realpath.c revision 236582
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) 30static 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: head/lib/libc/stdlib/realpath.c 236582 2012-06-04 21:34:49Z ache $"); 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 */ 50char * 51realpath(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 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 serrno = errno; 87 free(resolved); 88 errno = serrno; 89 } else { 90 resolved[0] = '.'; 91 resolved[1] = '\0'; 92 } 93 return (NULL); 94 } 95 resolved_len = strlen(resolved); 96 left_len = strlcpy(left, path, sizeof(left)); 97 } 98 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 99 if (m) 100 free(resolved); 101 errno = ENAMETOOLONG; 102 return (NULL); 103 } 104 105 /* 106 * Iterate over path components in `left'. 107 */ 108 while (left_len != 0) { 109 /* 110 * Extract the next path component and adjust `left' 111 * and its length. 112 */ 113 p = strchr(left, '/'); 114 s = p ? p : left + left_len; 115 if (s - left >= sizeof(next_token)) { 116 if (m) 117 free(resolved); 118 errno = ENAMETOOLONG; 119 return (NULL); 120 } 121 memcpy(next_token, left, s - left); 122 next_token[s - left] = '\0'; 123 left_len -= s - left; 124 if (p != NULL) 125 memmove(left, s + 1, left_len + 1); 126 if (resolved[resolved_len - 1] != '/') { 127 if (resolved_len + 1 >= PATH_MAX) { 128 if (m) 129 free(resolved); 130 errno = ENAMETOOLONG; 131 return (NULL); 132 } 133 resolved[resolved_len++] = '/'; 134 resolved[resolved_len] = '\0'; 135 } 136 if (next_token[0] == '\0') { 137 /* 138 * Handle consequential slashes. The path 139 * before slash shall point to a directory. 140 * 141 * Only the trailing slashes are not covered 142 * by other checks in the loop, but we verify 143 * the prefix for any (rare) "//" or "/\0" 144 * occurence to not implement lookahead. 145 */ 146 if (lstat(resolved, &sb) != 0) { 147 if (m) { 148 serrno = errno; 149 free(resolved); 150 errno = serrno; 151 } 152 return (NULL); 153 } 154 if (!S_ISDIR(sb.st_mode)) { 155 if (m) 156 free(resolved); 157 errno = ENOTDIR; 158 return (NULL); 159 } 160 continue; 161 } 162 else if (strcmp(next_token, ".") == 0) 163 continue; 164 else if (strcmp(next_token, "..") == 0) { 165 /* 166 * Strip the last path component except when we have 167 * single "/" 168 */ 169 if (resolved_len > 1) { 170 resolved[resolved_len - 1] = '\0'; 171 q = strrchr(resolved, '/') + 1; 172 *q = '\0'; 173 resolved_len = q - resolved; 174 } 175 continue; 176 } 177 178 /* 179 * Append the next path component and lstat() it. 180 */ 181 resolved_len = strlcat(resolved, next_token, PATH_MAX); 182 if (resolved_len >= PATH_MAX) { 183 if (m) 184 free(resolved); 185 errno = ENAMETOOLONG; 186 return (NULL); 187 } 188 if (lstat(resolved, &sb) != 0) { 189 if (errno != ENOENT || p != NULL) 190 errno = ENOTDIR; 191 if (m) { 192 serrno = errno; 193 free(resolved); 194 errno = serrno; 195 } 196 return (NULL); 197 } 198 if (S_ISLNK(sb.st_mode)) { 199 if (symlinks++ > MAXSYMLINKS) { 200 if (m) 201 free(resolved); 202 errno = ELOOP; 203 return (NULL); 204 } 205 slen = readlink(resolved, symlink, sizeof(symlink) - 1); 206 if (slen < 0) { 207 if (m) { 208 serrno = errno; 209 free(resolved); 210 errno = serrno; 211 } 212 return (NULL); 213 } 214 symlink[slen] = '\0'; 215 if (symlink[0] == '/') { 216 resolved[1] = 0; 217 resolved_len = 1; 218 } else if (resolved_len > 1) { 219 /* Strip the last path component. */ 220 resolved[resolved_len - 1] = '\0'; 221 q = strrchr(resolved, '/') + 1; 222 *q = '\0'; 223 resolved_len = q - resolved; 224 } 225 226 /* 227 * If there are any path components left, then 228 * append them to symlink. The result is placed 229 * in `left'. 230 */ 231 if (p != NULL) { 232 if (symlink[slen - 1] != '/') { 233 if (slen + 1 >= sizeof(symlink)) { 234 if (m) 235 free(resolved); 236 errno = ENAMETOOLONG; 237 return (NULL); 238 } 239 symlink[slen] = '/'; 240 symlink[slen + 1] = 0; 241 } 242 left_len = strlcat(symlink, left, 243 sizeof(symlink)); 244 if (left_len >= sizeof(left)) { 245 if (m) 246 free(resolved); 247 errno = ENAMETOOLONG; 248 return (NULL); 249 } 250 } 251 left_len = strlcpy(left, symlink, sizeof(left)); 252 } 253 } 254 255 /* 256 * Remove trailing slash except when the resolved pathname 257 * is a single "/". 258 */ 259 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 260 resolved[resolved_len - 1] = '\0'; 261 return (resolved); 262} 263