Add support for ECDSA in Service Providers

samlsp/new.go

@@ -2,21 +2,22 @@
 package samlsp
 
 import (
+	"crypto"
+	"crypto/ecdsa"
 	"crypto/rsa"
 	"crypto/x509"
 	"net/http"
 	"net/url"
 
-	dsig "github.com/russellhaering/goxmldsig"
-
 	"github.com/crewjam/saml"
+	"github.com/golang-jwt/jwt/v4"
 )
 
 // Options represents the parameters for creating a new middleware
 type Options struct {
 	EntityID              string
 	URL                   url.URL
-	Key                   *rsa.PrivateKey
+	Key                   crypto.Signer
 	Certificate           *x509.Certificate
 	Intermediates         []*x509.Certificate
 	HTTPClient            *http.Client
@@ -33,11 +34,23 @@ type Options struct {
 	LogoutBindings        []string
 }
 
+func getDefaultSigningMethod(signer crypto.Signer) jwt.SigningMethod {
+	if signer != nil {
+		switch signer.Public().(type) {
+		case *ecdsa.PublicKey:
+			return jwt.SigningMethodES256
+		case *rsa.PublicKey:
+			return jwt.SigningMethodRS256
+		}
+	}
+	return jwt.SigningMethodRS256
+}
+
 // DefaultSessionCodec returns the default SessionCodec for the provided options,
 // a JWTSessionCodec configured to issue signed tokens.
 func DefaultSessionCodec(opts Options) JWTSessionCodec {
 	return JWTSessionCodec{
-		SigningMethod: defaultJWTSigningMethod,
+		SigningMethod: getDefaultSigningMethod(opts.Key),
 		Audience:      opts.URL.String(),
 		Issuer:        opts.URL.String(),
 		MaxAge:        defaultSessionMaxAge,
@@ -67,7 +80,7 @@ func DefaultSessionProvider(opts Options) CookieSessionProvider {
 // options, a JWTTrackedRequestCodec that uses a JWT to encode TrackedRequests.
 func DefaultTrackedRequestCodec(opts Options) JWTTrackedRequestCodec {
 	return JWTTrackedRequestCodec{
-		SigningMethod: defaultJWTSigningMethod,
+		SigningMethod: getDefaultSigningMethod(opts.Key),
 		Audience:      opts.URL.String(),
 		Issuer:        opts.URL.String(),
 		MaxAge:        saml.MaxIssueDelay,
@@ -99,9 +112,9 @@ func DefaultServiceProvider(opts Options) saml.ServiceProvider {
 	if opts.ForceAuthn {
 		forceAuthn = &opts.ForceAuthn
 	}
-	signatureMethod := dsig.RSASHA1SignatureMethod
-	if !opts.SignRequest {
-		signatureMethod = ""
+	var signatureMethod string
+	if opts.SignRequest {
+		signatureMethod = "auto"
 	}
 
 	if opts.DefaultRedirectURI == "" {

samlsp/request_tracker_jwt.go

@@ -1,7 +1,7 @@
 package samlsp
 
 import (
-	"crypto/rsa"
+	"crypto"
 	"fmt"
 	"time"
 
@@ -10,15 +10,13 @@
 	"github.com/crewjam/saml"
 )
 
-var defaultJWTSigningMethod = jwt.SigningMethodRS256
-
 // JWTTrackedRequestCodec encodes TrackedRequests as signed JWTs
 type JWTTrackedRequestCodec struct {
 	SigningMethod jwt.SigningMethod
 	Audience      string
 	Issuer        string
 	MaxAge        time.Duration
-	Key           *rsa.PrivateKey
+	Key           crypto.Signer
 }
 
 var _ TrackedRequestCodec = JWTTrackedRequestCodec{}
@@ -61,7 +59,7 @@
 	if err != nil {
 		return nil, err
 	}
 	if !claims.VerifyAudience(s.Audience, true) {
 		return nil, fmt.Errorf("expected audience %q, got %q", s.Audience, claims.Audience)
 	}
 	if !claims.VerifyIssuer(s.Issuer, true) {

samlsp/session_jwt.go

@@ -1,7 +1,7 @@
 package samlsp
 
 import (
-	"crypto/rsa"
+	"crypto"
 	"errors"
 	"fmt"
 	"time"
@@ -23,7 +23,7 @@ type JWTSessionCodec struct {
 	Audience      string
 	Issuer        string
 	MaxAge        time.Duration
-	Key           *rsa.PrivateKey
+	Key           crypto.Signer
 }
 
 var _ SessionCodec = JWTSessionCodec{}

service_provider.go

@@ -4,7 +4,7 @@ import (
 	"bytes"
 	"compress/flate"
 	"context"
-	"crypto/rsa"
+	"crypto"
 	"crypto/tls"
 	"crypto/x509"
 	"encoding/base64"
@@ -67,7 +67,7 @@ type ServiceProvider struct {
 	EntityID string
 
 	// Key is the RSA private key we use to sign requests.
-	Key *rsa.PrivateKey
+	Key crypto.Signer
 
 	// Certificate is the RSA public part of Key.
 	Certificate   *x509.Certificate
@@ -117,7 +117,7 @@ type ServiceProvider struct {
 	// to verify signatures.
 	SignatureVerifier SignatureVerifier
 
-	// SignatureMethod, if non-empty, authentication requests will be signed
+	// SignatureMethod, if non-empty, authentication requests will be signed. "auto" will determine method based on certificate type.
 	SignatureMethod string
 
 	// LogoutBindings specify the bindings available for SLO endpoint. If empty,
@@ -141,6 +141,11 @@ const DefaultValidDuration = time.Hour * 24 * 2
 // DefaultCacheDuration is how long we ask the IDP to cache the SP metadata.
 const DefaultCacheDuration = time.Hour * 24 * 1
 
+// SignRequests returns true if the service provider should sign requests.
+func (sp *ServiceProvider) SignRequests() bool {
+	return len(sp.SignatureMethod) > 0
+}
+
 // Metadata returns the service provider metadata
 func (sp *ServiceProvider) Metadata() *EntityDescriptor {
 	validDuration := DefaultValidDuration
@@ -245,6 +250,19 @@ func (sp *ServiceProvider) MakeRedirectAuthenticationRequest(relayState string)
 	return req.Redirect(relayState, sp)
 }
 
+// GetSignatureMethod returns the appropriate string to represent the
+// signature method for the service provider.
+func (sp *ServiceProvider) GetSignatureMethod() (string, error) {
+	if sp.SignatureMethod == "auto" {
+		signingContext, err := GetSigningContext(sp)
+		if err != nil {
+			return "auto", err
+		}
+		return signingContext.GetSignatureMethodIdentifier(), nil
+	}
+	return sp.SignatureMethod, nil
+}
+
 // Redirect returns a URL suitable for using the redirect binding with the request
 func (r *AuthnRequest) Redirect(relayState string, sp *ServiceProvider) (*url.URL, error) {
 	w := &bytes.Buffer{}
@@ -274,13 +292,16 @@ func (r *AuthnRequest) Redirect(relayState string, sp *ServiceProvider) (*url.UR
 	if relayState != "" {
 		query += "&RelayState=" + relayState
 	}
-	if len(sp.SignatureMethod) > 0 {
-		query += "&SigAlg=" + url.QueryEscape(sp.SignatureMethod)
+	if sp.SignRequests() {
 		signingContext, err := GetSigningContext(sp)
-
 		if err != nil {
 			return nil, err
 		}
+		sigMethod, err := sp.GetSignatureMethod()
+		if err != nil {
+			return nil, err
+		}
+		query += "&SigAlg=" + url.QueryEscape(sigMethod)
 
 		sig, err := signingContext.SignString(query)
 		if err != nil {
@@ -391,7 +412,7 @@ func (sp *ServiceProvider) MakeArtifactResolveRequest(artifactID string) (*Artif
 		Artifact: artifactID,
 	}
 
-	if len(sp.SignatureMethod) > 0 {
+	if sp.SignRequests() {
 		if err := sp.SignArtifactResolve(&req); err != nil {
 			return nil, err
 		}
@@ -428,7 +449,7 @@ func (sp *ServiceProvider) MakeAuthenticationRequest(idpURL string, binding stri
 		RequestedAuthnContext: sp.RequestedAuthnContext,
 	}
 	// We don't need to sign the XML document if the IDP uses HTTP-Redirect binding
-	if len(sp.SignatureMethod) > 0 && binding == HTTPPostBinding {
+	if sp.SignRequests() && binding == HTTPPostBinding {
 		if err := sp.SignAuthnRequest(&req); err != nil {
 			return nil, err
 		}
@@ -449,13 +470,13 @@ func GetSigningContext(sp *ServiceProvider) (*dsig.SigningContext, error) {
 	// }
 	keyStore := dsig.TLSCertKeyStore(keyPair)
 
-	if sp.SignatureMethod != dsig.RSASHA1SignatureMethod &&
-		sp.SignatureMethod != dsig.RSASHA256SignatureMethod &&
-		sp.SignatureMethod != dsig.RSASHA512SignatureMethod {
-		return nil, fmt.Errorf("invalid signing method %s", sp.SignatureMethod)
+	signer, _ := sp.Key.(crypto.Signer)
+	chain, _ := keyStore.GetChain()
+	signingContext, err := dsig.NewSigningContext(signer, chain)
+	if err != nil {
+		return nil, err
 	}
-	signatureMethod := sp.SignatureMethod
-	signingContext := dsig.NewDefaultSigningContext(keyStore)
+	signatureMethod := signingContext.GetSignatureMethodIdentifier()
 	signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
 	if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
 		return nil, err
@@ -1170,13 +1191,13 @@ func (sp *ServiceProvider) SignLogoutRequest(req *LogoutRequest) error {
 	// }
 	keyStore := dsig.TLSCertKeyStore(keyPair)
 
-	if sp.SignatureMethod != dsig.RSASHA1SignatureMethod &&
-		sp.SignatureMethod != dsig.RSASHA256SignatureMethod &&
-		sp.SignatureMethod != dsig.RSASHA512SignatureMethod {
-		return fmt.Errorf("invalid signing method %s", sp.SignatureMethod)
+	signer, _ := sp.Key.(crypto.Signer)
+	chain, _ := keyStore.GetChain()
+	signingContext, err := dsig.NewSigningContext(signer, chain)
+	if err != nil {
+		return err
 	}
-	signatureMethod := sp.SignatureMethod
-	signingContext := dsig.NewDefaultSigningContext(keyStore)
+	signatureMethod := signingContext.GetSignatureMethodIdentifier()
 	signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
 	if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
 		return err
@@ -1213,7 +1234,7 @@ func (sp *ServiceProvider) MakeLogoutRequest(idpURL, nameID string) (*LogoutRequ
 			SPNameQualifier: sp.Metadata().EntityID,
 		},
 	}
-	if len(sp.SignatureMethod) > 0 {
+	if sp.SignRequests() {
 		if err := sp.SignLogoutRequest(&req); err != nil {
 			return nil, err
 		}
@@ -1327,7 +1348,7 @@ func (sp *ServiceProvider) MakeLogoutResponse(idpURL, logoutRequestID string) (*
 		},
 	}
 
-	if len(sp.SignatureMethod) > 0 {
+	if sp.SignRequests() {
 		if err := sp.SignLogoutResponse(&response); err != nil {
 			return nil, err
 		}
@@ -1435,13 +1456,13 @@ func (sp *ServiceProvider) SignLogoutResponse(resp *LogoutResponse) error {
 	// }
 	keyStore := dsig.TLSCertKeyStore(keyPair)
 
-	if sp.SignatureMethod != dsig.RSASHA1SignatureMethod &&
-		sp.SignatureMethod != dsig.RSASHA256SignatureMethod &&
-		sp.SignatureMethod != dsig.RSASHA512SignatureMethod {
-		return fmt.Errorf("invalid signing method %s", sp.SignatureMethod)
+	signer, _ := sp.Key.(crypto.Signer)
+	chain, _ := keyStore.GetChain()
+	signingContext, err := dsig.NewSigningContext(signer, chain)
+	if err != nil {
+		return err
 	}
-	signatureMethod := sp.SignatureMethod
-	signingContext := dsig.NewDefaultSigningContext(keyStore)
+	signatureMethod := signingContext.GetSignatureMethodIdentifier()
 	signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
 	if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
 		return err

service_provider_test.go

@@ -350,7 +350,7 @@ func TestSPFailToProduceSignedRequestWithBogusSignatureMethod(t *testing.T) {
 	assert.Check(t, err)
 
 	_, err = s.MakeRedirectAuthenticationRequest("relayState")
-	assert.Check(t, is.ErrorContains(err, "invalid signing method bogus"))
+	assert.Check(t, is.ErrorContains(err, "unknown SignatureMethod: bogus"))
 }
 
 func TestSPCanProducePostLogoutRequest(t *testing.T) {
@@ -1665,7 +1665,7 @@ func TestMakeSignedArtifactResolveRequestWithBogusSignatureMethod(t *testing.T)
 	}
 
 	_, err := sp.MakeArtifactResolveRequest("artifactId")
-	assert.Check(t, is.ErrorContains(err, "invalid signing method bogus"))
+	assert.Check(t, is.ErrorContains(err, "unknown SignatureMethod: bogus"))
 
 }