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sas: Introduce a new calculate mac function to fix the base64 issue 

Since it's important to keep backwards compatibility introduce a new
function to calculate the MAC using a SAS object.

Modifying the existing functions would break compatibility with older
releases of libolm.
sas-base64-fix
Damir Jelić 2021-02-02 16:58:28 +01:00
parent 4e927eb1cf
commit f46577a06a
1 changed files with 32 additions and 6 deletions
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38
src/sas.c
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@ -131,7 +131,9 @@ size_t olm_sas_mac_length(
return _olm_encode_base64_length(SHA256_OUTPUT_LENGTH);
}
size_t olm_sas_calculate_mac(
// 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,
@ -160,6 +162,33 @@ size_t olm_sas_calculate_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,
@ -182,10 +211,7 @@ size_t olm_sas_calculate_mac_long_kdf(
(const uint8_t *) info, info_length,
key, 256
);
uint8_t temp_mac[32];
_olm_crypto_hmac_sha256(key, 256, input, input_length, temp_mac);
_olm_encode_base64((const uint8_t *)temp_mac, SHA256_OUTPUT_LENGTH, (uint8_t *)mac);
_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;
}