dsa_subr.c

包含标准证书编/解码、哈希、MD5、SHA1等算法的实现源码

/*
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  The above copyright notice and this permission notice shall be
  included in all copies or substantial portions of the Software.

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*/

#pragma ident "@(#)dsa_subr.C	1.8 96/01/30"

/*
 * Copyright (c) 1995, 1996  Colin Plumb.  All rights reserved.
 * For licensing and other legal details, see the file legal.c.
 *
 * This generates DSA primes using a (hopefully) clearly
 * defined algorithm, based on David Kravitz's "kosherizer".
 * It is not, however, identical.
 */

#include <stdio.h>
#include <string.h>
#include "Bstream.h"
#include "Bigint.h"
#include "Time.h"
#include "asn1_der.h"
#include "ObjId.h"
#include "Name.h"
#include "X509Cert.h"
#include "Sig.h"

#include "bn.h"
#include "bn_glue.h"
#include "prime.h"
#include "sha.h"
#include "dsa.h"
#include "ca.h"
#include "utils.h"

/*
 * Generate a random bignum of a specified length.
 */
int
genRandBn(struct BigNum *bn, unsigned bits)
{
	unsigned char buf[64];
	unsigned bytes = (bits+7)/8;
	unsigned l = 0;	/* Current position */
	unsigned i;

	bnSetQ(bn, 0);

	if (!bits)
		return 0;

	/* Do low-order portions */
	while (bytes > sizeof(buf)) {
		randpool_getbytes(buf, sizeof(buf));
		if (bnInsertBigBytes(bn, buf, l, sizeof(buf)) < 0)
			return -1;
		l += sizeof(buf);
	}

	/* Do the most-significant chunk */
	randpool_getbytes(buf, bytes);
	/* Mask off excess high bits */
	buf[0] &= 255 >> (-bits & 7);

	return bnInsertBigBytes(bn, buf, l, bytes);
}

/*
 * DSA signature.
 * Inputs:
 * p - a large prime
 * q - a 160-bit prime factor of (p-1).  (Actually, any length will do.)
 * g - a generator of order q modulo p, i.e. g^q == 1 (mod p)
 * x - the secret key, 1 < x < q-1
 * hash - the value to be signed
 * k - the per-signature random number, 1 < k < q-1
 * Outputs: r, s
 *
 * returns 0 on success and -1 on failure (out of memory or bogus key)
 */
static int
dsaSign(struct BigNum const *p, struct BigNum const *q,
	struct BigNum const *g, struct BigNum const *x,
	struct BigNum const *hash, struct BigNum const *k,
	struct BigNum *r, struct BigNum *s)
{
	int retval = -1;
	struct BigNum t;

	/* Sanity check all the values */
	if ((bnLSWord(p) & 1) == 0|| (bnLSWord(q) & 1) == 0 ||
	    bnCmp(p, q) <= 0 || bnCmp(p, g) <= 0 ||
	    bnCmp(q, x) <= 0 || bnCmp(q, k) <= 0 ||
	    bnBits(x) <= 1 || bnBits(k) <= 1)
		return -1;

	bnBegin(&t);

	printf("Error: Cannot Sign\n");
	retval = -1;

failed:
	bnEnd(&t);
	return retval;
}

Bstream
DSA_sign(const Bigint& p, const Bigint& q, const Bigint& g,
		const Bigint& x, const Bstream& data) 
{
	struct BigNum prime, subprime, gen, secret, k, s_r, s_s, hash;
	Bstream nullbstr, localhash;
	int retval;

	bnInit();	// just in case ...

	// locally compute the hash
	localhash = messageDigest(data, dsaWithSHA);

	// initialize bignums and convert as neccessary
	bnBegin(&prime);
	bnBegin(&subprime);
	bnBegin(&gen);
	bnBegin(&secret);
	bnBegin(&hash);
	bnBegin(&k);
	bnBegin(&s_r);
	bnBegin(&s_s);

	Bigint_to_BigNum(&p, &prime);
	Bigint_to_BigNum(&q, &subprime);
	Bigint_to_BigNum(&g, &gen);
	Bigint_to_BigNum(&x, &secret);
	Bstream_to_BigNum(&localhash, &hash);

	// generate k uniformly between 0 and q-1
	camode = TRUE;
	if (genRandBn(&k, bnBits(&subprime)+8) < 0 ||
	    bnMod(&k, &k, &subprime) <0) {
		fprintf(stderr, "DSA_sign: failed to generate 'k'\n");
		goto failed;
	}
	retval = dsaSign(&prime, &subprime, &gen, &secret, &hash, &k,
			&s_r, &s_s);
	if (retval == 0) {
		Bigint r, s;
		BigNum_to_Bigint(&s_r, &r);
		BigNum_to_Bigint(&s_s, &s);
		nullbstr = asn1_der_encode_dsa_signature(r, s);
	} else
		fprintf(stderr, "DSA_sign: failed to sign\n");

failed:
	bnEnd(&prime);
	bnEnd(&subprime);
	bnEnd(&gen);
	bnEnd(&secret);
	bnEnd(&k);
	bnEnd(&hash);
	bnEnd(&s_r);
	bnEnd(&s_s);

	return (nullbstr);
}

/*
 * DSA signature verification.
 * Inputs:
 * p - a large prime
 * q - a 160-bit prime factor of (p-1).  (Actually, any length will do.)
 * g - a generator of order q modulo p, i.e. g^q == 1 (mod p)
 * y - the public key, g^x mod p, 1 < y < p-1
 * r = the signature (first part)
 * s = the signature (second part)
 * hash - the value to be signed
 * Outputs:
 * Returns 1 for a good signature, 0 for bad, and -1 on error.
 *
 */
static int
dsaVerify(struct BigNum const *p, struct BigNum const *q,
          struct BigNum const *g, struct BigNum const *y,
          struct BigNum const *r, struct BigNum const *s,
          struct BigNum const *hash)
{
	struct BigNum v, u1, u2;
	int retval = -1;
	int i;

	/* Sanity check all the values */
	if ((bnLSWord(p) & 1) == 0|| (bnLSWord(q) & 1) == 0 ||
	    bnCmp(p, q) <= 0 || bnCmp(p, g) <= 0 ||
	    bnCmp(q, r) <= 0 || bnCmp(q, s) <= 0)
		return 0;	// Messed up -> all signatures are bad

	bnBegin(&v);
	bnBegin(&u1);
	bnBegin(&u2);

	printf("Error: Cannot Verify\n");
	retval = -1;		// An Error since we can't verify
failed:
	bnEnd(&u2);
	bnEnd(&u1);
	bnEnd(&v);
	return retval;
}

VerifyResult
DSA_verify(const Bstream& data, const Bstream& sig, const PubKey& pubkey,
		AlgId sigalg)
{
	Bigint p, q, g, y, r, s;
	Bstream localhash;
	struct BigNum prime, subprime, gen, pub, s_r, s_s, hash;
	int retval;

	bnInit();	// just in case ....

	// decode the DSA parameters, and public key
	Bstream der_stream = pubkey.keytype.params;
	retval = asn1_der_decode_dsa_params(der_stream, p, q, g);
	if (retval < 0) {
		fprintf(stderr, "DSA_verify: Bad key params encoding\n");
		return (INVALID_SIG);
	}
	der_stream = pubkey.key;
	y = Bigint(der_stream.getdatap(), der_stream.getlength());
	if (y == Bigint((short)0)) {
		fprintf(stderr, "DSA_verify: Bad publickey encoding\n");
		return (INVALID_SIG);
	}
	// decode the signature into its components
	retval = asn1_der_decode_dsa_signature(sig, r, s);
	if (retval < 0) {
		fprintf(stderr, "DSA_verify: Bad signature encoding\n");
		return (INVALID_SIG);
	}

	// Locally compute message digest over the input portion
	localhash = messageDigest(data, sigalg.algid);

	// intialize bignums and convert as necessary
	bnBegin(&prime);
	bnBegin(&subprime);
	bnBegin(&gen);
	bnBegin(&pub);
	bnBegin(&s_r);
	bnBegin(&s_s);
	bnBegin(&hash);

	Bigint_to_BigNum(&p, &prime);
	Bigint_to_BigNum(&q, &subprime);
	Bigint_to_BigNum(&g, &gen);
	Bigint_to_BigNum(&y, &pub);
	Bigint_to_BigNum(&r, &s_r);
	Bigint_to_BigNum(&s, &s_s);
	Bstream_to_BigNum(&localhash, &hash);
	
	retval = dsaVerify(&prime, &subprime, &gen, &pub, &s_r, &s_s, &hash);

	bnEnd(&prime);
	bnEnd(&subprime);
	bnEnd(&gen);
	bnEnd(&pub);
	bnEnd(&s_r);
	bnEnd(&s_s);
	bnEnd(&hash);

	if (retval <= 0) {
		fprintf(stderr, "DSA_verify: Bad signature\n");
		return (INVALID_SIG);
	}
	return (VALID);
}

// ASN.1 routines for DSA encoding/decoding
int
asn1_der_decode_dsa_privkey(Bstream der_stream, Bigint& p, Bigint& q,
				Bigint& g, Bigint& x)
{
        byte tmp = 0;
        int seqlen, retval = 0;
        ObjId oid;
        Bigint version;
	Bstream DSAprivkey;

	SEQUENCE {
		INTEGER(version);	// version of syntax
		SEQUENCE {		// privkey alg id
			OBJECT_IDENTIFIER(oid);
                	SEQUENCE {
                        	INTEGER(p);
                        	INTEGER(q);
                        	INTEGER(g);
                	}
        	}
		OCTET_STRING(DSAprivkey);
		// XXX -- leaving out the optional attributes stuff
	}