Implement query signature verification

service_provider.go

@@ -304,29 +304,24 @@
 	}
 
 	// We can't depend on Query().set() as order matters for signing
+	reqString := string(w.Bytes())
 	query := rv.RawQuery
 	if len(query) > 0 {
-		query += "&SAMLRequest=" + url.QueryEscape(requestStr.String())
+		query += "&" + string(samlRequest) + "=" + url.QueryEscape(requestStr.String())
 	} else {
-		query += "SAMLRequest=" + url.QueryEscape(requestStr.String())
+		query += string(samlRequest) + "=" + url.QueryEscape(requestStr.String())
 	}
 
 	if relayState != "" {
 		query += "&RelayState=" + relayState
 	}
 	if len(sp.SignatureMethod) > 0 {
-		query += "&SigAlg=" + url.QueryEscape(sp.SignatureMethod)
-		signingContext, err := GetSigningContext(sp)
-
-		if err != nil {
-			return nil, err
+		var errSig error
+		query, errSig = sp.signQuery(samlRequest, query, reqString, relayState)
+		if errSig != nil {
+			return nil, errSig
 		}
 
-		sig, err := signingContext.SignString(query)
-		if err != nil {
-			return nil, err
-		}
-		query += "&Signature=" + url.QueryEscape(base64.StdEncoding.EncodeToString(sig))
 	}
 
 	rv.RawQuery = query
@@ -1624,8 +1619,9 @@
 
 // ValidateLogoutResponseRequest validates the LogoutResponse content from the request
 func (sp *ServiceProvider) ValidateLogoutResponseRequest(req *http.Request) error {
-	if data := req.URL.Query().Get("SAMLResponse"); data != "" {
-		return sp.ValidateLogoutResponseRedirect(data)
+	query := req.URL.Query()
+	if data := query.Get("SAMLResponse"); data != "" {
+		return sp.ValidateLogoutResponseRedirect(query)
 	}
 
 	err := req.ParseForm()
@@ -1677,7 +1673,8 @@
 //
 // URL Binding appears to be gzip / flate encoded
 // See https://www.oasis-open.org/committees/download.php/20645/sstc-saml-tech-overview-2%200-draft-10.pdf  6.6
-func (sp *ServiceProvider) ValidateLogoutResponseRedirect(queryParameterData string) error {
+func (sp *ServiceProvider) ValidateLogoutResponseRedirect(query url.Values) error {
+	queryParameterData := query.Get("SAMLResponse")
 	retErr := &InvalidResponseError{
 		Now: TimeNow(),
 	}
@@ -1699,6 +1696,13 @@
 		return err
 	}
 
+	if query.Get("Signature") != "" && query.Get("SigAlg") != "" {
+		if err := sp.validateQuerySig(query); err != nil {
+			retErr.PrivateErr = err
+			return retErr
+		}
+	}
+
 	doc := etree.NewDocument()
 	if err := doc.ReadFromBytes(gr); err != nil {
 		retErr.PrivateErr = err

service_provider_signed.go

@@ -0,0 +1,141 @@
+package saml
+
+import (
+	"crypto"
+	"crypto/rsa"
+	"crypto/sha1" // #nosec G505
+	"crypto/sha256"
+	"crypto/sha512"
+	"crypto/x509"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net/url"
+
+	dsig "github.com/russellhaering/goxmldsig"
+)
+
+type reqType string
+
+const (
+	samlRequest  reqType = "SAMLRequest"
+	samlResponse reqType = "SAMLResponse"
+)
+
+var (
+	// ErrInvalidQuerySignature is returned when the query signature is invalid
+	ErrInvalidQuerySignature = errors.New("invalid query signature")
+	// ErrNoQuerySignature is returned when the query does not contain a signature
+	ErrNoQuerySignature = errors.New("query Signature or SigAlg not found")
+)
+
+// Sign Query with the SP private key.
+// Returns provided query with the SigAlg and Signature parameters added.
+func (sp *ServiceProvider) signQuery(reqT reqType, query, body, relayState string) (string, error) {
+	signingContext, err := GetSigningContext(sp)
+
+	// Encode Query as standard demands. query.Encode() is not standard compliant
+	toHash := string(reqT) + "=" + url.QueryEscape(body)
+	if relayState != "" {
+		toHash += "&RelayState=" + url.QueryEscape(relayState)
+	}
+
+	toHash += "&SigAlg=" + url.QueryEscape(sp.SignatureMethod)
+
+	if err != nil {
+		return "", err
+	}
+
+	sig, err := signingContext.SignString(toHash)
+	if err != nil {
+		return "", err
+	}
+
+	query += "&SigAlg=" + url.QueryEscape(sp.SignatureMethod)
+	query += "&Signature=" + url.QueryEscape(base64.StdEncoding.EncodeToString(sig))
+
+	return query, nil
+}
+
+// validateSig validation of the signature of the Redirect Binding in query values
+// Query is valid if return is nil
+func (sp *ServiceProvider) validateQuerySig(query url.Values) error {
+	sig := query.Get("Signature")
+	alg := query.Get("SigAlg")
+	if sig == "" || alg == "" {
+		return ErrNoQuerySignature
+	}
+
+	certs, err := sp.getIDPSigningCerts()
+	if err != nil {
+		return err
+	}
+
+	respType := ""
+	if query.Get("SAMLResponse") != "" {
+		respType = "SAMLResponse"
+	} else if query.Get("SAMLRequest") != "" {
+		respType = "SAMLRequest"
+	} else {
+		return fmt.Errorf("No SAMLResponse or SAMLRequest found in query")
+	}
+
+	// Encode Query as standard demands.
+	// query.Encode() is not standard compliant
+	// as query encoding order matters
+	res := respType + "=" + url.QueryEscape(query.Get(respType))
+
+	relayState := query.Get("RelayState")
+	if relayState != "" {
+		res += "&RelayState=" + url.QueryEscape(relayState)
+	}
+
+	res += "&SigAlg=" + url.QueryEscape(alg)
+
+	// Signature is base64 encoded
+	sigBytes, err := base64.StdEncoding.DecodeString(sig)
+	if err != nil {
+		return fmt.Errorf("failed to decode signature: %w", err)
+	}
+
+	var (
+		hashed  []byte
+		hashAlg crypto.Hash
+		sigAlg  x509.SignatureAlgorithm
+	)
+
+	// Hashed Query
+	switch alg {
+	case dsig.RSASHA256SignatureMethod:
+		hashed256 := sha256.Sum256([]byte(res))
+		hashed = hashed256[:]
+		hashAlg = crypto.SHA256
+		sigAlg = x509.SHA256WithRSA
+	case dsig.RSASHA512SignatureMethod:
+		hashed512 := sha512.Sum512([]byte(res))
+		hashed = hashed512[:]
+		hashAlg = crypto.SHA512
+		sigAlg = x509.SHA512WithRSA
+	case dsig.RSASHA1SignatureMethod:
+		hashed1 := sha1.Sum([]byte(res)) // #nosec G401
+		hashed = hashed1[:]
+		hashAlg = crypto.SHA1
+		sigAlg = x509.SHA1WithRSA
+	default:
+		return fmt.Errorf("unsupported signature algorithm: %s", alg)
+	}
+
+	// validate signature
+	for _, cert := range certs {
+		// verify cert is RSA
+		if cert.SignatureAlgorithm != sigAlg {
+			continue
+		}
+
+		if err := rsa.VerifyPKCS1v15(cert.PublicKey.(*rsa.PublicKey), hashAlg, hashed, sigBytes); err == nil {
+			return nil
+		}
+	}
+
+	return ErrInvalidQuerySignature
+}

service_provider_signed_test.go

@@ -0,0 +1,117 @@
+package saml
+
+import (
+	"crypto/rsa"
+	"encoding/base64"
+	"encoding/xml"
+	"net/url"
+	"testing"
+
+	dsig "github.com/russellhaering/goxmldsig"
+	"gotest.tools/assert"
+	"gotest.tools/golden"
+)
+
+// Given a SAMLRequest query string, sign the query and validate signature
+// Using same Cert for SP and IdP in order to test
+func TestSigningAndValidation(t *testing.T) {
+	type testCase struct {
+		desc         string
+		relayState   string
+		requestType  reqType
+		wantErr      bool
+		wantRawQuery string
+	}
+
+	testCases := []testCase{
+		{
+			desc:         "validate signature of SAMLRequest with relayState",
+			relayState:   "AAAAAAAAAAAA",
+			requestType:  samlRequest,
+			wantRawQuery: "SAMLRequest=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%2BPHNhbWw6SXNzdWVyIEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6ZW50aXR5Ij5odHRwczovL3NwLmV4YW1wbGUuY29tL3NhbWwyL21ldGFkYXRhPC9zYW1sOklzc3Vlcj48c2FtbHA6TmFtZUlEUG9saWN5IEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6dHJhbnNpZW50IiBBbGxvd0NyZWF0ZT0idHJ1ZSIvPjwvc2FtbHA6QXV0aG5SZXF1ZXN0Pg%3D%3D&RelayState=AAAAAAAAAAAA&SigAlg=http%3A%2F%2Fwww.w3.org%2F2000%2F09%2Fxmldsig%23rsa-sha1&Signature=zWAF4S%2FIs7tfmEriOsT5Fm8EFOGS3iCq6OxP5i7hM%2BMPwAoXwdDz6fKH8euS1gQ3sGOZBdHD588FZLvnO1OeCxLaEsxHMVKsAZSZFLBmPPwqB6e%2B84cCwX2szOeoMROaR%2B36mdoBDRQz36JIvyBBG%2FND9x41k%2FGQuAuwk%2B9fkuE%3D",
+		},
+		{
+			desc:         "validate signature of SAML request without relay state",
+			relayState:   "",
+			requestType:  samlRequest,
+			wantRawQuery: "SAMLRequest=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%2BPHNhbWw6SXNzdWVyIEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6ZW50aXR5Ij5odHRwczovL3NwLmV4YW1wbGUuY29tL3NhbWwyL21ldGFkYXRhPC9zYW1sOklzc3Vlcj48c2FtbHA6TmFtZUlEUG9saWN5IEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6dHJhbnNpZW50IiBBbGxvd0NyZWF0ZT0idHJ1ZSIvPjwvc2FtbHA6QXV0aG5SZXF1ZXN0Pg%3D%3D&SigAlg=http%3A%2F%2Fwww.w3.org%2F2000%2F09%2Fxmldsig%23rsa-sha1&Signature=HDdoHJSdkYh9%2BmE7RZ1LXcsAWIMJ6LuzKJgwLxH%2BQ4sKFlh8b5moFuQ%2B7rPEwoTcg9SjgCGV5rW9v8PrSU7WGKcLfAbeVwXWyU94ghjFZHEj%2BFCDpsfTD750ZPAPVnhVr0GogFZZ7c%2BEWX4NAqL4CYxDvsg56o%2BpOjw62G%2FyPDc%3D",
+		},
+		{
+			desc:         "validate signature of SAML response with relay state",
+			relayState:   "AAAAAAAAAAAA",
+			requestType:  samlResponse,
+			wantRawQuery: "SAMLResponse=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%2BPHNhbWw6SXNzdWVyIEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6ZW50aXR5Ij5odHRwczovL3NwLmV4YW1wbGUuY29tL3NhbWwyL21ldGFkYXRhPC9zYW1sOklzc3Vlcj48c2FtbHA6TmFtZUlEUG9saWN5IEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6dHJhbnNpZW50IiBBbGxvd0NyZWF0ZT0idHJ1ZSIvPjwvc2FtbHA6QXV0aG5SZXF1ZXN0Pg%3D%3D&RelayState=AAAAAAAAAAAA&SigAlg=http%3A%2F%2Fwww.w3.org%2F2000%2F09%2Fxmldsig%23rsa-sha1&Signature=JDeiWfLgV7SZqgqU64wgtAHS%2FqtF2c3c%2B9g1vdfRHn03tm5jrgsvJtIYg1BD8HoejCoyruH3xgDz1i2qqecVcUiAdaVgVvhn0JWJ%2BzeN9YpUFTEQ4Ah1pwezlSArzuz5esgYzSkemViox313HePWZ%2Fd0FAmtdXuGHA8O0Lp%2F4Ws%3D",
+		},
+	}
+
+	idpMetadata := golden.Get(t, "SP_IDPMetadata_signing")
+	s := ServiceProvider{
+		Key:             mustParsePrivateKey(golden.Get(t, "idp_key.pem")).(*rsa.PrivateKey),
+		Certificate:     mustParseCertificate(golden.Get(t, "idp_cert.pem")),
+		MetadataURL:     mustParseURL("https://15661444.ngrok.io/saml2/metadata"),
+		AcsURL:          mustParseURL("https://15661444.ngrok.io/saml2/acs"),
+		SignatureMethod: dsig.RSASHA1SignatureMethod,
+	}
+
+	err := xml.Unmarshal(idpMetadata, &s.IDPMetadata)
+	idpCert, err := s.getIDPSigningCerts()
+
+	assert.Check(t, err == nil)
+	assert.Check(t,
+		s.Certificate.Issuer.CommonName == idpCert[0].Issuer.CommonName, "expected %s, got %s",
+		s.Certificate.Issuer.CommonName, idpCert[0].Issuer.CommonName)
+
+	req := golden.Get(t, "idp_authn_request.xml")
+	reqString := base64.StdEncoding.EncodeToString(req)
+
+	for _, tc := range testCases {
+		t.Run(tc.desc, func(t *testing.T) {
+			relayState := tc.relayState
+
+			rawQuery := string(tc.requestType) + "=" + url.QueryEscape(reqString)
+
+			if relayState != "" {
+				rawQuery += "&RelayState=" + relayState
+			}
+
+			rawQuery, err = s.signQuery(tc.requestType, rawQuery, reqString, relayState)
+			assert.NilError(t, err, "error signing query: %s", err)
+
+			assert.Equal(t, tc.wantRawQuery, rawQuery)
+
+			query, err := url.ParseQuery(rawQuery)
+			assert.NilError(t, err, "error parsing query: %s", err)
+
+			err = s.validateQuerySig(query)
+			assert.NilError(t, err, "error validating query: %s", err)
+		})
+	}
+}
+
+// Given a raw query with an unsupported signature method, the signature should be rejected.
+func TestInvalidSignatureAlgorithm(t *testing.T) {
+	rawQuery := "SAMLRequest=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%2BPHNhbWw6SXNzdWVyIEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6ZW50aXR5Ij5odHRwczovL3NwLmV4YW1wbGUuY29tL3NhbWwyL21ldGFkYXRhPC9zYW1sOklzc3Vlcj48c2FtbHA6TmFtZUlEUG9saWN5IEZvcm1hdD0idXJuOm9hc2lzOm5hbWVzOnRjOlNBTUw6Mi4wOm5hbWVpZC1mb3JtYXQ6dHJhbnNpZW50IiBBbGxvd0NyZWF0ZT0idHJ1ZSIvPjwvc2FtbHA6QXV0aG5SZXF1ZXN0Pg%3D%3D&RelayState=AAAAAAAAAAAA&SigAlg=http%3A%2F%2Fwww.w3.org%2F2000%2F09%2Fxmldsig%23rsa-sha384&Signature=zWAF4S%2FIs7tfmEriOsT5Fm8EFOGS3iCq6OxP5i7hM%2BMPwAoXwdDz6fKH8euS1gQ3sGOZBdHD588FZLvnO1OeCxLaEsxHMVKsAZSZFLBmPPwqB6e%2B84cCwX2szOeoMROaR%2B36mdoBDRQz36JIvyBBG%2FND9x41k%2FGQuAuwk%2B9fkuE%3D"
+
+	idpMetadata := golden.Get(t, "SP_IDPMetadata_signing")
+	s := ServiceProvider{
+		Key:             mustParsePrivateKey(golden.Get(t, "idp_key.pem")).(*rsa.PrivateKey),
+		Certificate:     mustParseCertificate(golden.Get(t, "idp_cert.pem")),
+		MetadataURL:     mustParseURL("https://15661444.ngrok.io/saml2/metadata"),
+		AcsURL:          mustParseURL("https://15661444.ngrok.io/saml2/acs"),
+		SignatureMethod: dsig.RSASHA1SignatureMethod,
+	}
+
+	err := xml.Unmarshal(idpMetadata, &s.IDPMetadata)
+	idpCert, err := s.getIDPSigningCerts()
+
+	assert.Check(t, err == nil)
+	assert.Check(t,
+		s.Certificate.Issuer.CommonName == idpCert[0].Issuer.CommonName, "expected %s, got %s",
+		s.Certificate.Issuer.CommonName, idpCert[0].Issuer.CommonName)
+
+	query, err := url.ParseQuery(rawQuery)
+	assert.NilError(t, err, "error parsing query: %s", err)
+
+	err = s.validateQuerySig(query)
+	assert.Error(t, err, "unsupported signature algorithm: http://www.w3.org/2000/09/xmldsig#rsa-sha384")
+}