////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  WjCryptLib_Sha1
//
//  Implementation of SHA1 hash function.
//  Original author:  Steve Reid <sreid@sea-to-sky.net>
//  Contributions by: James H. Brown <jbrown@burgoyne.com>, Saul Kravitz <Saul.Kravitz@celera.com>,
//  and Ralph Giles <giles@ghostscript.com>
//  Modified by WaterJuice retaining Public Domain license.
//
//  This is free and unencumbered software released into the public domain - June 2013 waterjuice.org
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

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

#include "sha1.h"
#include <memory.h>

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  DEFINES
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

// Decide whether to use the Little-Endian shortcut. If the shortcut is not used then the code will work correctly
// on either big or little endian, however if we do know it is a little endian architecture we can speed it up a bit.
// Note, there are TWO places where USE_LITTLE_ENDIAN_SHORTCUT is used. They MUST be paired together.
#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && ( __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ )
    // gcc defines __BYTE_ORDER__ so if it says its little endian we can use that.
    #define USE_LITTLE_ENDIAN_SHORTCUT
#elif defined( _WIN32 )
    // Windows is always little endian so we can use that.
    #define USE_LITTLE_ENDIAN_SHORTCUT
#endif

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  TYPES
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

typedef union
{
    uint8_t     c [64];
    uint32_t    l [16];
} CHAR64LONG16;

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

// Endian neutral macro for loading 32 bit value from 4 byte array (in big endian form).
#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 rol(value, bits) (((value) << (bits)) | ((value) >> (32 - (bits))))

// blk0() and blk() perform the initial expand.
#ifdef USE_LITTLE_ENDIAN_SHORTCUT
    #define blk0(i) (block->l[i] = (rol(block->l[i],24)&0xFF00FF00) | (rol(block->l[i],8)&0x00FF00FF))
#else
    #define blk0(i) block->l[i]
#endif

#define blk(i) (block->l[i&15] = rol(block->l[(i+13)&15] ^ block->l[(i+8)&15] ^ block->l[(i+2)&15] ^ block->l[i&15],1))

// (R0+R1), R2, R3, R4 are the different operations used in SHA1
#define R0(v,w,x,y,z,i)  z += ((w&(x^y))^y)     + blk0(i)+ 0x5A827999 + rol(v,5); w=rol(w,30);
#define R1(v,w,x,y,z,i)  z += ((w&(x^y))^y)     + blk(i) + 0x5A827999 + rol(v,5); w=rol(w,30);
#define R2(v,w,x,y,z,i)  z += (w^x^y)           + blk(i) + 0x6ED9EBA1 + rol(v,5); w=rol(w,30);
#define R3(v,w,x,y,z,i)  z += (((w|x)&y)|(w&x)) + blk(i) + 0x8F1BBCDC + rol(v,5); w=rol(w,30);
#define R4(v,w,x,y,z,i)  z += (w^x^y)           + blk(i) + 0xCA62C1D6 + rol(v,5); w=rol(w,30);

// Loads the 128 bits from ByteArray into WordArray, treating ByteArray as big endian data
#ifdef USE_LITTLE_ENDIAN_SHORTCUT
    #define Load128BitsAsWords( WordArray, ByteArray )  \
        memcpy( WordArray, ByteArray, 64 )
#else
    #define Load128BitsAsWords( WordArray, ByteArray )      \
    {                                                       \
        uint32_t i;                                         \
        for( i=0; i<16; i++ )                               \
        {                                                   \
            LOAD32H( (WordArray)[i], (ByteArray)+(i*4) );   \
        }                                                   \
    }
#endif

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  TransformFunction
//
//  Hash a single 512-bit block. This is the core of the algorithm
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
static
void
    TransformFunction
    (
        uint32_t            state[5],
        uint8_t const       buffer[64]
    )
{
    uint32_t            a;
    uint32_t            b;
    uint32_t            c;
    uint32_t            d;
    uint32_t            e;
    uint8_t             workspace[64];
    CHAR64LONG16*       block = (CHAR64LONG16*) workspace;

    Load128BitsAsWords( block->l, buffer );

    // Copy context->state[] to working vars
    a = state[0];
    b = state[1];
    c = state[2];
    d = state[3];
    e = state[4];

    // 4 rounds of 20 operations each. Loop unrolled.
    R0(a,b,c,d,e, 0); R0(e,a,b,c,d, 1); R0(d,e,a,b,c, 2); R0(c,d,e,a,b, 3);
    R0(b,c,d,e,a, 4); R0(a,b,c,d,e, 5); R0(e,a,b,c,d, 6); R0(d,e,a,b,c, 7);
    R0(c,d,e,a,b, 8); R0(b,c,d,e,a, 9); R0(a,b,c,d,e,10); R0(e,a,b,c,d,11);
    R0(d,e,a,b,c,12); R0(c,d,e,a,b,13); R0(b,c,d,e,a,14); R0(a,b,c,d,e,15);
    R1(e,a,b,c,d,16); R1(d,e,a,b,c,17); R1(c,d,e,a,b,18); R1(b,c,d,e,a,19);
    R2(a,b,c,d,e,20); R2(e,a,b,c,d,21); R2(d,e,a,b,c,22); R2(c,d,e,a,b,23);
    R2(b,c,d,e,a,24); R2(a,b,c,d,e,25); R2(e,a,b,c,d,26); R2(d,e,a,b,c,27);
    R2(c,d,e,a,b,28); R2(b,c,d,e,a,29); R2(a,b,c,d,e,30); R2(e,a,b,c,d,31);
    R2(d,e,a,b,c,32); R2(c,d,e,a,b,33); R2(b,c,d,e,a,34); R2(a,b,c,d,e,35);
    R2(e,a,b,c,d,36); R2(d,e,a,b,c,37); R2(c,d,e,a,b,38); R2(b,c,d,e,a,39);
    R3(a,b,c,d,e,40); R3(e,a,b,c,d,41); R3(d,e,a,b,c,42); R3(c,d,e,a,b,43);
    R3(b,c,d,e,a,44); R3(a,b,c,d,e,45); R3(e,a,b,c,d,46); R3(d,e,a,b,c,47);
    R3(c,d,e,a,b,48); R3(b,c,d,e,a,49); R3(a,b,c,d,e,50); R3(e,a,b,c,d,51);
    R3(d,e,a,b,c,52); R3(c,d,e,a,b,53); R3(b,c,d,e,a,54); R3(a,b,c,d,e,55);
    R3(e,a,b,c,d,56); R3(d,e,a,b,c,57); R3(c,d,e,a,b,58); R3(b,c,d,e,a,59);
    R4(a,b,c,d,e,60); R4(e,a,b,c,d,61); R4(d,e,a,b,c,62); R4(c,d,e,a,b,63);
    R4(b,c,d,e,a,64); R4(a,b,c,d,e,65); R4(e,a,b,c,d,66); R4(d,e,a,b,c,67);
    R4(c,d,e,a,b,68); R4(b,c,d,e,a,69); R4(a,b,c,d,e,70); R4(e,a,b,c,d,71);
    R4(d,e,a,b,c,72); R4(c,d,e,a,b,73); R4(b,c,d,e,a,74); R4(a,b,c,d,e,75);
    R4(e,a,b,c,d,76); R4(d,e,a,b,c,77); R4(c,d,e,a,b,78); R4(b,c,d,e,a,79);

    // Add the working vars back into context.state[]
    state[0] += a;
    state[1] += b;
    state[2] += c;
    state[3] += d;
    state[4] += e;
}

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

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha1Initialise
//
//  Initialises an SHA1 Context. Use this to initialise/reset a context.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha1Initialise
    (
        Sha1Context*        Context         // [out]
    )
{
    // SHA1 initialisation constants
    Context->State[0] = 0x67452301;
    Context->State[1] = 0xEFCDAB89;
    Context->State[2] = 0x98BADCFE;
    Context->State[3] = 0x10325476;
    Context->State[4] = 0xC3D2E1F0;
    Context->Count[0] = 0;
    Context->Count[1] = 0;
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha1Update
//
//  Adds data to the SHA1 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 Sha1Finalise to calculate the hash.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha1Update
    (
        Sha1Context*        Context,        // [in out]
        void  const*        Buffer,         // [in]
        uint32_t            BufferSize      // [in]
    )
{
    uint32_t    i;
    uint32_t    j;

    j = (Context->Count[0] >> 3) & 63;
    if( (Context->Count[0] += BufferSize << 3) < (BufferSize << 3) )
    {
        Context->Count[1]++;
    }

    Context->Count[1] += (BufferSize >> 29);
    if( (j + BufferSize) > 63 )
    {
        i = 64 - j;
        memcpy( &Context->Buffer[j], Buffer, i );
        TransformFunction(Context->State, Context->Buffer);
        for( ; i + 63 < BufferSize; i += 64 )
        {
            TransformFunction(Context->State, (uint8_t*)Buffer + i);
        }
        j = 0;
    }
    else
    {
        i = 0;
    }

    memcpy( &Context->Buffer[j], &((uint8_t*)Buffer)[i], BufferSize - i );
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha1Finalise
//
//  Performs the final calculation of the hash and returns the digest (20 byte buffer containing 160bit hash). After
//  calling this, Sha1Initialised must be used to reuse the context.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha1Finalise
    (
        Sha1Context*        Context,        // [in out]
        SHA1_HASH*          Digest          // [in]
    )
{
    uint32_t    i;
    uint8_t     finalcount[8];

    for( i=0; i<8; i++ )
    {
        finalcount[i] = (unsigned char)((Context->Count[(i >= 4 ? 0 : 1)]
         >> ((3-(i & 3)) * 8) ) & 255);  // Endian independent
    }
    Sha1Update( Context, (uint8_t*)"\x80", 1 );
    while( (Context->Count[0] & 504) != 448 )
    {
        Sha1Update( Context, (uint8_t*)"\0", 1 );
    }

    Sha1Update( Context, finalcount, 8 );  // Should cause a Sha1TransformFunction()
    for( i=0; i<SHA1_HASH_SIZE; i++ )
    {
        Digest->bytes[i] = (uint8_t)((Context->State[i>>2] >> ((3-(i & 3)) * 8) ) & 255);
    }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//  Sha1Calculate
//
//  Combines Sha1Initialise, Sha1Update, and Sha1Finalise into one function. Calculates the SHA1 hash of the buffer.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
void
    Sha1Calculate
    (
        void  const*        Buffer,         // [in]
        uint32_t            BufferSize,     // [in]
        SHA1_HASH*          Digest          // [in]
    )
{
    Sha1Context context;

    Sha1Initialise( &context );
    Sha1Update( &context, Buffer, BufferSize );
    Sha1Finalise( &context, Digest );
}