From d5925fd52258bfdaddd434e8c610cdcb0a16a0cd Mon Sep 17 00:00:00 2001
From: Jon Bonazza <jonbonazza@gmail.com>
Date: Sat, 14 Nov 2020 04:42:47 -0800
Subject: feat: HMAC support in Crypto APIs

---
 doc/classes/Crypto.xml      | 26 ++++++++++++++
 doc/classes/HMACContext.xml | 88 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 114 insertions(+)
 create mode 100644 doc/classes/HMACContext.xml

(limited to 'doc/classes')

diff --git a/doc/classes/Crypto.xml b/doc/classes/Crypto.xml
index b3bbbae94f..1f6cb40cde 100644
--- a/doc/classes/Crypto.xml
+++ b/doc/classes/Crypto.xml
@@ -73,6 +73,18 @@
 	<tutorials>
 	</tutorials>
 	<methods>
+		<method name="constant_time_compare">
+			<return type="bool">
+			</return>
+			<argument index="0" name="trusted" type="PackedByteArray">
+			</argument>
+			<argument index="1" name="received" type="PackedByteArray">
+			</argument>
+			<description>
+				Compares two [PackedByteArray]s for equality without leaking timing information in order to prevent timing attacks.
+				See [url=https://paragonie.com/blog/2015/11/preventing-timing-attacks-on-string-comparison-with-double-hmac-strategy]this blog post[/url] for more information.
+			</description>
+		</method>
 		<method name="decrypt">
 			<return type="PackedByteArray">
 			</return>
@@ -147,6 +159,20 @@
 				[/codeblocks]
 			</description>
 		</method>
+		<method name="hmac_digest">
+			<return type="PackedByteArray">
+			</return>
+			<argument index="0" name="hash_type" type="int" enum="HashingContext.HashType">
+			</argument>
+			<argument index="1" name="key" type="PackedByteArray">
+			</argument>
+			<argument index="2" name="msg" type="PackedByteArray">
+			</argument>
+			<description>
+				Generates an [url=https://en.wikipedia.org/wiki/HMAC]HMAC[/url] digest of [code]msg[/code] using [code]key[/code]. The [code]hash_type[/code] parameter is the hashing algorithm that is used for the inner and outer hashes.
+				Currently, only [constant HashingContext.HASH_SHA256] and [constant HashingContext.HASH_SHA1] are supported.
+			</description>
+		</method>
 		<method name="sign">
 			<return type="PackedByteArray">
 			</return>
diff --git a/doc/classes/HMACContext.xml b/doc/classes/HMACContext.xml
new file mode 100644
index 0000000000..00d528ef8f
--- /dev/null
+++ b/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>
-- 
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