xref: /qemu/crypto/cipher-gnutls.c.inc (revision 8b7b9c5c) 
1/*
2 * QEMU Crypto cipher gnutls algorithms
3 *
4 * Copyright (c) 2021 Red Hat, Inc.
5 *
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public
17 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 *
19 */
20
21#include "qemu/osdep.h"
22#include "cipherpriv.h"
23
24#include <gnutls/crypto.h>
25
26#if GNUTLS_VERSION_NUMBER >= 0x030608
27#define QEMU_GNUTLS_XTS
28#endif
29
30bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg,
31                             QCryptoCipherMode mode)
32{
33
34    switch (mode) {
35    case QCRYPTO_CIPHER_MODE_ECB:
36    case QCRYPTO_CIPHER_MODE_CBC:
37        switch (alg) {
38        case QCRYPTO_CIPHER_ALG_AES_128:
39        case QCRYPTO_CIPHER_ALG_AES_192:
40        case QCRYPTO_CIPHER_ALG_AES_256:
41        case QCRYPTO_CIPHER_ALG_DES:
42        case QCRYPTO_CIPHER_ALG_3DES:
43            return true;
44        default:
45            return false;
46        }
47#ifdef QEMU_GNUTLS_XTS
48    case QCRYPTO_CIPHER_MODE_XTS:
49        switch (alg) {
50        case QCRYPTO_CIPHER_ALG_AES_128:
51        case QCRYPTO_CIPHER_ALG_AES_256:
52            return true;
53        default:
54            return false;
55        }
56#endif
57    default:
58        return false;
59    }
60}
61
62typedef struct QCryptoCipherGnutls QCryptoCipherGnutls;
63struct QCryptoCipherGnutls {
64    QCryptoCipher base;
65    gnutls_cipher_hd_t handle; /* XTS & CBC mode */
66    gnutls_cipher_algorithm_t galg; /* ECB mode */
67    guint8 *key; /* ECB mode */
68    size_t nkey; /* ECB mode */
69    size_t blocksize;
70};
71
72
73static void
74qcrypto_gnutls_cipher_free(QCryptoCipher *cipher)
75{
76    QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
77
78    g_free(ctx->key);
79    if (ctx->handle) {
80        gnutls_cipher_deinit(ctx->handle);
81    }
82    g_free(ctx);
83}
84
85
86static int
87qcrypto_gnutls_cipher_encrypt(QCryptoCipher *cipher,
88                              const void *in,
89                              void *out,
90                              size_t len,
91                              Error **errp)
92{
93    QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
94    int err;
95
96    if (len % ctx->blocksize) {
97        error_setg(errp, "Length %zu must be a multiple of block size %zu",
98                   len, ctx->blocksize);
99        return -1;
100    }
101
102    if (ctx->handle) { /* CBC / XTS mode */
103        err = gnutls_cipher_encrypt2(ctx->handle,
104                                     in, len,
105                                     out, len);
106        if (err != 0) {
107            error_setg(errp, "Cannot encrypt data: %s",
108                       gnutls_strerror(err));
109            return -1;
110        }
111    } else { /* ECB mode very inefficiently faked with CBC */
112        g_autofree unsigned char *iv = g_new0(unsigned char, ctx->blocksize);
113        while (len) {
114            gnutls_cipher_hd_t handle;
115            gnutls_datum_t gkey = { (unsigned char *)ctx->key, ctx->nkey };
116            err = gnutls_cipher_init(&handle, ctx->galg, &gkey, NULL);
117            if (err != 0) {
118                error_setg(errp, "Cannot initialize cipher: %s",
119                           gnutls_strerror(err));
120                return -1;
121            }
122
123            gnutls_cipher_set_iv(handle, iv, ctx->blocksize);
124
125            err = gnutls_cipher_encrypt2(handle,
126                                         in, ctx->blocksize,
127                                         out, ctx->blocksize);
128            if (err != 0) {
129                gnutls_cipher_deinit(handle);
130                error_setg(errp, "Cannot encrypt data: %s",
131                           gnutls_strerror(err));
132                return -1;
133            }
134            gnutls_cipher_deinit(handle);
135
136            len -= ctx->blocksize;
137            in += ctx->blocksize;
138            out += ctx->blocksize;
139        }
140    }
141
142    return 0;
143}
144
145
146static int
147qcrypto_gnutls_cipher_decrypt(QCryptoCipher *cipher,
148                              const void *in,
149                              void *out,
150                              size_t len,
151                              Error **errp)
152{
153    QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
154    int err;
155
156    if (len % ctx->blocksize) {
157        error_setg(errp, "Length %zu must be a multiple of block size %zu",
158                   len, ctx->blocksize);
159        return -1;
160    }
161
162    if (ctx->handle) { /* CBC / XTS mode */
163        err = gnutls_cipher_decrypt2(ctx->handle,
164                                     in, len,
165                                     out, len);
166
167        if (err != 0) {
168            error_setg(errp, "Cannot decrypt data: %s",
169                       gnutls_strerror(err));
170            return -1;
171        }
172    } else { /* ECB mode very inefficiently faked with CBC */
173        g_autofree unsigned char *iv = g_new0(unsigned char, ctx->blocksize);
174        while (len) {
175            gnutls_cipher_hd_t handle;
176            gnutls_datum_t gkey = { (unsigned char *)ctx->key, ctx->nkey };
177            err = gnutls_cipher_init(&handle, ctx->galg, &gkey, NULL);
178            if (err != 0) {
179                error_setg(errp, "Cannot initialize cipher: %s",
180                           gnutls_strerror(err));
181                return -1;
182            }
183
184            gnutls_cipher_set_iv(handle, iv, ctx->blocksize);
185
186            err = gnutls_cipher_decrypt2(handle,
187                                         in, ctx->blocksize,
188                                         out, ctx->blocksize);
189            if (err != 0) {
190                gnutls_cipher_deinit(handle);
191                error_setg(errp, "Cannot encrypt data: %s",
192                           gnutls_strerror(err));
193                return -1;
194            }
195            gnutls_cipher_deinit(handle);
196
197            len -= ctx->blocksize;
198            in += ctx->blocksize;
199            out += ctx->blocksize;
200        }
201    }
202
203    return 0;
204}
205
206static int
207qcrypto_gnutls_cipher_setiv(QCryptoCipher *cipher,
208                            const uint8_t *iv, size_t niv,
209                            Error **errp)
210{
211    QCryptoCipherGnutls *ctx = container_of(cipher, QCryptoCipherGnutls, base);
212
213    if (niv != ctx->blocksize) {
214        error_setg(errp, "Expected IV size %zu not %zu",
215                   ctx->blocksize, niv);
216        return -1;
217    }
218
219    gnutls_cipher_set_iv(ctx->handle, (unsigned char *)iv, niv);
220
221    return 0;
222}
223
224
225static struct QCryptoCipherDriver gnutls_driver = {
226    .cipher_encrypt = qcrypto_gnutls_cipher_encrypt,
227    .cipher_decrypt = qcrypto_gnutls_cipher_decrypt,
228    .cipher_setiv = qcrypto_gnutls_cipher_setiv,
229    .cipher_free = qcrypto_gnutls_cipher_free,
230};
231
232static QCryptoCipher *qcrypto_cipher_ctx_new(QCryptoCipherAlgorithm alg,
233                                             QCryptoCipherMode mode,
234                                             const uint8_t *key,
235                                             size_t nkey,
236                                             Error **errp)
237{
238    QCryptoCipherGnutls *ctx;
239    gnutls_datum_t gkey = { (unsigned char *)key, nkey };
240    gnutls_cipher_algorithm_t galg = GNUTLS_CIPHER_UNKNOWN;
241    int err;
242
243    switch (mode) {
244#ifdef QEMU_GNUTLS_XTS
245    case QCRYPTO_CIPHER_MODE_XTS:
246        switch (alg) {
247        case QCRYPTO_CIPHER_ALG_AES_128:
248            galg = GNUTLS_CIPHER_AES_128_XTS;
249            break;
250        case QCRYPTO_CIPHER_ALG_AES_256:
251            galg = GNUTLS_CIPHER_AES_256_XTS;
252            break;
253        default:
254            break;
255        }
256        break;
257#endif
258
259    case QCRYPTO_CIPHER_MODE_ECB:
260    case QCRYPTO_CIPHER_MODE_CBC:
261        switch (alg) {
262        case QCRYPTO_CIPHER_ALG_AES_128:
263            galg = GNUTLS_CIPHER_AES_128_CBC;
264            break;
265        case QCRYPTO_CIPHER_ALG_AES_192:
266            galg = GNUTLS_CIPHER_AES_192_CBC;
267            break;
268        case QCRYPTO_CIPHER_ALG_AES_256:
269            galg = GNUTLS_CIPHER_AES_256_CBC;
270            break;
271        case QCRYPTO_CIPHER_ALG_DES:
272            galg = GNUTLS_CIPHER_DES_CBC;
273            break;
274        case QCRYPTO_CIPHER_ALG_3DES:
275            galg = GNUTLS_CIPHER_3DES_CBC;
276            break;
277        default:
278            break;
279        }
280        break;
281    default:
282        break;
283    }
284
285    if (galg == GNUTLS_CIPHER_UNKNOWN) {
286        error_setg(errp, "Unsupported cipher algorithm %s with %s mode",
287                   QCryptoCipherAlgorithm_str(alg),
288                   QCryptoCipherMode_str(mode));
289        return NULL;
290    }
291
292    if (!qcrypto_cipher_validate_key_length(alg, mode, nkey, errp)) {
293        return NULL;
294    }
295
296    ctx = g_new0(QCryptoCipherGnutls, 1);
297    ctx->base.driver = &gnutls_driver;
298
299    if (mode == QCRYPTO_CIPHER_MODE_ECB) {
300        ctx->key = g_new0(guint8, nkey);
301        memcpy(ctx->key, key, nkey);
302        ctx->nkey = nkey;
303        ctx->galg = galg;
304    } else {
305        err = gnutls_cipher_init(&ctx->handle, galg, &gkey, NULL);
306        if (err != 0) {
307            error_setg(errp, "Cannot initialize cipher: %s",
308                       gnutls_strerror(err));
309            goto error;
310        }
311    }
312
313    if (alg == QCRYPTO_CIPHER_ALG_DES ||
314        alg == QCRYPTO_CIPHER_ALG_3DES)
315        ctx->blocksize = 8;
316    else
317        ctx->blocksize = 16;
318
319    /*
320     * Our API contract for requires iv to be optional
321     * but nettle gets unhappy when called by gnutls
322     * in this case, so we just force set a default
323     * all-zeros IV, to match behaviour of other backends.
324     */
325    if (mode != QCRYPTO_CIPHER_MODE_ECB) {
326        g_autofree unsigned char *iv = g_new0(unsigned char, ctx->blocksize);
327        gnutls_cipher_set_iv(ctx->handle, iv, ctx->blocksize);
328    }
329
330    return &ctx->base;
331
332 error:
333    qcrypto_gnutls_cipher_free(&ctx->base);
334    return NULL;
335}
336