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 len, fd;
  95
  96         if (lstat(path, &st) < 0)
  97                 return -1;
  98
  99         /* Make sure it is a "refs/.." symlink */
 100         if (S_ISLNK(st.st_mode)) {
 101                 len = readlink(path, buffer, sizeof(buffer)-1);
 102                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 103                         return 0;
 104                 return -1;
 105         }
 106
 107         /*
 108          * Anything else, just open it and try to see if it is a symbolic ref.
 109          */
 110         fd = open(path, O_RDONLY);
 111         if (fd < 0)
 112                 return -1;
 113         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 114         close(fd);
 115
 116         /*
 117          * Is it a symbolic ref?
 118          */
 119         if (len < 4)
 120                 return -1;
 121         if (!memcmp("ref:", buffer, 4)) {
 122                 buf = buffer + 4;
 123                 len -= 4;
 124                 while (len && isspace(*buf))
 125                         buf++, len--;
 126                 if (len >= 5 && !memcmp("refs/", buf, 5))
 127                         return 0;
 128         }
 129
 130         /*
 131          * Is this a detached HEAD?
 132          */
 133         if (!get_sha1_hex(buffer, sha1))
 134                 return 0;
 135
 136         return -1;
 137 }
 138
 139 static char *user_path(char *buf, char *path, int sz)
 140 {
 141         struct passwd *pw;
 142         char *slash;
 143         int len, baselen;
 144
 145         if (!path || path[0] != '~')
 146                 return NULL;
 147         path++;
 148         slash = strchr(path, '/');
 149         if (path[0] == '/' || !path[0]) {
 150                 pw = getpwuid(getuid());
 151         }
 152         else {
 153                 if (slash) {
 154                         *slash = 0;
 155                         pw = getpwnam(path);
 156                         *slash = '/';
 157                 }
 158                 else
 159                         pw = getpwnam(path);
 160         }
 161         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 162                 return NULL;
 163         baselen = strlen(pw->pw_dir);
 164         memcpy(buf, pw->pw_dir, baselen);
 165         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 166                 buf[baselen-1] = 0;
 167                 baselen--;
 168         }
 169         if (slash && slash[1]) {
 170                 len = strlen(slash);
 171                 if (sz <= baselen + len)
 172                         return NULL;
 173                 memcpy(buf + baselen, slash, len + 1);
 174         }
 175         return buf;
 176 }
 177
 178 /*
 179  * First, one directory to try is determined by the following algorithm.
 180  *
 181  * (0) If "strict" is given, the path is used as given and no DWIM is
 182  *     done. Otherwise:
 183  * (1) "~/path" to mean path under the running user's home directory;
 184  * (2) "~user/path" to mean path under named user's home directory;
 185  * (3) "relative/path" to mean cwd relative directory; or
 186  * (4) "/absolute/path" to mean absolute directory.
 187  *
 188  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 189  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 190  * what we try.
 191  *
 192  * Second, we try chdir() to that.  Upon failure, we return NULL.
 193  *
 194  * Then, we try if the current directory is a valid git repository.
 195  * Upon failure, we return NULL.
 196  *
 197  * If all goes well, we return the directory we used to chdir() (but
 198  * before ~user is expanded), avoiding getcwd() resolving symbolic
 199  * links.  User relative paths are also returned as they are given,
 200  * except DWIM suffixing.
 201  */
 202 char *enter_repo(char *path, int strict)
 203 {
 204         static char used_path[PATH_MAX];
 205         static char validated_path[PATH_MAX];
 206
 207         if (!path)
 208                 return NULL;
 209
 210         if (!strict) {
 211                 static const char *suffix[] = {
 212                         ".git/.git", "/.git", ".git", "", NULL,
 213                 };
 214                 int len = strlen(path);
 215                 int i;
 216                 while ((1 < len) && (path[len-1] == '/')) {
 217                         path[len-1] = 0;
 218                         len--;
 219                 }
 220                 if (PATH_MAX <= len)
 221                         return NULL;
 222                 if (path[0] == '~') {
 223                         if (!user_path(used_path, path, PATH_MAX))
 224                                 return NULL;
 225                         strcpy(validated_path, path);
 226                         path = used_path;
 227                 }
 228                 else if (PATH_MAX - 10 < len)
 229                         return NULL;
 230                 else {
 231                         path = strcpy(used_path, path);
 232                         strcpy(validated_path, path);
 233                 }
 234                 len = strlen(path);
 235                 for (i = 0; suffix[i]; i++) {
 236                         strcpy(path + len, suffix[i]);
 237                         if (!access(path, F_OK)) {
 238                                 strcat(validated_path, suffix[i]);
 239                                 break;
 240                         }
 241                 }
 242                 if (!suffix[i] || chdir(path))
 243                         return NULL;
 244                 path = validated_path;
 245         }
 246         else if (chdir(path))
 247                 return NULL;
 248
 249         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 250             validate_headref("HEAD") == 0) {
 251                 setenv(GIT_DIR_ENVIRONMENT, ".", 1);
 252                 check_repository_format();
 253                 return path;
 254         }
 255
 256         return NULL;
 257 }
 258
 259 int adjust_shared_perm(const char *path)
 260 {
 261         struct stat st;
 262         int mode;
 263
 264         if (!shared_repository)
 265                 return 0;
 266         if (lstat(path, &st) < 0)
 267                 return -1;
 268         mode = st.st_mode;
 269
 270         if (shared_repository) {
 271                 int tweak = shared_repository;
 272                 if (!(mode & S_IWUSR))
 273                         tweak &= ~0222;
 274                 mode = (mode & ~0777) | tweak;
 275         } else {
 276                 /* Preserve old PERM_UMASK behaviour */
 277                 if (mode & S_IWUSR)
 278                         mode |= S_IWGRP;
 279         }
 280
 281         if (S_ISDIR(mode)) {
 282                 mode |= FORCE_DIR_SET_GID;
 283
 284                 /* Copy read bits to execute bits */
 285                 mode |= (shared_repository & 0444) >> 2;
 286         }
 287
 288         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 289                 return -2;
 290         return 0;
 291 }
 292
 293 /* We allow "recursive" symbolic links. Only within reason, though. */
 294 #define MAXDEPTH 5
 295
 296 const char *make_absolute_path(const char *path)
 297 {
 298         static char bufs[2][PATH_MAX + 1], *buf = bufs[0], *next_buf = bufs[1];
 299         char cwd[1024] = "";
 300         int buf_index = 1, len;
 301
 302         int depth = MAXDEPTH;
 303         char *last_elem = NULL;
 304         struct stat st;
 305
 306         if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
 307                 die ("Too long path: %.*s", 60, path);
 308
 309         while (depth--) {
 310                 if (stat(buf, &st) || !S_ISDIR(st.st_mode)) {
 311                         char *last_slash = strrchr(buf, '/');
 312                         if (last_slash) {
 313                                 *last_slash = '\0';
 314                                 last_elem = xstrdup(last_slash + 1);
 315                         } else {
 316                                 last_elem = xstrdup(buf);
 317                                 *buf = '\0';
 318                         }
 319                 }
 320
 321                 if (*buf) {
 322                         if (!*cwd && !getcwd(cwd, sizeof(cwd)))
 323                                 die ("Could not get current working directory");
 324
 325                         if (chdir(buf))
 326                                 die ("Could not switch to '%s'", buf);
 327                 }
 328                 if (!getcwd(buf, PATH_MAX))
 329                         die ("Could not get current working directory");
 330
 331                 if (last_elem) {
 332                         int len = strlen(buf);
 333                         if (len + strlen(last_elem) + 2 > PATH_MAX)
 334                                 die ("Too long path name: '%s/%s'",
 335                                                 buf, last_elem);
 336                         buf[len] = '/';
 337                         strcpy(buf + len + 1, last_elem);
 338                         free(last_elem);
 339                         last_elem = NULL;
 340                 }
 341
 342                 if (!lstat(buf, &st) && S_ISLNK(st.st_mode)) {
 343                         len = readlink(buf, next_buf, PATH_MAX);
 344                         if (len < 0)
 345                                 die ("Invalid symlink: %s", buf);
 346                         next_buf[len] = '\0';
 347                         buf = next_buf;
 348                         buf_index = 1 - buf_index;
 349                         next_buf = bufs[buf_index];
 350                 } else
 351                         break;
 352         }
 353
 354         if (*cwd && chdir(cwd))
 355                 die ("Could not change back to '%s'", cwd);
 356
 357         return buf;
 358 }