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ddbb4114 MM |
1 | /* 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 | */ | |
31 | static int do_dh(MPI result, MPI base, MPI xa, MPI p) | |
32 | { | |
33 | return mpi_powm(result, base, xa, p); | |
34 | } | |
35 | ||
36 | static 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); | |
76 | error: | |
77 | return ret; | |
78 | } | |
79 | ||
80 | long 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 | ||
148 | error5: | |
149 | kfree(kbuf); | |
150 | error4: | |
151 | mpi_free(result); | |
152 | error3: | |
153 | mpi_free(private); | |
154 | error2: | |
155 | mpi_free(base); | |
156 | error1: | |
157 | mpi_free(prime); | |
158 | out: | |
159 | return ret; | |
160 | } |