Decode signature from assertion response

Cargo.toml

@@ -14,6 +14,7 @@ cainome = { git = "https://github.com/piniom/cainome", tag="v0.2.4-expand", feat
     "abigen-rs", "expand-expr"
 ] }
 cairo-lang-starknet = "2.4.0"
+ecdsa = "0.16.9"
 futures = "0.3"
 lazy_static = "1"
 p256 = "0.13"
@@ -30,7 +31,7 @@ u256-literal = "1"
 url = "2"
 wasm-bindgen = "0.2"
 wasm-bindgen-futures = "0.4.42"
-wasm-webauthn = { git = "https://github.com/broody/wasm-webauthn" }
+wasm-webauthn = { git = "https://github.com/broody/wasm-webauthn", rev = "f54bdbc3b4c5da2679e6f74278295b3924b56db5" }
 webauthn-rs-proto = "0.4"
 account-sdk = { path = "crates/account_sdk" }
 tokio = { version = "1", features = ["macros", "time"] }

crates/account_sdk/Cargo.toml

@@ -14,6 +14,7 @@ async-trait.workspace = true
 base64.workspace = true
 cainome.workspace = true
 cairo-lang-starknet.workspace = true
+ecdsa.workspace = true
 futures.workspace = true
 lazy_static.workspace = true
 p256.workspace = true
@@ -31,11 +32,11 @@ url.workspace = true
 wasm-bindgen-futures.workspace = true
 wasm-bindgen.workspace = true
 wasm-webauthn.workspace = true
+web-sys = "0.3.69"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 tokio.workspace = true
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 wasm-bindgen-test = "0.3.34"
 js-sys = "0.3.69"
-web-sys = "0.3.69"

crates/account_sdk/src/webauthn_signer/signers/device.rs

@@ -1,5 +1,6 @@
 use async_trait::async_trait;
 use futures::channel::oneshot;
+use p256::NistP256;
 use std::result::Result;
 use wasm_bindgen_futures::spawn_local;
 use wasm_webauthn::*;
@@ -130,15 +131,23 @@
 impl Signer for DeviceSigner {
     async fn sign(&self, challenge: &[u8]) -> Result<AuthenticatorAssertionResponse, SignError> {
         let GetAssertionResponse {
-            signature,
+            signature: encoded_sig,
+            rp_id_hash,
             client_data_json,
             flags,
             counter,
         } = self.get_assertion(challenge).await?;
 
+        let ecdsa_sig = ecdsa::Signature::<NistP256>::from_der(&encoded_sig).unwrap();
+        let r = ecdsa_sig.r().to_bytes(); 
+        let s = ecdsa_sig.s().to_bytes();
+
+        let mut signature = r.as_slice().to_vec();
+        signature.extend_from_slice(s.as_slice());
+
         Ok(AuthenticatorAssertionResponse {
             authenticator_data: AuthenticatorData {
-                rp_id_hash: [0; 32],
+                rp_id_hash,
                 flags,
                 sign_count: counter,
             },