feat: pluggable SignalCryptoProvider for AES-CBC/GCM + HMAC-SHA256

wacore/Cargo.toml

@@ -18,7 +18,6 @@ js = ["getrandom/wasm_js"]
 
 [dependencies]
 aes = { workspace = true }
-aes-gcm = { workspace = true }
 anyhow = { workspace = true }
 async-channel = { workspace = true }
 async-lock = { workspace = true }
@@ -55,6 +54,7 @@ wacore-noise = { workspace = true }
 waproto = { workspace = true }
 
 [dev-dependencies]
+aes-gcm = { workspace = true }
 futures = { workspace = true, features = ["executor"] }
 iai-callgrind = { workspace = true }
 tokio = { workspace = true, features = ["macros", "rt"] }

wacore/libsignal/Cargo.toml

@@ -9,7 +9,6 @@ description = "Signal Protocol implementation for the WhatsApp platform"
 
 [dependencies]
 aes = { workspace = true }
-aes-gcm = { workspace = true }
 arrayref = "0.3.9"
 async-trait = { workspace = true }
 cbc = { version = "0.2", features = ["alloc"] }

wacore/libsignal/src/crypto/aes_cbc.rs

@@ -5,9 +5,7 @@
 
 use std::result::Result;
 
-use aes::Aes256;
-use aes::cipher::block_padding::Pkcs7;
-use aes::cipher::{BlockModeDecrypt, BlockModeEncrypt, KeyIvInit};
+use crate::crypto::provider::provider;
 
 #[derive(Debug, displaydoc::Display, thiserror::Error)]
 pub enum EncryptionError {
@@ -31,35 +29,11 @@ pub fn aes_256_cbc_encrypt_into(
     iv: &[u8],
     output: &mut Vec<u8>,
 ) -> Result<(), EncryptionError> {
-    // Calculate the space needed for encryption + PKCS7 padding
-    // PKCS7 padding can add 1-16 bytes (always adds at least 1 byte)
-    let padding_needed = 16 - (ptext.len() % 16);
-    let encrypted_size = ptext.len() + padding_needed;
-
-    let start_pos = output.len();
-
-    // Reserve space for the encrypted data
-    output.resize(start_pos + encrypted_size, 0);
-
-    // Copy plaintext to the buffer
-    output[start_pos..start_pos + ptext.len()].copy_from_slice(ptext);
-
-    // Create encryptor and encrypt in place
-    let encryptor = cbc::Encryptor::<Aes256>::new_from_slices(key, iv)
-        .map_err(|_| EncryptionError::BadKeyOrIv)?;
-
-    // Encrypt the data in place with proper padding
-    let encrypted_len = {
-        let encrypted_slice = encryptor
-            .encrypt_padded::<Pkcs7>(&mut output[start_pos..], ptext.len())
-            .map_err(|_| EncryptionError::BadPadding)?;
-        encrypted_slice.len()
-    };
-
-    // Resize to actual encrypted length
-    output.truncate(start_pos + encrypted_len);
-
-    Ok(())
+    let key: &[u8; 32] = key.try_into().map_err(|_| EncryptionError::BadKeyOrIv)?;
+    let iv: &[u8; 16] = iv.try_into().map_err(|_| EncryptionError::BadKeyOrIv)?;
+    provider()
+        .aes_256_cbc_encrypt(key, iv, ptext, output)
+        .map_err(|_| EncryptionError::BadPadding)
 }
 
 /// The output buffer is cleared and filled with the decrypted plaintext.
@@ -69,27 +43,11 @@ pub fn aes_256_cbc_decrypt_into(
     iv: &[u8],
     output: &mut Vec<u8>,
 ) -> Result<(), DecryptionError> {
-    if ctext.is_empty() || !ctext.len().is_multiple_of(16) {
-        return Err(DecryptionError::BadCiphertext(
-            "ciphertext length must be a non-zero multiple of 16",
-        ));
-    }
-
-    output.clear();
-    output.reserve(ctext.len());
-    output.extend_from_slice(ctext);
-
-    let decryptor = cbc::Decryptor::<Aes256>::new_from_slices(key, iv)
-        .map_err(|_| DecryptionError::BadKeyOrIv)?;
-
-    let decrypted = decryptor
-        .decrypt_padded::<Pkcs7>(output)
-        .map_err(|_| DecryptionError::BadCiphertext("failed to decrypt"))?;
-
-    let decrypted_len = decrypted.len();
-    output.truncate(decrypted_len);
-
-    Ok(())
+    let key: &[u8; 32] = key.try_into().map_err(|_| DecryptionError::BadKeyOrIv)?;
+    let iv: &[u8; 16] = iv.try_into().map_err(|_| DecryptionError::BadKeyOrIv)?;
+    provider()
+        .aes_256_cbc_decrypt(key, iv, ctext, output)
+        .map_err(|_| DecryptionError::BadCiphertext("failed to decrypt"))
 }
 
 #[cfg(test)]

wacore/libsignal/src/crypto/mod.rs

@@ -8,7 +8,8 @@ mod hash;
 
 mod aes_cbc;
 mod aes_ctr;
-mod aes_gcm;
+pub(crate) mod aes_gcm;
+mod provider;
 
 pub use aes_cbc::{
     DecryptionError, EncryptionError, aes_256_cbc_decrypt_into, aes_256_cbc_encrypt_into,
@@ -19,3 +20,38 @@ pub use error::{Error, Result};
 pub use hash::{
     CryptographicHash, CryptographicMac, SHA1_OUTPUT_SIZE, SHA256_OUTPUT_SIZE, SHA512_OUTPUT_SIZE,
 };
+pub use provider::{
+    CryptoProviderError, RustCryptoProvider, SignalCryptoProvider, set_crypto_provider,
+};
+
+/// AES-256-GCM seal. Appends `ciphertext || tag(16)` to `out`.
+/// Delegates to the active [`SignalCryptoProvider`].
+#[inline]
+pub fn aes_256_gcm_encrypt(
+    key: &[u8; 32],
+    nonce: &[u8; 12],
+    aad: &[u8],
+    plaintext: &[u8],
+    out: &mut Vec<u8>,
+) -> std::result::Result<(), CryptoProviderError> {
+    provider::provider().aes_256_gcm_encrypt(key, nonce, aad, plaintext, out)
+}
+
+/// AES-256-GCM open. `ciphertext_with_tag` must end with the 16-byte tag.
+/// Appends plaintext to `out` on success.
+#[inline]
+pub fn aes_256_gcm_decrypt(
+    key: &[u8; 32],
+    nonce: &[u8; 12],
+    aad: &[u8],
+    ciphertext_with_tag: &[u8],
+    out: &mut Vec<u8>,
+) -> std::result::Result<(), CryptoProviderError> {
+    provider::provider().aes_256_gcm_decrypt(key, nonce, aad, ciphertext_with_tag, out)
+}
+
+/// HMAC-SHA256 one-shot. Delegates to the active [`SignalCryptoProvider`].
+#[inline]
+pub fn hmac_sha256(key: &[u8], input: &[u8]) -> [u8; 32] {
+    provider::provider().hmac_sha256(key, input)
+}