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/* Copyright 2018-2019 New Vector Ltd
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License 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 "olm/sas.h"
#include "olm/base64.h"
#include "olm/crypto.h"
#include "olm/error.h"
#include "olm/memory.h"
struct OlmSAS {
enum OlmErrorCode last_error;
struct _olm_curve25519_key_pair curve25519_key;
uint8_t secret[CURVE25519_SHARED_SECRET_LENGTH];
int their_key_set;
};
const char * olm_sas_last_error(
const OlmSAS * sas
) {
return _olm_error_to_string(sas->last_error);
}
enum OlmErrorCode olm_sas_last_error_code(
const OlmSAS * sas
) {
return sas->last_error;
}
size_t olm_sas_size(void) {
return sizeof(OlmSAS);
}
OlmSAS * olm_sas(
void * memory
) {
_olm_unset(memory, sizeof(OlmSAS));
return (OlmSAS *) memory;
}
size_t olm_clear_sas(
OlmSAS * sas
) {
_olm_unset(sas, sizeof(OlmSAS));
return sizeof(OlmSAS);
}
size_t olm_create_sas_random_length(const OlmSAS * sas) {
return CURVE25519_KEY_LENGTH;
}
size_t olm_create_sas(
OlmSAS * sas,
void * random, size_t random_length
) {
if (random_length < olm_create_sas_random_length(sas)) {
sas->last_error = OLM_NOT_ENOUGH_RANDOM;
return (size_t)-1;
}
_olm_crypto_curve25519_generate_key((uint8_t *) random, &sas->curve25519_key);
sas->their_key_set = 0;
return 0;
}
size_t olm_sas_pubkey_length(const OlmSAS * sas) {
return _olm_encode_base64_length(CURVE25519_KEY_LENGTH);
}
size_t olm_sas_get_pubkey(
OlmSAS * sas,
void * pubkey, size_t pubkey_length
) {
if (pubkey_length < olm_sas_pubkey_length(sas)) {
sas->last_error = OLM_OUTPUT_BUFFER_TOO_SMALL;
return (size_t)-1;
}
_olm_encode_base64(
(const uint8_t *)sas->curve25519_key.public_key.public_key,
CURVE25519_KEY_LENGTH,
(uint8_t *)pubkey
);
return 0;
}
size_t olm_sas_set_their_key(
OlmSAS *sas,
void * their_key, size_t their_key_length
) {
if (their_key_length < olm_sas_pubkey_length(sas)) {
sas->last_error = OLM_INPUT_BUFFER_TOO_SMALL;
return (size_t)-1;
}
size_t ret = _olm_decode_base64(their_key, their_key_length, their_key);
if (ret == (size_t)-1) {
sas->last_error = OLM_INVALID_BASE64;
return (size_t)-1;
}
_olm_crypto_curve25519_shared_secret(&sas->curve25519_key, their_key, sas->secret);
sas->their_key_set = 1;
return 0;
}
int olm_sas_is_their_key_set(
const OlmSAS *sas
) {
return sas->their_key_set;
}
size_t olm_sas_generate_bytes(
OlmSAS * sas,
const void * info, size_t info_length,
void * output, size_t output_length
) {
if (!sas->their_key_set) {
sas->last_error = OLM_SAS_THEIR_KEY_NOT_SET;
return (size_t)-1;
}
_olm_crypto_hkdf_sha256(
sas->secret, sizeof(sas->secret),
NULL, 0,
(const uint8_t *) info, info_length,
output, output_length
);
return 0;
}
size_t olm_sas_mac_length(
const OlmSAS *sas
) {
return _olm_encode_base64_length(SHA256_OUTPUT_LENGTH);
}
// A version of the calculate mac function that produces base64 strings that are
// compatible with other base64 implementations.
size_t olm_sas_calculate_mac_fixed_base64(
OlmSAS * sas,
const void * input, size_t input_length,
const void * info, size_t info_length,
void * mac, size_t mac_length
) {
if (mac_length < olm_sas_mac_length(sas)) {
sas->last_error = OLM_OUTPUT_BUFFER_TOO_SMALL;
return (size_t)-1;
}
if (!sas->their_key_set) {
sas->last_error = OLM_SAS_THEIR_KEY_NOT_SET;
return (size_t)-1;
}
uint8_t key[32];
_olm_crypto_hkdf_sha256(
sas->secret, sizeof(sas->secret),
NULL, 0,
(const uint8_t *) info, info_length,
key, 32
);
uint8_t temp_mac[32];
_olm_crypto_hmac_sha256(key, 32, input, input_length, temp_mac);
_olm_encode_base64((const uint8_t *)temp_mac, SHA256_OUTPUT_LENGTH, (uint8_t *)mac);
return 0;
}
size_t olm_sas_calculate_mac(
OlmSAS * sas,
const void * input, size_t input_length,
const void * info, size_t info_length,
void * mac, size_t mac_length
) {
if (mac_length < olm_sas_mac_length(sas)) {
sas->last_error = OLM_OUTPUT_BUFFER_TOO_SMALL;
return (size_t)-1;
}
if (!sas->their_key_set) {
sas->last_error = OLM_SAS_THEIR_KEY_NOT_SET;
return (size_t)-1;
}
uint8_t key[32];
_olm_crypto_hkdf_sha256(
sas->secret, sizeof(sas->secret),
NULL, 0,
(const uint8_t *) info, info_length,
key, 32
);
_olm_crypto_hmac_sha256(key, 32, input, input_length, mac);
_olm_encode_base64((const uint8_t *)mac, SHA256_OUTPUT_LENGTH, (uint8_t *)mac);
return 0;
}
// for compatibility with an old version of Riot
size_t olm_sas_calculate_mac_long_kdf(
OlmSAS * sas,
const void * input, size_t input_length,
const void * info, size_t info_length,
void * mac, size_t mac_length
) {
if (mac_length < olm_sas_mac_length(sas)) {
sas->last_error = OLM_OUTPUT_BUFFER_TOO_SMALL;
return (size_t)-1;
}
if (!sas->their_key_set) {
sas->last_error = OLM_SAS_THEIR_KEY_NOT_SET;
return (size_t)-1;
}
uint8_t key[256];
_olm_crypto_hkdf_sha256(
sas->secret, sizeof(sas->secret),
NULL, 0,
(const uint8_t *) info, info_length,
key, 256
);
_olm_crypto_hmac_sha256(key, 256, input, input_length, mac);
_olm_encode_base64((const uint8_t *)mac, SHA256_OUTPUT_LENGTH, (uint8_t *)mac);
return 0;
}
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