add feature to search for groups of user

main.go

@@ -5,10 +5,12 @@ import (
 	"crypto/x509"
 	"encoding/json"
 	"encoding/pem"
+	"errors"
 	"flag"
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/go-ldap/ldap/v3"
 )
@@ -19,6 +21,7 @@ type Output struct {
 	Error       string
 	CertLoaded  bool
 	Results     string
+	Groups      string
 }
 
 func GetFilePath(path string) string {
@@ -52,6 +55,51 @@ func isFlagPassed(name string) bool {
 	return found
 }
 
+// GetGroupsOfUser returns the group for a user.
+// Taken from https://github.com/jtblin/go-ldap-client/issues/13#issuecomment-456090979
+func GetGroupsOfUser(username string, baseDN string, conn *ldap.Conn) ([]string, error) {
+
+	// Get the users DN
+	// Search for the given username
+	searchRequest := ldap.NewSearchRequest(
+		baseDN,
+		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
+		fmt.Sprintf("(uid=%s)", username),
+		[]string{"dn"},
+		nil,
+	)
+
+	sr, err := conn.Search(searchRequest)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(sr.Entries) != 1 {
+		return nil, errors.New("user does not exist")
+	}
+
+	userdn := sr.Entries[0].DN
+
+	searchRequest = ldap.NewSearchRequest(
+		baseDN,
+		ldap.ScopeWholeSubtree, ldap.NeverDerefAliases, 0, 0, false,
+		fmt.Sprintf("(memberUid=%s)", userdn),
+		[]string{"cn"}, // can it be something else than "cn"?
+		nil,
+	)
+	sr, err = conn.Search(searchRequest)
+	if err != nil {
+		return nil, err
+	}
+
+	groups := []string{}
+	for _, entry := range sr.Entries {
+		groups = append(groups, entry.GetAttributeValue("cn"))
+	}
+
+	return groups, nil
+}
+
 func main() {
 	var output Output
 
@@ -173,6 +221,15 @@ func main() {
 	} else {
 		output.AuthSuccess = true
 		output.Results = fmt.Sprintf("Search result count: %d; %s", len(result.Entries), result.Entries[0].DN)
+
+		// Since we have a successful connection, try getting group membership
+		groups, err := GetGroupsOfUser(*username, *baseDN, ldaps)
+		if err != nil {
+			output.Results = err.Error()
+		} else {
+			output.Groups = strings.Join(groups[:], ",")
+		}
+
 		b, _ := json.Marshal(output)
 		fmt.Println(string(b))
 		return