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implicitly generate HMAC-secret

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This commit is contained in:
Fabian Kaczmarczyck
2020-12-08 18:12:48 +01:00
parent f475aa5d28
commit 90def7dfd3
5 changed files with 112 additions and 178 deletions
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30
src/ctap/pin_protocol_v1.rs
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@@ -56,23 +56,16 @@ fn verify_pin_auth(hmac_key: &[u8], hmac_contents: &[u8], pin_auth: &[u8]) -> bo
fn encrypt_hmac_secret_output(
shared_secret: &[u8; 32],
salt_enc: &[u8],
cred_random: &[u8],
cred_random: &[u8; 32],
) -> Result<Vec<u8>, Ctap2StatusCode> {
if salt_enc.len() != 32 && salt_enc.len() != 64 {
return Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_EXTENSION);
}
if cred_random.len() != 32 {
// We are strict here. We need at least 32 byte, but expect exactly 32.
return Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_EXTENSION);
}
let aes_enc_key = crypto::aes256::EncryptionKey::new(shared_secret);
let aes_dec_key = crypto::aes256::DecryptionKey::new(&aes_enc_key);
// The specification specifically asks for a zero IV.
let iv = [0u8; 16];
let mut cred_random_secret = [0u8; 32];
cred_random_secret.copy_from_slice(cred_random);
// With the if clause restriction above, block_len can only be 2 or 4.
let block_len = salt_enc.len() / 16;
let mut blocks = vec![[0u8; 16]; block_len];
@@ -84,7 +77,7 @@ fn encrypt_hmac_secret_output(
let mut decrypted_salt1 = [0u8; 32];
decrypted_salt1[..16].copy_from_slice(&blocks[0]);
decrypted_salt1[16..].copy_from_slice(&blocks[1]);
let output1 = hmac_256::<Sha256>(&cred_random_secret, &decrypted_salt1[..]);
let output1 = hmac_256::<Sha256>(&cred_random[..], &decrypted_salt1[..]);
for i in 0..2 {
blocks[i].copy_from_slice(&output1[16 * i..16 * (i + 1)]);
}
@@ -93,7 +86,7 @@ fn encrypt_hmac_secret_output(
let mut decrypted_salt2 = [0u8; 32];
decrypted_salt2[..16].copy_from_slice(&blocks[2]);
decrypted_salt2[16..].copy_from_slice(&blocks[3]);
let output2 = hmac_256::<Sha256>(&cred_random_secret, &decrypted_salt2[..]);
let output2 = hmac_256::<Sha256>(&cred_random[..], &decrypted_salt2[..]);
for i in 0..2 {
blocks[i + 2].copy_from_slice(&output2[16 * i..16 * (i + 1)]);
}
@@ -588,7 +581,7 @@ impl PinProtocolV1 {
pub fn process_hmac_secret(
&self,
hmac_secret_input: GetAssertionHmacSecretInput,
cred_random: &Option<Vec<u8>>,
cred_random: &[u8; 32],
) -> Result<Vec<u8>, Ctap2StatusCode> {
let GetAssertionHmacSecretInput {
key_agreement,
@@ -602,12 +595,7 @@ impl PinProtocolV1 {
// Hard to tell what the correct error code here is.
return Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_EXTENSION);
}
match cred_random {
Some(cr) => encrypt_hmac_secret_output(&shared_secret, &salt_enc[..], cr),
// This is the case if the credential was not created with HMAC-secret.
None => Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_EXTENSION),
}
encrypt_hmac_secret_output(&shared_secret, &salt_enc[..], cred_random)
}
#[cfg(feature = "with_ctap2_1")]
@@ -1195,14 +1183,6 @@ mod test {
let output = encrypt_hmac_secret_output(&shared_secret, &salt_enc, &cred_random);
assert_eq!(output.unwrap().len(), 64);
let salt_enc = [0x5E; 32];
let cred_random = [0xC9; 33];
let output = encrypt_hmac_secret_output(&shared_secret, &salt_enc, &cred_random);
assert_eq!(
output,
Err(Ctap2StatusCode::CTAP2_ERR_UNSUPPORTED_EXTENSION)
);
let mut salt_enc = [0x00; 32];
let cred_random = [0xC9; 32];