djm@openbsd.org | 569b650 | 2019-07-05 04:55:40 +0000 | [diff] [blame] | 1 | /* $OpenBSD: sftp-realpath.c,v 1.1 2019/07/05 04:55:40 djm 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 | |
Damien Miller | 53a6ebf | 2019-07-08 13:44:32 +1000 | [diff] [blame] | 30 | #include "includes.h" |
| 31 | |
djm@openbsd.org | 569b650 | 2019-07-05 04:55:40 +0000 | [diff] [blame] | 32 | #include <sys/types.h> |
| 33 | #include <sys/param.h> |
| 34 | #include <sys/stat.h> |
| 35 | |
| 36 | #include <errno.h> |
| 37 | #include <stdlib.h> |
| 38 | #include <stddef.h> |
| 39 | #include <string.h> |
| 40 | #include <unistd.h> |
| 41 | #include <limits.h> |
| 42 | |
| 43 | #ifndef SYMLOOP_MAX |
| 44 | # define SYMLOOP_MAX 32 |
| 45 | #endif |
| 46 | |
| 47 | /* XXX rewrite sftp-server to use POSIX realpath and remove this hack */ |
| 48 | |
| 49 | char *sftp_realpath(const char *path, char *resolved); |
| 50 | |
| 51 | /* |
| 52 | * char *realpath(const char *path, char resolved[PATH_MAX]); |
| 53 | * |
| 54 | * Find the real name of path, by removing all ".", ".." and symlink |
| 55 | * components. Returns (resolved) on success, or (NULL) on failure, |
| 56 | * in which case the path which caused trouble is left in (resolved). |
| 57 | */ |
| 58 | char * |
| 59 | sftp_realpath(const char *path, char *resolved) |
| 60 | { |
| 61 | struct stat sb; |
| 62 | char *p, *q, *s; |
| 63 | size_t left_len, resolved_len; |
| 64 | unsigned symlinks; |
| 65 | int serrno, slen, mem_allocated; |
| 66 | char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; |
| 67 | |
| 68 | if (path[0] == '\0') { |
| 69 | errno = ENOENT; |
| 70 | return (NULL); |
| 71 | } |
| 72 | |
| 73 | serrno = errno; |
| 74 | |
| 75 | if (resolved == NULL) { |
| 76 | resolved = malloc(PATH_MAX); |
| 77 | if (resolved == NULL) |
| 78 | return (NULL); |
| 79 | mem_allocated = 1; |
| 80 | } else |
| 81 | mem_allocated = 0; |
| 82 | |
| 83 | symlinks = 0; |
| 84 | if (path[0] == '/') { |
| 85 | resolved[0] = '/'; |
| 86 | resolved[1] = '\0'; |
| 87 | if (path[1] == '\0') |
| 88 | return (resolved); |
| 89 | resolved_len = 1; |
| 90 | left_len = strlcpy(left, path + 1, sizeof(left)); |
| 91 | } else { |
| 92 | if (getcwd(resolved, PATH_MAX) == NULL) { |
| 93 | if (mem_allocated) |
| 94 | free(resolved); |
| 95 | else |
| 96 | strlcpy(resolved, ".", PATH_MAX); |
| 97 | return (NULL); |
| 98 | } |
| 99 | resolved_len = strlen(resolved); |
| 100 | left_len = strlcpy(left, path, sizeof(left)); |
| 101 | } |
| 102 | if (left_len >= sizeof(left) || resolved_len >= PATH_MAX) { |
| 103 | errno = ENAMETOOLONG; |
| 104 | goto err; |
| 105 | } |
| 106 | |
| 107 | /* |
| 108 | * Iterate over path components in `left'. |
| 109 | */ |
| 110 | while (left_len != 0) { |
| 111 | /* |
| 112 | * Extract the next path component and adjust `left' |
| 113 | * and its length. |
| 114 | */ |
| 115 | p = strchr(left, '/'); |
| 116 | s = p ? p : left + left_len; |
| 117 | if (s - left >= (ptrdiff_t)sizeof(next_token)) { |
| 118 | errno = ENAMETOOLONG; |
| 119 | goto err; |
| 120 | } |
| 121 | memcpy(next_token, left, s - left); |
| 122 | next_token[s - left] = '\0'; |
| 123 | left_len -= s - left; |
| 124 | if (p != NULL) |
| 125 | memmove(left, s + 1, left_len + 1); |
| 126 | if (resolved[resolved_len - 1] != '/') { |
| 127 | if (resolved_len + 1 >= PATH_MAX) { |
| 128 | errno = ENAMETOOLONG; |
| 129 | goto err; |
| 130 | } |
| 131 | resolved[resolved_len++] = '/'; |
| 132 | resolved[resolved_len] = '\0'; |
| 133 | } |
| 134 | if (next_token[0] == '\0') |
| 135 | continue; |
| 136 | else if (strcmp(next_token, ".") == 0) |
| 137 | continue; |
| 138 | else if (strcmp(next_token, "..") == 0) { |
| 139 | /* |
| 140 | * Strip the last path component except when we have |
| 141 | * single "/" |
| 142 | */ |
| 143 | if (resolved_len > 1) { |
| 144 | resolved[resolved_len - 1] = '\0'; |
| 145 | q = strrchr(resolved, '/') + 1; |
| 146 | *q = '\0'; |
| 147 | resolved_len = q - resolved; |
| 148 | } |
| 149 | continue; |
| 150 | } |
| 151 | |
| 152 | /* |
| 153 | * Append the next path component and lstat() it. If |
| 154 | * lstat() fails we still can return successfully if |
| 155 | * there are no more path components left. |
| 156 | */ |
| 157 | resolved_len = strlcat(resolved, next_token, PATH_MAX); |
| 158 | if (resolved_len >= PATH_MAX) { |
| 159 | errno = ENAMETOOLONG; |
| 160 | goto err; |
| 161 | } |
| 162 | if (lstat(resolved, &sb) != 0) { |
| 163 | if (errno == ENOENT && p == NULL) { |
| 164 | errno = serrno; |
| 165 | return (resolved); |
| 166 | } |
| 167 | goto err; |
| 168 | } |
| 169 | if (S_ISLNK(sb.st_mode)) { |
| 170 | if (symlinks++ > SYMLOOP_MAX) { |
| 171 | errno = ELOOP; |
| 172 | goto err; |
| 173 | } |
| 174 | slen = readlink(resolved, symlink, sizeof(symlink) - 1); |
| 175 | if (slen < 0) |
| 176 | goto err; |
| 177 | symlink[slen] = '\0'; |
| 178 | if (symlink[0] == '/') { |
| 179 | resolved[1] = 0; |
| 180 | resolved_len = 1; |
| 181 | } else if (resolved_len > 1) { |
| 182 | /* Strip the last path component. */ |
| 183 | resolved[resolved_len - 1] = '\0'; |
| 184 | q = strrchr(resolved, '/') + 1; |
| 185 | *q = '\0'; |
| 186 | resolved_len = q - resolved; |
| 187 | } |
| 188 | |
| 189 | /* |
| 190 | * If there are any path components left, then |
| 191 | * append them to symlink. The result is placed |
| 192 | * in `left'. |
| 193 | */ |
| 194 | if (p != NULL) { |
| 195 | if (symlink[slen - 1] != '/') { |
| 196 | if (slen + 1 >= |
| 197 | (ptrdiff_t)sizeof(symlink)) { |
| 198 | errno = ENAMETOOLONG; |
| 199 | goto err; |
| 200 | } |
| 201 | symlink[slen] = '/'; |
| 202 | symlink[slen + 1] = 0; |
| 203 | } |
| 204 | left_len = strlcat(symlink, left, sizeof(symlink)); |
| 205 | if (left_len >= sizeof(symlink)) { |
| 206 | errno = ENAMETOOLONG; |
| 207 | goto err; |
| 208 | } |
| 209 | } |
| 210 | left_len = strlcpy(left, symlink, sizeof(left)); |
| 211 | } |
| 212 | } |
| 213 | |
| 214 | /* |
| 215 | * Remove trailing slash except when the resolved pathname |
| 216 | * is a single "/". |
| 217 | */ |
| 218 | if (resolved_len > 1 && resolved[resolved_len - 1] == '/') |
| 219 | resolved[resolved_len - 1] = '\0'; |
| 220 | return (resolved); |
| 221 | |
| 222 | err: |
| 223 | if (mem_allocated) |
| 224 | free(resolved); |
| 225 | return (NULL); |
| 226 | } |