Add support for hardware security module (HSM) signing.

goxmldsig was recently updated to support HSMs. This is done by supporting
signing using the `crypto.Signer` directly, which is how HSMs are able to
sign things in golang.

This commit adds a new field `Signer` to the `IdentityProvider` which takes
precedence over the `Key` field when creating the `SigningContext`. The `Key`
field has been left in place to maintain backwards compatibility.

Tests have been updated to verify that this functions, and the `samlidp`
example identity provider has been updated such that it now supports a
`Signer` option. Additionally, `NewIdentifyProviderTest` has been corrected to
`NewIdentityProviderTest`.

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/kr/pretty v0.3.1
 	github.com/mattermost/xml-roundtrip-validator v0.1.0
 	github.com/pkg/errors v0.9.1 // indirect
-	github.com/russellhaering/goxmldsig v1.2.0
+	github.com/russellhaering/goxmldsig v1.3.0
 	github.com/stretchr/testify v1.8.1
 	github.com/zenazn/goji v1.0.1
 	golang.org/x/crypto v0.0.0-20220128200615-198e4374d7ed

go.sum

@@ -35,8 +35,8 @@ github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTE
 github.com/rogpeppe/go-internal v1.8.0/go.mod h1:WmiCO8CzOY8rg0OYDC4/i/2WRWAB6poM+XZ2dLUbcbE=
 github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZVejAe8=
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
-github.com/russellhaering/goxmldsig v1.2.0 h1:Y6GTTc9Un5hCxSzVz4UIWQ/zuVwDvzJk80guqzwx6Vg=
-github.com/russellhaering/goxmldsig v1.2.0/go.mod h1:gM4MDENBQf7M+V824SGfyIUVFWydB7n0KkEubVJl+Tw=
+github.com/russellhaering/goxmldsig v1.3.0 h1:DllIWUgMy0cRUMfGiASiYEa35nsieyD3cigIwLonTPM=
+github.com/russellhaering/goxmldsig v1.3.0/go.mod h1:gM4MDENBQf7M+V824SGfyIUVFWydB7n0KkEubVJl+Tw=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=

identity_provider.go

@@ -96,6 +96,7 @@ type AssertionMaker interface {
 // and password).
 type IdentityProvider struct {
 	Key                     crypto.PrivateKey
+	Signer                  crypto.Signer
 	Logger                  logger.Interface
 	Certificate             *x509.Certificate
 	Intermediates           []*x509.Certificate
@@ -830,24 +831,8 @@ const canonicalizerPrefixList = ""
 
 // MakeAssertionEl sets `AssertionEl` to a signed, possibly encrypted, version of `Assertion`.
 func (req *IdpAuthnRequest) MakeAssertionEl() error {
-	keyPair := tls.Certificate{
-		Certificate: [][]byte{req.IDP.Certificate.Raw},
-		PrivateKey:  req.IDP.Key,
-		Leaf:        req.IDP.Certificate,
-	}
-	for _, cert := range req.IDP.Intermediates {
-		keyPair.Certificate = append(keyPair.Certificate, cert.Raw)
-	}
-	keyStore := dsig.TLSCertKeyStore(keyPair)
-
-	signatureMethod := req.IDP.SignatureMethod
-	if signatureMethod == "" {
-		signatureMethod = dsig.RSASHA1SignatureMethod
-	}
-
-	signingContext := dsig.NewDefaultSigningContext(keyStore)
-	signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
-	if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
+	signingContext, err := req.signingContext()
+	if err != nil {
 		return err
 	}
 
@@ -1048,24 +1033,8 @@ func (req *IdpAuthnRequest) MakeResponse() error {
 
 	// Sign the response element (we've already signed the Assertion element)
 	{
-		keyPair := tls.Certificate{
-			Certificate: [][]byte{req.IDP.Certificate.Raw},
-			PrivateKey:  req.IDP.Key,
-			Leaf:        req.IDP.Certificate,
-		}
-		for _, cert := range req.IDP.Intermediates {
-			keyPair.Certificate = append(keyPair.Certificate, cert.Raw)
-		}
-		keyStore := dsig.TLSCertKeyStore(keyPair)
-
-		signatureMethod := req.IDP.SignatureMethod
-		if signatureMethod == "" {
-			signatureMethod = dsig.RSASHA1SignatureMethod
-		}
-
-		signingContext := dsig.NewDefaultSigningContext(keyStore)
-		signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
-		if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
+		signingContext, err := req.signingContext()
+		if err != nil {
 			return err
 		}
 
@@ -1083,3 +1052,42 @@ func (req *IdpAuthnRequest) MakeResponse() error {
 	req.ResponseEl = responseEl
 	return nil
 }
+
+// signingContext will create a signing context for the request.
+func (req *IdpAuthnRequest) signingContext() (signingContext *dsig.SigningContext, err error) {
+	// Create a cert chain based off of the IDP cert and its intermediates.
+	certificates := [][]byte{req.IDP.Certificate.Raw}
+	for _, cert := range req.IDP.Intermediates {
+		certificates = append(certificates, cert.Raw)
+	}
+
+	// If signer is set, use it instead of the private key.
+	if req.IDP.Signer != nil {
+		signingContext, err = dsig.NewSigningContext(req.IDP.Signer, certificates)
+		if err != nil {
+			return
+		}
+	} else {
+		keyPair := tls.Certificate{
+			Certificate: certificates,
+			PrivateKey:  req.IDP.Key,
+			Leaf:        req.IDP.Certificate,
+		}
+		keyStore := dsig.TLSCertKeyStore(keyPair)
+
+		signingContext = dsig.NewDefaultSigningContext(keyStore)
+	}
+
+	// Default to using SHA1 if the signature method isn't set.
+	signatureMethod := req.IDP.SignatureMethod
+	if signatureMethod == "" {
+		signatureMethod = dsig.RSASHA1SignatureMethod
+	}
+
+	signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
+	if err = signingContext.SetSignatureMethod(signatureMethod); err != nil {
+		return
+	}
+
+	return
+}

identity_provider_go116_test.go

@@ -18,7 +18,7 @@ import (
 )
 
 func TestIDPHTTPCanHandleSSORequest(t *testing.T) {
-	test := NewIdentifyProviderTest(t)
+	test := NewIdentityProviderTest(t, applyKey)
 	w := httptest.NewRecorder()
 
 	const validRequest = `lJJBayoxFIX%2FypC9JhnU5wszAz7lgWCLaNtFd5fMbQ1MkmnunVb%2FfUfbUqEgdhs%2BTr5zkmLW8S5s8KVD4mzvm0Cl6FIwEciRCeCRDFuznd2sTD5Upk2Ro42NyGZEmNjFMI%2BBOo9pi%2BnVWbzfrEqxY27JSEntEPfg2waHNnpJ4JtcgiWRLfoLXYBjwDfu6p%2B8JIoiWy5K4eqBUipXIzVRUwXKKtRK53qkJ3qqQVuNPUjU4TIQQ%2BBS5EqPBzofKH2ntBn%2FMervo8jWnyX%2BuVC78FwKkT1gopNKX1JUxSklXTMIfM0gsv8xeeDL%2BPGk7%2FF0Qg0GdnwQ1cW5PDLUwFDID6uquO1Dlot1bJw9%2FPLRmia%2BzRMCYyk4dSiq6205QSDXOxfy3KAq5Pkvqt4DAAD%2F%2Fw%3D%3D`

identity_provider_go117_test.go

@@ -18,7 +18,7 @@ import (
 )
 
 func TestIDPHTTPCanHandleSSORequest(t *testing.T) {
-	test := NewIdentifyProviderTest(t)
+	test := NewIdentityProviderTest(t, applyKey)
 	w := httptest.NewRecorder()
 
 	const validRequest = `lJJBayoxFIX%2FypC9JhnU5wszAz7lgWCLaNtFd5fMbQ1MkmnunVb%2FfUfbUqEgdhs%2BTr5zkmLW8S5s8KVD4mzvm0Cl6FIwEciRCeCRDFuznd2sTD5Upk2Ro42NyGZEmNjFMI%2BBOo9pi%2BnVWbzfrEqxY27JSEntEPfg2waHNnpJ4JtcgiWRLfoLXYBjwDfu6p%2B8JIoiWy5K4eqBUipXIzVRUwXKKtRK53qkJ3qqQVuNPUjU4TIQQ%2BBS5EqPBzofKH2ntBn%2FMervo8jWnyX%2BuVC78FwKkT1gopNKX1JUxSklXTMIfM0gsv8xeeDL%2BPGk7%2FF0Qg0GdnwQ1cW5PDLUwFDID6uquO1Dlot1bJw9%2FPLRmia%2BzRMCYyk4dSiq6205QSDXOxfy3KAq5Pkvqt4DAAD%2F%2Fw%3D%3D`