feat: HMAC support in Crypto APIs

doc/classes/HMACContext.xml

@@ -0,0 +1,88 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="HMACContext" inherits="Reference" version="4.0">
+	<brief_description>
+		Used to create an HMAC for a message using a key.
+	</brief_description>
+	<description>
+		The HMACContext class is useful for advanced HMAC use cases, such as streaming the message as it supports creating the message over time rather than providing it all at once.
+	[codeblocks]
+	[gdscript]
+	extends Node
+	var ctx = HMACContext.new()
+
+	func _ready():
+	    var key = "supersecret".to_utf8()
+	    var err = ctx.start(HashingContext.HASH_SHA256, key)
+	    assert(err == OK)
+	    var msg1 = "this is ".to_utf8()
+	    var msg2 = "vewy vewy secret".to_utf8()
+	    err = ctx.update(msg1)
+	    assert(err == OK)
+	    err = ctx.update(msg2)
+	    assert(err == OK)
+	    var hmac = ctx.finish()
+	    print(hmac.hex_encode())
+
+	[/gdscript]
+	[csharp]
+	using Godot;
+	using System;
+	using System.Diagnostics;
+
+	public class CryptoNode : Node
+	{
+	    private HMACContext ctx = new HMACContext();
+	    public override void _Ready()
+	    {
+	        PackedByteArray key = String("supersecret").to_utf8();
+	        Error err = ctx.Start(HashingContext.HASH_SHA256, key);
+	        GD.Assert(err == OK);
+	        PackedByteArray msg1 = String("this is ").to_utf8();
+	        PackedByteArray msg2 = String("vewy vew secret").to_utf8();
+	        err = ctx.Update(msg1);
+	        GD.Assert(err == OK);
+	        err = ctx.Update(msg2);
+	        GD.Assert(err == OK);
+	        PackedByteArray hmac = ctx.Finish();
+	        GD.Print(hmac.HexEncode());
+	    }
+	}
+
+	[/csharp]
+	[/codeblocks]
+	[b]Note:[/b] Not available in HTML5 exports.
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+		<method name="finish">
+			<return type="PackedByteArray">
+			</return>
+			<description>
+				Returns the resulting HMAC. If the HMAC failed, an empty [PackedByteArray] is returned.
+			</description>
+		</method>
+		<method name="start">
+			<return type="int" enum="Error">
+			</return>
+			<argument index="0" name="hash_type" type="int" enum="HashingContext.HashType">
+			</argument>
+			<argument index="1" name="key" type="PackedByteArray">
+			</argument>
+			<description>
+				Initializes the HMACContext. This method cannot be called again on the same HMACContext until [method finish] has been called.
+			</description>
+		</method>
+		<method name="update">
+			<return type="int" enum="Error">
+			</return>
+			<argument index="0" name="data" type="PackedByteArray">
+			</argument>
+			<description>
+				Updates the message to be HMACed. This can be called multiple times before [method finish] is called to append [code]data[/code] to the message, but cannot be called until [method start] has been called.
+			</description>
+		</method>
+	</methods>
+	<constants>
+	</constants>
+</class>