monocypher-ed25519.c

// Monocypher version __git__
//
// This file is dual-licensed.  Choose whichever licence you want from
// the two licences listed below.
//
// The first licence is a regular 2-clause BSD licence.  The second licence
// is the CC-0 from Creative Commons. It is intended to release Monocypher
// to the public domain.  The BSD licence serves as a fallback option.
//
// SPDX-License-Identifier: BSD-2-Clause OR CC0-1.0
//
// ------------------------------------------------------------------------
//
// Copyright (c) 2017-2019, Loup Vaillant
// All rights reserved.
//
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the
//    distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// ------------------------------------------------------------------------
//
// Written in 2017-2019 by Loup Vaillant
//
// To the extent possible under law, the author(s) have dedicated all copyright
// and related neighboring rights to this software to the public domain
// worldwide.  This software is distributed without any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication along
// with this software.  If not, see
// <https://creativecommons.org/publicdomain/zero/1.0/>

#include "monocypher-ed25519.h"

/////////////////
/// Utilities ///
/////////////////
#define FOR(i, min, max)     for (size_t i = min; i < max; i++)
#define COPY(dst, src, size) FOR(i, 0, size) (dst)[i] = (src)[i]
#define ZERO(buf, size)      FOR(i, 0, size) (buf)[i] = 0
#define WIPE_CTX(ctx)        crypto_wipe(ctx   , sizeof(*(ctx)))
#define WIPE_BUFFER(buffer)  crypto_wipe(buffer, sizeof(buffer))
#define MIN(a, b)            ((a) <= (b) ? (a) : (b))
typedef uint8_t u8;
typedef uint64_t u64;

// returns the smallest positive integer y such that
// (x + y) % pow_2  == 0
// Basically, it's how many bytes we need to add to "align" x.
// Only works when pow_2 is a power of 2.
// Note: we use ~x+1 instead of -x to avoid compiler warnings
static size_t align(size_t x, size_t pow_2)
{
    return (~x + 1) & (pow_2 - 1);
}

static u64 load64_be(const u8 s[8])
{
    return((u64)s[0] << 56)
        | ((u64)s[1] << 48)
        | ((u64)s[2] << 40)
        | ((u64)s[3] << 32)
        | ((u64)s[4] << 24)
        | ((u64)s[5] << 16)
        | ((u64)s[6] <<  8)
        |  (u64)s[7];
}

static void store64_be(u8 out[8], u64 in)
{
    out[0] = (in >> 56) & 0xff;
    out[1] = (in >> 48) & 0xff;
    out[2] = (in >> 40) & 0xff;
    out[3] = (in >> 32) & 0xff;
    out[4] = (in >> 24) & 0xff;
    out[5] = (in >> 16) & 0xff;
    out[6] = (in >>  8) & 0xff;
    out[7] =  in        & 0xff;
}

///////////////
/// SHA 512 ///
///////////////
static u64 rot(u64 x, int c       ) { return (x >> c) | (x << (64 - c));   }
static u64 ch (u64 x, u64 y, u64 z) { return (x & y) ^ (~x & z);           }
static u64 maj(u64 x, u64 y, u64 z) { return (x & y) ^ ( x & z) ^ (y & z); }
static u64 big_sigma0(u64 x) { return rot(x, 28) ^ rot(x, 34) ^ rot(x, 39); }
static u64 big_sigma1(u64 x) { return rot(x, 14) ^ rot(x, 18) ^ rot(x, 41); }
static u64 lit_sigma0(u64 x) { return rot(x,  1) ^ rot(x,  8) ^ (x >> 7);   }
static u64 lit_sigma1(u64 x) { return rot(x, 19) ^ rot(x, 61) ^ (x >> 6);   }

static const u64 K[80] = {
    0x428a2f98d728ae22,0x7137449123ef65cd,0xb5c0fbcfec4d3b2f,0xe9b5dba58189dbbc,
    0x3956c25bf348b538,0x59f111f1b605d019,0x923f82a4af194f9b,0xab1c5ed5da6d8118,
    0xd807aa98a3030242,0x12835b0145706fbe,0x243185be4ee4b28c,0x550c7dc3d5ffb4e2,
    0x72be5d74f27b896f,0x80deb1fe3b1696b1,0x9bdc06a725c71235,0xc19bf174cf692694,
    0xe49b69c19ef14ad2,0xefbe4786384f25e3,0x0fc19dc68b8cd5b5,0x240ca1cc77ac9c65,
    0x2de92c6f592b0275,0x4a7484aa6ea6e483,0x5cb0a9dcbd41fbd4,0x76f988da831153b5,
    0x983e5152ee66dfab,0xa831c66d2db43210,0xb00327c898fb213f,0xbf597fc7beef0ee4,
    0xc6e00bf33da88fc2,0xd5a79147930aa725,0x06ca6351e003826f,0x142929670a0e6e70,
    0x27b70a8546d22ffc,0x2e1b21385c26c926,0x4d2c6dfc5ac42aed,0x53380d139d95b3df,
    0x650a73548baf63de,0x766a0abb3c77b2a8,0x81c2c92e47edaee6,0x92722c851482353b,
    0xa2bfe8a14cf10364,0xa81a664bbc423001,0xc24b8b70d0f89791,0xc76c51a30654be30,
    0xd192e819d6ef5218,0xd69906245565a910,0xf40e35855771202a,0x106aa07032bbd1b8,
    0x19a4c116b8d2d0c8,0x1e376c085141ab53,0x2748774cdf8eeb99,0x34b0bcb5e19b48a8,
    0x391c0cb3c5c95a63,0x4ed8aa4ae3418acb,0x5b9cca4f7763e373,0x682e6ff3d6b2b8a3,
    0x748f82ee5defb2fc,0x78a5636f43172f60,0x84c87814a1f0ab72,0x8cc702081a6439ec,
    0x90befffa23631e28,0xa4506cebde82bde9,0xbef9a3f7b2c67915,0xc67178f2e372532b,
    0xca273eceea26619c,0xd186b8c721c0c207,0xeada7dd6cde0eb1e,0xf57d4f7fee6ed178,
    0x06f067aa72176fba,0x0a637dc5a2c898a6,0x113f9804bef90dae,0x1b710b35131c471b,
    0x28db77f523047d84,0x32caab7b40c72493,0x3c9ebe0a15c9bebc,0x431d67c49c100d4c,
    0x4cc5d4becb3e42b6,0x597f299cfc657e2a,0x5fcb6fab3ad6faec,0x6c44198c4a475817
};

static void sha512_compress(crypto_sha512_ctx *ctx)
{
    u64 a = ctx->hash[0];    u64 b = ctx->hash[1];
    u64 c = ctx->hash[2];    u64 d = ctx->hash[3];
    u64 e = ctx->hash[4];    u64 f = ctx->hash[5];
    u64 g = ctx->hash[6];    u64 h = ctx->hash[7];

    FOR (j, 0, 16) {
        u64 in = K[j] + ctx->input[j];
        u64 t1 = big_sigma1(e) + ch (e, f, g) + h + in;
        u64 t2 = big_sigma0(a) + maj(a, b, c);
        h = g;  g = f;  f = e;  e = d  + t1;
        d = c;  c = b;  b = a;  a = t1 + t2;
    }
    size_t i16 = 0;
    FOR(i, 1, 5) {
        i16 += 16;
        FOR (j, 0, 16) {
            ctx->input[j] += lit_sigma1(ctx->input[(j- 2) & 15]);
            ctx->input[j] += lit_sigma0(ctx->input[(j-15) & 15]);
            ctx->input[j] +=            ctx->input[(j- 7) & 15];
            u64 in = K[i16 + j] + ctx->input[j];
            u64 t1 = big_sigma1(e) + ch (e, f, g) + h + in;
            u64 t2 = big_sigma0(a) + maj(a, b, c);
            h = g;  g = f;  f = e;  e = d  + t1;
            d = c;  c = b;  b = a;  a = t1 + t2;
        }
    }

    ctx->hash[0] += a;    ctx->hash[1] += b;
    ctx->hash[2] += c;    ctx->hash[3] += d;
    ctx->hash[4] += e;    ctx->hash[5] += f;
    ctx->hash[6] += g;    ctx->hash[7] += h;
}

static void sha512_set_input(crypto_sha512_ctx *ctx, u8 input)
{
    if (ctx->input_idx == 0) {
        ZERO(ctx->input, 16);
    }
    size_t word = ctx->input_idx >> 3;
    size_t byte = ctx->input_idx &  7;
    ctx->input[word] |= (u64)input << (8 * (7 - byte));
}

// increment a 128-bit "word".
static void sha512_incr(u64 x[2], u64 y)
{
    x[1] += y;
    if (x[1] < y) {
        x[0]++;
    }
}

static void sha512_end_block(crypto_sha512_ctx *ctx)
{
    if (ctx->input_idx == 128) {
        sha512_incr(ctx->input_size, 1024); // size is in bits
        sha512_compress(ctx);
        ctx->input_idx = 0;
    }
}

static void sha512_update(crypto_sha512_ctx *ctx,
                          const u8 *message, size_t message_size)
{
    FOR (i, 0, message_size) {
        sha512_set_input(ctx, message[i]);
        ctx->input_idx++;
        sha512_end_block(ctx);
    }
}

void crypto_sha512_init(crypto_sha512_ctx *ctx)
{
    ctx->hash[0] = 0x6a09e667f3bcc908;
    ctx->hash[1] = 0xbb67ae8584caa73b;
    ctx->hash[2] = 0x3c6ef372fe94f82b;
    ctx->hash[3] = 0xa54ff53a5f1d36f1;
    ctx->hash[4] = 0x510e527fade682d1;
    ctx->hash[5] = 0x9b05688c2b3e6c1f;
    ctx->hash[6] = 0x1f83d9abfb41bd6b;
    ctx->hash[7] = 0x5be0cd19137e2179;
    ctx->input_size[0] = 0;
    ctx->input_size[1] = 0;
    ctx->input_idx = 0;
}

void crypto_sha512_update(crypto_sha512_ctx *ctx,
                          const u8 *message, size_t message_size)
{
    if (message_size == 0) {
        return;
    }
    // Align ourselves with block boundaries
    size_t aligned = MIN(align(ctx->input_idx, 128), message_size);
    sha512_update(ctx, message, aligned);
    message      += aligned;
    message_size -= aligned;

    // Process the message block by block
    FOR (i, 0, message_size / 128) { // number of blocks
        FOR (j, 0, 16) {
            ctx->input[j] = load64_be(message + j*8);
        }
        message        += 128;
        ctx->input_idx += 128;
        sha512_end_block(ctx);
    }
    message_size &= 127;

    // remaining bytes
    sha512_update(ctx, message, message_size);
}

void crypto_sha512_final(crypto_sha512_ctx *ctx, u8 hash[64])
{
    sha512_incr(ctx->input_size, ctx->input_idx * 8); // size is in bits
    sha512_set_input(ctx, 128);                       // padding

    // compress penultimate block (if any)
    if (ctx->input_idx > 111) {
        sha512_compress(ctx);
        ZERO(ctx->input, 14);
    }
    // compress last block
    ctx->input[14] = ctx->input_size[0];
    ctx->input[15] = ctx->input_size[1];
    sha512_compress(ctx);

    // copy hash to output (big endian)
    FOR (i, 0, 8) {
        store64_be(hash + i*8, ctx->hash[i]);
    }

    WIPE_CTX(ctx);
}

void crypto_sha512(u8 hash[64], const u8 *message, size_t message_size)
{
    crypto_sha512_ctx ctx;
    crypto_sha512_init  (&ctx);
    crypto_sha512_update(&ctx, message, message_size);
    crypto_sha512_final (&ctx, hash);
}

static void sha512_vtable_init(void *ctx) {
    crypto_sha512_init(&((crypto_sign_ed25519_ctx*)ctx)->hash);
}
static void sha512_vtable_update(void *ctx, const u8 *m, size_t s) {
    crypto_sha512_update(&((crypto_sign_ed25519_ctx*)ctx)->hash, m, s);
}
static void sha512_vtable_final(void *ctx, u8 *h) {
    crypto_sha512_final(&((crypto_sign_ed25519_ctx*)ctx)->hash, h);
}
const crypto_sign_vtable crypto_sha512_vtable = {
    crypto_sha512,
    sha512_vtable_init,
    sha512_vtable_update,
    sha512_vtable_final,
    sizeof(crypto_sign_ed25519_ctx),
};

////////////////////
/// HMAC SHA 512 ///
////////////////////
void crypto_hmac_sha512_init(crypto_hmac_sha512_ctx *ctx,
                             const u8 *key, size_t key_size)
{
    // hash key if it is too long
    if (key_size > 128) {
        crypto_sha512(ctx->key, key, key_size);
        key      = ctx->key;
        key_size = 64;
    }
    // Compute inner key: padded key XOR 0x36
    FOR (i, 0, key_size)   { ctx->key[i] = key[i] ^ 0x36; }
    FOR (i, key_size, 128) { ctx->key[i] =          0x36; }
    // Start computing inner hash
    crypto_sha512_init  (&ctx->ctx);
    crypto_sha512_update(&ctx->ctx, ctx->key, 128);
}

void crypto_hmac_sha512_update(crypto_hmac_sha512_ctx *ctx,
                               const u8 *message, size_t message_size)
{
    crypto_sha512_update(&ctx->ctx, message, message_size);
}

void crypto_hmac_sha512_final(crypto_hmac_sha512_ctx *ctx, u8 hmac[64])
{
    // Finish computing inner hash
    crypto_sha512_final(&ctx->ctx, hmac);
    // Compute outer key: padded key XOR 0x5c
    FOR (i, 0, 128) {
        ctx->key[i] ^= 0x36 ^ 0x5c;
    }
    // Compute outer hash
    crypto_sha512_init  (&ctx->ctx);
    crypto_sha512_update(&ctx->ctx, ctx->key , 128);
    crypto_sha512_update(&ctx->ctx, hmac, 64);
    crypto_sha512_final (&ctx->ctx, hmac); // outer hash
    WIPE_CTX(ctx);
}

void crypto_hmac_sha512(u8 hmac[64], const u8 *key, size_t key_size,
                        const u8 *message, size_t message_size)
{
    crypto_hmac_sha512_ctx ctx;
    crypto_hmac_sha512_init  (&ctx, key, key_size);
    crypto_hmac_sha512_update(&ctx, message, message_size);
    crypto_hmac_sha512_final (&ctx, hmac);
}


///////////////
/// Ed25519 ///
///////////////

void crypto_ed25519_public_key(u8       public_key[32],
                               const u8 secret_key[32])
{
    crypto_sign_public_key_custom_hash(public_key, secret_key,
                                       &crypto_sha512_vtable);
}

void crypto_ed25519_sign_init_first_pass(crypto_sign_ctx_abstract *ctx,
                                         const u8 secret_key[32],
                                         const u8 public_key[32])
{
    crypto_sign_init_first_pass_custom_hash(ctx, secret_key, public_key,
                                            &crypto_sha512_vtable);
}

void crypto_ed25519_check_init(crypto_check_ctx_abstract *ctx,
                               const u8 signature[64],
                               const u8 public_key[32])
{
    crypto_check_init_custom_hash(ctx, signature, public_key,
                                  &crypto_sha512_vtable);
}

void crypto_ed25519_sign(u8        signature [64],
                         const u8  secret_key[32],
                         const u8  public_key[32],
                         const u8 *message, size_t message_size)
{
    crypto_sign_ed25519_ctx ctx;
    crypto_sign_ctx_abstract *actx = (crypto_sign_ctx_abstract*)&ctx;
    crypto_ed25519_sign_init_first_pass (actx, secret_key, public_key);
    crypto_ed25519_sign_update          (actx, message, message_size);
    crypto_ed25519_sign_init_second_pass(actx);
    crypto_ed25519_sign_update          (actx, message, message_size);
    crypto_ed25519_sign_final           (actx, signature);
}

int crypto_ed25519_check(const u8  signature [64],
                         const u8  public_key[32],
                         const u8 *message, size_t message_size)
{
    crypto_check_ed25519_ctx ctx;
    crypto_check_ctx_abstract *actx = (crypto_check_ctx_abstract*)&ctx;
    crypto_ed25519_check_init  (actx, signature, public_key);
    crypto_ed25519_check_update(actx, message, message_size);
    return crypto_ed25519_check_final(actx);
}

void crypto_from_ed25519_private(u8 x25519[32], const u8 eddsa[32])
{
    u8 a[64];
    crypto_sha512(a, eddsa, 32);
    COPY(x25519, a, 32);
    WIPE_BUFFER(a);
}