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         char *env, *pch = path;
  75
  76         if ((env = getenv("TMPDIR")) == NULL &&
  77             /* on Windows it is TMP and TEMP */
  78             (env = getenv("TMP")) == NULL &&
  79             (env = getenv("TEMP")) == NULL) {
  80                 strcpy(pch, "/tmp/");
  81                 len -= 5;
  82                 pch += 5;
  83         } else {
  84                 size_t n = snprintf(pch, len, "%s/", env);
  85
  86                 len -= n;
  87                 pch += n;
  88         }
  89
  90         strlcpy(pch, template, len);
  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 #ifndef NO_ETC_PASSWD
 147
 148 static char *user_path(char *buf, char *path, int sz)
 149 {
 150         struct passwd *pw;
 151         char *slash;
 152         int len, baselen;
 153
 154         if (!path || path[0] != '~')
 155                 return NULL;
 156         path++;
 157         slash = strchr(path, '/');
 158         if (path[0] == '/' || !path[0]) {
 159                 pw = getpwuid(getuid());
 160         }
 161         else {
 162                 if (slash) {
 163                         *slash = 0;
 164                         pw = getpwnam(path);
 165                         *slash = '/';
 166                 }
 167                 else
 168                         pw = getpwnam(path);
 169         }
 170         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 171                 return NULL;
 172         baselen = strlen(pw->pw_dir);
 173         memcpy(buf, pw->pw_dir, baselen);
 174         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 175                 buf[baselen-1] = 0;
 176                 baselen--;
 177         }
 178         if (slash && slash[1]) {
 179                 len = strlen(slash);
 180                 if (sz <= baselen + len)
 181                         return NULL;
 182                 memcpy(buf + baselen, slash, len + 1);
 183         }
 184         return buf;
 185 }
 186
 187 #else
 188
 189 static char *user_path(char *buf, char *path, int sz)
 190 {
 191         return getenv("HOME");
 192 }
 193
 194 #endif
 195
 196 /*
 197  * First, one directory to try is determined by the following algorithm.
 198  *
 199  * (0) If "strict" is given, the path is used as given and no DWIM is
 200  *     done. Otherwise:
 201  * (1) "~/path" to mean path under the running user's home directory;
 202  * (2) "~user/path" to mean path under named user's home directory;
 203  * (3) "relative/path" to mean cwd relative directory; or
 204  * (4) "/absolute/path" to mean absolute directory.
 205  *
 206  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 207  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 208  * what we try.
 209  *
 210  * Second, we try chdir() to that.  Upon failure, we return NULL.
 211  *
 212  * Then, we try if the current directory is a valid git repository.
 213  * Upon failure, we return NULL.
 214  *
 215  * If all goes well, we return the directory we used to chdir() (but
 216  * before ~user is expanded), avoiding getcwd() resolving symbolic
 217  * links.  User relative paths are also returned as they are given,
 218  * except DWIM suffixing.
 219  */
 220 char *enter_repo(char *path, int strict)
 221 {
 222         static char used_path[PATH_MAX];
 223         static char validated_path[PATH_MAX];
 224
 225         if (!path)
 226                 return NULL;
 227
 228         if (!strict) {
 229                 static const char *suffix[] = {
 230                         ".git/.git", "/.git", ".git", "", NULL,
 231                 };
 232                 int len = strlen(path);
 233                 int i;
 234                 while ((1 < len) && (path[len-1] == '/')) {
 235                         path[len-1] = 0;
 236                         len--;
 237                 }
 238                 if (PATH_MAX <= len)
 239                         return NULL;
 240                 if (path[0] == '~') {
 241                         if (!user_path(used_path, path, PATH_MAX))
 242                                 return NULL;
 243                         strcpy(validated_path, path);
 244                         path = used_path;
 245                 }
 246                 else if (PATH_MAX - 10 < len)
 247                         return NULL;
 248                 else {
 249                         path = strcpy(used_path, path);
 250                         strcpy(validated_path, path);
 251                 }
 252                 len = strlen(path);
 253                 for (i = 0; suffix[i]; i++) {
 254                         strcpy(path + len, suffix[i]);
 255                         if (!access(path, F_OK)) {
 256                                 strcat(validated_path, suffix[i]);
 257                                 break;
 258                         }
 259                 }
 260                 if (!suffix[i] || chdir(path))
 261                         return NULL;
 262                 path = validated_path;
 263         }
 264         else if (chdir(path))
 265                 return NULL;
 266
 267         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 268             validate_headref("HEAD") == 0) {
 269                 setenv("GIT_DIR", ".", 1);
 270                 check_repository_format();
 271                 return path;
 272         }
 273
 274         return NULL;
 275 }
 276
 277 int adjust_shared_perm(const char *path)
 278 {
 279         struct stat st;
 280         int mode;
 281
 282         if (!shared_repository)
 283                 return 0;
 284         if (lstat(path, &st) < 0)
 285                 return -1;
 286         mode = st.st_mode;
 287         if (mode & S_IRUSR)
 288                 mode |= (shared_repository == PERM_GROUP
 289                          ? S_IRGRP
 290                          : (shared_repository == PERM_EVERYBODY
 291                             ? (S_IRGRP|S_IROTH)
 292                             : 0));
 293
 294         if (mode & S_IWUSR)
 295                 mode |= S_IWGRP;
 296
 297         if (mode & S_IXUSR)
 298                 mode |= (shared_repository == PERM_GROUP
 299                          ? S_IXGRP
 300                          : (shared_repository == PERM_EVERYBODY
 301                             ? (S_IXGRP|S_IXOTH)
 302                             : 0));
 303         if (S_ISDIR(mode))
 304                 mode |= S_ISGID;
 305         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 306                 return -2;
 307         return 0;
 308 }