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 #include <sys/param.h> 32 #include <sys/stat.h> 33 34 #include <errno.h> 35 #include <fcntl.h> 36 #include <libsys.h> 37 #include <stdlib.h> 38 #include <string.h> 39 #include <unistd.h> 40 #include <ssp/ssp.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 static char * __noinline 48 realpath1(const char *path, char *resolved) 49 { 50 struct stat sb; 51 char *p, *q; 52 size_t left_len, prev_len, resolved_len, next_token_len; 53 unsigned symlinks; 54 ssize_t slen; 55 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; 56 57 symlinks = 0; 58 if (path[0] == '/') { 59 resolved[0] = '/'; 60 resolved[1] = '\0'; 61 if (path[1] == '\0') 62 return (resolved); 63 resolved_len = 1; 64 left_len = strlcpy(left, path + 1, sizeof(left)); 65 } else { 66 if (getcwd(resolved, PATH_MAX) == NULL) { 67 resolved[0] = '.'; 68 resolved[1] = '\0'; 69 return (NULL); 70 } 71 resolved_len = strlen(resolved); 72 left_len = strlcpy(left, path, sizeof(left)); 73 } 74 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 75 errno = ENAMETOOLONG; 76 return (NULL); 77 } 78 79 /* 80 * Iterate over path components in `left'. 81 */ 82 while (left_len != 0) { 83 /* 84 * Extract the next path component and adjust `left' 85 * and its length. 86 */ 87 p = strchr(left, '/'); 88 89 next_token_len = p != NULL ? (size_t)(p - left) : left_len; 90 memcpy(next_token, left, next_token_len); 91 next_token[next_token_len] = '\0'; 92 93 if (p != NULL) { 94 left_len -= next_token_len + 1; 95 memmove(left, p + 1, left_len + 1); 96 } else { 97 left[0] = '\0'; 98 left_len = 0; 99 } 100 101 prev_len = resolved_len; 102 if (resolved[resolved_len - 1] != '/') { 103 if (resolved_len + 1 >= PATH_MAX) { 104 errno = ENAMETOOLONG; 105 return (NULL); 106 } 107 resolved[resolved_len++] = '/'; 108 resolved[resolved_len] = '\0'; 109 } 110 if (next_token[0] == '\0') { 111 /* Handle consequential slashes. */ 112 continue; 113 } else if (strcmp(next_token, ".") == 0) { 114 continue; 115 } else if (strcmp(next_token, "..") == 0) { 116 /* 117 * Strip the last path component except when we have 118 * single "/" 119 */ 120 if (resolved_len > 1) { 121 resolved[resolved_len - 1] = '\0'; 122 q = strrchr(resolved, '/') + 1; 123 *q = '\0'; 124 resolved_len = q - resolved; 125 } 126 continue; 127 } 128 129 /* 130 * Append the next path component and lstat() it. 131 */ 132 resolved_len = strlcat(resolved, next_token, PATH_MAX); 133 if (resolved_len >= PATH_MAX) { 134 errno = ENAMETOOLONG; 135 return (NULL); 136 } 137 if (lstat(resolved, &sb) != 0) { 138 /* 139 * EACCES means the parent directory is not 140 * readable, while ENOTDIR means the parent 141 * directory is not a directory. Rewind the path 142 * to correctly indicate where the error lies. 143 */ 144 if (errno == EACCES || errno == ENOTDIR) 145 resolved[prev_len] = '\0'; 146 return (NULL); 147 } 148 if (S_ISLNK(sb.st_mode)) { 149 if (symlinks++ > MAXSYMLINKS) { 150 errno = ELOOP; 151 return (NULL); 152 } 153 slen = readlink(resolved, symlink, sizeof(symlink)); 154 if (slen < 0) 155 return (NULL); 156 if (slen == 0) { 157 errno = ENOENT; 158 return (NULL); 159 } 160 if ((size_t)slen >= sizeof(symlink)) { 161 errno = ENAMETOOLONG; 162 return (NULL); 163 } 164 symlink[slen] = '\0'; 165 if (symlink[0] == '/') { 166 resolved[1] = 0; 167 resolved_len = 1; 168 } else { 169 /* Strip the last path component. */ 170 q = strrchr(resolved, '/') + 1; 171 *q = '\0'; 172 resolved_len = q - resolved; 173 } 174 175 /* 176 * If there are any path components left, then 177 * append them to symlink. The result is placed 178 * in `left'. 179 */ 180 if (p != NULL) { 181 if (symlink[slen - 1] != '/') { 182 if ((size_t)slen + 1 >= sizeof(symlink)) { 183 errno = ENAMETOOLONG; 184 return (NULL); 185 } 186 symlink[slen] = '/'; 187 symlink[slen + 1] = 0; 188 } 189 left_len = strlcat(symlink, left, 190 sizeof(symlink)); 191 if (left_len >= sizeof(symlink)) { 192 errno = ENAMETOOLONG; 193 return (NULL); 194 } 195 } 196 left_len = strlcpy(left, symlink, sizeof(left)); 197 } else if (!S_ISDIR(sb.st_mode) && p != NULL) { 198 errno = ENOTDIR; 199 return (NULL); 200 } 201 } 202 203 /* 204 * Remove trailing slash except when the resolved pathname 205 * is a single "/". 206 */ 207 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 208 resolved[resolved_len - 1] = '\0'; 209 return (resolved); 210 } 211 212 char * 213 __ssp_real(realpath)(const char * __restrict path, char * __restrict resolved) 214 { 215 char *m, *res; 216 217 if (path == NULL) { 218 errno = EINVAL; 219 return (NULL); 220 } 221 if (path[0] == '\0') { 222 errno = ENOENT; 223 return (NULL); 224 } 225 if (resolved != NULL) { 226 m = NULL; 227 } else { 228 m = resolved = malloc(PATH_MAX); 229 if (resolved == NULL) 230 return (NULL); 231 } 232 if (__sys___realpathat(AT_FDCWD, path, resolved, PATH_MAX, 0) == 0) { 233 return (resolved); 234 } 235 res = realpath1(path, resolved); 236 if (res == NULL) 237 free(m); 238 return (res); 239 } 240