Add manual signed peer card exchange

crates/geth-discovery/src/lib.rs

@@ -1,3 +1,4 @@
+use geth_crypto::AgentKey;
 use geth_types::{AgentId, NodeId, UnixMillis};
 use serde::{Deserialize, Serialize};
 
@@ -13,20 +14,93 @@ pub struct PeerCard {
 }
 
 impl PeerCard {
+    pub fn signed(
+        node_id: NodeId,
+        agent_key: &AgentKey,
+        endpoints: Vec<EndpointCandidate>,
+        issued_at: UnixMillis,
+    ) -> Result<Self, DiscoveryError> {
+        let agent_id = agent_key.agent_id();
+        let payload = PeerCardSigningPayload {
+            node_id: node_id.clone(),
+            agent_id: agent_id.clone(),
+            endpoints: endpoints.clone(),
+            issued_at,
+        };
+        let signature = agent_key.sign_canonical(PEER_CARD_SIGNATURE_NAMESPACE, &payload)?;
+        Ok(Self {
+            node_id,
+            agent_id: agent_id.clone(),
+            endpoints,
+            issued_at,
+            signature: SignatureMetadata {
+                namespace: PEER_CARD_SIGNATURE_NAMESPACE.to_owned(),
+                signer: agent_id.to_string(),
+                public_key: agent_key.public_key_hex(),
+                signature: hex::encode(signature),
+            },
+        })
+    }
+
     pub fn validate_candidate(&self) -> Result<(), DiscoveryError> {
         if self.endpoints.is_empty() {
             return Err(DiscoveryError::MissingEndpoint);
         }
+        self.verify_signature()
+    }
+
+    pub fn verify_signature(&self) -> Result<(), DiscoveryError> {
         if self.signature.namespace != PEER_CARD_SIGNATURE_NAMESPACE {
             return Err(DiscoveryError::InvalidSignatureNamespace(
                 self.signature.namespace.clone(),
             ));
         }
-        if self.signature.signer.is_empty() || self.signature.signature.is_empty() {
+        if self.signature.signer.is_empty()
+            || self.signature.public_key.is_empty()
+            || self.signature.signature.is_empty()
+        {
             return Err(DiscoveryError::UnsignedPeerCard);
         }
+        if self.signature.signer != self.agent_id.as_str() {
+            return Err(DiscoveryError::SignerMismatch {
+                signer: self.signature.signer.clone(),
+                agent: self.agent_id.to_string(),
+            });
+        }
+        let public_key = hex::decode(&self.signature.public_key)?;
+        let fingerprint = geth_crypto::key_fingerprint(&public_key);
+        if fingerprint != self.signature.signer {
+            return Err(DiscoveryError::SignerPublicKeyMismatch {
+                signer: self.signature.signer.clone(),
+                fingerprint,
+            });
+        }
+        let signature = hex::decode(&self.signature.signature)?;
+        geth_crypto::verify_canonical(
+            &public_key,
+            PEER_CARD_SIGNATURE_NAMESPACE,
+            &self.signing_payload(),
+            &signature,
+        )?;
         Ok(())
     }
+
+    fn signing_payload(&self) -> PeerCardSigningPayload {
+        PeerCardSigningPayload {
+            node_id: self.node_id.clone(),
+            agent_id: self.agent_id.clone(),
+            endpoints: self.endpoints.clone(),
+            issued_at: self.issued_at,
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+struct PeerCardSigningPayload {
+    node_id: NodeId,
+    agent_id: AgentId,
+    endpoints: Vec<EndpointCandidate>,
+    issued_at: UnixMillis,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
@@ -40,6 +114,8 @@ pub struct EndpointCandidate {
 pub struct SignatureMetadata {
     pub namespace: String,
     pub signer: String,
+    #[serde(default)]
+    pub public_key: String,
     pub signature: String,
 }
 
@@ -94,6 +170,14 @@ pub enum DiscoveryError {
     UnsignedPeerCard,
     #[error("invalid peer card signature namespace: {0}")]
     InvalidSignatureNamespace(String),
+    #[error("peer card signer {signer} does not match agent {agent}")]
+    SignerMismatch { signer: String, agent: String },
+    #[error("peer card signer {signer} does not match public key fingerprint {fingerprint}")]
+    SignerPublicKeyMismatch { signer: String, fingerprint: String },
+    #[error("invalid peer card hex: {0}")]
+    Hex(#[from] hex::FromHexError),
+    #[error("peer card signature error: {0}")]
+    Crypto(#[from] geth_crypto::CryptoError),
 }
 
 #[must_use]
@@ -106,21 +190,19 @@ mod tests {
     use super::*;
 
     fn signed_card() -> PeerCard {
-        PeerCard {
-            node_id: "node:laptop".into(),
-            agent_id: "agent:abc".into(),
-            endpoints: vec![EndpointCandidate {
+        let key = AgentKey::generate();
+        let agent_id = key.agent_id();
+        PeerCard::signed(
+            format!("node:{agent_id}").into(),
+            &key,
+            vec![EndpointCandidate {
                 endpoint_id: "endpoint:iroh".to_owned(),
                 relay_url: None,
                 source: DiscoverySource::Manual,
             }],
-            issued_at: UnixMillis(1),
-            signature: SignatureMetadata {
-                namespace: PEER_CARD_SIGNATURE_NAMESPACE.to_owned(),
-                signer: "agent:abc".to_owned(),
-                signature: "sig:test".to_owned(),
-            },
-        }
+            UnixMillis(1),
+        )
+        .expect("signed card")
     }
 
     #[test]
@@ -146,4 +228,14 @@ mod tests {
             Err(DiscoveryError::UnsignedPeerCard)
         ));
     }
+
+    #[test]
+    fn tampered_peer_card_signature_is_rejected() {
+        let mut card = signed_card();
+        card.endpoints[0].endpoint_id = "endpoint:tampered".to_owned();
+        assert!(matches!(
+            card.validate_candidate(),
+            Err(DiscoveryError::Crypto(geth_crypto::CryptoError::Verify))
+        ));
+    }
 }