make request signer methods return a result

Signed-off-by: Ryan Tate <ryan.michael.tate@gmail.com>

src/verifier/client.rs

@@ -37,13 +37,13 @@ pub trait Client: Debug {
 pub struct DIDClient {
     id: ClientId,
     vm: String,
-    signer: Arc<dyn RequestSigner + Send + Sync>,
+    signer: Arc<dyn RequestSigner<Error = anyhow::Error> + Send + Sync>,
 }
 
 impl DIDClient {
     pub async fn new(
         vm: String,
-        signer: Arc<dyn RequestSigner + Send + Sync>,
+        signer: Arc<dyn RequestSigner<Error = anyhow::Error> + Send + Sync>,
         resolver: impl JWKResolver,
     ) -> Result<Self> {
         let (id, _f) = vm.rsplit_once('#').context(format!(
@@ -55,7 +55,7 @@ impl DIDClient {
             .await
             .context("unable to resolve key from verification method")?;
 
-        if &*jwk != signer.jwk() {
+        if *jwk != signer.jwk().context("signer did not have a JWK")? {
             bail!(
                 "verification method resolved from DID document did not match public key of signer"
             )
@@ -74,14 +74,14 @@ impl DIDClient {
 pub struct X509SanClient {
     id: ClientId,
     x5c: Vec<Certificate>,
-    signer: Arc<dyn RequestSigner + Send + Sync>,
+    signer: Arc<dyn RequestSigner<Error = anyhow::Error> + Send + Sync>,
     variant: X509SanVariant,
 }
 
 impl X509SanClient {
     pub fn new(
         x5c: Vec<Certificate>,
-        signer: Arc<dyn RequestSigner + Send + Sync>,
+        signer: Arc<dyn RequestSigner<Error = anyhow::Error> + Send + Sync>,
         variant: X509SanVariant,
     ) -> Result<Self> {
         let leaf = &x5c[0];
@@ -145,7 +145,10 @@ impl Client for DIDClient {
         &self,
         body: &AuthorizationRequestObject,
     ) -> Result<String> {
-        let algorithm = self.signer.alg();
+        let algorithm = self
+            .signer
+            .alg()
+            .context("failed to retrieve signing algorithm")?;
         let header = json!({
             "alg": algorithm,
             "kid": self.vm,
@@ -172,7 +175,10 @@ impl Client for X509SanClient {
         &self,
         body: &AuthorizationRequestObject,
     ) -> Result<String> {
-        let algorithm = self.signer.alg();
+        let algorithm = self
+            .signer
+            .alg()
+            .context("failed to retrieve signing algorithm")?;
         let x5c: Vec<String> = self
             .x5c
             .iter()

src/verifier/request_signer.rs

@@ -3,17 +3,34 @@ use anyhow::Result;
 use async_trait::async_trait;
 #[cfg(feature = "p256")]
 use p256::ecdsa::{signature::Signer, Signature, SigningKey};
+#[cfg(feature = "p256")]
+use ssi_claims::jws::{JWSSigner, JWSSignerInfo};
+#[cfg(feature = "p256")]
+use ssi_jwk::Algorithm;
+
 use ssi_jwk::JWK;
 
 use std::fmt::Debug;
 
 #[async_trait]
 pub trait RequestSigner: Debug {
+    type Error: std::fmt::Display;
+
     /// The algorithm that will be used to sign.
-    fn alg(&self) -> &str;
+    fn alg(&self) -> Result<String, Self::Error>;
+
     /// The public JWK of the signer.
-    fn jwk(&self) -> &JWK;
+    fn jwk(&self) -> Result<JWK, Self::Error>;
+
+    /// Sign the payload and return the signature.
     async fn sign(&self, payload: &[u8]) -> Vec<u8>;
+
+    /// Attempt to sign the payload and return the signature.
+    async fn try_sign(&self, payload: &[u8]) -> Result<Vec<u8>, Self::Error> {
+        // default implementation will call sign.
+        // Override for custom error handling.
+        Ok(self.sign(payload).await)
+    }
 }
 
 #[cfg(feature = "p256")]
@@ -30,21 +47,52 @@ impl P256Signer {
         let jwk = serde_json::from_str(&pk.to_jwk_string())?;
         Ok(Self { key, jwk })
     }
+
+    pub fn jwk(&self) -> &JWK {
+        &self.jwk
+    }
 }
 
 #[cfg(feature = "p256")]
 #[async_trait]
 impl RequestSigner for P256Signer {
-    fn alg(&self) -> &str {
-        "ES256"
+    type Error = anyhow::Error;
+
+    fn alg(&self) -> Result<String, Self::Error> {
+        Ok(self
+            .jwk
+            .algorithm
+            .map(|alg| alg)
+            .unwrap_or(Algorithm::ES256)
+            .to_string())
     }
 
-    fn jwk(&self) -> &JWK {
-        &self.jwk
+    fn jwk(&self) -> Result<JWK, Self::Error> {
+        Ok(self.jwk.clone())
     }
 
     async fn sign(&self, payload: &[u8]) -> Vec<u8> {
         let sig: Signature = self.key.sign(payload);
         sig.to_vec()
     }
 }
+
+#[cfg(feature = "p256")]
+impl JWSSigner for P256Signer {
+    async fn fetch_info(&self) -> std::result::Result<JWSSignerInfo, ssi_claims::SignatureError> {
+        let algorithm = self.jwk.algorithm.unwrap_or(Algorithm::ES256);
+
+        let key_id = self.jwk.key_id.clone();
+
+        Ok(JWSSignerInfo { algorithm, key_id })
+    }
+
+    async fn sign_bytes(
+        &self,
+        signing_bytes: &[u8],
+    ) -> std::result::Result<Vec<u8>, ssi_claims::SignatureError> {
+        self.try_sign(signing_bytes).await.map_err(|e| {
+            ssi_claims::SignatureError::Other(format!("Failed to sign bytes: {}", e).into())
+        })
+    }
+}