1/**
2 * eCryptfs: Linux filesystem encryption layer
3 *
4 * Copyright (C) 2004-2006 International Business Machines Corp.
5 *   Author(s): Michael A. Halcrow <mhalcrow@us.ibm.com>
6 *		Tyler Hicks <tyhicks@ou.edu>
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License version
10 * 2 as published by the Free Software Foundation.
11 *
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
20 * 02111-1307, USA.
21 */
22
23#include <net/sock.h>
24#include <linux/hash.h>
25#include <linux/random.h>
26#include "ecryptfs_kernel.h"
27
28static struct sock *ecryptfs_nl_sock;
29
30/**
31 * ecryptfs_send_netlink
32 * @data: The data to include as the payload
33 * @data_len: The byte count of the data
34 * @msg_ctx: The netlink context that will be used to handle the
35 *          response message
36 * @msg_type: The type of netlink message to send
37 * @msg_flags: The flags to include in the netlink header
38 * @daemon_pid: The process id of the daemon to send the message to
39 *
40 * Sends the data to the specified daemon pid and uses the netlink
41 * context element to store the data needed for validation upon
42 * receiving the response.  The data and the netlink context can be
43 * null if just sending a netlink header is sufficient.  Returns zero
44 * upon sending the message; non-zero upon error.
45 */
46int ecryptfs_send_netlink(char *data, int data_len,
47			  struct ecryptfs_msg_ctx *msg_ctx, u16 msg_type,
48			  u16 msg_flags, pid_t daemon_pid)
49{
50	struct sk_buff *skb;
51	struct nlmsghdr *nlh;
52	struct ecryptfs_message *msg;
53	size_t payload_len;
54	int rc;
55
56	payload_len = ((data && data_len) ? (sizeof(*msg) + data_len) : 0);
57	skb = alloc_skb(NLMSG_SPACE(payload_len), GFP_KERNEL);
58	if (!skb) {
59		rc = -ENOMEM;
60		ecryptfs_printk(KERN_ERR, "Failed to allocate socket buffer\n");
61		goto out;
62	}
63	nlh = NLMSG_PUT(skb, daemon_pid, msg_ctx ? msg_ctx->counter : 0,
64			msg_type, payload_len);
65	nlh->nlmsg_flags = msg_flags;
66	if (msg_ctx && payload_len) {
67		msg = (struct ecryptfs_message *)NLMSG_DATA(nlh);
68		msg->index = msg_ctx->index;
69		msg->data_len = data_len;
70		memcpy(msg->data, data, data_len);
71	}
72	rc = netlink_unicast(ecryptfs_nl_sock, skb, daemon_pid, 0);
73	if (rc < 0) {
74		ecryptfs_printk(KERN_ERR, "Failed to send eCryptfs netlink "
75				"message; rc = [%d]\n", rc);
76		goto out;
77	}
78	rc = 0;
79	goto out;
80nlmsg_failure:
81	rc = -EMSGSIZE;
82	kfree_skb(skb);
83out:
84	return rc;
85}
86
87/**
88 * ecryptfs_process_nl_reponse
89 * @skb: The socket buffer containing the netlink message of state
90 *       RESPONSE
91 *
92 * Processes a response message after sending a operation request to
93 * userspace.  Attempts to assign the msg to a netlink context element
94 * at the index specified in the msg.  The sk_buff and nlmsghdr must
95 * be validated before this function. Returns zero upon delivery to
96 * desired context element; non-zero upon delivery failure or error.
97 */
98static int ecryptfs_process_nl_response(struct sk_buff *skb)
99{
100	struct nlmsghdr *nlh = nlmsg_hdr(skb);
101	struct ecryptfs_message *msg = NLMSG_DATA(nlh);
102	int rc;
103
104	if (skb->len - NLMSG_HDRLEN - sizeof(*msg) != msg->data_len) {
105		rc = -EINVAL;
106		ecryptfs_printk(KERN_ERR, "Received netlink message with "
107				"incorrectly specified data length\n");
108		goto out;
109	}
110	rc = ecryptfs_process_response(msg, NETLINK_CREDS(skb)->uid,
111				       NETLINK_CREDS(skb)->pid, nlh->nlmsg_seq);
112	if (rc)
113		printk(KERN_ERR
114		       "Error processing response message; rc = [%d]\n", rc);
115out:
116	return rc;
117}
118
119/**
120 * ecryptfs_process_nl_helo
121 * @skb: The socket buffer containing the nlmsghdr in HELO state
122 *
123 * Gets uid and pid of the skb and adds the values to the daemon id
124 * hash. Returns zero after adding a new daemon id to the hash list;
125 * non-zero otherwise.
126 */
127static int ecryptfs_process_nl_helo(struct sk_buff *skb)
128{
129	int rc;
130
131	rc = ecryptfs_process_helo(ECRYPTFS_TRANSPORT_NETLINK,
132				   NETLINK_CREDS(skb)->uid,
133				   NETLINK_CREDS(skb)->pid);
134	if (rc)
135		printk(KERN_WARNING "Error processing HELO; rc = [%d]\n", rc);
136	return rc;
137}
138
139/**
140 * ecryptfs_process_nl_quit
141 * @skb: The socket buffer containing the nlmsghdr in QUIT state
142 *
143 * Gets uid and pid of the skb and deletes the corresponding daemon
144 * id, if it is the registered that is requesting the
145 * deletion. Returns zero after deleting the desired daemon id;
146 * non-zero otherwise.
147 */
148static int ecryptfs_process_nl_quit(struct sk_buff *skb)
149{
150	int rc;
151
152	rc = ecryptfs_process_quit(NETLINK_CREDS(skb)->uid,
153				   NETLINK_CREDS(skb)->pid);
154	if (rc)
155		printk(KERN_WARNING
156		       "Error processing QUIT message; rc = [%d]\n", rc);
157	return rc;
158}
159
160/**
161 * ecryptfs_receive_nl_message
162 *
163 * Callback function called by netlink system when a message arrives.
164 * If the message looks to be valid, then an attempt is made to assign
165 * it to its desired netlink context element and wake up the process
166 * that is waiting for a response.
167 */
168static void ecryptfs_receive_nl_message(struct sock *sk, int len)
169{
170	struct sk_buff *skb;
171	struct nlmsghdr *nlh;
172	int rc = 0;	/* skb_recv_datagram requires this */
173
174receive:
175	skb = skb_recv_datagram(sk, 0, 0, &rc);
176	if (rc == -EINTR)
177		goto receive;
178	else if (rc < 0) {
179		ecryptfs_printk(KERN_ERR, "Error occurred while "
180				"receiving eCryptfs netlink message; "
181				"rc = [%d]\n", rc);
182		return;
183	}
184	nlh = nlmsg_hdr(skb);
185	if (!NLMSG_OK(nlh, skb->len)) {
186		ecryptfs_printk(KERN_ERR, "Received corrupt netlink "
187				"message\n");
188		goto free;
189	}
190	switch (nlh->nlmsg_type) {
191		case ECRYPTFS_NLMSG_RESPONSE:
192			if (ecryptfs_process_nl_response(skb)) {
193				ecryptfs_printk(KERN_WARNING, "Failed to "
194						"deliver netlink response to "
195						"requesting operation\n");
196			}
197			break;
198		case ECRYPTFS_NLMSG_HELO:
199			if (ecryptfs_process_nl_helo(skb)) {
200				ecryptfs_printk(KERN_WARNING, "Failed to "
201						"fulfill HELO request\n");
202			}
203			break;
204		case ECRYPTFS_NLMSG_QUIT:
205			if (ecryptfs_process_nl_quit(skb)) {
206				ecryptfs_printk(KERN_WARNING, "Failed to "
207						"fulfill QUIT request\n");
208			}
209			break;
210		default:
211			ecryptfs_printk(KERN_WARNING, "Dropping netlink "
212					"message of unrecognized type [%d]\n",
213					nlh->nlmsg_type);
214			break;
215	}
216free:
217	kfree_skb(skb);
218}
219
220/**
221 * ecryptfs_init_netlink
222 *
223 * Initializes the daemon id hash list, netlink context array, and
224 * necessary locks.  Returns zero upon success; non-zero upon error.
225 */
226int ecryptfs_init_netlink(void)
227{
228	int rc;
229
230	ecryptfs_nl_sock = netlink_kernel_create(NETLINK_ECRYPTFS, 0,
231						 ecryptfs_receive_nl_message,
232						 NULL, THIS_MODULE);
233	if (!ecryptfs_nl_sock) {
234		rc = -EIO;
235		ecryptfs_printk(KERN_ERR, "Failed to create netlink socket\n");
236		goto out;
237	}
238	ecryptfs_nl_sock->sk_sndtimeo = ECRYPTFS_DEFAULT_SEND_TIMEOUT;
239	rc = 0;
240out:
241	return rc;
242}
243
244/**
245 * ecryptfs_release_netlink
246 *
247 * Frees all memory used by the netlink context array and releases the
248 * netlink socket.
249 */
250void ecryptfs_release_netlink(void)
251{
252	if (ecryptfs_nl_sock && ecryptfs_nl_sock->sk_socket)
253		sock_release(ecryptfs_nl_sock->sk_socket);
254	ecryptfs_nl_sock = NULL;
255}
256