Fix for issue 418 with unit test

AUTHORS.txt

@@ -39,13 +39,12 @@ ManuelBk <[email protected]>
 Michael Zabka <[email protected]>
 Michiel De Backker <[email protected]>
 Rachel Chen <[email protected]>
+Michael Schexnaydre <[email protected]>
 Robert Eperjesi <[email protected]>
 Ryan Gordon <[email protected]>
 Sam Lancia <[email protected]>
-Sean <[email protected]>
 Sean DuBois <[email protected]>
 Sean DuBois <[email protected]>
-Sean DuBois <[email protected]>
 Sean DuBois <[email protected]>
 Shelikhoo <[email protected]>
 Stefan Tatschner <[email protected]>

conn_test.go

@@ -864,6 +864,14 @@ func TestClientCertificate(t *testing.T) {
 					ClientAuth:   RequireAnyClientCert,
 				},
 			},
+			"RequestClientCert_cert_sigscheme": { // specify signature algorithm
+				clientCfg: &Config{RootCAs: srvCAPool, Certificates: []tls.Certificate{cert}},
+				serverCfg: &Config{
+                                        SignatureSchemes:[]tls.SignatureScheme{tls.ECDSAWithP521AndSHA512}, 
+					Certificates: []tls.Certificate{srvCert},
+					ClientAuth:   RequestClientCert,
+				},
+			},
 			"RequestClientCert_cert": {
 				clientCfg: &Config{RootCAs: srvCAPool, Certificates: []tls.Certificate{cert}},
 				serverCfg: &Config{
@@ -1352,7 +1360,7 @@ func TestServerCertificate(t *testing.T) {
 				}},
 			},
 			"good_ca_custom_verify_peer": {
-				clientCfg: &Config{
+				clientCfg: &Config{                                        
 					RootCAs: caPool,
 					VerifyPeerCertificate: func([][]byte, [][]*x509.Certificate) error {
 						return errWrongCert

crypto.go

@@ -9,7 +9,6 @@ import (
 	"crypto/ed25519"
 	"crypto/rand"
 	"crypto/rsa"
-	"crypto/sha256"
 	"crypto/x509"
 	"encoding/asn1"
 	"encoding/binary"
@@ -118,11 +117,7 @@ func generateCertificateVerify(handshakeBodies []byte, privateKey crypto.Private
 		return p.Sign(rand.Reader, handshakeBodies, crypto.Hash(0))
 	}
 
-	h := sha256.New()
-	if _, err := h.Write(handshakeBodies); err != nil {
-		return nil, err
-	}
-	hashed := h.Sum(nil)
+	hashed := hashAlgorithm.Digest(handshakeBodies)
 
 	switch p := privateKey.(type) {
 	case *ecdsa.PrivateKey:

flight3handler.go

@@ -153,7 +153,8 @@ func flight3Parse(ctx context.Context, c flightConn, state *State, cache *handsh
 		}
 	}
 
-	if _, ok := msgs[handshake.TypeCertificateRequest].(*handshake.MessageCertificateRequest); ok {
+	if creq, ok := msgs[handshake.TypeCertificateRequest].(*handshake.MessageCertificateRequest); ok {
+		state.remoteCertRequestAlgs = creq.SignatureHashAlgorithms
 		state.remoteRequestedCertificate = true
 	}
 

flight5handler.go

@@ -193,7 +193,8 @@ func flight5Generate(c flightConn, state *State, cache *handshakeCache, cfg *han
 		), merged...)
 
 		// Find compatible signature scheme
-		signatureHashAlgo, err := signaturehash.SelectSignatureScheme(cfg.localSignatureSchemes, privateKey)
+
+		signatureHashAlgo, err := signaturehash.SelectSignatureScheme(state.remoteCertRequestAlgs, privateKey)
 		if err != nil {
 			return nil, &alert.Alert{Level: alert.Fatal, Description: alert.InsufficientSecurity}, err
 		}

state.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/pion/dtls/v2/pkg/crypto/elliptic"
 	"github.com/pion/dtls/v2/pkg/crypto/prf"
+	"github.com/pion/dtls/v2/pkg/crypto/signaturehash"
 	"github.com/pion/dtls/v2/pkg/protocol/handshake"
 	"github.com/pion/transport/v3/replaydetector"
 )
@@ -53,6 +54,7 @@ type State struct {
 	handshakeSendSequence      int
 	handshakeRecvSequence      int
 	serverName                 string
+	remoteCertRequestAlgs      []signaturehash.Algorithm
 	remoteRequestedCertificate bool   // Did we get a CertificateRequest
 	localCertificatesVerify    []byte // cache CertificateVerify
 	localVerifyData            []byte // cached VerifyData