exec-server: add Noise channel foundation

MODULE.bazel

@@ -210,6 +210,18 @@ crate.from_cargo(
     use_experimental_platforms = True,
 )
 
+# BLAKE3 normally builds hand-written assembly on x86_64. In the Windows GNU
+# cross configuration, that archive is produced by the build script but is not
+# propagated to the Rust link action. Prefer BLAKE3's equivalent Rust
+# intrinsics implementation for the affected targets so every Rust crate that
+# transitively uses BLAKE3 remains buildable under Windows linting.
+crate.annotation(
+    crate = "blake3",
+    crate_features_select = {
+        "x86_64-pc-windows-gnullvm": ["prefer_intrinsics"],
+    },
+)
+
 bazel_dep(name = "zstd", version = "1.5.7")
 
 crate.annotation(

codex-rs/Cargo.toml

@@ -265,6 +265,7 @@ async-stream = "0.3.6"
 async-trait = "0.1.89"
 aws-config = "1"
 aws-credential-types = "1"
+aws-lc-rs = { version = "=1.16.2", default-features = false, features = ["non-fips"] }
 aws-sigv4 = "1"
 aws-types = "1"
 axum = { version = "0.8", default-features = false }
@@ -275,6 +276,13 @@ chardetng = "0.1.17"
 chrono = "0.4.43"
 clap = "4"
 clap_complete = "4"
+clatter = { version = "2.2.0", default-features = false, features = [
+    "alloc",
+    "getrandom",
+    "use-25519",
+    "use-aes-gcm",
+    "use-sha",
+] }
 color-eyre = "0.6.3"
 constant_time_eq = "0.3.1"
 crossbeam-channel = "0.5.15"

codex-rs/exec-server/Cargo.toml

@@ -13,9 +13,11 @@ workspace = true
 [dependencies]
 arc-swap = { workspace = true }
 async-trait = { workspace = true }
+aws-lc-rs = { workspace = true }
 axum = { workspace = true, features = ["http1", "tokio", "ws"] }
 base64 = { workspace = true }
 bytes = { workspace = true }
+clatter = { workspace = true }
 codex-app-server-protocol = { workspace = true }
 codex-api = { workspace = true }
 codex-client = { workspace = true }

codex-rs/exec-server/src/aws_lc_ml_kem.rs

@@ -0,0 +1,89 @@
+//! Clatter's ML-KEM-768 adapter, backed by AWS-LC.
+
+use aws_lc_rs::kem::Ciphertext;
+use aws_lc_rs::kem::DecapsulationKey;
+use aws_lc_rs::kem::EncapsulationKey;
+use aws_lc_rs::kem::ML_KEM_768;
+use clatter::KeyPair;
+use clatter::bytearray::ByteArray;
+use clatter::bytearray::HeapArray;
+use clatter::bytearray::SensitiveByteArray;
+use clatter::error::KemError;
+use clatter::error::KemResult;
+use clatter::traits::CryptoComponent;
+use clatter::traits::Kem;
+use clatter::traits::Rng;
+
+pub(super) const PUBLIC_KEY_LEN: usize = 1184;
+const SECRET_KEY_LEN: usize = 2400;
+const CIPHERTEXT_LEN: usize = 1088;
+const SHARED_SECRET_LEN: usize = 32;
+
+/// ML-KEM-768 implementation backed by AWS-LC through `aws-lc-rs`.
+#[derive(Clone)]
+pub(super) struct AwsLcMlKem768;
+
+impl CryptoComponent for AwsLcMlKem768 {
+    fn name() -> &'static str {
+        "MLKEM768"
+    }
+}
+
+impl Kem for AwsLcMlKem768 {
+    type SecretKey = SensitiveByteArray<HeapArray<SECRET_KEY_LEN>>;
+    type PubKey = HeapArray<PUBLIC_KEY_LEN>;
+    type Ct = HeapArray<CIPHERTEXT_LEN>;
+    type Ss = SensitiveByteArray<[u8; SHARED_SECRET_LEN]>;
+
+    fn genkey_rng<R: Rng>(_rng: &mut R) -> KemResult<KeyPair<Self::PubKey, Self::SecretKey>> {
+        // AWS-LC generates ML-KEM keys with its own RNG. Clatter's RNG is unused.
+        let decapsulation_key =
+            DecapsulationKey::generate(&ML_KEM_768).map_err(|_| KemError::KeyGeneration)?;
+        let encapsulation_key = decapsulation_key
+            .encapsulation_key()
+            .map_err(|_| KemError::KeyGeneration)?;
+        let public = encapsulation_key
+            .key_bytes()
+            .map_err(|_| KemError::KeyGeneration)?;
+        let secret = decapsulation_key
+            .key_bytes()
+            .map_err(|_| KemError::KeyGeneration)?;
+
+        Ok(KeyPair {
+            public: Self::PubKey::from_slice(public.as_ref()),
+            secret: Self::SecretKey::from_slice(secret.as_ref()),
+        })
+    }
+
+    fn encapsulate<R: Rng>(pk: &[u8], _rng: &mut R) -> KemResult<(Self::Ct, Self::Ss)> {
+        let encapsulation_key =
+            EncapsulationKey::new(&ML_KEM_768, pk).map_err(|_| KemError::Input)?;
+        let (ciphertext, shared_secret) = encapsulation_key
+            .encapsulate()
+            .map_err(|_| KemError::Encapsulation)?;
+
+        Ok((
+            Self::Ct::from_slice(ciphertext.as_ref()),
+            Self::Ss::from_slice(shared_secret.as_ref()),
+        ))
+    }
+
+    fn decapsulate(ct: &[u8], sk: &[u8]) -> KemResult<Self::Ss> {
+        // Check the wire length before constructing AWS-LC's ciphertext wrapper.
+        if ct.len() != CIPHERTEXT_LEN {
+            return Err(KemError::Input);
+        }
+
+        let decapsulation_key =
+            DecapsulationKey::new(&ML_KEM_768, sk).map_err(|_| KemError::Input)?;
+        let shared_secret = decapsulation_key
+            .decapsulate(Ciphertext::from(ct))
+            .map_err(|_| KemError::Decapsulation)?;
+
+        Ok(Self::Ss::from_slice(shared_secret.as_ref()))
+    }
+}
+
+#[cfg(test)]
+#[path = "aws_lc_ml_kem_tests.rs"]
+mod tests;

codex-rs/exec-server/src/aws_lc_ml_kem_tests.rs

@@ -0,0 +1,31 @@
+use clatter::bytearray::ByteArray;
+use clatter::traits::Kem;
+use pretty_assertions::assert_eq;
+
+use super::AwsLcMlKem768;
+
+#[test]
+fn kem_roundtrip() {
+    let keypair = AwsLcMlKem768::genkey().expect("generate keypair");
+    let mut rng = clatter::crypto::rng::DefaultRng;
+    let (ciphertext, encapsulated_secret) =
+        AwsLcMlKem768::encapsulate(keypair.public.as_slice(), &mut rng).expect("encapsulate");
+    let decapsulated_secret =
+        AwsLcMlKem768::decapsulate(ciphertext.as_slice(), keypair.secret.as_slice())
+            .expect("decapsulate");
+
+    assert_eq!(
+        encapsulated_secret.as_slice(),
+        decapsulated_secret.as_slice()
+    );
+}
+
+#[test]
+fn decapsulate_rejects_wrong_ciphertext_length() {
+    let keypair = AwsLcMlKem768::genkey().expect("generate keypair");
+
+    let error = AwsLcMlKem768::decapsulate(&[], keypair.secret.as_slice())
+        .expect_err("empty ciphertext should be rejected");
+
+    assert!(matches!(error, clatter::error::KemError::Input));
+}

codex-rs/exec-server/src/lib.rs

@@ -1,3 +1,4 @@
+mod aws_lc_ml_kem;
 mod client;
 mod client_api;
 mod client_transport;
@@ -11,6 +12,7 @@ mod fs_helper_main;
 mod fs_sandbox;
 mod local_file_system;
 mod local_process;
+mod noise_channel;
 mod process;
 mod process_id;
 mod protocol;
@@ -51,6 +53,9 @@ pub use fs_helper::CODEX_FS_HELPER_ARG1;
 pub use fs_helper_main::main as run_fs_helper_main;
 pub use local_file_system::LOCAL_FS;
 pub use local_file_system::LocalFileSystem;
+pub use noise_channel::NoiseChannelError;
+pub use noise_channel::NoiseChannelIdentity;
+pub use noise_channel::NoiseChannelPublicKey;
 pub use process::ExecBackend;
 pub use process::ExecProcess;
 pub use process::ExecProcessEvent;