gistfile1.txt

// Based on public domain Supercop by Daniel J. Bernstein

const mem = @import("../mem.zig");
const endian = @import("../endian.zig");
const builtin = @import("builtin");

const QuarterRound = struct {
    a: usize,
    b: usize,
    c: usize,
    d: usize,
};

fn Rp(a: usize, b: usize, c: usize, d: usize) QuarterRound {
    return QuarterRound{
        .a = a,
        .b = b,
        .c = c,
        .d = d,
    };
}

fn rotate(a: u32, b: u5) u32 {
    return ((a << b) |
            (a >> @intCast(u5, (32 - @intCast(u6, b))))
           );
}

fn salsa20_wordtobyte(input: [16]u32) [64]u8 {
    var x: [16]u32 = undefined;
    var out: [64]u8 = undefined;

    for (x) |_, i|
        x[i] = input[i];
    const rounds = comptime []QuarterRound{
        Rp( 0, 4, 8,12),
        Rp( 1, 5, 9,13),
        Rp( 2, 6,10,14),
        Rp( 3, 7,11,15),
        Rp( 0, 5,10,15),
        Rp( 1, 6,11,12),
        Rp( 2, 7, 8,13),
        Rp( 3, 4, 9,14),
    };
    comptime var j: usize = 20;
    inline while (j > 0) : (j -=2) {
        for (rounds) |r| {
            x[r.a] +%= x[r.b]; x[r.d] = rotate(x[r.d] ^ x[r.a], 16);
            x[r.c] +%= x[r.d]; x[r.b] = rotate(x[r.b] ^ x[r.c], 12);
            x[r.a] +%= x[r.b]; x[r.d] = rotate(x[r.d] ^ x[r.a],  8);
            x[r.c] +%= x[r.d]; x[r.b] = rotate(x[r.b] ^ x[r.c],  7);
        }
    }
    for (x) |_, i|
        x[i] +%= input[i];
    for (x) |_, i|
        mem.writeInt(out[4 * i .. 4 * i + 4], x[i], builtin.Endian.Little);
    return out;
}

pub fn chaCha20(in: []const u8, key: [32]u8, nonce: [8]u8, out: []u8) void {
    var ctx: [16]u32 = undefined;
    var remaining: usize = undefined;
    var cursor: usize = 0;

    if (in.len > out.*.len) {
        remaining = out.len;
    } else
        remaining = in.len;

    comptime const c = "expand 32-byte k";
    comptime const constant_le = []u32{
        comptime mem.readIntLE(u32, c[0..4]),
        comptime mem.readIntLE(u32, c[4..8]),
        comptime mem.readIntLE(u32, c[8..12]),
        comptime mem.readIntLE(u32, c[12..16]),
    };
    
    for (constant_le) |_, i|
        ctx[i] = constant_le[i];

    ctx[4] = mem.readIntLE(u32, key[0..4]);
    ctx[5] = mem.readIntLE(u32, key[4..8]);
    ctx[6] = mem.readIntLE(u32, key[8..12]);
    ctx[7] = mem.readIntLE(u32, key[12..16]);
    ctx[8] = mem.readIntLE(u32, key[16..20]);
    ctx[9] = mem.readIntLE(u32, key[20..24]);
    ctx[10] = mem.readIntLE(u32, key[24..28]);
    ctx[11] = mem.readIntLE(u32, key[28..32]);

    ctx[12] = 0;
    ctx[13] = 0;
    ctx[14] = mem.readIntLE(u32, nonce[0..4]);
    ctx[15] = mem.readIntLE(u32, nonce[4..8]);

    while (true) {
        var buf = salsa20_wordtobyte(ctx);
        var count: u64 = undefined;

        if (remaining < 64) {
            var i: usize = 0;
            while (i < remaining) : (i += 1)
                out.*[cursor + i] = in[cursor + i] ^ buf[i];
            return;
        }

        comptime var i: usize = 0;
        inline while (i < 64) : (i += 1)
            out.*[cursor + i] = in[cursor + i] ^ buf[i];

        cursor += 64;
        remaining -= 64;

        count = @intCast(u64, ctx[12]) | @intCast(u64, ctx[13]) << 32;
        count += 1;
        ctx[12] = @intCast(u32, count & @maxValue(u32));
        ctx[13] = @intCast(u32, count >> 32);
    }
}

// https://tools.ietf.org/html/draft-agl-tls-chacha20poly1305-04#section-7
test "crypto.chacha20 test vector 1" {
    const assert = @import("std").debug.assert;

    const expected_result = []u8{
        0x76, 0xb8, 0xe0, 0xad, 0xa0, 0xf1, 0x3d, 0x90,
        0x40, 0x5d, 0x6a, 0xe5, 0x53, 0x86, 0xbd, 0x28,
        0xbd, 0xd2, 0x19, 0xb8, 0xa0, 0x8d, 0xed, 0x1a,
        0xa8, 0x36, 0xef, 0xcc, 0x8b, 0x77, 0x0d, 0xc7,
        0xda, 0x41, 0x59, 0x7c, 0x51, 0x57, 0x48, 0x8d,
        0x77, 0x24, 0xe0, 0x3f, 0xb8, 0xd8, 0x4a, 0x37,
        0x6a, 0x43, 0xb8, 0xf4, 0x15, 0x18, 0xa1, 0x1c,
        0xc3, 0x87, 0xb6, 0x69, 0xb2, 0xee, 0x65, 0x86,
    };
    const input = []u8{
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    };
    var result: [64]u8 = undefined;
    const key = []u8{
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
    };
    const nonce = []u8{0, 0, 0, 0, 0, 0, 0, 0};

    chaCha20(input[0..], key, nonce, result[0..]);
    assert(mem.compare(u8, expected_result, result) == mem.Compare.Equal);
}

test "crypto.chacha20 test vector 2" {
    const assert = @import("std").debug.assert;

    const expected_result = []u8{
        0x45, 0x40, 0xf0, 0x5a, 0x9f, 0x1f, 0xb2, 0x96,
        0xd7, 0x73, 0x6e, 0x7b, 0x20, 0x8e, 0x3c, 0x96,
        0xeb, 0x4f, 0xe1, 0x83, 0x46, 0x88, 0xd2, 0x60,
        0x4f, 0x45, 0x09, 0x52, 0xed, 0x43, 0x2d, 0x41,
        0xbb, 0xe2, 0xa0, 0xb6, 0xea, 0x75, 0x66, 0xd2,
        0xa5, 0xd1, 0xe7, 0xe2, 0x0d, 0x42, 0xaf, 0x2c,
        0x53, 0xd7, 0x92, 0xb1, 0xc4, 0x3f, 0xea, 0x81,
        0x7e, 0x9a, 0xd2, 0x75, 0xae, 0x54, 0x69, 0x63,
    };
    const input = []u8{
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    };
    var result: [64]u8 = undefined;
    const key = []u8{
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 1,
    };
    const nonce = []u8{0, 0, 0, 0, 0, 0, 0, 0};

    chaCha20(input[0..], key, nonce, result[0..]);
    assert(mem.compare(u8, expected_result, result) == mem.Compare.Equal);
}

test "crypto.chacha20 test vector 3" {
    const assert = @import("std").debug.assert;

    const expected_result = []u8{
        0xde, 0x9c, 0xba, 0x7b, 0xf3, 0xd6, 0x9e, 0xf5,
        0xe7, 0x86, 0xdc, 0x63, 0x97, 0x3f, 0x65, 0x3a,
        0x0b, 0x49, 0xe0, 0x15, 0xad, 0xbf, 0xf7, 0x13,
        0x4f, 0xcb, 0x7d, 0xf1, 0x37, 0x82, 0x10, 0x31,
        0xe8, 0x5a, 0x05, 0x02, 0x78, 0xa7, 0x08, 0x45,
        0x27, 0x21, 0x4f, 0x73, 0xef, 0xc7, 0xfa, 0x5b,
        0x52, 0x77, 0x06, 0x2e, 0xb7, 0xa0, 0x43, 0x3e,
        0x44, 0x5f, 0x41, 0xe3,
    };
    const input = []u8{
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    };
    var result: [60]u8 = undefined;
    const key = []u8{
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
    };
    const nonce = []u8{0, 0, 0, 0, 0, 0, 0, 1};

    chaCha20(input[0..], key, nonce, result[0..]);
    assert(mem.compare(u8, expected_result, result) == mem.Compare.Equal);
}

test "crypto.chacha20 test vector 4" {
    const assert = @import("std").debug.assert;

    const expected_result = []u8{
        0xef, 0x3f, 0xdf, 0xd6, 0xc6, 0x15, 0x78, 0xfb,
        0xf5, 0xcf, 0x35, 0xbd, 0x3d, 0xd3, 0x3b, 0x80,
        0x09, 0x63, 0x16, 0x34, 0xd2, 0x1e, 0x42, 0xac,
        0x33, 0x96, 0x0b, 0xd1, 0x38, 0xe5, 0x0d, 0x32,
        0x11, 0x1e, 0x4c, 0xaf, 0x23, 0x7e, 0xe5, 0x3c,
        0xa8, 0xad, 0x64, 0x26, 0x19, 0x4a, 0x88, 0x54,
        0x5d, 0xdc, 0x49, 0x7a, 0x0b, 0x46, 0x6e, 0x7d,
        0x6b, 0xbd, 0xb0, 0x04, 0x1b, 0x2f, 0x58, 0x6b,
    };
    const input = []u8{
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    };
    var result: [64]u8 = undefined;
    const key = []u8{
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0,
    };
    const nonce = []u8{1, 0, 0, 0, 0, 0, 0, 0};

    chaCha20(input[0..], key, nonce, result[0..]);
    assert(mem.compare(u8, expected_result, result) == mem.Compare.Equal);
}

test "crypto.chacha20 test vector 5" {
    const assert = @import("std").debug.assert;

    const expected_result = []u8{
        0xf7, 0x98, 0xa1, 0x89, 0xf1, 0x95, 0xe6, 0x69,
        0x82, 0x10, 0x5f, 0xfb, 0x64, 0x0b, 0xb7, 0x75,
        0x7f, 0x57, 0x9d, 0xa3, 0x16, 0x02, 0xfc, 0x93,
        0xec, 0x01, 0xac, 0x56, 0xf8, 0x5a, 0xc3, 0xc1,
        0x34, 0xa4, 0x54, 0x7b, 0x73, 0x3b, 0x46, 0x41,
        0x30, 0x42, 0xc9, 0x44, 0x00, 0x49, 0x17, 0x69,
        0x05, 0xd3, 0xbe, 0x59, 0xea, 0x1c, 0x53, 0xf1,
        0x59, 0x16, 0x15, 0x5c, 0x2b, 0xe8, 0x24, 0x1a,

        0x38, 0x00, 0x8b, 0x9a, 0x26, 0xbc, 0x35, 0x94,
        0x1e, 0x24, 0x44, 0x17, 0x7c, 0x8a, 0xde, 0x66,
        0x89, 0xde, 0x95, 0x26, 0x49, 0x86, 0xd9, 0x58,
        0x89, 0xfb, 0x60, 0xe8, 0x46, 0x29, 0xc9, 0xbd,
        0x9a, 0x5a, 0xcb, 0x1c, 0xc1, 0x18, 0xbe, 0x56,
        0x3e, 0xb9, 0xb3, 0xa4, 0xa4, 0x72, 0xf8, 0x2e,
        0x09, 0xa7, 0xe7, 0x78, 0x49, 0x2b, 0x56, 0x2e,
        0xf7, 0x13, 0x0e, 0x88, 0xdf, 0xe0, 0x31, 0xc7,

        0x9d, 0xb9, 0xd4, 0xf7, 0xc7, 0xa8, 0x99, 0x15,
        0x1b, 0x9a, 0x47, 0x50, 0x32, 0xb6, 0x3f, 0xc3,
        0x85, 0x24, 0x5f, 0xe0, 0x54, 0xe3, 0xdd, 0x5a,
        0x97, 0xa5, 0xf5, 0x76, 0xfe, 0x06, 0x40, 0x25,
        0xd3, 0xce, 0x04, 0x2c, 0x56, 0x6a, 0xb2, 0xc5,
        0x07, 0xb1, 0x38, 0xdb, 0x85, 0x3e, 0x3d, 0x69,
        0x59, 0x66, 0x09, 0x96, 0x54, 0x6c, 0xc9, 0xc4,
        0xa6, 0xea, 0xfd, 0xc7, 0x77, 0xc0, 0x40, 0xd7,

        0x0e, 0xaf, 0x46, 0xf7, 0x6d, 0xad, 0x39, 0x79,
        0xe5, 0xc5, 0x36, 0x0c, 0x33, 0x17, 0x16, 0x6a,
        0x1c, 0x89, 0x4c, 0x94, 0xa3, 0x71, 0x87, 0x6a,
        0x94, 0xdf, 0x76, 0x28, 0xfe, 0x4e, 0xaa, 0xf2,
        0xcc, 0xb2, 0x7d, 0x5a, 0xaa, 0xe0, 0xad, 0x7a,
        0xd0, 0xf9, 0xd4, 0xb6, 0xad, 0x3b, 0x54, 0x09,
        0x87, 0x46, 0xd4, 0x52, 0x4d, 0x38, 0x40, 0x7a,
        0x6d, 0xeb, 0x3a, 0xb7, 0x8f, 0xab, 0x78, 0xc9,
    };
    const input = []u8{
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,

        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    };
    var result: [256]u8 = undefined;
    const key = []u8{
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
        0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
        0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
        0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
    };
    const nonce = []u8{
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
    };

    chaCha20(input[0..], key, nonce, result[0..]);
    assert(mem.compare(u8, expected_result, result) == mem.Compare.Equal);
}