realpath.c revision 115362
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) 30static 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: head/lib/libc/stdlib/realpath.c 115362 2003-05-28 08:23:01Z fjoe $"); 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 * char *realpath(const char *path, char resolved[PATH_MAX]); 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 */ 52char * 53realpath(const char *path, char resolved[PATH_MAX]) 54{ 55 struct stat sb; 56 char *p, *q, *s; 57 size_t left_len, resolved_len; 58 unsigned symlinks; 59 int serrno, slen; 60 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; 61 62 serrno = errno; 63 symlinks = 0; 64 if (path[0] == '/') { 65 resolved[0] = '/'; 66 resolved[1] = '\0'; 67 if (path[1] == '\0') 68 return (resolved); 69 resolved_len = 1; 70 left_len = strlcpy(left, path + 1, sizeof(left)); 71 } else { 72 if (getcwd(resolved, PATH_MAX) == NULL) { 73 strlcpy(resolved, ".", PATH_MAX); 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 s = p ? p : left + left_len; 94 if (s - left >= sizeof(next_token)) { 95 errno = ENAMETOOLONG; 96 return (NULL); 97 } 98 memcpy(next_token, left, s - left); 99 next_token[s - left] = '\0'; 100 left_len -= s - left; 101 if (p != NULL) 102 memmove(left, s + 1, left_len + 1); 103 if (resolved[resolved_len - 1] != '/') { 104 if (resolved_len + 1 >= PATH_MAX) { 105 errno = ENAMETOOLONG; 106 return (NULL); 107 } 108 resolved[resolved_len++] = '/'; 109 resolved[resolved_len] = '\0'; 110 } 111 if (next_token[0] == '\0') 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. If 131 * lstat() fails we still can return successfully if 132 * there are no more path components left. 133 */ 134 resolved_len = strlcat(resolved, next_token, PATH_MAX); 135 if (resolved_len >= PATH_MAX) { 136 errno = ENAMETOOLONG; 137 return (NULL); 138 } 139 if (lstat(resolved, &sb) != 0) { 140 if (errno == ENOENT && p == NULL) { 141 errno = serrno; 142 return (resolved); 143 } 144 return (NULL); 145 } 146 if (S_ISLNK(sb.st_mode)) { 147 if (symlinks++ > MAXSYMLINKS) { 148 errno = ELOOP; 149 return (NULL); 150 } 151 slen = readlink(resolved, symlink, sizeof(symlink) - 1); 152 if (slen < 0) 153 return (NULL); 154 symlink[slen] = '\0'; 155 if (symlink[0] == '/') { 156 resolved[1] = 0; 157 resolved_len = 1; 158 } else if (resolved_len > 1) { 159 /* Strip the last path component. */ 160 resolved[resolved_len - 1] = '\0'; 161 q = strrchr(resolved, '/') + 1; 162 *q = '\0'; 163 resolved_len = q - resolved; 164 } 165 166 /* 167 * If there are any path components left, then 168 * append them to symlink. The result is placed 169 * in `left'. 170 */ 171 if (p != NULL) { 172 if (symlink[slen - 1] != '/') { 173 if (slen + 1 >= sizeof(symlink)) { 174 errno = ENAMETOOLONG; 175 return (NULL); 176 } 177 symlink[slen] = '/'; 178 symlink[slen + 1] = 0; 179 } 180 left_len = strlcat(symlink, left, sizeof(left)); 181 if (left_len >= sizeof(left)) { 182 errno = ENAMETOOLONG; 183 return (NULL); 184 } 185 } 186 left_len = strlcpy(left, symlink, sizeof(left)); 187 } 188 } 189 190 /* 191 * Remove trailing slash except when the resolved pathname 192 * is a single "/". 193 */ 194 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 195 resolved[resolved_len - 1] = '\0'; 196 return (resolved); 197} 198