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627 lines
16 KiB
C
627 lines
16 KiB
C
/* $OpenBSD: moduli.c,v 1.5 2003/12/22 09:16:57 djm Exp $ */
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/*
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* Copyright 1994 Phil Karn <karn@qualcomm.com>
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* Copyright 1996-1998, 2003 William Allen Simpson <wsimpson@greendragon.com>
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* Copyright 2000 Niels Provos <provos@citi.umich.edu>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Two-step process to generate safe primes for DHGEX
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*
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* Sieve candidates for "safe" primes,
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* suitable for use as Diffie-Hellman moduli;
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* that is, where q = (p-1)/2 is also prime.
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*
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* First step: generate candidate primes (memory intensive)
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* Second step: test primes' safety (processor intensive)
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*/
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#include "includes.h"
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#include "moduli.h"
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#include "xmalloc.h"
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#include "log.h"
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#include <openssl/bn.h>
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/*
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* File output defines
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*/
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/* need line long enough for largest moduli plus headers */
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#define QLINESIZE (100+8192)
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/* Type: decimal.
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* Specifies the internal structure of the prime modulus.
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*/
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#define QTYPE_UNKNOWN (0)
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#define QTYPE_UNSTRUCTURED (1)
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#define QTYPE_SAFE (2)
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#define QTYPE_SCHNOOR (3)
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#define QTYPE_SOPHIE_GERMAINE (4)
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#define QTYPE_STRONG (5)
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/* Tests: decimal (bit field).
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* Specifies the methods used in checking for primality.
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* Usually, more than one test is used.
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*/
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#define QTEST_UNTESTED (0x00)
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#define QTEST_COMPOSITE (0x01)
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#define QTEST_SIEVE (0x02)
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#define QTEST_MILLER_RABIN (0x04)
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#define QTEST_JACOBI (0x08)
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#define QTEST_ELLIPTIC (0x10)
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/*
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* Size: decimal.
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* Specifies the number of the most significant bit (0 to M).
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* WARNING: internally, usually 1 to N.
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*/
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#define QSIZE_MINIMUM (511)
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/*
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* Prime sieving defines
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*/
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/* Constant: assuming 8 bit bytes and 32 bit words */
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#define SHIFT_BIT (3)
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#define SHIFT_BYTE (2)
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#define SHIFT_WORD (SHIFT_BIT+SHIFT_BYTE)
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#define SHIFT_MEGABYTE (20)
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#define SHIFT_MEGAWORD (SHIFT_MEGABYTE-SHIFT_BYTE)
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/*
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* Constant: when used with 32-bit integers, the largest sieve prime
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* has to be less than 2**32.
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*/
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#define SMALL_MAXIMUM (0xffffffffUL)
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/* Constant: can sieve all primes less than 2**32, as 65537**2 > 2**32-1. */
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#define TINY_NUMBER (1UL<<16)
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/* Ensure enough bit space for testing 2*q. */
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#define TEST_MAXIMUM (1UL<<16)
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#define TEST_MINIMUM (QSIZE_MINIMUM + 1)
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/* real TEST_MINIMUM (1UL << (SHIFT_WORD - TEST_POWER)) */
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#define TEST_POWER (3) /* 2**n, n < SHIFT_WORD */
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/* bit operations on 32-bit words */
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#define BIT_CLEAR(a,n) ((a)[(n)>>SHIFT_WORD] &= ~(1L << ((n) & 31)))
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#define BIT_SET(a,n) ((a)[(n)>>SHIFT_WORD] |= (1L << ((n) & 31)))
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#define BIT_TEST(a,n) ((a)[(n)>>SHIFT_WORD] & (1L << ((n) & 31)))
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/*
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* Prime testing defines
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*/
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/*
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* Sieving data (XXX - move to struct)
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*/
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/* sieve 2**16 */
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static u_int32_t *TinySieve, tinybits;
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/* sieve 2**30 in 2**16 parts */
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static u_int32_t *SmallSieve, smallbits, smallbase;
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/* sieve relative to the initial value */
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static u_int32_t *LargeSieve, largewords, largetries, largenumbers;
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static u_int32_t largebits, largememory; /* megabytes */
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static BIGNUM *largebase;
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/*
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* print moduli out in consistent form,
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*/
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static int
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qfileout(FILE * ofile, u_int32_t otype, u_int32_t otests, u_int32_t otries,
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u_int32_t osize, u_int32_t ogenerator, BIGNUM * omodulus)
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{
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struct tm *gtm;
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time_t time_now;
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int res;
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time(&time_now);
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gtm = gmtime(&time_now);
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res = fprintf(ofile, "%04d%02d%02d%02d%02d%02d %u %u %u %u %x ",
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gtm->tm_year + 1900, gtm->tm_mon + 1, gtm->tm_mday,
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gtm->tm_hour, gtm->tm_min, gtm->tm_sec,
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otype, otests, otries, osize, ogenerator);
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if (res < 0)
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return (-1);
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if (BN_print_fp(ofile, omodulus) < 1)
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return (-1);
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res = fprintf(ofile, "\n");
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fflush(ofile);
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return (res > 0 ? 0 : -1);
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}
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/*
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** Sieve p's and q's with small factors
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*/
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static void
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sieve_large(u_int32_t s)
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{
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u_int32_t r, u;
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debug3("sieve_large %u", s);
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largetries++;
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/* r = largebase mod s */
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r = BN_mod_word(largebase, s);
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if (r == 0)
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u = 0; /* s divides into largebase exactly */
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else
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u = s - r; /* largebase+u is first entry divisible by s */
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if (u < largebits * 2) {
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/*
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* The sieve omits p's and q's divisible by 2, so ensure that
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* largebase+u is odd. Then, step through the sieve in
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* increments of 2*s
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*/
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if (u & 0x1)
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u += s; /* Make largebase+u odd, and u even */
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/* Mark all multiples of 2*s */
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for (u /= 2; u < largebits; u += s)
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BIT_SET(LargeSieve, u);
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}
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/* r = p mod s */
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r = (2 * r + 1) % s;
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if (r == 0)
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u = 0; /* s divides p exactly */
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else
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u = s - r; /* p+u is first entry divisible by s */
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if (u < largebits * 4) {
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/*
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* The sieve omits p's divisible by 4, so ensure that
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* largebase+u is not. Then, step through the sieve in
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* increments of 4*s
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*/
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while (u & 0x3) {
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if (SMALL_MAXIMUM - u < s)
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return;
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u += s;
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}
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/* Mark all multiples of 4*s */
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for (u /= 4; u < largebits; u += s)
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BIT_SET(LargeSieve, u);
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}
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}
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/*
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* list candidates for Sophie-Germaine primes (where q = (p-1)/2)
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* to standard output.
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* The list is checked against small known primes (less than 2**30).
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*/
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int
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gen_candidates(FILE *out, int memory, int power, BIGNUM *start)
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{
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BIGNUM *q;
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u_int32_t j, r, s, t;
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u_int32_t smallwords = TINY_NUMBER >> 6;
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u_int32_t tinywords = TINY_NUMBER >> 6;
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time_t time_start, time_stop;
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int i, ret = 0;
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largememory = memory;
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/*
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* Set power to the length in bits of the prime to be generated.
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* This is changed to 1 less than the desired safe prime moduli p.
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*/
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if (power > TEST_MAXIMUM) {
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error("Too many bits: %u > %lu", power, TEST_MAXIMUM);
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return (-1);
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} else if (power < TEST_MINIMUM) {
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error("Too few bits: %u < %u", power, TEST_MINIMUM);
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return (-1);
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}
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power--; /* decrement before squaring */
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/*
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* The density of ordinary primes is on the order of 1/bits, so the
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* density of safe primes should be about (1/bits)**2. Set test range
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* to something well above bits**2 to be reasonably sure (but not
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* guaranteed) of catching at least one safe prime.
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*/
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largewords = ((power * power) >> (SHIFT_WORD - TEST_POWER));
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/*
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* Need idea of how much memory is available. We don't have to use all
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* of it.
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*/
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if (largememory > LARGE_MAXIMUM) {
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logit("Limited memory: %u MB; limit %lu MB",
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largememory, LARGE_MAXIMUM);
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largememory = LARGE_MAXIMUM;
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}
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if (largewords <= (largememory << SHIFT_MEGAWORD)) {
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logit("Increased memory: %u MB; need %u bytes",
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largememory, (largewords << SHIFT_BYTE));
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largewords = (largememory << SHIFT_MEGAWORD);
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} else if (largememory > 0) {
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logit("Decreased memory: %u MB; want %u bytes",
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largememory, (largewords << SHIFT_BYTE));
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largewords = (largememory << SHIFT_MEGAWORD);
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}
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TinySieve = calloc(tinywords, sizeof(u_int32_t));
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if (TinySieve == NULL) {
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error("Insufficient memory for tiny sieve: need %u bytes",
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tinywords << SHIFT_BYTE);
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exit(1);
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}
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tinybits = tinywords << SHIFT_WORD;
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SmallSieve = calloc(smallwords, sizeof(u_int32_t));
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if (SmallSieve == NULL) {
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error("Insufficient memory for small sieve: need %u bytes",
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smallwords << SHIFT_BYTE);
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xfree(TinySieve);
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exit(1);
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}
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smallbits = smallwords << SHIFT_WORD;
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/*
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* dynamically determine available memory
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*/
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while ((LargeSieve = calloc(largewords, sizeof(u_int32_t))) == NULL)
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largewords -= (1L << (SHIFT_MEGAWORD - 2)); /* 1/4 MB chunks */
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largebits = largewords << SHIFT_WORD;
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largenumbers = largebits * 2; /* even numbers excluded */
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/* validation check: count the number of primes tried */
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largetries = 0;
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q = BN_new();
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/*
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* Generate random starting point for subprime search, or use
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* specified parameter.
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*/
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largebase = BN_new();
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if (start == NULL)
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BN_rand(largebase, power, 1, 1);
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else
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BN_copy(largebase, start);
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/* ensure odd */
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BN_set_bit(largebase, 0);
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time(&time_start);
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logit("%.24s Sieve next %u plus %u-bit", ctime(&time_start),
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largenumbers, power);
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debug2("start point: 0x%s", BN_bn2hex(largebase));
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/*
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* TinySieve
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*/
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for (i = 0; i < tinybits; i++) {
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if (BIT_TEST(TinySieve, i))
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continue; /* 2*i+3 is composite */
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/* The next tiny prime */
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t = 2 * i + 3;
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/* Mark all multiples of t */
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for (j = i + t; j < tinybits; j += t)
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BIT_SET(TinySieve, j);
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sieve_large(t);
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}
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/*
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* Start the small block search at the next possible prime. To avoid
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* fencepost errors, the last pass is skipped.
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*/
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for (smallbase = TINY_NUMBER + 3;
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smallbase < (SMALL_MAXIMUM - TINY_NUMBER);
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smallbase += TINY_NUMBER) {
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for (i = 0; i < tinybits; i++) {
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if (BIT_TEST(TinySieve, i))
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continue; /* 2*i+3 is composite */
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/* The next tiny prime */
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t = 2 * i + 3;
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r = smallbase % t;
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if (r == 0) {
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s = 0; /* t divides into smallbase exactly */
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} else {
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/* smallbase+s is first entry divisible by t */
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s = t - r;
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}
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/*
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* The sieve omits even numbers, so ensure that
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* smallbase+s is odd. Then, step through the sieve
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* in increments of 2*t
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*/
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if (s & 1)
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s += t; /* Make smallbase+s odd, and s even */
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/* Mark all multiples of 2*t */
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for (s /= 2; s < smallbits; s += t)
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BIT_SET(SmallSieve, s);
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}
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/*
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* SmallSieve
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*/
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for (i = 0; i < smallbits; i++) {
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if (BIT_TEST(SmallSieve, i))
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continue; /* 2*i+smallbase is composite */
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/* The next small prime */
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sieve_large((2 * i) + smallbase);
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}
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memset(SmallSieve, 0, smallwords << SHIFT_BYTE);
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}
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time(&time_stop);
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logit("%.24s Sieved with %u small primes in %ld seconds",
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ctime(&time_stop), largetries, (long) (time_stop - time_start));
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for (j = r = 0; j < largebits; j++) {
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if (BIT_TEST(LargeSieve, j))
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continue; /* Definitely composite, skip */
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debug2("test q = largebase+%u", 2 * j);
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BN_set_word(q, 2 * j);
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BN_add(q, q, largebase);
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if (qfileout(out, QTYPE_SOPHIE_GERMAINE, QTEST_SIEVE,
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largetries, (power - 1) /* MSB */, (0), q) == -1) {
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ret = -1;
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break;
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}
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r++; /* count q */
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}
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time(&time_stop);
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xfree(LargeSieve);
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xfree(SmallSieve);
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xfree(TinySieve);
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logit("%.24s Found %u candidates", ctime(&time_stop), r);
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return (ret);
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}
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/*
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* perform a Miller-Rabin primality test
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* on the list of candidates
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* (checking both q and p)
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* The result is a list of so-call "safe" primes
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*/
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int
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prime_test(FILE *in, FILE *out, u_int32_t trials,
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u_int32_t generator_wanted)
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{
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BIGNUM *q, *p, *a;
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BN_CTX *ctx;
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char *cp, *lp;
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u_int32_t count_in = 0, count_out = 0, count_possible = 0;
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u_int32_t generator_known, in_tests, in_tries, in_type, in_size;
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time_t time_start, time_stop;
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int res;
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time(&time_start);
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p = BN_new();
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q = BN_new();
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ctx = BN_CTX_new();
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debug2("%.24s Final %u Miller-Rabin trials (%x generator)",
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ctime(&time_start), trials, generator_wanted);
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res = 0;
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lp = xmalloc(QLINESIZE + 1);
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while (fgets(lp, QLINESIZE, in) != NULL) {
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int ll = strlen(lp);
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count_in++;
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if (ll < 14 || *lp == '!' || *lp == '#') {
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debug2("%10u: comment or short line", count_in);
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continue;
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}
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/* XXX - fragile parser */
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/* time */
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cp = &lp[14]; /* (skip) */
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/* type */
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in_type = strtoul(cp, &cp, 10);
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/* tests */
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in_tests = strtoul(cp, &cp, 10);
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if (in_tests & QTEST_COMPOSITE) {
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debug2("%10u: known composite", count_in);
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continue;
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}
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/* tries */
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in_tries = strtoul(cp, &cp, 10);
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/* size (most significant bit) */
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in_size = strtoul(cp, &cp, 10);
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/* generator (hex) */
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generator_known = strtoul(cp, &cp, 16);
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/* Skip white space */
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cp += strspn(cp, " ");
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/* modulus (hex) */
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switch (in_type) {
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case QTYPE_SOPHIE_GERMAINE:
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debug2("%10u: (%u) Sophie-Germaine", count_in, in_type);
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a = q;
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BN_hex2bn(&a, cp);
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/* p = 2*q + 1 */
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BN_lshift(p, q, 1);
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BN_add_word(p, 1);
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in_size += 1;
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generator_known = 0;
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break;
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case QTYPE_UNSTRUCTURED:
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case QTYPE_SAFE:
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case QTYPE_SCHNOOR:
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case QTYPE_STRONG:
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case QTYPE_UNKNOWN:
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debug2("%10u: (%u)", count_in, in_type);
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a = p;
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BN_hex2bn(&a, cp);
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/* q = (p-1) / 2 */
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BN_rshift(q, p, 1);
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break;
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default:
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debug2("Unknown prime type");
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break;
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}
|
|
|
|
/*
|
|
* due to earlier inconsistencies in interpretation, check
|
|
* the proposed bit size.
|
|
*/
|
|
if (BN_num_bits(p) != (in_size + 1)) {
|
|
debug2("%10u: bit size %u mismatch", count_in, in_size);
|
|
continue;
|
|
}
|
|
if (in_size < QSIZE_MINIMUM) {
|
|
debug2("%10u: bit size %u too short", count_in, in_size);
|
|
continue;
|
|
}
|
|
|
|
if (in_tests & QTEST_MILLER_RABIN)
|
|
in_tries += trials;
|
|
else
|
|
in_tries = trials;
|
|
|
|
/*
|
|
* guess unknown generator
|
|
*/
|
|
if (generator_known == 0) {
|
|
if (BN_mod_word(p, 24) == 11)
|
|
generator_known = 2;
|
|
else if (BN_mod_word(p, 12) == 5)
|
|
generator_known = 3;
|
|
else {
|
|
u_int32_t r = BN_mod_word(p, 10);
|
|
|
|
if (r == 3 || r == 7)
|
|
generator_known = 5;
|
|
}
|
|
}
|
|
/*
|
|
* skip tests when desired generator doesn't match
|
|
*/
|
|
if (generator_wanted > 0 &&
|
|
generator_wanted != generator_known) {
|
|
debug2("%10u: generator %d != %d",
|
|
count_in, generator_known, generator_wanted);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* Primes with no known generator are useless for DH, so
|
|
* skip those.
|
|
*/
|
|
if (generator_known == 0) {
|
|
debug2("%10u: no known generator", count_in);
|
|
continue;
|
|
}
|
|
|
|
count_possible++;
|
|
|
|
/*
|
|
* The (1/4)^N performance bound on Miller-Rabin is
|
|
* extremely pessimistic, so don't spend a lot of time
|
|
* really verifying that q is prime until after we know
|
|
* that p is also prime. A single pass will weed out the
|
|
* vast majority of composite q's.
|
|
*/
|
|
if (BN_is_prime(q, 1, NULL, ctx, NULL) <= 0) {
|
|
debug("%10u: q failed first possible prime test",
|
|
count_in);
|
|
continue;
|
|
}
|
|
|
|
/*
|
|
* q is possibly prime, so go ahead and really make sure
|
|
* that p is prime. If it is, then we can go back and do
|
|
* the same for q. If p is composite, chances are that
|
|
* will show up on the first Rabin-Miller iteration so it
|
|
* doesn't hurt to specify a high iteration count.
|
|
*/
|
|
if (!BN_is_prime(p, trials, NULL, ctx, NULL)) {
|
|
debug("%10u: p is not prime", count_in);
|
|
continue;
|
|
}
|
|
debug("%10u: p is almost certainly prime", count_in);
|
|
|
|
/* recheck q more rigorously */
|
|
if (!BN_is_prime(q, trials - 1, NULL, ctx, NULL)) {
|
|
debug("%10u: q is not prime", count_in);
|
|
continue;
|
|
}
|
|
debug("%10u: q is almost certainly prime", count_in);
|
|
|
|
if (qfileout(out, QTYPE_SAFE, (in_tests | QTEST_MILLER_RABIN),
|
|
in_tries, in_size, generator_known, p)) {
|
|
res = -1;
|
|
break;
|
|
}
|
|
|
|
count_out++;
|
|
}
|
|
|
|
time(&time_stop);
|
|
xfree(lp);
|
|
BN_free(p);
|
|
BN_free(q);
|
|
BN_CTX_free(ctx);
|
|
|
|
logit("%.24s Found %u safe primes of %u candidates in %ld seconds",
|
|
ctime(&time_stop), count_out, count_possible,
|
|
(long) (time_stop - time_start));
|
|
|
|
return (res);
|
|
}
|