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                 strcpy(pch, "/tmp/");
  78                 len -= 5;
  79                 pch += 5;
  80         } else {
  81                 size_t n = snprintf(pch, len, "%s/", env);
  82
  83                 len -= n;
  84                 pch += n;
  85         }
  86
  87         strlcpy(pch, template, len);
  88
  89         return mkstemp(path);
  90 }
  91
  92
  93 int validate_symref(const char *path)
  94 {
  95         struct stat st;
  96         char *buf, buffer[256];
  97         int len, fd;
  98
  99         if (lstat(path, &st) < 0)
 100                 return -1;
 101
 102         /* Make sure it is a "refs/.." symlink */
 103         if (S_ISLNK(st.st_mode)) {
 104                 len = readlink(path, buffer, sizeof(buffer)-1);
 105                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 106                         return 0;
 107                 return -1;
 108         }
 109
 110         /*
 111          * Anything else, just open it and try to see if it is a symbolic ref.
 112          */
 113         fd = open(path, O_RDONLY);
 114         if (fd < 0)
 115                 return -1;
 116         len = read(fd, buffer, sizeof(buffer)-1);
 117         close(fd);
 118
 119         /*
 120          * Is it a symbolic ref?
 121          */
 122         if (len < 4 || memcmp("ref:", buffer, 4))
 123                 return -1;
 124         buf = buffer + 4;
 125         len -= 4;
 126         while (len && isspace(*buf))
 127                 buf++, len--;
 128         if (len >= 5 && !memcmp("refs/", buf, 5))
 129                 return 0;
 130         return -1;
 131 }
 132
 133 static char *user_path(char *buf, char *path, int sz)
 134 {
 135         struct passwd *pw;
 136         char *slash;
 137         int len, baselen;
 138
 139         if (!path || path[0] != '~')
 140                 return NULL;
 141         path++;
 142         slash = strchr(path, '/');
 143         if (path[0] == '/' || !path[0]) {
 144                 pw = getpwuid(getuid());
 145         }
 146         else {
 147                 if (slash) {
 148                         *slash = 0;
 149                         pw = getpwnam(path);
 150                         *slash = '/';
 151                 }
 152                 else
 153                         pw = getpwnam(path);
 154         }
 155         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 156                 return NULL;
 157         baselen = strlen(pw->pw_dir);
 158         memcpy(buf, pw->pw_dir, baselen);
 159         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 160                 buf[baselen-1] = 0;
 161                 baselen--;
 162         }
 163         if (slash && slash[1]) {
 164                 len = strlen(slash);
 165                 if (sz <= baselen + len)
 166                         return NULL;
 167                 memcpy(buf + baselen, slash, len + 1);
 168         }
 169         return buf;
 170 }
 171
 172 /*
 173  * First, one directory to try is determined by the following algorithm.
 174  *
 175  * (0) If "strict" is given, the path is used as given and no DWIM is
 176  *     done. Otherwise:
 177  * (1) "~/path" to mean path under the running user's home directory;
 178  * (2) "~user/path" to mean path under named user's home directory;
 179  * (3) "relative/path" to mean cwd relative directory; or
 180  * (4) "/absolute/path" to mean absolute directory.
 181  *
 182  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 183  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 184  * what we try.
 185  *
 186  * Second, we try chdir() to that.  Upon failure, we return NULL.
 187  *
 188  * Then, we try if the current directory is a valid git repository.
 189  * Upon failure, we return NULL.
 190  *
 191  * If all goes well, we return the directory we used to chdir() (but
 192  * before ~user is expanded), avoiding getcwd() resolving symbolic
 193  * links.  User relative paths are also returned as they are given,
 194  * except DWIM suffixing.
 195  */
 196 char *enter_repo(char *path, int strict)
 197 {
 198         static char used_path[PATH_MAX];
 199         static char validated_path[PATH_MAX];
 200
 201         if (!path)
 202                 return NULL;
 203
 204         if (!strict) {
 205                 static const char *suffix[] = {
 206                         ".git/.git", "/.git", ".git", "", NULL,
 207                 };
 208                 int len = strlen(path);
 209                 int i;
 210                 while ((1 < len) && (path[len-1] == '/')) {
 211                         path[len-1] = 0;
 212                         len--;
 213                 }
 214                 if (PATH_MAX <= len)
 215                         return NULL;
 216                 if (path[0] == '~') {
 217                         if (!user_path(used_path, path, PATH_MAX))
 218                                 return NULL;
 219                         strcpy(validated_path, path);
 220                         path = used_path;
 221                 }
 222                 else if (PATH_MAX - 10 < len)
 223                         return NULL;
 224                 else {
 225                         path = strcpy(used_path, path);
 226                         strcpy(validated_path, path);
 227                 }
 228                 len = strlen(path);
 229                 for (i = 0; suffix[i]; i++) {
 230                         strcpy(path + len, suffix[i]);
 231                         if (!access(path, F_OK)) {
 232                                 strcat(validated_path, suffix[i]);
 233                                 break;
 234                         }
 235                 }
 236                 if (!suffix[i] || chdir(path))
 237                         return NULL;
 238                 path = validated_path;
 239         }
 240         else if (chdir(path))
 241                 return NULL;
 242
 243         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 244             validate_symref("HEAD") == 0) {
 245                 putenv("GIT_DIR=.");
 246                 check_repository_format();
 247                 return path;
 248         }
 249
 250         return NULL;
 251 }
 252
 253 int adjust_shared_perm(const char *path)
 254 {
 255         struct stat st;
 256         int mode;
 257
 258         if (!shared_repository)
 259                 return 0;
 260         if (lstat(path, &st) < 0)
 261                 return -1;
 262         mode = st.st_mode;
 263         if (mode & S_IRUSR)
 264                 mode |= (shared_repository == PERM_GROUP
 265                          ? S_IRGRP
 266                          : (shared_repository == PERM_EVERYBODY
 267                             ? (S_IRGRP|S_IROTH)
 268                             : 0));
 269
 270         if (mode & S_IWUSR)
 271                 mode |= S_IWGRP;
 272
 273         if (mode & S_IXUSR)
 274                 mode |= (shared_repository == PERM_GROUP
 275                          ? S_IXGRP
 276                          : (shared_repository == PERM_EVERYBODY
 277                             ? (S_IXGRP|S_IXOTH)
 278                             : 0));
 279         if (S_ISDIR(mode))
 280                 mode |= S_ISGID;
 281         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 282                 return -2;
 283         return 0;
 284 }