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