text: /*******************************************************************************
  * Copyright 2013-2020 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 Primitive.
  //     SMS4 encryption/decryption
  // 
  //  Contents:
  //        ippsSMS4EncryptCBC_CS3()
  //
  */
  
  #include "owncp.h"
  #include "pcpsms4.h"
  #include "pcptool.h"
  #include "pcpsms4_encrypt_cbc.h"
  
  /*F*
  //    Name: ippsSMS4EncryptCBC_CS3
  //
  // Purpose: SMS4-CBC-CS3 encryption.
  //
  // Returns:                Reason:
  //    ippStsNullPtrErr        pCtx == NULL
  //                            pSrc == NULL
  //                            pDst == NULL
  //                            pIV  == NULL
  //    ippStsContextMatchErr   !VALID_SMS4_ID()
  //    ippStsLengthErr         len <=MBS_SMS4 (different from CS1 and CS2)
  //    ippStsNoErr             no errors
  //
  // Parameters:
  //    pSrc        pointer to the source data buffer
  //    pDst        pointer to the target data buffer
  //    len         input/output buffer length (in bytes)
  //    pCtx        pointer to the SMS4 context
  //    pIV         pointer to the initialization vector
  //
  // Note:
  // - CS3 correponds to definitions spcified for Kerberos 3 in RFC2040 and RFC3962
  // - C*[n-2] and C[n-1] are unconditionally swapped, even if C*[n-2] is a complete block
  // - Therefore, CBC-CS3 is not strictly an extensioin of usual CBC mode
  //
  *F*/
  IPPFUN(IppStatus, ippsSMS4EncryptCBC_CS3,(const Ipp8u* pSrc, Ipp8u* pDst, int len,
                                            const IppsSMS4Spec* pCtx,
                                            const Ipp8u* pIV))
  {
     /* test context */
     IPP_BAD_PTR1_RET(pCtx);
     /* test the context ID */
     IPP_BADARG_RET(!VALID_SMS4_ID(pCtx), ippStsContextMatchErr);
  
     /* test source, target buffers and initialization pointers */
     IPP_BAD_PTR3_RET(pSrc, pIV, pDst);
     /* test stream length */
     IPP_BADARG_RET((len<=MBS_SMS4), ippStsLengthErr);
  
     {
        int tail = len & (MBS_SMS4-1); /* length of the last partial block */
        if(0==tail)
           tail = MBS_SMS4;
        len -= tail;
  
        /* encryption of complete blocks */
        cpEncryptSMS4_cbc(pIV, pSrc, pDst, len, pCtx);
        pSrc += len;
        pDst += len;
  
        {
           __ALIGN16 Ipp8u TMP[2*MBS_SMS4];
  
           /*
              lastIV     size = MBS_SMS4
              lastEncBlk size = MBS_SMS4
           */
  
           Ipp8u*     lastIV = TMP;
           Ipp8u* lastEncBlk = TMP + MBS_SMS4;
  
           int n;
  
           CopyBlock16(pDst-MBS_SMS4, lastIV);
           CopyBlock16(pDst-MBS_SMS4, lastEncBlk);
           for(n=0; n<tail; n++)
              lastIV[n] ^= pSrc[n];
  
           /* encrypt last padded block */
           cpSMS4_Cipher(pDst-MBS_SMS4, lastIV, SMS4_RK(pCtx));
  
           CopyBlock(lastEncBlk, pDst, tail);
  
           /* clear secret data */
           PurgeBlock(TMP, sizeof(TMP));
        }
  
        return ippStsNoErr;
     }
  }
  