Hi Marcel,
On 14 May 2014 17:07, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
> Hi Lukas,
>
>> This patch adds support to generate hash using AES-CMAC algorithm
>> ---
>> src/shared/crypto.c | 37 +++++++++++++++++++++++++++++++++++++
>> src/shared/crypto.h | 4 ++++
>> 2 files changed, 41 insertions(+)
>>
>> diff --git a/src/shared/crypto.c b/src/shared/crypto.c
>> index f0b2979..a0bcc7b 100644
>> --- a/src/shared/crypto.c
>> +++ b/src/shared/crypto.c
>> @@ -256,6 +256,43 @@ static inline void swap128(const uint8_t src[16], uint8_t dst[16])
>> dst[15 - i] = src[i];
>> }
>>
>> +bool bt_crypto_cmac_aes_hash(struct bt_crypto *crypto,
>> + const uint8_t key[16],
>> + const uint8_t *m, uint16_t m_len,
>> + uint8_t hash[12])
>> +{
>> + int fd;
>> + int len;
>> + uint8_t tmp[16], out[16];
>> +
>> + if (!crypto)
>> + return false;
>> +
>> + /* The most significant octet of key corresponds to key[0] */
>> + swap128(key, tmp);
>> +
>> + fd = alg_new(crypto->cmac_aes, tmp, 16);
>> + if (fd < 0)
>> + return false;
>> +
>> + len = send(fd, m, m_len, 0);
>> + if (len < 0)
>> + return false;
>> +
>> + len = read(fd, out, 16);
>> + if (len < 0)
>> + return false;
>> +
>> + /*
>> + * The most significant octet of hash corresponds to out[0] - swap it.
>> + * Then truncate in most significant bit first order to a length of
>> + * 12 octets
>> + */
>> + swap128(out, tmp);
>> + memcpy(hash, tmp + 4, 12);
>> +
>> + return true;
>> +}
>> /*
>> * Security function e
>> *
>> diff --git a/src/shared/crypto.h b/src/shared/crypto.h
>> index cae8daa..05888b9 100644
>> --- a/src/shared/crypto.h
>> +++ b/src/shared/crypto.h
>> @@ -46,3 +46,7 @@ bool bt_crypto_c1(struct bt_crypto *crypto, const uint8_t k[16],
>> bool bt_crypto_s1(struct bt_crypto *crypto, const uint8_t k[16],
>> const uint8_t r1[16], const uint8_t r2[16],
>> uint8_t res[16]);
>> +bool bt_crypto_cmac_aes_hash(struct bt_crypto *crypto,
>> + const uint8_t key[16],
>> + const uint8_t *m, uint16_t m_len,
>> + uint8_t hash[12]);
>
> we are using the cryptographic names from the Bluetooth specification cryptographic toolbox. I bet this one has a proper function name as well. So lets use that one.
Actually it does not have other name - AES-CMAC is referenced in
section "2.4.5 Signing algorithm" of SMP specification as algorithm to
be used for signing. Perhaps we can call it 'bt_crypto_le_sign' since
it's used for signing LE data (as per spec) or just leave as-is.
BR,
Andrzej
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