fix(core): add attestation sig validation

crates/core/src/attestation.rs

@@ -264,6 +264,7 @@ impl Body {
 ///
 /// See [module level documentation](crate::attestation) for more information.
 #[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(try_from = "validation::AttestationUnchecked")]
 pub struct Attestation {
     /// The signature of the attestation.
     pub signature: Signature,
@@ -287,3 +288,73 @@ impl Attestation {
         PresentationBuilder::new(provider, self)
     }
 }
+
+/// Invalid attestation error.
+#[derive(Debug, thiserror::Error)]
+#[error("invalid attestation: {0}")]
+pub struct InvalidAttestation(String);
+
+mod validation {
+    use super::*;
+    use crate::{serialize::CanonicalSerialize, signing::SignatureVerifierProvider};
+
+    #[derive(Debug, Deserialize)]
+    pub(super) struct AttestationUnchecked {
+        signature: Signature,
+        header: Header,
+        body: Body,
+    }
+
+    impl TryFrom<AttestationUnchecked> for Attestation {
+        type Error = InvalidAttestation;
+
+        fn try_from(unchecked: AttestationUnchecked) -> Result<Self, Self::Error> {
+            let provider = SignatureVerifierProvider::default();
+            let verifier = provider.get(&unchecked.signature.alg).map_err(|_| {
+                InvalidAttestation(format!(
+                    "invalid signature algorithm id {:?}",
+                    unchecked.signature.alg
+                ))
+            })?;
+
+            verifier
+                .verify(
+                    &unchecked.body.verifying_key.data,
+                    &CanonicalSerialize::serialize(&unchecked.header),
+                    &unchecked.signature.data,
+                )
+                .map_err(|_| InvalidAttestation("failed to verify the signature".into()))?;
+
+            Ok(Self {
+                body: unchecked.body,
+                header: unchecked.header,
+                signature: unchecked.signature,
+            })
+        }
+    }
+
+    #[cfg(test)]
+    mod tests {
+        use crate::{attestation::Attestation, fixtures::basic_attestation_fixture};
+
+        #[test]
+        fn test_validation_ok() {
+            let attestation = basic_attestation_fixture();
+            let bytes = bincode::serialize(&attestation).unwrap();
+            let result: Result<Attestation, Box<bincode::ErrorKind>> = bincode::deserialize(&bytes);
+            assert!(result.is_ok());
+        }
+
+        #[test]
+        fn test_validation_err() {
+            let mut attestation = basic_attestation_fixture();
+
+            // Corrupt the signature.
+            attestation.signature.data[1] = attestation.signature.data[1].wrapping_add(1);
+
+            let bytes = bincode::serialize(&attestation).unwrap();
+            let result: Result<Attestation, Box<bincode::ErrorKind>> = bincode::deserialize(&bytes);
+            assert!(result.is_err());
+        }
+    }
+}

crates/core/src/fixtures.rs

@@ -6,14 +6,15 @@ pub use provider::FixtureEncodingProvider;
 
 use hex::FromHex;
 use p256::ecdsa::SigningKey;
+use tlsn_data_fixtures::http::{request::GET_WITH_HEADER, response::OK_JSON};
 
 use crate::{
     attestation::{Attestation, AttestationConfig, Extension},
     connection::{
         Certificate, ConnectionInfo, HandshakeData, HandshakeDataV1_2, KeyType, ServerCertData,
         ServerEphemKey, ServerName, ServerSignature, SignatureScheme, TlsVersion, TranscriptLength,
     },
-    hash::HashAlgorithm,
+    hash::{Blake3, HashAlgorithm},
     request::{Request, RequestConfig},
     signing::SignatureAlgId,
     transcript::{
@@ -263,3 +264,28 @@ pub fn attestation_fixture(
 
     attestation_builder.build(&provider).unwrap()
 }
+
+/// Returns a basic attestation fixture for testing.
+pub fn basic_attestation_fixture() -> Attestation {
+    let transcript = Transcript::new(GET_WITH_HEADER, OK_JSON);
+    let connection = ConnectionFixture::tlsnotary(transcript.length());
+
+    let RequestFixture {
+        mut request,
+        encoding_tree: _,
+    } = request_fixture(
+        transcript.clone(),
+        encoding_provider(GET_WITH_HEADER, OK_JSON),
+        connection.clone(),
+        Blake3::default(),
+        Vec::new(),
+    );
+
+    request.encoding_commitment_root = None;
+    attestation_fixture(
+        request,
+        connection,
+        SignatureAlgId::SECP256K1,
+        encoder_secret(),
+    )
+}