blob: 880505a4b9f1e273429783aa5ebe1eee2579674c [file] [log] [blame]
Mat Martineauddbb4112016-04-12 19:54:58 +01001/* Crypto operations using stored keys
2 *
3 * Copyright (c) 2016, Intel Corporation
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public License
7 * as published by the Free Software Foundation; either version
8 * 2 of the License, or (at your option) any later version.
9 */
10
11#include <linux/mpi.h>
12#include <linux/slab.h>
13#include <linux/uaccess.h>
14#include <keys/user-type.h>
15#include "internal.h"
16
17/*
18 * Public key or shared secret generation function [RFC2631 sec 2.1.1]
19 *
20 * ya = g^xa mod p;
21 * or
22 * ZZ = yb^xa mod p;
23 *
24 * where xa is the local private key, ya is the local public key, g is
25 * the generator, p is the prime, yb is the remote public key, and ZZ
26 * is the shared secret.
27 *
28 * Both are the same calculation, so g or yb are the "base" and ya or
29 * ZZ are the "result".
30 */
31static int do_dh(MPI result, MPI base, MPI xa, MPI p)
32{
33 return mpi_powm(result, base, xa, p);
34}
35
36static ssize_t mpi_from_key(key_serial_t keyid, size_t maxlen, MPI *mpi)
37{
38 struct key *key;
39 key_ref_t key_ref;
40 long status;
41 ssize_t ret;
42
43 key_ref = lookup_user_key(keyid, 0, KEY_NEED_READ);
44 if (IS_ERR(key_ref)) {
45 ret = -ENOKEY;
46 goto error;
47 }
48
49 key = key_ref_to_ptr(key_ref);
50
51 ret = -EOPNOTSUPP;
52 if (key->type == &key_type_user) {
53 down_read(&key->sem);
54 status = key_validate(key);
55 if (status == 0) {
56 const struct user_key_payload *payload;
57
58 payload = user_key_payload(key);
59
60 if (maxlen == 0) {
61 *mpi = NULL;
62 ret = payload->datalen;
63 } else if (payload->datalen <= maxlen) {
64 *mpi = mpi_read_raw_data(payload->data,
65 payload->datalen);
66 if (*mpi)
67 ret = payload->datalen;
68 } else {
69 ret = -EINVAL;
70 }
71 }
72 up_read(&key->sem);
73 }
74
75 key_put(key);
76error:
77 return ret;
78}
79
80long keyctl_dh_compute(struct keyctl_dh_params __user *params,
81 char __user *buffer, size_t buflen)
82{
83 long ret;
84 MPI base, private, prime, result;
85 unsigned nbytes;
86 struct keyctl_dh_params pcopy;
87 uint8_t *kbuf;
88 ssize_t keylen;
89 size_t resultlen;
90
91 if (!params || (!buffer && buflen)) {
92 ret = -EINVAL;
93 goto out;
94 }
95 if (copy_from_user(&pcopy, params, sizeof(pcopy)) != 0) {
96 ret = -EFAULT;
97 goto out;
98 }
99
100 keylen = mpi_from_key(pcopy.prime, buflen, &prime);
101 if (keylen < 0 || !prime) {
102 /* buflen == 0 may be used to query the required buffer size,
103 * which is the prime key length.
104 */
105 ret = keylen;
106 goto out;
107 }
108
109 /* The result is never longer than the prime */
110 resultlen = keylen;
111
112 keylen = mpi_from_key(pcopy.base, SIZE_MAX, &base);
113 if (keylen < 0 || !base) {
114 ret = keylen;
115 goto error1;
116 }
117
118 keylen = mpi_from_key(pcopy.private, SIZE_MAX, &private);
119 if (keylen < 0 || !private) {
120 ret = keylen;
121 goto error2;
122 }
123
124 result = mpi_alloc(0);
125 if (!result) {
126 ret = -ENOMEM;
127 goto error3;
128 }
129
130 kbuf = kmalloc(resultlen, GFP_KERNEL);
131 if (!kbuf) {
132 ret = -ENOMEM;
133 goto error4;
134 }
135
136 ret = do_dh(result, base, private, prime);
137 if (ret)
138 goto error5;
139
140 ret = mpi_read_buffer(result, kbuf, resultlen, &nbytes, NULL);
141 if (ret != 0)
142 goto error5;
143
144 ret = nbytes;
145 if (copy_to_user(buffer, kbuf, nbytes) != 0)
146 ret = -EFAULT;
147
148error5:
149 kfree(kbuf);
150error4:
151 mpi_free(result);
152error3:
153 mpi_free(private);
154error2:
155 mpi_free(base);
156error1:
157 mpi_free(prime);
158out:
159 return ret;
160}