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 #ifdef __MINGW32__
  79         /* on Windows it is TMP and TEMP */
  80         if (!tmp)
  81             tmp = getenv("TMP");
  82         if (!tmp)
  83             tmp = getenv("TEMP");
  84 #endif
  85         if (!tmp)
  86                 tmp = "/tmp";
  87         n = snprintf(path, len, "%s/%s", tmp, template);
  88         if (len <= n) {
  89                 errno = ENAMETOOLONG;
  90                 return -1;
  91         }
  92         return mkstemp(path);
  93 }
  94
  95
  96 int validate_headref(const char *path)
  97 {
  98         struct stat st;
  99         char *buf, buffer[256];
 100         unsigned char sha1[20];
 101         int len, fd;
 102
 103         if (lstat(path, &st) < 0)
 104                 return -1;
 105
 106         /* Make sure it is a "refs/.." symlink */
 107         if (S_ISLNK(st.st_mode)) {
 108                 len = readlink(path, buffer, sizeof(buffer)-1);
 109                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 110                         return 0;
 111                 return -1;
 112         }
 113
 114         /*
 115          * Anything else, just open it and try to see if it is a symbolic ref.
 116          */
 117         fd = open(path, O_RDONLY);
 118         if (fd < 0)
 119                 return -1;
 120         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 121         close(fd);
 122
 123         /*
 124          * Is it a symbolic ref?
 125          */
 126         if (len < 4)
 127                 return -1;
 128         if (!memcmp("ref:", buffer, 4)) {
 129                 buf = buffer + 4;
 130                 len -= 4;
 131                 while (len && isspace(*buf))
 132                         buf++, len--;
 133                 if (len >= 5 && !memcmp("refs/", buf, 5))
 134                         return 0;
 135         }
 136
 137         /*
 138          * Is this a detached HEAD?
 139          */
 140         if (!get_sha1_hex(buffer, sha1))
 141                 return 0;
 142
 143         return -1;
 144 }
 145
 146 static char *user_path(char *buf, char *path, int sz)
 147 {
 148         struct passwd *pw;
 149         char *slash;
 150         int len, baselen;
 151
 152         if (!path || path[0] != '~')
 153                 return NULL;
 154         path++;
 155         slash = strchr(path, '/');
 156         if (path[0] == '/' || !path[0]) {
 157                 pw = getpwuid(getuid());
 158         }
 159         else {
 160                 if (slash) {
 161                         *slash = 0;
 162                         pw = getpwnam(path);
 163                         *slash = '/';
 164                 }
 165                 else
 166                         pw = getpwnam(path);
 167         }
 168         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 169                 return NULL;
 170         baselen = strlen(pw->pw_dir);
 171         memcpy(buf, pw->pw_dir, baselen);
 172         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 173                 buf[baselen-1] = 0;
 174                 baselen--;
 175         }
 176         if (slash && slash[1]) {
 177                 len = strlen(slash);
 178                 if (sz <= baselen + len)
 179                         return NULL;
 180                 memcpy(buf + baselen, slash, len + 1);
 181         }
 182         return buf;
 183 }
 184
 185 /*
 186  * First, one directory to try is determined by the following algorithm.
 187  *
 188  * (0) If "strict" is given, the path is used as given and no DWIM is
 189  *     done. Otherwise:
 190  * (1) "~/path" to mean path under the running user's home directory;
 191  * (2) "~user/path" to mean path under named user's home directory;
 192  * (3) "relative/path" to mean cwd relative directory; or
 193  * (4) "/absolute/path" to mean absolute directory.
 194  *
 195  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 196  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 197  * what we try.
 198  *
 199  * Second, we try chdir() to that.  Upon failure, we return NULL.
 200  *
 201  * Then, we try if the current directory is a valid git repository.
 202  * Upon failure, we return NULL.
 203  *
 204  * If all goes well, we return the directory we used to chdir() (but
 205  * before ~user is expanded), avoiding getcwd() resolving symbolic
 206  * links.  User relative paths are also returned as they are given,
 207  * except DWIM suffixing.
 208  */
 209 char *enter_repo(char *path, int strict)
 210 {
 211         static char used_path[PATH_MAX];
 212         static char validated_path[PATH_MAX];
 213
 214         if (!path)
 215                 return NULL;
 216
 217         if (!strict) {
 218                 static const char *suffix[] = {
 219                         ".git/.git", "/.git", ".git", "", NULL,
 220                 };
 221                 int len = strlen(path);
 222                 int i;
 223                 while ((1 < len) && (path[len-1] == '/')) {
 224                         path[len-1] = 0;
 225                         len--;
 226                 }
 227                 if (PATH_MAX <= len)
 228                         return NULL;
 229                 if (path[0] == '~') {
 230                         if (!user_path(used_path, path, PATH_MAX))
 231                                 return NULL;
 232                         strcpy(validated_path, path);
 233                         path = used_path;
 234                 }
 235                 else if (PATH_MAX - 10 < len)
 236                         return NULL;
 237                 else {
 238                         path = strcpy(used_path, path);
 239                         strcpy(validated_path, path);
 240                 }
 241                 len = strlen(path);
 242                 for (i = 0; suffix[i]; i++) {
 243                         strcpy(path + len, suffix[i]);
 244                         if (!access(path, F_OK)) {
 245                                 strcat(validated_path, suffix[i]);
 246                                 break;
 247                         }
 248                 }
 249                 if (!suffix[i] || chdir(path))
 250                         return NULL;
 251                 path = validated_path;
 252         }
 253         else if (chdir(path))
 254                 return NULL;
 255
 256         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 257             validate_headref("HEAD") == 0) {
 258                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 259                 check_repository_format();
 260                 return path;
 261         }
 262
 263         return NULL;
 264 }
 265
 266 int adjust_shared_perm(const char *path)
 267 {
 268         struct stat st;
 269         int mode;
 270
 271         if (!shared_repository)
 272                 return 0;
 273         if (lstat(path, &st) < 0)
 274                 return -1;
 275         mode = st.st_mode;
 276         if (mode & S_IRUSR)
 277                 mode |= (shared_repository == PERM_GROUP
 278                          ? S_IRGRP
 279                          : (shared_repository == PERM_EVERYBODY
 280                             ? (S_IRGRP|S_IROTH)
 281                             : 0));
 282
 283         if (mode & S_IWUSR)
 284                 mode |= S_IWGRP;
 285
 286         if (mode & S_IXUSR)
 287                 mode |= (shared_repository == PERM_GROUP
 288                          ? S_IXGRP
 289                          : (shared_repository == PERM_EVERYBODY
 290                             ? (S_IXGRP|S_IXOTH)
 291                             : 0));
 292         if (S_ISDIR(mode))
 293                 mode |= S_ISGID;
 294         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 295                 return -2;
 296         return 0;
 297 }
 298
 299 /* We allow "recursive" symbolic links. Only within reason, though. */
 300 #define MAXDEPTH 5
 301
 302 const char *make_absolute_path(const char *path)
 303 {
 304         static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];
 305         char cwd[1024] = "";
 306         int buf_index = 1, len;
 307
 308         int depth = MAXDEPTH;
 309         char *last_elem = NULL;
 310         struct stat st;
 311
 312         if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
 313                 die ("Too long path: %.*s", 60, path);
 314
 315         while (depth--) {
 316                 if (stat(buf, &st) || !S_ISDIR(st.st_mode)) {
 317                         char *last_slash = strrchr(buf, '/');
 318                         if (last_slash) {
 319                                 *last_slash = '\0';
 320                                 last_elem = xstrdup(last_slash + 1);
 321                         } else
 322                                 last_elem = xstrdup(buf);
 323                 }
 324
 325                 if (*buf) {
 326                         if (!*cwd && !getcwd(cwd, sizeof(cwd)))
 327                                 die ("Could not get current working directory");
 328
 329                         if (chdir(buf))
 330                                 die ("Could not switch to '%s'", buf);
 331                 }
 332                 if (!getcwd(buf, PATH_MAX))
 333                         die ("Could not get current working directory");
 334
 335                 if (last_elem) {
 336                         int len = strlen(buf);
 337                         if (len + strlen(last_elem) + 2 > PATH_MAX)
 338                                 die ("Too long path name: '%s/%s'",
 339                                                 buf, last_elem);
 340                         buf[len] = '/';
 341                         strcpy(buf + len + 1, last_elem);
 342                         free(last_elem);
 343                         last_elem = NULL;
 344                 }
 345
 346                 if (!lstat(buf, &st) && S_ISLNK(st.st_mode)) {
 347                         len = readlink(buf, next_buf, PATH_MAX);
 348                         if (len < 0)
 349                                 die ("Invalid symlink: %s", buf);
 350                         next_buf[len] = '\0';
 351                         buf = next_buf;
 352                         buf_index = 1 - buf_index;
 353                         next_buf = bufs[buf_index];
 354                 } else
 355                         break;
 356         }
 357
 358         if (*cwd && chdir(cwd))
 359                 die ("Could not change back to '%s'", cwd);
 360
 361         return buf;
 362 }