From 58873ed3f90325cee5c442169d609d02c71fd05a Mon Sep 17 00:00:00 2001 From: Frank Denis Date: Wed, 30 Sep 2020 01:12:37 +0200 Subject: [PATCH] std/crypto: add GHASH implementation GHASH is required to implement AES-GCM. Optimized implementations for CPUs with instructions for carry-less multiplication will be added next. --- lib/std/crypto.zig | 1 + lib/std/crypto/benchmark.zig | 1 + lib/std/crypto/ghash.zig | 195 +++++++++++++++++++++++++++++++++++ 3 files changed, 197 insertions(+) create mode 100644 lib/std/crypto/ghash.zig diff --git a/lib/std/crypto.zig b/lib/std/crypto.zig index fa69d51d4d..5070305633 100644 --- a/lib/std/crypto.zig +++ b/lib/std/crypto.zig @@ -35,6 +35,7 @@ pub const aead = struct { /// MAC functions requiring single-use secret keys. pub const onetimeauth = struct { pub const Poly1305 = @import("crypto/poly1305.zig").Poly1305; + pub const Ghash = @import("crypto/ghash.zig").Ghash; }; /// A password hashing function derives a uniform key from low-entropy input material such as passwords. diff --git a/lib/std/crypto/benchmark.zig b/lib/std/crypto/benchmark.zig index 3c7e3445a2..d0ff29e896 100644 --- a/lib/std/crypto/benchmark.zig +++ b/lib/std/crypto/benchmark.zig @@ -57,6 +57,7 @@ pub fn benchmarkHash(comptime Hash: anytype, comptime bytes: comptime_int) !u64 } const macs = [_]Crypto{ + Crypto{ .ty = crypto.onetimeauth.Ghash, .name = "ghash" }, Crypto{ .ty = crypto.onetimeauth.Poly1305, .name = "poly1305" }, Crypto{ .ty = crypto.auth.hmac.HmacMd5, .name = "hmac-md5" }, Crypto{ .ty = crypto.auth.hmac.HmacSha1, .name = "hmac-sha1" }, diff --git a/lib/std/crypto/ghash.zig b/lib/std/crypto/ghash.zig new file mode 100644 index 0000000000..f05b5d7139 --- /dev/null +++ b/lib/std/crypto/ghash.zig @@ -0,0 +1,195 @@ +// SPDX-License-Identifier: MIT +// Copyright (c) 2015-2020 Zig Contributors +// This file is part of [zig](https://ziglang.org/), which is MIT licensed. +// The MIT license requires this copyright notice to be included in all copies +// and substantial portions of the software. +// +// Adapted from BearSSL's ctmul64 implementation originally written by Thomas Pornin + +const std = @import("../std.zig"); +const assert = std.debug.assert; +const math = std.math; +const mem = std.mem; + +/// GHASH is a universal hash function that features multiplication +/// by a fixed parameter within a Galois field. +/// +/// It is not a general purpose hash function - The key must be secret, unpredictable and never reused. +/// +/// GHASH is typically used to compute the authentication tag in the AES-GCM construction. +pub const Ghash = struct { + pub const block_size: usize = 16; + pub const mac_length = 16; + pub const minimum_key_length = 16; + + y0: u64 = 0, + y1: u64 = 0, + h0: u64, + h1: u64, + h2: u64, + h0r: u64, + h1r: u64, + h2r: u64, + + leftover: usize = 0, + buf: [block_size]u8 align(16) = undefined, + + pub fn init(key: []const u8) Ghash { + assert(key.len >= minimum_key_length); + const h1 = mem.readIntBig(u64, key[0..8]); + const h0 = mem.readIntBig(u64, key[8..16]); + const h1r = @bitReverse(u64, h1); + const h0r = @bitReverse(u64, h0); + const h2 = h0 ^ h1; + const h2r = h0r ^ h1r; + + return Ghash{ + .h0 = h0, + .h1 = h1, + .h2 = h2, + .h0r = h0r, + .h1r = h1r, + .h2r = h2r, + }; + } + + fn bmul(x: u64, y: u64) u64 { + const x0 = x & 0x1111111111111111; + const x1 = x & 0x2222222222222222; + const x2 = x & 0x4444444444444444; + const x3 = x & 0x8888888888888888; + const y0 = y & 0x1111111111111111; + const y1 = y & 0x2222222222222222; + const y2 = y & 0x4444444444444444; + const y3 = y & 0x8888888888888888; + var z0 = (x0 *% y0) ^ (x1 *% y3) ^ (x2 *% y2) ^ (x3 *% y1); + var z1 = (x0 *% y1) ^ (x1 *% y0) ^ (x2 *% y3) ^ (x3 *% y2); + var z2 = (x0 *% y2) ^ (x1 *% y1) ^ (x2 *% y0) ^ (x3 *% y3); + var z3 = (x0 *% y3) ^ (x1 *% y2) ^ (x2 *% y1) ^ (x3 *% y0); + z0 &= 0x1111111111111111; + z1 &= 0x2222222222222222; + z2 &= 0x4444444444444444; + z3 &= 0x8888888888888888; + + return z0 | z1 | z2 | z3; + } + + fn blocks(st: *Ghash, msg: []const u8) void { + assert(msg.len % 16 == 0); // GHASH blocks() expects full blocks + var y1 = st.y1; + var y0 = st.y0; + + var i: usize = 0; + while (i + 16 <= msg.len) : (i += 16) { + y1 ^= mem.readIntBig(u64, msg[i..][0..8]); + y0 ^= mem.readIntBig(u64, msg[i..][8..16]); + + const y1r = @bitReverse(u64, y1); + const y0r = @bitReverse(u64, y0); + const y2 = y0 ^ y1; + const y2r = y0r ^ y1r; + + const z0 = bmul(y0, st.h0); + const z1 = bmul(y1, st.h1); + var z2 = bmul(y2, st.h2); + var z0h = bmul(y0r, st.h0r); + var z1h = bmul(y1r, st.h1r); + var z2h = bmul(y2r, st.h2r); + z2 ^= z0 ^ z1; + z2h ^= z0h ^ z1h; + z0h = @bitReverse(u64, z0h) >> 1; + z1h = @bitReverse(u64, z1h) >> 1; + z2h = @bitReverse(u64, z2h) >> 1; + + var v3 = z1h; + var v2 = z1 ^ z2h; + var v1 = z0h ^ z2; + var v0 = z0; + + v3 = (v3 << 1) | (v2 >> 63); + v2 = (v2 << 1) | (v1 >> 63); + v1 = (v1 << 1) | (v0 >> 63); + v0 = (v0 << 1); + + v2 ^= v0 ^ (v0 >> 1) ^ (v0 >> 2) ^ (v0 >> 7); + v1 ^= (v0 << 63) ^ (v0 << 62) ^ (v0 << 57); + y1 = v3 ^ v1 ^ (v1 >> 1) ^ (v1 >> 2) ^ (v1 >> 7); + y0 = v2 ^ (v1 << 63) ^ (v1 << 62) ^ (v1 << 57); + } + st.y1 = y1; + st.y0 = y0; + } + + pub fn update(st: *Ghash, m: []const u8) void { + var mb = m; + + if (st.leftover > 0) { + const want = math.min(block_size - st.leftover, mb.len); + const mc = mb[0..want]; + for (mc) |x, i| { + st.buf[st.leftover + i] = x; + } + mb = mb[want..]; + st.leftover += want; + if (st.leftover > block_size) { + return; + } + st.blocks(&st.buf); + st.leftover = 0; + } + if (mb.len >= block_size) { + const want = mb.len & ~(block_size - 1); + st.blocks(mb[0..want]); + mb = mb[want..]; + } + if (mb.len > 0) { + for (mb) |x, i| { + st.buf[st.leftover + i] = x; + } + st.leftover += mb.len; + } + } + + pub fn final(st: *Ghash, out: []u8) void { + assert(out.len >= mac_length); + if (st.leftover > 0) { + var i = st.leftover; + while (i < block_size) : (i += 1) { + st.buf[i] = 0; + } + st.blocks(&st.buf); + } + mem.writeIntBig(u64, out[0..8], st.y1); + mem.writeIntBig(u64, out[8..16], st.y0); + + mem.secureZero(u8, @ptrCast([*]u8, st)[0..@sizeOf(Ghash)]); + } + + pub fn create(out: []u8, msg: []const u8, key: []const u8) void { + std.debug.assert(out.len >= mac_length); + std.debug.assert(key.len >= minimum_key_length); + + var st = Ghash.init(key); + st.update(msg); + st.final(out); + } +}; + +const htest = @import("test.zig"); + +test "ghash" { + const key = [_]u8{0x42} ** 16; + const m = [_]u8{0x69} ** 256; + + var st = Ghash.init(&key); + st.update(&m); + var out: [16]u8 = undefined; + st.final(&out); + htest.assertEqual("889295fa746e8b174bf4ec80a65dea41", &out); + + st = Ghash.init(&key); + st.update(m[0..100]); + st.update(m[100..]); + st.final(&out); + htest.assertEqual("889295fa746e8b174bf4ec80a65dea41", &out); +}