Add validation of keystore setting names (#27626)

This commit restricts settings added to the keystore to have a lowercase
ascii name. The java Keystore javadocs state that case sensitivity of
key alias names are implementation dependent. This ensures regardless of
case sensitivity in a jvm implementation, the keys will be stored as we
expect.

core/src/main/java/org/elasticsearch/common/settings/KeyStoreWrapper.java

@@ -49,6 +49,7 @@ import java.util.HashSet;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
 import org.apache.lucene.codecs.CodecUtil;
@@ -59,7 +60,6 @@ import org.apache.lucene.store.IndexInput;
 import org.apache.lucene.store.IndexOutput;
 import org.apache.lucene.store.SimpleFSDirectory;
 import org.apache.lucene.util.SetOnce;
-import org.elasticsearch.bootstrap.BootstrapSettings;
 import org.elasticsearch.cli.ExitCodes;
 import org.elasticsearch.cli.UserException;
 import org.elasticsearch.common.Randomness;
@@ -75,6 +75,11 @@ import org.elasticsearch.common.Randomness;
  */
 public class KeyStoreWrapper implements SecureSettings {
 
+    /**
+     * A regex for the valid characters that a setting name in the keystore may use.
+     */
+    private static final Pattern ALLOWED_SETTING_NAME = Pattern.compile("[a-z0-9_\\-.]+");
+
     public static final Setting<SecureString> SEED_SETTING = SecureSetting.secureString("keystore.seed", null);
 
     /** Characters that may be used in the bootstrap seed setting added to all keystores. */
@@ -383,6 +388,18 @@ public class KeyStoreWrapper implements SecureSettings {
         return Base64.getDecoder().wrap(bytesStream);
     }
 
+    /**
+     * Ensure the given setting name is allowed.
+     *
+     * @throws IllegalArgumentException if the setting name is not valid
+     */
+    public static void validateSettingName(String setting) {
+        if (ALLOWED_SETTING_NAME.matcher(setting).matches() == false) {
+            throw new IllegalArgumentException("Setting name [" + setting + "] does not match the allowed setting name pattern ["
+                + ALLOWED_SETTING_NAME.pattern() + "]");
+        }
+    }
+
     /**
      * Set a string setting.
      *
@@ -390,6 +407,7 @@ public class KeyStoreWrapper implements SecureSettings {
      */
     void setString(String setting, char[] value) throws GeneralSecurityException {
         assert isLoaded();
+        validateSettingName(setting);
         if (ASCII_ENCODER.canEncode(CharBuffer.wrap(value)) == false) {
             throw new IllegalArgumentException("Value must be ascii");
         }
@@ -401,6 +419,7 @@ public class KeyStoreWrapper implements SecureSettings {
     /** Set a file setting. */
     void setFile(String setting, byte[] bytes) throws GeneralSecurityException {
         assert isLoaded();
+        validateSettingName(setting);
         bytes = Base64.getEncoder().encode(bytes);
         char[] chars = new char[bytes.length];
         for (int i = 0; i < chars.length; ++i) {

core/src/main/java/org/elasticsearch/common/settings/SecureSetting.java

@@ -46,6 +46,7 @@ public abstract class SecureSetting<T> extends Setting<T> {
     private SecureSetting(String key, Property... properties) {
         super(key, (String)null, null, ArrayUtils.concat(properties, FIXED_PROPERTIES, Property.class));
         assert assertAllowedProperties(properties);
+        KeyStoreWrapper.validateSettingName(key);
     }
 
     private boolean assertAllowedProperties(Setting.Property... properties) {

core/src/test/java/org/elasticsearch/common/settings/KeyStoreWrapperTests.java

@@ -97,4 +97,14 @@ public class KeyStoreWrapperTests extends ESTestCase {
         keystore.decrypt(new char[0]);
         assertEquals(seed.toString(), keystore.getString(KeyStoreWrapper.SEED_SETTING.getKey()).toString());
     }
+
+    public void testIllegalSettingName() throws Exception {
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> KeyStoreWrapper.validateSettingName("UpperCase"));
+        assertTrue(e.getMessage().contains("does not match the allowed setting name pattern"));
+        KeyStoreWrapper keystore = KeyStoreWrapper.create(new char[0]);
+        e = expectThrows(IllegalArgumentException.class, () -> keystore.setString("UpperCase", new char[0]));
+        assertTrue(e.getMessage().contains("does not match the allowed setting name pattern"));
+        e = expectThrows(IllegalArgumentException.class, () -> keystore.setFile("UpperCase", new byte[0]));
+        assertTrue(e.getMessage().contains("does not match the allowed setting name pattern"));
+    }
 }

core/src/test/java/org/elasticsearch/common/settings/SettingsTests.java

@@ -486,6 +486,15 @@ public class SettingsTests extends ESTestCase {
         assertTrue(e.getMessage().contains("must be stored inside the Elasticsearch keystore"));
     }
 
+    public void testSecureSettingIllegalName() {
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () ->
+            SecureSetting.secureString("UpperCaseSetting", null));
+        assertTrue(e.getMessage().contains("does not match the allowed setting name pattern"));
+        e = expectThrows(IllegalArgumentException.class, () ->
+            SecureSetting.secureFile("UpperCaseSetting", null));
+        assertTrue(e.getMessage().contains("does not match the allowed setting name pattern"));
+    }
+
     public void testGetAsArrayFailsOnDuplicates() {
         final IllegalStateException e = expectThrows(IllegalStateException.class, () -> Settings.builder()
             .put("foobar.0", "bar")