feat: support SAML and test with aliyun IDaaS (#346)

* feat: support SAML and test with aliyun IDaaS

Signed-off-by: Yixiang Zhao <seriouszyx@foxmail.com>

* refactor: refactor saml.go and router

Signed-off-by: Yixiang Zhao <seriouszyx@foxmail.com>

* fix: add param to getSamlLogin()

Signed-off-by: Yixiang Zhao <seriouszyx@foxmail.com>

* feat: add inputs to parse metadata automatically and show sp-acs-url, sp-entity-id

Signed-off-by: Yixiang Zhao <seriouszyx@foxmail.com>

object/saml.go

@@ -0,0 +1,99 @@
+// Copyright 2021 The casbin Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package object
+
+import (
+	"crypto/x509"
+	"encoding/base64"
+	"fmt"
+	"net/url"
+	"regexp"
+	"strings"
+
+	"github.com/astaxie/beego"
+	saml2 "github.com/russellhaering/gosaml2"
+	dsig "github.com/russellhaering/goxmldsig"
+)
+
+func ParseSamlResponse(samlResponse string) (string, error) {
+	samlResponse, _ = url.QueryUnescape(samlResponse)
+	sp, err := buildSp(nil, samlResponse)
+	if err != nil {
+		return "", err
+	}
+	assertionInfo, err := sp.RetrieveAssertionInfo(samlResponse)
+	if err != nil {
+		panic(err)
+	}
+	return assertionInfo.NameID, nil
+}
+
+func GenerateSamlLoginUrl(id string) (string, error) {
+	provider := GetProvider(id)
+	if provider.Category != "SAML" {
+		return "", fmt.Errorf("Provider %s's category is not SAML", provider.Name)
+	}
+	sp, err := buildSp(provider, "")
+	if err != nil {
+		return "", err
+	}
+	authURL, err := sp.BuildAuthURL("")
+	if err != nil {
+		return "", err
+	}
+	return authURL, nil
+}
+
+func buildSp(provider *Provider, samlResponse string) (*saml2.SAMLServiceProvider, error) {
+	certStore := dsig.MemoryX509CertificateStore{
+		Roots: []*x509.Certificate{},
+	}
+	samlOrigin := beego.AppConfig.String("samlOrigin")
+	certEncodedData := ""
+	if samlResponse != "" {
+		de, err := base64.StdEncoding.DecodeString(samlResponse)
+		if err != nil {
+			panic(err)
+		}
+		deStr := strings.Replace(string(de), "\n", "", -1)
+		res := regexp.MustCompile(`<ds:X509Certificate>(.*?)</ds:X509Certificate>`).FindAllStringSubmatch(deStr, -1)
+		str := res[0][0]
+		certEncodedData = str[20 : len(str)-21]
+	} else if provider != nil {
+		certEncodedData = provider.IdP
+	}
+	certData, err := base64.StdEncoding.DecodeString(certEncodedData)
+	if err != nil {
+		return nil, err
+	}
+	idpCert, err := x509.ParseCertificate(certData)
+	if err != nil {
+		return nil, err
+	}
+	certStore.Roots = append(certStore.Roots, idpCert)
+	sp := &saml2.SAMLServiceProvider{
+		ServiceProviderIssuer:       fmt.Sprintf("%s/api/acs", samlOrigin),
+		AssertionConsumerServiceURL: fmt.Sprintf("%s/api/acs", samlOrigin),
+		IDPCertificateStore:         &certStore,
+	}
+	if provider != nil {
+		randomKeyStore := dsig.RandomKeyStoreForTest()
+		sp.IdentityProviderSSOURL = provider.Endpoint
+		sp.IdentityProviderIssuer = provider.IssuerUrl
+		sp.SignAuthnRequests = false
+		sp.SPKeyStore = randomKeyStore
+	}
+	return sp, nil
+}