1 /*
2 * AppArmor security module
3 *
4 * This file contains AppArmor function for pathnames
5 *
6 * Copyright (C) 1998-2008 Novell/SUSE
7 * Copyright 2009-2010 Canonical Ltd.
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation, version 2 of the
12 * License.
13 */
14
15 #include <linux/magic.h>
16 #include <linux/mount.h>
17 #include <linux/namei.h>
18 #include <linux/nsproxy.h>
19 #include <linux/path.h>
20 #include <linux/sched.h>
21 #include <linux/slab.h>
22 #include <linux/fs_struct.h>
23
24 #include "include/apparmor.h"
25 #include "include/path.h"
26 #include "include/policy.h"
27
28
29 /* modified from dcache.c */
prepend(char ** buffer,int buflen,const char * str,int namelen)30 static int prepend(char **buffer, int buflen, const char *str, int namelen)
31 {
32 buflen -= namelen;
33 if (buflen < 0)
34 return -ENAMETOOLONG;
35 *buffer -= namelen;
36 memcpy(*buffer, str, namelen);
37 return 0;
38 }
39
40 #define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
41
42 /**
43 * d_namespace_path - lookup a name associated with a given path
44 * @path: path to lookup (NOT NULL)
45 * @buf: buffer to store path to (NOT NULL)
46 * @buflen: length of @buf
47 * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
48 * @flags: flags controlling path lookup
49 *
50 * Handle path name lookup.
51 *
52 * Returns: %0 else error code if path lookup fails
53 * When no error the path name is returned in @name which points to
54 * to a position in @buf
55 */
d_namespace_path(struct path * path,char * buf,int buflen,char ** name,int flags)56 static int d_namespace_path(struct path *path, char *buf, int buflen,
57 char **name, int flags)
58 {
59 char *res;
60 int error = 0;
61 int connected = 1;
62
63 if (path->mnt->mnt_flags & MNT_INTERNAL) {
64 /* it's not mounted anywhere */
65 res = dentry_path(path->dentry, buf, buflen);
66 *name = res;
67 if (IS_ERR(res)) {
68 *name = buf;
69 return PTR_ERR(res);
70 }
71 if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
72 strncmp(*name, "/sys/", 5) == 0) {
73 /* TODO: convert over to using a per namespace
74 * control instead of hard coded /proc
75 */
76 return prepend(name, *name - buf, "/proc", 5);
77 }
78 return 0;
79 }
80
81 /* resolve paths relative to chroot?*/
82 if (flags & PATH_CHROOT_REL) {
83 struct path root;
84 get_fs_root(current->fs, &root);
85 res = __d_path(path, &root, buf, buflen);
86 path_put(&root);
87 } else {
88 res = d_absolute_path(path, buf, buflen);
89 if (!our_mnt(path->mnt))
90 connected = 0;
91 }
92
93 /* handle error conditions - and still allow a partial path to
94 * be returned.
95 */
96 if (!res || IS_ERR(res)) {
97 connected = 0;
98 res = dentry_path_raw(path->dentry, buf, buflen);
99 if (IS_ERR(res)) {
100 error = PTR_ERR(res);
101 *name = buf;
102 goto out;
103 };
104 } else if (!our_mnt(path->mnt))
105 connected = 0;
106
107 *name = res;
108
109 /* Handle two cases:
110 * 1. A deleted dentry && profile is not allowing mediation of deleted
111 * 2. On some filesystems, newly allocated dentries appear to the
112 * security_path hooks as a deleted dentry except without an inode
113 * allocated.
114 */
115 if (d_unlinked(path->dentry) && path->dentry->d_inode &&
116 !(flags & PATH_MEDIATE_DELETED)) {
117 error = -ENOENT;
118 goto out;
119 }
120
121 /* If the path is not connected to the expected root,
122 * check if it is a sysctl and handle specially else remove any
123 * leading / that __d_path may have returned.
124 * Unless
125 * specifically directed to connect the path,
126 * OR
127 * if in a chroot and doing chroot relative paths and the path
128 * resolves to the namespace root (would be connected outside
129 * of chroot) and specifically directed to connect paths to
130 * namespace root.
131 */
132 if (!connected) {
133 if (!(flags & PATH_CONNECT_PATH) &&
134 !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
135 our_mnt(path->mnt))) {
136 /* disconnected path, don't return pathname starting
137 * with '/'
138 */
139 error = -EACCES;
140 if (*res == '/')
141 *name = res + 1;
142 }
143 }
144
145 out:
146 return error;
147 }
148
149 /**
150 * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
151 * @path: path to get name for (NOT NULL)
152 * @flags: flags controlling path lookup
153 * @buffer: buffer to put name in (NOT NULL)
154 * @size: size of buffer
155 * @name: Returns - contains position of path name in @buffer (NOT NULL)
156 *
157 * Returns: %0 else error on failure
158 */
get_name_to_buffer(struct path * path,int flags,char * buffer,int size,char ** name,const char ** info)159 static int get_name_to_buffer(struct path *path, int flags, char *buffer,
160 int size, char **name, const char **info)
161 {
162 int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
163 int error = d_namespace_path(path, buffer, size - adjust, name, flags);
164
165 if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
166 /*
167 * Append "/" to the pathname. The root directory is a special
168 * case; it already ends in slash.
169 */
170 strcpy(&buffer[size - 2], "/");
171
172 if (info && error) {
173 if (error == -ENOENT)
174 *info = "Failed name lookup - deleted entry";
175 else if (error == -ESTALE)
176 *info = "Failed name lookup - disconnected path";
177 else if (error == -ENAMETOOLONG)
178 *info = "Failed name lookup - name too long";
179 else
180 *info = "Failed name lookup";
181 }
182
183 return error;
184 }
185
186 /**
187 * aa_path_name - compute the pathname of a file
188 * @path: path the file (NOT NULL)
189 * @flags: flags controlling path name generation
190 * @buffer: buffer that aa_get_name() allocated (NOT NULL)
191 * @name: Returns - the generated path name if !error (NOT NULL)
192 * @info: Returns - information on why the path lookup failed (MAYBE NULL)
193 *
194 * @name is a pointer to the beginning of the pathname (which usually differs
195 * from the beginning of the buffer), or NULL. If there is an error @name
196 * may contain a partial or invalid name that can be used for audit purposes,
197 * but it can not be used for mediation.
198 *
199 * We need PATH_IS_DIR to indicate whether the file is a directory or not
200 * because the file may not yet exist, and so we cannot check the inode's
201 * file type.
202 *
203 * Returns: %0 else error code if could retrieve name
204 */
aa_path_name(struct path * path,int flags,char ** buffer,const char ** name,const char ** info)205 int aa_path_name(struct path *path, int flags, char **buffer, const char **name,
206 const char **info)
207 {
208 char *buf, *str = NULL;
209 int size = 256;
210 int error;
211
212 *name = NULL;
213 *buffer = NULL;
214 for (;;) {
215 /* freed by caller */
216 buf = kmalloc(size, GFP_KERNEL);
217 if (!buf)
218 return -ENOMEM;
219
220 error = get_name_to_buffer(path, flags, buf, size, &str, info);
221 if (error != -ENAMETOOLONG)
222 break;
223
224 kfree(buf);
225 size <<= 1;
226 if (size > aa_g_path_max)
227 return -ENAMETOOLONG;
228 *info = NULL;
229 }
230 *buffer = buf;
231 *name = str;
232
233 return error;
234 }
235