E2EE: allow setting key_ring_size and key_derivation_algorithm (#921)

* Allow setting keyring-size from Rust

* Implement using HKDF as the KDF.

* Reexport KeyDerivationAlgorithm, use const for default KeyDerivationAlgorithm.

* Update webrtc

* Add changeset

* Don't wrongly to m144 change, update webrtc to webrtc-24f6822-2

Author: onestacked

.changeset/e2ee_allow_setting_key_ring_size_and_key_derivation_algorithm_update_webrtc_to_m144.md

@@ -0,0 +1,23 @@
+---
+soxr-sys: patch
+webrtc-sys: patch
+livekit-ffi: minor
+livekit-protocol: patch
+livekit: minor
+livekit-wakeword: patch
+livekit-api: patch
+imgproc: patch
+libwebrtc: minor
+webrtc-sys-build: patch
+yuv-sys: patch
+---
+
+# E2EE: allow setting key_ring_size and key_derivation_algorithm, update webrtc to m144
+
+#921 by @onestacked
+
+This PR uses [this webrtc-sdk PR](https://github.com/webrtc-sdk/webrtc/pull/224) to configure the KDF.
+
+I've tested this with https://codeberg.org/esoteric_programmer/matrix-jukebox and it is compatible with Element Call.
+
+Fixed: https://github.com/livekit/rust-sdks/issues/796

libwebrtc/src/native/frame_cryptor.rs

@@ -25,12 +25,29 @@ use crate::{
 
 pub type OnStateChange = Box<dyn FnMut(String, EncryptionState) + Send + Sync>;
 
+#[derive(Copy, Clone, Debug)]
+#[non_exhaustive]
+pub enum KeyDerivationAlgorithm {
+    PBKDF2,
+    HKDF,
+}
+impl Into<sys_fc::ffi::KeyDerivationAlgorithm> for KeyDerivationAlgorithm {
+    fn into(self) -> sys_fc::ffi::KeyDerivationAlgorithm {
+        match self {
+            KeyDerivationAlgorithm::PBKDF2 => sys_fc::ffi::KeyDerivationAlgorithm::PBKDF2,
+            KeyDerivationAlgorithm::HKDF => sys_fc::ffi::KeyDerivationAlgorithm::HKDF,
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct KeyProviderOptions {
     pub shared_key: bool,
     pub ratchet_window_size: i32,
     pub ratchet_salt: Vec<u8>,
     pub failure_tolerance: i32,
+    pub key_ring_size: i32,
+    pub key_derivation_algorithm: KeyDerivationAlgorithm,
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -272,6 +289,8 @@ impl From<KeyProviderOptions> for sys_fc::ffi::KeyProviderOptions {
             ratchet_window_size: value.ratchet_window_size,
             ratchet_salt: value.ratchet_salt,
             failure_tolerance: value.failure_tolerance,
+            key_ring_size: value.key_ring_size,
+            key_derivation_algorithm: value.key_derivation_algorithm.into(),
         }
     }
 }

livekit-ffi/protocol/e2ee.proto

@@ -38,6 +38,13 @@ message KeyProviderOptions {
     required int32 ratchet_window_size = 2;
     required bytes ratchet_salt = 3;
     required int32 failure_tolerance = 4; // -1 = no tolerance
+    required int32 key_ring_size = 5; 
+    required KeyDerivationFunction key_derivation_function = 6;
+}
+
+enum KeyDerivationFunction {
+    PBKDF2 = 0;
+    HKDF = 1;
 }
 
 message E2eeOptions {

livekit-ffi/src/conversion/room.rs

@@ -21,7 +21,7 @@ use livekit::{
     options::{AudioEncoding, TrackPublishOptions, VideoEncoding},
     prelude::*,
     webrtc::{
-        native::frame_cryptor::EncryptionState,
+        native::frame_cryptor::{EncryptionState, KeyDerivationAlgorithm},
         prelude::{ContinualGatheringPolicy, IceServer, IceTransportsType, RtcConfiguration},
     },
     RoomInfo,
@@ -133,10 +133,22 @@ impl From<proto::DisconnectReason> for DisconnectReason {
 
 impl From<proto::KeyProviderOptions> for KeyProviderOptions {
     fn from(value: proto::KeyProviderOptions) -> Self {
+        let key_derivation_algorithm = value.key_derivation_function().into();
         Self {
             ratchet_window_size: value.ratchet_window_size,
             ratchet_salt: value.ratchet_salt,
             failure_tolerance: value.failure_tolerance,
+            key_ring_size: value.key_ring_size,
+            key_derivation_algorithm,
+        }
+    }
+}
+
+impl From<proto::KeyDerivationFunction> for KeyDerivationAlgorithm {
+    fn from(value: proto::KeyDerivationFunction) -> Self {
+        match value {
+            proto::KeyDerivationFunction::Pbkdf2 => KeyDerivationAlgorithm::PBKDF2,
+            proto::KeyDerivationFunction::Hkdf => KeyDerivationAlgorithm::HKDF,
         }
     }
 }

livekit/src/room/e2ee/key_provider.rs

@@ -20,15 +20,21 @@ use std::sync::{
 
 use crate::id::ParticipantIdentity;
 
+pub use libwebrtc::native::frame_cryptor::KeyDerivationAlgorithm;
+
 const DEFAULT_RATCHET_SALT: &str = "LKFrameEncryptionKey";
 const DEFAULT_RATCHET_WINDOW_SIZE: i32 = 16;
 const DEFAULT_FAILURE_TOLERANCE: i32 = -1; // no tolerance by default
+const DEFAULT_KEY_RING_SIZE: i32 = 16;
+const DEFAULT_KEY_DERIVATION_ALGORITHM: KeyDerivationAlgorithm = KeyDerivationAlgorithm::PBKDF2;
 
 #[derive(Clone)]
 pub struct KeyProviderOptions {
     pub ratchet_window_size: i32,
     pub ratchet_salt: Vec<u8>,
     pub failure_tolerance: i32,
+    pub key_ring_size: i32,
+    pub key_derivation_algorithm: KeyDerivationAlgorithm,
 }
 
 impl Default for KeyProviderOptions {
@@ -37,6 +43,8 @@ impl Default for KeyProviderOptions {
             ratchet_window_size: DEFAULT_RATCHET_WINDOW_SIZE,
             ratchet_salt: DEFAULT_RATCHET_SALT.to_owned().into_bytes(),
             failure_tolerance: DEFAULT_FAILURE_TOLERANCE,
+            key_ring_size: DEFAULT_KEY_RING_SIZE,
+            key_derivation_algorithm: DEFAULT_KEY_DERIVATION_ALGORITHM,
         }
     }
 }
@@ -56,6 +64,8 @@ impl KeyProvider {
                 ratchet_window_size: options.ratchet_window_size,
                 ratchet_salt: options.ratchet_salt,
                 failure_tolerance: options.failure_tolerance,
+                key_ring_size: options.key_ring_size,
+                key_derivation_algorithm: options.key_derivation_algorithm,
             }),
             latest_key_index: Arc::new(AtomicI32::new(0)),
         }
@@ -67,6 +77,8 @@ impl KeyProvider {
             ratchet_window_size: options.ratchet_window_size,
             ratchet_salt: options.ratchet_salt,
             failure_tolerance: options.failure_tolerance,
+            key_ring_size: options.key_ring_size,
+            key_derivation_algorithm: options.key_derivation_algorithm,
         });
         handle.set_shared_key(0, shared_key);
         Self { handle, latest_key_index: Arc::new(AtomicI32::new(0)) }

webrtc-sys/libwebrtc/.gclient

@@ -1,7 +1,7 @@
 solutions = [
   {
     "name": 'src',
-    "url": 'https://github.com/webrtc-sdk/webrtc.git@m137_release',
+    "url": 'https://github.com/webrtc-sdk/webrtc.git@m137_release'',
     "custom_deps": {},
     "deps_file": "DEPS",
     "managed": False,

webrtc-sys/src/frame_cryptor.cpp

@@ -40,6 +40,19 @@ webrtc::FrameCryptorTransformer::Algorithm AlgorithmToFrameCryptorAlgorithm(
   }
 }
 
+webrtc::KeyDerivationAlgorithm
+KeyDerivationAlgorithmToFrameCryptorKeyDerivationAlgorithm(
+    KeyDerivationAlgorithm algorithm) {
+  switch (algorithm) {
+    case KeyDerivationAlgorithm::PBKDF2:
+      return webrtc::KeyDerivationAlgorithm::kPBKDF2;
+    case KeyDerivationAlgorithm::HKDF:
+      return webrtc::KeyDerivationAlgorithm::kHKDF;
+    default:
+      return webrtc::KeyDerivationAlgorithm::kPBKDF2;
+  }
+}
+
 KeyProvider::KeyProvider(KeyProviderOptions options) {
   webrtc::KeyProviderOptions rtc_options;
   rtc_options.shared_key = options.shared_key;
@@ -51,7 +64,10 @@ KeyProvider::KeyProvider(KeyProviderOptions options) {
   rtc_options.ratchet_salt = ratchet_salt;
   rtc_options.ratchet_window_size = options.ratchet_window_size;
   rtc_options.failure_tolerance = options.failure_tolerance;
-
+  rtc_options.key_ring_size = options.key_ring_size;
+  rtc_options.key_derivation_algorithm =
+      KeyDerivationAlgorithmToFrameCryptorKeyDerivationAlgorithm(
+          options.key_derivation_algorithm);
   impl_ =
       new rtc::RefCountedObject<webrtc::DefaultKeyProviderImpl>(rtc_options);
 }
@@ -154,10 +170,12 @@ int32_t FrameCryptor::key_index() const {
   return e2ee_transformer_->key_index();
 }
 
-DataPacketCryptor::DataPacketCryptor(webrtc::FrameCryptorTransformer::Algorithm algorithm,
-                 webrtc::scoped_refptr<webrtc::KeyProvider> key_provider)
+DataPacketCryptor::DataPacketCryptor(
+    webrtc::FrameCryptorTransformer::Algorithm algorithm,
+    webrtc::scoped_refptr<webrtc::KeyProvider> key_provider)
     : data_packet_cryptor_(
-          webrtc::make_ref_counted<webrtc::DataPacketCryptor>(algorithm, key_provider)) {}
+          webrtc::make_ref_counted<webrtc::DataPacketCryptor>(algorithm,
+                                                              key_provider)) {}
 
 EncryptedPacket DataPacketCryptor::encrypt_data_packet(
     const ::rust::String participant_id,
@@ -167,12 +185,12 @@ EncryptedPacket DataPacketCryptor::encrypt_data_packet(
   std::copy(data.begin(), data.end(), std::back_inserter(data_vec));
 
   auto result = data_packet_cryptor_->Encrypt(
-      std::string(participant_id.data(), participant_id.size()),
-      key_index,
+      std::string(participant_id.data(), participant_id.size()), key_index,
       data_vec);
 
   if (!result.ok()) {
-    throw std::runtime_error(std::string("Failed to encrypt data packet: ") + result.error().message());
+    throw std::runtime_error(std::string("Failed to encrypt data packet: ") +
+                             result.error().message());
   }
 
   auto& packet = result.value();
@@ -202,20 +220,23 @@ rust::Vec<::std::uint8_t> DataPacketCryptor::decrypt_data_packet(
   std::copy(encrypted_packet.iv.begin(), encrypted_packet.iv.end(),
             std::back_inserter(iv_vec));
 
-  auto native_encrypted_packet = webrtc::make_ref_counted<webrtc::EncryptedPacket>(
-      std::move(data_vec), std::move(iv_vec), encrypted_packet.key_index);
+  auto native_encrypted_packet =
+      webrtc::make_ref_counted<webrtc::EncryptedPacket>(
+          std::move(data_vec), std::move(iv_vec), encrypted_packet.key_index);
 
   auto result = data_packet_cryptor_->Decrypt(
       std::string(participant_id.data(), participant_id.size()),
       native_encrypted_packet);
 
   if (!result.ok()) {
-    throw std::runtime_error(std::string("Failed to decrypt data packet: ") + result.error().message());
+    throw std::runtime_error(std::string("Failed to decrypt data packet: ") +
+                             result.error().message());
   }
 
   rust::Vec<uint8_t> decrypted_data;
   auto& decrypted = result.value();
-  std::copy(decrypted.begin(), decrypted.end(), std::back_inserter(decrypted_data));
+  std::copy(decrypted.begin(), decrypted.end(),
+            std::back_inserter(decrypted_data));
   return decrypted_data;
 }
 

webrtc-sys/src/frame_cryptor.rs

@@ -25,6 +25,15 @@ pub mod ffi {
         pub ratchet_window_size: i32,
         pub ratchet_salt: Vec<u8>,
         pub failure_tolerance: i32,
+        pub key_ring_size: i32,
+        pub key_derivation_algorithm: KeyDerivationAlgorithm,
+    }
+
+    #[derive(Debug)]
+    #[repr(i32)]
+    pub enum KeyDerivationAlgorithm {
+        PBKDF2 = 0,
+        HKDF,
     }
 
     #[derive(Debug)]
@@ -249,6 +258,8 @@ mod tests {
             ratchet_window_size: 16,
             ratchet_salt: vec![],
             failure_tolerance: -1,
+            key_ring_size: 16,
+            key_derivation_algorithm: ffi::KeyDerivationAlgorithm::HKDF,
         };
 
         let key_provider = ffi::new_key_provider(options);