1// SPDX-License-Identifier: LGPL-2.1
2/*
3 *   SPNEGO upcall management for CIFS
4 *
5 *   Copyright (c) 2007 Red Hat, Inc.
6 *   Author(s): Jeff Layton (jlayton@redhat.com)
7 *
8 */
9
10#include <linux/list.h>
11#include <linux/slab.h>
12#include <linux/string.h>
13#include <keys/user-type.h>
14#include <linux/key-type.h>
15#include <linux/keyctl.h>
16#include <linux/inet.h>
17#include "cifsglob.h"
18#include "cifs_spnego.h"
19#include "cifs_debug.h"
20#include "cifsproto.h"
21static const struct cred *spnego_cred;
22
23/* create a new cifs key */
24static int
25cifs_spnego_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
26{
27	char *payload;
28	int ret;
29
30	ret = -ENOMEM;
31	payload = kmemdup(prep->data, prep->datalen, GFP_KERNEL);
32	if (!payload)
33		goto error;
34
35	/* attach the data */
36	key->payload.data[0] = payload;
37	ret = 0;
38
39error:
40	return ret;
41}
42
43static void
44cifs_spnego_key_destroy(struct key *key)
45{
46	kfree(key->payload.data[0]);
47}
48
49
50/*
51 * keytype for CIFS spnego keys
52 */
53struct key_type cifs_spnego_key_type = {
54	.name		= "cifs.spnego",
55	.instantiate	= cifs_spnego_key_instantiate,
56	.destroy	= cifs_spnego_key_destroy,
57	.describe	= user_describe,
58};
59
60/* length of longest version string e.g.  strlen("ver=0xFF") */
61#define MAX_VER_STR_LEN		8
62
63/* length of longest security mechanism name, eg in future could have
64 * strlen(";sec=ntlmsspi") */
65#define MAX_MECH_STR_LEN	13
66
67/* strlen of ";host=" */
68#define HOST_KEY_LEN		6
69
70/* strlen of ";ip4=" or ";ip6=" */
71#define IP_KEY_LEN		5
72
73/* strlen of ";uid=0x" */
74#define UID_KEY_LEN		7
75
76/* strlen of ";creduid=0x" */
77#define CREDUID_KEY_LEN		11
78
79/* strlen of ";user=" */
80#define USER_KEY_LEN		6
81
82/* strlen of ";pid=0x" */
83#define PID_KEY_LEN		7
84
85/* get a key struct with a SPNEGO security blob, suitable for session setup */
86struct key *
87cifs_get_spnego_key(struct cifs_ses *sesInfo,
88		    struct TCP_Server_Info *server)
89{
90	struct sockaddr_in *sa = (struct sockaddr_in *) &server->dstaddr;
91	struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *) &server->dstaddr;
92	char *description, *dp;
93	size_t desc_len;
94	struct key *spnego_key;
95	const char *hostname = server->hostname;
96	const struct cred *saved_cred;
97
98	/* length of fields (with semicolons): ver=0xyz ip4=ipaddress
99	   host=hostname sec=mechanism uid=0xFF user=username */
100	desc_len = MAX_VER_STR_LEN +
101		   HOST_KEY_LEN + strlen(hostname) +
102		   IP_KEY_LEN + INET6_ADDRSTRLEN +
103		   MAX_MECH_STR_LEN +
104		   UID_KEY_LEN + (sizeof(uid_t) * 2) +
105		   CREDUID_KEY_LEN + (sizeof(uid_t) * 2) +
106		   PID_KEY_LEN + (sizeof(pid_t) * 2) + 1;
107
108	if (sesInfo->user_name)
109		desc_len += USER_KEY_LEN + strlen(sesInfo->user_name);
110
111	spnego_key = ERR_PTR(-ENOMEM);
112	description = kzalloc(desc_len, GFP_KERNEL);
113	if (description == NULL)
114		goto out;
115
116	dp = description;
117	/* start with version and hostname portion of UNC string */
118	spnego_key = ERR_PTR(-EINVAL);
119	sprintf(dp, "ver=0x%x;host=%s;", CIFS_SPNEGO_UPCALL_VERSION,
120		hostname);
121	dp = description + strlen(description);
122
123	/* add the server address */
124	if (server->dstaddr.ss_family == AF_INET)
125		sprintf(dp, "ip4=%pI4", &sa->sin_addr);
126	else if (server->dstaddr.ss_family == AF_INET6)
127		sprintf(dp, "ip6=%pI6", &sa6->sin6_addr);
128	else
129		goto out;
130
131	dp = description + strlen(description);
132
133	/* for now, only sec=krb5 and sec=mskrb5 are valid */
134	if (server->sec_kerberos)
135		sprintf(dp, ";sec=krb5");
136	else if (server->sec_mskerberos)
137		sprintf(dp, ";sec=mskrb5");
138	else {
139		cifs_dbg(VFS, "unknown or missing server auth type, use krb5\n");
140		sprintf(dp, ";sec=krb5");
141	}
142
143	dp = description + strlen(description);
144	sprintf(dp, ";uid=0x%x",
145		from_kuid_munged(&init_user_ns, sesInfo->linux_uid));
146
147	dp = description + strlen(description);
148	sprintf(dp, ";creduid=0x%x",
149		from_kuid_munged(&init_user_ns, sesInfo->cred_uid));
150
151	if (sesInfo->user_name) {
152		dp = description + strlen(description);
153		sprintf(dp, ";user=%s", sesInfo->user_name);
154	}
155
156	dp = description + strlen(description);
157	sprintf(dp, ";pid=0x%x", current->pid);
158
159	cifs_dbg(FYI, "key description = %s\n", description);
160	saved_cred = override_creds(spnego_cred);
161	spnego_key = request_key(&cifs_spnego_key_type, description, "");
162	revert_creds(saved_cred);
163
164#ifdef CONFIG_CIFS_DEBUG2
165	if (cifsFYI && !IS_ERR(spnego_key)) {
166		struct cifs_spnego_msg *msg = spnego_key->payload.data[0];
167		cifs_dump_mem("SPNEGO reply blob:", msg->data, min(1024U,
168				msg->secblob_len + msg->sesskey_len));
169	}
170#endif /* CONFIG_CIFS_DEBUG2 */
171
172out:
173	kfree(description);
174	return spnego_key;
175}
176
177int
178init_cifs_spnego(void)
179{
180	struct cred *cred;
181	struct key *keyring;
182	int ret;
183
184	cifs_dbg(FYI, "Registering the %s key type\n",
185		 cifs_spnego_key_type.name);
186
187	/*
188	 * Create an override credential set with special thread keyring for
189	 * spnego upcalls.
190	 */
191
192	cred = prepare_kernel_cred(&init_task);
193	if (!cred)
194		return -ENOMEM;
195
196	keyring = keyring_alloc(".cifs_spnego",
197				GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
198				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
199				KEY_USR_VIEW | KEY_USR_READ,
200				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
201	if (IS_ERR(keyring)) {
202		ret = PTR_ERR(keyring);
203		goto failed_put_cred;
204	}
205
206	ret = register_key_type(&cifs_spnego_key_type);
207	if (ret < 0)
208		goto failed_put_key;
209
210	/*
211	 * instruct request_key() to use this special keyring as a cache for
212	 * the results it looks up
213	 */
214	set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
215	cred->thread_keyring = keyring;
216	cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
217	spnego_cred = cred;
218
219	cifs_dbg(FYI, "cifs spnego keyring: %d\n", key_serial(keyring));
220	return 0;
221
222failed_put_key:
223	key_put(keyring);
224failed_put_cred:
225	put_cred(cred);
226	return ret;
227}
228
229void
230exit_cifs_spnego(void)
231{
232	key_revoke(spnego_cred->thread_keyring);
233	unregister_key_type(&cifs_spnego_key_type);
234	put_cred(spnego_cred);
235	cifs_dbg(FYI, "Unregistered %s key type\n", cifs_spnego_key_type.name);
236}
237