1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru> 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. The names of the authors may not be used to endorse or promote 15 * products derived from this software without specific prior written 16 * permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #if defined(LIBC_SCCS) && !defined(lint) 32 static char sccsid[] = "@(#)realpath.c 8.1 (Berkeley) 2/16/94"; 33 #endif /* LIBC_SCCS and not lint */ 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "namespace.h" 38 #include <sys/param.h> 39 #include <sys/stat.h> 40 41 #include <errno.h> 42 #include <stdlib.h> 43 #include <string.h> 44 #include <unistd.h> 45 #include "un-namespace.h" 46 47 /* 48 * Find the real name of path, by removing all ".", ".." and symlink 49 * components. Returns (resolved) on success, or (NULL) on failure, 50 * in which case the path which caused trouble is left in (resolved). 51 */ 52 static char * 53 realpath1(const char *path, char *resolved) 54 { 55 struct stat sb; 56 char *p, *q; 57 size_t left_len, resolved_len, next_token_len; 58 unsigned symlinks; 59 ssize_t slen; 60 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; 61 62 symlinks = 0; 63 if (path[0] == '/') { 64 resolved[0] = '/'; 65 resolved[1] = '\0'; 66 if (path[1] == '\0') 67 return (resolved); 68 resolved_len = 1; 69 left_len = strlcpy(left, path + 1, sizeof(left)); 70 } else { 71 if (getcwd(resolved, PATH_MAX) == NULL) { 72 resolved[0] = '.'; 73 resolved[1] = '\0'; 74 return (NULL); 75 } 76 resolved_len = strlen(resolved); 77 left_len = strlcpy(left, path, sizeof(left)); 78 } 79 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 80 errno = ENAMETOOLONG; 81 return (NULL); 82 } 83 84 /* 85 * Iterate over path components in `left'. 86 */ 87 while (left_len != 0) { 88 /* 89 * Extract the next path component and adjust `left' 90 * and its length. 91 */ 92 p = strchr(left, '/'); 93 94 next_token_len = p != NULL ? p - left : left_len; 95 memcpy(next_token, left, next_token_len); 96 next_token[next_token_len] = '\0'; 97 98 if (p != NULL) { 99 left_len -= next_token_len + 1; 100 memmove(left, p + 1, left_len + 1); 101 } else { 102 left[0] = '\0'; 103 left_len = 0; 104 } 105 106 if (resolved[resolved_len - 1] != '/') { 107 if (resolved_len + 1 >= PATH_MAX) { 108 errno = ENAMETOOLONG; 109 return (NULL); 110 } 111 resolved[resolved_len++] = '/'; 112 resolved[resolved_len] = '\0'; 113 } 114 if (next_token[0] == '\0') { 115 /* Handle consequential slashes. */ 116 continue; 117 } else if (strcmp(next_token, ".") == 0) { 118 continue; 119 } else if (strcmp(next_token, "..") == 0) { 120 /* 121 * Strip the last path component except when we have 122 * single "/" 123 */ 124 if (resolved_len > 1) { 125 resolved[resolved_len - 1] = '\0'; 126 q = strrchr(resolved, '/') + 1; 127 *q = '\0'; 128 resolved_len = q - resolved; 129 } 130 continue; 131 } 132 133 /* 134 * Append the next path component and lstat() it. 135 */ 136 resolved_len = strlcat(resolved, next_token, PATH_MAX); 137 if (resolved_len >= PATH_MAX) { 138 errno = ENAMETOOLONG; 139 return (NULL); 140 } 141 if (lstat(resolved, &sb) != 0) 142 return (NULL); 143 if (S_ISLNK(sb.st_mode)) { 144 if (symlinks++ > MAXSYMLINKS) { 145 errno = ELOOP; 146 return (NULL); 147 } 148 slen = readlink(resolved, symlink, sizeof(symlink)); 149 if (slen <= 0 || slen >= sizeof(symlink)) { 150 if (slen < 0) 151 ; /* keep errno from readlink(2) call */ 152 else if (slen == 0) 153 errno = ENOENT; 154 else 155 errno = ENAMETOOLONG; 156 return (NULL); 157 } 158 symlink[slen] = '\0'; 159 if (symlink[0] == '/') { 160 resolved[1] = 0; 161 resolved_len = 1; 162 } else { 163 /* Strip the last path component. */ 164 q = strrchr(resolved, '/') + 1; 165 *q = '\0'; 166 resolved_len = q - resolved; 167 } 168 169 /* 170 * If there are any path components left, then 171 * append them to symlink. The result is placed 172 * in `left'. 173 */ 174 if (p != NULL) { 175 if (symlink[slen - 1] != '/') { 176 if (slen + 1 >= sizeof(symlink)) { 177 errno = ENAMETOOLONG; 178 return (NULL); 179 } 180 symlink[slen] = '/'; 181 symlink[slen + 1] = 0; 182 } 183 left_len = strlcat(symlink, left, 184 sizeof(symlink)); 185 if (left_len >= sizeof(symlink)) { 186 errno = ENAMETOOLONG; 187 return (NULL); 188 } 189 } 190 left_len = strlcpy(left, symlink, sizeof(left)); 191 } else if (!S_ISDIR(sb.st_mode) && p != NULL) { 192 errno = ENOTDIR; 193 return (NULL); 194 } 195 } 196 197 /* 198 * Remove trailing slash except when the resolved pathname 199 * is a single "/". 200 */ 201 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 202 resolved[resolved_len - 1] = '\0'; 203 return (resolved); 204 } 205 206 char * 207 realpath(const char * __restrict path, char * __restrict resolved) 208 { 209 char *m, *res; 210 211 if (path == NULL) { 212 errno = EINVAL; 213 return (NULL); 214 } 215 if (path[0] == '\0') { 216 errno = ENOENT; 217 return (NULL); 218 } 219 if (resolved != NULL) { 220 m = NULL; 221 } else { 222 m = resolved = malloc(PATH_MAX); 223 if (resolved == NULL) 224 return (NULL); 225 } 226 res = realpath1(path, resolved); 227 if (res == NULL) 228 free(m); 229 return (res); 230 } 231