 113         size_t n;
 114
 115         tmp = getenv("TMPDIR");
 116         if (!tmp)
 117                 tmp = "/tmp";
 118         n = snprintf(path, len, "%s/%s", tmp, template);
 119         if (len <= n) {
 120                 errno = ENAMETOOLONG;
 121                 return -1;
 122         }
 123         return mkstemp(path);
 124 }
 125
 126
 127 int validate_headref(const char *path)
 128 {
 129         struct stat st;
 130         char *buf, buffer[256];
 131         unsigned char sha1[20];
 132         int fd;
 133         ssize_t len;
 134
 135         if (lstat(path, &st) < 0)
 136                 return -1;
 137
 138         /* Make sure it is a "refs/.." symlink */
 139         if (S_ISLNK(st.st_mode)) {
 140                 len = readlink(path, buffer, sizeof(buffer)-1);
 141                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 142                         return 0;
 143                 return -1;
 144         }
 145
 146         /*
 147          * Anything else, just open it and try to see if it is a symbolic ref.
 148          */
 149         fd = open(path, O_RDONLY);
 150         if (fd < 0)
 151                 return -1;
 152         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 153         close(fd);
 154
 155         /*
 156          * Is it a symbolic ref?
 157          */
 158         if (len < 4)
 159                 return -1;
 160         if (!memcmp("ref:", buffer, 4)) {
 161                 buf = buffer + 4;
 162                 len -= 4;
 163                 while (len && isspace(*buf))
 164                         buf++, len--;
 165                 if (len >= 5 && !memcmp("refs/", buf, 5))
 166                         return 0;
 167         }
 168
 169         /*
 170          * Is this a detached HEAD?
 171          */
 172         if (!get_sha1_hex(buffer, sha1))
 173                 return 0;
 174
 175         return -1;
 176 }
 177
 178 static char *user_path(char *buf, char *path, int sz)
 179 {
 180         struct passwd *pw;
 181         char *slash;
 182         int len, baselen;
 183
 184         if (!path || path[0] != '~')
 185                 return NULL;
 186         path++;
 187         slash = strchr(path, '/');
 188         if (path[0] == '/' || !path[0]) {
 189                 pw = getpwuid(getuid());
 190         }
 191         else {
 192                 if (slash) {
 193                         *slash = 0;
 194                         pw = getpwnam(path);
 195                         *slash = '/';
 196                 }
 197                 else
 198                         pw = getpwnam(path);
 199         }
 200         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 201                 return NULL;
 202         baselen = strlen(pw->pw_dir);
 203         memcpy(buf, pw->pw_dir, baselen);
 204         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 205                 buf[baselen-1] = 0;
 206                 baselen--;
 207         }
 208         if (slash && slash[1]) {
 209                 len = strlen(slash);
 210                 if (sz <= baselen + len)
 211                         return NULL;
 212                 memcpy(buf + baselen, slash, len + 1);
 213         }
 214         return buf;
 215 }
 216
 217 /*
 218  * First, one directory to try is determined by the following algorithm.
 219  *
 220  * (0) If "strict" is given, the path is used as given and no DWIM is
 221  *     done. Otherwise:
 222  * (1) "~/path" to mean path under the running user's home directory;
 223  * (2) "~user/path" to mean path under named user's home directory;
 224  * (3) "relative/path" to mean cwd relative directory; or
 225  * (4) "/absolute/path" to mean absolute directory.
 226  *
 227  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 228  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 229  * what we try.
 230  *
 231  * Second, we try chdir() to that.  Upon failure, we return NULL.
 232  *
 233  * Then, we try if the current directory is a valid git repository.
 234  * Upon failure, we return NULL.
 235  *
 236  * If all goes well, we return the directory we used to chdir() (but
 237  * before ~user is expanded), avoiding getcwd() resolving symbolic
 238  * links.  User relative paths are also returned as they are given,
 239  * except DWIM suffixing.
 240  */
 241 char *enter_repo(char *path, int strict)
 242 {
 243         static char used_path[PATH_MAX];
 244         static char validated_path[PATH_MAX];
 245
 246         if (!path)
 247                 return NULL;
 248
 249         if (!strict) {
 250                 static const char *suffix[] = {
 251                         ".git/.git", "/.git", ".git", "", NULL,
 252                 };
 253                 int len = strlen(path);
 254                 int i;
 255                 while ((1 < len) && (path[len-1] == '/')) {
 256                         path[len-1] = 0;
 257                         len--;
 258                 }
 259                 if (PATH_MAX <= len)
 260                         return NULL;
 261                 if (path[0] == '~') {
 262                         if (!user_path(used_path, path, PATH_MAX))
 263                                 return NULL;
 264                         strcpy(validated_path, path);
 265                         path = used_path;
 266                 }
 267                 else if (PATH_MAX - 10 < len)
 268                         return NULL;
 269                 else {
 270                         path = strcpy(used_path, path);
 271                         strcpy(validated_path, path);
 272                 }
 273                 len = strlen(path);
 274                 for (i = 0; suffix[i]; i++) {
 275                         strcpy(path + len, suffix[i]);
 276                         if (!access(path, F_OK)) {
 277                                 strcat(validated_path, suffix[i]);
 278                                 break;
 279                         }
 280                 }
 281                 if (!suffix[i] || chdir(path))
 282                         return NULL;
 283                 path = validated_path;
 284         }
 285         else if (chdir(path))
 286                 return NULL;
 287
 288         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 289             validate_headref("HEAD") == 0) {
 290                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 291                 check_repository_format();
 292                 return path;
 293         }
 294
 295         return NULL;
 296 }
 297
 298 int adjust_shared_perm(const char *path)
 299 {
 300         struct stat st;
 301         int mode;
 302
 303         if (!shared_repository)
 304                 return 0;
 305         if (lstat(path, &st) < 0)
 306                 return -1;
 307         mode = st.st_mode;
 308
 309         if (shared_repository) {
 310                 int tweak = shared_repository;
 311                 if (!(mode & S_IWUSR))
 312                         tweak &= ~0222;
 313                 mode |= tweak;
 314         } else {
 315                 /* Preserve old PERM_UMASK behaviour */
 316                 if (mode & S_IWUSR)
 317                         mode |= S_IWGRP;
 318         }
 319
 320         if (S_ISDIR(mode)) {
 321                 mode |= FORCE_DIR_SET_GID;
 322
 323                 /* Copy read bits to execute bits */
 324                 mode |= (shared_repository & 0444) >> 2;
 325         }
 326
 327         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 328                 return -2;
 329         return 0;
 330 }
 331
 332 const char *make_relative_path(const char *abs, const char *base)
 333 {
 334         static char buf[PATH_MAX + 1];
 335         int baselen;
 336         if (!base)
 337                 return abs;
 338         baselen = strlen(base);
 339         if (prefixcmp(abs, base))
 340                 return abs;
 341         if (abs[baselen] == '/')
 342                 baselen++;
 343         else if (base[baselen - 1] != '/')
 344                 return abs;
 345         strcpy(buf, abs + baselen);
 346         return buf;
 347 }
 348
 349 /*
 350  * path = absolute path
 351  * buf = buffer of at least max(2, strlen(path)+1) bytes
 352  * It is okay if buf == path, but they should not overlap otherwise.
 353  *
 354  * Performs the following normalizations on path, storing the result in buf:
 355  * - Removes trailing slashes.
 356  * - Removes empty components.
 357  * - Removes "." components.
 358  * - Removes ".." components, and the components the precede them.
 359  * "" and paths that contain only slashes are normalized to "/".
 360  * Returns the length of the output.
 361  *
 362  * Note that this function is purely textual.  It does not follow symlinks,
 363  * verify the existence of the path, or make any system calls.
 364  */
 365 int normalize_absolute_path(char *buf, const char *path)
 366 {
 367         const char *comp_start = path, *comp_end = path;
 368         char *dst = buf;
 369         int comp_len;
 370         assert(buf);
 371         assert(path);
 372
 373         while (*comp_start) {
 374                 assert(*comp_start == '/');
 375                 while (*++comp_end && *comp_end != '/')
 376                         ; /* nothing */
 377                 comp_len = comp_end - comp_start;
 378
 379                 if (!strncmp("/",  comp_start, comp_len) ||
 380                     !strncmp("/.", comp_start, comp_len))
 381                         goto next;
 382
 383                 if (!strncmp("/..", comp_start, comp_len)) {
 384                         while (dst > buf && *--dst != '/')
 385                                 ; /* nothing */
 386                         goto next;
 387                 }
 388
 389                 memcpy(dst, comp_start, comp_len);
 390                 dst += comp_len;
 391         next:
 392                 comp_start = comp_end;
 393         }
 394
 395         if (dst == buf)
 396                 *dst++ = '/';
 397
 398         *dst = '\0';
 399         return dst - buf;
 400 }
 401
 402 /*
 403  * path = Canonical absolute path
 404  * prefix_list = Colon-separated list of absolute paths
 405  *
 406  * Determines, for each path in prefix_list, whether the "prefix" really
 407  * is an ancestor directory of path.  Returns the length of the longest
 408  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 409  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 410  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 411  * are not considered to be their own ancestors.  path must be in a
 412  * canonical form: empty components, or "." or ".." components are not
 413  * allowed.  prefix_list may be null, which is like "".
 414  */
 415 int longest_ancestor_length(const char *path, const char *prefix_list)
 416 {
 417         char buf[PATH_MAX+1];
 418         const char *ceil, *colon;
 419         int len, max_len = -1;
 420
 421         if (prefix_list == NULL || !strcmp(path, "/"))
 422                 return -1;
 423
 424         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 425                 for (colon = ceil; *colon && *colon != ':'; colon++);
 426                 len = colon - ceil;
 427                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 428                         continue;
 429                 strlcpy(buf, ceil, len+1);
 430                 len = normalize_absolute_path(buf, buf);
 431                 /* Strip "trailing slashes" from "/". */
 432                 if (len == 1)
 433                         len = 0;
 434
 435                 if (!strncmp(path, buf, len) &&
 436                     path[len] == '/' &&
 437                     len > max_len) {
 438                         max_len = len;
 439                 }
 440         }
 441
 442         return max_len;
 443 }