Prototype for CBA (#8475)

* Prototype for CBA

* Fixing gofmt issues

* Do not require password if logging in with certificate

* Fixing issues from feedback

* Adding unit tests

* Fixing feedback

app/login.go

@@ -6,6 +6,7 @@ package app
 import (
 	"fmt"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/avct/uasurfer"
@@ -13,6 +14,23 @@ import (
 	"github.com/mattermost/mattermost-server/store"
 )
 
+func (a *App) CheckForClienSideCert(r *http.Request) (string, string, string) {
+	pem := r.Header.Get("X-SSL-Client-Cert")                // mapped to $ssl_client_cert from nginx
+	subject := r.Header.Get("X-SSL-Client-Cert-Subject-DN") // mapped to $ssl_client_s_dn from nginx
+	email := ""
+
+	if len(subject) > 0 {
+		for _, v := range strings.Split(subject, "/") {
+			kv := strings.Split(v, "=")
+			if len(kv) == 2 && kv[0] == "emailAddress" {
+				email = kv[1]
+			}
+		}
+	}
+
+	return pem, subject, email
+}
+
 func (a *App) AuthenticateUserForLogin(id, loginId, password, mfaToken string, ldapOnly bool) (user *model.User, err *model.AppError) {
 	// Do statistics
 	defer func() {
@@ -35,6 +53,13 @@ func (a *App) AuthenticateUserForLogin(id, loginId, password, mfaToken string, l
 		return nil, err
 	}
 
+	// If client side cert is enable and it's checking as a primary source
+	// then trust the proxy and cert that the correct user is supplied and allow
+	// them access
+	if *a.Config().ExperimentalSettings.ClientSideCertEnable && *a.Config().ExperimentalSettings.ClientSideCertCheck == model.CLIENT_SIDE_CERT_CHECK_PRIMARY_AUTH {
+		return user, nil
+	}
+
 	// and then authenticate them
 	if user, err = a.authenticateUser(user, password, mfaToken); err != nil {
 		return nil, err

app/login_test.go

@@ -0,0 +1,37 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"net/http"
+	"testing"
+)
+
+func TestCheckForClienSideCert(t *testing.T) {
+	th := Setup()
+	defer th.TearDown()
+
+	var tests = []struct {
+		pem           string
+		subject       string
+		expectedEmail string
+	}{
+		{"blah", "blah", ""},
+		{"blah", "C=US, ST=Maryland, L=Pasadena, O=Brent Baccala, OU=FreeSoft, CN=www.freesoft.org/emailAddress=test@test.com", "test@test.com"},
+		{"blah", "C=US, ST=Maryland, L=Pasadena, O=Brent Baccala, OU=FreeSoft, CN=www.freesoft.org/EmailAddress=test@test.com", ""},
+		{"blah", "CN=www.freesoft.org/EmailAddress=test@test.com, C=US, ST=Maryland, L=Pasadena, O=Brent Baccala, OU=FreeSoft", ""},
+	}
+
+	for _, tt := range tests {
+		r := &http.Request{Header: http.Header{}}
+		r.Header.Add("X-SSL-Client-Cert", tt.pem)
+		r.Header.Add("X-SSL-Client-Cert-Subject-DN", tt.subject)
+
+		_, _, actualEmail := th.App.CheckForClienSideCert(r)
+
+		if actualEmail != tt.expectedEmail {
+			t.Fatalf("CheckForClienSideCert(%v): expected %v, actual %v", tt.subject, tt.expectedEmail, actualEmail)
+		}
+	}
+}