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[PM-17984] Remove AES128-CBC+HMAC encryption #147

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Merged
merged 5 commits into from
Feb 6, 2025
Merged

[PM-17984] Remove AES128-CBC+HMAC encryption #147

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13fb037
Remove AES128CBC-HMAC encryption
quexten Feb 6, 2025
0eb8e53
Merge branch 'main' into km/pm-17984/remove-cbc128hmac
quexten Feb 6, 2025
81b8dcc
Remove forgotten parameter
quexten Feb 6, 2025
5491a2f
Merge branch 'km/pm-17984/remove-cbc128hmac' of github.com:bitwarden/…
quexten Feb 6, 2025
00f12e2
Add comment about removal of AesCbc128_HmacSha256
quexten Feb 6, 2025
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53 changes: 1 addition & 52 deletions crates/bitwarden-crypto/src/aes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,9 +6,7 @@
//! [KeyEncryptable][crate::KeyEncryptable] & [KeyDecryptable][crate::KeyDecryptable] instead.

use aes::cipher::{
block_padding::Pkcs7,
typenum::{U16, U32},
BlockDecryptMut, BlockEncryptMut, KeyIvInit,
block_padding::Pkcs7, typenum::U32, BlockDecryptMut, BlockEncryptMut, KeyIvInit,
};
use generic_array::GenericArray;
use hmac::Mac;
Expand Down Expand Up @@ -111,42 +109,6 @@ fn encrypt_aes256_internal(
(iv, data)
}

/// Decrypt using AES-128 in CBC mode.
///
/// Behaves similar to [decrypt_aes128_hmac], but does not validate the MAC.
fn decrypt_aes128(iv: &[u8; 16], data: Vec<u8>, key: &GenericArray<u8, U16>) -> Result<Vec<u8>> {
// Decrypt data
let iv = GenericArray::from_slice(iv);
let mut data = data;
let decrypted_key_slice = cbc::Decryptor::<aes::Aes128>::new(key, iv)
.decrypt_padded_mut::<Pkcs7>(&mut data)
.map_err(|_| CryptoError::KeyDecrypt)?;

// Data is decrypted in place and returns a subslice of the original Vec, to avoid cloning it,
// we truncate to the subslice length
let decrypted_len = decrypted_key_slice.len();
data.truncate(decrypted_len);

Ok(data)
}

/// Decrypt using AES-128 in CBC mode with MAC.
///
/// Behaves similar to [decrypt_aes128], but also validates the MAC.
pub(crate) fn decrypt_aes128_hmac(
iv: &[u8; 16],
mac: &[u8; 32],
data: Vec<u8>,
mac_key: &GenericArray<u8, U16>,
key: &GenericArray<u8, U16>,
) -> Result<Vec<u8>> {
let res = generate_mac(mac_key, iv, &data)?;
if res.ct_ne(mac).into() {
return Err(CryptoError::InvalidMac);
}
decrypt_aes128(iv, data, key)
}

/// Generate a MAC using HMAC-SHA256.
fn generate_mac(mac_key: &[u8], iv: &[u8], data: &[u8]) -> Result<[u8; 32]> {
let mut hmac =
Expand Down Expand Up @@ -212,19 +174,6 @@ mod tests {
assert_eq!(mac.len(), 32);
}

#[test]
fn test_decrypt_aes128() {
let iv = generate_vec(16, 0, 1);
let iv: &[u8; 16] = iv.as_slice().try_into().unwrap();
let key = generate_generic_array(0, 1);

let data = STANDARD.decode("dC0X+2IjFbeL4WLLg2jX7Q==").unwrap();

let decrypted = decrypt_aes128(iv, data, &key).unwrap();

assert_eq!(String::from_utf8(decrypted).unwrap(), "EncryptMe!");
}

#[test]
fn test_decrypt_aes256() {
let iv = generate_vec(16, 0, 1);
Expand Down
79 changes: 6 additions & 73 deletions crates/bitwarden-crypto/src/enc_string/symmetric.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,6 @@ export type EncString = string;
///
/// ## Variants
/// - [AesCbc256_B64](EncString::AesCbc256_B64)
/// - [AesCbc128_HmacSha256_B64](EncString::AesCbc128_HmacSha256_B64)
/// - [AesCbc256_HmacSha256_B64](EncString::AesCbc256_HmacSha256_B64)
///
/// ## Serialization
Expand All @@ -55,12 +54,7 @@ export type EncString = string;
pub enum EncString {
/// 0
AesCbc256_B64 { iv: [u8; 16], data: Vec<u8> },
/// 1
AesCbc128_HmacSha256_B64 {
iv: [u8; 16],
mac: [u8; 32],
data: Vec<u8>,
},
/// 1 was the now removed `AesCbc128_HmacSha256_B64`.
/// 2
AesCbc256_HmacSha256_B64 {
iv: [u8; 16],
Expand Down Expand Up @@ -89,16 +83,12 @@ impl FromStr for EncString {

Ok(EncString::AesCbc256_B64 { iv, data })
}
("1" | "2", 3) => {
("2", 3) => {
let iv = from_b64(parts[0])?;
let data = from_b64_vec(parts[1])?;
let mac = from_b64(parts[2])?;

if enc_type == "1" {
Ok(EncString::AesCbc128_HmacSha256_B64 { iv, mac, data })
} else {
Ok(EncString::AesCbc256_HmacSha256_B64 { iv, mac, data })
}
Ok(EncString::AesCbc256_HmacSha256_B64 { iv, mac, data })
}

(enc_type, parts) => Err(EncStringParseError::InvalidTypeSymm {
Expand Down Expand Up @@ -130,17 +120,13 @@ impl EncString {

Ok(EncString::AesCbc256_B64 { iv, data })
}
1 | 2 => {
2 => {
check_length(buf, 50)?;
let iv = buf[1..17].try_into().expect("Valid length");
let mac = buf[17..49].try_into().expect("Valid length");
let data = buf[49..].to_vec();

if enc_type == 1 {
Ok(EncString::AesCbc128_HmacSha256_B64 { iv, mac, data })
} else {
Ok(EncString::AesCbc256_HmacSha256_B64 { iv, mac, data })
}
Ok(EncString::AesCbc256_HmacSha256_B64 { iv, mac, data })
}
_ => Err(EncStringParseError::InvalidTypeSymm {
enc_type: enc_type.to_string(),
Expand All @@ -160,8 +146,7 @@ impl EncString {
buf.extend_from_slice(iv);
buf.extend_from_slice(data);
}
EncString::AesCbc128_HmacSha256_B64 { iv, mac, data }
| EncString::AesCbc256_HmacSha256_B64 { iv, mac, data } => {
EncString::AesCbc256_HmacSha256_B64 { iv, mac, data } => {
buf = Vec::with_capacity(1 + 16 + 32 + data.len());
buf.push(self.enc_type());
buf.extend_from_slice(iv);
Expand All @@ -178,7 +163,6 @@ impl Display for EncString {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
let parts: Vec<&[u8]> = match self {
EncString::AesCbc256_B64 { iv, data } => vec![iv, data],
EncString::AesCbc128_HmacSha256_B64 { iv, mac, data } => vec![iv, data, mac],
EncString::AesCbc256_HmacSha256_B64 { iv, mac, data } => vec![iv, data, mac],
};

Expand Down Expand Up @@ -222,7 +206,6 @@ impl EncString {
const fn enc_type(&self) -> u8 {
match self {
EncString::AesCbc256_B64 { .. } => 0,
EncString::AesCbc128_HmacSha256_B64 { .. } => 1,
EncString::AesCbc256_HmacSha256_B64 { .. } => 2,
}
}
Expand Down Expand Up @@ -250,16 +233,6 @@ impl KeyDecryptable<SymmetricCryptoKey, Vec<u8>> for EncString {
let dec = crate::aes::decrypt_aes256(iv, data.clone(), &key.key)?;
Ok(dec)
}
EncString::AesCbc128_HmacSha256_B64 { iv, mac, data } => {
// TODO: SymmetricCryptoKey is designed to handle 32 byte keys only, but this
// variant uses a 16 byte key This means the key+mac are going to be
// parsed as a single 32 byte key, at the moment we split it manually
// When refactoring the key handling, this should be fixed.
let enc_key = key.key[0..16].into();
let mac_key = key.key[16..32].into();
let dec = crate::aes::decrypt_aes128_hmac(iv, mac, data.clone(), mac_key, enc_key)?;
Ok(dec)
}
EncString::AesCbc256_HmacSha256_B64 { iv, mac, data } => {
let mac_key = key.mac_key.as_ref().ok_or(CryptoError::InvalidMac)?;
let dec =
Expand Down Expand Up @@ -390,33 +363,6 @@ mod tests {
};
}

#[test]
fn test_from_str_cbc128_hmac() {
let enc_str = "1.Hh8gISIjJCUmJygpKissLQ==|MjM0NTY3ODk6Ozw9Pj9AQUJDREU=|KCkqKywtLi8wMTIzNDU2Nzg5Ojs8PT4/QEFCQ0RFRkc=";
let enc_string: EncString = enc_str.parse().unwrap();

assert_eq!(enc_string.enc_type(), 1);
if let EncString::AesCbc128_HmacSha256_B64 { iv, mac, data } = &enc_string {
assert_eq!(
iv,
&[30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45]
);
assert_eq!(
mac,
&[
40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59,
60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71
]
);
assert_eq!(
data,
&[50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69]
);
} else {
panic!("Invalid variant")
};
}

#[test]
fn test_decrypt_cbc256() {
let key = "hvBMMb1t79YssFZkpetYsM3deyVuQv4r88Uj9gvYe08=".to_string();
Expand Down Expand Up @@ -448,19 +394,6 @@ mod tests {
assert!(matches!(result, Err(CryptoError::MacNotProvided)));
}

#[test]
fn test_decrypt_cbc128_hmac() {
let key = "Gt1aZ8kTTgkF80bLtb7LiMZBcxEA2FA5mbvV4x7K208=".to_string();
let key = SymmetricCryptoKey::try_from(key).unwrap();

let enc_str = "1.CU/oG4VZuxbHoZSDZjCLQw==|kb1HGwAk+fQ275ORfLf5Ew==|8UaEYHyqRZcG37JWhYBOBdEatEXd1u1/wN7OuImolcM=";
let enc_string: EncString = enc_str.parse().unwrap();
assert_eq!(enc_string.enc_type(), 1);

let dec_str: String = enc_string.decrypt_with_key(&key).unwrap();
assert_eq!(dec_str, "EncryptMe!");
}

#[test]
fn test_from_str_invalid() {
let enc_str = "7.ABC";
Expand Down
10 changes: 0 additions & 10 deletions crates/bitwarden-crypto/src/store/context.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -381,16 +381,6 @@ impl<Ids: KeyIds> KeyStoreContext<'_, Ids> {
let dec = crate::aes::decrypt_aes256(iv, data.clone(), &key.key)?;
Ok(dec)
}
EncString::AesCbc128_HmacSha256_B64 { iv, mac, data } => {
// TODO: SymmetricCryptoKey is designed to handle 32 byte keys only, but this
// variant uses a 16 byte key This means the key+mac are going to be
// parsed as a single 32 byte key, at the moment we split it manually
// When refactoring the key handling, this should be fixed.
let enc_key = (&key.key[0..16]).into();
let mac_key = (&key.key[16..32]).into();
let dec = crate::aes::decrypt_aes128_hmac(iv, mac, data.clone(), mac_key, enc_key)?;
Ok(dec)
}
EncString::AesCbc256_HmacSha256_B64 { iv, mac, data } => {
let mac_key = key.mac_key.as_ref().ok_or(CryptoError::InvalidMac)?;
let dec =
Expand Down
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