1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157

//! The Salsa20 stream cipher.
//!
//! Cipher functionality is accessed using traits from re-exported
//! [`stream-cipher`](https://docs.rs/stream-cipher) crate.
//!
//! # Security Warning
//!
//! This crate does not ensure ciphertexts are authentic! Thus ciphertext integrity
//! is not verified, which can lead to serious vulnerabilities!
//!
//! USE AT YOUR OWN RISK!
//!
//! # Diagram
//!
//! This diagram illustrates the Salsa quarter round function.
//! Each round consists of four quarter-rounds:
//!
//! <img src="https://raw.githubusercontent.com/RustCrypto/meta/master/img/stream-ciphers/salsa20.png" width="300px">
//!
//! Legend:
//!
//! - ⊞ add
//! - ‹‹‹ rotate
//! - ⊕ xor
//!
//! # Usage
//!
//! ```
//! use salsa20::{Salsa20, Key, Nonce};
//! use salsa20::stream_cipher::{NewStreamCipher, SyncStreamCipher, SyncStreamCipherSeek};
//!
//! let mut data = [1, 2, 3, 4, 5, 6, 7];
//!
//! let key = Key::from_slice(b"an example very very secret key.");
//! let nonce = Nonce::from_slice(b"a nonce.");
//!
//! // create cipher instance
//! let mut cipher = Salsa20::new(&key, &nonce);
//!
//! // apply keystream (encrypt)
//! cipher.apply_keystream(&mut data);
//! assert_eq!(data, [182, 14, 133, 113, 210, 25, 165]);
//!
//! // seek to the keystream beginning and apply it again to the `data` (decrypt)
//! cipher.seek(0);
//! cipher.apply_keystream(&mut data);
//! assert_eq!(data, [1, 2, 3, 4, 5, 6, 7]);
//! ```

#![no_std]
#![doc(
    html_logo_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg",
    html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/meta/master/logo.svg"
)]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![deny(unsafe_code)]
#![warn(missing_docs, rust_2018_idioms, trivial_casts, unused_qualifications)]

pub use stream_cipher;

mod block;
mod cipher;
mod rounds;
#[cfg(feature = "xsalsa20")]
mod xsalsa20;

#[cfg(feature = "xsalsa20")]
pub use self::xsalsa20::{XNonce, XSalsa20};

#[cfg(feature = "hsalsa20")]
pub use self::xsalsa20::hsalsa20;

use crate::{
    block::Block,
    cipher::Cipher,
    rounds::{Rounds, R12, R20, R8},
};
use core::convert::TryInto;
use stream_cipher::{
    consts::{U32, U8},
    LoopError, NewStreamCipher, OverflowError, SeekNum, SyncStreamCipher, SyncStreamCipherSeek,
};

/// Size of a Salsa20 block in bytes
pub const BLOCK_SIZE: usize = 64;

/// Size of a Salsa20 key in bytes
pub const KEY_SIZE: usize = 32;

/// Number of bytes in the Salsa20 IV
const IV_SIZE: usize = 8;

/// Number of 32-bit words in the Salsa20 state
const STATE_WORDS: usize = 16;

/// State initialization constant ("expand 32-byte k")
const CONSTANTS: [u32; 4] = [0x6170_7865, 0x3320_646e, 0x7962_2d32, 0x6b20_6574];

/// Salsa20/8 stream cipher
/// (reduced-round variant of Salsa20 with 8 rounds, *not recommended*)
pub type Salsa8 = Salsa<R8>;

/// Salsa20/12 stream cipher
/// (reduced-round variant of Salsa20 with 12 rounds, *not recommended*)
pub type Salsa12 = Salsa<R12>;

/// Salsa20/20 stream cipher
/// (20 rounds; **recommended**)
pub type Salsa20 = Salsa<R20>;

/// Key type.
///
/// Implemented as an alias for [`GenericArray`].
///
/// (NOTE: all three round variants use the same key size)
pub type Key = stream_cipher::Key<Salsa20>;

/// Nonce type.
///
/// Implemented as an alias for [`GenericArray`].
pub type Nonce = stream_cipher::Nonce<Salsa20>;

/// The Salsa20 family of stream ciphers
/// (implemented generically over a number of rounds).
///
/// We recommend you use the [`Salsa20`] (a.k.a. Salsa20/20) variant.
#[derive(Debug)]
pub struct Salsa<R: Rounds>(Cipher<R>);

impl<R: Rounds> NewStreamCipher for Salsa<R> {
    /// Key size in bytes
    type KeySize = U32;

    /// Nonce size in bytes
    type NonceSize = U8;

    fn new(key: &Key, nonce: &Nonce) -> Self {
        let block = Block::new(key.as_slice().try_into().unwrap(), (*nonce).into());
        Salsa(Cipher::new(block))
    }
}

impl<R: Rounds> SyncStreamCipherSeek for Salsa<R> {
    fn try_current_pos<T: SeekNum>(&self) -> Result<T, OverflowError> {
        self.0.try_current_pos()
    }

    fn try_seek<T: SeekNum>(&mut self, pos: T) -> Result<(), LoopError> {
        self.0.try_seek(pos)
    }
}

impl<R: Rounds> SyncStreamCipher for Salsa<R> {
    fn try_apply_keystream(&mut self, data: &mut [u8]) -> Result<(), LoopError> {
        self.0.try_apply_keystream(data)
    }
}