From 4732484520838081703fe61ef4bd8c4531637b85 Mon Sep 17 00:00:00 2001 From: Jeffrey Czyz Date: Thu, 24 Aug 2023 16:31:16 -0500 Subject: [PATCH] Add a ChaCha20 utility for encrypting a block This hides an encryption implementation detail from callers. --- lightning/src/ln/inbound_payment.rs | 14 ++++----- lightning/src/util/chacha20.rs | 44 +++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+), 8 deletions(-) diff --git a/lightning/src/ln/inbound_payment.rs b/lightning/src/ln/inbound_payment.rs index 956928fd7..25e79e3bc 100644 --- a/lightning/src/ln/inbound_payment.rs +++ b/lightning/src/ln/inbound_payment.rs @@ -277,10 +277,9 @@ fn construct_payment_secret(iv_bytes: &[u8; IV_LEN], metadata_bytes: &[u8; METAD let (iv_slice, encrypted_metadata_slice) = payment_secret_bytes.split_at_mut(IV_LEN); iv_slice.copy_from_slice(iv_bytes); - let chacha_block = ChaCha20::get_single_block(metadata_key, iv_bytes); - for i in 0..METADATA_LEN { - encrypted_metadata_slice[i] = chacha_block[i] ^ metadata_bytes[i]; - } + ChaCha20::encrypt_single_block( + metadata_key, iv_bytes, encrypted_metadata_slice, metadata_bytes + ); PaymentSecret(payment_secret_bytes) } @@ -412,11 +411,10 @@ fn decrypt_metadata(payment_secret: PaymentSecret, keys: &ExpandedKey) -> ([u8; let (iv_slice, encrypted_metadata_bytes) = payment_secret.0.split_at(IV_LEN); iv_bytes.copy_from_slice(iv_slice); - let chacha_block = ChaCha20::get_single_block(&keys.metadata_key, &iv_bytes); let mut metadata_bytes: [u8; METADATA_LEN] = [0; METADATA_LEN]; - for i in 0..METADATA_LEN { - metadata_bytes[i] = chacha_block[i] ^ encrypted_metadata_bytes[i]; - } + ChaCha20::encrypt_single_block( + &keys.metadata_key, &iv_bytes, &mut metadata_bytes, encrypted_metadata_bytes + ); (iv_bytes, metadata_bytes) } diff --git a/lightning/src/util/chacha20.rs b/lightning/src/util/chacha20.rs index c729e6847..07567ea8a 100644 --- a/lightning/src/util/chacha20.rs +++ b/lightning/src/util/chacha20.rs @@ -159,6 +159,20 @@ mod real_chacha { chacha_bytes } + /// Encrypts `src` into `dest` using a single block from a ChaCha stream. Passing `dest` as + /// `src` in a second call will decrypt it. + pub fn encrypt_single_block( + key: &[u8; 32], nonce: &[u8; 16], dest: &mut [u8], src: &[u8] + ) { + debug_assert_eq!(dest.len(), src.len()); + debug_assert!(dest.len() <= 32); + + let block = ChaCha20::get_single_block(key, nonce); + for i in 0..dest.len() { + dest[i] = block[i] ^ src[i]; + } + } + fn expand(key: &[u8], nonce: &[u8]) -> ChaChaState { let constant = match key.len() { 16 => b"expand 16-byte k", @@ -290,6 +304,13 @@ mod fuzzy_chacha { [0; 32] } + pub fn encrypt_single_block( + _key: &[u8; 32], _nonce: &[u8; 16], dest: &mut [u8], src: &[u8] + ) { + debug_assert_eq!(dest.len(), src.len()); + debug_assert!(dest.len() <= 32); + } + pub fn process(&mut self, input: &[u8], output: &mut [u8]) { output.copy_from_slice(input); } @@ -618,4 +639,27 @@ mod test { assert_eq!(ChaCha20::get_single_block(&key, &nonce_16bytes), block_bytes); } + + #[test] + fn encrypt_single_block() { + let key = [ + 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, + 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, + 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, + 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, + ]; + let nonce = [ + 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, + 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, + ]; + let bytes = [1; 32]; + + let mut encrypted_bytes = [0; 32]; + ChaCha20::encrypt_single_block(&key, &nonce, &mut encrypted_bytes, &bytes); + + let mut decrypted_bytes = [0; 32]; + ChaCha20::encrypt_single_block(&key, &nonce, &mut decrypted_bytes, &encrypted_bytes); + + assert_eq!(bytes, decrypted_bytes); + } } -- 2.39.5