1 /* 2 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru> 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 3. The names of the authors may not be used to endorse or promote 13 * products derived from this software without specific prior written 14 * permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #if defined(LIBC_SCCS) && !defined(lint) 30 static char sccsid[] = "@(#)realpath.c 8.1 (Berkeley) 2/16/94"; 31 #endif /* LIBC_SCCS and not lint */ 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "namespace.h" 36 #include <sys/param.h> 37 #include <sys/stat.h> 38 39 #include <errno.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <unistd.h> 43 #include "un-namespace.h" 44 45 /* 46 * Find the real name of path, by removing all ".", ".." and symlink 47 * components. Returns (resolved) on success, or (NULL) on failure, 48 * in which case the path which caused trouble is left in (resolved). 49 */ 50 char * 51 realpath(const char * __restrict path, char * __restrict resolved) 52 { 53 struct stat sb; 54 char *p, *q, *s; 55 size_t left_len, resolved_len; 56 unsigned symlinks; 57 int m, serrno, slen; 58 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; 59 60 if (path == NULL) { 61 errno = EINVAL; 62 return (NULL); 63 } 64 if (path[0] == '\0') { 65 errno = ENOENT; 66 return (NULL); 67 } 68 serrno = errno; 69 if (resolved == NULL) { 70 resolved = malloc(PATH_MAX); 71 if (resolved == NULL) 72 return (NULL); 73 m = 1; 74 } else 75 m = 0; 76 symlinks = 0; 77 if (path[0] == '/') { 78 resolved[0] = '/'; 79 resolved[1] = '\0'; 80 if (path[1] == '\0') 81 return (resolved); 82 resolved_len = 1; 83 left_len = strlcpy(left, path + 1, sizeof(left)); 84 } else { 85 if (getcwd(resolved, PATH_MAX) == NULL) { 86 if (m) 87 free(resolved); 88 else { 89 resolved[0] = '.'; 90 resolved[1] = '\0'; 91 } 92 return (NULL); 93 } 94 resolved_len = strlen(resolved); 95 left_len = strlcpy(left, path, sizeof(left)); 96 } 97 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 98 if (m) 99 free(resolved); 100 errno = ENAMETOOLONG; 101 return (NULL); 102 } 103 104 /* 105 * Iterate over path components in `left'. 106 */ 107 while (left_len != 0) { 108 /* 109 * Extract the next path component and adjust `left' 110 * and its length. 111 */ 112 p = strchr(left, '/'); 113 s = p ? p : left + left_len; 114 if (s - left >= sizeof(next_token)) { 115 if (m) 116 free(resolved); 117 errno = ENAMETOOLONG; 118 return (NULL); 119 } 120 memcpy(next_token, left, s - left); 121 next_token[s - left] = '\0'; 122 left_len -= s - left; 123 if (p != NULL) 124 memmove(left, s + 1, left_len + 1); 125 if (resolved[resolved_len - 1] != '/') { 126 if (resolved_len + 1 >= PATH_MAX) { 127 if (m) 128 free(resolved); 129 errno = ENAMETOOLONG; 130 return (NULL); 131 } 132 resolved[resolved_len++] = '/'; 133 resolved[resolved_len] = '\0'; 134 } 135 if (next_token[0] == '\0') { 136 /* 137 * Handle consequential slashes. The path 138 * before slash shall point to a directory. 139 * 140 * Only the trailing slashes are not covered 141 * by other checks in the loop, but we verify 142 * the prefix for any (rare) "//" or "/\0" 143 * occurence to not implement lookahead. 144 */ 145 if (lstat(resolved, &sb) != 0) { 146 if (m) 147 free(resolved); 148 return (NULL); 149 } 150 if (!S_ISDIR(sb.st_mode)) { 151 if (m) 152 free(resolved); 153 errno = ENOTDIR; 154 return (NULL); 155 } 156 continue; 157 } 158 else if (strcmp(next_token, ".") == 0) 159 continue; 160 else if (strcmp(next_token, "..") == 0) { 161 /* 162 * Strip the last path component except when we have 163 * single "/" 164 */ 165 if (resolved_len > 1) { 166 resolved[resolved_len - 1] = '\0'; 167 q = strrchr(resolved, '/') + 1; 168 *q = '\0'; 169 resolved_len = q - resolved; 170 } 171 continue; 172 } 173 174 /* 175 * Append the next path component and lstat() it. 176 */ 177 resolved_len = strlcat(resolved, next_token, PATH_MAX); 178 if (resolved_len >= PATH_MAX) { 179 if (m) 180 free(resolved); 181 errno = ENAMETOOLONG; 182 return (NULL); 183 } 184 if (lstat(resolved, &sb) != 0) { 185 if (errno != ENOENT || p != NULL) 186 errno = ENOTDIR; 187 if (m) 188 free(resolved); 189 return (NULL); 190 } 191 if (S_ISLNK(sb.st_mode)) { 192 if (symlinks++ > MAXSYMLINKS) { 193 if (m) 194 free(resolved); 195 errno = ELOOP; 196 return (NULL); 197 } 198 slen = readlink(resolved, symlink, sizeof(symlink) - 1); 199 if (slen < 0) { 200 if (m) 201 free(resolved); 202 return (NULL); 203 } 204 symlink[slen] = '\0'; 205 if (symlink[0] == '/') { 206 resolved[1] = 0; 207 resolved_len = 1; 208 } else if (resolved_len > 1) { 209 /* Strip the last path component. */ 210 resolved[resolved_len - 1] = '\0'; 211 q = strrchr(resolved, '/') + 1; 212 *q = '\0'; 213 resolved_len = q - resolved; 214 } 215 216 /* 217 * If there are any path components left, then 218 * append them to symlink. The result is placed 219 * in `left'. 220 */ 221 if (p != NULL) { 222 if (symlink[slen - 1] != '/') { 223 if (slen + 1 >= sizeof(symlink)) { 224 if (m) 225 free(resolved); 226 errno = ENAMETOOLONG; 227 return (NULL); 228 } 229 symlink[slen] = '/'; 230 symlink[slen + 1] = 0; 231 } 232 left_len = strlcat(symlink, left, 233 sizeof(symlink)); 234 if (left_len >= sizeof(left)) { 235 if (m) 236 free(resolved); 237 errno = ENAMETOOLONG; 238 return (NULL); 239 } 240 } 241 left_len = strlcpy(left, symlink, sizeof(left)); 242 } 243 } 244 245 /* 246 * Remove trailing slash except when the resolved pathname 247 * is a single "/". 248 */ 249 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 250 resolved[resolved_len - 1] = '\0'; 251 return (resolved); 252 } 253