Add canonical signed operation envelopes

crates/geth-crypto/Cargo.toml

@@ -12,6 +12,7 @@ hex.workspace = true
 rand_core.workspace = true
 serde.workspace = true
 thiserror.workspace = true
+geth-codec = { path = "../geth-codec" }
 geth-types = { path = "../geth-types" }
 
 [dev-dependencies]

crates/geth-crypto/src/lib.rs

@@ -1,5 +1,6 @@
 use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
 use rand_core::OsRng;
+use serde::Serialize;
 use std::path::Path;
 
 #[derive(Debug, thiserror::Error)]
@@ -12,6 +13,8 @@ pub enum CryptoError {
     InvalidKey,
     #[error("signature verification failed")]
     Verify,
+    #[error("canonical encoding failed: {0}")]
+    Codec(#[from] geth_codec::CodecError),
 }
 
 pub struct AgentKey {
@@ -73,6 +76,14 @@ impl AgentKey {
     pub fn sign(&self, bytes: &[u8]) -> Vec<u8> {
         self.signing_key.sign(bytes).to_bytes().to_vec()
     }
+
+    pub fn sign_canonical<T: Serialize + ?Sized>(
+        &self,
+        namespace: &str,
+        payload: &T,
+    ) -> Result<Vec<u8>, CryptoError> {
+        Ok(self.sign(&geth_codec::signing_payload(namespace, payload)?))
+    }
 }
 
 pub fn verify(public_key: &[u8], message: &[u8], signature: &[u8]) -> Result<(), CryptoError> {
@@ -85,6 +96,19 @@ pub fn verify(public_key: &[u8], message: &[u8], signature: &[u8]) -> Result<(),
         .map_err(|_| CryptoError::Verify)
 }
 
+pub fn verify_canonical<T: Serialize + ?Sized>(
+    public_key: &[u8],
+    namespace: &str,
+    payload: &T,
+    signature: &[u8],
+) -> Result<(), CryptoError> {
+    verify(
+        public_key,
+        &geth_codec::signing_payload(namespace, payload)?,
+        signature,
+    )
+}
+
 #[must_use]
 pub fn blake3_hex(bytes: &[u8]) -> String {
     blake3::hash(bytes).to_hex().to_string()
@@ -115,4 +139,39 @@ mod tests {
             "3a4aa805ade0d4694a1bb69ad5b9a2f1dffcd4de2136df9a465023722d26e325"
         );
     }
+
+    #[derive(Clone, serde::Serialize)]
+    struct CanonicalSample {
+        version: u8,
+        name: String,
+    }
+
+    #[test]
+    fn canonical_signature_verifies_only_for_matching_namespace() {
+        let key = AgentKey::generate();
+        let sample = CanonicalSample {
+            version: 1,
+            name: "geth".to_owned(),
+        };
+        let signature = key
+            .sign_canonical("geth.keychain.v1@geth.local", &sample)
+            .expect("sign");
+
+        verify_canonical(
+            &key.verifying_key().to_bytes(),
+            "geth.keychain.v1@geth.local",
+            &sample,
+            &signature,
+        )
+        .expect("verify matching namespace");
+        assert!(matches!(
+            verify_canonical(
+                &key.verifying_key().to_bytes(),
+                "geth.auth-op.v1@geth.local",
+                &sample,
+                &signature,
+            ),
+            Err(CryptoError::Verify)
+        ));
+    }
 }