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/cred.h>
12 #include <linux/slab.h>
13 #include <linux/string.h>
14 #include <keys/user-type.h>
15 #include <linux/key-type.h>
16 #include <linux/keyctl.h>
17 #include <linux/inet.h>
18 #include "cifsglob.h"
19 #include "cifs_spnego.h"
20 #include "cifs_debug.h"
21 #include "cifsproto.h"
22 static const struct cred *spnego_cred;
23
24 /* create a new cifs key */
25 static int
cifs_spnego_key_instantiate(struct key * key,struct key_preparsed_payload * prep)26 cifs_spnego_key_instantiate(struct key *key, struct key_preparsed_payload *prep)
27 {
28 char *payload = kmemdup(prep->data, prep->datalen, GFP_KERNEL);
29
30 if (!payload)
31 return -ENOMEM;
32
33 /* attach the data */
34 key->payload.data[0] = payload;
35 return 0;
36 }
37
38 static void
cifs_spnego_key_destroy(struct key * key)39 cifs_spnego_key_destroy(struct key *key)
40 {
41 kfree(key->payload.data[0]);
42 }
43
44 static int
cifs_spnego_key_vet_description(const char * description)45 cifs_spnego_key_vet_description(const char *description)
46 {
47 /*
48 * cifs.spnego descriptions are authority-bearing inputs to cifs.upcall.
49 * They are only valid when produced by CIFS while using the private
50 * spnego_cred installed below. Do not let userspace create this type
51 * of key through request_key(2)/add_key(2), since the helper treats
52 * pid/uid/creduid/upcall_target as kernel-originating fields.
53 */
54 if (current_cred() != spnego_cred)
55 return -EPERM;
56 return 0;
57 }
58
59 /*
60 * keytype for CIFS spnego keys
61 */
62 struct key_type cifs_spnego_key_type = {
63 .name = "cifs.spnego",
64 .vet_description = cifs_spnego_key_vet_description,
65 .instantiate = cifs_spnego_key_instantiate,
66 .destroy = cifs_spnego_key_destroy,
67 .describe = user_describe,
68 };
69
70 /* length of longest version string e.g. strlen("ver=0xFF") */
71 #define MAX_VER_STR_LEN 8
72
73 /* length of longest security mechanism name, eg in future could have
74 * strlen(";sec=ntlmsspi") */
75 #define MAX_MECH_STR_LEN 13
76
77 /* strlen of ";host=" */
78 #define HOST_KEY_LEN 6
79
80 /* strlen of ";ip4=" or ";ip6=" */
81 #define IP_KEY_LEN 5
82
83 /* strlen of ";uid=0x" */
84 #define UID_KEY_LEN 7
85
86 /* strlen of ";creduid=0x" */
87 #define CREDUID_KEY_LEN 11
88
89 /* strlen of ";user=" */
90 #define USER_KEY_LEN 6
91
92 /* strlen of ";pid=0x" */
93 #define PID_KEY_LEN 7
94
95 /* strlen of ";upcall_target=" */
96 #define UPCALL_TARGET_KEY_LEN 15
97
98 /* get a key struct with a SPNEGO security blob, suitable for session setup */
99 struct key *
cifs_get_spnego_key(struct cifs_ses * sesInfo,struct TCP_Server_Info * server)100 cifs_get_spnego_key(struct cifs_ses *sesInfo,
101 struct TCP_Server_Info *server)
102 {
103 struct sockaddr_in *sa = (struct sockaddr_in *) &server->dstaddr;
104 struct sockaddr_in6 *sa6 = (struct sockaddr_in6 *) &server->dstaddr;
105 char *description, *dp;
106 size_t desc_len;
107 struct key *spnego_key;
108 const char *hostname = server->hostname;
109
110 /* length of fields (with semicolons): ver=0xyz ip4=ipaddress
111 host=hostname sec=mechanism uid=0xFF user=username */
112 desc_len = MAX_VER_STR_LEN +
113 HOST_KEY_LEN + strlen(hostname) +
114 IP_KEY_LEN + INET6_ADDRSTRLEN +
115 MAX_MECH_STR_LEN +
116 UID_KEY_LEN + (sizeof(uid_t) * 2) +
117 CREDUID_KEY_LEN + (sizeof(uid_t) * 2) +
118 PID_KEY_LEN + (sizeof(pid_t) * 2) + 1;
119
120 if (sesInfo->user_name)
121 desc_len += USER_KEY_LEN + strlen(sesInfo->user_name);
122
123 if (sesInfo->upcall_target == UPTARGET_MOUNT)
124 desc_len += UPCALL_TARGET_KEY_LEN + 5; // strlen("mount")
125 else
126 desc_len += UPCALL_TARGET_KEY_LEN + 3; // strlen("app")
127
128 spnego_key = ERR_PTR(-ENOMEM);
129 description = kzalloc(desc_len, GFP_KERNEL);
130 if (description == NULL)
131 goto out;
132
133 dp = description;
134 /* start with version and hostname portion of UNC string */
135 spnego_key = ERR_PTR(-EINVAL);
136 dp += sprintf(dp, "ver=0x%x;host=%s;", CIFS_SPNEGO_UPCALL_VERSION,
137 hostname);
138
139 /* add the server address */
140 if (server->dstaddr.ss_family == AF_INET)
141 dp += sprintf(dp, "ip4=%pI4", &sa->sin_addr);
142 else if (server->dstaddr.ss_family == AF_INET6)
143 dp += sprintf(dp, "ip6=%pI6", &sa6->sin6_addr);
144 else
145 goto out;
146
147 /* for now, only sec=krb5 and sec=mskrb5 and iakerb are valid */
148 if (server->sec_kerberos)
149 dp += sprintf(dp, ";sec=krb5");
150 else if (server->sec_mskerberos)
151 dp += sprintf(dp, ";sec=mskrb5");
152 else if (server->sec_iakerb)
153 dp += sprintf(dp, ";sec=iakerb");
154 else {
155 cifs_dbg(VFS, "unknown or missing server auth type, use krb5\n");
156 dp += sprintf(dp, ";sec=krb5");
157 }
158
159 dp += sprintf(dp, ";uid=0x%x",
160 from_kuid_munged(&init_user_ns, sesInfo->linux_uid));
161
162 dp += sprintf(dp, ";creduid=0x%x",
163 from_kuid_munged(&init_user_ns, sesInfo->cred_uid));
164
165 if (sesInfo->user_name)
166 dp += sprintf(dp, ";user=%s", sesInfo->user_name);
167
168 dp += sprintf(dp, ";pid=0x%x", current->pid);
169
170 if (sesInfo->upcall_target == UPTARGET_MOUNT)
171 dp += sprintf(dp, ";upcall_target=mount");
172 else
173 dp += sprintf(dp, ";upcall_target=app");
174
175 cifs_dbg(FYI, "key description = %s\n", description);
176 scoped_with_creds(spnego_cred)
177 spnego_key = request_key(&cifs_spnego_key_type, description, "");
178 trace_smb3_kerberos_auth(server, sesInfo, PTR_ERR_OR_ZERO(spnego_key));
179
180 #ifdef CONFIG_CIFS_DEBUG2
181 if (cifsFYI && !IS_ERR(spnego_key)) {
182 struct cifs_spnego_msg *msg = spnego_key->payload.data[0];
183 cifs_dump_mem("SPNEGO reply blob:", msg->data, min(1024U,
184 msg->secblob_len + msg->sesskey_len));
185 }
186 #endif /* CONFIG_CIFS_DEBUG2 */
187
188 out:
189 kfree(description);
190 return spnego_key;
191 }
192
193 int
init_cifs_spnego(void)194 init_cifs_spnego(void)
195 {
196 struct cred *cred;
197 struct key *keyring;
198 int ret;
199
200 cifs_dbg(FYI, "Registering the %s key type\n",
201 cifs_spnego_key_type.name);
202
203 /*
204 * Create an override credential set with special thread keyring for
205 * spnego upcalls.
206 */
207
208 cred = prepare_kernel_cred(&init_task);
209 if (!cred)
210 return -ENOMEM;
211
212 keyring = keyring_alloc(".cifs_spnego",
213 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
214 (KEY_POS_ALL & ~KEY_POS_SETATTR) |
215 KEY_USR_VIEW | KEY_USR_READ,
216 KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
217 if (IS_ERR(keyring)) {
218 ret = PTR_ERR(keyring);
219 goto failed_put_cred;
220 }
221
222 ret = register_key_type(&cifs_spnego_key_type);
223 if (ret < 0)
224 goto failed_put_key;
225
226 /*
227 * instruct request_key() to use this special keyring as a cache for
228 * the results it looks up
229 */
230 set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
231 cred->thread_keyring = keyring;
232 cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
233 spnego_cred = cred;
234
235 cifs_dbg(FYI, "cifs spnego keyring: %d\n", key_serial(keyring));
236 return 0;
237
238 failed_put_key:
239 key_put(keyring);
240 failed_put_cred:
241 put_cred(cred);
242 return ret;
243 }
244
245 void
exit_cifs_spnego(void)246 exit_cifs_spnego(void)
247 {
248 key_revoke(spnego_cred->thread_keyring);
249 unregister_key_type(&cifs_spnego_key_type);
250 put_cred(spnego_cred);
251 cifs_dbg(FYI, "Unregistered %s key type\n", cifs_spnego_key_type.name);
252 }
253