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                 strlcpy(buf, bad_path, n);
  45                 return buf;
  46         }
  47         return cleanup_path(buf);
  48 }
  49
  50 static char *git_vsnpath(char *buf, size_t n, const char *fmt, va_list args)
  51 {
  52         const char *git_dir = get_git_dir();
  53         size_t len;
  54
  55         len = strlen(git_dir);
  56         if (n < len + 1)
  57                 goto bad;
  58         memcpy(buf, git_dir, len);
  59         if (len && !is_dir_sep(git_dir[len-1]))
  60                 buf[len++] = '/';
  61         len += vsnprintf(buf + len, n - len, fmt, args);
  62         if (len >= n)
  63                 goto bad;
  64         return cleanup_path(buf);
  65 bad:
  66         strlcpy(buf, bad_path, n);
  67         return buf;
  68 }
  69
  70 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
  71 {
  72         va_list args;
  73         va_start(args, fmt);
  74         (void)git_vsnpath(buf, n, fmt, args);
  75         va_end(args);
  76         return buf;
  77 }
  78
  79 char *git_pathdup(const char *fmt, ...)
  80 {
  81         char path[PATH_MAX];
  82         va_list args;
  83         va_start(args, fmt);
  84         (void)git_vsnpath(path, sizeof(path), fmt, args);
  85         va_end(args);
  86         return xstrdup(path);
  87 }
  88
  89 char *mkpath(const char *fmt, ...)
  90 {
  91         va_list args;
  92         unsigned len;
  93         char *pathname = get_pathname();
  94
  95         va_start(args, fmt);
  96         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  97         va_end(args);
  98         if (len >= PATH_MAX)
  99                 return bad_path;
 100         return cleanup_path(pathname);
 101 }
 102
 103 char *git_path(const char *fmt, ...)
 104 {
 105         const char *git_dir = get_git_dir();
 106         char *pathname = get_pathname();
 107         va_list args;
 108         unsigned len;
 109
 110         len = strlen(git_dir);
 111         if (len > PATH_MAX-100)
 112                 return bad_path;
 113         memcpy(pathname, git_dir, len);
 114         if (len && git_dir[len-1] != '/')
 115                 pathname[len++] = '/';
 116         va_start(args, fmt);
 117         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
 118         va_end(args);
 119         if (len >= PATH_MAX)
 120                 return bad_path;
 121         return cleanup_path(pathname);
 122 }
 123
 124
 125 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
 126 int git_mkstemp(char *path, size_t len, const char *template)
 127 {
 128         const char *tmp;
 129         size_t n;
 130
 131         tmp = getenv("TMPDIR");
 132         if (!tmp)
 133                 tmp = "/tmp";
 134         n = snprintf(path, len, "%s/%s", tmp, template);
 135         if (len <= n) {
 136                 errno = ENAMETOOLONG;
 137                 return -1;
 138         }
 139         return mkstemp(path);
 140 }
 141
 142
 143 int validate_headref(const char *path)
 144 {
 145         struct stat st;
 146         char *buf, buffer[256];
 147         unsigned char sha1[20];
 148         int fd;
 149         ssize_t len;
 150
 151         if (lstat(path, &st) < 0)
 152                 return -1;
 153
 154         /* Make sure it is a "refs/.." symlink */
 155         if (S_ISLNK(st.st_mode)) {
 156                 len = readlink(path, buffer, sizeof(buffer)-1);
 157                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 158                         return 0;
 159                 return -1;
 160         }
 161
 162         /*
 163          * Anything else, just open it and try to see if it is a symbolic ref.
 164          */
 165         fd = open(path, O_RDONLY);
 166         if (fd < 0)
 167                 return -1;
 168         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 169         close(fd);
 170
 171         /*
 172          * Is it a symbolic ref?
 173          */
 174         if (len < 4)
 175                 return -1;
 176         if (!memcmp("ref:", buffer, 4)) {
 177                 buf = buffer + 4;
 178                 len -= 4;
 179                 while (len && isspace(*buf))
 180                         buf++, len--;
 181                 if (len >= 5 && !memcmp("refs/", buf, 5))
 182                         return 0;
 183         }
 184
 185         /*
 186          * Is this a detached HEAD?
 187          */
 188         if (!get_sha1_hex(buffer, sha1))
 189                 return 0;
 190
 191         return -1;
 192 }
 193
 194 static char *user_path(char *buf, char *path, int sz)
 195 {
 196         struct passwd *pw;
 197         char *slash;
 198         int len, baselen;
 199
 200         if (!path || path[0] != '~')
 201                 return NULL;
 202         path++;
 203         slash = strchr(path, '/');
 204         if (path[0] == '/' || !path[0]) {
 205                 pw = getpwuid(getuid());
 206         }
 207         else {
 208                 if (slash) {
 209                         *slash = 0;
 210                         pw = getpwnam(path);
 211                         *slash = '/';
 212                 }
 213                 else
 214                         pw = getpwnam(path);
 215         }
 216         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 217                 return NULL;
 218         baselen = strlen(pw->pw_dir);
 219         memcpy(buf, pw->pw_dir, baselen);
 220         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 221                 buf[baselen-1] = 0;
 222                 baselen--;
 223         }
 224         if (slash && slash[1]) {
 225                 len = strlen(slash);
 226                 if (sz <= baselen + len)
 227                         return NULL;
 228                 memcpy(buf + baselen, slash, len + 1);
 229         }
 230         return buf;
 231 }
 232
 233 /*
 234  * First, one directory to try is determined by the following algorithm.
 235  *
 236  * (0) If "strict" is given, the path is used as given and no DWIM is
 237  *     done. Otherwise:
 238  * (1) "~/path" to mean path under the running user's home directory;
 239  * (2) "~user/path" to mean path under named user's home directory;
 240  * (3) "relative/path" to mean cwd relative directory; or
 241  * (4) "/absolute/path" to mean absolute directory.
 242  *
 243  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 244  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 245  * what we try.
 246  *
 247  * Second, we try chdir() to that.  Upon failure, we return NULL.
 248  *
 249  * Then, we try if the current directory is a valid git repository.
 250  * Upon failure, we return NULL.
 251  *
 252  * If all goes well, we return the directory we used to chdir() (but
 253  * before ~user is expanded), avoiding getcwd() resolving symbolic
 254  * links.  User relative paths are also returned as they are given,
 255  * except DWIM suffixing.
 256  */
 257 char *enter_repo(char *path, int strict)
 258 {
 259         static char used_path[PATH_MAX];
 260         static char validated_path[PATH_MAX];
 261
 262         if (!path)
 263                 return NULL;
 264
 265         if (!strict) {
 266                 static const char *suffix[] = {
 267                         ".git/.git", "/.git", ".git", "", NULL,
 268                 };
 269                 int len = strlen(path);
 270                 int i;
 271                 while ((1 < len) && (path[len-1] == '/')) {
 272                         path[len-1] = 0;
 273                         len--;
 274                 }
 275                 if (PATH_MAX <= len)
 276                         return NULL;
 277                 if (path[0] == '~') {
 278                         if (!user_path(used_path, path, PATH_MAX))
 279                                 return NULL;
 280                         strcpy(validated_path, path);
 281                         path = used_path;
 282                 }
 283                 else if (PATH_MAX - 10 < len)
 284                         return NULL;
 285                 else {
 286                         path = strcpy(used_path, path);
 287                         strcpy(validated_path, path);
 288                 }
 289                 len = strlen(path);
 290                 for (i = 0; suffix[i]; i++) {
 291                         strcpy(path + len, suffix[i]);
 292                         if (!access(path, F_OK)) {
 293                                 strcat(validated_path, suffix[i]);
 294                                 break;
 295                         }
 296                 }
 297                 if (!suffix[i] || chdir(path))
 298                         return NULL;
 299                 path = validated_path;
 300         }
 301         else if (chdir(path))
 302                 return NULL;
 303
 304         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 305             validate_headref("HEAD") == 0) {
 306                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 307                 check_repository_format();
 308                 return path;
 309         }
 310
 311         return NULL;
 312 }
 313
 314 int adjust_shared_perm(const char *path)
 315 {
 316         struct stat st;
 317         int mode;
 318
 319         if (!shared_repository)
 320                 return 0;
 321         if (lstat(path, &st) < 0)
 322                 return -1;
 323         mode = st.st_mode;
 324
 325         if (shared_repository) {
 326                 int tweak = shared_repository;
 327                 if (!(mode & S_IWUSR))
 328                         tweak &= ~0222;
 329                 mode |= tweak;
 330         } else {
 331                 /* Preserve old PERM_UMASK behaviour */
 332                 if (mode & S_IWUSR)
 333                         mode |= S_IWGRP;
 334         }
 335
 336         if (S_ISDIR(mode)) {
 337                 mode |= FORCE_DIR_SET_GID;
 338
 339                 /* Copy read bits to execute bits */
 340                 mode |= (shared_repository & 0444) >> 2;
 341         }
 342
 343         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 344                 return -2;
 345         return 0;
 346 }
 347
 348 const char *make_relative_path(const char *abs, const char *base)
 349 {
 350         static char buf[PATH_MAX + 1];
 351         int baselen;
 352         if (!base)
 353                 return abs;
 354         baselen = strlen(base);
 355         if (prefixcmp(abs, base))
 356                 return abs;
 357         if (abs[baselen] == '/')
 358                 baselen++;
 359         else if (base[baselen - 1] != '/')
 360                 return abs;
 361         strcpy(buf, abs + baselen);
 362         return buf;
 363 }
 364
 365 /*
 366  * path = absolute path
 367  * buf = buffer of at least max(2, strlen(path)+1) bytes
 368  * It is okay if buf == path, but they should not overlap otherwise.
 369  *
 370  * Performs the following normalizations on path, storing the result in buf:
 371  * - Removes trailing slashes.
 372  * - Removes empty components.
 373  * - Removes "." components.
 374  * - Removes ".." components, and the components the precede them.
 375  * "" and paths that contain only slashes are normalized to "/".
 376  * Returns the length of the output.
 377  *
 378  * Note that this function is purely textual.  It does not follow symlinks,
 379  * verify the existence of the path, or make any system calls.
 380  */
 381 int normalize_absolute_path(char *buf, const char *path)
 382 {
 383         const char *comp_start = path, *comp_end = path;
 384         char *dst = buf;
 385         int comp_len;
 386         assert(buf);
 387         assert(path);
 388
 389         while (*comp_start) {
 390                 assert(*comp_start == '/');
 391                 while (*++comp_end && *comp_end != '/')
 392                         ; /* nothing */
 393                 comp_len = comp_end - comp_start;
 394
 395                 if (!strncmp("/",  comp_start, comp_len) ||
 396                     !strncmp("/.", comp_start, comp_len))
 397                         goto next;
 398
 399                 if (!strncmp("/..", comp_start, comp_len)) {
 400                         while (dst > buf && *--dst != '/')
 401                                 ; /* nothing */
 402                         goto next;
 403                 }
 404
 405                 memmove(dst, comp_start, comp_len);
 406                 dst += comp_len;
 407         next:
 408                 comp_start = comp_end;
 409         }
 410
 411         if (dst == buf)
 412                 *dst++ = '/';
 413
 414         *dst = '\0';
 415         return dst - buf;
 416 }
 417
 418 /*
 419  * path = Canonical absolute path
 420  * prefix_list = Colon-separated list of absolute paths
 421  *
 422  * Determines, for each path in prefix_list, whether the "prefix" really
 423  * is an ancestor directory of path.  Returns the length of the longest
 424  * ancestor directory, excluding any trailing slashes, or -1 if no prefix
 425  * is an ancestor.  (Note that this means 0 is returned if prefix_list is
 426  * "/".) "/foo" is not considered an ancestor of "/foobar".  Directories
 427  * are not considered to be their own ancestors.  path must be in a
 428  * canonical form: empty components, or "." or ".." components are not
 429  * allowed.  prefix_list may be null, which is like "".
 430  */
 431 int longest_ancestor_length(const char *path, const char *prefix_list)
 432 {
 433         char buf[PATH_MAX+1];
 434         const char *ceil, *colon;
 435         int len, max_len = -1;
 436
 437         if (prefix_list == NULL || !strcmp(path, "/"))
 438                 return -1;
 439
 440         for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
 441                 for (colon = ceil; *colon && *colon != ':'; colon++);
 442                 len = colon - ceil;
 443                 if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
 444                         continue;
 445                 strlcpy(buf, ceil, len+1);
 446                 len = normalize_absolute_path(buf, buf);
 447                 /* Strip "trailing slashes" from "/". */
 448                 if (len == 1)
 449                         len = 0;
 450
 451                 if (!strncmp(path, buf, len) &&
 452                     path[len] == '/' &&
 453                     len > max_len) {
 454                         max_len = len;
 455                 }
 456         }
 457
 458         return max_len;
 459 }