1 /* crypto/dsa/dsa_ossl.c */
2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to. The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 * must display the following acknowledgement:
33 * "This product includes cryptographic software written by
34 * Eric Young (eay@cryptsoft.com)"
35 * The word 'cryptographic' can be left out if the rouines from the library
36 * being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 * the apps directory (application code) you must include an acknowledgement:
39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed. i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
59 /* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
63 #include <openssl/bn.h>
64 #include <openssl/dsa.h>
65 #include <openssl/rand.h>
66 #include <openssl/asn1.h>
69 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
70 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
71 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
73 static int dsa_init(DSA *dsa);
74 static int dsa_finish(DSA *dsa);
75 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
76 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
77 BN_MONT_CTX *in_mont);
78 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
79 const BIGNUM *m, BN_CTX *ctx,
82 static DSA_METHOD openssl_dsa_meth = {
95 const DSA_METHOD *DSA_OpenSSL(void)
97 return &openssl_dsa_meth;
100 static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
102 BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
106 int i,reason=ERR_R_BN_LIB;
112 if (!dsa->p || !dsa->q || !dsa->g)
114 reason=DSA_R_MISSING_PARAMETERS;
119 if (s == NULL) goto err;
121 i=BN_num_bytes(dsa->q); /* should be 20 */
122 if ((dlen > i) || (dlen > 50))
124 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
129 if (ctx == NULL) goto err;
131 if ((dsa->kinv == NULL) || (dsa->r == NULL))
133 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
143 if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err;
145 /* Compute s = inv(k) (m + xr) mod q */
146 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
147 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */
148 if (BN_cmp(s,dsa->q) > 0)
150 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
153 if (ret == NULL) goto err;
160 DSAerr(DSA_F_DSA_DO_SIGN,reason);
164 if (ctx != NULL) BN_CTX_free(ctx);
167 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
172 static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
175 BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
178 if (!dsa->p || !dsa->q || !dsa->g)
180 DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
189 if ((ctx=BN_CTX_new()) == NULL) goto err;
194 if ((r=BN_new()) == NULL) goto err;
198 if (!BN_rand_range(&k, dsa->q)) goto err;
199 while (BN_is_zero(&k));
200 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
202 BN_set_flags(&k, BN_FLG_EXP_CONSTTIME);
205 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
207 if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
213 /* Compute r = (g^k mod p) mod q */
215 if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
217 if (!BN_copy(&kq, &k)) goto err;
219 /* We do not want timing information to leak the length of k,
220 * so we compute g^k using an equivalent exponent of fixed length.
222 * (This is a kludge that we need because the BN_mod_exp_mont()
223 * does not let us specify the desired timing behaviour.) */
225 if (!BN_add(&kq, &kq, dsa->q)) goto err;
226 if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
228 if (!BN_add(&kq, &kq, dsa->q)) goto err;
237 if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,K,dsa->p,ctx,
238 (BN_MONT_CTX *)dsa->method_mont_p)) goto err;
239 if (!BN_mod(r,r,dsa->q,ctx)) goto err;
241 /* Compute part of 's = inv(k) (m + xr) mod q' */
242 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
244 if (*kinvp != NULL) BN_clear_free(*kinvp);
247 if (*rp != NULL) BN_clear_free(*rp);
253 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
254 if (kinv != NULL) BN_clear_free(kinv);
255 if (r != NULL) BN_clear_free(r);
257 if (ctx_in == NULL) BN_CTX_free(ctx);
258 if (kinv != NULL) BN_clear_free(kinv);
264 static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
269 BN_MONT_CTX *mont=NULL;
271 if (!dsa->p || !dsa->q || !dsa->g)
273 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
277 if (BN_num_bits(dsa->q) != 160)
279 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
283 if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
285 DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
293 if ((ctx=BN_CTX_new()) == NULL) goto err;
295 if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0)
300 if (BN_is_zero(sig->s) || sig->s->neg || BN_ucmp(sig->s, dsa->q) >= 0)
306 /* Calculate W = inv(S) mod Q
308 if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
311 if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
313 /* u1 = M * w mod q */
314 if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
316 /* u2 = r * w mod q */
317 if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
320 if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
322 mont = BN_MONT_CTX_set_locked(
323 (BN_MONT_CTX **)&dsa->method_mont_p,
324 CRYPTO_LOCK_DSA, dsa->p, ctx);
334 /* v = ( g^u1 * y^u2 mod p ) mod q */
335 /* let t1 = g ^ u1 mod p */
336 if (!BN_mod_exp_mont(&t1,dsa->g,&u1,dsa->p,ctx,mont)) goto err;
337 /* let t2 = y ^ u2 mod p */
338 if (!BN_mod_exp_mont(&t2,dsa->pub_key,&u2,dsa->p,ctx,mont)) goto err;
339 /* let u1 = t1 * t2 mod p */
340 if (!BN_mod_mul(&u1,&t1,&t2,dsa->p,ctx)) goto err_bn;
343 /* let u1 = u1 mod q */
344 if (!BN_mod(&u1,&u1,dsa->q,ctx)) goto err;
347 if (!dsa->meth->dsa_mod_exp(dsa, &t1,dsa->g,&u1,dsa->pub_key,&u2,
348 dsa->p,ctx,mont)) goto err;
349 /* BN_copy(&u1,&t1); */
350 /* let u1 = u1 mod q */
351 if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
354 /* V is now in u1. If the signature is correct, it will be
356 ret=(BN_ucmp(&u1, sig->r) == 0);
359 if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
360 if (ctx != NULL) BN_CTX_free(ctx);
367 static int dsa_init(DSA *dsa)
369 dsa->flags|=DSA_FLAG_CACHE_MONT_P;
373 static int dsa_finish(DSA *dsa)
375 if(dsa->method_mont_p)
376 BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p);
380 static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
381 BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
382 BN_MONT_CTX *in_mont)
384 return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont);
387 static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
388 const BIGNUM *m, BN_CTX *ctx,
391 return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);