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 *mkpath(const char *fmt, ...)
  36 {
  37         va_list args;
  38         unsigned len;
  39         char *pathname = get_pathname();
  40
  41         va_start(args, fmt);
  42         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  43         va_end(args);
  44         if (len >= PATH_MAX)
  45                 return bad_path;
  46         return cleanup_path(pathname);
  47 }
  48
  49 char *git_path(const char *fmt, ...)
  50 {
  51         const char *git_dir = get_git_dir();
  52         char *pathname = get_pathname();
  53         va_list args;
  54         unsigned len;
  55
  56         len = strlen(git_dir);
  57         if (len > PATH_MAX-100)
  58                 return bad_path;
  59         memcpy(pathname, git_dir, len);
  60         if (len && git_dir[len-1] != '/')
  61                 pathname[len++] = '/';
  62         va_start(args, fmt);
  63         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
  64         va_end(args);
  65         if (len >= PATH_MAX)
  66                 return bad_path;
  67         return cleanup_path(pathname);
  68 }
  69
  70
  71 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
  72 int git_mkstemp(char *path, size_t len, const char *template)
  73 {
  74         const char *tmp;
  75         size_t n;
  76
  77         tmp = getenv("TMPDIR");
  78         if (!tmp)
  79                 tmp = "/tmp";
  80         n = snprintf(path, len, "%s/%s", tmp, template);
  81         if (len <= n) {
  82                 errno = ENAMETOOLONG;
  83                 return -1;
  84         }
  85         return mkstemp(path);
  86 }
  87
  88
  89 int validate_headref(const char *path)
  90 {
  91         struct stat st;
  92         char *buf, buffer[256];
  93         unsigned char sha1[20];
  94         int fd;
  95         ssize_t len;
  96
  97         if (lstat(path, &st) < 0)
  98                 return -1;
  99
 100         /* Make sure it is a "refs/.." symlink */
 101         if (S_ISLNK(st.st_mode)) {
 102                 len = readlink(path, buffer, sizeof(buffer)-1);
 103                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 104                         return 0;
 105                 return -1;
 106         }
 107
 108         /*
 109          * Anything else, just open it and try to see if it is a symbolic ref.
 110          */
 111         fd = open(path, O_RDONLY);
 112         if (fd < 0)
 113                 return -1;
 114         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 115         close(fd);
 116
 117         /*
 118          * Is it a symbolic ref?
 119          */
 120         if (len < 4)
 121                 return -1;
 122         if (!memcmp("ref:", buffer, 4)) {
 123                 buf = buffer + 4;
 124                 len -= 4;
 125                 while (len && isspace(*buf))
 126                         buf++, len--;
 127                 if (len >= 5 && !memcmp("refs/", buf, 5))
 128                         return 0;
 129         }
 130
 131         /*
 132          * Is this a detached HEAD?
 133          */
 134         if (!get_sha1_hex(buffer, sha1))
 135                 return 0;
 136
 137         return -1;
 138 }
 139
 140 static char *user_path(char *buf, char *path, int sz)
 141 {
 142         struct passwd *pw;
 143         char *slash;
 144         int len, baselen;
 145
 146         if (!path || path[0] != '~')
 147                 return NULL;
 148         path++;
 149         slash = strchr(path, '/');
 150         if (path[0] == '/' || !path[0]) {
 151                 pw = getpwuid(getuid());
 152         }
 153         else {
 154                 if (slash) {
 155                         *slash = 0;
 156                         pw = getpwnam(path);
 157                         *slash = '/';
 158                 }
 159                 else
 160                         pw = getpwnam(path);
 161         }
 162         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 163                 return NULL;
 164         baselen = strlen(pw->pw_dir);
 165         memcpy(buf, pw->pw_dir, baselen);
 166         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 167                 buf[baselen-1] = 0;
 168                 baselen--;
 169         }
 170         if (slash && slash[1]) {
 171                 len = strlen(slash);
 172                 if (sz <= baselen + len)
 173                         return NULL;
 174                 memcpy(buf + baselen, slash, len + 1);
 175         }
 176         return buf;
 177 }
 178
 179 /*
 180  * First, one directory to try is determined by the following algorithm.
 181  *
 182  * (0) If "strict" is given, the path is used as given and no DWIM is
 183  *     done. Otherwise:
 184  * (1) "~/path" to mean path under the running user's home directory;
 185  * (2) "~user/path" to mean path under named user's home directory;
 186  * (3) "relative/path" to mean cwd relative directory; or
 187  * (4) "/absolute/path" to mean absolute directory.
 188  *
 189  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 190  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 191  * what we try.
 192  *
 193  * Second, we try chdir() to that.  Upon failure, we return NULL.
 194  *
 195  * Then, we try if the current directory is a valid git repository.
 196  * Upon failure, we return NULL.
 197  *
 198  * If all goes well, we return the directory we used to chdir() (but
 199  * before ~user is expanded), avoiding getcwd() resolving symbolic
 200  * links.  User relative paths are also returned as they are given,
 201  * except DWIM suffixing.
 202  */
 203 char *enter_repo(char *path, int strict)
 204 {
 205         static char used_path[PATH_MAX];
 206         static char validated_path[PATH_MAX];
 207
 208         if (!path)
 209                 return NULL;
 210
 211         if (!strict) {
 212                 static const char *suffix[] = {
 213                         ".git/.git", "/.git", ".git", "", NULL,
 214                 };
 215                 int len = strlen(path);
 216                 int i;
 217                 while ((1 < len) && (path[len-1] == '/')) {
 218                         path[len-1] = 0;
 219                         len--;
 220                 }
 221                 if (PATH_MAX <= len)
 222                         return NULL;
 223                 if (path[0] == '~') {
 224                         if (!user_path(used_path, path, PATH_MAX))
 225                                 return NULL;
 226                         strcpy(validated_path, path);
 227                         path = used_path;
 228                 }
 229                 else if (PATH_MAX - 10 < len)
 230                         return NULL;
 231                 else {
 232                         path = strcpy(used_path, path);
 233                         strcpy(validated_path, path);
 234                 }
 235                 len = strlen(path);
 236                 for (i = 0; suffix[i]; i++) {
 237                         strcpy(path + len, suffix[i]);
 238                         if (!access(path, F_OK)) {
 239                                 strcat(validated_path, suffix[i]);
 240                                 break;
 241                         }
 242                 }
 243                 if (!suffix[i] || chdir(path))
 244                         return NULL;
 245                 path = validated_path;
 246         }
 247         else if (chdir(path))
 248                 return NULL;
 249
 250         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 251             validate_headref("HEAD") == 0) {
 252                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 253                 check_repository_format();
 254                 return path;
 255         }
 256
 257         return NULL;
 258 }
 259
 260 int adjust_shared_perm(const char *path)
 261 {
 262         struct stat st;
 263         int mode;
 264
 265         if (!shared_repository)
 266                 return 0;
 267         if (lstat(path, &st) < 0)
 268                 return -1;
 269         mode = st.st_mode;
 270
 271         if (shared_repository) {
 272                 int tweak = shared_repository;
 273                 if (!(mode & S_IWUSR))
 274                         tweak &= ~0222;
 275                 mode |= tweak;
 276         } else {
 277                 /* Preserve old PERM_UMASK behaviour */
 278                 if (mode & S_IWUSR)
 279                         mode |= S_IWGRP;
 280         }
 281
 282         if (S_ISDIR(mode)) {
 283                 mode |= FORCE_DIR_SET_GID;
 284
 285                 /* Copy read bits to execute bits */
 286                 mode |= (shared_repository & 0444) >> 2;
 287         }
 288
 289         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 290                 return -2;
 291         return 0;
 292 }
 293
 294 const char *make_relative_path(const char *abs, const char *base)
 295 {
 296         static char buf[PATH_MAX + 1];
 297         int baselen;
 298         if (!base)
 299                 return abs;
 300         baselen = strlen(base);
 301         if (prefixcmp(abs, base))
 302                 return abs;
 303         if (abs[baselen] == '/')
 304                 baselen++;
 305         else if (base[baselen - 1] != '/')
 306                 return abs;
 307         strcpy(buf, abs + baselen);
 308         return buf;
 309 }
 310
 311 /*
 312  * path = absolute path
 313  * buf = buffer of at least max(2, strlen(path)+1) bytes
 314  * It is okay if buf == path, but they should not overlap otherwise.
 315  *
 316  * Performs the following normalizations on path, storing the result in buf:
 317  * - Removes trailing slashes.
 318  * - Removes empty components.
 319  * - Removes "." components.
 320  * - Removes ".." components, and the components the precede them.
 321  * "" and paths that contain only slashes are normalized to "/".
 322  * Returns the length of the output.
 323  *
 324  * Note that this function is purely textual.  It does not follow symlinks,
 325  * verify the existence of the path, or make any system calls.
 326  */
 327 int normalize_absolute_path(char *buf, const char *path)
 328 {
 329         const char *comp_start = path, *comp_end = path;
 330         char *dst = buf;
 331         int comp_len;
 332         assert(buf);
 333         assert(path);
 334
 335         while (*comp_start) {
 336                 assert(*comp_start == '/');
 337                 while (*++comp_end && *comp_end != '/')
 338                         ; /* nothing */
 339                 comp_len = comp_end - comp_start;
 340
 341                 if (!strncmp("/",  comp_start, comp_len) ||
 342                     !strncmp("/.", comp_start, comp_len))
 343                         goto next;
 344
 345                 if (!strncmp("/..", comp_start, comp_len)) {
 346                         while (dst > buf && *--dst != '/')
 347                                 ; /* nothing */
 348                         goto next;
 349                 }
 350
 351                 memcpy(dst, comp_start, comp_len);
 352                 dst += comp_len;
 353         next:
 354                 comp_start = comp_end;
 355         }
 356
 357         if (dst == buf)
 358                 *dst++ = '/';
 359
 360         *dst = '\0';
 361         return dst - buf;
 362 }
 363
 364 /*
 365  * path = Canonical absolute path
 366  * prefix_list = Colon-separated list of absolute paths
 367  *
 368  * Determines, for each path in prefix_list, whether the "prefix" really
 369  * is an ancestor directory of path.  Returns the length of the longest
 370  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 371  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 372  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 373  * are not considered to be their own ancestors.  path must be in a
 374  * canonical form: empty components, or "." or ".." components are not
 375  * allowed.  prefix_list may be null, which is like "".
 376  */
 377 int longest_ancestor_length(const char *path, const char *prefix_list)
 378 {
 379         char buf[PATH_MAX+1];
 380         const char *ceil, *colon;
 381         int len, max_len = -1;
 382
 383         if (prefix_list == NULL || !strcmp(path, "/"))
 384                 return -1;
 385
 386         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 387                 for (colon = ceil; *colon && *colon != ':'; colon++);
 388                 len = colon - ceil;
 389                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 390                         continue;
 391                 strlcpy(buf, ceil, len+1);
 392                 len = normalize_absolute_path(buf, buf);
 393                 /* Strip "trailing slashes" from "/". */
 394                 if (len == 1)
 395                         len = 0;
 396
 397                 if (!strncmp(path, buf, len) &&
 398                     path[len] == '/' &&
 399                     len > max_len) {
 400                         max_len = len;
 401                 }
 402         }
 403
 404         return max_len;
 405 }