/*

    File:       DiffieHellman.cpp

        Contains:   Diffie-Hellman key exchange example.        

        Copyright:  © Copyright 2002 Apple Computer, Inc. All rights reserved.

    Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.

                        ("Apple") in consideration of your agreement to the following terms, and your

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                        please do not use, install, modify or redistribute this Apple software.

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                        to these terms, Apple grants you a personal, non-exclusive license, under AppleÕs

                        copyrights in this original Apple software (the "Apple Software"), to use,

                        reproduce, modify and redistribute the Apple Software, with or without

                        modifications, in source and/or binary forms; provided that if you redistribute

                        the Apple Software in its entirety and without modifications, you must retain

                        this notice and the following text and disclaimers in all such redistributions of

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                        Apple Computer, Inc. may be used to endorse or promote products derived from the

                        Apple Software without specific prior written permission from Apple.  Except as

                        expressly stated in this notice, no other rights or licenses, express or implied,

                        are granted by Apple herein, including but not limited to any patent rights that

                        may be infringed by your derivative works or by other works in which the Apple

                        Software may be incorporated.

                        The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO

                        WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED

                        WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR

                        PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN

                        COMBINATION WITH YOUR PRODUCTS.

                        IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR

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    Change History (most recent first):

                11/4/02     1.0d1

*/

#include <libCdsaCrypt/libCdsaCrypt.h>

#include <libCdsaCrypt/fileIo.h>

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#define DH_KEY_SIZE     512     /* size of Diffie-Hellman key in bits */

#define DERIVE_KEY_SIZE 128     /* size of derived key in bits */

#define DERIVE_KEY_ALG  CSSM_ALGID_AES

static void usage(char **argv)

{

    printf("usage: \n");

    printf("usage: %s i=paramBlobFile     uses precalculated parameters\n",

            argv[0]);

    printf("usage: %s o=paramBlobFile     calculates and writes parameters\n",

            argv[0]);

    exit(1);

}

/*

 * Encrypt ptext with myDeriveKey ==> ctext

 * decrypt ctext with theirDeriveKey ==> rptext

 * ensure ptext == rptext

 */  

static int doEncryptTest(

    CSSM_CSP_HANDLE     cspHandle,

    const CSSM_DATA     *ptext,

    CSSM_KEY_PTR        myDeriveKey,

    CSSM_KEY_PTR        theirDeriveKey)

{

    CSSM_DATA ctext = {0, NULL};

    CSSM_DATA rptext = {0, NULL};

    CSSM_RETURN crtn;

    /* encrypt with our derived key */

    crtn = cdsaEncrypt(cspHandle,

        myDeriveKey,

        ptext,

        &ctext);

    if(crtn) {

        cssmPerror("cdsaEncrypt", crtn);

        return -1;

    }

    /* decrypt with their derived key */

    crtn = cdsaDecrypt(cspHandle,

        theirDeriveKey,

        &ctext,

        &rptext);

    if(crtn) {

        cssmPerror("cdsaDecrypt", crtn);

        return -1;

    }

    /* verify */

    if((ptext->Length != rptext.Length) ||

       memcmp(ptext->Data, rptext.Data, ptext->Length)) {

        printf("***DATA MISCOMPARE***\n");

        return -1;

    }

    /* free data allocated by CSP */

    free(ctext.Data);

    free(rptext.Data);

    return 0;

}

/*

 * Generate two Diffie-Hellman key pairs using the same algorithm parameters. 

 * Derive two symmetric keys using D-H key exchange.

 * Encrypt with one symmetric key, decrypt with the other, ensure match.

 */

static int doTest(

    CSSM_CSP_HANDLE     cspHandle,

    const CSSM_DATA     *ptext,

    const CSSM_DATA     *inParams,      // optional

    CSSM_DATA_PTR       outParams,      // optional

    uint32              keySizeInBits)  // Diffie-HEllman keys

{

    CSSM_KEY    myPriv;

    CSSM_KEY    myPub;

    CSSM_KEY    theirPriv;

    CSSM_KEY    theirPub;

    int         rtn = 0;

    CSSM_RETURN crtn;

    if(outParams) {

        printf("Generating Diffie-Hellman parameters and key pairs...\n");

    }

    else {

        printf("Generating Diffie-Hellman key pairs...\n");

    }

    crtn = cdsaDhGenerateKeyPair(cspHandle,

        &myPub,

        &myPriv,

        keySizeInBits,

        inParams,

        outParams);

    if(crtn) {

        cssmPerror("cdsaDhGenerateKeyPair", crtn);

        return -1;

    }

    /* 

     * Note the params for the second key pair MUST match the 

     * params either specified or generated in previous call.

     */

    if((inParams == NULL) && (outParams == NULL)) {

        printf("***Must provide a way to match D-H parameters!\n");

        exit(1);

    }

    const CSSM_DATA *theParams = inParams;

    if(theParams == NULL) {

        theParams = outParams;

    }

    crtn = cdsaDhGenerateKeyPair(cspHandle,

        &theirPub,

        &theirPriv,

        keySizeInBits,

        theParams,          // inParams

        NULL);              // outParams

    if(crtn) {

        cssmPerror("cdsaDhGenerateKeyPair", crtn);

        return -1;

    }

    /* derive two symmetric keys */

    printf("Performing Diffie-Hellman key exchange...\n");

    CSSM_KEY myDerive;

    CSSM_KEY theirDerive;

    crtn = cdsaDhKeyExchange(cspHandle,

        &myPriv,

        theirPub.KeyData.Data,

        theirPub.KeyData.Length,

        &myDerive,

        DERIVE_KEY_SIZE,

        DERIVE_KEY_ALG);

    if(crtn) {

        cssmPerror("cdsaDhKeyExchange", crtn);

        return -1;

    }

    crtn = cdsaDhKeyExchange(cspHandle,

        &theirPriv,

        myPub.KeyData.Data,

        myPub.KeyData.Length,

        &theirDerive,

        DERIVE_KEY_SIZE,

        DERIVE_KEY_ALG);

    if(crtn) {

        cssmPerror("cdsaDhKeyExchange", crtn);

        return -1;

    }

    /*

     * Encrypt plaintext with myDerive

     * decrypt with theirDerive

     * verify result of decryption matches original plaintext 

     */

    printf("Verifying key exchange...\n");

    rtn = doEncryptTest(cspHandle,

        ptext,

        &myDerive,

        &theirDerive);

    /* Free resources */

    cdsaFreeKey(cspHandle, &myPub);

    cdsaFreeKey(cspHandle, &myPriv);

    cdsaFreeKey(cspHandle, &theirPub);

    cdsaFreeKey(cspHandle, &theirPriv);

    cdsaFreeKey(cspHandle, &myDerive);

    cdsaFreeKey(cspHandle, &theirDerive);

    return rtn;

}

int main(int argc, char **argv)

{

    CSSM_CSP_HANDLE         cspHandle;

    CSSM_DATA               inParams = {0, NULL};

    CSSM_DATA               outParams = {0, NULL};

    CSSM_DATA_PTR           inParamPtr = NULL;

    CSSM_DATA_PTR           outParamPtr = NULL;

    CSSM_DATA               ptext;

    char                    *inFileName = NULL;

    char                    *outFileName = NULL;

    CSSM_RETURN             crtn;

    int                     irtn;

    if(argc != 2) {

        usage(argv);

    }

    switch(argv[1][0]) {

        case 'i':

            inFileName = &argv[1][2];

            break;

        case 'o':

            outFileName = &argv[1][2];

            break;

        default:

            usage(argv);

    }

    crtn = cdsaCspAttach(&cspHandle);

    if(crtn) {

        cssmPerror("Attach to CSP", crtn);

        exit(1);

    }

    /* optionally fetch algorithm parameters from a file */

    if(inFileName) {

        irtn = readFile(inFileName, &inParams.Data, 

            (unsigned *)&inParams.Length);

        if(irtn) {

            printf("***Can't read parameters from %s; aborting.\n",

                inFileName);

            exit(1);

        }

        /* constant from now on */

        inParamPtr = &inParams;

    }

    else {

        /* no user-supplied parameters; generate and save in outParams */

        outParamPtr = &outParams;

    }

    ptext.Data = (uint8 *)"Some random plaintext to carefully"

        "encrypt and recover";

    ptext.Length = strlen((char *)ptext.Data);

    irtn = doTest(cspHandle, 

        &ptext,

        inParamPtr, 

        outParamPtr, 

        DH_KEY_SIZE);

    if(irtn == 0) {

        /* test was successful */

        if(outParamPtr) {

            /* write generated params to file */

            irtn = writeFile(outFileName, outParams.Data, outParams.Length);

            if(irtn) {

                printf("***Error writing params to %s.\n",  outFileName);

            }

            else {

                printf("...wrote %u bytes to %s\n", 

                        (unsigned)outParams.Length, outFileName);

            }

        }

    }

    CSSM_ModuleDetach(cspHandle);

    if(irtn == 0) {

        printf("Diffie-Hellman test complete.\n");

    }

    else {

        printf("Diffie-Hellman test failed.\n");

    }

    return 0;

}