1 /*
2 * Copyright (c) 2018 Thomas Pornin <pornin@bolet.org>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25 #include "inner.h"
26
27 /*
28 * CCM initialisation. This does everything except setting the vtable,
29 * which depends on whether this is a context for encrypting or for
30 * decrypting.
31 */
32 static void
gen_ccm_init(br_sslrec_ccm_context * cc,const br_block_ctrcbc_class * bc_impl,const void * key,size_t key_len,const void * iv,size_t tag_len)33 gen_ccm_init(br_sslrec_ccm_context *cc,
34 const br_block_ctrcbc_class *bc_impl,
35 const void *key, size_t key_len,
36 const void *iv, size_t tag_len)
37 {
38 cc->seq = 0;
39 bc_impl->init(&cc->bc.vtable, key, key_len);
40 memcpy(cc->iv, iv, sizeof cc->iv);
41 cc->tag_len = tag_len;
42 }
43
44 static void
in_ccm_init(br_sslrec_ccm_context * cc,const br_block_ctrcbc_class * bc_impl,const void * key,size_t key_len,const void * iv,size_t tag_len)45 in_ccm_init(br_sslrec_ccm_context *cc,
46 const br_block_ctrcbc_class *bc_impl,
47 const void *key, size_t key_len,
48 const void *iv, size_t tag_len)
49 {
50 cc->vtable.in = &br_sslrec_in_ccm_vtable;
51 gen_ccm_init(cc, bc_impl, key, key_len, iv, tag_len);
52 }
53
54 static int
ccm_check_length(const br_sslrec_ccm_context * cc,size_t rlen)55 ccm_check_length(const br_sslrec_ccm_context *cc, size_t rlen)
56 {
57 /*
58 * CCM overhead is 8 bytes for nonce_explicit, and the tag
59 * (normally 8 or 16 bytes, depending on cipher suite).
60 */
61 size_t over;
62
63 over = 8 + cc->tag_len;
64 return rlen >= over && rlen <= (16384 + over);
65 }
66
67 static unsigned char *
ccm_decrypt(br_sslrec_ccm_context * cc,int record_type,unsigned version,void * data,size_t * data_len)68 ccm_decrypt(br_sslrec_ccm_context *cc,
69 int record_type, unsigned version, void *data, size_t *data_len)
70 {
71 br_ccm_context zc;
72 unsigned char *buf;
73 unsigned char nonce[12], header[13];
74 size_t len;
75
76 buf = (unsigned char *)data + 8;
77 len = *data_len - (8 + cc->tag_len);
78
79 /*
80 * Make nonce (implicit + explicit parts).
81 */
82 memcpy(nonce, cc->iv, sizeof cc->iv);
83 memcpy(nonce + 4, data, 8);
84
85 /*
86 * Assemble synthetic header for the AAD.
87 */
88 br_enc64be(header, cc->seq ++);
89 header[8] = (unsigned char)record_type;
90 br_enc16be(header + 9, version);
91 br_enc16be(header + 11, len);
92
93 /*
94 * Perform CCM decryption.
95 */
96 br_ccm_init(&zc, &cc->bc.vtable);
97 br_ccm_reset(&zc, nonce, sizeof nonce, sizeof header, len, cc->tag_len);
98 br_ccm_aad_inject(&zc, header, sizeof header);
99 br_ccm_flip(&zc);
100 br_ccm_run(&zc, 0, buf, len);
101 if (!br_ccm_check_tag(&zc, buf + len)) {
102 return NULL;
103 }
104 *data_len = len;
105 return buf;
106 }
107
108 /* see bearssl_ssl.h */
109 const br_sslrec_in_ccm_class br_sslrec_in_ccm_vtable = {
110 {
111 sizeof(br_sslrec_ccm_context),
112 (int (*)(const br_sslrec_in_class *const *, size_t))
113 &ccm_check_length,
114 (unsigned char *(*)(const br_sslrec_in_class **,
115 int, unsigned, void *, size_t *))
116 &ccm_decrypt
117 },
118 (void (*)(const br_sslrec_in_ccm_class **,
119 const br_block_ctrcbc_class *, const void *, size_t,
120 const void *, size_t))
121 &in_ccm_init
122 };
123
124 static void
out_ccm_init(br_sslrec_ccm_context * cc,const br_block_ctrcbc_class * bc_impl,const void * key,size_t key_len,const void * iv,size_t tag_len)125 out_ccm_init(br_sslrec_ccm_context *cc,
126 const br_block_ctrcbc_class *bc_impl,
127 const void *key, size_t key_len,
128 const void *iv, size_t tag_len)
129 {
130 cc->vtable.out = &br_sslrec_out_ccm_vtable;
131 gen_ccm_init(cc, bc_impl, key, key_len, iv, tag_len);
132 }
133
134 static void
ccm_max_plaintext(const br_sslrec_ccm_context * cc,size_t * start,size_t * end)135 ccm_max_plaintext(const br_sslrec_ccm_context *cc,
136 size_t *start, size_t *end)
137 {
138 size_t len;
139
140 *start += 8;
141 len = *end - *start - cc->tag_len;
142 if (len > 16384) {
143 len = 16384;
144 }
145 *end = *start + len;
146 }
147
148 static unsigned char *
ccm_encrypt(br_sslrec_ccm_context * cc,int record_type,unsigned version,void * data,size_t * data_len)149 ccm_encrypt(br_sslrec_ccm_context *cc,
150 int record_type, unsigned version, void *data, size_t *data_len)
151 {
152 br_ccm_context zc;
153 unsigned char *buf;
154 unsigned char nonce[12], header[13];
155 size_t len;
156
157 buf = (unsigned char *)data;
158 len = *data_len;
159
160 /*
161 * Make nonce; the explicit part is an encoding of the sequence
162 * number.
163 */
164 memcpy(nonce, cc->iv, sizeof cc->iv);
165 br_enc64be(nonce + 4, cc->seq);
166
167 /*
168 * Assemble synthetic header for the AAD.
169 */
170 br_enc64be(header, cc->seq ++);
171 header[8] = (unsigned char)record_type;
172 br_enc16be(header + 9, version);
173 br_enc16be(header + 11, len);
174
175 /*
176 * Perform CCM encryption.
177 */
178 br_ccm_init(&zc, &cc->bc.vtable);
179 br_ccm_reset(&zc, nonce, sizeof nonce, sizeof header, len, cc->tag_len);
180 br_ccm_aad_inject(&zc, header, sizeof header);
181 br_ccm_flip(&zc);
182 br_ccm_run(&zc, 1, buf, len);
183 br_ccm_get_tag(&zc, buf + len);
184
185 /*
186 * Assemble header and adjust pointer/length.
187 */
188 len += 8 + cc->tag_len;
189 buf -= 13;
190 memcpy(buf + 5, nonce + 4, 8);
191 buf[0] = (unsigned char)record_type;
192 br_enc16be(buf + 1, version);
193 br_enc16be(buf + 3, len);
194 *data_len = len + 5;
195 return buf;
196 }
197
198 /* see bearssl_ssl.h */
199 const br_sslrec_out_ccm_class br_sslrec_out_ccm_vtable = {
200 {
201 sizeof(br_sslrec_ccm_context),
202 (void (*)(const br_sslrec_out_class *const *,
203 size_t *, size_t *))
204 &ccm_max_plaintext,
205 (unsigned char *(*)(const br_sslrec_out_class **,
206 int, unsigned, void *, size_t *))
207 &ccm_encrypt
208 },
209 (void (*)(const br_sslrec_out_ccm_class **,
210 const br_block_ctrcbc_class *, const void *, size_t,
211 const void *, size_t))
212 &out_ccm_init
213 };
214