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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/mnt_namespace.h>
17#include <linux/mount.h>
18#include <linux/namei.h>
19#include <linux/nsproxy.h>
20#include <linux/path.h>
21#include <linux/sched.h>
22#include <linux/slab.h>
23#include <linux/fs_struct.h>
24
25#include "include/apparmor.h"
26#include "include/path.h"
27#include "include/policy.h"
28
29
30/* modified from dcache.c */
31static int prepend(char **buffer, int buflen, const char *str, int namelen)
32{
33 buflen -= namelen;
34 if (buflen < 0)
35 return -ENAMETOOLONG;
36 *buffer -= namelen;
37 memcpy(*buffer, str, namelen);
38 return 0;
39}
40
41#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
42
43/**
44 * d_namespace_path - lookup a name associated with a given path
45 * @path: path to lookup (NOT NULL)
46 * @buf: buffer to store path to (NOT NULL)
47 * @buflen: length of @buf
48 * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
49 * @flags: flags controlling path lookup
50 *
51 * Handle path name lookup.
52 *
53 * Returns: %0 else error code if path lookup fails
54 * When no error the path name is returned in @name which points to
55 * to a position in @buf
56 */
57static int d_namespace_path(struct path *path, char *buf, int buflen,
58 char **name, int flags)
59{
60 struct path root, tmp;
61 char *res;
62 int connected, error = 0;
63
64 /* Get the root we want to resolve too, released below */
65 if (flags & PATH_CHROOT_REL) {
66 /* resolve paths relative to chroot */
67 get_fs_root(current->fs, &root);
68 } else {
69 /* resolve paths relative to namespace */
70 root.mnt = current->nsproxy->mnt_ns->root;
71 root.dentry = root.mnt->mnt_root;
72 path_get(&root);
73 }
74
75 tmp = root;
76 res = __d_path(path, &tmp, buf, buflen);
77
78 *name = res;
79 /* handle error conditions - and still allow a partial path to
80 * be returned.
81 */
82 if (IS_ERR(res)) {
83 error = PTR_ERR(res);
84 *name = buf;
85 goto out;
86 }
87
88 /* Handle two cases:
89 * 1. A deleted dentry && profile is not allowing mediation of deleted
90 * 2. On some filesystems, newly allocated dentries appear to the
91 * security_path hooks as a deleted dentry except without an inode
92 * allocated.
93 */
94 if (d_unlinked(path->dentry) && path->dentry->d_inode &&
95 !(flags & PATH_MEDIATE_DELETED)) {
96 error = -ENOENT;
97 goto out;
98 }
99
100 /* Determine if the path is connected to the expected root */
101 connected = tmp.dentry == root.dentry && tmp.mnt == root.mnt;
102
103 /* If the path is not connected,
104 * check if it is a sysctl and handle specially else remove any
105 * leading / that __d_path may have returned.
106 * Unless
107 * specifically directed to connect the path,
108 * OR
109 * if in a chroot and doing chroot relative paths and the path
110 * resolves to the namespace root (would be connected outside
111 * of chroot) and specifically directed to connect paths to
112 * namespace root.
113 */
114 if (!connected) {
115 /* is the disconnect path a sysctl? */
116 if (tmp.dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
117 strncmp(*name, "/sys/", 5) == 0) {
118 /* TODO: convert over to using a per namespace
119 * control instead of hard coded /proc
120 */
121 error = prepend(name, *name - buf, "/proc", 5);
122 } else if (!(flags & PATH_CONNECT_PATH) &&
123 !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
124 (tmp.mnt == current->nsproxy->mnt_ns->root &&
125 tmp.dentry == tmp.mnt->mnt_root))) {
126 /* disconnected path, don't return pathname starting
127 * with '/'
128 */
129 error = -ESTALE;
130 if (*res == '/')
131 *name = res + 1;
132 }
133 }
134
135out:
136 path_put(&root);
137
138 return error;
139}
140
141/**
142 * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
143 * @path: path to get name for (NOT NULL)
144 * @flags: flags controlling path lookup
145 * @buffer: buffer to put name in (NOT NULL)
146 * @size: size of buffer
147 * @name: Returns - contains position of path name in @buffer (NOT NULL)
148 *
149 * Returns: %0 else error on failure
150 */
151static int get_name_to_buffer(struct path *path, int flags, char *buffer,
152 int size, char **name)
153{
154 int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
155 int error = d_namespace_path(path, buffer, size - adjust, name, flags);
156
157 if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
158 /*
159 * Append "/" to the pathname. The root directory is a special
160 * case; it already ends in slash.
161 */
162 strcpy(&buffer[size - 2], "/");
163
164 return error;
165}
166
167/**
168 * aa_get_name - compute the pathname of a file
169 * @path: path the file (NOT NULL)
170 * @flags: flags controlling path name generation
171 * @buffer: buffer that aa_get_name() allocated (NOT NULL)
172 * @name: Returns - the generated path name if !error (NOT NULL)
173 *
174 * @name is a pointer to the beginning of the pathname (which usually differs
175 * from the beginning of the buffer), or NULL. If there is an error @name
176 * may contain a partial or invalid name that can be used for audit purposes,
177 * but it can not be used for mediation.
178 *
179 * We need PATH_IS_DIR to indicate whether the file is a directory or not
180 * because the file may not yet exist, and so we cannot check the inode's
181 * file type.
182 *
183 * Returns: %0 else error code if could retrieve name
184 */
185int aa_get_name(struct path *path, int flags, char **buffer, const char **name)
186{
187 char *buf, *str = NULL;
188 int size = 256;
189 int error;
190
191 *name = NULL;
192 *buffer = NULL;
193 for (;;) {
194 /* freed by caller */
195 buf = kmalloc(size, GFP_KERNEL);
196 if (!buf)
197 return -ENOMEM;
198
199 error = get_name_to_buffer(path, flags, buf, size, &str);
200 if (error != -ENAMETOOLONG)
201 break;
202
203 kfree(buf);
204 size <<= 1;
205 if (size > aa_g_path_max)
206 return -ENAMETOOLONG;
207 }
208 *buffer = buf;
209 *name = str;
210
211 return error;
212}
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/* modified from dcache.c */
29static int prepend(char **buffer, int buflen, const char *str, int namelen)
30{
31 buflen -= namelen;
32 if (buflen < 0)
33 return -ENAMETOOLONG;
34 *buffer -= namelen;
35 memcpy(*buffer, str, namelen);
36 return 0;
37}
38
39#define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
40
41/* If the path is not connected to the expected root,
42 * check if it is a sysctl and handle specially else remove any
43 * leading / that __d_path may have returned.
44 * Unless
45 * specifically directed to connect the path,
46 * OR
47 * if in a chroot and doing chroot relative paths and the path
48 * resolves to the namespace root (would be connected outside
49 * of chroot) and specifically directed to connect paths to
50 * namespace root.
51 */
52static int disconnect(const struct path *path, char *buf, char **name,
53 int flags)
54{
55 int error = 0;
56
57 if (!(flags & PATH_CONNECT_PATH) &&
58 !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
59 our_mnt(path->mnt))) {
60 /* disconnected path, don't return pathname starting
61 * with '/'
62 */
63 error = -EACCES;
64 if (**name == '/')
65 *name = *name + 1;
66 } else if (**name != '/')
67 /* CONNECT_PATH with missing root */
68 error = prepend(name, *name - buf, "/", 1);
69
70 return error;
71}
72
73/**
74 * d_namespace_path - lookup a name associated with a given path
75 * @path: path to lookup (NOT NULL)
76 * @buf: buffer to store path to (NOT NULL)
77 * @buflen: length of @buf
78 * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
79 * @flags: flags controlling path lookup
80 *
81 * Handle path name lookup.
82 *
83 * Returns: %0 else error code if path lookup fails
84 * When no error the path name is returned in @name which points to
85 * to a position in @buf
86 */
87static int d_namespace_path(const struct path *path, char *buf, int buflen,
88 char **name, int flags)
89{
90 char *res;
91 int error = 0;
92 int connected = 1;
93
94 if (path->mnt->mnt_flags & MNT_INTERNAL) {
95 /* it's not mounted anywhere */
96 res = dentry_path(path->dentry, buf, buflen);
97 *name = res;
98 if (IS_ERR(res)) {
99 *name = buf;
100 return PTR_ERR(res);
101 }
102 if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
103 strncmp(*name, "/sys/", 5) == 0) {
104 /* TODO: convert over to using a per namespace
105 * control instead of hard coded /proc
106 */
107 return prepend(name, *name - buf, "/proc", 5);
108 } else
109 return disconnect(path, buf, name, flags);
110 return 0;
111 }
112
113 /* resolve paths relative to chroot?*/
114 if (flags & PATH_CHROOT_REL) {
115 struct path root;
116 get_fs_root(current->fs, &root);
117 res = __d_path(path, &root, buf, buflen);
118 path_put(&root);
119 } else {
120 res = d_absolute_path(path, buf, buflen);
121 if (!our_mnt(path->mnt))
122 connected = 0;
123 }
124
125 /* handle error conditions - and still allow a partial path to
126 * be returned.
127 */
128 if (!res || IS_ERR(res)) {
129 if (PTR_ERR(res) == -ENAMETOOLONG)
130 return -ENAMETOOLONG;
131 connected = 0;
132 res = dentry_path_raw(path->dentry, buf, buflen);
133 if (IS_ERR(res)) {
134 error = PTR_ERR(res);
135 *name = buf;
136 goto out;
137 };
138 } else if (!our_mnt(path->mnt))
139 connected = 0;
140
141 *name = res;
142
143 /* Handle two cases:
144 * 1. A deleted dentry && profile is not allowing mediation of deleted
145 * 2. On some filesystems, newly allocated dentries appear to the
146 * security_path hooks as a deleted dentry except without an inode
147 * allocated.
148 */
149 if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
150 !(flags & PATH_MEDIATE_DELETED)) {
151 error = -ENOENT;
152 goto out;
153 }
154
155 if (!connected)
156 error = disconnect(path, buf, name, flags);
157
158out:
159 return error;
160}
161
162/**
163 * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
164 * @path: path to get name for (NOT NULL)
165 * @flags: flags controlling path lookup
166 * @buffer: buffer to put name in (NOT NULL)
167 * @size: size of buffer
168 * @name: Returns - contains position of path name in @buffer (NOT NULL)
169 *
170 * Returns: %0 else error on failure
171 */
172static int get_name_to_buffer(const struct path *path, int flags, char *buffer,
173 int size, char **name, const char **info)
174{
175 int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
176 int error = d_namespace_path(path, buffer, size - adjust, name, flags);
177
178 if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
179 /*
180 * Append "/" to the pathname. The root directory is a special
181 * case; it already ends in slash.
182 */
183 strcpy(&buffer[size - 2], "/");
184
185 if (info && error) {
186 if (error == -ENOENT)
187 *info = "Failed name lookup - deleted entry";
188 else if (error == -EACCES)
189 *info = "Failed name lookup - disconnected path";
190 else if (error == -ENAMETOOLONG)
191 *info = "Failed name lookup - name too long";
192 else
193 *info = "Failed name lookup";
194 }
195
196 return error;
197}
198
199/**
200 * aa_path_name - compute the pathname of a file
201 * @path: path the file (NOT NULL)
202 * @flags: flags controlling path name generation
203 * @buffer: buffer that aa_get_name() allocated (NOT NULL)
204 * @name: Returns - the generated path name if !error (NOT NULL)
205 * @info: Returns - information on why the path lookup failed (MAYBE NULL)
206 *
207 * @name is a pointer to the beginning of the pathname (which usually differs
208 * from the beginning of the buffer), or NULL. If there is an error @name
209 * may contain a partial or invalid name that can be used for audit purposes,
210 * but it can not be used for mediation.
211 *
212 * We need PATH_IS_DIR to indicate whether the file is a directory or not
213 * because the file may not yet exist, and so we cannot check the inode's
214 * file type.
215 *
216 * Returns: %0 else error code if could retrieve name
217 */
218int aa_path_name(const struct path *path, int flags, char **buffer,
219 const char **name, const char **info)
220{
221 char *buf, *str = NULL;
222 int size = 256;
223 int error;
224
225 *name = NULL;
226 *buffer = NULL;
227 for (;;) {
228 /* freed by caller */
229 buf = kmalloc(size, GFP_KERNEL);
230 if (!buf)
231 return -ENOMEM;
232
233 error = get_name_to_buffer(path, flags, buf, size, &str, info);
234 if (error != -ENAMETOOLONG)
235 break;
236
237 kfree(buf);
238 size <<= 1;
239 if (size > aa_g_path_max)
240 return -ENAMETOOLONG;
241 *info = NULL;
242 }
243 *buffer = buf;
244 *name = str;
245
246 return error;
247}