/* $OpenBSD: rsa_gen.c,v 1.25 2022/01/20 11:11:17 inoguchi Exp $ */

/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)

 * All rights reserved.

 *

 * This package is an SSL implementation written

 * by Eric Young (eay@cryptsoft.com).

 * The implementation was written so as to conform with Netscapes SSL.

 *

 * This library is free for commercial and non-commercial use as long as

 * the following conditions are aheared to.  The following conditions

 * apply to all code found in this distribution, be it the RC4, RSA,

 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation

 * included with this distribution is covered by the same copyright terms

 * except that the holder is Tim Hudson (tjh@cryptsoft.com).

 *

 * Copyright remains Eric Young's, and as such any Copyright notices in

 * the code are not to be removed.

 * If this package is used in a product, Eric Young should be given attribution

 * as the author of the parts of the library used.

 * This can be in the form of a textual message at program startup or

 * in documentation (online or textual) provided with the package.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. All advertising materials mentioning features or use of this software

 *    must display the following acknowledgement:

 *    "This product includes cryptographic software written by

 *     Eric Young (eay@cryptsoft.com)"

 *    The word 'cryptographic' can be left out if the rouines from the library

 *    being used are not cryptographic related :-).

 * 4. If you include any Windows specific code (or a derivative thereof) from

 *    the apps directory (application code) you must include an acknowledgement:

 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"

 *

 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 *

 * The licence and distribution terms for any publically available version or

 * derivative of this code cannot be changed.  i.e. this code cannot simply be

 * copied and put under another distribution licence

 * [including the GNU Public Licence.]

 */

/* NB: these functions have been "upgraded", the deprecated versions (which are

 * compatibility wrappers using these functions) are in rsa_depr.c.

 * - Geoff

 */

#include <stdio.h>

#include <time.h>

#include <openssl/bn.h>

#include <openssl/err.h>

#include <openssl/rsa.h>

#include "bn_lcl.h"

#include "rsa_locl.h"

static int rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb);

/*

 * NB: this wrapper would normally be placed in rsa_lib.c and the static

 * implementation would probably be in rsa_eay.c. Nonetheless, is kept here so

 * that we don't introduce a new linker dependency. Eg. any application that

 * wasn't previously linking object code related to key-generation won't have to

 * now just because key-generation is part of RSA_METHOD.

 */

int

RSA_generate_key_ex(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)

{

  if (rsa->meth->rsa_keygen)

    return rsa->meth->rsa_keygen(rsa, bits, e_value, cb);

  return rsa_builtin_keygen(rsa, bits, e_value, cb);

}

static int

rsa_builtin_keygen(RSA *rsa, int bits, BIGNUM *e_value, BN_GENCB *cb)

{

  BIGNUM *r0 = NULL, *r1 = NULL, *r2 = NULL, *r3 = NULL, *tmp;

  BIGNUM pr0, d, p;

  int bitsp, bitsq, ok = -1, n = 0;

  BN_CTX *ctx = NULL;

  ctx = BN_CTX_new();

  if (ctx == NULL)

    goto err;

  BN_CTX_start(ctx);

  if ((r0 = BN_CTX_get(ctx)) == NULL)

    goto err;

  if ((r1 = BN_CTX_get(ctx)) == NULL)

    goto err;

  if ((r2 = BN_CTX_get(ctx)) == NULL)

    goto err;

  if ((r3 = BN_CTX_get(ctx)) == NULL)

    goto err;

  bitsp = (bits + 1) / 2;

  bitsq = bits - bitsp;

  /* We need the RSA components non-NULL */

  if (!rsa->n && ((rsa->n = BN_new()) == NULL))

    goto err;

  if (!rsa->d && ((rsa->d = BN_new()) == NULL))

    goto err;

  if (!rsa->e && ((rsa->e = BN_new()) == NULL))

    goto err;

  if (!rsa->p && ((rsa->p = BN_new()) == NULL))

    goto err;

  if (!rsa->q && ((rsa->q = BN_new()) == NULL))

    goto err;

  if (!rsa->dmp1 && ((rsa->dmp1 = BN_new()) == NULL))

    goto err;

  if (!rsa->dmq1 && ((rsa->dmq1 = BN_new()) == NULL))

    goto err;

  if (!rsa->iqmp && ((rsa->iqmp = BN_new()) == NULL))

    goto err;

  BN_copy(rsa->e, e_value);

  /* generate p and q */

  for (;;) {

    if (!BN_generate_prime_ex(rsa->p, bitsp, 0, NULL, NULL, cb))

      goto err;

    if (!BN_sub(r2, rsa->p, BN_value_one()))

      goto err;

    if (!BN_gcd_ct(r1, r2, rsa->e, ctx))

      goto err;

    if (BN_is_one(r1))

      break;

    if (!BN_GENCB_call(cb, 2, n++))

      goto err;

  }

  if (!BN_GENCB_call(cb, 3, 0))

    goto err;

  for (;;) {

    /*

     * When generating ridiculously small keys, we can get stuck

     * continually regenerating the same prime values. Check for

     * this and bail if it happens 3 times.

     */

    unsigned int degenerate = 0;

    do {

      if (!BN_generate_prime_ex(rsa->q, bitsq, 0, NULL, NULL,

          cb))

        goto err;

    } while (BN_cmp(rsa->p, rsa->q) == 0 &&

        ++degenerate < 3);

    if (degenerate == 3) {

      ok = 0; /* we set our own err */

      RSAerror(RSA_R_KEY_SIZE_TOO_SMALL);

      goto err;

    }

    if (!BN_sub(r2, rsa->q, BN_value_one()))

      goto err;

    if (!BN_gcd_ct(r1, r2, rsa->e, ctx))

      goto err;

    if (BN_is_one(r1))

      break;

    if (!BN_GENCB_call(cb, 2, n++))

      goto err;

  }

  if (!BN_GENCB_call(cb, 3, 1))

    goto err;

  if (BN_cmp(rsa->p, rsa->q) < 0) {

    tmp = rsa->p;

    rsa->p = rsa->q;

    rsa->q = tmp;

  }

  /* calculate n */

  if (!BN_mul(rsa->n, rsa->p, rsa->q, ctx))

    goto err;

  /* calculate d */

  if (!BN_sub(r1, rsa->p, BN_value_one())) /* p-1 */

    goto err;

  if (!BN_sub(r2, rsa->q, BN_value_one())) /* q-1 */

    goto err;

  if (!BN_mul(r0, r1, r2, ctx))     /* (p-1)(q-1) */

    goto err;

  BN_init(&pr0);

  BN_with_flags(&pr0, r0, BN_FLG_CONSTTIME);

  if (BN_mod_inverse_ct(rsa->d, rsa->e, &pr0, ctx) == NULL) /* d */

    goto err;

  /* set up d for correct BN_FLG_CONSTTIME flag */

  BN_init(&d);

  BN_with_flags(&d, rsa->d, BN_FLG_CONSTTIME);

  /* calculate d mod (p-1) */

  if (!BN_mod_ct(rsa->dmp1, &d, r1, ctx))

    goto err;

  /* calculate d mod (q-1) */

  if (!BN_mod_ct(rsa->dmq1, &d, r2, ctx))

    goto err;

  /* calculate inverse of q mod p */

  BN_init(&p);

  BN_with_flags(&p, rsa->p, BN_FLG_CONSTTIME);

  if (BN_mod_inverse_ct(rsa->iqmp, rsa->q, &p, ctx) == NULL)

    goto err;

  ok = 1;

err:

  if (ok == -1) {

    RSAerror(ERR_LIB_BN);

    ok = 0;

  }

  if (ctx != NULL) {

    BN_CTX_end(ctx);

    BN_CTX_free(ctx);

  }

  return ok;

}