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 */
30static 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 */
56static 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		if (PTR_ERR(res) == -ENAMETOOLONG)
98			return -ENAMETOOLONG;
99		connected = 0;
100		res = dentry_path_raw(path->dentry, buf, buflen);
101		if (IS_ERR(res)) {
102			error = PTR_ERR(res);
103			*name = buf;
104			goto out;
105		};
106	} else if (!our_mnt(path->mnt))
107		connected = 0;
108
109	*name = res;
110
111	/* Handle two cases:
112	 * 1. A deleted dentry && profile is not allowing mediation of deleted
113	 * 2. On some filesystems, newly allocated dentries appear to the
114	 *    security_path hooks as a deleted dentry except without an inode
115	 *    allocated.
116	 */
117	if (d_unlinked(path->dentry) && d_is_positive(path->dentry) &&
118	    !(flags & PATH_MEDIATE_DELETED)) {
119			error = -ENOENT;
120			goto out;
121	}
122
123	/* If the path is not connected to the expected root,
124	 * check if it is a sysctl and handle specially else remove any
125	 * leading / that __d_path may have returned.
126	 * Unless
127	 *     specifically directed to connect the path,
128	 * OR
129	 *     if in a chroot and doing chroot relative paths and the path
130	 *     resolves to the namespace root (would be connected outside
131	 *     of chroot) and specifically directed to connect paths to
132	 *     namespace root.
133	 */
134	if (!connected) {
135		if (!(flags & PATH_CONNECT_PATH) &&
136			   !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&
137			     our_mnt(path->mnt))) {
138			/* disconnected path, don't return pathname starting
139			 * with '/'
140			 */
141			error = -EACCES;
142			if (*res == '/')
143				*name = res + 1;
144		}
145	}
146
147out:
148	return error;
149}
150
151/**
152 * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
153 * @path: path to get name for  (NOT NULL)
154 * @flags: flags controlling path lookup
155 * @buffer: buffer to put name in  (NOT NULL)
156 * @size: size of buffer
157 * @name: Returns - contains position of path name in @buffer (NOT NULL)
158 *
159 * Returns: %0 else error on failure
160 */
161static int get_name_to_buffer(struct path *path, int flags, char *buffer,
162			      int size, char **name, const char **info)
163{
164	int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
165	int error = d_namespace_path(path, buffer, size - adjust, name, flags);
166
167	if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
168		/*
169		 * Append "/" to the pathname.  The root directory is a special
170		 * case; it already ends in slash.
171		 */
172		strcpy(&buffer[size - 2], "/");
173
174	if (info && error) {
175		if (error == -ENOENT)
176			*info = "Failed name lookup - deleted entry";
177		else if (error == -EACCES)
178			*info = "Failed name lookup - disconnected path";
179		else if (error == -ENAMETOOLONG)
180			*info = "Failed name lookup - name too long";
181		else
182			*info = "Failed name lookup";
183	}
184
185	return error;
186}
187
188/**
189 * aa_path_name - compute the pathname of a file
190 * @path: path the file  (NOT NULL)
191 * @flags: flags controlling path name generation
192 * @buffer: buffer that aa_get_name() allocated  (NOT NULL)
193 * @name: Returns - the generated path name if !error (NOT NULL)
194 * @info: Returns - information on why the path lookup failed (MAYBE NULL)
195 *
196 * @name is a pointer to the beginning of the pathname (which usually differs
197 * from the beginning of the buffer), or NULL.  If there is an error @name
198 * may contain a partial or invalid name that can be used for audit purposes,
199 * but it can not be used for mediation.
200 *
201 * We need PATH_IS_DIR to indicate whether the file is a directory or not
202 * because the file may not yet exist, and so we cannot check the inode's
203 * file type.
204 *
205 * Returns: %0 else error code if could retrieve name
206 */
207int aa_path_name(struct path *path, int flags, char **buffer, const char **name,
208		 const char **info)
209{
210	char *buf, *str = NULL;
211	int size = 256;
212	int error;
213
214	*name = NULL;
215	*buffer = NULL;
216	for (;;) {
217		/* freed by caller */
218		buf = kmalloc(size, GFP_KERNEL);
219		if (!buf)
220			return -ENOMEM;
221
222		error = get_name_to_buffer(path, flags, buf, size, &str, info);
223		if (error != -ENAMETOOLONG)
224			break;
225
226		kfree(buf);
227		size <<= 1;
228		if (size > aa_g_path_max)
229			return -ENAMETOOLONG;
230		*info = NULL;
231	}
232	*buffer = buf;
233	*name = str;
234
235	return error;
236}
237