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 *mkpath(const char *fmt, ...)
  51 {
  52         va_list args;
  53         unsigned len;
  54         char *pathname = get_pathname();
  55
  56         va_start(args, fmt);
  57         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  58         va_end(args);
  59         if (len >= PATH_MAX)
  60                 return bad_path;
  61         return cleanup_path(pathname);
  62 }
  63
  64 char *git_path(const char *fmt, ...)
  65 {
  66         const char *git_dir = get_git_dir();
  67         char *pathname = get_pathname();
  68         va_list args;
  69         unsigned len;
  70
  71         len = strlen(git_dir);
  72         if (len > PATH_MAX-100)
  73                 return bad_path;
  74         memcpy(pathname, git_dir, len);
  75         if (len && git_dir[len-1] != '/')
  76                 pathname[len++] = '/';
  77         va_start(args, fmt);
  78         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
  79         va_end(args);
  80         if (len >= PATH_MAX)
  81                 return bad_path;
  82         return cleanup_path(pathname);
  83 }
  84
  85
  86 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
  87 int git_mkstemp(char *path, size_t len, const char *template)
  88 {
  89         const char *tmp;
  90         size_t n;
  91
  92         tmp = getenv("TMPDIR");
  93         if (!tmp)
  94                 tmp = "/tmp";
  95         n = snprintf(path, len, "%s/%s", tmp, template);
  96         if (len <= n) {
  97                 errno = ENAMETOOLONG;
  98                 return -1;
  99         }
 100         return mkstemp(path);
 101 }
 102
 103
 104 int validate_headref(const char *path)
 105 {
 106         struct stat st;
 107         char *buf, buffer[256];
 108         unsigned char sha1[20];
 109         int fd;
 110         ssize_t len;
 111
 112         if (lstat(path, &st) < 0)
 113                 return -1;
 114
 115         /* Make sure it is a "refs/.." symlink */
 116         if (S_ISLNK(st.st_mode)) {
 117                 len = readlink(path, buffer, sizeof(buffer)-1);
 118                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 119                         return 0;
 120                 return -1;
 121         }
 122
 123         /*
 124          * Anything else, just open it and try to see if it is a symbolic ref.
 125          */
 126         fd = open(path, O_RDONLY);
 127         if (fd < 0)
 128                 return -1;
 129         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 130         close(fd);
 131
 132         /*
 133          * Is it a symbolic ref?
 134          */
 135         if (len < 4)
 136                 return -1;
 137         if (!memcmp("ref:", buffer, 4)) {
 138                 buf = buffer + 4;
 139                 len -= 4;
 140                 while (len && isspace(*buf))
 141                         buf++, len--;
 142                 if (len >= 5 && !memcmp("refs/", buf, 5))
 143                         return 0;
 144         }
 145
 146         /*
 147          * Is this a detached HEAD?
 148          */
 149         if (!get_sha1_hex(buffer, sha1))
 150                 return 0;
 151
 152         return -1;
 153 }
 154
 155 static char *user_path(char *buf, char *path, int sz)
 156 {
 157         struct passwd *pw;
 158         char *slash;
 159         int len, baselen;
 160
 161         if (!path || path[0] != '~')
 162                 return NULL;
 163         path++;
 164         slash = strchr(path, '/');
 165         if (path[0] == '/' || !path[0]) {
 166                 pw = getpwuid(getuid());
 167         }
 168         else {
 169                 if (slash) {
 170                         *slash = 0;
 171                         pw = getpwnam(path);
 172                         *slash = '/';
 173                 }
 174                 else
 175                         pw = getpwnam(path);
 176         }
 177         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 178                 return NULL;
 179         baselen = strlen(pw->pw_dir);
 180         memcpy(buf, pw->pw_dir, baselen);
 181         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 182                 buf[baselen-1] = 0;
 183                 baselen--;
 184         }
 185         if (slash && slash[1]) {
 186                 len = strlen(slash);
 187                 if (sz <= baselen + len)
 188                         return NULL;
 189                 memcpy(buf + baselen, slash, len + 1);
 190         }
 191         return buf;
 192 }
 193
 194 /*
 195  * First, one directory to try is determined by the following algorithm.
 196  *
 197  * (0) If "strict" is given, the path is used as given and no DWIM is
 198  *     done. Otherwise:
 199  * (1) "~/path" to mean path under the running user's home directory;
 200  * (2) "~user/path" to mean path under named user's home directory;
 201  * (3) "relative/path" to mean cwd relative directory; or
 202  * (4) "/absolute/path" to mean absolute directory.
 203  *
 204  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 205  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 206  * what we try.
 207  *
 208  * Second, we try chdir() to that.  Upon failure, we return NULL.
 209  *
 210  * Then, we try if the current directory is a valid git repository.
 211  * Upon failure, we return NULL.
 212  *
 213  * If all goes well, we return the directory we used to chdir() (but
 214  * before ~user is expanded), avoiding getcwd() resolving symbolic
 215  * links.  User relative paths are also returned as they are given,
 216  * except DWIM suffixing.
 217  */
 218 char *enter_repo(char *path, int strict)
 219 {
 220         static char used_path[PATH_MAX];
 221         static char validated_path[PATH_MAX];
 222
 223         if (!path)
 224                 return NULL;
 225
 226         if (!strict) {
 227                 static const char *suffix[] = {
 228                         ".git/.git", "/.git", ".git", "", NULL,
 229                 };
 230                 int len = strlen(path);
 231                 int i;
 232                 while ((1 < len) && (path[len-1] == '/')) {
 233                         path[len-1] = 0;
 234                         len--;
 235                 }
 236                 if (PATH_MAX <= len)
 237                         return NULL;
 238                 if (path[0] == '~') {
 239                         if (!user_path(used_path, path, PATH_MAX))
 240                                 return NULL;
 241                         strcpy(validated_path, path);
 242                         path = used_path;
 243                 }
 244                 else if (PATH_MAX - 10 < len)
 245                         return NULL;
 246                 else {
 247                         path = strcpy(used_path, path);
 248                         strcpy(validated_path, path);
 249                 }
 250                 len = strlen(path);
 251                 for (i = 0; suffix[i]; i++) {
 252                         strcpy(path + len, suffix[i]);
 253                         if (!access(path, F_OK)) {
 254                                 strcat(validated_path, suffix[i]);
 255                                 break;
 256                         }
 257                 }
 258                 if (!suffix[i] || chdir(path))
 259                         return NULL;
 260                 path = validated_path;
 261         }
 262         else if (chdir(path))
 263                 return NULL;
 264
 265         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 266             validate_headref("HEAD") == 0) {
 267                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 268                 check_repository_format();
 269                 return path;
 270         }
 271
 272         return NULL;
 273 }
 274
 275 int adjust_shared_perm(const char *path)
 276 {
 277         struct stat st;
 278         int mode;
 279
 280         if (!shared_repository)
 281                 return 0;
 282         if (lstat(path, &st) < 0)
 283                 return -1;
 284         mode = st.st_mode;
 285
 286         if (shared_repository) {
 287                 int tweak = shared_repository;
 288                 if (!(mode & S_IWUSR))
 289                         tweak &= ~0222;
 290                 mode |= tweak;
 291         } else {
 292                 /* Preserve old PERM_UMASK behaviour */
 293                 if (mode & S_IWUSR)
 294                         mode |= S_IWGRP;
 295         }
 296
 297         if (S_ISDIR(mode)) {
 298                 mode |= FORCE_DIR_SET_GID;
 299
 300                 /* Copy read bits to execute bits */
 301                 mode |= (shared_repository & 0444) >> 2;
 302         }
 303
 304         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 305                 return -2;
 306         return 0;
 307 }
 308
 309 const char *make_relative_path(const char *abs, const char *base)
 310 {
 311         static char buf[PATH_MAX + 1];
 312         int baselen;
 313         if (!base)
 314                 return abs;
 315         baselen = strlen(base);
 316         if (prefixcmp(abs, base))
 317                 return abs;
 318         if (abs[baselen] == '/')
 319                 baselen++;
 320         else if (base[baselen - 1] != '/')
 321                 return abs;
 322         strcpy(buf, abs + baselen);
 323         return buf;
 324 }
 325
 326 /*
 327  * path = absolute path
 328  * buf = buffer of at least max(2, strlen(path)+1) bytes
 329  * It is okay if buf == path, but they should not overlap otherwise.
 330  *
 331  * Performs the following normalizations on path, storing the result in buf:
 332  * - Removes trailing slashes.
 333  * - Removes empty components.
 334  * - Removes "." components.
 335  * - Removes ".." components, and the components the precede them.
 336  * "" and paths that contain only slashes are normalized to "/".
 337  * Returns the length of the output.
 338  *
 339  * Note that this function is purely textual.  It does not follow symlinks,
 340  * verify the existence of the path, or make any system calls.
 341  */
 342 int normalize_absolute_path(char *buf, const char *path)
 343 {
 344         const char *comp_start = path, *comp_end = path;
 345         char *dst = buf;
 346         int comp_len;
 347         assert(buf);
 348         assert(path);
 349
 350         while (*comp_start) {
 351                 assert(*comp_start == '/');
 352                 while (*++comp_end && *comp_end != '/')
 353                         ; /* nothing */
 354                 comp_len = comp_end - comp_start;
 355
 356                 if (!strncmp("/",  comp_start, comp_len) ||
 357                     !strncmp("/.", comp_start, comp_len))
 358                         goto next;
 359
 360                 if (!strncmp("/..", comp_start, comp_len)) {
 361                         while (dst > buf && *--dst != '/')
 362                                 ; /* nothing */
 363                         goto next;
 364                 }
 365
 366                 memcpy(dst, comp_start, comp_len);
 367                 dst += comp_len;
 368         next:
 369                 comp_start = comp_end;
 370         }
 371
 372         if (dst == buf)
 373                 *dst++ = '/';
 374
 375         *dst = '\0';
 376         return dst - buf;
 377 }
 378
 379 /*
 380  * path = Canonical absolute path
 381  * prefix_list = Colon-separated list of absolute paths
 382  *
 383  * Determines, for each path in prefix_list, whether the "prefix" really
 384  * is an ancestor directory of path.  Returns the length of the longest
 385  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 386  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 387  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 388  * are not considered to be their own ancestors.  path must be in a
 389  * canonical form: empty components, or "." or ".." components are not
 390  * allowed.  prefix_list may be null, which is like "".
 391  */
 392 int longest_ancestor_length(const char *path, const char *prefix_list)
 393 {
 394         char buf[PATH_MAX+1];
 395         const char *ceil, *colon;
 396         int len, max_len = -1;
 397
 398         if (prefix_list == NULL || !strcmp(path, "/"))
 399                 return -1;
 400
 401         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 402                 for (colon = ceil; *colon && *colon != ':'; colon++);
 403                 len = colon - ceil;
 404                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 405                         continue;
 406                 strlcpy(buf, ceil, len+1);
 407                 len = normalize_absolute_path(buf, buf);
 408                 /* Strip "trailing slashes" from "/". */
 409                 if (len == 1)
 410                         len = 0;
 411
 412                 if (!strncmp(path, buf, len) &&
 413                     path[len] == '/' &&
 414                     len > max_len) {
 415                         max_len = len;
 416                 }
 417         }
 418
 419         return max_len;
 420 }