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Separate file crypto wrappers, starting with AES-CBC (#298)

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* refactor key wrapping with tests

* remove backwards compatiblity tests

* adds AES-CBC tests for IV and RNG
This commit is contained in:
kaczmarczyck
2021-03-31 16:41:20 +02:00
committed by GitHub
parent c596f785ff
commit e7797a5683
3 changed files with 157 additions and 91 deletions
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147
src/ctap/crypto_wrapper.rs Normal file
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@@ -0,0 +1,147 @@
// Copyright 2021 Google LLC
//
// 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.
use crate::ctap::status_code::Ctap2StatusCode;
use alloc::vec;
use alloc::vec::Vec;
use crypto::cbc::{cbc_decrypt, cbc_encrypt};
use crypto::rng256::Rng256;
/// Wraps the AES256-CBC encryption to match what we need in CTAP.
pub fn aes256_cbc_encrypt(
rng: &mut dyn Rng256,
aes_enc_key: &crypto::aes256::EncryptionKey,
plaintext: &[u8],
embeds_iv: bool,
) -> Result<Vec<u8>, Ctap2StatusCode> {
if plaintext.len() % 16 != 0 {
return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
}
let iv = if embeds_iv {
let random_bytes = rng.gen_uniform_u8x32();
*array_ref!(random_bytes, 0, 16)
} else {
[0u8; 16]
};
let mut blocks = Vec::with_capacity(plaintext.len() / 16);
// TODO(https://github.com/rust-lang/rust/issues/74985) Use array_chunks when stable.
for block in plaintext.chunks_exact(16) {
blocks.push(*array_ref!(block, 0, 16));
}
cbc_encrypt(aes_enc_key, iv, &mut blocks);
let mut ciphertext = if embeds_iv { iv.to_vec() } else { vec![] };
ciphertext.extend(blocks.iter().flatten());
Ok(ciphertext)
}
/// Wraps the AES256-CBC decryption to match what we need in CTAP.
pub fn aes256_cbc_decrypt(
aes_enc_key: &crypto::aes256::EncryptionKey,
ciphertext: &[u8],
embeds_iv: bool,
) -> Result<Vec<u8>, Ctap2StatusCode> {
if ciphertext.len() % 16 != 0 {
return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
}
let mut block_len = ciphertext.len() / 16;
// TODO(https://github.com/rust-lang/rust/issues/74985) Use array_chunks when stable.
let mut block_iter = ciphertext.chunks_exact(16);
let iv = if embeds_iv {
block_len -= 1;
let iv_block = block_iter
.next()
.ok_or(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER)?;
*array_ref!(iv_block, 0, 16)
} else {
[0u8; 16]
};
let mut blocks = Vec::with_capacity(block_len);
for block in block_iter {
blocks.push(*array_ref!(block, 0, 16));
}
let aes_dec_key = crypto::aes256::DecryptionKey::new(aes_enc_key);
cbc_decrypt(&aes_dec_key, iv, &mut blocks);
Ok(blocks.iter().flatten().cloned().collect::<Vec<u8>>())
}
#[cfg(test)]
mod test {
use super::*;
use crypto::rng256::ThreadRng256;
#[test]
fn test_encrypt_decrypt_with_iv() {
let mut rng = ThreadRng256 {};
let aes_enc_key = crypto::aes256::EncryptionKey::new(&[0xC2; 32]);
let plaintext = vec![0xAA; 64];
let ciphertext = aes256_cbc_encrypt(&mut rng, &aes_enc_key, &plaintext, true).unwrap();
let decrypted = aes256_cbc_decrypt(&aes_enc_key, &ciphertext, true).unwrap();
assert_eq!(decrypted, plaintext);
}
#[test]
fn test_encrypt_decrypt_without_iv() {
let mut rng = ThreadRng256 {};
let aes_enc_key = crypto::aes256::EncryptionKey::new(&[0xC2; 32]);
let plaintext = vec![0xAA; 64];
let ciphertext = aes256_cbc_encrypt(&mut rng, &aes_enc_key, &plaintext, false).unwrap();
let decrypted = aes256_cbc_decrypt(&aes_enc_key, &ciphertext, false).unwrap();
assert_eq!(decrypted, plaintext);
}
#[test]
fn test_correct_iv_usage() {
let mut rng = ThreadRng256 {};
let aes_enc_key = crypto::aes256::EncryptionKey::new(&[0xC2; 32]);
let plaintext = vec![0xAA; 64];
let mut ciphertext_no_iv =
aes256_cbc_encrypt(&mut rng, &aes_enc_key, &plaintext, false).unwrap();
let mut ciphertext_with_iv = vec![0u8; 16];
ciphertext_with_iv.append(&mut ciphertext_no_iv);
let decrypted = aes256_cbc_decrypt(&aes_enc_key, &ciphertext_with_iv, true).unwrap();
assert_eq!(decrypted, plaintext);
}
#[test]
fn test_iv_manipulation_property() {
let mut rng = ThreadRng256 {};
let aes_enc_key = crypto::aes256::EncryptionKey::new(&[0xC2; 32]);
let plaintext = vec![0xAA; 64];
let mut ciphertext = aes256_cbc_encrypt(&mut rng, &aes_enc_key, &plaintext, true).unwrap();
let mut expected_plaintext = plaintext;
for i in 0..16 {
ciphertext[i] ^= 0xBB;
expected_plaintext[i] ^= 0xBB;
}
let decrypted = aes256_cbc_decrypt(&aes_enc_key, &ciphertext, true).unwrap();
assert_eq!(decrypted, expected_plaintext);
}
#[test]
fn test_chaining() {
let mut rng = ThreadRng256 {};
let aes_enc_key = crypto::aes256::EncryptionKey::new(&[0xC2; 32]);
let plaintext = vec![0xAA; 64];
let ciphertext1 = aes256_cbc_encrypt(&mut rng, &aes_enc_key, &plaintext, true).unwrap();
let ciphertext2 = aes256_cbc_encrypt(&mut rng, &aes_enc_key, &plaintext, true).unwrap();
assert_eq!(ciphertext1.len(), 80);
assert_eq!(ciphertext2.len(), 80);
// The ciphertext should mutate in all blocks with a different IV.
let block_iter1 = ciphertext1.chunks_exact(16);
let block_iter2 = ciphertext2.chunks_exact(16);
for (block1, block2) in block_iter1.zip(block_iter2) {
assert_ne!(block1, block2);
}
}
}

43
src/ctap/mod.rs
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@@ -17,6 +17,7 @@ mod client_pin;
pub mod command;
mod config_command;
mod credential_management;
mod crypto_wrapper;
#[cfg(feature = "with_ctap1")]
mod ctap1;
mod customization;
@@ -38,6 +39,7 @@ use self::command::{
};
use self::config_command::process_config;
use self::credential_management::process_credential_management;
use self::crypto_wrapper::{aes256_cbc_decrypt, aes256_cbc_encrypt};
use self::customization::{
DEFAULT_CRED_PROTECT, ENTERPRISE_ATTESTATION_MODE, ENTERPRISE_RP_ID_LIST,
MAX_CREDENTIAL_COUNT_IN_LIST, MAX_CRED_BLOB_LENGTH, MAX_LARGE_BLOB_ARRAY_SIZE,
@@ -71,7 +73,6 @@ use cbor::cbor_map_options;
use core::convert::TryFrom;
#[cfg(feature = "debug_ctap")]
use core::fmt::Write;
use crypto::cbc::{cbc_decrypt, cbc_encrypt};
use crypto::hmac::{hmac_256, verify_hmac_256};
use crypto::rng256::Rng256;
use crypto::sha256::Sha256;
@@ -338,23 +339,11 @@ where
) -> Result<Vec<u8>, Ctap2StatusCode> {
let master_keys = self.persistent_store.master_keys()?;
let aes_enc_key = crypto::aes256::EncryptionKey::new(&master_keys.encryption);
let mut sk_bytes = [0; 32];
private_key.to_bytes(&mut sk_bytes);
let mut iv = [0; 16];
iv.copy_from_slice(&self.rng.gen_uniform_u8x32()[..16]);
let mut plaintext = [0; 64];
private_key.to_bytes(array_mut_ref!(plaintext, 0, 32));
plaintext[32..64].copy_from_slice(application);
let mut blocks = [[0u8; 16]; 4];
blocks[0].copy_from_slice(&sk_bytes[..16]);
blocks[1].copy_from_slice(&sk_bytes[16..]);
blocks[2].copy_from_slice(&application[..16]);
blocks[3].copy_from_slice(&application[16..]);
cbc_encrypt(&aes_enc_key, iv, &mut blocks);
let mut encrypted_id = Vec::with_capacity(0x70);
encrypted_id.extend(&iv);
for b in &blocks {
encrypted_id.extend(b);
}
let mut encrypted_id = aes256_cbc_encrypt(self.rng, &aes_enc_key, &plaintext, true)?;
let id_hmac = hmac_256::<Sha256>(&master_keys.hmac, &encrypted_id[..]);
encrypted_id.extend(&id_hmac);
Ok(encrypted_id)
@@ -381,26 +370,12 @@ where
return Ok(None);
}
let aes_enc_key = crypto::aes256::EncryptionKey::new(&master_keys.encryption);
let aes_dec_key = crypto::aes256::DecryptionKey::new(&aes_enc_key);
let mut iv = [0; 16];
iv.copy_from_slice(&credential_id[..16]);
let mut blocks = [[0u8; 16]; 4];
for i in 0..4 {
blocks[i].copy_from_slice(&credential_id[16 * (i + 1)..16 * (i + 2)]);
}
cbc_decrypt(&aes_dec_key, iv, &mut blocks);
let mut decrypted_sk = [0; 32];
let mut decrypted_rp_id_hash = [0; 32];
decrypted_sk[..16].clone_from_slice(&blocks[0]);
decrypted_sk[16..].clone_from_slice(&blocks[1]);
decrypted_rp_id_hash[..16].clone_from_slice(&blocks[2]);
decrypted_rp_id_hash[16..].clone_from_slice(&blocks[3]);
if rp_id_hash != decrypted_rp_id_hash {
let decrypted_id = aes256_cbc_decrypt(&aes_enc_key, &credential_id[..payload_size], true)?;
if rp_id_hash != &decrypted_id[32..64] {
return Ok(None);
}
let sk_option = crypto::ecdsa::SecKey::from_bytes(&decrypted_sk);
let sk_option = crypto::ecdsa::SecKey::from_bytes(array_ref!(decrypted_id, 0, 32));
Ok(sk_option.map(|sk| PublicKeyCredentialSource {
key_type: PublicKeyCredentialType::PublicKey,
credential_id,

58
src/ctap/pin_protocol.rs
View File

@@ -13,13 +13,12 @@
// limitations under the License.
use crate::ctap::client_pin::PIN_TOKEN_LENGTH;
use crate::ctap::crypto_wrapper::{aes256_cbc_decrypt, aes256_cbc_encrypt};
use crate::ctap::data_formats::{CoseKey, PinUvAuthProtocol};
use crate::ctap::status_code::Ctap2StatusCode;
use alloc::boxed::Box;
use alloc::vec;
use alloc::vec::Vec;
use core::convert::TryInto;
use crypto::cbc::{cbc_decrypt, cbc_encrypt};
use crypto::hkdf::hkdf_empty_salt_256;
#[cfg(test)]
use crypto::hmac::hmac_256;
@@ -135,61 +134,6 @@ pub trait SharedSecret {
fn authenticate(&self, message: &[u8]) -> Vec<u8>;
}
fn aes256_cbc_encrypt(
rng: &mut dyn Rng256,
aes_enc_key: &crypto::aes256::EncryptionKey,
plaintext: &[u8],
has_iv: bool,
) -> Result<Vec<u8>, Ctap2StatusCode> {
if plaintext.len() % 16 != 0 {
return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
}
let iv = if has_iv {
let random_bytes = rng.gen_uniform_u8x32();
*array_ref!(random_bytes, 0, 16)
} else {
[0u8; 16]
};
let mut blocks = Vec::with_capacity(plaintext.len() / 16);
// TODO(https://github.com/rust-lang/rust/issues/74985) Use array_chunks when stable.
for block in plaintext.chunks_exact(16) {
blocks.push(*array_ref!(block, 0, 16));
}
cbc_encrypt(aes_enc_key, iv, &mut blocks);
let mut ciphertext = if has_iv { iv.to_vec() } else { vec![] };
ciphertext.extend(blocks.iter().flatten());
Ok(ciphertext)
}
fn aes256_cbc_decrypt(
aes_enc_key: &crypto::aes256::EncryptionKey,
ciphertext: &[u8],
has_iv: bool,
) -> Result<Vec<u8>, Ctap2StatusCode> {
if ciphertext.len() % 16 != 0 {
return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);
}
let mut block_len = ciphertext.len() / 16;
// TODO(https://github.com/rust-lang/rust/issues/74985) Use array_chunks when stable.
let mut block_iter = ciphertext.chunks_exact(16);
let iv = if has_iv {
block_len -= 1;
let iv_block = block_iter
.next()
.ok_or(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER)?;
*array_ref!(iv_block, 0, 16)
} else {
[0u8; 16]
};
let mut blocks = Vec::with_capacity(block_len);
for block in block_iter {
blocks.push(*array_ref!(block, 0, 16));
}
let aes_dec_key = crypto::aes256::DecryptionKey::new(aes_enc_key);
cbc_decrypt(&aes_dec_key, iv, &mut blocks);
Ok(blocks.iter().flatten().cloned().collect::<Vec<u8>>())
}
fn verify_v1(key: &[u8], message: &[u8], signature: &[u8]) -> Result<(), Ctap2StatusCode> {
if signature.len() != 16 {
return Err(Ctap2StatusCode::CTAP1_ERR_INVALID_PARAMETER);