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 * $FreeBSD: src/lib/libc/stdlib/realpath.c SVN 227090 2011/11/04 ed $ 29 */ 30 31 #include "namespace.h" 32 #include <sys/param.h> 33 #include <sys/stat.h> 34 35 #include <errno.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <unistd.h> 39 #include "un-namespace.h" 40 41 /* 42 * Find the real name of path, by removing all ".", ".." and symlink 43 * components. Returns (resolved) on success, or (NULL) on failure, 44 * in which case the path which caused trouble is left in (resolved). 45 */ 46 char * 47 realpath(const char * __restrict path, char * __restrict resolved) 48 { 49 struct stat sb; 50 char *p, *q, *s; 51 size_t left_len, resolved_len; 52 unsigned symlinks; 53 int m, serrno, slen; 54 char left[PATH_MAX], next_token[PATH_MAX], my_symlink[PATH_MAX]; 55 56 if (path == NULL) { 57 errno = EINVAL; 58 return (NULL); 59 } 60 if (path[0] == '\0') { 61 errno = ENOENT; 62 return (NULL); 63 } 64 serrno = errno; 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 continue; 133 else if (strcmp(next_token, ".") == 0) 134 continue; 135 else if (strcmp(next_token, "..") == 0) { 136 /* 137 * Strip the last path component except when we have 138 * single "/" 139 */ 140 if (resolved_len > 1) { 141 resolved[resolved_len - 1] = '\0'; 142 q = strrchr(resolved, '/') + 1; 143 *q = '\0'; 144 resolved_len = q - resolved; 145 } 146 continue; 147 } 148 149 /* 150 * Append the next path component and lstat() it. If 151 * lstat() fails we still can return successfully if 152 * there are no more path components left. 153 */ 154 resolved_len = strlcat(resolved, next_token, PATH_MAX); 155 if (resolved_len >= PATH_MAX) { 156 if (m) 157 free(resolved); 158 errno = ENAMETOOLONG; 159 return (NULL); 160 } 161 if (lstat(resolved, &sb) != 0) { 162 if (errno == ENOENT && p == NULL) { 163 errno = serrno; 164 return (resolved); 165 } 166 if (m) 167 free(resolved); 168 return (NULL); 169 } 170 if (S_ISLNK(sb.st_mode)) { 171 if (symlinks++ > MAXSYMLINKS) { 172 if (m) 173 free(resolved); 174 errno = ELOOP; 175 return (NULL); 176 } 177 slen = readlink(resolved, my_symlink, sizeof(my_symlink) - 1); 178 if (slen < 0) { 179 if (m) 180 free(resolved); 181 return (NULL); 182 } 183 my_symlink[slen] = '\0'; 184 if (my_symlink[0] == '/') { 185 resolved[1] = 0; 186 resolved_len = 1; 187 } else if (resolved_len > 1) { 188 /* Strip the last path component. */ 189 resolved[resolved_len - 1] = '\0'; 190 q = strrchr(resolved, '/') + 1; 191 *q = '\0'; 192 resolved_len = q - resolved; 193 } 194 195 /* 196 * If there are any path components left, then 197 * append them to symlink. The result is placed 198 * in `left'. 199 */ 200 if (p != NULL) { 201 if (my_symlink[slen - 1] != '/') { 202 if (slen + 1 >= (int)sizeof(my_symlink)) { 203 if (m) 204 free(resolved); 205 errno = ENAMETOOLONG; 206 return (NULL); 207 } 208 my_symlink[slen] = '/'; 209 my_symlink[slen + 1] = 0; 210 } 211 left_len = strlcat(my_symlink, left, 212 sizeof(my_symlink)); 213 if (left_len >= sizeof(left)) { 214 if (m) 215 free(resolved); 216 errno = ENAMETOOLONG; 217 return (NULL); 218 } 219 } 220 left_len = strlcpy(left, my_symlink, sizeof(left)); 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