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 * @(#)realpath.c 8.1 (Berkeley) 2/16/94 29 * $FreeBSD: head/lib/libc/stdlib/realpath.c 264417 2014-04-13 19:48:28Z jilles $ 30 */ 31 32 #include "namespace.h" 33 #include <sys/param.h> 34 #include <sys/stat.h> 35 36 #include <errno.h> 37 #include <stdlib.h> 38 #include <string.h> 39 #include <unistd.h> 40 #include "un-namespace.h" 41 42 /* 43 * Find the real name of path, by removing all ".", ".." and symlink 44 * components. Returns (resolved) on success, or (NULL) on failure, 45 * in which case the path which caused trouble is left in (resolved). 46 */ 47 char * 48 realpath(const char * __restrict path, char * __restrict resolved) 49 { 50 struct stat sb; 51 char *p, *q, *s; 52 size_t left_len, resolved_len; 53 unsigned symlinks; 54 int m, slen; 55 char left[PATH_MAX], next_token[PATH_MAX], my_symlink[PATH_MAX]; 56 57 if (path == NULL) { 58 errno = EINVAL; 59 return (NULL); 60 } 61 if (path[0] == '\0') { 62 errno = ENOENT; 63 return (NULL); 64 } 65 if (resolved == NULL) { 66 resolved = malloc(PATH_MAX); 67 if (resolved == NULL) 68 return (NULL); 69 m = 1; 70 } else 71 m = 0; 72 symlinks = 0; 73 if (path[0] == '/') { 74 resolved[0] = '/'; 75 resolved[1] = '\0'; 76 if (path[1] == '\0') 77 return (resolved); 78 resolved_len = 1; 79 left_len = strlcpy(left, path + 1, sizeof(left)); 80 } else { 81 if (getcwd(resolved, PATH_MAX) == NULL) { 82 if (m) 83 free(resolved); 84 else { 85 resolved[0] = '.'; 86 resolved[1] = '\0'; 87 } 88 return (NULL); 89 } 90 resolved_len = strlen(resolved); 91 left_len = strlcpy(left, path, sizeof(left)); 92 } 93 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 94 if (m) 95 free(resolved); 96 errno = ENAMETOOLONG; 97 return (NULL); 98 } 99 100 /* 101 * Iterate over path components in `left'. 102 */ 103 while (left_len != 0) { 104 /* 105 * Extract the next path component and adjust `left' 106 * and its length. 107 */ 108 p = strchr(left, '/'); 109 s = p ? p : left + left_len; 110 if (s - left >= sizeof(next_token)) { 111 if (m) 112 free(resolved); 113 errno = ENAMETOOLONG; 114 return (NULL); 115 } 116 memcpy(next_token, left, s - left); 117 next_token[s - left] = '\0'; 118 left_len -= s - left; 119 if (p != NULL) 120 memmove(left, s + 1, left_len + 1); 121 if (resolved[resolved_len - 1] != '/') { 122 if (resolved_len + 1 >= PATH_MAX) { 123 if (m) 124 free(resolved); 125 errno = ENAMETOOLONG; 126 return (NULL); 127 } 128 resolved[resolved_len++] = '/'; 129 resolved[resolved_len] = '\0'; 130 } 131 if (next_token[0] == '\0') { 132 /* Handle consequential slashes. */ 133 continue; 134 } else if (strcmp(next_token, ".") == 0) { 135 continue; 136 } else if (strcmp(next_token, "..") == 0) { 137 /* 138 * Strip the last path component except when we have 139 * single "/" 140 */ 141 if (resolved_len > 1) { 142 resolved[resolved_len - 1] = '\0'; 143 q = strrchr(resolved, '/') + 1; 144 *q = '\0'; 145 resolved_len = q - resolved; 146 } 147 continue; 148 } 149 150 /* 151 * Append the next path component and lstat() it. 152 */ 153 resolved_len = strlcat(resolved, next_token, PATH_MAX); 154 if (resolved_len >= PATH_MAX) { 155 if (m) 156 free(resolved); 157 errno = ENAMETOOLONG; 158 return (NULL); 159 } 160 if (lstat(resolved, &sb) != 0) { 161 if (m) 162 free(resolved); 163 return (NULL); 164 } 165 if (S_ISLNK(sb.st_mode)) { 166 if (symlinks++ > MAXSYMLINKS) { 167 if (m) 168 free(resolved); 169 errno = ELOOP; 170 return (NULL); 171 } 172 slen = readlink(resolved, my_symlink, sizeof(my_symlink) - 1); 173 if (slen < 0) { 174 if (m) 175 free(resolved); 176 return (NULL); 177 } 178 my_symlink[slen] = '\0'; 179 if (my_symlink[0] == '/') { 180 resolved[1] = 0; 181 resolved_len = 1; 182 } else if (resolved_len > 1) { 183 /* Strip the last path component. */ 184 resolved[resolved_len - 1] = '\0'; 185 q = strrchr(resolved, '/') + 1; 186 *q = '\0'; 187 resolved_len = q - resolved; 188 } 189 190 /* 191 * If there are any path components left, then 192 * append them to symlink. The result is placed 193 * in `left'. 194 */ 195 if (p != NULL) { 196 if (my_symlink[slen - 1] != '/') { 197 if (slen + 1 >= (int)sizeof(my_symlink)) { 198 if (m) 199 free(resolved); 200 errno = ENAMETOOLONG; 201 return (NULL); 202 } 203 my_symlink[slen] = '/'; 204 my_symlink[slen + 1] = 0; 205 } 206 left_len = strlcat(my_symlink, left, 207 sizeof(my_symlink)); 208 if (left_len >= sizeof(left)) { 209 if (m) 210 free(resolved); 211 errno = ENAMETOOLONG; 212 return (NULL); 213 } 214 } 215 left_len = strlcpy(left, my_symlink, sizeof(left)); 216 } else if (!S_ISDIR(sb.st_mode) && p != NULL) { 217 if (m) 218 free(resolved); 219 errno = ENOTDIR; 220 return (NULL); 221 } 222 } 223 224 /* 225 * Remove trailing slash except when the resolved pathname 226 * is a single "/". 227 */ 228 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 229 resolved[resolved_len - 1] = '\0'; 230 return (resolved); 231 } 232