fix a parsing mistake in ActiveDirectory code

Signed-off-by: Ryan Richard <richardry@vmware.com>

internal/controller/supervisorconfig/activedirectoryupstreamwatcher/active_directory_upstream_watcher.go

@@ -1,4 +1,4 @@
-// Copyright 2021-2024 the Pinniped contributors. All Rights Reserved.
+// Copyright 2021-2026 the Pinniped contributors. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
 // Package activedirectoryupstreamwatcher implements a controller which watches ActiveDirectoryIdentityProviders.
@@ -8,7 +8,6 @@ import (
 	"context"
 	"encoding/base64"
 	"fmt"
-	"regexp"
 	"strconv"
 	"strings"
 
@@ -454,14 +453,29 @@ func groupSAMAccountNameWithDomainSuffix(entry *ldap.Entry) (string, error) {
 	return sAMAccountName + "@" + domain, nil
 }
 
-var domainComponentsRegexp = regexp.MustCompile(",DC=|,dc=")
-
 func getDomainFromDistinguishedName(distinguishedName string) (string, error) {
-	domainComponents := domainComponentsRegexp.Split(distinguishedName, -1)
-	if len(domainComponents) == 1 {
-		return "", fmt.Errorf("did not find domain components in group dn: %s", distinguishedName)
+	parsedDN, err := ldap.ParseDN(distinguishedName)
+	if err != nil {
+		return "", fmt.Errorf("could not parse DN %q: %w", distinguishedName, err)
 	}
-	return strings.Join(domainComponents[1:], "."), nil
+
+	var dcValues []string
+	// Iterate through the Relative Distinguished Names (RDNs)
+	for _, rdn := range parsedDN.RDNs {
+		// Each RDN can contain multiple attribute-value pairs (usually just one)
+		for _, attr := range rdn.Attributes {
+			// Compare case-insensitively since LDAP attributes are case-insensitive
+			if strings.EqualFold(attr.Type, "dc") {
+				dcValues = append(dcValues, attr.Value)
+			}
+		}
+	}
+
+	if len(dcValues) == 0 {
+		return "", fmt.Errorf("did not find domain components in group DN %q", distinguishedName)
+	}
+
+	return strings.Join(dcValues, "."), nil
 }
 
 //nolint:gochecknoglobals // this needs to be a global variable so that tests can check pointer equality

internal/controller/supervisorconfig/activedirectoryupstreamwatcher/active_directory_upstream_watcher_test.go

@@ -2481,14 +2481,35 @@ func TestGroupSAMAccountNameWithDomainSuffix(t *testing.T) {
 			wantResult: "Mammals@mycompany.example.com",
 		},
 		{
-			name: "no domain components in DN",
+			name: "unusual CN with DN and valid sAMAccountName",
 			entry: &ldap.Entry{
-				DN: "no-domain-components",
+				// A backslash within a CN escapes the next character, so we want to ignore the letters "DC=" there.
+				DN: `CN=animals\,DC=should-be-ignored-because-it-is-part-of-cn,OU=Users,OU=pinniped-ad,DC=mycompany,DC=example,DC=com`,
 				Attributes: []*ldap.EntryAttribute{
 					ldap.NewEntryAttribute("sAMAccountName", []string{"Mammals"}),
 				},
 			},
-			wantErr: "did not find domain components in group dn: no-domain-components",
+			wantResult: "Mammals@mycompany.example.com",
+		},
+		{
+			name: "invalid DN",
+			entry: &ldap.Entry{
+				DN: "invalid-dn",
+				Attributes: []*ldap.EntryAttribute{
+					ldap.NewEntryAttribute("sAMAccountName", []string{"Mammals"}),
+				},
+			},
+			wantErr: `could not parse DN "invalid-dn": DN ended with incomplete type, value pair`,
+		},
+		{
+			name: "no domain components in DN",
+			entry: &ldap.Entry{
+				DN: "CN=foo",
+				Attributes: []*ldap.EntryAttribute{
+					ldap.NewEntryAttribute("sAMAccountName", []string{"Mammals"}),
+				},
+			},
+			wantErr: `did not find domain components in group DN "CN=foo"`,
 		},
 		{
 			name: "multiple values for sAMAccountName attribute",
@@ -2576,9 +2597,19 @@ func TestGetDomainFromDistinguishedName(t *testing.T) {
 			wantDomain:        "activedirectory.mycompany.example.com",
 		},
 		{
-			name:              "no domain components",
+			name:              "unusual CN",
+			distinguishedName: `CN=animals\,DC=should-be-ignored-because-it-is-part-of-cn,OU=Users,OU=pinniped-ad,dc=activedirectory,DC=mycompany,DC=example,DC=com`,
+			wantDomain:        "activedirectory.mycompany.example.com",
+		},
+		{
+			name:              "invalid DN",
 			distinguishedName: "not-a-dn",
-			wantErr:           "did not find domain components in group dn: not-a-dn",
+			wantErr:           `could not parse DN "not-a-dn": DN ended with incomplete type, value pair`,
+		},
+		{
+			name:              "no domain components",
+			distinguishedName: "CN=foo",
+			wantErr:           `did not find domain components in group DN "CN=foo"`,
 		},
 	}