LDAP: Make LDAP attribute mapping case-insensitive (grafana#58992)

* Make LDAP attribute mapping case-insensitive

* Add test case with attribute name different from schema's

* Add fix to getArrayAttribute also and add test with mismatched letter
case.

* Update pkg/services/ldap/helpers.go

Co-authored-by: Misi <mgyongyosi@users.noreply.github.com>

Author: markkrj

pkg/services/ldap/helpers.go

@@ -34,7 +34,7 @@ func getAttribute(name string, entry *ldap.Entry) string {
 	}
 
 	for _, attr := range entry.Attributes {
-		if attr.Name == name {
+		if strings.EqualFold(attr.Name, name) {
 			if len(attr.Values) > 0 {
 				return attr.Values[0]
 			}
@@ -49,7 +49,7 @@ func getArrayAttribute(name string, entry *ldap.Entry) []string {
 	}
 
 	for _, attr := range entry.Attributes {
-		if attr.Name == name && len(attr.Values) > 0 {
+		if strings.EqualFold(attr.Name, name) && len(attr.Values) > 0 {
 			return attr.Values
 		}
 	}

pkg/services/ldap/ldap_helpers_test.go

@@ -83,6 +83,20 @@ func TestGetAttribute(t *testing.T) {
 		assert.Equal(t, value, result)
 	})
 
+	t.Run("letter case mismatch", func(t *testing.T) {
+		value := "roelgerrits"
+		entry := &ldap.Entry{
+			Attributes: []*ldap.EntryAttribute{
+				{
+					Name: "sAMAccountName", Values: []string{value},
+				},
+			},
+		}
+
+		result := getAttribute("samaccountname", entry)
+		assert.Equal(t, value, result)
+	})
+
 	t.Run("no result", func(t *testing.T) {
 		value := []string{"roelgerrits"}
 		entry := &ldap.Entry{
@@ -124,6 +138,21 @@ func TestGetArrayAttribute(t *testing.T) {
 		assert.EqualValues(t, value, result)
 	})
 
+	t.Run("letter case mismatch", func(t *testing.T) {
+		value := []string{"CN=Administrators,CN=Builtin,DC=grafana,DC=org"}
+		entry := &ldap.Entry{
+			Attributes: []*ldap.EntryAttribute{
+				{
+					Name: "memberOf", Values: value,
+				},
+			},
+		}
+
+		result := getArrayAttribute("memberof", entry)
+
+		assert.EqualValues(t, value, result)
+	})
+
 	t.Run("no result", func(t *testing.T) {
 		value := []string{"roelgerrits"}
 		entry := &ldap.Entry{