/*
 * Demo of how to construct your own engine and using it.  The basis of this
 * engine is RSAref, an old reference of the RSA algorithm which can still be
 * found a little here and there.
 */

#include <stdio.h>
#include <string.h>
#include "./source/global.h"
#include "./source/rsaref.h"
#include "./source/rsa.h"
#include "./source/des.h"
#include <openssl/err.h>
#define OPENSSL_NO_MD2
#define OPENSSL_NO_MD5
#include <openssl/evp.h>
#include <openssl/bn.h>
#include <openssl/engine.h>

#define RSAREF_LIB_NAME "rsaref engine"
#include "rsaref_err.c"

/*****************************************************************************
 *** Function declarations and global variable definitions                 ***
 *****************************************************************************/

/*****************************************************************************
 * Constants used when creating the ENGINE
 **/
static const char *engine_rsaref_id = "rsaref";
static const char *engine_rsaref_name = "RSAref engine support";

/*****************************************************************************
 * Functions to handle the engine
 **/
static int rsaref_destroy(ENGINE *e);
static int rsaref_init(ENGINE *e);
static int rsaref_finish(ENGINE *e);

/*****************************************************************************
 * Engine commands
 **/
static const ENGINE_CMD_DEFN rsaref_cmd_defns[] = {
    {0, NULL, NULL, 0}
};

/*****************************************************************************
 * RSA functions
 **/
static int rsaref_private_decrypt(int len, const unsigned char *from,
                                  unsigned char *to, RSA *rsa, int padding);
static int rsaref_private_encrypt(int len, const unsigned char *from,
                                  unsigned char *to, RSA *rsa, int padding);
static int rsaref_public_encrypt(int len, const unsigned char *from,
                                 unsigned char *to, RSA *rsa, int padding);
static int rsaref_public_decrypt(int len, const unsigned char *from,
                                 unsigned char *to, RSA *rsa, int padding);
static int bnref_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
static int rsaref_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa);

/*****************************************************************************
 * Our RSA method
 **/
static RSA_METHOD rsaref_rsa = {
    "RSAref PKCS#1 RSA",
    rsaref_public_encrypt,
    rsaref_public_decrypt,
    rsaref_private_encrypt,
    rsaref_private_decrypt,
    rsaref_mod_exp,
    bnref_mod_exp,
    NULL,
    NULL,
    0,
    NULL,
    NULL,
    NULL
};

/*****************************************************************************
 * Symetric cipher and digest function registrars
 **/
static int rsaref_ciphers(ENGINE *e, const EVP_CIPHER **cipher,
                          const int **nids, int nid);
static int rsaref_digests(ENGINE *e, const EVP_MD **digest,
                          const int **nids, int nid);

static int rsaref_cipher_nids[] =
    { NID_des_cbc, NID_des_ede3_cbc, NID_desx_cbc, 0 };
static int rsaref_digest_nids[] = { NID_md2, NID_md5, 0 };

/*****************************************************************************
 * DES functions
 **/
static int cipher_des_cbc_init(EVP_CIPHER_CTX *ctx, const unsigned char *key,
                               const unsigned char *iv, int enc);
static int cipher_des_cbc_code(EVP_CIPHER_CTX *ctx, unsigned char *out,
                               const unsigned char *in, unsigned int inl);
static int cipher_des_cbc_clean(EVP_CIPHER_CTX *);
static int cipher_des_ede3_cbc_init(EVP_CIPHER_CTX *ctx,
                                    const unsigned char *key,
                                    const unsigned char *iv, int enc);
static int cipher_des_ede3_cbc_code(EVP_CIPHER_CTX *ctx, unsigned char *out,
                                    const unsigned char *in,
                                    unsigned int inl);
static int cipher_des_ede3_cbc_clean(EVP_CIPHER_CTX *);
static int cipher_desx_cbc_init(EVP_CIPHER_CTX *ctx, const unsigned char *key,
                                const unsigned char *iv, int enc);
static int cipher_desx_cbc_code(EVP_CIPHER_CTX *ctx, unsigned char *out,
                                const unsigned char *in, unsigned int inl);
static int cipher_desx_cbc_clean(EVP_CIPHER_CTX *);

/*****************************************************************************
 * Our DES ciphers
 **/
static const EVP_CIPHER cipher_des_cbc = {
    NID_des_cbc,
    8, 8, 8,
    0 | EVP_CIPH_CBC_MODE,
    cipher_des_cbc_init,
    cipher_des_cbc_code,
    cipher_des_cbc_clean,
    sizeof(DES_CBC_CTX),
    NULL,
    NULL,
    NULL,
    NULL
};

static const EVP_CIPHER cipher_des_ede3_cbc = {
    NID_des_ede3_cbc,
    8, 24, 8,
    0 | EVP_CIPH_CBC_MODE,
    cipher_des_ede3_cbc_init,
    cipher_des_ede3_cbc_code,
    cipher_des_ede3_cbc_clean,
    sizeof(DES3_CBC_CTX),
    NULL,
    NULL,
    NULL,
    NULL
};

static const EVP_CIPHER cipher_desx_cbc = {
    NID_desx_cbc,
    8, 24, 8,
    0 | EVP_CIPH_CBC_MODE,
    cipher_desx_cbc_init,
    cipher_desx_cbc_code,
    cipher_desx_cbc_clean,
    sizeof(DESX_CBC_CTX),
    NULL,
    NULL,
    NULL,
    NULL
};

/*****************************************************************************
 * MD functions
 **/
static int digest_md2_init(EVP_MD_CTX *ctx);
static int digest_md2_update(EVP_MD_CTX *ctx, const void *data,
                             unsigned long count);
static int digest_md2_final(EVP_MD_CTX *ctx, unsigned char *md);
static int digest_md5_init(EVP_MD_CTX *ctx);
static int digest_md5_update(EVP_MD_CTX *ctx, const void *data,
                             unsigned long count);
static int digest_md5_final(EVP_MD_CTX *ctx, unsigned char *md);

/*****************************************************************************
 * Our MD digests
 **/
static const EVP_MD digest_md2 = {
    NID_md2,
    NID_md2WithRSAEncryption,
    16,
    0,
    digest_md2_init,
    digest_md2_update,
    digest_md2_final,
    NULL,
    NULL,
    EVP_PKEY_RSA_method,
    16,
    sizeof(MD2_CTX)
};

static const EVP_MD digest_md5 = {
    NID_md5,
    NID_md5WithRSAEncryption,
    16,
    0,
    digest_md5_init,
    digest_md5_update,
    digest_md5_final,
    NULL,
    NULL,
    EVP_PKEY_RSA_method,
    64,
    sizeof(MD5_CTX)
};

/*****************************************************************************
 *** Function definitions                                                  ***
 *****************************************************************************/

/*****************************************************************************
 * Functions to handle the engine
 **/

static int bind_rsaref(ENGINE *e)
{
    const RSA_METHOD *meth1;
    if (!ENGINE_set_id(e, engine_rsaref_id)
        || !ENGINE_set_name(e, engine_rsaref_name)
        || !ENGINE_set_RSA(e, &rsaref_rsa)
        || !ENGINE_set_ciphers(e, rsaref_ciphers)
        || !ENGINE_set_digests(e, rsaref_digests)
        || !ENGINE_set_destroy_function(e, rsaref_destroy)
        || !ENGINE_set_init_function(e, rsaref_init)
        || !ENGINE_set_finish_function(e, rsaref_finish)
        /* || !ENGINE_set_ctrl_function(e, rsaref_ctrl) */
        /*
         * || !ENGINE_set_cmd_defns(e, rsaref_cmd_defns)
         */ )
        return 0;

    /* Ensure the rsaref error handling is set up */
    ERR_load_RSAREF_strings();
    return 1;
}

#ifdef ENGINE_DYNAMIC_SUPPORT
static int bind_helper(ENGINE *e, const char *id)
{
    if (id && (strcmp(id, engine_rsaref_id) != 0))
        return 0;
    if (!bind_rsaref(e))
        return 0;
    return 1;
}

IMPLEMENT_DYNAMIC_CHECK_FN()
    IMPLEMENT_DYNAMIC_BIND_FN(bind_helper)
#else
static ENGINE *engine_rsaref(void)
{
    ENGINE *ret = ENGINE_new();
    if (!ret)
        return NULL;
    if (!bind_rsaref(ret)) {
        ENGINE_free(ret);
        return NULL;
    }
    return ret;
}

void ENGINE_load_rsaref(void)
{
    /* Copied from eng_[openssl|dyn].c */
    ENGINE *toadd = engine_rsaref();
    if (!toadd)
        return;
    ENGINE_add(toadd);
    ENGINE_free(toadd);
    ERR_clear_error();
}
#endif

/* Initiator which is only present to make sure this engine looks available */
static int rsaref_init(ENGINE *e)
{
    return 1;
}

/* Finisher which is only present to make sure this engine looks available */
static int rsaref_finish(ENGINE *e)
{
    return 1;
}

/* Destructor (complements the "ENGINE_ncipher()" constructor) */
static int rsaref_destroy(ENGINE *e)
{
    ERR_unload_RSAREF_strings();
    return 1;
}

/*****************************************************************************
 * RSA functions
 **/

static int rsaref_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa)
{
    RSAREFerr(RSAREF_F_RSAREF_MOD_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
    return (0);
}

static int bnref_mod_exp(BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
{
    RSAREFerr(RSAREF_F_BNREF_MOD_EXP, ERR_R_SHOULD_NOT_HAVE_BEEN_CALLED);
    return (0);
}

/* unsigned char *to:  [max]    */
static int RSAref_bn2bin(BIGNUM *from, unsigned char *to, int max)
{
    int i;

    i = BN_num_bytes(from);
    if (i > max) {
        RSAREFerr(RSAREF_F_RSAREF_BN2BIN, RSAREF_R_LEN);
        return (0);
    }

    memset(to, 0, (unsigned int)max);
    if (!BN_bn2bin(from, &(to[max - i])))
        return (0);
    return (1);
}

static int RSAref_Public_eay2ref(RSA *from, R_RSA_PUBLIC_KEY * to)
{
    to->bits = BN_num_bits(from->n);
    if (!RSAref_bn2bin(from->n, to->modulus, MAX_RSA_MODULUS_LEN))
        return (0);
    if (!RSAref_bn2bin(from->e, to->exponent, MAX_RSA_MODULUS_LEN))
        return (0);
    return (1);
}

static int RSAref_Private_eay2ref(RSA *from, R_RSA_PRIVATE_KEY * to)
{
    to->bits = BN_num_bits(from->n);
    if (!RSAref_bn2bin(from->n, to->modulus, MAX_RSA_MODULUS_LEN))
        return (0);
    if (!RSAref_bn2bin(from->e, to->publicExponent, MAX_RSA_MODULUS_LEN))
        return (0);
    if (!RSAref_bn2bin(from->d, to->exponent, MAX_RSA_MODULUS_LEN))
        return (0);
    if (!RSAref_bn2bin(from->p, to->prime[0], MAX_RSA_PRIME_LEN))
        return (0);
    if (!RSAref_bn2bin(from->q, to->prime[1], MAX_RSA_PRIME_LEN))
        return (0);
    if (!RSAref_bn2bin(from->dmp1, to->primeExponent[0], MAX_RSA_PRIME_LEN))
        return (0);
    if (!RSAref_bn2bin(from->dmq1, to->primeExponent[1], MAX_RSA_PRIME_LEN))
        return (0);
    if (!RSAref_bn2bin(from->iqmp, to->coefficient, MAX_RSA_PRIME_LEN))
        return (0);
    return (1);
}

static int rsaref_private_decrypt(int len, const unsigned char *from,
                                  unsigned char *to, RSA *rsa, int padding)
{
    int i, outlen = -1;
    R_RSA_PRIVATE_KEY RSAkey;

    if (!RSAref_Private_eay2ref(rsa, &RSAkey))
        goto err;
    if ((i =
         RSAPrivateDecrypt(to, (unsigned int *)&outlen, (unsigned char *)from,
                           len, &RSAkey)) != 0) {
        RSAREFerr(RSAREF_F_RSAREF_PRIVATE_DECRYPT, i);
        outlen = -1;
    }
 err:
    memset(&RSAkey, 0, sizeof(RSAkey));
    return (outlen);
}

static int rsaref_private_encrypt(int len, const unsigned char *from,
                                  unsigned char *to, RSA *rsa, int padding)
{
    int i, outlen = -1;
    R_RSA_PRIVATE_KEY RSAkey;

    if (padding != RSA_PKCS1_PADDING) {
        RSAREFerr(RSAREF_F_RSAREF_PRIVATE_ENCRYPT,
                  RSA_R_UNKNOWN_PADDING_TYPE);
        goto err;
    }
    if (!RSAref_Private_eay2ref(rsa, &RSAkey))
        goto err;
    if ((i =
         RSAPrivateEncrypt(to, (unsigned int *)&outlen, (unsigned char *)from,
                           len, &RSAkey)) != 0) {
        RSAREFerr(RSAREF_F_RSAREF_PRIVATE_ENCRYPT, i);
        outlen = -1;
    }
 err:
    memset(&RSAkey, 0, sizeof(RSAkey));
    return (outlen);
}

static int rsaref_public_decrypt(int len, const unsigned char *from,
                                 unsigned char *to, RSA *rsa, int padding)
{
    int i, outlen = -1;
    R_RSA_PUBLIC_KEY RSAkey;

    if (!RSAref_Public_eay2ref(rsa, &RSAkey))
        goto err;
    if ((i =
         RSAPublicDecrypt(to, (unsigned int *)&outlen, (unsigned char *)from,
                          len, &RSAkey)) != 0) {
        RSAREFerr(RSAREF_F_RSAREF_PUBLIC_DECRYPT, i);
        outlen = -1;
    }
 err:
    memset(&RSAkey, 0, sizeof(RSAkey));
    return (outlen);
}

static int rsaref_public_encrypt(int len, const unsigned char *from,
                                 unsigned char *to, RSA *rsa, int padding)
{
    int outlen = -1;
    int i;
    R_RSA_PUBLIC_KEY RSAkey;
    R_RANDOM_STRUCT rnd;
    unsigned char buf[16];

    if (padding != RSA_PKCS1_PADDING && padding != RSA_SSLV23_PADDING) {
        RSAREFerr(RSAREF_F_RSAREF_PUBLIC_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
        goto err;
    }

    R_RandomInit(&rnd);
    R_GetRandomBytesNeeded((unsigned int *)&i, &rnd);
    while (i > 0) {
        if (RAND_bytes(buf, 16) <= 0)
            goto err;
        R_RandomUpdate(&rnd, buf, (unsigned int)((i > 16) ? 16 : i));
        i -= 16;
    }

    if (!RSAref_Public_eay2ref(rsa, &RSAkey))
        goto err;
    if ((i =
         RSAPublicEncrypt(to, (unsigned int *)&outlen, (unsigned char *)from,
                          len, &RSAkey, &rnd)) != 0) {
        RSAREFerr(RSAREF_F_RSAREF_PUBLIC_ENCRYPT, i);
        outlen = -1;
        goto err;
    }
 err:
    memset(&RSAkey, 0, sizeof(RSAkey));
    R_RandomFinal(&rnd);
    memset(&rnd, 0, sizeof(rnd));
    return (outlen);
}

/*****************************************************************************
 * Symetric cipher and digest function registrars
 **/
static int rsaref_ciphers(ENGINE *e, const EVP_CIPHER **cipher,
                          const int **nids, int nid)
{
    int ok = 1;
    if (!cipher) {
        /* We are returning a list of supported nids */
        *nids = rsaref_cipher_nids;
        return (sizeof(rsaref_cipher_nids) -
                1) / sizeof(rsaref_cipher_nids[0]);
    }
    /* We are being asked for a specific cipher */
    switch (nid) {
    case NID_des_cbc:
        *cipher = &cipher_des_cbc;
        break;
    case NID_des_ede3_cbc:
        *cipher = &cipher_des_ede3_cbc;
        break;
    case NID_desx_cbc:
        *cipher = &cipher_desx_cbc;
        break;
    default:
        ok = 0;
        *cipher = NULL;
        break;
    }
    return ok;
}

static int rsaref_digests(ENGINE *e, const EVP_MD **digest,
                          const int **nids, int nid)
{
    int ok = 1;
    if (!digest) {
        /* We are returning a list of supported nids */
        *nids = rsaref_digest_nids;
        return (sizeof(rsaref_digest_nids) -
                1) / sizeof(rsaref_digest_nids[0]);
    }
    /* We are being asked for a specific digest */
    switch (nid) {
    case NID_md2:
        *digest = &digest_md2;
        break;
    case NID_md5:
        *digest = &digest_md5;
        break;
    default:
        ok = 0;
        *digest = NULL;
        break;
    }
    return ok;
}

/*****************************************************************************
 * DES functions
 **/
#undef data
#define data(ctx) ((DES_CBC_CTX *)(ctx)->cipher_data)
static int cipher_des_cbc_init(EVP_CIPHER_CTX *ctx, const unsigned char *key,
                               const unsigned char *iv, int enc)
{
    DES_CBCInit(data(ctx), (unsigned char *)key, (unsigned char *)iv, enc);
    return 1;
}

static int cipher_des_cbc_code(EVP_CIPHER_CTX *ctx, unsigned char *out,
                               const unsigned char *in, unsigned int inl)
{
    int ret = DES_CBCUpdate(data(ctx), out, (unsigned char *)in, inl);
    switch (ret) {
    case RE_LEN:
        RSAREFerr(RSAREF_F_CIPHER_DES_CBC_CODE,
                  RSAREF_R_LENGTH_NOT_BLOCK_ALIGNED);
        break;
    case 0:
        break;
    default:
        RSAREFerr(RSAREF_F_CIPHER_DES_CBC_CODE, RSAREF_R_UNKNOWN_FAULT);
    }
    return !ret;
}

static int cipher_des_cbc_clean(EVP_CIPHER_CTX *ctx)
{
    memset(data(ctx), 0, ctx->cipher->ctx_size);
    return 1;
}

#undef data
#define data(ctx) ((DES3_CBC_CTX *)(ctx)->cipher_data)
static int cipher_des_ede3_cbc_init(EVP_CIPHER_CTX *ctx,
                                    const unsigned char *key,
                                    const unsigned char *iv, int enc)
{
    DES3_CBCInit(data(ctx), (unsigned char *)key, (unsigned char *)iv, enc);
    return 1;
}

static int cipher_des_ede3_cbc_code(EVP_CIPHER_CTX *ctx, unsigned char *out,
                                    const unsigned char *in, unsigned int inl)
{
    int ret = DES3_CBCUpdate(data(ctx), out, (unsigned char *)in, inl);
    switch (ret) {
    case RE_LEN:
        RSAREFerr(RSAREF_F_CIPHER_DES_CBC_CODE,
                  RSAREF_R_LENGTH_NOT_BLOCK_ALIGNED);
        break;
    case 0:
        break;
    default:
        RSAREFerr(RSAREF_F_CIPHER_DES_CBC_CODE, RSAREF_R_UNKNOWN_FAULT);
    }
    return !ret;
}

static int cipher_des_ede3_cbc_clean(EVP_CIPHER_CTX *ctx)
{
    memset(data(ctx), 0, ctx->cipher->ctx_size);
    return 1;
}

#undef data
#define data(ctx) ((DESX_CBC_CTX *)(ctx)->cipher_data)
static int cipher_desx_cbc_init(EVP_CIPHER_CTX *ctx, const unsigned char *key,
                                const unsigned char *iv, int enc)
{
    DESX_CBCInit(data(ctx), (unsigned char *)key, (unsigned char *)iv, enc);
    return 1;
}

static int cipher_desx_cbc_code(EVP_CIPHER_CTX *ctx, unsigned char *out,
                                const unsigned char *in, unsigned int inl)
{
    int ret = DESX_CBCUpdate(data(ctx), out, (unsigned char *)in, inl);
    switch (ret) {
    case RE_LEN:
        RSAREFerr(RSAREF_F_CIPHER_DES_CBC_CODE,
                  RSAREF_R_LENGTH_NOT_BLOCK_ALIGNED);
        break;
    case 0:
        break;
    default:
        RSAREFerr(RSAREF_F_CIPHER_DES_CBC_CODE, RSAREF_R_UNKNOWN_FAULT);
    }
    return !ret;
}

static int cipher_desx_cbc_clean(EVP_CIPHER_CTX *ctx)
{
    memset(data(ctx), 0, ctx->cipher->ctx_size);
    return 1;
}

/*****************************************************************************
 * MD functions
 **/
#undef data
#define data(ctx) ((MD2_CTX *)(ctx)->md_data)
static int digest_md2_init(EVP_MD_CTX *ctx)
{
    MD2Init(data(ctx));
    return 1;
}

static int digest_md2_update(EVP_MD_CTX *ctx, const void *data,
                             unsigned long count)
{
    MD2Update(data(ctx), (unsigned char *)data, (unsigned int)count);
    return 1;
}

static int digest_md2_final(EVP_MD_CTX *ctx, unsigned char *md)
{
    MD2Final(md, data(ctx));
    return 1;
}

#undef data
#define data(ctx) ((MD5_CTX *)(ctx)->md_data)
static int digest_md5_init(EVP_MD_CTX *ctx)
{
    MD5Init(data(ctx));
    return 1;
}

static int digest_md5_update(EVP_MD_CTX *ctx, const void *data,
                             unsigned long count)
{
    MD5Update(data(ctx), (unsigned char *)data, (unsigned int)count);
    return 1;
}

static int digest_md5_final(EVP_MD_CTX *ctx, unsigned char *md)
{
    MD5Final(md, data(ctx));
    return 1;
}