/* Module for encryption using MD5.
 *
 * Modified for Anope.
 * (C) 2003-2022 Anope Team
 * Contact us at team@anope.org
 *
 * Taken from IRC Services and is copyright (c) 1996-2002 Andrew Church.
 *	 E-mail: <achurch@achurch.org>
 * Parts written by Andrew Kempe and others.
 * This program is free but copyrighted software; see the file COPYING for
 * details.
 */

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

/* Copyright (C) 1991-2, RSA Data Security, Inc. Created 1991. All
rights reserved.

License to copy and use this software is granted provided that it
is identified as the "RSA Data Security, Inc. MD5 Message-Digest
Algorithm" in all material mentioning or referencing this software
or this function.

License is also granted to make and use derivative works provided
that such works are identified as "derived from the RSA Data
Security, Inc. MD5 Message-Digest Algorithm" in all material
mentioning or referencing the derived work.

RSA Data Security, Inc. makes no representations concerning either
the merchantability of this software or the suitability of this
software for any particular purpose. It is provided "as is"
without express or implied warranty of any kind.

These notices must be retained in any copies of any part of this
documentation and/or software.
 */

static unsigned char PADDING[64] = {
	0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

/* F, G, H and I are basic MD5 functions.
 */
inline static unsigned F(unsigned x, unsigned y, unsigned z) { return (x & y) | (~x & z); }
inline static unsigned G(unsigned x, unsigned y, unsigned z) { return (x & z) | (y & ~z); }
inline static unsigned H(unsigned x, unsigned y, unsigned z) { return x ^ y ^ z; }
inline static unsigned I(unsigned x, unsigned y, unsigned z) { return y ^ (x | ~z); }

/* ROTATE_LEFT rotates x left n bits.
 */
inline static unsigned ROTATE_LEFT(unsigned x, unsigned n) { return (x << n) | (x >> (32 - n)); }

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.
 * Rotation is separate from addition to prevent recomputation.
 */
inline static void FF(unsigned &a, unsigned b, unsigned c, unsigned d, unsigned x, unsigned s, unsigned ac)
{
	a += F(b, c, d) + x + ac;
	a = ROTATE_LEFT(a, s);
	a += b;
}
inline static void GG(unsigned &a, unsigned b, unsigned c, unsigned d, unsigned x, unsigned s, unsigned ac)
{
	a += G(b, c, d) + x + ac;
	a = ROTATE_LEFT(a, s);
	a += b;
}
inline static void HH(unsigned &a, unsigned b, unsigned c, unsigned d, unsigned x, unsigned s, unsigned ac)
{
	a += H(b, c, d) + x + ac;
	a = ROTATE_LEFT(a, s);
	a += b;
}
inline static void II(unsigned &a, unsigned b, unsigned c, unsigned d, unsigned x, unsigned s, unsigned ac)
{
	a += I(b, c, d) + x + ac;
	a = ROTATE_LEFT(a, s);
	a += b;
}

static const uint32_t md5_iv[4] =
{
	0x67452301, 0xefcdab89, 0x98badcfe, 0x10325476
};

class MD5Context : public Encryption::Context
{
	unsigned state[4]; /* state (ABCD) */
	unsigned count[2]; /* number of bits, modulo 2^64 (lsb first) */
	unsigned char buffer[64]; /* input buffer */
	unsigned char digest[16]; /* final digest */

	/* Constants for MD5Transform routine.
	 */
	enum
	{
		S11 = 7,
		S12 = 12,
		S13 = 17,
		S14 = 22,
		S21 = 5,
		S22 = 9,
		S23 = 14,
		S24 = 20,
		S31 = 4,
		S32 = 11,
		S33 = 16,
		S34 = 23,
		S41 = 6,
		S42 = 10,
		S43 = 15,
		S44 = 21
	};

	/* MD5 basic transformation. Transforms state based on block.
	 */
	void Transform(const unsigned char block[64])
	{
		unsigned a = state[0], b = state[1], c = state[2], d = state[3], x[16];

		Decode(x, block, 64);

		/* Round 1 */
		FF(a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */
		FF(d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */
		FF(c, d, a, b, x[2], S13, 0x242070db); /* 3 */
		FF(b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */
		FF(a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */
		FF(d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */
		FF(c, d, a, b, x[6], S13, 0xa8304613); /* 7 */
		FF(b, c, d, a, x[7], S14, 0xfd469501); /* 8 */
		FF(a, b, c, d, x[8], S11, 0x698098d8); /* 9 */
		FF(d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */
		FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
		FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
		FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
		FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
		FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
		FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

		/* Round 2 */
		GG(a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */
		GG(d, a, b, c, x[6], S22, 0xc040b340); /* 18 */
		GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
		GG(b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */
		GG(a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */
		GG(d, a, b, c, x[10], S22, 0x2441453); /* 22 */
		GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
		GG(b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */
		GG(a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */
		GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
		GG(c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */
		GG(b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */
		GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
		GG(d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */
		GG(c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */
		GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

		/* Round 3 */
		HH(a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */
		HH(d, a, b, c, x[8], S32, 0x8771f681); /* 34 */
		HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
		HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
		HH(a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */
		HH(d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */
		HH(c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */
		HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
		HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
		HH(d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */
		HH(c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */
		HH(b, c, d, a, x[6], S34, 0x4881d05); /* 44 */
		HH(a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */
		HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
		HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
		HH(b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 */

		/* Round 4 */
		II(a, b, c, d, x[0], S41, 0xf4292244); /* 49 */
		II(d, a, b, c, x[7], S42, 0x432aff97); /* 50 */
		II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
		II(b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */
		II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
		II(d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */
		II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
		II(b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */
		II(a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */
		II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
		II(c, d, a, b, x[6], S43, 0xa3014314); /* 59 */
		II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
		II(a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */
		II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
		II(c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */
		II(b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */

		state[0] += a;
		state[1] += b;
		state[2] += c;
		state[3] += d;

		/* Zeroize sensitive information. */
		memset(x, 0, sizeof(x));
	}

	/* Encodes input (unsigned) into output (unsigned char). Assumes len is
	 * a multiple of 4.
	 */
	void Encode(unsigned char *output, unsigned *input, unsigned len)
	{
		for (unsigned i = 0, j = 0; j < len; ++i, j += 4)
		{
			output[j] = static_cast<unsigned char>(input[i] & 0xff);
			output[j + 1] = static_cast<unsigned char>((input[i] >> 8) & 0xff);
			output[j + 2] = static_cast<unsigned char>((input[i] >> 16) & 0xff);
			output[j + 3] = static_cast<unsigned char>((input[i] >> 24) & 0xff);
		}
	}

	/* Decodes input (unsigned char) into output (unsigned). Assumes len is
	 * a multiple of 4.
	 */
	void Decode(unsigned *output, const unsigned char *input, unsigned len)
	{
		for (unsigned i = 0, j = 0; j < len; ++i, j += 4)
			output[i] = static_cast<unsigned>(input[j]) | (static_cast<unsigned>(input[j + 1]) << 8) | (static_cast<unsigned>(input[j + 2]) << 16) | (static_cast<unsigned>(input[j + 3]) << 24);
	}

 public:
	MD5Context(Encryption::IV *iv = NULL)
	{
		if (iv != NULL)
		{
			if (iv->second != 4)
				throw CoreException("Invalid IV size");
			/* Load magic initialization constants. */
			for (int i = 0; i < 4; ++i)
				this->state[i] = iv->first[i];
		}
		else
			for (int i = 0; i < 4; ++i)
				this->state[i] = md5_iv[i];

		this->count[0] = this->count[1] = 0;
		memset(this->buffer, 0, sizeof(this->buffer));
	}

	/* MD5 block update operation. Continues an MD5 message-digest
	 * operation, processing another message block, and updating the
	 * context.
	 */
	void Update(const unsigned char *input, size_t len) anope_override
	{
		unsigned i, index, partLen;

		/* Compute number of bytes mod 64 */
		index = (this->count[0] >> 3) & 0x3F;

		/* Update number of bits */
		if ((this->count[0] += len << 3) < (len << 3))
			++this->count[1];
		this->count[1] += len >> 29;

		partLen = 64 - index;

		/* Transform as many times as possible. */
		if (len >= partLen)
		{
			memcpy(&this->buffer[index], input, partLen);
			this->Transform(this->buffer);

			for (i = partLen; i + 63 < len; i += 64)
				this->Transform(&input[i]);

			index = 0;
		}
		else
			i = 0;

		/* Buffer remaining input */
		memcpy(&this->buffer[index], &input[i], len - i);
	}

	/* MD5 finalization. Ends an MD5 message-digest opera
	 * the message digest and zeroizing the context.
	 */
	void Finalize() anope_override
	{
		unsigned char bits[8];
		unsigned index, padLen;

		/* Save number of bits */
		this->Encode(bits, this->count, 8);

		/* Pad out to 56 mod 64. */
		index = (this->count[0] >> 3) & 0x3f;
		padLen = index < 56 ? 56 - index : 120 - index;
		this->Update(PADDING, padLen);

		/* Append length (before padding) */
		this->Update(bits, 8);
		/* Store state in digest */
		this->Encode(digest, this->state, 16);

		/* Zeroize sensitive information. */
		memset(this->state, 0, sizeof(this->state));
		memset(this->count, 0, sizeof(this->count));
		memset(this->buffer, 0, sizeof(this->buffer));
	}

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

class MD5Provider : public Encryption::Provider
{
 public:
	MD5Provider(Module *creator) : Encryption::Provider(creator, "md5") { }

	Encryption::Context *CreateContext(Encryption::IV *iv) anope_override
	{
		return new MD5Context(iv);
	}

	Encryption::IV GetDefaultIV() anope_override
	{
		Encryption::IV iv;
		iv.first = md5_iv;
		iv.second = sizeof(md5_iv) / sizeof(uint32_t);
		return iv;
	}
};

class EMD5 : public Module
{
	MD5Provider md5provider;

 public:
	EMD5(const Anope::string &modname, const Anope::string &creator) : Module(modname, creator, ENCRYPTION | VENDOR),
		md5provider(this)
	{

	}

	EventReturn OnEncrypt(const Anope::string &src, Anope::string &dest) anope_override
	{
		MD5Context context;

		context.Update(reinterpret_cast<const unsigned char *>(src.c_str()), src.length());
		context.Finalize();

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

		Anope::string buf = "md5:" + Anope::Hex(reinterpret_cast<const char *>(hash.first), hash.second);

		Log(LOG_DEBUG_2) << "(enc_md5) hashed password from [" << src << "] to [" << buf << "]";
		dest = buf;
		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("md5"))
			return;

		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(EMD5)