module rc4 // Copyright (c) 2019-2020 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. // Based off: https://github.com/golang/go/blob/master/src/crypto/rc4 // Last commit: https://github.com/golang/go/commit/b35dacaac57b039205d9b07ea24098e2c3fcb12e import crypto.internal.subtle // A Cipher is an instance of RC4 using a particular key. struct Cipher { mut: s []u32 i byte j byte } // 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{len: (256)} } for i in 0 .. 256 { c.s[i] = u32(i) } mut j := byte(0) for i in 0 .. 256 { j += byte(c.s[i]) + 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.good to com // // Deprecated: Reset can't guarantee that the key will be entirely removed from // the process's memory. pub fn (mut c Cipher) reset() { for i in c.s { c.s[i] = 0 } c.i = 0 c.j = 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 (mut c Cipher) xor_key_stream(mut dst []byte, mut src []byte) { if src.len == 0 { return } if subtle.inexact_overlap(dst, src) { panic('crypto.rc4: invalid buffer overlap') } mut i := c.i mut j := c.j for k, v in src { i += byte(1) x := c.s[i] j += byte(x) y := c.s[j] c.s[i] = y c.s[j] = x dst[k] = v ^ byte(c.s[byte(x + y)]) } c.i = i c.j = j }