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_headref(const char *path)
  94 {
  95         struct stat st;
  96         char *buf, buffer[256];
  97         unsigned char sha1[20];
  98         int len, fd;
  99
 100         if (lstat(path, &st) < 0)
 101                 return -1;
 102
 103         /* Make sure it is a "refs/.." symlink */
 104         if (S_ISLNK(st.st_mode)) {
 105                 len = readlink(path, buffer, sizeof(buffer)-1);
 106                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 107                         return 0;
 108                 return -1;
 109         }
 110
 111         /*
 112          * Anything else, just open it and try to see if it is a symbolic ref.
 113          */
 114         fd = open(path, O_RDONLY);
 115         if (fd < 0)
 116                 return -1;
 117         len = read_in_full(fd, buffer, sizeof(buffer)-1);
 118         close(fd);
 119
 120         /*
 121          * Is it a symbolic ref?
 122          */
 123         if (len < 4)
 124                 return -1;
 125         if (!memcmp("ref:", buffer, 4)) {
 126                 buf = buffer + 4;
 127                 len -= 4;
 128                 while (len && isspace(*buf))
 129                         buf++, len--;
 130                 if (len >= 5 && !memcmp("refs/", buf, 5))
 131                         return 0;
 132         }
 133
 134         /*
 135          * Is this a detached HEAD?
 136          */
 137         if (!get_sha1_hex(buffer, sha1))
 138                 return 0;
 139
 140         return -1;
 141 }
 142
 143 #ifndef NO_ETC_PASSWD
 144
 145 static char *user_path(char *buf, char *path, int sz)
 146 {
 147         struct passwd *pw;
 148         char *slash;
 149         int len, baselen;
 150
 151         if (!path || path[0] != '~')
 152                 return NULL;
 153         path++;
 154         slash = strchr(path, '/');
 155         if (path[0] == '/' || !path[0]) {
 156                 pw = getpwuid(getuid());
 157         }
 158         else {
 159                 if (slash) {
 160                         *slash = 0;
 161                         pw = getpwnam(path);
 162                         *slash = '/';
 163                 }
 164                 else
 165                         pw = getpwnam(path);
 166         }
 167         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 168                 return NULL;
 169         baselen = strlen(pw->pw_dir);
 170         memcpy(buf, pw->pw_dir, baselen);
 171         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 172                 buf[baselen-1] = 0;
 173                 baselen--;
 174         }
 175         if (slash && slash[1]) {
 176                 len = strlen(slash);
 177                 if (sz <= baselen + len)
 178                         return NULL;
 179                 memcpy(buf + baselen, slash, len + 1);
 180         }
 181         return buf;
 182 }
 183
 184 #else
 185
 186 static char *user_path(char *buf, char *path, int sz)
 187 {
 188         return getenv("HOME");
 189 }
 190
 191 #endif
 192
 193 /*
 194  * First, one directory to try is determined by the following algorithm.
 195  *
 196  * (0) If "strict" is given, the path is used as given and no DWIM is
 197  *     done. Otherwise:
 198  * (1) "~/path" to mean path under the running user's home directory;
 199  * (2) "~user/path" to mean path under named user's home directory;
 200  * (3) "relative/path" to mean cwd relative directory; or
 201  * (4) "/absolute/path" to mean absolute directory.
 202  *
 203  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 204  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 205  * what we try.
 206  *
 207  * Second, we try chdir() to that.  Upon failure, we return NULL.
 208  *
 209  * Then, we try if the current directory is a valid git repository.
 210  * Upon failure, we return NULL.
 211  *
 212  * If all goes well, we return the directory we used to chdir() (but
 213  * before ~user is expanded), avoiding getcwd() resolving symbolic
 214  * links.  User relative paths are also returned as they are given,
 215  * except DWIM suffixing.
 216  */
 217 char *enter_repo(char *path, int strict)
 218 {
 219         static char used_path[PATH_MAX];
 220         static char validated_path[PATH_MAX];
 221
 222         if (!path)
 223                 return NULL;
 224
 225         if (!strict) {
 226                 static const char *suffix[] = {
 227                         ".git/.git", "/.git", ".git", "", NULL,
 228                 };
 229                 int len = strlen(path);
 230                 int i;
 231                 while ((1 < len) && (path[len-1] == '/')) {
 232                         path[len-1] = 0;
 233                         len--;
 234                 }
 235                 if (PATH_MAX <= len)
 236                         return NULL;
 237                 if (path[0] == '~') {
 238                         if (!user_path(used_path, path, PATH_MAX))
 239                                 return NULL;
 240                         strcpy(validated_path, path);
 241                         path = used_path;
 242                 }
 243                 else if (PATH_MAX - 10 < len)
 244                         return NULL;
 245                 else {
 246                         path = strcpy(used_path, path);
 247                         strcpy(validated_path, path);
 248                 }
 249                 len = strlen(path);
 250                 for (i = 0; suffix[i]; i++) {
 251                         strcpy(path + len, suffix[i]);
 252                         if (!access(path, F_OK)) {
 253                                 strcat(validated_path, suffix[i]);
 254                                 break;
 255                         }
 256                 }
 257                 if (!suffix[i] || chdir(path))
 258                         return NULL;
 259                 path = validated_path;
 260         }
 261         else if (chdir(path))
 262                 return NULL;
 263
 264         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 265             validate_headref("HEAD") == 0) {
 266                 setenv("GIT_DIR", ".", 1);
 267                 check_repository_format();
 268                 return path;
 269         }
 270
 271         return NULL;
 272 }
 273
 274 int adjust_shared_perm(const char *path)
 275 {
 276         struct stat st;
 277         int mode;
 278
 279         if (!shared_repository)
 280                 return 0;
 281         if (lstat(path, &st) < 0)
 282                 return -1;
 283         mode = st.st_mode;
 284         if (mode & S_IRUSR)
 285                 mode |= (shared_repository == PERM_GROUP
 286                          ? S_IRGRP
 287                          : (shared_repository == PERM_EVERYBODY
 288                             ? (S_IRGRP|S_IROTH)
 289                             : 0));
 290
 291         if (mode & S_IWUSR)
 292                 mode |= S_IWGRP;
 293
 294         if (mode & S_IXUSR)
 295                 mode |= (shared_repository == PERM_GROUP
 296                          ? S_IXGRP
 297                          : (shared_repository == PERM_EVERYBODY
 298                             ? (S_IXGRP|S_IXOTH)
 299                             : 0));
 300         if (S_ISDIR(mode))
 301                 mode |= S_ISGID;
 302         if ((mode & st.st_mode) != mode && chmod(path, mode) < 0)
 303                 return -2;
 304         return 0;
 305 }