1 /* 2 * Dropbear - a SSH2 server 3 * 4 * Copyright (c) 2002,2003 Matt Johnston 5 * All rights reserved. 6 * 7 * Permission is hereby granted, free of charge, to any person obtaining a copy 8 * of this software and associated documentation files (the "Software"), to deal 9 * in the Software without restriction, including without limitation the rights 10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 11 * copies of the Software, and to permit persons to whom the Software is 12 * furnished to do so, subject to the following conditions: 13 * 14 * The above copyright notice and this permission notice shall be included in 15 * all copies or substantial portions of the Software. 16 * 17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 23 * SOFTWARE. */ 24 25 #include "includes.h" 26 #include "dbutil.h" 27 #include "bignum.h" 28 #include "random.h" 29 #include "rsa.h" 30 #include "genrsa.h" 31 32 #define RSA_E 65537 33 34 #ifdef DROPBEAR_RSA 35 36 static void getrsaprime(mp_int* prime, mp_int *primeminus, 37 mp_int* rsa_e, unsigned int size); 38 39 /* mostly taken from libtomcrypt's rsa key generation routine */ 40 rsa_key * gen_rsa_priv_key(unsigned int size) { 41 42 rsa_key * key; 43 DEF_MP_INT(pminus); 44 DEF_MP_INT(qminus); 45 DEF_MP_INT(lcm); 46 47 key = (rsa_key*)m_malloc(sizeof(rsa_key)); 48 49 key->e = (mp_int*)m_malloc(sizeof(mp_int)); 50 key->n = (mp_int*)m_malloc(sizeof(mp_int)); 51 key->d = (mp_int*)m_malloc(sizeof(mp_int)); 52 key->p = (mp_int*)m_malloc(sizeof(mp_int)); 53 key->q = (mp_int*)m_malloc(sizeof(mp_int)); 54 55 m_mp_init_multi(key->e, key->n, key->d, key->p, key->q, 56 &pminus, &lcm, &qminus, NULL); 57 58 seedrandom(); 59 60 if (mp_set_int(key->e, RSA_E) != MP_OKAY) { 61 fprintf(stderr, "rsa generation failed\n"); 62 exit(1); 63 } 64 65 /* PuTTY doesn't like it if the modulus isn't a multiple of 8 bits, 66 * so we just generate them until we get one which is OK */ 67 getrsaprime(key->p, &pminus, key->e, size/2); 68 do { 69 getrsaprime(key->q, &qminus, key->e, size/2); 70 71 if (mp_mul(key->p, key->q, key->n) != MP_OKAY) { 72 fprintf(stderr, "rsa generation failed\n"); 73 exit(1); 74 } 75 } while (mp_count_bits(key->n) % 8 != 0); 76 77 /* lcm(p-1, q-1) */ 78 if (mp_lcm(&pminus, &qminus, &lcm) != MP_OKAY) { 79 fprintf(stderr, "rsa generation failed\n"); 80 exit(1); 81 } 82 83 /* de = 1 mod lcm(p-1,q-1) */ 84 /* therefore d = (e^-1) mod lcm(p-1,q-1) */ 85 if (mp_invmod(key->e, &lcm, key->d) != MP_OKAY) { 86 fprintf(stderr, "rsa generation failed\n"); 87 exit(1); 88 } 89 90 mp_clear_multi(&pminus, &qminus, &lcm, NULL); 91 92 return key; 93 } 94 95 /* return a prime suitable for p or q */ 96 static void getrsaprime(mp_int* prime, mp_int *primeminus, 97 mp_int* rsa_e, unsigned int size) { 98 99 unsigned char *buf; 100 DEF_MP_INT(temp_gcd); 101 102 buf = (unsigned char*)m_malloc(size+1); 103 104 m_mp_init(&temp_gcd); 105 do { 106 /* generate a random odd number with MSB set, then find the 107 the next prime above it */ 108 genrandom(buf, size+1); 109 buf[0] |= 0x80; /* MSB set */ 110 111 bytes_to_mp(prime, buf, size+1); 112 113 /* find the next integer which is prime, 8 round of miller-rabin */ 114 if (mp_prime_next_prime(prime, 8, 0) != MP_OKAY) { 115 fprintf(stderr, "rsa generation failed\n"); 116 exit(1); 117 } 118 119 /* subtract one to get p-1 */ 120 if (mp_sub_d(prime, 1, primeminus) != MP_OKAY) { 121 fprintf(stderr, "rsa generation failed\n"); 122 exit(1); 123 } 124 /* check relative primality to e */ 125 if (mp_gcd(primeminus, rsa_e, &temp_gcd) != MP_OKAY) { 126 fprintf(stderr, "rsa generation failed\n"); 127 exit(1); 128 } 129 } while (mp_cmp_d(&temp_gcd, 1) != MP_EQ); /* while gcd(p-1, e) != 1 */ 130 131 /* now we have a good value for result */ 132 mp_clear(&temp_gcd); 133 m_burn(buf, size+1); 134 m_free(buf); 135 } 136 137 #endif /* DROPBEAR_RSA */ 138
