/*************************************************************************
* Copyright (C) 2010 Intel Corporation
*
* Licensed under the Apache License,  Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* 	http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law  or agreed  to  in  writing,  software
* distributed under  the License  is  distributed  on  an  "AS IS"  BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the  specific  language  governing  permissions  and
* limitations under the License.
*************************************************************************/

/*
//
//  Purpose:
//     Cryptography Primitives.
//     EC over GF(p) Operations
//
//     Context:
//        ippsGFpECSetPointHash()
//
*/

#include "owndefs.h"
#include "owncp.h"
#include "gfpec/pcpgfpecstuff.h"
#include "hash/pcphash.h"
#include "hash/pcphash_rmf.h"

/*F*
// Name: ippsGFpECSetPointHash
//
// Purpose: Constructs a point on an elliptic curve based on the hash of the input message
//
// Returns:                   Reason:
//    ippStsNullPtrErr               pPoint == NULL
//                                   pEC == NULL
//                                   pScratchBuffer == NULL
//                                   (msgLen && !pMsg)
//
//    ippStsContextMatchErr          invalid pEC->idCtx
//                                   invalid pPoint->idCtx
//
//    ippStsBadArgErr                !GFP_IS_BASIC(pGFE)
//
//    ippStsOutOfRangeErr            ECP_POINT_FELEN(pPoint)!=GFP_FELEN()
//
//    ippStsQuadraticNonResidueErr   square of the Y-coordinate of
//                                   the pPoint is a quadratic non-residue modulo
//
//    ippStsLengthErr                msgLen<0
//
//    ippStsNotSupportedModeErr      if algID is not match to supported hash alg
//
//    ippStsNoErr                    no error
//
// Parameters:
//    hdr              Header of the input message
//    pMsg             Pointer to the input message
//    msgLen           Length of the input message
//    pPoint           Pointer to the IppsGFpECPoint context
//    pEC              Pointer to the context of the elliptic curve
//    hashID           ID of the hash algorithm used
//    pScratchBuffer   Pointer to the scratch buffer
//
// Note:
//    Is not a fact that computed point belongs to BP-related subgroup BP
//
*F*/

/* clang-format off */
IPPFUN(IppStatus, ippsGFpECSetPointHash, (Ipp32u hdr,
                                          const Ipp8u* pMsg,
                                          int msgLen,
                                          IppsGFpECPoint* pPoint,
                                          IppsGFpECState* pEC,
                                          IppHashAlgId hashID,
                                          Ipp8u* pScratchBuffer))
/* clang-format on */
{
    IppsGFpState* pGF;
    gsModEngine* pGFE;

    /* get algorithm id */
    hashID = cpValidHashAlg(hashID);
    IPP_BADARG_RET(ippHashAlg_Unknown == hashID, ippStsNotSupportedModeErr);
    /* check if the algorithm is from the sha3 family (SHA3 is not supported in non-rmf methods)*/
    IPP_BADARG_RET(cpIsSHA3AlgID(hashID), ippStsNotSupportedModeErr);

    /* test message length */
    IPP_BADARG_RET((msgLen < 0), ippStsLengthErr);
    /* test message pointer */
    IPP_BADARG_RET((msgLen && !pMsg), ippStsNullPtrErr);

    IPP_BAD_PTR3_RET(pPoint, pEC, pScratchBuffer);
    IPP_BADARG_RET(!VALID_ECP_ID(pEC), ippStsContextMatchErr);

    pGF  = ECP_GFP(pEC);
    pGFE = GFP_PMA(pGF);

    IPP_BADARG_RET(!GFP_IS_BASIC(pGFE), ippStsBadArgErr);
    IPP_BADARG_RET(!ECP_POINT_VALID_ID(pPoint), ippStsContextMatchErr);

    IPP_BADARG_RET(ECP_POINT_FELEN(pPoint) != GFP_FELEN(pGFE), ippStsOutOfRangeErr);

    {
        int elemLen           = GFP_FELEN(pGFE);
        BNU_CHUNK_T* pModulus = GFP_MODULUS(pGFE);

        Ipp8u md[IPP_SHA512_DIGEST_BITSIZE / BYTESIZE];
        int hashLen = cpHashAlgAttr[hashID].hashSize;
        BNU_CHUNK_T hashVal[BITS_BNU_CHUNK(IPP_SHA512_DIGEST_BITSIZE) + 1];
        int hashValLen;

        IppsHashState hashCtx;
        ippsHashInit(&hashCtx, hashID);

        {
            BNU_CHUNK_T* pPoolElm = cpGFpGetPool(1, pGFE);

            /* convert hdr => hdrStr */
            BNU_CHUNK_T locHdr = (BNU_CHUNK_T)hdr;
            Ipp8u hdrOctStr[sizeof(hdr /*locHdr*/)];
            cpToOctStr_BNU(hdrOctStr, sizeof(hdrOctStr), &locHdr, 1);

            /* compute md = hash(hrd||msg) */
            ippsHashUpdate(hdrOctStr, sizeof(hdrOctStr), &hashCtx);
            ippsHashUpdate(pMsg, msgLen, &hashCtx);
            ippsHashFinal(md, &hashCtx);

            /* convert hash into the integer */
            hashValLen = cpFromOctStr_BNU(hashVal, md, hashLen);
            hashValLen = cpMod_BNU(hashVal, hashValLen, pModulus, elemLen);
            cpGFpSet(pPoolElm, hashVal, hashValLen, pGFE);

            if (gfec_MakePoint(pPoint, pPoolElm, pEC)) {
                /* choose even y-coordinate of the point (see SafeID Specs v2) */
                BNU_CHUNK_T* pY = ECP_POINT_Y(pPoint);

                /* due to P(X,Y,Z=1) just decode Y->y */
                GFP_METHOD(pGFE)->decode(pPoolElm, pY, pGFE);
                if (pPoolElm[0] & 1)
                    cpGFpNeg(pY, pY, pGFE);

                /* R = [cofactor]R */
                if (ECP_SUBGROUP(pEC)) {
                    BNU_CHUNK_T* pCofactor = ECP_COFACTOR(pEC);
                    int cofactorLen        = GFP_FELEN(pGFE);
                    if (!GFP_IS_ONE(pCofactor, cofactorLen))
                        gfec_MulPoint(pPoint,
                                      pPoint,
                                      pCofactor,
                                      cofactorLen,
                                      /*0,*/ pEC,
                                      pScratchBuffer);
                }

                cpGFpReleasePool(1, pGFE);
                return ippStsNoErr;
            }
        }

        cpGFpReleasePool(1, pGFE);
        return ippStsQuadraticNonResidueErr;
    }
}
