/*! \file
 *
 * \brief Based on the RFC 6234
 *
 * Copyright (c) 2011 IETF Trust and the persons identified as
 * authors of the code.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above
 *   copyright notice, this list of conditions and
 *   the following disclaimer.
 *
 * - 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.
 *
 * - Neither the name of Internet Society, IETF or IETF Trust, nor
 *   the names of specific contributors, may be used to endorse or
 *   promote products derived from this software without specific
 *   prior written permission.
 *
 * 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 OWNER 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.
 *
 *  Description:
 *      This file implements the Secure Hash Algorithm SHA-1
 *      as defined in the U.S. National Institute of Standards
 *      and Technology Federal Information Processing Standards
 *      Publication (FIPS PUB) 180-3 published in October 2008
 *      and formerly defined in its predecessors, FIPS PUB 180-1
 *      and FIP PUB 180-2.
 *
 *      A combined document showing all algorithms is available at
 *              http://csrc.nist.gov/publications/fips/
 *                     fips180-3/fips180-3_final.pdf
 *
 *      The SHA-1 algorithm produces a 160-bit message digest for a
 *      given data stream that can serve as a means of providing a
 *      "fingerprint" for a message.
 *
 *  Portability Issues:
 *      SHA-1 is defined in terms of 32-bit "words".  This code
 *      uses <stdint.h> (included via "sha.h") to define 32- and
 *      8-bit unsigned integer types.  If your C compiler does
 *      not support 32-bit unsigned integers, this code is not
 *      appropriate.
 *
 *  Caveats:
 *      SHA-1 is designed to work with messages less than 2^64 bits
 *      long.  This implementation uses SHA1Input() to hash the bits
 *      that are a multiple of the size of an 8-bit octet, and then
 *      optionally uses SHA1FinalBits() to hash the final few bits of
 *      the input.
 */

#include <asterisk/sha1.h>

/*! Define the SHA1 circular left shift macro */
#define SHA1_ROTL(bits,word) \
                (((word) << (bits)) | ((word) >> (32-(bits))))

/*
 * Add "length" to the length.
 * Set Corrupted when overflow has occurred.
 */
static uint32_t addTemp;
#define SHA1AddLength(context, length)                     \
    (addTemp = (context)->Length_Low,                      \
     (context)->Corrupted =                                \
        (((context)->Length_Low += (length)) < addTemp) && \
        (++(context)->Length_High == 0) ? shaInputTooLong  \
                                        : (context)->Corrupted )

/* Local Function Prototypes */
static void SHA1ProcessMessageBlock(SHA1Context * context);
static void SHA1Finalize(SHA1Context * context, uint8_t Pad_Byte);
static void SHA1PadMessage(SHA1Context * context, uint8_t Pad_Byte);

/*!
 * \brief SHA1Reset
 * \param context the context to be reset.
 * This function will initialize the SHA1Context in preparation
 * for computing a new SHA1 message digest.
 * \return sha Error Code.
 */
int SHA1Reset(SHA1Context *context)
{
	if (!context) {
		return shaNull;
	}

	context->Length_High = context->Length_Low = 0;
	context->Message_Block_Index = 0;

	/* Initial Hash Values: FIPS 180-3 section 5.3.1 */
	context->Intermediate_Hash[0] = 0x67452301;
	context->Intermediate_Hash[1] = 0xEFCDAB89;
	context->Intermediate_Hash[2] = 0x98BADCFE;
	context->Intermediate_Hash[3] = 0x10325476;
	context->Intermediate_Hash[4] = 0xC3D2E1F0;

	context->Computed = 0;
	context->Corrupted = shaSuccess;

	return shaSuccess;
}

/*!
 *  \brief SHA1Input
 * \param context [in/out] The SHA context to update
 * \param message_array [in] An array of characters representing the next portion of
 *		   the message.
 * \param length [in] The length of the message in message_array.
 *  This function accepts an array of octets as the next portion
 *  of the message.
 * \return sha Error Code.
 */
int SHA1Input(SHA1Context *context,
			  const uint8_t *message_array, unsigned length)
{
	if (!context) {
		return shaNull;
	}
	if (!length) {
		return shaSuccess;
	}
	if (!message_array) {
		return shaNull;
	}

	if (context->Computed) {
		context->Corrupted = shaStateError;
		return shaStateError;
	}

	if (context->Corrupted) {
		return context->Corrupted;
	}

	while (length--) {
		context->Message_Block[context->Message_Block_Index++] =
			*message_array;

		if ((SHA1AddLength(context, 8) == shaSuccess) &&
			(context->Message_Block_Index == SHA1_Message_Block_Size))
			SHA1ProcessMessageBlock(context);

		message_array++;
	}

	return context->Corrupted;
}

/*!
 * \brief SHA1FinalBits Add in any final bits of the message.
 *
 * \param context [in/out] The SHA context to update.
 * \param message_bits [in] The final bits of the message, in the upper portion of the
 *     byte.  (Use 0b###00000 instead of 0b00000### to input the
 *     three bits ###.)
 * \param length [in] *     The number of bits in message_bits, between 1 and 7.
 * \returns sha Error Code.
 */
int SHA1FinalBits(SHA1Context * context, uint8_t message_bits,
				  unsigned int length)
{
	static uint8_t masks[8] = {
		/* 0 0b00000000 */ 0x00, /* 1 0b10000000 */ 0x80,
		/* 2 0b11000000 */ 0xC0, /* 3 0b11100000 */ 0xE0,
		/* 4 0b11110000 */ 0xF0, /* 5 0b11111000 */ 0xF8,
		/* 6 0b11111100 */ 0xFC, /* 7 0b11111110 */ 0xFE
	};

	static uint8_t markbit[8] = {
		/* 0 0b10000000 */ 0x80, /* 1 0b01000000 */ 0x40,
		/* 2 0b00100000 */ 0x20, /* 3 0b00010000 */ 0x10,
		/* 4 0b00001000 */ 0x08, /* 5 0b00000100 */ 0x04,
		/* 6 0b00000010 */ 0x02, /* 7 0b00000001 */ 0x01
	};

	if (!context)
		return shaNull;
	if (!length)
		return shaSuccess;
	if (context->Corrupted)
		return context->Corrupted;
	if (context->Computed)
		return context->Corrupted = shaStateError;
	if (length >= 8)
		return context->Corrupted = shaBadParam;

	SHA1AddLength(context, length);
	SHA1Finalize(context,
				 (uint8_t) ((message_bits & masks[length]) |
							markbit[length]));

	return context->Corrupted;
}

/*
 * \brief SHA1Result Returns the resulting 160-bit digest
 * \param context [in/out] The SHA context to update.
 * \param Message_Digest [out] Where the digest is returned.
 *
 *   This function will return the 160-bit message digest
 *   into the Message_Digest array provided by the caller.
 * \note The first octet of hash is stored in the element with index 0,
 *       the last octet of hash in the element with index 19.
 * \returns sha Error Code.
 */
int SHA1Result(SHA1Context * context, uint8_t Message_Digest[SHA1HashSize])
{
	int i;

	if (!context) {
		return shaNull;
	}
	if (!Message_Digest) {
		return shaNull;
	}
	if (context->Corrupted) {
		return context->Corrupted;
	}

	if (!context->Computed) {
		SHA1Finalize(context, 0x80);
	}

	for (i = 0; i < SHA1HashSize; ++i) {
		Message_Digest[i] = (uint8_t) (context->Intermediate_Hash[i >> 2]
				>> (8 * (3 - (i & 0x03))));
	}

	return shaSuccess;
}

/*!
 * \brief Process the next 512 bits of the message stored in the Message_Block array.
 * \param context [in/out] The SHA context to update
 * \note  Many of the variable names in this code, especially the
 *	  single character names, were used because those were the
 *	  names used in the publication.
 * \returns nothing.
 */
static void SHA1ProcessMessageBlock(SHA1Context *context)
{
	/* Constants defined in FIPS 180-3, section 4.2.1 */
	const uint32_t K[4] = {
		0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6
	};
	int t;						/* Loop counter */
	uint32_t temp;				/* Temporary word value */
	uint32_t W[80];				/* Word sequence */
	uint32_t A, B, C, D, E;		/* Word buffers */

	/*
	 * Initialize the first 16 words in the array W
	 */
	for (t = 0; t < 16; t++) {
		W[t] = ((uint32_t) context->Message_Block[t * 4]) << 24;
		W[t] |= ((uint32_t) context->Message_Block[t * 4 + 1]) << 16;
		W[t] |= ((uint32_t) context->Message_Block[t * 4 + 2]) << 8;
		W[t] |= ((uint32_t) context->Message_Block[t * 4 + 3]);
	}

	for (t = 16; t < 80; t++) {
		W[t] = SHA1_ROTL(1, W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16]);
	}

	A = context->Intermediate_Hash[0];
	B = context->Intermediate_Hash[1];
	C = context->Intermediate_Hash[2];
	D = context->Intermediate_Hash[3];
	E = context->Intermediate_Hash[4];

	for (t = 0; t < 20; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Ch(B, C, D) + E + W[t] + K[0];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	for (t = 20; t < 40; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Parity(B, C, D) + E + W[t] + K[1];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	for (t = 40; t < 60; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Maj(B, C, D) + E + W[t] + K[2];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	for (t = 60; t < 80; t++) {
		temp = SHA1_ROTL(5, A) + SHA_Parity(B, C, D) + E + W[t] + K[3];
		E = D;
		D = C;
		C = SHA1_ROTL(30, B);
		B = A;
		A = temp;
	}

	context->Intermediate_Hash[0] += A;
	context->Intermediate_Hash[1] += B;
	context->Intermediate_Hash[2] += C;
	context->Intermediate_Hash[3] += D;
	context->Intermediate_Hash[4] += E;

	context->Message_Block_Index = 0;
}

/*!
 * \brief This helper function finishes off the digest calculations.
 * \param context [in/out]  The context to pad.
 * \param Pad_Byte [in]  The last byte to add to the message block
 *     before the 0-padding and length.  This will contain the last
 *     bits of the message followed by another single bit.  If the
 *     message was an exact multiple of 8-bits long, Pad_Byte will
 *     be 0x80.
 * \returns sha Error Code.
 */
static void SHA1Finalize(SHA1Context * context, uint8_t Pad_Byte)
{
	int i;
	SHA1PadMessage(context, Pad_Byte);
	/* message may be sensitive, clear it out */
	for (i = 0; i < SHA1_Message_Block_Size; ++i) {
		context->Message_Block[i] = 0;
	}
	context->Length_High = 0;	/* and clear length */
	context->Length_Low = 0;
	context->Computed = 1;
}

/*!
 * \brief Pad message to be 512 bits.
 * \param context [in/out]  The context to pad.
 * \param Pad_Byte [in]  Last padding byte.
 *
 *  According to the standard, the message must be padded to the next
 *  even multiple of 512 bits.  The first padding bit must be a '1'.
 *  The last 64 bits represent the length of the original message.
 *  All bits in between should be 0.  This helper function will pad
 *  the message according to those rules by filling the Message_Block
 *  array accordingly.  When it returns, it can be assumed that the
 *  message digest has been computed.
 *
 * \returns nothing.
 */
static void SHA1PadMessage(SHA1Context * context, uint8_t Pad_Byte)
{
	/*
	 *  Check to see if the current message block is too small to hold
	 *  the initial padding bits and length.  If so, we will pad the
	 *  block, process it, and then continue padding into a second
	 *  block.
	 */
	if (context->Message_Block_Index >= (SHA1_Message_Block_Size - 8)) {
		context->Message_Block[context->Message_Block_Index++] = Pad_Byte;
		while (context->Message_Block_Index < SHA1_Message_Block_Size) {
			context->Message_Block[context->Message_Block_Index++] = 0;
		}

		SHA1ProcessMessageBlock(context);
	} else
		context->Message_Block[context->Message_Block_Index++] = Pad_Byte;

	while (context->Message_Block_Index < (SHA1_Message_Block_Size - 8)) {
		context->Message_Block[context->Message_Block_Index++] = 0;
	}

	/*
	 *  Store the message length as the last 8 octets
	 */
	context->Message_Block[56] = (uint8_t) (context->Length_High >> 24);
	context->Message_Block[57] = (uint8_t) (context->Length_High >> 16);
	context->Message_Block[58] = (uint8_t) (context->Length_High >> 8);
	context->Message_Block[59] = (uint8_t) (context->Length_High);
	context->Message_Block[60] = (uint8_t) (context->Length_Low >> 24);
	context->Message_Block[61] = (uint8_t) (context->Length_Low >> 16);
	context->Message_Block[62] = (uint8_t) (context->Length_Low >> 8);
	context->Message_Block[63] = (uint8_t) (context->Length_Low);

	SHA1ProcessMessageBlock(context);
}
