////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  WjCryptLib_Sha256
//
//  Implementation of SHA256 hash function.
//  Original author: Tom St Denis, tomstdenis@gmail.com, http://libtom.org
//  Modified by WaterJuice retaining Public Domain license.
//
//  This is free and unencumbered software released into the public domain - June 2013 waterjuice.org
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  IMPORTS
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#include "sha256.h"
#include <memory.h>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  MACROS
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

#define ror(value, bits) (((value) >> (bits)) | ((value) << (32 - (bits))))

#define MIN(x, y) ( ((x)<(y))?(x):(y) )

#define STORE32H(x, y)                                                                     \
     { (y)[0] = (uint8_t)(((x)>>24)&255); (y)[1] = (uint8_t)(((x)>>16)&255);   \
       (y)[2] = (uint8_t)(((x)>>8)&255); (y)[3] = (uint8_t)((x)&255); }

#define LOAD32H(x, y)                            \
     { x = ((uint32_t)((y)[0] & 255)<<24) | \
           ((uint32_t)((y)[1] & 255)<<16) | \
           ((uint32_t)((y)[2] & 255)<<8)  | \
           ((uint32_t)((y)[3] & 255)); }

#define STORE64H(x, y)                                                                     \
   { (y)[0] = (uint8_t)(((x)>>56)&255); (y)[1] = (uint8_t)(((x)>>48)&255);     \
     (y)[2] = (uint8_t)(((x)>>40)&255); (y)[3] = (uint8_t)(((x)>>32)&255);     \
     (y)[4] = (uint8_t)(((x)>>24)&255); (y)[5] = (uint8_t)(((x)>>16)&255);     \
     (y)[6] = (uint8_t)(((x)>>8)&255); (y)[7] = (uint8_t)((x)&255); }

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  CONSTANTS
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

// The K array
static const uint32_t K[64] = {
    0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL, 0x3956c25bUL,
    0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL, 0xd807aa98UL, 0x12835b01UL,
    0x243185beUL, 0x550c7dc3UL, 0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL,
    0xc19bf174UL, 0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL,
    0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL, 0x983e5152UL,
    0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL, 0xc6e00bf3UL, 0xd5a79147UL,
    0x06ca6351UL, 0x14292967UL, 0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL,
    0x53380d13UL, 0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
    0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL, 0xd192e819UL,
    0xd6990624UL, 0xf40e3585UL, 0x106aa070UL, 0x19a4c116UL, 0x1e376c08UL,
    0x2748774cUL, 0x34b0bcb5UL, 0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL,
    0x682e6ff3UL, 0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
    0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL
};

#define BLOCK_SIZE          64

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  INTERNAL FUNCTIONS
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

// Various logical functions
#define Ch( x, y, z )     (z ^ (x & (y ^ z)))
#define Maj( x, y, z )    (((x | y) & z) | (x & y))
#define S( x, n )         ror((x),(n))
#define R( x, n )         (((x)&0xFFFFFFFFUL)>>(n))
#define Sigma0( x )       (S(x, 2) ^ S(x, 13) ^ S(x, 22))
#define Sigma1( x )       (S(x, 6) ^ S(x, 11) ^ S(x, 25))
#define Gamma0( x )       (S(x, 7) ^ S(x, 18) ^ R(x, 3))
#define Gamma1( x )       (S(x, 17) ^ S(x, 19) ^ R(x, 10))

#define Sha256Round( a, b, c, d, e, f, g, h, i )       \
     t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[i];   \
     t1 = Sigma0(a) + Maj(a, b, c);                    \
     d += t0;                                          \
     h  = t0 + t1;

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  TransformFunction
//
//  Compress 512-bits
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
static
void
    TransformFunction
    (
        Sha256Context*      Context,
        uint8_t const*      Buffer
    )
{
    uint32_t    S[8];
    uint32_t    W[64];
    uint32_t    t0;
    uint32_t    t1;
    uint32_t    t;
    int         i;

    // Copy state into S
    for( i=0; i<8; i++ )
    {
        S[i] = Context->state[i];
    }

    // Copy the state into 512-bits into W[0..15]
    for( i=0; i<16; i++ )
    {
        LOAD32H( W[i], Buffer + (4*i) );
    }

    // Fill W[16..63]
    for( i=16; i<64; i++ )
    {
        W[i] = Gamma1( W[i-2]) + W[i-7] + Gamma0( W[i-15] ) + W[i-16];
    }

    // Compress
    for( i=0; i<64; i++ )
    {
        Sha256Round( S[0], S[1], S[2], S[3], S[4], S[5], S[6], S[7], i );
        t = S[7];
        S[7] = S[6];
        S[6] = S[5];
        S[5] = S[4];
        S[4] = S[3];
        S[3] = S[2];
        S[2] = S[1];
        S[1] = S[0];
        S[0] = t;
    }

    // Feedback
    for( i=0; i<8; i++ )
    {
        Context->state[i] = Context->state[i] + S[i];
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  PUBLIC FUNCTIONS
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha256Initialise
//
//  Initialises a SHA256 Context. Use this to initialise/reset a context.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha256Initialise
    (
        Sha256Context*      Context         // [out]
    )
{
    Context->curlen = 0;
    Context->length = 0;
    Context->state[0] = 0x6A09E667UL;
    Context->state[1] = 0xBB67AE85UL;
    Context->state[2] = 0x3C6EF372UL;
    Context->state[3] = 0xA54FF53AUL;
    Context->state[4] = 0x510E527FUL;
    Context->state[5] = 0x9B05688CUL;
    Context->state[6] = 0x1F83D9ABUL;
    Context->state[7] = 0x5BE0CD19UL;
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha256Update
//
//  Adds data to the SHA256 context. This will process the data and update the internal state of the context. Keep on
//  calling this function until all the data has been added. Then call Sha256Finalise to calculate the hash.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha256Update
    (
        Sha256Context*      Context,        // [in out]
        void const*         Buffer,         // [in]
        uint32_t            BufferSize      // [in]
    )
{
    uint32_t n;

    if( Context->curlen > sizeof(Context->buf) )
    {
       return;
    }

    while( BufferSize > 0 )
    {
        if( Context->curlen == 0 && BufferSize >= BLOCK_SIZE )
        {
           TransformFunction( Context, (uint8_t*)Buffer );
           Context->length += BLOCK_SIZE * 8;
           Buffer = (uint8_t*)Buffer + BLOCK_SIZE;
           BufferSize -= BLOCK_SIZE;
        }
        else
        {
           n = MIN( BufferSize, (BLOCK_SIZE - Context->curlen) );
           memcpy( Context->buf + Context->curlen, Buffer, (size_t)n );
           Context->curlen += n;
           Buffer = (uint8_t*)Buffer + n;
           BufferSize -= n;
           if( Context->curlen == BLOCK_SIZE )
           {
              TransformFunction( Context, Context->buf );
              Context->length += 8*BLOCK_SIZE;
              Context->curlen = 0;
           }
       }
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha256Finalise
//
//  Performs the final calculation of the hash and returns the digest (32 byte buffer containing 256bit hash). After
//  calling this, Sha256Initialised must be used to reuse the context.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha256Finalise
    (
        Sha256Context*      Context,        // [in out]
        SHA256_HASH*        Digest          // [out]
    )
{
    int i;

    if( Context->curlen >= sizeof(Context->buf) )
    {
       return;
    }

    // Increase the length of the message
    Context->length += Context->curlen * 8;

    // Append the '1' bit
    Context->buf[Context->curlen++] = (uint8_t)0x80;

    // if the length is currently above 56 bytes we append zeros
    // then compress.  Then we can fall back to padding zeros and length
    // encoding like normal.
    if( Context->curlen > 56 )
    {
        while( Context->curlen < 64 )
        {
            Context->buf[Context->curlen++] = (uint8_t)0;
        }
        TransformFunction(Context, Context->buf);
        Context->curlen = 0;
    }

    // Pad up to 56 bytes of zeroes
    while( Context->curlen < 56 )
    {
        Context->buf[Context->curlen++] = (uint8_t)0;
    }

    // Store length
    STORE64H( Context->length, Context->buf+56 );
    TransformFunction( Context, Context->buf );

    // Copy output
    for( i=0; i<8; i++ )
    {
        STORE32H( Context->state[i], Digest->bytes+(4*i) );
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha256Calculate
//
//  Combines Sha256Initialise, Sha256Update, and Sha256Finalise into one function. Calculates the SHA256 hash of the
//  buffer.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha256Calculate
    (
        void  const*        Buffer,         // [in]
        uint32_t            BufferSize,     // [in]
        SHA256_HASH*        Digest          // [in]
    )
{
    Sha256Context context;

    Sha256Initialise( &context );
    Sha256Update( &context, Buffer, BufferSize );
    Sha256Finalise( &context, Digest );
}