/* This module generates and compares password hashes using SHA256 algorithms.
 *
 * If an intruder gets access to your system or uses a brute force attack,
 * salt will not provide much value.
 * IMPORTANT: DATA HASHES CANNOT BE "DECRYPTED" BACK TO PLAIN TEXT.
 *
 * Modified for Anope.
 * (C) 2003-2020 Anope Team
 * Contact us at team@anope.org
 *
 * Taken from InspIRCd (https://www.inspircd.org/),
 * see https://wiki.inspircd.org/Credits
 *
 * This program is free but copyrighted software; see
 * the file COPYING for details.
 */

/* FIPS 180-2 SHA-224/256/384/512 implementation
 * Last update: 05/23/2005
 * Issue date:  04/30/2005
 *
 * Copyright (C) 2005 Olivier Gay <olivier.gay@a3.epfl.ch>
 * 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.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT 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 PROJECT 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.
 */

#include "module.h"
#include "modules/encryption.h"

static const unsigned SHA256_DIGEST_SIZE = 256 / 8;
static const unsigned SHA256_BLOCK_SIZE = 512 / 8;

inline static uint32_t SHFR(uint32_t x, uint32_t n) { return x >> n; }
inline static uint32_t ROTR(uint32_t x, uint32_t n) { return (x >> n) | (x << ((sizeof(x) << 3) - n)); }
inline static uint32_t ROTL(uint32_t x, uint32_t n) { return (x << n) | (x >> ((sizeof(x) << 3) - n)); }
inline static uint32_t CH(uint32_t x, uint32_t y, uint32_t z) { return (x & y) ^ (~x & z); }
inline static uint32_t MAJ(uint32_t x, uint32_t y, uint32_t z) { return (x & y) ^ (x & z) ^ (y & z); }

inline static uint32_t SHA256_F1(uint32_t x) { return ROTR(x, 2) ^ ROTR(x, 13) ^ ROTR(x, 22); }
inline static uint32_t SHA256_F2(uint32_t x) { return ROTR(x, 6) ^ ROTR(x, 11) ^ ROTR(x, 25); }
inline static uint32_t SHA256_F3(uint32_t x) { return ROTR(x, 7) ^ ROTR(x, 18) ^ SHFR(x, 3); }
inline static uint32_t SHA256_F4(uint32_t x) { return ROTR(x, 17) ^ ROTR(x, 19) ^ SHFR(x, 10); }

inline static void UNPACK32(unsigned x, unsigned char *str)
{
	str[3] = static_cast<uint8_t>(x);
	str[2] = static_cast<uint8_t>(x >> 8);
	str[1] = static_cast<uint8_t>(x >> 16);
	str[0] = static_cast<uint8_t>(x >> 24);
}

inline static void PACK32(unsigned char *str, uint32_t &x)
{
	x = static_cast<uint32_t>(str[3]) | static_cast<uint32_t>(str[2]) << 8 | static_cast<uint32_t>(str[1]) << 16 | static_cast<uint32_t>(str[0]) << 24;
}

/* Macros used for loops unrolling */

inline static void SHA256_SCR(uint32_t w[64], int i)
{
	w[i] = SHA256_F4(w[i - 2]) + w[i - 7] + SHA256_F3(w[i - 15]) + w[i - 16];
}

static const uint32_t sha256_h0[8] =
{
	0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a,
	0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
};

static const uint32_t sha256_k[64] =
{
	0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
	0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
	0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
	0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
	0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
	0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
	0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
	0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
	0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
	0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
	0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
	0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
	0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
	0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
	0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
	0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};

/** An sha256 context
 */
class SHA256Context : public Encryption::Context
{
	void Transform(unsigned char *message, unsigned block_nb)
	{
		uint32_t w[64], wv[8];
		unsigned char *sub_block;
		for (unsigned i = 1; i <= block_nb; ++i)
		{
			int j;
			sub_block = message + ((i - 1) << 6);

			for (j = 0; j < 16; ++j)
				PACK32(&sub_block[j << 2], w[j]);
			for (j = 16; j < 64; ++j)
				SHA256_SCR(w, j);
			for (j = 0; j < 8; ++j)
				wv[j] = this->h[j];
			for (j = 0; j < 64; ++j)
			{
				uint32_t t1 = wv[7] + SHA256_F2(wv[4]) + CH(wv[4], wv[5], wv[6]) + sha256_k[j] + w[j];
				uint32_t t2 = SHA256_F1(wv[0]) + MAJ(wv[0], wv[1], wv[2]);
				wv[7] = wv[6];
				wv[6] = wv[5];
				wv[5] = wv[4];
				wv[4] = wv[3] + t1;
				wv[3] = wv[2];
				wv[2] = wv[1];
				wv[1] = wv[0];
				wv[0] = t1 + t2;
			}
			for (j = 0; j < 8; ++j)
				this->h[j] += wv[j];
		}
	}

	unsigned tot_len;
	unsigned len;
	unsigned char block[2 * SHA256_BLOCK_SIZE];
	uint32_t h[8];
	unsigned char digest[SHA256_DIGEST_SIZE];

 public:
	SHA256Context(Encryption::IV *iv)
	{
		if (iv != NULL)
		{
			if (iv->second != 8)
				throw CoreException("Invalid IV size");
			for (int i = 0; i < 8; ++i)
				this->h[i] = iv->first[i];
		}
		else
			for (int i = 0; i < 8; ++i)
				this->h[i] = sha256_h0[i];

		this->tot_len = 0;
		this->len = 0;
		memset(this->block, 0, sizeof(this->block));
		memset(this->digest, 0, sizeof(this->digest));
	}

	void Update(const unsigned char *message, size_t mlen) anope_override
	{
		unsigned tmp_len = SHA256_BLOCK_SIZE - this->len, rem_len = mlen < tmp_len ? mlen : tmp_len;

		memcpy(&this->block[this->len], message, rem_len);
		if (this->len + mlen < SHA256_BLOCK_SIZE)
		{
			this->len += mlen;
			return;
		}
		unsigned new_len = mlen - rem_len, block_nb = new_len / SHA256_BLOCK_SIZE;
		unsigned char *shifted_message = new unsigned char[mlen - rem_len];
		memcpy(shifted_message, message + rem_len, mlen - rem_len);
		this->Transform(this->block, 1);
		this->Transform(shifted_message, block_nb);
		rem_len = new_len % SHA256_BLOCK_SIZE;
		memcpy(this->block, &shifted_message[block_nb << 6], rem_len);
		delete [] shifted_message;
		this->len = rem_len;
		this->tot_len += (block_nb + 1) << 6;
	}

	void Finalize() anope_override
	{
		unsigned block_nb = 1 + ((SHA256_BLOCK_SIZE - 9) < (this->len % SHA256_BLOCK_SIZE));
		unsigned len_b = (this->tot_len + this->len) << 3;
		unsigned pm_len = block_nb << 6;
		memset(this->block + this->len, 0, pm_len - this->len);
		this->block[this->len] = 0x80;
		UNPACK32(len_b, this->block + pm_len - 4);
		this->Transform(this->block, block_nb);
		for (int i = 0 ; i < 8; ++i)
			UNPACK32(this->h[i], &this->digest[i << 2]);
	}

	Encryption::Hash GetFinalizedHash() anope_override
	{
		Encryption::Hash hash;
		hash.first = this->digest;
		hash.second = SHA256_DIGEST_SIZE;
		return hash;
	}
};

class SHA256Provider : public Encryption::Provider
{
 public:
	SHA256Provider(Module *creator) : Encryption::Provider(creator, "sha256") { }

	Encryption::Context *CreateContext(Encryption::IV *iv) anope_override
	{
		return new SHA256Context(iv);
	}

	Encryption::IV GetDefaultIV() anope_override
	{
		Encryption::IV iv;
		iv.first = sha256_h0;
		iv.second = sizeof(sha256_h0) / sizeof(uint32_t);
		return iv;
	}
};

class ESHA256 : public Module
{
	SHA256Provider sha256provider;

	unsigned iv[8];
	bool use_iv;

	/* initializes the IV with a new random value */
	void NewRandomIV()
	{
		for (int i = 0; i < 8; ++i)
			iv[i] = static_cast<uint32_t>(rand());
	}

	/* returns the IV as base64-encrypted string */
	Anope::string GetIVString()
	{
		char buf[33];
		for (int i = 0; i < 8; ++i)
			UNPACK32(iv[i], reinterpret_cast<unsigned char *>(&buf[i << 2]));
		buf[32] = '\0';
		return Anope::Hex(buf, 32);
	}

	/* splits the appended IV from the password string so it can be used for the next encryption */
	/* password format:  <hashmethod>:<password_b64>:<iv_b64> */
	void GetIVFromPass(const Anope::string &password)
	{
		size_t pos = password.find(':');
		Anope::string buf = password.substr(password.find(':', pos + 1) + 1, password.length());
		char buf2[33];
		Anope::Unhex(buf, buf2, sizeof(buf2));
		for (int i = 0 ; i < 8; ++i)
			PACK32(reinterpret_cast<unsigned char *>(&buf2[i << 2]), iv[i]);
	}

 public:
	ESHA256(const Anope::string &modname, const Anope::string &creator) : Module(modname, creator, ENCRYPTION | VENDOR),
		sha256provider(this)
	{


		use_iv = false;
	}

	EventReturn OnEncrypt(const Anope::string &src, Anope::string &dest) anope_override
	{
		if (!use_iv)
			NewRandomIV();
		else
			use_iv = false;

		Encryption::IV initilization(this->iv, 8);
		SHA256Context ctx(&initilization);
		ctx.Update(reinterpret_cast<const unsigned char *>(src.c_str()), src.length());
		ctx.Finalize();

		Encryption::Hash hash = ctx.GetFinalizedHash();

		std::stringstream buf;
		buf << "sha256:" << Anope::Hex(reinterpret_cast<const char *>(hash.first), hash.second) << ":" << GetIVString();
		Log(LOG_DEBUG_2) << "(enc_sha256) hashed password from [" << src << "] to [" << buf.str() << " ]";
		dest = buf.str();
		return EVENT_ALLOW;
	}

	void OnCheckAuthentication(User *, IdentifyRequest *req) anope_override
	{
		const NickAlias *na = NickAlias::Find(req->GetAccount());
		if (na == NULL)
			return;
		NickCore *nc = na->nc;

		size_t pos = nc->pass.find(':');
		if (pos == Anope::string::npos)
			return;
		Anope::string hash_method(nc->pass.begin(), nc->pass.begin() + pos);
		if (!hash_method.equals_cs("sha256"))
			return;

		GetIVFromPass(nc->pass);
		use_iv = true;
		Anope::string buf;
		this->OnEncrypt(req->GetPassword(), buf);
		if (nc->pass.equals_cs(buf))
		{
			/* if we are NOT the first module in the list,
			 * we want to re-encrypt the pass with the new encryption
			 */
			if (ModuleManager::FindFirstOf(ENCRYPTION) != this)
				Anope::Encrypt(req->GetPassword(), nc->pass);
			req->Success(this);
		}
	}
};

MODULE_INIT(ESHA256)
