--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/genrsa.c	Thu Jan 11 04:29:08 2007 +0000
@@ -0,0 +1,137 @@
+/*
+ * Dropbear - a SSH2 server
+ * 
+ * Copyright (c) 2002,2003 Matt Johnston
+ * All rights reserved.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE. */
+
+#include "includes.h"
+#include "dbutil.h"
+#include "bignum.h"
+#include "random.h"
+#include "rsa.h"
+#include "genrsa.h"
+
+#define RSA_E 65537
+
+#ifdef DROPBEAR_RSA
+
+static void getrsaprime(mp_int* prime, mp_int *primeminus, 
+		mp_int* rsa_e, unsigned int size);
+
+/* mostly taken from libtomcrypt's rsa key generation routine */
+rsa_key * gen_rsa_priv_key(unsigned int size) {
+
+	rsa_key * key;
+	DEF_MP_INT(pminus);
+	DEF_MP_INT(qminus);
+	DEF_MP_INT(lcm);
+
+	key = (rsa_key*)m_malloc(sizeof(rsa_key));
+
+	key->e = (mp_int*)m_malloc(sizeof(mp_int));
+	key->n = (mp_int*)m_malloc(sizeof(mp_int));
+	key->d = (mp_int*)m_malloc(sizeof(mp_int));
+	key->p = (mp_int*)m_malloc(sizeof(mp_int));
+	key->q = (mp_int*)m_malloc(sizeof(mp_int));
+
+	m_mp_init_multi(key->e, key->n, key->d, key->p, key->q,
+			&pminus, &lcm, &qminus, NULL);
+
+	seedrandom();
+
+	if (mp_set_int(key->e, RSA_E) != MP_OKAY) {
+		fprintf(stderr, "rsa generation failed\n");
+		exit(1);
+	}
+
+	/* PuTTY doesn't like it if the modulus isn't a multiple of 8 bits,
+	 * so we just generate them until we get one which is OK */
+	getrsaprime(key->p, &pminus, key->e, size/2);
+	do {
+		getrsaprime(key->q, &qminus, key->e, size/2);
+
+		if (mp_mul(key->p, key->q, key->n) != MP_OKAY) {
+			fprintf(stderr, "rsa generation failed\n");
+			exit(1);
+		}
+	} while (mp_count_bits(key->n) % 8 != 0);
+
+	/* lcm(p-1, q-1) */
+	if (mp_lcm(&pminus, &qminus, &lcm) != MP_OKAY) {
+		fprintf(stderr, "rsa generation failed\n");
+		exit(1);
+	}
+
+	/* de = 1 mod lcm(p-1,q-1) */
+	/* therefore d = (e^-1) mod lcm(p-1,q-1) */
+	if (mp_invmod(key->e, &lcm, key->d) != MP_OKAY) {
+		fprintf(stderr, "rsa generation failed\n");
+		exit(1);
+	}
+
+	mp_clear_multi(&pminus, &qminus, &lcm, NULL);
+
+	return key;
+}	
+
+/* return a prime suitable for p or q */
+static void getrsaprime(mp_int* prime, mp_int *primeminus, 
+		mp_int* rsa_e, unsigned int size) {
+
+	unsigned char *buf;
+	DEF_MP_INT(temp_gcd);
+
+	buf = (unsigned char*)m_malloc(size+1);
+
+	m_mp_init(&temp_gcd);
+	do {
+		/* generate a random odd number with MSB set, then find the
+		   the next prime above it */
+		genrandom(buf, size+1);
+		buf[0] |= 0x80; /* MSB set */
+
+		bytes_to_mp(prime, buf, size+1);
+
+		/* find the next integer which is prime, 8 round of miller-rabin */
+		if (mp_prime_next_prime(prime, 8, 0) != MP_OKAY) {
+			fprintf(stderr, "rsa generation failed\n");
+			exit(1);
+		}
+
+		/* subtract one to get p-1 */
+		if (mp_sub_d(prime, 1, primeminus) != MP_OKAY) {
+			fprintf(stderr, "rsa generation failed\n");
+			exit(1);
+		}
+		/* check relative primality to e */
+		if (mp_gcd(primeminus, rsa_e, &temp_gcd) != MP_OKAY) {
+			fprintf(stderr, "rsa generation failed\n");
+			exit(1);
+		}
+	} while (mp_cmp_d(&temp_gcd, 1) != MP_EQ); /* while gcd(p-1, e) != 1 */
+
+	/* now we have a good value for result */
+	mp_clear(&temp_gcd);
+	m_burn(buf, size+1);
+	m_free(buf);
+}
+
+#endif /* DROPBEAR_RSA */