1/* $OpenBSD: sftp-realpath.c,v 1.2 2021/09/02 21:03:54 deraadt Exp $ */ 2/* 3 * Copyright (c) 2003 Constantin S. Svintsoff <kostik@iclub.nsu.ru> 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. The names of the authors may not be used to endorse or promote 14 * products derived from this software without specific prior written 15 * permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30#include "includes.h" 31 32#include <sys/types.h> 33#include <sys/stat.h> 34 35#include <errno.h> 36#include <stdlib.h> 37#include <stddef.h> 38#include <string.h> 39#include <unistd.h> 40#include <limits.h> 41 42#ifndef SYMLOOP_MAX 43# define SYMLOOP_MAX 32 44#endif 45 46/* XXX rewrite sftp-server to use POSIX realpath and remove this hack */ 47 48char *sftp_realpath(const char *path, char *resolved); 49 50/* 51 * char *realpath(const char *path, char resolved[PATH_MAX]); 52 * 53 * Find the real name of path, by removing all ".", ".." and symlink 54 * components. Returns (resolved) on success, or (NULL) on failure, 55 * in which case the path which caused trouble is left in (resolved). 56 */ 57char * 58sftp_realpath(const char *path, char *resolved) 59{ 60 struct stat sb; 61 char *p, *q, *s; 62 size_t left_len, resolved_len; 63 unsigned symlinks; 64 int serrno, slen, mem_allocated; 65 char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; 66 67 if (path[0] == '\0') { 68 errno = ENOENT; 69 return (NULL); 70 } 71 72 serrno = errno; 73 74 if (resolved == NULL) { 75 resolved = malloc(PATH_MAX); 76 if (resolved == NULL) 77 return (NULL); 78 mem_allocated = 1; 79 } else 80 mem_allocated = 0; 81 82 symlinks = 0; 83 if (path[0] == '/') { 84 resolved[0] = '/'; 85 resolved[1] = '\0'; 86 if (path[1] == '\0') 87 return (resolved); 88 resolved_len = 1; 89 left_len = strlcpy(left, path + 1, sizeof(left)); 90 } else { 91 if (getcwd(resolved, PATH_MAX) == NULL) { 92 if (mem_allocated) 93 free(resolved); 94 else 95 strlcpy(resolved, ".", PATH_MAX); 96 return (NULL); 97 } 98 resolved_len = strlen(resolved); 99 left_len = strlcpy(left, path, sizeof(left)); 100 } 101 if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { 102 errno = ENAMETOOLONG; 103 goto err; 104 } 105 106 /* 107 * Iterate over path components in `left'. 108 */ 109 while (left_len != 0) { 110 /* 111 * Extract the next path component and adjust `left' 112 * and its length. 113 */ 114 p = strchr(left, '/'); 115 s = p ? p : left + left_len; 116 if (s - left >= (ptrdiff_t)sizeof(next_token)) { 117 errno = ENAMETOOLONG; 118 goto err; 119 } 120 memcpy(next_token, left, s - left); 121 next_token[s - left] = '\0'; 122 left_len -= s - left; 123 if (p != NULL) 124 memmove(left, s + 1, left_len + 1); 125 if (resolved[resolved_len - 1] != '/') { 126 if (resolved_len + 1 >= PATH_MAX) { 127 errno = ENAMETOOLONG; 128 goto err; 129 } 130 resolved[resolved_len++] = '/'; 131 resolved[resolved_len] = '\0'; 132 } 133 if (next_token[0] == '\0') 134 continue; 135 else if (strcmp(next_token, ".") == 0) 136 continue; 137 else if (strcmp(next_token, "..") == 0) { 138 /* 139 * Strip the last path component except when we have 140 * single "/" 141 */ 142 if (resolved_len > 1) { 143 resolved[resolved_len - 1] = '\0'; 144 q = strrchr(resolved, '/') + 1; 145 *q = '\0'; 146 resolved_len = q - resolved; 147 } 148 continue; 149 } 150 151 /* 152 * Append the next path component and lstat() it. If 153 * lstat() fails we still can return successfully if 154 * there are no more path components left. 155 */ 156 resolved_len = strlcat(resolved, next_token, PATH_MAX); 157 if (resolved_len >= PATH_MAX) { 158 errno = ENAMETOOLONG; 159 goto err; 160 } 161 if (lstat(resolved, &sb) != 0) { 162 if (errno == ENOENT && p == NULL) { 163 errno = serrno; 164 return (resolved); 165 } 166 goto err; 167 } 168 if (S_ISLNK(sb.st_mode)) { 169 if (symlinks++ > SYMLOOP_MAX) { 170 errno = ELOOP; 171 goto err; 172 } 173 slen = readlink(resolved, symlink, sizeof(symlink) - 1); 174 if (slen < 0) 175 goto err; 176 symlink[slen] = '\0'; 177 if (symlink[0] == '/') { 178 resolved[1] = 0; 179 resolved_len = 1; 180 } else if (resolved_len > 1) { 181 /* Strip the last path component. */ 182 resolved[resolved_len - 1] = '\0'; 183 q = strrchr(resolved, '/') + 1; 184 *q = '\0'; 185 resolved_len = q - resolved; 186 } 187 188 /* 189 * If there are any path components left, then 190 * append them to symlink. The result is placed 191 * in `left'. 192 */ 193 if (p != NULL) { 194 if (symlink[slen - 1] != '/') { 195 if (slen + 1 >= 196 (ptrdiff_t)sizeof(symlink)) { 197 errno = ENAMETOOLONG; 198 goto err; 199 } 200 symlink[slen] = '/'; 201 symlink[slen + 1] = 0; 202 } 203 left_len = strlcat(symlink, left, sizeof(symlink)); 204 if (left_len >= sizeof(symlink)) { 205 errno = ENAMETOOLONG; 206 goto err; 207 } 208 } 209 left_len = strlcpy(left, symlink, sizeof(left)); 210 } 211 } 212 213 /* 214 * Remove trailing slash except when the resolved pathname 215 * is a single "/". 216 */ 217 if (resolved_len > 1 && resolved[resolved_len - 1] == '/') 218 resolved[resolved_len - 1] = '\0'; 219 return (resolved); 220 221err: 222 if (mem_allocated) 223 free(resolved); 224 return (NULL); 225} 226