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 #include <pwd.h>
  15
  16 static char pathname[PATH_MAX];
  17 static char bad_path[] = "/bad-path/";
  18
  19 static char *cleanup_path(char *path)
  20 {
  21         /* Clean it up */
  22         if (!memcmp(path, "./", 2)) {
  23                 path += 2;
  24                 while (*path == '/')
  25                         path++;
  26         }
  27         return path;
  28 }
  29
  30 char *mkpath(const char *fmt, ...)
  31 {
  32         va_list args;
  33         unsigned len;
  34
  35         va_start(args, fmt);
  36         len = vsnprintf(pathname, PATH_MAX, fmt, args);
  37         va_end(args);
  38         if (len >= PATH_MAX)
  39                 return bad_path;
  40         return cleanup_path(pathname);
  41 }
  42
  43 char *git_path(const char *fmt, ...)
  44 {
  45         const char *git_dir = get_git_dir();
  46         va_list args;
  47         unsigned len;
  48
  49         len = strlen(git_dir);
  50         if (len > PATH_MAX-100)
  51                 return bad_path;
  52         memcpy(pathname, git_dir, len);
  53         if (len && git_dir[len-1] != '/')
  54                 pathname[len++] = '/';
  55         va_start(args, fmt);
  56         len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
  57         va_end(args);
  58         if (len >= PATH_MAX)
  59                 return bad_path;
  60         return cleanup_path(pathname);
  61 }
  62
  63
  64 /* git_mkstemp() - create tmp file honoring TMPDIR variable */
  65 int git_mkstemp(char *path, size_t len, const char *template)
  66 {
  67         char *env, *pch = path;
  68
  69         if ((env = getenv("TMPDIR")) == NULL) {
  70                 strcpy(pch, "/tmp/");
  71                 len -= 5;
  72                 pch += 5;
  73         } else {
  74                 size_t n = snprintf(pch, len, "%s/", env);
  75
  76                 len -= n;
  77                 pch += n;
  78         }
  79
  80         safe_strncpy(pch, template, len);
  81
  82         return mkstemp(path);
  83 }
  84
  85
  86 size_t safe_strncpy(char *dest, const char *src, size_t size)
  87 {
  88         size_t ret = strlen(src);
  89
  90         if (size) {
  91                 size_t len = (ret >= size) ? size - 1 : ret;
  92                 memcpy(dest, src, len);
  93                 dest[len] = '\0';
  94         }
  95         return ret;
  96 }
  97
  98
  99 int validate_symref(const char *path)
 100 {
 101         struct stat st;
 102         char *buf, buffer[256];
 103         int len, fd;
 104
 105         if (lstat(path, &st) < 0)
 106                 return -1;
 107
 108         /* Make sure it is a "refs/.." symlink */
 109         if (S_ISLNK(st.st_mode)) {
 110                 len = readlink(path, buffer, sizeof(buffer)-1);
 111                 if (len >= 5 && !memcmp("refs/", buffer, 5))
 112                         return 0;
 113                 return -1;
 114         }
 115
 116         /*
 117          * Anything else, just open it and try to see if it is a symbolic ref.
 118          */
 119         fd = open(path, O_RDONLY);
 120         if (fd < 0)
 121                 return -1;
 122         len = read(fd, buffer, sizeof(buffer)-1);
 123         close(fd);
 124
 125         /*
 126          * Is it a symbolic ref?
 127          */
 128         if (len < 4 || memcmp("ref:", buffer, 4))
 129                 return -1;
 130         buf = buffer + 4;
 131         len -= 4;
 132         while (len && isspace(*buf))
 133                 buf++, len--;
 134         if (len >= 5 && !memcmp("refs/", buf, 5))
 135                 return 0;
 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_symref("HEAD") == 0) {
 251                 putenv("GIT_DIR=.");
 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         if (mode & S_IRUSR)
 270                 mode |= S_IRGRP;
 271         if (mode & S_IWUSR)
 272                 mode |= S_IWGRP;
 273         if (mode & S_IXUSR)
 274                 mode |= S_IXGRP;
 275         if (S_ISDIR(mode))
 276                 mode |= S_ISGID;
 277         if (chmod(path, mode) < 0)
 278                 return -2;
 279         return 0;
 280 }