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improved testing in pin_protocol_v1.rs

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This commit is contained in:
Fabian Kaczmarczyck
2020-08-13 05:37:20 +02:00
parent d5fefa2f12
commit 0aabf8210a
1 changed files with 135 additions and 83 deletions
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210
src/ctap/pin_protocol_v1.rs
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@@ -106,17 +106,13 @@ fn encrypt_hmac_secret_output(
Ok(encrypted_output)
}
/// Stores the encrypted new PIN in the persistent storage, if it satisfies the
/// PIN policy. The PIN is decrypted and stripped from its padding. Next, the
/// length of the PIN is checked to fulfill policy requirements. Last, the PIN
/// is hashed, truncated to 16 bytes and persistently stored.
fn check_and_store_new_pin(
persistent_store: &mut PersistentStore,
/// Decrypts the new_pin_enc and outputs the found PIN.
fn decrypt_pin(
aes_dec_key: &crypto::aes256::DecryptionKey,
new_pin_enc: Vec<u8>,
) -> bool {
) -> Option<Vec<u8>> {
if new_pin_enc.len() != PIN_PADDED_LENGTH {
return false;
return None;
}
let iv = [0u8; 16];
// Assuming PIN_PADDED_LENGTH % block_size == 0 here.
@@ -129,12 +125,27 @@ fn check_and_store_new_pin(
// In CTAP 2.1, the specification changed. The new wording might lead to
// different behavior when there are non-zero bytes after zero bytes.
// This implementation consistently ignores those degenerate cases.
let pin: Vec<u8> = blocks
Some(
blocks
.iter()
.flatten()
.cloned()
.take_while(|&c| c != 0)
.collect();
.collect::<Vec<u8>>(),
)
}
/// Stores the encrypted new PIN in the persistent storage, if it satisfies the
/// PIN policy. The PIN is decrypted and stripped from its padding. Next, the
/// length of the PIN is checked to fulfill policy requirements. Last, the PIN
/// is hashed, truncated to 16 bytes and persistently stored.
fn check_and_store_new_pin(
persistent_store: &mut PersistentStore,
aes_dec_key: &crypto::aes256::DecryptionKey,
new_pin_enc: Vec<u8>,
) -> Result<(), Ctap2StatusCode> {
let pin = decrypt_pin(aes_dec_key, new_pin_enc)
.ok_or(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION)?;
#[cfg(feature = "with_ctap2_1")]
let min_pin_length = persistent_store.min_pin_length() as usize;
@@ -142,12 +153,12 @@ fn check_and_store_new_pin(
let min_pin_length = 4;
if pin.len() < min_pin_length || pin.len() == PIN_PADDED_LENGTH {
// TODO(kaczmarczyck) check 4 code point minimum instead
return false;
return Err(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION);
}
let mut pin_hash = [0u8; 16];
pin_hash.copy_from_slice(&Sha256::hash(&pin[..])[..16]);
persistent_store.set_pin_hash(&pin_hash);
true
Ok(())
}
#[cfg(feature = "with_ctap2_1")]
@@ -214,7 +225,7 @@ impl PinProtocolV1 {
let iv = [0u8; 16];
let mut blocks = [[0u8; 16]; 1];
blocks[0].copy_from_slice(&pin_hash_enc[0..PIN_AUTH_LENGTH]);
blocks[0].copy_from_slice(&pin_hash_enc);
cbc_decrypt(aes_dec_key, iv, &mut blocks);
if !bool::from(pin_hash.ct_eq(&blocks[0])) {
@@ -239,16 +250,16 @@ impl PinProtocolV1 {
/// Uses the self-owned and passed halves of the key agreement to generate the
/// shared secret for checking pin_auth and generating a decryption key.
fn create_decryption_key_verified(
fn exchange_decryption_key(
&self,
key_agreement: CoseKey,
pin_auth: &[u8],
message: &[u8],
authenticated_message: &[u8],
) -> Result<crypto::aes256::DecryptionKey, Ctap2StatusCode> {
let pk: crypto::ecdh::PubKey = CoseKey::try_into(key_agreement)?;
let shared_secret = self.key_agreement_key.exchange_x_sha256(&pk);
if !verify_pin_auth(&shared_secret, message, pin_auth) {
if !verify_pin_auth(&shared_secret, authenticated_message, pin_auth) {
return Err(Ctap2StatusCode::CTAP2_ERR_PIN_AUTH_INVALID);
}
@@ -288,10 +299,8 @@ impl PinProtocolV1 {
return Err(Ctap2StatusCode::CTAP2_ERR_PIN_AUTH_INVALID);
}
let pin_decryption_key =
self.create_decryption_key_verified(key_agreement, &pin_auth, &new_pin_enc)?;
if !check_and_store_new_pin(persistent_store, &pin_decryption_key, new_pin_enc) {
return Err(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION);
}
self.exchange_decryption_key(key_agreement, &pin_auth, &new_pin_enc)?;
check_and_store_new_pin(persistent_store, &pin_decryption_key, new_pin_enc)?;
persistent_store.reset_pin_retries();
Ok(())
}
@@ -311,12 +320,10 @@ impl PinProtocolV1 {
let mut auth_param_data = new_pin_enc.clone();
auth_param_data.extend(&pin_hash_enc);
let pin_decryption_key =
self.create_decryption_key_verified(key_agreement, &pin_auth, &auth_param_data)?;
self.exchange_decryption_key(key_agreement, &pin_auth, &auth_param_data)?;
self.verify_pin_hash_enc(rng, persistent_store, &pin_decryption_key, pin_hash_enc)?;
if !check_and_store_new_pin(persistent_store, &pin_decryption_key, new_pin_enc) {
return Err(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION);
}
check_and_store_new_pin(persistent_store, &pin_decryption_key, new_pin_enc)?;
self.pin_uv_auth_token = rng.gen_uniform_u8x32();
Ok(())
}
@@ -345,10 +352,7 @@ impl PinProtocolV1 {
item.copy_from_slice(&self.pin_uv_auth_token[i * 16..(i + 1) * 16]);
}
cbc_encrypt(&token_encryption_key, iv, &mut blocks);
let mut pin_token = vec![];
for item in blocks.iter().take(PIN_TOKEN_LENGTH / 16) {
pin_token.extend(item);
}
let pin_token: Vec<u8> = blocks.iter().flatten().cloned().collect();
#[cfg(feature = "with_ctap2_1")]
{
@@ -415,6 +419,9 @@ impl PinProtocolV1 {
}
// TODO(kaczmarczyck) Values are taken from the (not yet public) new revision
// of CTAP 2.1. The code should link the specification when published.
// From CTAP2.1: "If request contains pinUvAuthParam, the Authenticator calls
// verify(pinUvAuthToken, 32×0xff || 0x0608 || uint32LittleEndian(minPINLength)
// || minPinLengthRPIDs, pinUvAuthParam)"
let mut message = vec![0xFF; 32];
message.extend(&[0x06, 0x08]);
message.extend(&[min_pin_length as u8, 0x00, 0x00, 0x00]);
@@ -644,21 +651,25 @@ mod test {
persistent_store.set_pin_hash(&pin_hash);
}
fn encrypt_standard_pin(shared_secret: &[u8; 32]) -> Vec<u8> {
// Fails on PINs bigger than 64 byte..
fn encrypt_pin(shared_secret: &[u8; 32], pin: Vec<u8>) -> Vec<u8> {
assert!(pin.len() <= 64);
let mut padded_pin = [0u8; 64];
padded_pin[..pin.len()].copy_from_slice(&pin[..]);
let aes_enc_key = crypto::aes256::EncryptionKey::new(shared_secret);
let mut blocks = [[0u8; 16]; 4];
blocks[0][0] = 0x31;
blocks[0][1] = 0x32;
blocks[0][2] = 0x33;
blocks[0][3] = 0x34;
let (b0, b1, b2, b3) = array_refs!(&padded_pin, 16, 16, 16, 16);
blocks[0][..].copy_from_slice(b0);
blocks[1][..].copy_from_slice(b1);
blocks[2][..].copy_from_slice(b2);
blocks[3][..].copy_from_slice(b3);
let iv = [0u8; 16];
cbc_encrypt(&aes_enc_key, iv, &mut blocks);
let mut encrypted_pin = Vec::with_capacity(64);
for b in &blocks {
encrypted_pin.extend(b);
blocks.iter().flatten().cloned().collect::<Vec<u8>>()
}
encrypted_pin
fn encrypt_standard_pin(shared_secret: &[u8; 32]) -> Vec<u8> {
encrypt_pin(shared_secret, vec![0x31, 0x32, 0x33, 0x34])
}
fn encrypt_standard_pin_hash(shared_secret: &[u8; 32]) -> Vec<u8> {
@@ -734,6 +745,29 @@ mod test {
),
Err(Ctap2StatusCode::CTAP2_ERR_PIN_AUTH_BLOCKED)
);
pin_protocol_v1.consecutive_pin_mismatches = 0;
let pin_hash_enc = vec![0x77; PIN_AUTH_LENGTH - 1];
assert_eq!(
pin_protocol_v1.verify_pin_hash_enc(
&mut rng,
&mut persistent_store,
&aes_dec_key,
pin_hash_enc
),
Err(Ctap2StatusCode::CTAP2_ERR_PIN_INVALID)
);
let pin_hash_enc = vec![0x77; PIN_AUTH_LENGTH + 1];
assert_eq!(
pin_protocol_v1.verify_pin_hash_enc(
&mut rng,
&mut persistent_store,
&aes_dec_key,
pin_hash_enc
),
Err(Ctap2StatusCode::CTAP2_ERR_PIN_INVALID)
);
}
#[test]
@@ -1027,14 +1061,12 @@ mod test {
}
#[test]
fn test_check_and_store_new_pin() {
let mut rng = ThreadRng256 {};
let mut persistent_store = PersistentStore::new(&mut rng);
fn test_decrypt_pin() {
let shared_secret = [0x88; 32];
let aes_enc_key = crypto::aes256::EncryptionKey::new(&shared_secret);
let aes_dec_key = crypto::aes256::DecryptionKey::new(&aes_enc_key);
// The PIN "1234" should be accepted.
// "1234"
let new_pin_enc = vec![
0xC0, 0xCF, 0xAE, 0x4C, 0x79, 0x56, 0x87, 0x99, 0xE5, 0x83, 0x4F, 0xE6, 0x4D, 0xFE,
0x53, 0x32, 0x36, 0x0D, 0xF9, 0x1E, 0x47, 0x66, 0x10, 0x5C, 0x63, 0x30, 0x1D, 0xCC,
@@ -1042,53 +1074,73 @@ mod test {
0xEE, 0x01, 0x99, 0x6C, 0xD7, 0xE5, 0x2B, 0xA5, 0x7A, 0x5A, 0xE1, 0xEC, 0x69, 0x31,
0x18, 0x35, 0x06, 0x66, 0x97, 0x84, 0x68, 0xC2,
];
assert!(check_and_store_new_pin(
&mut persistent_store,
&aes_dec_key,
new_pin_enc
));
assert_eq!(
decrypt_pin(&aes_dec_key, new_pin_enc),
Some(vec![0x31, 0x32, 0x33, 0x34]),
);
// The PIN "123" has only 3 characters.
let bad_pin_enc = vec![
// "123"
let new_pin_enc = vec![
0xF3, 0x54, 0x29, 0x17, 0xD4, 0xF8, 0xCD, 0x23, 0x1D, 0x59, 0xED, 0xE5, 0x33, 0x42,
0x13, 0x39, 0x22, 0xBB, 0x91, 0x28, 0x87, 0x6A, 0xF9, 0xB1, 0x80, 0x9C, 0x9D, 0x76,
0xFF, 0xDD, 0xB8, 0xD6, 0x8D, 0x66, 0x99, 0xA2, 0x42, 0x67, 0xB0, 0x5C, 0x82, 0x3F,
0x08, 0x55, 0x8C, 0x04, 0xC5, 0x91, 0xF0, 0xF9, 0x58, 0x44, 0x00, 0x1B, 0x99, 0xA6,
0x7C, 0xC7, 0x2D, 0x43, 0x74, 0x4C, 0x1D, 0x7E,
];
assert!(!check_and_store_new_pin(
&mut persistent_store,
&aes_dec_key,
bad_pin_enc
));
assert_eq!(
decrypt_pin(&aes_dec_key, new_pin_enc),
Some(vec![0x31, 0x32, 0x33]),
);
// The PIN "12'\0'4" (a zero byte where the 3 was) should be rejected.
let bad_pin_enc = vec![
0x32, 0x78, 0x24, 0xCD, 0x25, 0xB7, 0x2F, 0x42, 0x18, 0x08, 0x27, 0x80, 0x21, 0xEA,
0xE9, 0x2C, 0x20, 0x06, 0x7E, 0x17, 0xBA, 0x87, 0xCB, 0x35, 0xB0, 0xB9, 0x57, 0x9B,
0xCB, 0x73, 0x7D, 0xBB, 0x61, 0x0D, 0xBB, 0x70, 0x5F, 0xC3, 0x94, 0x03, 0x64, 0x9A,
0xC6, 0xDF, 0x9C, 0x74, 0x36, 0x97, 0xD4, 0x1B, 0x31, 0xD9, 0x7D, 0x1E, 0x42, 0xAC,
0x18, 0xBA, 0xE0, 0x6C, 0x16, 0x0B, 0x25, 0xCC,
];
assert!(!check_and_store_new_pin(
&mut persistent_store,
&aes_dec_key,
bad_pin_enc
));
// Encrypted PIN is too short.
let new_pin_enc = vec![0x44; 63];
assert_eq!(decrypt_pin(&aes_dec_key, new_pin_enc), None,);
// The last byte of the decrypted PIN is not padding, which is 0x00.
let bad_pin_enc = vec![
0x53, 0x3D, 0xAD, 0x69, 0xB6, 0x1B, 0x5F, 0xAF, 0x0F, 0x26, 0xF1, 0x33, 0xB3, 0xCC,
0x94, 0x26, 0x68, 0xD0, 0xC4, 0x58, 0xD4, 0x2D, 0x3D, 0x8B, 0x6F, 0x1A, 0xA2, 0x0A,
0x44, 0x47, 0xE8, 0x94, 0xF2, 0x2D, 0x99, 0xEB, 0xA1, 0xA6, 0xBE, 0x32, 0x7C, 0x99,
0x2B, 0xB8, 0x9A, 0x15, 0x9C, 0xEA, 0x86, 0x47, 0x4B, 0x5E, 0x6C, 0xA2, 0xE2, 0xB9,
0x0D, 0x85, 0x25, 0xD3, 0x8A, 0x46, 0x39, 0xAD,
// Encrypted PIN is too long.
let new_pin_enc = vec![0x44; 65];
assert_eq!(decrypt_pin(&aes_dec_key, new_pin_enc), None,);
}
#[test]
fn test_check_and_store_new_pin() {
let mut rng = ThreadRng256 {};
let mut persistent_store = PersistentStore::new(&mut rng);
let shared_secret = [0x88; 32];
let aes_enc_key = crypto::aes256::EncryptionKey::new(&shared_secret);
let aes_dec_key = crypto::aes256::DecryptionKey::new(&aes_enc_key);
let test_cases = vec![
// Accept PIN "1234".
(vec![0x31, 0x32, 0x33, 0x34], Ok(())),
// Reject PIN "123" since it is too short.
(
vec![0x31, 0x32, 0x33],
Err(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION),
),
// Reject PIN "12'\0'4" (a zero byte at index 2).
(
vec![0x31, 0x32, 0x00, 0x34],
Err(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION),
),
// Reject PINs not ending in 0u8 padding.
(
vec![0x30; 64],
Err(Ctap2StatusCode::CTAP2_ERR_PIN_POLICY_VIOLATION),
),
];
assert!(!check_and_store_new_pin(
&mut persistent_store,
&aes_dec_key,
bad_pin_enc
));
for (pin, result) in test_cases {
let old_pin_hash = persistent_store.pin_hash().cloned();
let new_pin_enc = encrypt_pin(&shared_secret, pin);
assert_eq!(
check_and_store_new_pin(&mut persistent_store, &aes_dec_key, new_pin_enc),
result
);
if result.is_ok() {
assert_ne!(old_pin_hash.as_ref(), persistent_store.pin_hash());
} else {
assert_eq!(old_pin_hash.as_ref(), persistent_store.pin_hash());
}
}
}
#[test]