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Change the signature context according to protocol role #205

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4 changes: 2 additions & 2 deletions client-state-machine.go
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Original file line number Diff line number Diff line change
Expand Up @@ -819,7 +819,7 @@ func (state clientStateWaitCV) Next(hr handshakeMessageReader) (HandshakeState,
logf(logTypeHandshake, "Handshake Hash to be verified: [%d] %x", len(hcv), hcv)

serverPublicKey := state.serverCertificate.CertificateList[0].CertData.PublicKey
if err := certVerify.Verify(serverPublicKey, hcv); err != nil {
if err := certVerify.Verify(true, serverPublicKey, hcv); err != nil {
logf(logTypeHandshake, "[ClientStateWaitCV] Server signature failed to verify")
return nil, nil, AlertHandshakeFailure
}
Expand Down Expand Up @@ -1021,7 +1021,7 @@ func (state clientStateWaitFinished) Next(hr handshakeMessageReader) (HandshakeS
certificateVerify := &CertificateVerifyBody{Algorithm: certScheme}
logf(logTypeHandshake, "Creating CertVerify: %04x %v", certScheme, state.cryptoParams.Hash)

err = certificateVerify.Sign(cert.PrivateKey, hcv)
err = certificateVerify.Sign(false, cert.PrivateKey, hcv)
if err != nil {
logf(logTypeHandshake, "[ClientStateWaitFinished] Error signing CertificateVerify [%v]", err)
return nil, nil, AlertInternalError
Expand Down
2 changes: 2 additions & 0 deletions crypto.go
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Expand Up @@ -523,6 +523,8 @@ func HkdfExtract(hash crypto.Hash, saltIn, input []byte) []byte {
}

const (
clientCertVerifyContext = "TLS 1.3, client CertificateVerify"
serverCertVerifyContext = "TLS 1.3, server CertificateVerify"
labelExternalBinder = "ext binder"
labelResumptionBinder = "res binder"
labelEarlyTrafficSecret = "c e traffic"
Expand Down
21 changes: 10 additions & 11 deletions handshake-messages.go
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Original file line number Diff line number Diff line change
Expand Up @@ -124,7 +124,6 @@ func (ch *ClientHelloBody) Unmarshal(data []byte) (int, error) {
return read, nil
}

// TODO: File a spec bug to clarify this
func (ch ClientHelloBody) Truncated() ([]byte, error) {
if len(ch.Extensions) == 0 {
return nil, fmt.Errorf("tls.clienthello.truncate: No extensions")
Expand Down Expand Up @@ -205,8 +204,6 @@ func (sh *ServerHelloBody) Unmarshal(data []byte) (int, error) {
//
// For similar reasons, we don't use the `syntax` module here, because this
// struct doesn't map well to standard TLS presentation language concepts.
//
// TODO: File a spec bug
type FinishedBody struct {
VerifyDataLen int
VerifyData []byte
Expand Down Expand Up @@ -351,26 +348,28 @@ func (cv *CertificateVerifyBody) Unmarshal(data []byte) (int, error) {
return syntax.Unmarshal(data, cv)
}

func (cv *CertificateVerifyBody) EncodeSignatureInput(data []byte) []byte {
// TODO: Change context for client auth
// TODO: Put this in a const
const context = "TLS 1.3, server CertificateVerify"
func (cv *CertificateVerifyBody) EncodeSignatureInput(server bool, data []byte) []byte {
context := clientCertVerifyContext
if server {
context = serverCertVerifyContext
}

sigInput := bytes.Repeat([]byte{0x20}, 64)
sigInput = append(sigInput, []byte(context)...)
sigInput = append(sigInput, []byte{0}...)
sigInput = append(sigInput, data...)
return sigInput
}

func (cv *CertificateVerifyBody) Sign(privateKey crypto.Signer, handshakeHash []byte) (err error) {
sigInput := cv.EncodeSignatureInput(handshakeHash)
func (cv *CertificateVerifyBody) Sign(server bool, privateKey crypto.Signer, handshakeHash []byte) (err error) {
sigInput := cv.EncodeSignatureInput(server, handshakeHash)
cv.Signature, err = sign(cv.Algorithm, privateKey, sigInput)
logf(logTypeHandshake, "Signed: alg=[%04x] sigInput=[%x], sig=[%x]", cv.Algorithm, sigInput, cv.Signature)
return
}

func (cv *CertificateVerifyBody) Verify(publicKey crypto.PublicKey, handshakeHash []byte) error {
sigInput := cv.EncodeSignatureInput(handshakeHash)
func (cv *CertificateVerifyBody) Verify(server bool, publicKey crypto.PublicKey, handshakeHash []byte) error {
sigInput := cv.EncodeSignatureInput(server, handshakeHash)
logf(logTypeHandshake, "About to verify: alg=[%04x] sigInput=[%x], sig=[%x]", cv.Algorithm, sigInput, cv.Signature)
return verify(cv.Algorithm, publicKey, sigInput, cv.Signature)
}
Expand Down
29 changes: 19 additions & 10 deletions handshake-messages_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -539,29 +539,38 @@ func TestCertificateVerifyMarshalUnmarshal(t *testing.T) {
_, err = cv.Unmarshal(certVerifyValid[:5])
assertError(t, err, "Unmarshaled a CertificateVerify with no header")

// Test successful sign / verify round-trip
certVerifyValidIn.Algorithm = RSA_PSS_SHA256
err = certVerifyValidIn.Sign(privRSA, handshakeHash)
assertNotError(t, err, "Failed to sign CertificateVerify")

// Test sign failure on algorithm
originalAlg := certVerifyValidIn.Algorithm
certVerifyValidIn.Algorithm = SignatureScheme(0)
err = certVerifyValidIn.Sign(privRSA, handshakeHash)
err = certVerifyValidIn.Sign(true, privRSA, handshakeHash)
assertError(t, err, "Signed CertificateVerify despite bad algorithm")
certVerifyValidIn.Algorithm = originalAlg

// Test successful verify
// Test successful sign / verify round trip (client side)
certVerifyValidIn = CertificateVerifyBody{Algorithm: RSA_PSS_SHA256}
err = certVerifyValidIn.Sign(privRSA, handshakeHash)
err = certVerifyValidIn.Sign(false, privRSA, handshakeHash)
assertNotError(t, err, "Failed to sign CertificateVerify")
err = certVerifyValidIn.Verify(privRSA.Public(), handshakeHash)
err = certVerifyValidIn.Verify(false, privRSA.Public(), handshakeHash)
assertNotError(t, err, "Failed to verify CertificateVerify")

// Test successful sign / verify round trip (server side)
certVerifyValidIn = CertificateVerifyBody{Algorithm: RSA_PSS_SHA256}
err = certVerifyValidIn.Sign(true, privRSA, handshakeHash)
assertNotError(t, err, "Failed to sign CertificateVerify")
err = certVerifyValidIn.Verify(true, privRSA.Public(), handshakeHash)
assertNotError(t, err, "Failed to verify CertificateVerify")

// Test verify failure on client/server difference
certVerifyValidIn = CertificateVerifyBody{Algorithm: RSA_PSS_SHA256}
err = certVerifyValidIn.Sign(true, privRSA, handshakeHash)
assertNotError(t, err, "Failed to sign CertificateVerify")
err = certVerifyValidIn.Verify(false, privRSA.Public(), handshakeHash)
assertError(t, err, "Accpepted CertificateVerify in wrong context")

// Test verify failure on bad algorithm
originalAlg = certVerifyValidIn.Algorithm
certVerifyValidIn.Algorithm = SignatureScheme(0)
err = certVerifyValidIn.Verify(privRSA.Public(), handshakeHash)
err = certVerifyValidIn.Verify(true, privRSA.Public(), handshakeHash)
assertError(t, err, "Verified CertificateVerify despite bad hash algorithm")
certVerifyValidIn.Algorithm = originalAlg
}
Expand Down
4 changes: 2 additions & 2 deletions server-state-machine.go
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Original file line number Diff line number Diff line change
Expand Up @@ -665,7 +665,7 @@ func (state serverStateNegotiated) Next(_ handshakeMessageReader) (HandshakeStat
hcv := handshakeHash.Sum(nil)
logf(logTypeHandshake, "Handshake Hash to be verified: [%d] %x", len(hcv), hcv)

err = certificateVerify.Sign(state.cert.PrivateKey, hcv)
err = certificateVerify.Sign(true, state.cert.PrivateKey, hcv)
if err != nil {
logf(logTypeHandshake, "[ServerStateNegotiated] Error signing CertificateVerify [%v]", err)
return nil, nil, AlertInternalError
Expand Down Expand Up @@ -1061,7 +1061,7 @@ func (state serverStateWaitCV) Next(hr handshakeMessageReader) (HandshakeState,
logf(logTypeHandshake, "Handshake Hash to be verified: [%d] %x", len(hcv), hcv)

clientPublicKey := state.clientCertificate.CertificateList[0].CertData.PublicKey
if err := certVerify.Verify(clientPublicKey, hcv); err != nil {
if err := certVerify.Verify(false, clientPublicKey, hcv); err != nil {
logf(logTypeHandshake, "[ServerStateWaitCV] Failure in client auth verification [%v]", err)
return nil, nil, AlertHandshakeFailure
}
Expand Down
1 change: 1 addition & 0 deletions tls_test.go
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Expand Up @@ -215,6 +215,7 @@ func TestExchangeData(t *testing.T) {

srv := <-srvCh
assertNotNil(t, srv, "Server should have completed handshake")
assertNotError(t, serr, "Error in server handshake")

buf := make([]byte, 16)
buf = buf[0:6]
Expand Down