84 lines
1.9 KiB
Go
84 lines
1.9 KiB
Go
// 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
|
|
}
|