1/*
2 *  PSA FFDH layer on top of Mbed TLS crypto
3 */
4/*
5 *  Copyright The Mbed TLS Contributors
6 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
7 */
8
9#include "common.h"
10
11#if defined(MBEDTLS_PSA_CRYPTO_C)
12
13/* This header is only needed because it defines
14 * MBEDTLS_DHM_RFC7919_FFDHEXXXX_[P|G]_BIN symbols that are used in
15 * mbedtls_psa_ffdh_set_prime_generator(). Apart from that, this module
16 * only uses bignum functions for arithmetic. */
17#include <mbedtls/dhm.h>
18
19#include <psa/crypto.h>
20#include "psa_crypto_core.h"
21#include "psa_crypto_ffdh.h"
22#include "psa_crypto_random_impl.h"
23#include "mbedtls/platform.h"
24#include "mbedtls/error.h"
25
26#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_EXPORT) ||   \
27    defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_GENERATE) ||   \
28    defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY) || \
29    defined(MBEDTLS_PSA_BUILTIN_ALG_FFDH)
30static psa_status_t mbedtls_psa_ffdh_set_prime_generator(size_t key_size,
31                                                         mbedtls_mpi *P,
32                                                         mbedtls_mpi *G)
33{
34    const unsigned char *dhm_P = NULL;
35    const unsigned char *dhm_G = NULL;
36    size_t dhm_size_P = 0;
37    size_t dhm_size_G = 0;
38    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
39
40    if (P == NULL && G == NULL) {
41        return PSA_ERROR_INVALID_ARGUMENT;
42    }
43
44#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_2048)
45    static const unsigned char dhm_P_2048[] =
46        MBEDTLS_DHM_RFC7919_FFDHE2048_P_BIN;
47    static const unsigned char dhm_G_2048[] =
48        MBEDTLS_DHM_RFC7919_FFDHE2048_G_BIN;
49#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_2048 */
50#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_3072)
51    static const unsigned char dhm_P_3072[] =
52        MBEDTLS_DHM_RFC7919_FFDHE3072_P_BIN;
53    static const unsigned char dhm_G_3072[] =
54        MBEDTLS_DHM_RFC7919_FFDHE3072_G_BIN;
55#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_3072 */
56#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_4096)
57    static const unsigned char dhm_P_4096[] =
58        MBEDTLS_DHM_RFC7919_FFDHE4096_P_BIN;
59    static const unsigned char dhm_G_4096[] =
60        MBEDTLS_DHM_RFC7919_FFDHE4096_G_BIN;
61#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_4096 */
62#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_6144)
63    static const unsigned char dhm_P_6144[] =
64        MBEDTLS_DHM_RFC7919_FFDHE6144_P_BIN;
65    static const unsigned char dhm_G_6144[] =
66        MBEDTLS_DHM_RFC7919_FFDHE6144_G_BIN;
67#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_6144 */
68#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_8192)
69    static const unsigned char dhm_P_8192[] =
70        MBEDTLS_DHM_RFC7919_FFDHE8192_P_BIN;
71    static const unsigned char dhm_G_8192[] =
72        MBEDTLS_DHM_RFC7919_FFDHE8192_G_BIN;
73#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_8192 */
74
75    switch (key_size) {
76#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_2048)
77        case sizeof(dhm_P_2048):
78            dhm_P = dhm_P_2048;
79            dhm_G = dhm_G_2048;
80            dhm_size_P = sizeof(dhm_P_2048);
81            dhm_size_G = sizeof(dhm_G_2048);
82            break;
83#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_2048 */
84#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_3072)
85        case sizeof(dhm_P_3072):
86            dhm_P = dhm_P_3072;
87            dhm_G = dhm_G_3072;
88            dhm_size_P = sizeof(dhm_P_3072);
89            dhm_size_G = sizeof(dhm_G_3072);
90            break;
91#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_3072 */
92#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_4096)
93        case sizeof(dhm_P_4096):
94            dhm_P = dhm_P_4096;
95            dhm_G = dhm_G_4096;
96            dhm_size_P = sizeof(dhm_P_4096);
97            dhm_size_G = sizeof(dhm_G_4096);
98            break;
99#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_4096 */
100#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_6144)
101        case sizeof(dhm_P_6144):
102            dhm_P = dhm_P_6144;
103            dhm_G = dhm_G_6144;
104            dhm_size_P = sizeof(dhm_P_6144);
105            dhm_size_G = sizeof(dhm_G_6144);
106            break;
107#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_6144 */
108#if defined(MBEDTLS_PSA_BUILTIN_DH_RFC7919_8192)
109        case sizeof(dhm_P_8192):
110            dhm_P = dhm_P_8192;
111            dhm_G = dhm_G_8192;
112            dhm_size_P = sizeof(dhm_P_8192);
113            dhm_size_G = sizeof(dhm_G_8192);
114            break;
115#endif /* MBEDTLS_PSA_BUILTIN_DH_RFC7919_8192 */
116        default:
117            return PSA_ERROR_INVALID_ARGUMENT;
118    }
119
120    if (P != NULL) {
121        MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(P, dhm_P,
122                                                dhm_size_P));
123    }
124    if (G != NULL) {
125        MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(G, dhm_G,
126                                                dhm_size_G));
127    }
128
129cleanup:
130    if (ret != 0) {
131        return mbedtls_to_psa_error(ret);
132    }
133
134    return PSA_SUCCESS;
135}
136#endif /* MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_EXPORT ||
137          MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_GENERATE ||
138          MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY ||
139          MBEDTLS_PSA_BUILTIN_ALG_FFDH */
140
141#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_EXPORT) || \
142    defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY)
143psa_status_t mbedtls_psa_ffdh_export_public_key(
144    const psa_key_attributes_t *attributes,
145    const uint8_t *key_buffer,
146    size_t key_buffer_size,
147    uint8_t *data,
148    size_t data_size,
149    size_t *data_length)
150{
151    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
152    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
153    mbedtls_mpi GX, G, X, P;
154    psa_key_type_t type = attributes->type;
155
156    if (PSA_KEY_TYPE_IS_PUBLIC_KEY(type)) {
157        if (key_buffer_size > data_size) {
158            return PSA_ERROR_BUFFER_TOO_SMALL;
159        }
160        memcpy(data, key_buffer, key_buffer_size);
161        memset(data + key_buffer_size, 0,
162               data_size - key_buffer_size);
163        *data_length = key_buffer_size;
164        return PSA_SUCCESS;
165    }
166
167    mbedtls_mpi_init(&GX); mbedtls_mpi_init(&G);
168    mbedtls_mpi_init(&X); mbedtls_mpi_init(&P);
169
170    size_t key_len = PSA_BITS_TO_BYTES(attributes->bits);
171
172    status = mbedtls_psa_ffdh_set_prime_generator(key_len, &P, &G);
173
174    if (status != PSA_SUCCESS) {
175        goto cleanup;
176    }
177
178    MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&X, key_buffer,
179                                            key_buffer_size));
180
181    MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&GX, &G, &X, &P, NULL));
182    MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&GX, data, key_len));
183
184    *data_length = key_len;
185
186    ret = 0;
187cleanup:
188    mbedtls_mpi_free(&P); mbedtls_mpi_free(&G);
189    mbedtls_mpi_free(&X); mbedtls_mpi_free(&GX);
190
191    if (status == PSA_SUCCESS && ret != 0) {
192        status = mbedtls_to_psa_error(ret);
193    }
194
195    return status;
196}
197#endif /* MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_EXPORT ||
198          MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_PUBLIC_KEY */
199
200#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_GENERATE)
201psa_status_t mbedtls_psa_ffdh_generate_key(
202    const psa_key_attributes_t *attributes,
203    uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length)
204{
205    mbedtls_mpi X, P;
206    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
207    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
208    mbedtls_mpi_init(&P); mbedtls_mpi_init(&X);
209    (void) attributes;
210
211    status = mbedtls_psa_ffdh_set_prime_generator(key_buffer_size, &P, NULL);
212
213    if (status != PSA_SUCCESS) {
214        goto cleanup;
215    }
216
217    /* RFC7919: Traditional finite field Diffie-Hellman has each peer choose their
218        secret exponent from the range [2, P-2].
219        Select random value in range [3, P-1] and decrease it by 1. */
220    MBEDTLS_MPI_CHK(mbedtls_mpi_random(&X, 3, &P, mbedtls_psa_get_random,
221                                       MBEDTLS_PSA_RANDOM_STATE));
222    MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&X, &X, 1));
223    MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&X, key_buffer, key_buffer_size));
224    *key_buffer_length = key_buffer_size;
225
226cleanup:
227    mbedtls_mpi_free(&P); mbedtls_mpi_free(&X);
228    if (status == PSA_SUCCESS && ret != 0) {
229        return mbedtls_to_psa_error(ret);
230    }
231
232    return status;
233}
234#endif /* MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_GENERATE */
235
236#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_IMPORT)
237psa_status_t mbedtls_psa_ffdh_import_key(
238    const psa_key_attributes_t *attributes,
239    const uint8_t *data, size_t data_length,
240    uint8_t *key_buffer, size_t key_buffer_size,
241    size_t *key_buffer_length, size_t *bits)
242{
243    (void) attributes;
244
245    if (key_buffer_size < data_length) {
246        return PSA_ERROR_BUFFER_TOO_SMALL;
247    }
248    memcpy(key_buffer, data, data_length);
249    *key_buffer_length = data_length;
250    *bits = PSA_BYTES_TO_BITS(data_length);
251
252    return PSA_SUCCESS;
253}
254#endif /* MBEDTLS_PSA_BUILTIN_KEY_TYPE_DH_KEY_PAIR_IMPORT */
255
256#if defined(MBEDTLS_PSA_BUILTIN_ALG_FFDH)
257psa_status_t mbedtls_psa_ffdh_key_agreement(
258    const psa_key_attributes_t *attributes,
259    const uint8_t *peer_key,
260    size_t peer_key_length,
261    const uint8_t *key_buffer,
262    size_t key_buffer_size,
263    uint8_t *shared_secret,
264    size_t shared_secret_size,
265    size_t *shared_secret_length)
266{
267    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
268    psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
269    mbedtls_mpi P, G, X, GY, K;
270    const size_t calculated_shared_secret_size = peer_key_length;
271
272    if (peer_key_length != key_buffer_size ||
273        calculated_shared_secret_size > shared_secret_size) {
274        return PSA_ERROR_INVALID_ARGUMENT;
275    }
276
277    if (!PSA_KEY_TYPE_IS_DH_KEY_PAIR(psa_get_key_type(attributes))) {
278        return PSA_ERROR_INVALID_ARGUMENT;
279    }
280
281    mbedtls_mpi_init(&P); mbedtls_mpi_init(&G);
282    mbedtls_mpi_init(&X); mbedtls_mpi_init(&GY);
283    mbedtls_mpi_init(&K);
284
285    status = mbedtls_psa_ffdh_set_prime_generator(
286        PSA_BITS_TO_BYTES(attributes->bits), &P, &G);
287
288    if (status != PSA_SUCCESS) {
289        goto cleanup;
290    }
291
292    MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&X, key_buffer,
293                                            key_buffer_size));
294
295    MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&GY, peer_key,
296                                            peer_key_length));
297
298    /* Calculate shared secret public key: K = G^(XY) mod P = GY^X mod P */
299    MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&K, &GY, &X, &P, NULL));
300
301    MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&K, shared_secret,
302                                             calculated_shared_secret_size));
303
304    *shared_secret_length = calculated_shared_secret_size;
305
306    ret = 0;
307
308cleanup:
309    mbedtls_mpi_free(&P); mbedtls_mpi_free(&G);
310    mbedtls_mpi_free(&X); mbedtls_mpi_free(&GY);
311    mbedtls_mpi_free(&K);
312
313    if (status == PSA_SUCCESS && ret != 0) {
314        status = mbedtls_to_psa_error(ret);
315    }
316
317    return status;
318}
319#endif /* MBEDTLS_PSA_BUILTIN_ALG_FFDH */
320
321#endif /* MBEDTLS_PSA_CRYPTO_C */
322