1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
|
/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License").
* You may not use this file except in compliance with the License.
* A copy of the License is located at
*
* http://aws.amazon.com/apache2.0
*
* or in the "license" file accompanying this file. This file is distributed
* on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
* express or implied. See the License for the specific language governing
* permissions and limitations under the License.
*/
#include "crypto/s2n_cipher.h"
#include "crypto/s2n_hmac.h"
#include "crypto/s2n_sequence.h"
#include "error/s2n_errno.h"
#include "stuffer/s2n_stuffer.h"
#include "tls/s2n_cipher_suites.h"
#include "tls/s2n_connection.h"
#include "tls/s2n_crypto.h"
#include "tls/s2n_record.h"
#include "tls/s2n_record_read.h"
#include "utils/s2n_annotations.h"
#include "utils/s2n_blob.h"
#include "utils/s2n_safety.h"
int s2n_record_parse_aead(
const struct s2n_cipher_suite *cipher_suite,
struct s2n_connection *conn,
uint8_t content_type,
uint16_t encrypted_length,
uint8_t *implicit_iv,
struct s2n_hmac_state *mac,
uint8_t *sequence_number,
struct s2n_session_key *session_key)
{
const int is_tls13_record = cipher_suite->record_alg->flags & S2N_TLS13_RECORD_AEAD_NONCE;
/* TLS 1.3 record protection uses a different 5 byte associated data than TLS 1.2's */
s2n_stack_blob(aad, is_tls13_record ? S2N_TLS13_AAD_LEN : S2N_TLS_MAX_AAD_LEN, S2N_TLS_MAX_AAD_LEN);
struct s2n_blob en = { 0 };
POSIX_GUARD(s2n_blob_init(&en, s2n_stuffer_raw_read(&conn->in, encrypted_length), encrypted_length));
POSIX_ENSURE_REF(en.data);
/* In AEAD mode, the explicit IV is in the record */
POSIX_ENSURE_GTE(en.size, cipher_suite->record_alg->cipher->io.aead.record_iv_size);
uint8_t aad_iv[S2N_TLS_MAX_IV_LEN] = { 0 };
struct s2n_blob iv = { 0 };
POSIX_GUARD(s2n_blob_init(&iv, aad_iv, sizeof(aad_iv)));
struct s2n_stuffer iv_stuffer = { 0 };
POSIX_GUARD(s2n_stuffer_init(&iv_stuffer, &iv));
if (cipher_suite->record_alg->flags & S2N_TLS12_AES_GCM_AEAD_NONCE) {
/* Partially explicit nonce. See RFC 5288 Section 3 */
POSIX_GUARD(s2n_stuffer_write_bytes(&iv_stuffer, implicit_iv, cipher_suite->record_alg->cipher->io.aead.fixed_iv_size));
POSIX_GUARD(s2n_stuffer_write_bytes(&iv_stuffer, en.data, cipher_suite->record_alg->cipher->io.aead.record_iv_size));
} else if (cipher_suite->record_alg->flags & S2N_TLS12_CHACHA_POLY_AEAD_NONCE || is_tls13_record) {
/* Fully implicit nonce.
* This is introduced with ChaChaPoly with RFC 7905 Section 2
* and also used for TLS 1.3 record protection (RFC 8446 Section 5.2).
*
* In these cipher modes, the sequence number (64 bits) is left padded by 4 bytes
* to align and xor-ed with the 96-bit IV.
**/
uint8_t four_zeroes[4] = { 0 };
POSIX_GUARD(s2n_stuffer_write_bytes(&iv_stuffer, four_zeroes, 4));
POSIX_GUARD(s2n_stuffer_write_bytes(&iv_stuffer, sequence_number, S2N_TLS_SEQUENCE_NUM_LEN));
for (int i = 0; i < cipher_suite->record_alg->cipher->io.aead.fixed_iv_size; i++) {
S2N_INVARIANT(i <= cipher_suite->record_alg->cipher->io.aead.fixed_iv_size);
aad_iv[i] = aad_iv[i] ^ implicit_iv[i];
}
} else {
POSIX_BAIL(S2N_ERR_INVALID_NONCE_TYPE);
}
/* Set the IV size to the amount of data written */
iv.size = s2n_stuffer_data_available(&iv_stuffer);
uint16_t payload_length = encrypted_length;
/* remove the AEAD overhead from the record size */
POSIX_ENSURE_GTE(payload_length, cipher_suite->record_alg->cipher->io.aead.record_iv_size + cipher_suite->record_alg->cipher->io.aead.tag_size);
payload_length -= cipher_suite->record_alg->cipher->io.aead.record_iv_size;
payload_length -= cipher_suite->record_alg->cipher->io.aead.tag_size;
if (is_tls13_record) {
POSIX_GUARD_RESULT(s2n_tls13_aead_aad_init(payload_length, cipher_suite->record_alg->cipher->io.aead.tag_size, &aad));
} else {
POSIX_GUARD_RESULT(s2n_aead_aad_init(conn, sequence_number, content_type, payload_length, &aad));
}
/* Decrypt stuff! */
/* Skip explicit IV for decryption */
en.size -= cipher_suite->record_alg->cipher->io.aead.record_iv_size;
en.data += cipher_suite->record_alg->cipher->io.aead.record_iv_size;
/* Check that we have some data to decrypt */
POSIX_ENSURE_NE(en.size, 0);
POSIX_GUARD(cipher_suite->record_alg->cipher->io.aead.decrypt(session_key, &iv, &aad, &en, &en));
struct s2n_blob seq = { 0 };
POSIX_GUARD(s2n_blob_init(&seq, sequence_number, S2N_TLS_SEQUENCE_NUM_LEN));
POSIX_GUARD(s2n_increment_sequence_number(&seq));
/* O.k., we've successfully read and decrypted the record, now we need to align the stuffer
* for reading the plaintext data.
*/
POSIX_GUARD(s2n_stuffer_reread(&conn->in));
POSIX_GUARD(s2n_stuffer_reread(&conn->header_in));
/* Skip the IV, if any */
if (conn->actual_protocol_version >= S2N_TLS12) {
POSIX_GUARD(s2n_stuffer_skip_read(&conn->in, cipher_suite->record_alg->cipher->io.aead.record_iv_size));
}
/* Truncate and wipe the MAC and any padding */
POSIX_GUARD(s2n_stuffer_wipe_n(&conn->in, s2n_stuffer_data_available(&conn->in) - payload_length));
conn->in_status = PLAINTEXT;
return 0;
}
|
