1 /* Copyright (c) 2015, Google Inc.
2 *
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
6 *
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14
15 #include <openssl/ssl.h>
16
17 #include <assert.h>
18 #include <string.h>
19
20 #include <openssl/aead.h>
21 #include <openssl/err.h>
22 #include <openssl/rand.h>
23 #include <openssl/type_check.h>
24
25 #include "internal.h"
26
27
28 OPENSSL_COMPILE_ASSERT(EVP_AEAD_MAX_NONCE_LENGTH < 256,
29 variable_nonce_len_doesnt_fit_in_uint8_t);
30
SSL_AEAD_CTX_new(enum evp_aead_direction_t direction,uint16_t version,const SSL_CIPHER * cipher,const uint8_t * enc_key,size_t enc_key_len,const uint8_t * mac_key,size_t mac_key_len,const uint8_t * fixed_iv,size_t fixed_iv_len)31 SSL_AEAD_CTX *SSL_AEAD_CTX_new(enum evp_aead_direction_t direction,
32 uint16_t version, const SSL_CIPHER *cipher,
33 const uint8_t *enc_key, size_t enc_key_len,
34 const uint8_t *mac_key, size_t mac_key_len,
35 const uint8_t *fixed_iv, size_t fixed_iv_len) {
36 const EVP_AEAD *aead;
37 size_t discard;
38 if (!ssl_cipher_get_evp_aead(&aead, &discard, &discard, cipher, version)) {
39 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
40 return 0;
41 }
42
43 uint8_t merged_key[EVP_AEAD_MAX_KEY_LENGTH];
44 if (mac_key_len > 0) {
45 /* This is a "stateful" AEAD (for compatibility with pre-AEAD cipher
46 * suites). */
47 if (mac_key_len + enc_key_len + fixed_iv_len > sizeof(merged_key)) {
48 OPENSSL_PUT_ERROR(SSL, ERR_R_INTERNAL_ERROR);
49 return 0;
50 }
51 memcpy(merged_key, mac_key, mac_key_len);
52 memcpy(merged_key + mac_key_len, enc_key, enc_key_len);
53 memcpy(merged_key + mac_key_len + enc_key_len, fixed_iv, fixed_iv_len);
54 enc_key = merged_key;
55 enc_key_len += mac_key_len;
56 enc_key_len += fixed_iv_len;
57 }
58
59 SSL_AEAD_CTX *aead_ctx = (SSL_AEAD_CTX *)OPENSSL_malloc(sizeof(SSL_AEAD_CTX));
60 if (aead_ctx == NULL) {
61 OPENSSL_PUT_ERROR(SSL, ERR_R_MALLOC_FAILURE);
62 return NULL;
63 }
64 memset(aead_ctx, 0, sizeof(SSL_AEAD_CTX));
65 aead_ctx->cipher = cipher;
66
67 if (!EVP_AEAD_CTX_init_with_direction(
68 &aead_ctx->ctx, aead, enc_key, enc_key_len,
69 EVP_AEAD_DEFAULT_TAG_LENGTH, direction)) {
70 OPENSSL_free(aead_ctx);
71 return NULL;
72 }
73
74 assert(EVP_AEAD_nonce_length(aead) <= EVP_AEAD_MAX_NONCE_LENGTH);
75 aead_ctx->variable_nonce_len = (uint8_t)EVP_AEAD_nonce_length(aead);
76 if (mac_key_len == 0) {
77 assert(fixed_iv_len <= sizeof(aead_ctx->fixed_nonce));
78 memcpy(aead_ctx->fixed_nonce, fixed_iv, fixed_iv_len);
79 aead_ctx->fixed_nonce_len = fixed_iv_len;
80
81 if (cipher->algorithm_enc & SSL_CHACHA20POLY1305) {
82 /* The fixed nonce into the actual nonce (the sequence number). */
83 aead_ctx->xor_fixed_nonce = 1;
84 aead_ctx->variable_nonce_len = 8;
85 } else {
86 /* The fixed IV is prepended to the nonce. */
87 assert(fixed_iv_len <= aead_ctx->variable_nonce_len);
88 aead_ctx->variable_nonce_len -= fixed_iv_len;
89 }
90
91 /* AES-GCM uses an explicit nonce. */
92 if (cipher->algorithm_enc & (SSL_AES128GCM | SSL_AES256GCM)) {
93 aead_ctx->variable_nonce_included_in_record = 1;
94 }
95 } else {
96 aead_ctx->variable_nonce_included_in_record = 1;
97 aead_ctx->random_variable_nonce = 1;
98 aead_ctx->omit_length_in_ad = 1;
99 aead_ctx->omit_version_in_ad = (version == SSL3_VERSION);
100 }
101
102 return aead_ctx;
103 }
104
SSL_AEAD_CTX_free(SSL_AEAD_CTX * aead)105 void SSL_AEAD_CTX_free(SSL_AEAD_CTX *aead) {
106 if (aead == NULL) {
107 return;
108 }
109 EVP_AEAD_CTX_cleanup(&aead->ctx);
110 OPENSSL_free(aead);
111 }
112
SSL_AEAD_CTX_explicit_nonce_len(SSL_AEAD_CTX * aead)113 size_t SSL_AEAD_CTX_explicit_nonce_len(SSL_AEAD_CTX *aead) {
114 if (aead != NULL && aead->variable_nonce_included_in_record) {
115 return aead->variable_nonce_len;
116 }
117 return 0;
118 }
119
SSL_AEAD_CTX_max_overhead(SSL_AEAD_CTX * aead)120 size_t SSL_AEAD_CTX_max_overhead(SSL_AEAD_CTX *aead) {
121 if (aead == NULL) {
122 return 0;
123 }
124 return EVP_AEAD_max_overhead(aead->ctx.aead) +
125 SSL_AEAD_CTX_explicit_nonce_len(aead);
126 }
127
128 /* ssl_aead_ctx_get_ad writes the additional data for |aead| into |out| and
129 * returns the number of bytes written. */
ssl_aead_ctx_get_ad(SSL_AEAD_CTX * aead,uint8_t out[13],uint8_t type,uint16_t wire_version,const uint8_t seqnum[8],size_t plaintext_len)130 static size_t ssl_aead_ctx_get_ad(SSL_AEAD_CTX *aead, uint8_t out[13],
131 uint8_t type, uint16_t wire_version,
132 const uint8_t seqnum[8],
133 size_t plaintext_len) {
134 memcpy(out, seqnum, 8);
135 size_t len = 8;
136 out[len++] = type;
137 if (!aead->omit_version_in_ad) {
138 out[len++] = (uint8_t)(wire_version >> 8);
139 out[len++] = (uint8_t)wire_version;
140 }
141 if (!aead->omit_length_in_ad) {
142 out[len++] = (uint8_t)(plaintext_len >> 8);
143 out[len++] = (uint8_t)plaintext_len;
144 }
145 return len;
146 }
147
SSL_AEAD_CTX_open(SSL_AEAD_CTX * aead,uint8_t * out,size_t * out_len,size_t max_out,uint8_t type,uint16_t wire_version,const uint8_t seqnum[8],const uint8_t * in,size_t in_len)148 int SSL_AEAD_CTX_open(SSL_AEAD_CTX *aead, uint8_t *out, size_t *out_len,
149 size_t max_out, uint8_t type, uint16_t wire_version,
150 const uint8_t seqnum[8], const uint8_t *in,
151 size_t in_len) {
152 if (aead == NULL) {
153 /* Handle the initial NULL cipher. */
154 if (in_len > max_out) {
155 OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
156 return 0;
157 }
158 memmove(out, in, in_len);
159 *out_len = in_len;
160 return 1;
161 }
162
163 /* TLS 1.2 AEADs include the length in the AD and are assumed to have fixed
164 * overhead. Otherwise the parameter is unused. */
165 size_t plaintext_len = 0;
166 if (!aead->omit_length_in_ad) {
167 size_t overhead = SSL_AEAD_CTX_max_overhead(aead);
168 if (in_len < overhead) {
169 /* Publicly invalid. */
170 OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_PACKET_LENGTH);
171 return 0;
172 }
173 plaintext_len = in_len - overhead;
174 }
175 uint8_t ad[13];
176 size_t ad_len = ssl_aead_ctx_get_ad(aead, ad, type, wire_version, seqnum,
177 plaintext_len);
178
179 /* Assemble the nonce. */
180 uint8_t nonce[EVP_AEAD_MAX_NONCE_LENGTH];
181 size_t nonce_len = 0;
182
183 /* Prepend the fixed nonce, or left-pad with zeros if XORing. */
184 if (aead->xor_fixed_nonce) {
185 nonce_len = aead->fixed_nonce_len - aead->variable_nonce_len;
186 memset(nonce, 0, nonce_len);
187 } else {
188 memcpy(nonce, aead->fixed_nonce, aead->fixed_nonce_len);
189 nonce_len += aead->fixed_nonce_len;
190 }
191
192 /* Add the variable nonce. */
193 if (aead->variable_nonce_included_in_record) {
194 if (in_len < aead->variable_nonce_len) {
195 /* Publicly invalid. */
196 OPENSSL_PUT_ERROR(SSL, SSL_R_BAD_PACKET_LENGTH);
197 return 0;
198 }
199 memcpy(nonce + nonce_len, in, aead->variable_nonce_len);
200 in += aead->variable_nonce_len;
201 in_len -= aead->variable_nonce_len;
202 } else {
203 assert(aead->variable_nonce_len == 8);
204 memcpy(nonce + nonce_len, seqnum, aead->variable_nonce_len);
205 }
206 nonce_len += aead->variable_nonce_len;
207
208 /* XOR the fixed nonce, if necessary. */
209 if (aead->xor_fixed_nonce) {
210 assert(nonce_len == aead->fixed_nonce_len);
211 size_t i;
212 for (i = 0; i < aead->fixed_nonce_len; i++) {
213 nonce[i] ^= aead->fixed_nonce[i];
214 }
215 }
216
217 return EVP_AEAD_CTX_open(&aead->ctx, out, out_len, max_out, nonce, nonce_len,
218 in, in_len, ad, ad_len);
219 }
220
SSL_AEAD_CTX_seal(SSL_AEAD_CTX * aead,uint8_t * out,size_t * out_len,size_t max_out,uint8_t type,uint16_t wire_version,const uint8_t seqnum[8],const uint8_t * in,size_t in_len)221 int SSL_AEAD_CTX_seal(SSL_AEAD_CTX *aead, uint8_t *out, size_t *out_len,
222 size_t max_out, uint8_t type, uint16_t wire_version,
223 const uint8_t seqnum[8], const uint8_t *in,
224 size_t in_len) {
225 if (aead == NULL) {
226 /* Handle the initial NULL cipher. */
227 if (in_len > max_out) {
228 OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
229 return 0;
230 }
231 memmove(out, in, in_len);
232 *out_len = in_len;
233 return 1;
234 }
235
236 uint8_t ad[13];
237 size_t ad_len = ssl_aead_ctx_get_ad(aead, ad, type, wire_version, seqnum,
238 in_len);
239
240 /* Assemble the nonce. */
241 uint8_t nonce[EVP_AEAD_MAX_NONCE_LENGTH];
242 size_t nonce_len = 0;
243
244 /* Prepend the fixed nonce, or left-pad with zeros if XORing. */
245 if (aead->xor_fixed_nonce) {
246 nonce_len = aead->fixed_nonce_len - aead->variable_nonce_len;
247 memset(nonce, 0, nonce_len);
248 } else {
249 memcpy(nonce, aead->fixed_nonce, aead->fixed_nonce_len);
250 nonce_len += aead->fixed_nonce_len;
251 }
252
253 /* Select the variable nonce. */
254 if (aead->random_variable_nonce) {
255 assert(aead->variable_nonce_included_in_record);
256 if (!RAND_bytes(nonce + nonce_len, aead->variable_nonce_len)) {
257 return 0;
258 }
259 } else {
260 /* When sending we use the sequence number as the variable part of the
261 * nonce. */
262 assert(aead->variable_nonce_len == 8);
263 memcpy(nonce + nonce_len, seqnum, aead->variable_nonce_len);
264 }
265 nonce_len += aead->variable_nonce_len;
266
267 /* Emit the variable nonce if included in the record. */
268 size_t extra_len = 0;
269 if (aead->variable_nonce_included_in_record) {
270 assert(!aead->xor_fixed_nonce);
271 if (max_out < aead->variable_nonce_len) {
272 OPENSSL_PUT_ERROR(SSL, SSL_R_BUFFER_TOO_SMALL);
273 return 0;
274 }
275 if (out < in + in_len && in < out + aead->variable_nonce_len) {
276 OPENSSL_PUT_ERROR(SSL, SSL_R_OUTPUT_ALIASES_INPUT);
277 return 0;
278 }
279 memcpy(out, nonce + aead->fixed_nonce_len, aead->variable_nonce_len);
280 extra_len = aead->variable_nonce_len;
281 out += aead->variable_nonce_len;
282 max_out -= aead->variable_nonce_len;
283 }
284
285 /* XOR the fixed nonce, if necessary. */
286 if (aead->xor_fixed_nonce) {
287 assert(nonce_len == aead->fixed_nonce_len);
288 size_t i;
289 for (i = 0; i < aead->fixed_nonce_len; i++) {
290 nonce[i] ^= aead->fixed_nonce[i];
291 }
292 }
293
294 if (!EVP_AEAD_CTX_seal(&aead->ctx, out, out_len, max_out, nonce, nonce_len,
295 in, in_len, ad, ad_len)) {
296 return 0;
297 }
298 *out_len += extra_len;
299 return 1;
300 }
301