134 lines
3.8 KiB
C
134 lines
3.8 KiB
C
/*
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* Dropbear - a SSH2 server
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*
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* Copyright (c) 2002,2003 Matt Johnston
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* All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE. */
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#include "includes.h"
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#include "dbutil.h"
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#include "bignum.h"
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#include "random.h"
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#include "rsa.h"
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#include "genrsa.h"
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#define RSA_E 65537
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#ifdef DROPBEAR_RSA
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static void getrsaprime(mp_int* prime, mp_int *primeminus,
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mp_int* rsa_e, unsigned int size);
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/* mostly taken from libtomcrypt's rsa key generation routine */
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dropbear_rsa_key * gen_rsa_priv_key(unsigned int size) {
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dropbear_rsa_key * key;
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DEF_MP_INT(pminus);
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DEF_MP_INT(qminus);
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DEF_MP_INT(lcm);
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key = m_malloc(sizeof(*key));
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key->e = (mp_int*)m_malloc(sizeof(mp_int));
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key->n = (mp_int*)m_malloc(sizeof(mp_int));
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key->d = (mp_int*)m_malloc(sizeof(mp_int));
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key->p = (mp_int*)m_malloc(sizeof(mp_int));
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key->q = (mp_int*)m_malloc(sizeof(mp_int));
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m_mp_init_multi(key->e, key->n, key->d, key->p, key->q,
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&pminus, &lcm, &qminus, NULL);
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seedrandom();
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if (mp_set_int(key->e, RSA_E) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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getrsaprime(key->p, &pminus, key->e, size/2);
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getrsaprime(key->q, &qminus, key->e, size/2);
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if (mp_mul(key->p, key->q, key->n) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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/* lcm(p-1, q-1) */
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if (mp_lcm(&pminus, &qminus, &lcm) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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/* de = 1 mod lcm(p-1,q-1) */
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/* therefore d = (e^-1) mod lcm(p-1,q-1) */
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if (mp_invmod(key->e, &lcm, key->d) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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mp_clear_multi(&pminus, &qminus, &lcm, NULL);
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return key;
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}
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/* return a prime suitable for p or q */
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static void getrsaprime(mp_int* prime, mp_int *primeminus,
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mp_int* rsa_e, unsigned int size) {
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unsigned char *buf;
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DEF_MP_INT(temp_gcd);
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buf = (unsigned char*)m_malloc(size+1);
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m_mp_init(&temp_gcd);
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do {
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/* generate a random odd number with MSB set, then find the
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the next prime above it */
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genrandom(buf, size+1);
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buf[0] |= 0x80; /* MSB set */
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bytes_to_mp(prime, buf, size+1);
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/* find the next integer which is prime, 8 round of miller-rabin */
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if (mp_prime_next_prime(prime, 8, 0) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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/* subtract one to get p-1 */
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if (mp_sub_d(prime, 1, primeminus) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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/* check relative primality to e */
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if (mp_gcd(primeminus, rsa_e, &temp_gcd) != MP_OKAY) {
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fprintf(stderr, "RSA generation failed\n");
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exit(1);
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}
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} while (mp_cmp_d(&temp_gcd, 1) != MP_EQ); /* while gcd(p-1, e) != 1 */
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/* now we have a good value for result */
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mp_clear(&temp_gcd);
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m_burn(buf, size+1);
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m_free(buf);
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}
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#endif /* DROPBEAR_RSA */
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