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; 55 size_t left_len, resolved_len, next_token_len; 56 unsigned symlinks; 57 int m; 58 ssize_t slen; 59 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; 60 61 if (path == NULL) { 62 errno = EINVAL; 63 return (NULL); 64 } 65 if (path[0] == '\0') { 66 errno = ENOENT; 67 return (NULL); 68 } 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, '/'); 113 114 next_token_len = p ? p - left : left_len; 115 memcpy(next_token, left, next_token_len); 116 next_token[next_token_len] = '\0'; 117 118 if (p != NULL) { 119 left_len -= next_token_len + 1; 120 memmove(left, p + 1, left_len + 1); 121 } else { 122 left[0] = '\0'; 123 left_len = 0; 124 } 125 126 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 /* Handle consequential slashes. */ 138 continue; 139 } 140 else if (strcmp(next_token, ".") == 0) 141 continue; 142 else if (strcmp(next_token, "..") == 0) { 143 /* 144 * Strip the last path component except when we have 145 * single "/" 146 */ 147 if (resolved_len > 1) { 148 resolved[resolved_len - 1] = '\0'; 149 q = strrchr(resolved, '/') + 1; 150 *q = '\0'; 151 resolved_len = q - resolved; 152 } 153 continue; 154 } 155 156 /* 157 * Append the next path component and lstat() it. 158 */ 159 resolved_len = strlcat(resolved, next_token, PATH_MAX); 160 if (resolved_len >= PATH_MAX) { 161 if (m) 162 free(resolved); 163 errno = ENAMETOOLONG; 164 return (NULL); 165 } 166 if (lstat(resolved, &sb) != 0) { 167 if (m) 168 free(resolved); 169 return (NULL); 170 } 171 if (S_ISLNK(sb.st_mode)) { 172 if (symlinks++ > MAXSYMLINKS) { 173 if (m) 174 free(resolved); 175 errno = ELOOP; 176 return (NULL); 177 } 178 slen = readlink(resolved, symlink, sizeof(symlink)); 179 if (slen <= 0 || slen >= sizeof(symlink)) { 180 if (m) 181 free(resolved); 182 if (slen < 0) { 183 /* keep errno from readlink(2) call */ 184 } else if (slen == 0) { 185 errno = ENOENT; 186 } else { 187 errno = ENAMETOOLONG; 188 } 189 return (NULL); 190 } 191 symlink[slen] = '\0'; 192 if (symlink[0] == '/') { 193 resolved[1] = 0; 194 resolved_len = 1; 195 } else { 196 /* Strip the last path component. */ 197 q = strrchr(resolved, '/') + 1; 198 *q = '\0'; 199 resolved_len = q - resolved; 200 } 201 202 /* 203 * If there are any path components left, then 204 * append them to symlink. The result is placed 205 * in `left'. 206 */ 207 if (p != NULL) { 208 if (symlink[slen - 1] != '/') { 209 if (slen + 1 >= sizeof(symlink)) { 210 if (m) 211 free(resolved); 212 errno = ENAMETOOLONG; 213 return (NULL); 214 } 215 symlink[slen] = '/'; 216 symlink[slen + 1] = 0; 217 } 218 left_len = strlcat(symlink, left, 219 sizeof(symlink)); 220 if (left_len >= sizeof(symlink)) { 221 if (m) 222 free(resolved); 223 errno = ENAMETOOLONG; 224 return (NULL); 225 } 226 } 227 left_len = strlcpy(left, symlink, sizeof(left)); 228 } else if (!S_ISDIR(sb.st_mode) && p != NULL) { 229 if (m) 230 free(resolved); 231 errno = ENOTDIR; 232 return (NULL); 233 } 234 } 235 236 /* 237 * Remove trailing slash except when the resolved pathname 238 * is a single "/". 239 */ 240 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 241 resolved[resolved_len - 1] = '\0'; 242 return (resolved); 243 } 244