Add SCRAM-SHA-256 (RFC 7804)

Implements HTTP SCRAM with SCRAM-SHA-256 per RFC 7804 and SCRAM mechanics per RFC 5802/7677.

Author: fitekonea

httpclient5/src/main/java/org/apache/hc/client5/http/auth/StandardAuthScheme.java

@@ -82,4 +82,12 @@ private StandardAuthScheme() {
     @Deprecated
     public static final String KERBEROS = "Kerberos";
 
+
+    /**
+     * SCRAM with SHA-256 as defined by RFC 7804 / RFC 7677.
+     *
+     * @since 5.6
+     */
+    public static final String SCRAM_SHA_256 = "SCRAM-SHA-256";
+
 }

httpclient5/src/main/java/org/apache/hc/client5/http/impl/DefaultAuthenticationStrategy.java

@@ -67,10 +67,11 @@ public class DefaultAuthenticationStrategy implements AuthenticationStrategy {
     public static final DefaultAuthenticationStrategy INSTANCE = new DefaultAuthenticationStrategy();
 
     private static final List<String> DEFAULT_SCHEME_PRIORITY =
-        Collections.unmodifiableList(Arrays.asList(
-                StandardAuthScheme.BEARER,
-                StandardAuthScheme.DIGEST,
-                StandardAuthScheme.BASIC));
+            Collections.unmodifiableList(Arrays.asList(
+                    StandardAuthScheme.BEARER,
+                    StandardAuthScheme.SCRAM_SHA_256,
+                    StandardAuthScheme.DIGEST,
+                    StandardAuthScheme.BASIC));
 
     protected List<String> getSchemePriority() {
         return DEFAULT_SCHEME_PRIORITY;

httpclient5/src/main/java/org/apache/hc/client5/http/impl/ScramException.java

@@ -0,0 +1,73 @@
+/*
+ * ====================================================================
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ * ====================================================================
+ *
+ * This software consists of voluntary contributions made by many
+ * individuals on behalf of the Apache Software Foundation.  For more
+ * information on the Apache Software Foundation, please see
+ * <http://www.apache.org/>.
+ *
+ */
+
+package org.apache.hc.client5.http.impl;
+
+import org.apache.hc.client5.http.auth.AuthenticationException;
+
+/**
+ * Represents an exception that occurs during SCRAM (Salted Challenge Response Authentication Mechanism) authentication.
+ * <p>
+ * SCRAM is a family of SASL mechanisms used for secure authentication. This exception is thrown when
+ * an error or issue is encountered during the SCRAM authentication process.
+ * </p>
+ *
+ * @since 5.6
+ */
+public class ScramException extends AuthenticationException {
+
+    private static final long serialVersionUID = 2491660491058647342L;
+
+    /**
+     * Constructs a new {@code ScramException} with {@code null} as its detail message.
+     * The cause is not initialized and may be subsequently initialized by a call to {@link #initCause}.
+     */
+    public ScramException() {
+        super();
+    }
+
+    /**
+     * Constructs a new {@code ScramException} with the specified detail message.
+     * The cause is not initialized and may be subsequently initialized by a call to {@link #initCause}.
+     *
+     * @param message the detail message, saved for later retrieval by the {@link #getMessage()} method.
+     */
+    public ScramException(final String message) {
+        super(message);
+    }
+
+    /**
+     * Constructs a new {@code ScramException} with the specified detail message and cause.
+     *
+     * @param message the detail message, saved for later retrieval by the {@link #getMessage()} method.
+     * @param cause   the cause, saved for later retrieval by the {@link #getCause()} method.
+     *                A {@code null} value indicates that the cause is nonexistent or unknown.
+     */
+    public ScramException(final String message, final Throwable cause) {
+        super(message, cause);
+    }
+}

httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/H2AsyncClientBuilder.java

@@ -60,6 +60,7 @@
 import org.apache.hc.client5.http.impl.auth.BasicSchemeFactory;
 import org.apache.hc.client5.http.impl.auth.BearerSchemeFactory;
 import org.apache.hc.client5.http.impl.auth.DigestSchemeFactory;
+import org.apache.hc.client5.http.impl.auth.ScramSchemeFactory;
 import org.apache.hc.client5.http.impl.auth.SystemDefaultCredentialsProvider;
 import org.apache.hc.client5.http.impl.nio.MultihomeConnectionInitiator;
 import org.apache.hc.client5.http.impl.routing.DefaultRoutePlanner;
@@ -898,6 +899,7 @@ public CloseableHttpAsyncClient build() {
                     .register(StandardAuthScheme.BASIC, BasicSchemeFactory.INSTANCE)
                     .register(StandardAuthScheme.DIGEST, DigestSchemeFactory.INSTANCE)
                     .register(StandardAuthScheme.BEARER, BearerSchemeFactory.INSTANCE)
+                    .register(StandardAuthScheme.SCRAM_SHA_256, ScramSchemeFactory.INSTANCE)
                     .build();
         }
         Lookup<CookieSpecFactory> cookieSpecRegistryCopy = this.cookieSpecRegistry;

httpclient5/src/main/java/org/apache/hc/client5/http/impl/async/HttpAsyncClientBuilder.java

@@ -69,6 +69,7 @@
 import org.apache.hc.client5.http.impl.auth.BasicSchemeFactory;
 import org.apache.hc.client5.http.impl.auth.BearerSchemeFactory;
 import org.apache.hc.client5.http.impl.auth.DigestSchemeFactory;
+import org.apache.hc.client5.http.impl.auth.ScramSchemeFactory;
 import org.apache.hc.client5.http.impl.auth.SystemDefaultCredentialsProvider;
 import org.apache.hc.client5.http.impl.nio.PoolingAsyncClientConnectionManagerBuilder;
 import org.apache.hc.client5.http.impl.routing.DefaultProxyRoutePlanner;
@@ -1172,6 +1173,7 @@ public CloseableHttpAsyncClient build() {
                     .register(StandardAuthScheme.BASIC, BasicSchemeFactory.INSTANCE)
                     .register(StandardAuthScheme.DIGEST, DigestSchemeFactory.INSTANCE)
                     .register(StandardAuthScheme.BEARER, BearerSchemeFactory.INSTANCE)
+                    .register(StandardAuthScheme.SCRAM_SHA_256, ScramSchemeFactory.INSTANCE)
                     .build();
         }
         Lookup<CookieSpecFactory> cookieSpecRegistryCopy = this.cookieSpecRegistry;