From 920ac3f92eb7cda73d2fc0a5b9d01d19dcdea553 Mon Sep 17 00:00:00 2001
From: joe-conigliaro <joe-conigliaro@users.noreply.github.com>
Date: Sat, 27 Jul 2019 00:48:49 +1000
Subject: [PATCH] crypto.rc4 module

---
 vlib/crypto/aes/aes.v      |  2 +
 vlib/crypto/rc4/rc4.v      | 83 ++++++++++++++++++++++++++++++++++++++
 vlib/crypto/rc4/rc4_test.v | 23 +++++++++++
 3 files changed, 108 insertions(+)
 create mode 100644 vlib/crypto/rc4/rc4.v
 create mode 100644 vlib/crypto/rc4/rc4_test.v

diff --git a/vlib/crypto/aes/aes.v b/vlib/crypto/aes/aes.v
index 04a6784317..91b8d9f171 100644
--- a/vlib/crypto/aes/aes.v
+++ b/vlib/crypto/aes/aes.v
@@ -2,6 +2,8 @@
 // Use of this source code is governed by an MIT license
 // that can be found in the LICENSE file.
 
+// Adapted from: https://github.com/golang/go/blob/master/src/crypto/aes
+
 module aes
 
 import (
diff --git a/vlib/crypto/rc4/rc4.v b/vlib/crypto/rc4/rc4.v
new file mode 100644
index 0000000000..bb5d83d0f0
--- /dev/null
+++ b/vlib/crypto/rc4/rc4.v
@@ -0,0 +1,83 @@
+// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+
+// Package rc4 implements RC4 encryption, as defined in Bruce Schneier's
+// Applied Cryptography.
+//
+// RC4 is cryptographically broken and should not be used for secure
+// applications.
+
+// Adapted from: https://github.com/golang/go/blob/master/src/crypto/rc4
+
+module rc4
+
+import crypto.internal.subtle
+
+// A Cipher is an instance of RC4 using a particular key.
+struct Cipher {
+mut:
+	s []u32
+	i u8
+	j u8
+}
+
+// new_cipher creates and returns a new Cipher. The key argument should be the
+// RC4 key, at least 1 byte and at most 256 bytes.
+pub fn new_cipher(key []byte) ?Cipher {
+	if key.len < 1 || key.len > 256 {
+		return error('crypto.rc4: invalid key size ' + key.len.str())
+	}
+	mut c := Cipher{
+		s: [u32(0); 256]
+	}
+	for i := 0; i < 256; i++ {
+		c.s[i] = u32(i)
+	}
+	mut j := u8(0)
+	for i := 0; i < 256; i++ {
+		j += u8(c.s[i]) + u8(key[i%key.len])
+		tmp := c.s[i]
+		c.s[i] = c.s[j]
+		c.s[j] = tmp
+	}
+	return c
+}
+
+// reset zeros the key data and makes the Cipher unusable.
+//
+// Deprecated: Reset can't guarantee that the key will be entirely removed from
+// the process's memory.
+pub fn (c &Cipher) reset() {
+	for i in c.s {
+		c.s[i] = u32(0)
+	}
+	c.i = u8(0)
+	c.j = u8(0)
+}
+
+// xor_key_stream sets dst to the result of XORing src with the key stream.
+// Dst and src must overlap entirely or not at all.
+pub fn (c &Cipher) xor_key_stream(dst, src []byte) {
+	if src.len == 0 {
+		return
+	}
+	if subtle.inexact_overlap(dst.left(src.len), src) {
+		panic('crypto.rc4: invalid buffer overlap')
+	}
+	mut i := c.i
+	mut j := c.j
+	_ := dst[src.len-1]
+	dst = dst.left(src.len) // eliminate bounds check from loop
+	for k, v in src {
+		i += u8(1)
+		x := c.s[i]
+		j += u8(x)
+		y := c.s[j]
+		c.s[i] = y
+		c.s[j] = x
+		dst[k] = v ^ byte(c.s[u8(x+y)])
+	}
+	c.i = i
+	c.j = j
+}
diff --git a/vlib/crypto/rc4/rc4_test.v b/vlib/crypto/rc4/rc4_test.v
new file mode 100644
index 0000000000..2c792fa46f
--- /dev/null
+++ b/vlib/crypto/rc4/rc4_test.v
@@ -0,0 +1,23 @@
+// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+
+import crypto.rc4
+
+fn test_crypto_rc4() {	 
+	key := 'tthisisourrc4key'.bytes()
+	
+	c := rc4.new_cipher(key) or {
+		println(err)
+		return
+	}
+	
+	mut src := 'toencrypt'.bytes()
+	
+	// src & dst same, encrypt in place
+	c.xor_key_stream(src, src) // encrypt data
+	
+	c.reset()
+
+	assert src.hex() == '189A39A91AEA8AFA65'
+}