/*
 *  sha1.c
 *
 *  Copyright (C) 1998, 2009
 *  Paul E. Jones <paulej@packetizer.com>
 *  All Rights Reserved
 *
 *****************************************************************************
 *  $Id: sha1.c 12 2009-06-22 19:34:25Z paulej $
 *****************************************************************************
 *
 *  Description:
 *      This file implements the Secure Hashing Standard as defined
 *      in FIPS PUB 180-1 published April 17, 1995.
 *
 *      The Secure Hashing Standard, which uses the Secure Hashing
 *      Algorithm (SHA), produces a 160-bit message digest for a
 *      given data stream.  In theory, it is highly improbable that
 *      two messages will produce the same message digest.  Therefore,
 *      this algorithm 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 was
 *      written with the expectation that the processor has at least
 *      a 32-bit machine word size.  If the machine word size is larger,
 *      the code should still function properly.  One caveat to that
 *      is that the input functions taking characters and character
 *      arrays assume that only 8 bits of information are stored in each
 *      character.
 *
 *  Caveats:
 *      SHA-1 is designed to work with messages less than 2^64 bits
 *      long. Although SHA-1 allows a message digest to be generated for
 *      messages of any number of bits less than 2^64, this
 *      implementation only works with messages with a length that is a
 *      multiple of the size of an 8-bit character.
 *
 */

#include "sha1.h"

/*
 *  Define the circular shift macro
 */
#define SHA1CircularShift(bits, word) ((((word) << (bits)) & 0xFFFFFFFF) | ((word) >> (32 - (bits))))

namespace DotNetPELib
{
/* Function prototypes */
void SHA1ProcessMessageBlock(SHA1Context*);
void SHA1PadMessage(SHA1Context*);

/*
 *  SHA1Reset
 *
 *  Description:
 *      This function will initialize the SHA1Context in preparation
 *      for computing a new message digest.
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to reset.
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1Reset(SHA1Context* context)
{
    context->Length_Low = 0;
    context->Length_High = 0;
    context->Message_Block_Index = 0;

    context->Message_Digest[0] = 0x67452301;
    context->Message_Digest[1] = 0xEFCDAB89;
    context->Message_Digest[2] = 0x98BADCFE;
    context->Message_Digest[3] = 0x10325476;
    context->Message_Digest[4] = 0xC3D2E1F0;

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

/*
 *  SHA1Result
 *
 *  Description:
 *      This function will return the 160-bit message digest into the
 *      Message_Digest array within the SHA1Context provided
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to use to calculate the SHA-1 hash.
 *
 *  Returns:
 *      1 if successful, 0 if it failed.
 *
 *  Comments:
 *
 */
int SHA1Result(SHA1Context* context)
{

    if (context->Corrupted)
    {
        return 0;
    }

    if (!context->Computed)
    {
        SHA1PadMessage(context);
        context->Computed = 1;
        // rearrange for littleendian processors
        for (int i = 0; i < 5; i++)
        {
            unsigned n = context->Message_Digest[i];
            int n1 = 0;
            n1 = (n >> 24) + ((n >> 8) & 0xff00) + ((n << 8) & 0xff0000) + (n << 24);
            context->Message_Digest[i] = n1;
        }
    }

    return 1;
}

/*
 *  SHA1Input
 *
 *  Description:
 *      This function accepts an array of octets as the next portion of
 *      the message.
 *
 *  Parameters:
 *      context: [in/out]
 *          The SHA-1 context to update
 *      message_array: [in]
 *          An array of characters representing the next portion of the
 *          message.
 *      length: [in]
 *          The length of the message in message_array
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1Input(SHA1Context* context, const unsigned char* message_array, unsigned length)
{
    if (!length)
    {
        return;
    }

    if (context->Computed || context->Corrupted)
    {
        context->Corrupted = 1;
        return;
    }

    while (length-- && !context->Corrupted)
    {
        context->Message_Block[context->Message_Block_Index++] = (*message_array & 0xFF);

        context->Length_Low += 8;
        /* Force it to 32 bits */
        context->Length_Low &= 0xFFFFFFFF;
        if (context->Length_Low == 0)
        {
            context->Length_High++;
            /* Force it to 32 bits */
            context->Length_High &= 0xFFFFFFFF;
            if (context->Length_High == 0)
            {
                /* Message is too long */
                context->Corrupted = 1;
            }
        }

        if (context->Message_Block_Index == 64)
        {
            SHA1ProcessMessageBlock(context);
        }

        message_array++;
    }
}

/*
 *  SHA1ProcessMessageBlock
 *
 *  Description:
 *      This function will process the next 512 bits of the message
 *      stored in the Message_Block array.
 *
 *  Parameters:
 *      None.
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *      Many of the variable names in the SHAContext, especially the
 *      single character names, were used because those were the names
 *      used in the publication.
 *
 *
 */
void SHA1ProcessMessageBlock(SHA1Context* context)
{
    const unsigned K[] = /* Constants defined in SHA-1   */
        {0x5A827999, 0x6ED9EBA1, 0x8F1BBCDC, 0xCA62C1D6};
    int t;                  /* Loop counter                 */
    unsigned temp;          /* Temporary word value         */
    unsigned W[80];         /* Word sequence                */
    unsigned A, B, C, D, E; /* Word buffers                 */

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

    for (t = 16; t < 80; t++)
    {
        W[t] = SHA1CircularShift(1, W[t - 3] ^ W[t - 8] ^ W[t - 14] ^ W[t - 16]);
    }

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

    for (t = 0; t < 20; t++)
    {
        temp = SHA1CircularShift(5, A) + ((B & C) | ((~B) & D)) + E + W[t] + K[0];
        temp &= 0xFFFFFFFF;
        E = D;
        D = C;
        C = SHA1CircularShift(30, B);
        B = A;
        A = temp;
    }

    for (t = 20; t < 40; t++)
    {
        temp = SHA1CircularShift(5, A) + (B ^ C ^ D) + E + W[t] + K[1];
        temp &= 0xFFFFFFFF;
        E = D;
        D = C;
        C = SHA1CircularShift(30, B);
        B = A;
        A = temp;
    }

    for (t = 40; t < 60; t++)
    {
        temp = SHA1CircularShift(5, A) + ((B & C) | (B & D) | (C & D)) + E + W[t] + K[2];
        temp &= 0xFFFFFFFF;
        E = D;
        D = C;
        C = SHA1CircularShift(30, B);
        B = A;
        A = temp;
    }

    for (t = 60; t < 80; t++)
    {
        temp = SHA1CircularShift(5, A) + (B ^ C ^ D) + E + W[t] + K[3];
        temp &= 0xFFFFFFFF;
        E = D;
        D = C;
        C = SHA1CircularShift(30, B);
        B = A;
        A = temp;
    }

    context->Message_Digest[0] = (context->Message_Digest[0] + A) & 0xFFFFFFFF;
    context->Message_Digest[1] = (context->Message_Digest[1] + B) & 0xFFFFFFFF;
    context->Message_Digest[2] = (context->Message_Digest[2] + C) & 0xFFFFFFFF;
    context->Message_Digest[3] = (context->Message_Digest[3] + D) & 0xFFFFFFFF;
    context->Message_Digest[4] = (context->Message_Digest[4] + E) & 0xFFFFFFFF;

    context->Message_Block_Index = 0;
}

/*
 *  SHA1PadMessage
 *
 *  Description:
 *      According to the standard, the message must be padded to an even
 *      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 function will pad the message
 *      according to those rules by filling the Message_Block array
 *      accordingly.  It will also call SHA1ProcessMessageBlock()
 *      appropriately.  When it returns, it can be assumed that the
 *      message digest has been computed.
 *
 *  Parameters:
 *      context: [in/out]
 *          The context to pad
 *
 *  Returns:
 *      Nothing.
 *
 *  Comments:
 *
 */
void SHA1PadMessage(SHA1Context* context)
{
    /*
     *  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 > 55)
    {
        context->Message_Block[context->Message_Block_Index++] = 0x80;
        while (context->Message_Block_Index < 64)
        {
            context->Message_Block[context->Message_Block_Index++] = 0;
        }

        SHA1ProcessMessageBlock(context);

        while (context->Message_Block_Index < 56)
        {
            context->Message_Block[context->Message_Block_Index++] = 0;
        }
    }
    else
    {
        context->Message_Block[context->Message_Block_Index++] = 0x80;
        while (context->Message_Block_Index < 56)
        {
            context->Message_Block[context->Message_Block_Index++] = 0;
        }
    }

    /*
     *  Store the message length as the last 8 octets
     */
    context->Message_Block[56] = (context->Length_High >> 24) & 0xFF;
    context->Message_Block[57] = (context->Length_High >> 16) & 0xFF;
    context->Message_Block[58] = (context->Length_High >> 8) & 0xFF;
    context->Message_Block[59] = (context->Length_High) & 0xFF;
    context->Message_Block[60] = (context->Length_Low >> 24) & 0xFF;
    context->Message_Block[61] = (context->Length_Low >> 16) & 0xFF;
    context->Message_Block[62] = (context->Length_Low >> 8) & 0xFF;
    context->Message_Block[63] = (context->Length_Low) & 0xFF;

    SHA1ProcessMessageBlock(context);
}

}  // namespace DotNetPELib