xref: /linux/fs/smb/client/cifs_spnego.c (revision 0ea5c948cb64bab5bc7a5516774eb8536f05aa0d)
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"
21 static const struct cred *spnego_cred;
22 
23 /* create a new cifs key */
24 static int
cifs_spnego_key_instantiate(struct key * key,struct key_preparsed_payload * prep)25 cifs_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 
39 error:
40 	return ret;
41 }
42 
43 static void
cifs_spnego_key_destroy(struct key * key)44 cifs_spnego_key_destroy(struct key *key)
45 {
46 	kfree(key->payload.data[0]);
47 }
48 
49 
50 /*
51  * keytype for CIFS spnego keys
52  */
53 struct 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 */
86 struct key *
cifs_get_spnego_key(struct cifs_ses * sesInfo,struct TCP_Server_Info * server)87 cifs_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 
172 out:
173 	kfree(description);
174 	return spnego_key;
175 }
176 
177 int
init_cifs_spnego(void)178 init_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 
222 failed_put_key:
223 	key_put(keyring);
224 failed_put_cred:
225 	put_cred(cred);
226 	return ret;
227 }
228 
229 void
exit_cifs_spnego(void)230 exit_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