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