/* 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) 2003-2022 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 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 initialization(this->iv, 8);
 		SHA256Context ctx(&initialization);
 		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)

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