Add support for signed authnRequest (crewjam#296)

* Fixes handling signed response with encrypted assertions When the response is signed, the verification must happen before the assertion is decrypted since the encrypted XML is used in the signature digest. The response signature is sufficient unless the assertion is also signed in which case both must be valid. * Add support for signed authnRequests
seongwoohong · Dec 18, 2020 · a0fe4eb · a0fe4eb
1 parent 7296b3b
commit a0fe4eb
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Showing 4 changed files with 160 additions and 11 deletions.
diff --git a/example/trivial/trivial.go b/example/trivial/trivial.go
@@ -27,7 +27,7 @@ func main() {
 	}
 
 	rootURL, _ := url.Parse("http://localhost:8000")
-	idpMetadataURL, _ := url.Parse("https://www.testshib.org/metadata/testshib-providers.xml")
+	idpMetadataURL, _ := url.Parse("https://samltest.id/saml/idp")
 
 	idpMetadata, err := samlsp.FetchMetadata(
 		context.Background(),
@@ -42,6 +42,7 @@ func main() {
 		IDPMetadata: idpMetadata,
 		Key:         keyPair.PrivateKey.(*rsa.PrivateKey),
 		Certificate: keyPair.Leaf,
+		SignRequest: true,
 	})
 	if err != nil {
 		panic(err) // TODO handle error

diff --git a/samlsp/new.go b/samlsp/new.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"crypto/rsa"
 	"crypto/x509"
+	dsig "github.com/russellhaering/goxmldsig"
 	"net/http"
 	"net/url"
 	"time"
@@ -22,6 +23,7 @@ type Options struct {
 	Intermediates     []*x509.Certificate
 	AllowIDPInitiated bool
 	IDPMetadata       *saml.EntityDescriptor
+	SignRequest       bool
 	ForceAuthn        bool // TODO(ross): this should be *bool
 
 	// The following fields exist <= 0.3.0, but are superceded by the new
@@ -125,6 +127,10 @@ func DefaultServiceProvider(opts Options) saml.ServiceProvider {
 	if opts.ForceAuthn {
 		forceAuthn = &opts.ForceAuthn
 	}
+	signatureMethod := dsig.RSASHA1SignatureMethod
+	if !opts.SignRequest {
+		signatureMethod = ""
+	}
 
 	return saml.ServiceProvider{
 		EntityID:          opts.EntityID,
@@ -136,6 +142,7 @@ func DefaultServiceProvider(opts Options) saml.ServiceProvider {
 		SloURL:            *sloURL,
 		IDPMetadata:       opts.IDPMetadata,
 		ForceAuthn:        forceAuthn,
+		SignatureMethod:   signatureMethod,
 		AllowIDPInitiated: opts.AllowIDPInitiated,
 	}
 }

diff --git a/service_provider.go b/service_provider.go
@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"compress/flate"
 	"crypto/rsa"
+	"crypto/tls"
 	"crypto/x509"
 	"encoding/base64"
 	"encoding/xml"
@@ -101,6 +102,9 @@ type ServiceProvider struct {
 	// SignatureVerifier, if non-nil, allows you to implement an alternative way
 	// to verify signatures.
 	SignatureVerifier SignatureVerifier
+
+	// SignatureMethod, if non-empty, authentication requests will be signed
+	SignatureMethod string
 }
 
 // MaxIssueDelay is the longest allowed time between when a SAML assertion is
@@ -126,7 +130,7 @@ func (sp *ServiceProvider) Metadata() *EntityDescriptor {
 		validDuration = sp.MetadataValidDuration
 	}
 
-	authnRequestsSigned := false
+	authnRequestsSigned := len(sp.SignatureMethod) > 0
 	wantAssertionsSigned := true
 	validUntil := TimeNow().Add(validDuration)
 
@@ -137,12 +141,6 @@ func (sp *ServiceProvider) Metadata() *EntityDescriptor {
 			certBytes = append(certBytes, intermediate.Raw...)
 		}
 		keyDescriptors = []KeyDescriptor{
-			{
-				Use: "signing",
-				KeyInfo: KeyInfo{
-					Certificate: base64.StdEncoding.EncodeToString(certBytes),
-				},
-			},
 			{
 				Use: "encryption",
 				KeyInfo: KeyInfo{
@@ -156,6 +154,14 @@ func (sp *ServiceProvider) Metadata() *EntityDescriptor {
 				},
 			},
 		}
+		if len(sp.SignatureMethod) > 0 {
+			keyDescriptors = append(keyDescriptors, KeyDescriptor{
+				Use: "signing",
+				KeyInfo: KeyInfo{
+					Certificate: base64.StdEncoding.EncodeToString(certBytes),
+				},
+			})
+		}
 	}
 
 	return &EntityDescriptor{
@@ -330,9 +336,51 @@ func (sp *ServiceProvider) MakeAuthenticationRequest(idpURL string) (*AuthnReque
 		},
 		ForceAuthn: sp.ForceAuthn,
 	}
+	if len(sp.SignatureMethod) > 0 {
+		if err := sp.SignAuthnRequest(&req); err != nil {
+			return nil, err
+		}
+	}
 	return &req, nil
 }
 
+// SignAuthnRequest adds the `Signature` element to the `AuthnRequest`.
+func (sp *ServiceProvider) SignAuthnRequest(req *AuthnRequest) error {
+	keyPair := tls.Certificate{
+		Certificate: [][]byte{sp.Certificate.Raw},
+		PrivateKey:  sp.Key,
+		Leaf:        sp.Certificate,
+	}
+	// TODO: add intermediates for SP
+	//for _, cert := range sp.Intermediates {
+	//	keyPair.Certificate = append(keyPair.Certificate, cert.Raw)
+	//}
+	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)
+	}
+	signatureMethod := sp.SignatureMethod
+	signingContext := dsig.NewDefaultSigningContext(keyStore)
+	signingContext.Canonicalizer = dsig.MakeC14N10ExclusiveCanonicalizerWithPrefixList(canonicalizerPrefixList)
+	if err := signingContext.SetSignatureMethod(signatureMethod); err != nil {
+		return err
+	}
+
+	assertionEl := req.Element()
+
+	signedRequestEl, err := signingContext.SignEnveloped(assertionEl)
+	if err != nil {
+		return err
+	}
+
+	sigEl := signedRequestEl.Child[len(signedRequestEl.Child)-1]
+	req.Signature = sigEl.(*etree.Element)
+	return nil
+}
+
 // MakePostAuthenticationRequest creates a SAML authentication request using
 // the HTTP-POST binding. It returns HTML text representing an HTML form that
 // can be sent presented to a browser to initiate the login process.

diff --git a/service_provider_test.go b/service_provider_test.go
@@ -98,7 +98,7 @@ func TestSPCanSetAuthenticationNameIDFormat(t *testing.T) {
 	assert.Equal(t, string(EmailAddressNameIDFormat), *req.NameIDPolicy.Format)
 }
 
-func TestSPCanProduceMetadata(t *testing.T) {
+func TestSPCanProduceMetadataWithEncryptionCert(t *testing.T) {
 	test := NewServiceProviderTest()
 	s := ServiceProvider{
 		Key:         test.Key,
@@ -116,13 +116,43 @@ func TestSPCanProduceMetadata(t *testing.T) {
 	assert.Equal(t, ""+
 		"<EntityDescriptor xmlns=\"urn:oasis:names:tc:SAML:2.0:metadata\" validUntil=\"2015-12-03T01:57:09Z\" entityID=\"https://example.com/saml2/metadata\">\n"+
 		"  <SPSSODescriptor xmlns=\"urn:oasis:names:tc:SAML:2.0:metadata\" validUntil=\"2015-12-03T01:57:09Z\" protocolSupportEnumeration=\"urn:oasis:names:tc:SAML:2.0:protocol\" AuthnRequestsSigned=\"false\" WantAssertionsSigned=\"true\">\n"+
-		"    <KeyDescriptor use=\"signing\">\n"+
+		"    <KeyDescriptor use=\"encryption\">\n"+
 		"      <KeyInfo xmlns=\"http://www.w3.org/2000/09/xmldsig#\">\n"+
 		"        <X509Data>\n"+
 		"          <X509Certificate>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</X509Certificate>\n"+
 		"        </X509Data>\n"+
 		"      </KeyInfo>\n"+
+		"      <EncryptionMethod Algorithm=\"http://www.w3.org/2001/04/xmlenc#aes128-cbc\"></EncryptionMethod>\n"+
+		"      <EncryptionMethod Algorithm=\"http://www.w3.org/2001/04/xmlenc#aes192-cbc\"></EncryptionMethod>\n"+
+		"      <EncryptionMethod Algorithm=\"http://www.w3.org/2001/04/xmlenc#aes256-cbc\"></EncryptionMethod>\n"+
+		"      <EncryptionMethod Algorithm=\"http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p\"></EncryptionMethod>\n"+
 		"    </KeyDescriptor>\n"+
+		"    <SingleLogoutService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\" Location=\"https://example.com/saml2/slo\" ResponseLocation=\"https://example.com/saml2/slo\"></SingleLogoutService>\n"+
+		"    <AssertionConsumerService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\" Location=\"https://example.com/saml2/acs\" index=\"1\"></AssertionConsumerService>\n"+
+		"  </SPSSODescriptor>\n"+
+		"</EntityDescriptor>",
+		string(spMetadata))
+}
+
+func TestSPCanProduceMetadataWithBothCerts(t *testing.T) {
+	test := NewServiceProviderTest()
+	s := ServiceProvider{
+		Key:             test.Key,
+		Certificate:     test.Certificate,
+		MetadataURL:     mustParseURL("https://example.com/saml2/metadata"),
+		AcsURL:          mustParseURL("https://example.com/saml2/acs"),
+		SloURL:          mustParseURL("https://example.com/saml2/slo"),
+		IDPMetadata:     &EntityDescriptor{},
+		SignatureMethod: "not-empty",
+	}
+	err := xml.Unmarshal([]byte(test.IDPMetadata), &s.IDPMetadata)
+	assert.NoError(t, err)
+
+	spMetadata, err := xml.MarshalIndent(s.Metadata(), "", "  ")
+	assert.NoError(t, err)
+	assert.Equal(t, ""+
+		"<EntityDescriptor xmlns=\"urn:oasis:names:tc:SAML:2.0:metadata\" validUntil=\"2015-12-03T01:57:09Z\" entityID=\"https://example.com/saml2/metadata\">\n"+
+		"  <SPSSODescriptor xmlns=\"urn:oasis:names:tc:SAML:2.0:metadata\" validUntil=\"2015-12-03T01:57:09Z\" protocolSupportEnumeration=\"urn:oasis:names:tc:SAML:2.0:protocol\" AuthnRequestsSigned=\"true\" WantAssertionsSigned=\"true\">\n"+
 		"    <KeyDescriptor use=\"encryption\">\n"+
 		"      <KeyInfo xmlns=\"http://www.w3.org/2000/09/xmldsig#\">\n"+
 		"        <X509Data>\n"+
@@ -134,14 +164,21 @@ func TestSPCanProduceMetadata(t *testing.T) {
 		"      <EncryptionMethod Algorithm=\"http://www.w3.org/2001/04/xmlenc#aes256-cbc\"></EncryptionMethod>\n"+
 		"      <EncryptionMethod Algorithm=\"http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p\"></EncryptionMethod>\n"+
 		"    </KeyDescriptor>\n"+
+		"    <KeyDescriptor use=\"signing\">\n"+
+		"      <KeyInfo xmlns=\"http://www.w3.org/2000/09/xmldsig#\">\n"+
+		"        <X509Data>\n"+
+		"          <X509Certificate>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</X509Certificate>\n"+
+		"        </X509Data>\n"+
+		"      </KeyInfo>\n"+
+		"    </KeyDescriptor>\n"+
 		"    <SingleLogoutService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\" Location=\"https://example.com/saml2/slo\" ResponseLocation=\"https://example.com/saml2/slo\"></SingleLogoutService>\n"+
 		"    <AssertionConsumerService Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\" Location=\"https://example.com/saml2/acs\" index=\"1\"></AssertionConsumerService>\n"+
 		"  </SPSSODescriptor>\n"+
 		"</EntityDescriptor>",
 		string(spMetadata))
 }
 
-func TestCanProduceMetadataNoSigningKey(t *testing.T) {
+func TestCanProduceMetadataNoCerts(t *testing.T) {
 	test := NewServiceProviderTest()
 	s := ServiceProvider{
 		MetadataURL: mustParseURL("https://example.com/saml2/metadata"),
@@ -248,6 +285,62 @@ func TestSPCanProducePostRequest(t *testing.T) {
 		string(form))
 }
 
+func TestSPCanProduceSignedRequest(t *testing.T) {
+	test := NewServiceProviderTest()
+	TimeNow = func() time.Time {
+		rv, _ := time.Parse("Mon Jan 2 15:04:05.999999999 UTC 2006", "Mon Dec 1 01:31:21.123456789 UTC 2015")
+		return rv
+	}
+	Clock = dsig.NewFakeClockAt(TimeNow())
+	s := ServiceProvider{
+		Key:             test.Key,
+		Certificate:     test.Certificate,
+		MetadataURL:     mustParseURL("https://15661444.ngrok.io/saml2/metadata"),
+		AcsURL:          mustParseURL("https://15661444.ngrok.io/saml2/acs"),
+		IDPMetadata:     &EntityDescriptor{},
+		SignatureMethod: dsig.RSASHA1SignatureMethod,
+	}
+	err := xml.Unmarshal([]byte(test.IDPMetadata), &s.IDPMetadata)
+	assert.NoError(t, err)
+
+	redirectURL, err := s.MakeRedirectAuthenticationRequest("relayState")
+	assert.NoError(t, err)
+
+	decodedRequest, err := testsaml.ParseRedirectRequest(redirectURL)
+	assert.NoError(t, err)
+	assert.Equal(t,
+		"idp.testshib.org",
+		redirectURL.Host)
+	assert.Equal(t,
+		"/idp/profile/SAML2/Redirect/SSO",
+		redirectURL.Path)
+	assert.Equal(t,
+		"<samlp:AuthnRequest xmlns:saml=\"urn:oasis:names:tc:SAML:2.0:assertion\" xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\" ID=\"id-00020406080a0c0e10121416181a1c1e20222426\" Version=\"2.0\" IssueInstant=\"2015-12-01T01:31:21.123Z\" Destination=\"https://idp.testshib.org/idp/profile/SAML2/Redirect/SSO\" AssertionConsumerServiceURL=\"https://15661444.ngrok.io/saml2/acs\" ProtocolBinding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\"><saml:Issuer Format=\"urn:oasis:names:tc:SAML:2.0:nameid-format:entity\">https://15661444.ngrok.io/saml2/metadata</saml:Issuer><ds:Signature xmlns:ds=\"http://www.w3.org/2000/09/xmldsig#\"><ds:SignedInfo><ds:CanonicalizationMethod Algorithm=\"http://www.w3.org/2001/10/xml-exc-c14n#\"/><ds:SignatureMethod Algorithm=\"http://www.w3.org/2000/09/xmldsig#rsa-sha1\"/><ds:Reference URI=\"#id-00020406080a0c0e10121416181a1c1e20222426\"><ds:Transforms><ds:Transform Algorithm=\"http://www.w3.org/2000/09/xmldsig#enveloped-signature\"/><ds:Transform Algorithm=\"http://www.w3.org/2001/10/xml-exc-c14n#\"/></ds:Transforms><ds:DigestMethod Algorithm=\"http://www.w3.org/2000/09/xmldsig#sha1\"/><ds:DigestValue>XQ5+kdgOf34vpAemZRFalLlzjr0=</ds:DigestValue></ds:Reference></ds:SignedInfo><ds:SignatureValue>Wtomi/PiWx0bMFlImy5soCrrDbdY4BR2Qb8woGqc8KsVtXAwvl6lfYE2tuoT0YS5ipPLMMsFG8dB1TmLcA+0lnUcqfBiTiiHEwTIo3193RIsoH3STlOmXqBQf9Ax2nRdX+/4HwIYF58lgUzOb+nur+zGL6mYw2xjQBw6YGaX9Cc=</ds:SignatureValue><ds:KeyInfo><ds:X509Data><ds:X509Certificate>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</ds:X509Certificate></ds:X509Data></ds:KeyInfo></ds:Signature><samlp:NameIDPolicy Format=\"urn:oasis:names:tc:SAML:2.0:nameid-format:transient\" AllowCreate=\"true\"/></samlp:AuthnRequest>",
+		string(decodedRequest))
+}
+
+func TestSPFailToProduceSignedRequestWithBogusSignatureMethod(t *testing.T) {
+	test := NewServiceProviderTest()
+	TimeNow = func() time.Time {
+		rv, _ := time.Parse("Mon Jan 2 15:04:05.999999999 UTC 2006", "Mon Dec 1 01:31:21.123456789 UTC 2015")
+		return rv
+	}
+	Clock = dsig.NewFakeClockAt(TimeNow())
+	s := ServiceProvider{
+		Key:             test.Key,
+		Certificate:     test.Certificate,
+		MetadataURL:     mustParseURL("https://15661444.ngrok.io/saml2/metadata"),
+		AcsURL:          mustParseURL("https://15661444.ngrok.io/saml2/acs"),
+		IDPMetadata:     &EntityDescriptor{},
+		SignatureMethod: "bogus",
+	}
+	err := xml.Unmarshal([]byte(test.IDPMetadata), &s.IDPMetadata)
+	assert.NoError(t, err)
+
+	_, err = s.MakeRedirectAuthenticationRequest("relayState")
+	assert.Errorf(t, err, "invalid signing method bogus")
+}
+
 func TestSPCanProducePostLogoutRequest(t *testing.T) {
 	test := NewServiceProviderTest()
 	TimeNow = func() time.Time {