aboutsummaryrefslogtreecommitdiff
path: root/security/keys/request_key_auth.c
blob: 68164031a74e0bc225844037ceedd45a40fc94cb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
/* Request key authorisation token key definition.
 *
 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 *
 * See Documentation/keys-request-key.txt
 */

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/err.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include "internal.h"

static int request_key_auth_instantiate(struct key *, const void *, size_t);
static void request_key_auth_describe(const struct key *, struct seq_file *);
static void request_key_auth_revoke(struct key *);
static void request_key_auth_destroy(struct key *);
static long request_key_auth_read(const struct key *, char __user *, size_t);

/*
 * The request-key authorisation key type definition.
 */
struct key_type key_type_request_key_auth = {
	.name		= ".request_key_auth",
	.def_datalen	= sizeof(struct request_key_auth),
	.instantiate	= request_key_auth_instantiate,
	.describe	= request_key_auth_describe,
	.revoke		= request_key_auth_revoke,
	.destroy	= request_key_auth_destroy,
	.read		= request_key_auth_read,
};

/*
 * Instantiate a request-key authorisation key.
 */
static int request_key_auth_instantiate(struct key *key,
					const void *data,
					size_t datalen)
{
	key->payload.data = (struct request_key_auth *) data;
	return 0;
}

/*
 * Describe an authorisation token.
 */
static void request_key_auth_describe(const struct key *key,
				      struct seq_file *m)
{
	struct request_key_auth *rka = key->payload.data;

	seq_puts(m, "key:");
	seq_puts(m, key->description);
	seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
}

/*
 * Read the callout_info data (retrieves the callout information).
 * - the key's semaphore is read-locked
 */
static long request_key_auth_read(const struct key *key,
				  char __user *buffer, size_t buflen)
{
	struct request_key_auth *rka = key->payload.data;
	size_t datalen;
	long ret;

	datalen = rka->callout_len;
	ret = datalen;

	/* we can return the data as is */
	if (buffer && buflen > 0) {
		if (buflen > datalen)
			buflen = datalen;

		if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
			ret = -EFAULT;
	}

	return ret;
}

/*
 * Handle revocation of an authorisation token key.
 *
 * Called with the key sem write-locked.
 */
static void request_key_auth_revoke(struct key *key)
{
	struct request_key_auth *rka = key->payload.data;

	kenter("{%d}", key->serial);

	if (rka->cred) {
		put_cred(rka->cred);
		rka->cred = NULL;
	}
}

/*
 * Destroy an instantiation authorisation token key.
 */
static void request_key_auth_destroy(struct key *key)
{
	struct request_key_auth *rka = key->payload.data;

	kenter("{%d}", key->serial);

	if (rka->cred) {
		put_cred(rka->cred);
		rka->cred = NULL;
	}

	key_put(rka->target_key);
	key_put(rka->dest_keyring);
	kfree(rka->callout_info);
	kfree(rka);
}

/*
 * Create an authorisation token for /sbin/request-key or whoever to gain
 * access to the caller's security data.
 */
struct key *request_key_auth_new(struct key *target, const void *callout_info,
				 size_t callout_len, struct key *dest_keyring)
{
	struct request_key_auth *rka, *irka;
	const struct cred *cred = current->cred;
	struct key *authkey = NULL;
	char desc[20];
	int ret;

	kenter("%d,", target->serial);

	/* allocate a auth record */
	rka = kmalloc(sizeof(*rka), GFP_KERNEL);
	if (!rka) {
		kleave(" = -ENOMEM");
		return ERR_PTR(-ENOMEM);
	}
	rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
	if (!rka->callout_info) {
		kleave(" = -ENOMEM");
		kfree(rka);
		return ERR_PTR(-ENOMEM);
	}

	/* see if the calling process is already servicing the key request of
	 * another process */
	if (cred->request_key_auth) {
		/* it is - use that instantiation context here too */
		down_read(&cred->request_key_auth->sem);

		/* if the auth key has been revoked, then the key we're
		 * servicing is already instantiated */
		if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
			goto auth_key_revoked;

		irka = cred->request_key_auth->payload.data;
		rka->cred = get_cred(irka->cred);
		rka->pid = irka->pid;

		up_read(&cred->request_key_auth->sem);
	}
	else {
		/* it isn't - use this process as the context */
		rka->cred = get_cred(cred);
		rka->pid = current->pid;
	}

	rka->target_key = key_get(target);
	rka->dest_keyring = key_get(dest_keyring);
	memcpy(rka->callout_info, callout_info, callout_len);
	rka->callout_len = callout_len;

	/* allocate the auth key */
	sprintf(desc, "%x", target->serial);

	authkey = key_alloc(&key_type_request_key_auth, desc,
			    cred->fsuid, cred->fsgid, cred,
			    KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
			    KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
	if (IS_ERR(authkey)) {
		ret = PTR_ERR(authkey);
		goto error_alloc;
	}

	/* construct the auth key */
	ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
	if (ret < 0)
		goto error_inst;

	kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
	return authkey;

auth_key_revoked:
	up_read(&cred->request_key_auth->sem);
	kfree(rka->callout_info);
	kfree(rka);
	kleave("= -EKEYREVOKED");
	return ERR_PTR(-EKEYREVOKED);

error_inst:
	key_revoke(authkey);
	key_put(authkey);
error_alloc:
	key_put(rka->target_key);
	key_put(rka->dest_keyring);
	kfree(rka->callout_info);
	kfree(rka);
	kleave("= %d", ret);
	return ERR_PTR(ret);
}

/*
 * See if an authorisation key is associated with a particular key.
 */
static int key_get_instantiation_authkey_match(const struct key *key,
					       const void *_id)
{
	struct request_key_auth *rka = key->payload.data;
	key_serial_t id = (key_serial_t)(unsigned long) _id;

	return rka->target_key->serial == id;
}

/*
 * Search the current process's keyrings for the authorisation key for
 * instantiation of a key.
 */
struct key *key_get_instantiation_authkey(key_serial_t target_id)
{
	const struct cred *cred = current_cred();
	struct key *authkey;
	key_ref_t authkey_ref;

	authkey_ref = search_process_keyrings(
		&key_type_request_key_auth,
		(void *) (unsigned long) target_id,
		key_get_instantiation_authkey_match,
		cred);

	if (IS_ERR(authkey_ref)) {
		authkey = ERR_CAST(authkey_ref);
		goto error;
	}

	authkey = key_ref_to_ptr(authkey_ref);
	if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
		key_put(authkey);
		authkey = ERR_PTR(-EKEYREVOKED);
	}

error:
	return authkey;
}