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, 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 if (resolved == NULL) { 69 resolved = malloc(PATH_MAX); 70 if (resolved == NULL) 71 return (NULL); 72 m = 1; 73 } else 74 m = 0; 75 symlinks = 0; 76 if (path[0] == '/') { 77 resolved[0] = '/'; 78 resolved[1] = '\0'; 79 if (path[1] == '\0') 80 return (resolved); 81 resolved_len = 1; 82 left_len = strlcpy(left, path + 1, sizeof(left)); 83 } else { 84 if (getcwd(resolved, PATH_MAX) == NULL) { 85 if (m) 86 free(resolved); 87 else { 88 resolved[0] = '.'; 89 resolved[1] = '\0'; 90 } 91 return (NULL); 92 } 93 resolved_len = strlen(resolved); 94 left_len = strlcpy(left, path, sizeof(left)); 95 } 96 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 97 if (m) 98 free(resolved); 99 errno = ENAMETOOLONG; 100 return (NULL); 101 } 102 103 /* 104 * Iterate over path components in `left'. 105 */ 106 while (left_len != 0) { 107 /* 108 * Extract the next path component and adjust `left' 109 * and its length. 110 */ 111 p = strchr(left, '/'); 112 s = p ? p : left + left_len; 113 if (s - left >= sizeof(next_token)) { 114 if (m) 115 free(resolved); 116 errno = ENAMETOOLONG; 117 return (NULL); 118 } 119 memcpy(next_token, left, s - left); 120 next_token[s - left] = '\0'; 121 left_len -= s - left; 122 if (p != NULL) 123 memmove(left, s + 1, left_len + 1); 124 if (resolved[resolved_len - 1] != '/') { 125 if (resolved_len + 1 >= PATH_MAX) { 126 if (m) 127 free(resolved); 128 errno = ENAMETOOLONG; 129 return (NULL); 130 } 131 resolved[resolved_len++] = '/'; 132 resolved[resolved_len] = '\0'; 133 } 134 if (next_token[0] == '\0') { 135 /* 136 * Handle consequential slashes. The path 137 * before slash shall point to a directory. 138 * 139 * Only the trailing slashes are not covered 140 * by other checks in the loop, but we verify 141 * the prefix for any (rare) "//" or "/\0" 142 * occurrence to not implement lookahead. 143 */ 144 if (lstat(resolved, &sb) != 0) { 145 if (m) 146 free(resolved); 147 return (NULL); 148 } 149 if (!S_ISDIR(sb.st_mode)) { 150 if (m) 151 free(resolved); 152 errno = ENOTDIR; 153 return (NULL); 154 } 155 continue; 156 } 157 else if (strcmp(next_token, ".") == 0) 158 continue; 159 else if (strcmp(next_token, "..") == 0) { 160 /* 161 * Strip the last path component except when we have 162 * single "/" 163 */ 164 if (resolved_len > 1) { 165 resolved[resolved_len - 1] = '\0'; 166 q = strrchr(resolved, '/') + 1; 167 *q = '\0'; 168 resolved_len = q - resolved; 169 } 170 continue; 171 } 172 173 /* 174 * Append the next path component and lstat() it. 175 */ 176 resolved_len = strlcat(resolved, next_token, PATH_MAX); 177 if (resolved_len >= PATH_MAX) { 178 if (m) 179 free(resolved); 180 errno = ENAMETOOLONG; 181 return (NULL); 182 } 183 if (lstat(resolved, &sb) != 0) { 184 if (m) 185 free(resolved); 186 return (NULL); 187 } 188 if (S_ISLNK(sb.st_mode)) { 189 if (symlinks++ > MAXSYMLINKS) { 190 if (m) 191 free(resolved); 192 errno = ELOOP; 193 return (NULL); 194 } 195 slen = readlink(resolved, symlink, sizeof(symlink) - 1); 196 if (slen < 0) { 197 if (m) 198 free(resolved); 199 return (NULL); 200 } 201 symlink[slen] = '\0'; 202 if (symlink[0] == '/') { 203 resolved[1] = 0; 204 resolved_len = 1; 205 } else if (resolved_len > 1) { 206 /* Strip the last path component. */ 207 resolved[resolved_len - 1] = '\0'; 208 q = strrchr(resolved, '/') + 1; 209 *q = '\0'; 210 resolved_len = q - resolved; 211 } 212 213 /* 214 * If there are any path components left, then 215 * append them to symlink. The result is placed 216 * in `left'. 217 */ 218 if (p != NULL) { 219 if (symlink[slen - 1] != '/') { 220 if (slen + 1 >= sizeof(symlink)) { 221 if (m) 222 free(resolved); 223 errno = ENAMETOOLONG; 224 return (NULL); 225 } 226 symlink[slen] = '/'; 227 symlink[slen + 1] = 0; 228 } 229 left_len = strlcat(symlink, left, 230 sizeof(symlink)); 231 if (left_len >= sizeof(left)) { 232 if (m) 233 free(resolved); 234 errno = ENAMETOOLONG; 235 return (NULL); 236 } 237 } 238 left_len = strlcpy(left, symlink, sizeof(left)); 239 } 240 } 241 242 /* 243 * Remove trailing slash except when the resolved pathname 244 * is a single "/". 245 */ 246 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 247 resolved[resolved_len - 1] = '\0'; 248 return (resolved); 249 } 250