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 char *safe_strncpy(char *dest, const char *src, size_t n)
  87 {
  88         strncpy(dest, src, n);
  89         dest[n - 1] = '\0';
  90
  91         return dest;
  92 }
  93
  94 int validate_symref(const char *path)
  95 {
  96         struct stat st;
  97         char *buf, buffer[256];
  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(fd, buffer, sizeof(buffer)-1);
 118         close(fd);
 119
 120         /*
 121          * Is it a symbolic ref?
 122          */
 123         if (len < 4 || memcmp("ref:", buffer, 4))
 124                 return -1;
 125         buf = buffer + 4;
 126         len -= 4;
 127         while (len && isspace(*buf))
 128                 buf++, len--;
 129         if (len >= 5 && !memcmp("refs/", buf, 5))
 130                 return 0;
 131         return -1;
 132 }
 133
 134 static char *user_path(char *buf, char *path, int sz)
 135 {
 136         struct passwd *pw;
 137         char *slash;
 138         int len, baselen;
 139
 140         if (!path || path[0] != '~')
 141                 return NULL;
 142         path++;
 143         slash = strchr(path, '/');
 144         if (path[0] == '/' || !path[0]) {
 145                 pw = getpwuid(getuid());
 146         }
 147         else {
 148                 if (slash) {
 149                         *slash = 0;
 150                         pw = getpwnam(path);
 151                         *slash = '/';
 152                 }
 153                 else
 154                         pw = getpwnam(path);
 155         }
 156         if (!pw || !pw->pw_dir || sz <= strlen(pw->pw_dir))
 157                 return NULL;
 158         baselen = strlen(pw->pw_dir);
 159         memcpy(buf, pw->pw_dir, baselen);
 160         while ((1 < baselen) && (buf[baselen-1] == '/')) {
 161                 buf[baselen-1] = 0;
 162                 baselen--;
 163         }
 164         if (slash && slash[1]) {
 165                 len = strlen(slash);
 166                 if (sz <= baselen + len)
 167                         return NULL;
 168                 memcpy(buf + baselen, slash, len + 1);
 169         }
 170         return buf;
 171 }
 172
 173 /*
 174  * First, one directory to try is determined by the following algorithm.
 175  *
 176  * (0) If "strict" is given, the path is used as given and no DWIM is
 177  *     done. Otherwise:
 178  * (1) "~/path" to mean path under the running user's home directory;
 179  * (2) "~user/path" to mean path under named user's home directory;
 180  * (3) "relative/path" to mean cwd relative directory; or
 181  * (4) "/absolute/path" to mean absolute directory.
 182  *
 183  * Unless "strict" is given, we try access() for existence of "%s.git/.git",
 184  * "%s/.git", "%s.git", "%s" in this order.  The first one that exists is
 185  * what we try.
 186  *
 187  * Second, we try chdir() to that.  Upon failure, we return NULL.
 188  *
 189  * Then, we try if the current directory is a valid git repository.
 190  * Upon failure, we return NULL.
 191  *
 192  * If all goes well, we return the directory we used to chdir() (but
 193  * before ~user is expanded), avoiding getcwd() resolving symbolic
 194  * links.  User relative paths are also returned as they are given,
 195  * except DWIM suffixing.
 196  */
 197 char *enter_repo(char *path, int strict)
 198 {
 199         static char used_path[PATH_MAX];
 200         static char validated_path[PATH_MAX];
 201
 202         if (!path)
 203                 return NULL;
 204
 205         if (!strict) {
 206                 static const char *suffix[] = {
 207                         ".git/.git", "/.git", ".git", "", NULL,
 208                 };
 209                 int len = strlen(path);
 210                 int i;
 211                 while ((1 < len) && (path[len-1] == '/')) {
 212                         path[len-1] = 0;
 213                         len--;
 214                 }
 215                 if (PATH_MAX <= len)
 216                         return NULL;
 217                 if (path[0] == '~') {
 218                         if (!user_path(used_path, path, PATH_MAX))
 219                                 return NULL;
 220                         strcpy(validated_path, path);
 221                         path = used_path;
 222                 }
 223                 else if (PATH_MAX - 10 < len)
 224                         return NULL;
 225                 else {
 226                         path = strcpy(used_path, path);
 227                         strcpy(validated_path, path);
 228                 }
 229                 len = strlen(path);
 230                 for (i = 0; suffix[i]; i++) {
 231                         strcpy(path + len, suffix[i]);
 232                         if (!access(path, F_OK)) {
 233                                 strcat(validated_path, suffix[i]);
 234                                 break;
 235                         }
 236                 }
 237                 if (!suffix[i] || chdir(path))
 238                         return NULL;
 239                 path = validated_path;
 240         }
 241         else if (chdir(path))
 242                 return NULL;
 243
 244         if (access("objects", X_OK) == 0 && access("refs", X_OK) == 0 &&
 245             validate_symref("HEAD") == 0) {
 246                 putenv("GIT_DIR=.");
 247                 check_repository_format();
 248                 return path;
 249         }
 250
 251         return NULL;
 252 }