// Monocypher version 4.0.2
//
// 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"

#ifdef MONOCYPHER_CPP_NAMESPACE
namespace MONOCYPHER_CPP_NAMESPACE {
#endif

/////////////////
/// 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;
}

static void load64_be_buf (u64 *dst, const u8 *src, size_t size) {
    FOR (i, 0, size) { dst[i] = load64_be (src + i * 8); }
}

///////////////
/// 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;
}

// Write 1 input byte
static void sha512_set_input (crypto_sha512_ctx *ctx, u8 input) {
    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]++;
    }
}

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;
    ZERO (ctx->input, 16);
}

void crypto_sha512_update (crypto_sha512_ctx *ctx,
                           const u8 *message, size_t message_size) {
    // Avoid undefined NULL pointer increments with empty messages
    if (message_size == 0) {
        return;
    }

    // Align ourselves with word boundaries
    if ((ctx->input_idx & 7) != 0) {
        size_t nb_bytes = MIN (align (ctx->input_idx, 8), message_size);
        FOR (i, 0, nb_bytes) {
            sha512_set_input (ctx, message[i]);
            ctx->input_idx++;
        }
        message += nb_bytes;
        message_size -= nb_bytes;
    }

    // Align ourselves with block boundaries
    if ((ctx->input_idx & 127) != 0) {
        size_t nb_words = MIN (align (ctx->input_idx, 128), message_size) >> 3;
        load64_be_buf (ctx->input + (ctx->input_idx >> 3), message, nb_words);
        ctx->input_idx += nb_words << 3;
        message += nb_words << 3;
        message_size -= nb_words << 3;
    }

    // Compress block if needed
    if (ctx->input_idx == 128) {
        sha512_incr (ctx->input_size, 1024);  // size is in bits
        sha512_compress (ctx);
        ctx->input_idx = 0;
        ZERO (ctx->input, 16);
    }

    // Process the message block by block
    FOR (i, 0, message_size >> 7) {           // number of blocks
        load64_be_buf (ctx->input, message, 16);
        sha512_incr (ctx->input_size, 1024);  // size is in bits
        sha512_compress (ctx);
        ctx->input_idx = 0;
        ZERO (ctx->input, 16);
        message += 128;
    }
    message_size &= 127;

    if (message_size != 0) {
        // Remaining words
        size_t nb_words = message_size >> 3;
        load64_be_buf (ctx->input, message, nb_words);
        ctx->input_idx += nb_words << 3;
        message += nb_words << 3;
        message_size -= nb_words << 3;

        // Remaining bytes
        FOR (i, 0, message_size) {
            sha512_set_input (ctx, message[i]);
            ctx->input_idx++;
        }
    }
}

void crypto_sha512_final (crypto_sha512_ctx *ctx, u8 hash[64]) {
    // Add padding bit
    if (ctx->input_idx == 0) {
        ZERO (ctx->input, 16);
    }
    sha512_set_input (ctx, 128);

    // Update size
    sha512_incr (ctx->input_size, ctx->input_idx * 8);

    // 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);
}

////////////////////
/// HMAC SHA 512 ///
////////////////////
void crypto_sha512_hmac_init (crypto_sha512_hmac_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_sha512_hmac_update (crypto_sha512_hmac_ctx *ctx,
                                const u8 *message, size_t message_size) {
    crypto_sha512_update (&ctx->ctx, message, message_size);
}

void crypto_sha512_hmac_final (crypto_sha512_hmac_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_sha512_hmac (u8 hmac[64], const u8 *key, size_t key_size,
                         const u8 *message, size_t message_size) {
    crypto_sha512_hmac_ctx ctx;
    crypto_sha512_hmac_init (&ctx, key, key_size);
    crypto_sha512_hmac_update (&ctx, message, message_size);
    crypto_sha512_hmac_final (&ctx, hmac);
}

////////////////////
/// HKDF SHA 512 ///
////////////////////
void crypto_sha512_hkdf_expand (u8 *okm, size_t okm_size,
                                const u8 *prk, size_t prk_size,
                                const u8 *info, size_t info_size) {
    int not_first = 0;
    u8 ctr = 1;
    u8 blk[64];

    while (okm_size > 0) {
        size_t out_size = MIN (okm_size, sizeof (blk));

        crypto_sha512_hmac_ctx ctx;
        crypto_sha512_hmac_init (&ctx, prk, prk_size);
        if (not_first) {
            // For some reason HKDF uses some kind of CBC mode.
            // For some reason CTR mode alone wasn't enough.
            // Like what, they didn't trust HMAC in 2010?  Really??
            crypto_sha512_hmac_update (&ctx, blk, sizeof (blk));
        }
        crypto_sha512_hmac_update (&ctx, info, info_size);
        crypto_sha512_hmac_update (&ctx, &ctr, 1);
        crypto_sha512_hmac_final (&ctx, blk);

        COPY (okm, blk, out_size);

        not_first = 1;
        okm += out_size;
        okm_size -= out_size;
        ctr++;
    }
}

void crypto_sha512_hkdf (u8 *okm, size_t okm_size,
                         const u8 *ikm, size_t ikm_size,
                         const u8 *salt, size_t salt_size,
                         const u8 *info, size_t info_size) {
    // Extract
    u8 prk[64];
    crypto_sha512_hmac (prk, salt, salt_size, ikm, ikm_size);

    // Expand
    crypto_sha512_hkdf_expand (okm, okm_size, prk, sizeof (prk), info, info_size);
}

///////////////
/// Ed25519 ///
///////////////
void crypto_ed25519_key_pair (u8 secret_key[64], u8 public_key[32], u8 seed[32]) {
    u8 a[64];
    COPY (a, seed, 32);                       // a[ 0..31]  = seed
    crypto_wipe (seed, 32);
    COPY (secret_key, a, 32);                 // secret key = seed
    crypto_sha512 (a, a, 32);                 // a[ 0..31]  = scalar
    crypto_eddsa_trim_scalar (a, a);          // a[ 0..31]  = trimmed scalar
    crypto_eddsa_scalarbase (public_key, a);  // public key = [trimmed scalar]B
    COPY (secret_key + 32, public_key, 32);   // secret key includes public half
    WIPE_BUFFER (a);
}

static void hash_reduce (u8 h[32],
                         const u8 *a, size_t a_size,
                         const u8 *b, size_t b_size,
                         const u8 *c, size_t c_size,
                         const u8 *d, size_t d_size) {
    u8 hash[64];
    crypto_sha512_ctx ctx;
    crypto_sha512_init (&ctx);
    crypto_sha512_update (&ctx, a, a_size);
    crypto_sha512_update (&ctx, b, b_size);
    crypto_sha512_update (&ctx, c, c_size);
    crypto_sha512_update (&ctx, d, d_size);
    crypto_sha512_final (&ctx, hash);
    crypto_eddsa_reduce (h, hash);
}

static void ed25519_dom_sign (u8 signature[64], const u8 secret_key[32],
                              const u8 *dom, size_t dom_size,
                              const u8 *message, size_t message_size) {
    u8 a[64];  // secret scalar and prefix
    u8 r[32];  // secret deterministic "random" nonce
    u8 h[32];  // publically verifiable hash of the message (not wiped)
    u8 R[32];  // first half of the signature (allows overlapping inputs)
    const u8 *pk = secret_key + 32;

    crypto_sha512 (a, secret_key, 32);
    crypto_eddsa_trim_scalar (a, a);
    hash_reduce (r, dom, dom_size, a + 32, 32, message, message_size, 0, 0);
    crypto_eddsa_scalarbase (R, r);
    hash_reduce (h, dom, dom_size, R, 32, pk, 32, message, message_size);
    COPY (signature, R, 32);
    crypto_eddsa_mul_add (signature + 32, h, a, r);

    WIPE_BUFFER (a);
    WIPE_BUFFER (r);
}
// Meshcore-parity Ed25519 signing (non-standard, do NOT use outside Meshcore networks)
static void ed25519_meshcore_sign(u8 signature[64],
                                  const u8 priv_seed[32],    // secret seed (32 bytes)
                                  const u8 pub_key[32],      // public key (32 bytes)
                                  const u8 *message, size_t message_size)
{
    u8 a[64];   // secret scalar and prefix (same buffer as Monocypher)
    u8 r[32];   // nonce scalar
    u8 h[32];   // challenge scalar
    u8 R[32];   // encoded R

    // 1. Derive scalar a (clamped) and prefix (discarded here, Meshcore doesnĄ¯t use it)
    crypto_sha512(a, priv_seed, 32);   // hash the seed
    crypto_eddsa_trim_scalar(a, a);    // clamp scalar a

    // 2. Derive nonce r = H(public_key || message) instead of H(prefix || message)
    hash_reduce(r, 0, 0, pub_key, 32, message, message_size, 0, 0);

    // 3. R = r * basepoint
    crypto_eddsa_scalarbase(R, r);

    // 4. h = H(R || public_key || message)
    hash_reduce(h, 0, 0, R, 32, pub_key, 32, message, message_size);

    // 5. signature = R || (h*a + r)
    COPY(signature, R, 32);
    crypto_eddsa_mul_add(signature + 32, h, a, r);

    // wipe secrets
    WIPE_BUFFER(a);
    WIPE_BUFFER(r);
}

void crypto_ed25519_meshcore_sign(u8 signature[64],
                                  const u8 priv_seed[32],
                                  const u8 pub_key[32],
                                  const u8 *message, size_t message_size)
{
    ed25519_meshcore_sign(signature, priv_seed, pub_key, message, message_size);
}


void crypto_ed25519_sign (u8 signature[64], const u8 secret_key[64],
                          const u8 *message, size_t message_size) {
    ed25519_dom_sign (signature, secret_key, 0, 0, message, message_size);
}

int crypto_ed25519_check (const u8 signature[64], const u8 public_key[32],
                          const u8 *msg, size_t msg_size) {
    u8 h_ram[32];
    hash_reduce (h_ram, signature, 32, public_key, 32, msg, msg_size, 0, 0);
    return crypto_eddsa_check_equation (signature, public_key, h_ram);
}

static const u8 domain[34] = "SigEd25519 no Ed25519 collisions\1";

void crypto_ed25519_ph_sign (uint8_t signature[64], const uint8_t secret_key[64],
                             const uint8_t message_hash[64]) {
    ed25519_dom_sign (signature, secret_key, domain, sizeof (domain),
                      message_hash, 64);
}

int crypto_ed25519_ph_check (const uint8_t sig[64], const uint8_t pk[32],
                             const uint8_t msg_hash[64]) {
    u8 h_ram[32];
    hash_reduce (h_ram, domain, sizeof (domain), sig, 32, pk, 32, msg_hash, 64);
    return crypto_eddsa_check_equation (sig, pk, h_ram);
}


#ifdef MONOCYPHER_CPP_NAMESPACE
}
#endif