1 /* crypto/dsa/dsa_sign.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> */
68 /* data has already been hashed (probably with SHA or SHA-1). */
69 /* DSAerr(DSA_F_DSA_SIGN,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); */
71 int DSA_sign(type,dgst,dlen,sig,siglen,dsa)
75 unsigned char *sig; /* out */
76 unsigned int *siglen; /* out */
79 BIGNUM *kinv=NULL,*r=NULL;
84 int i,len=0,ret=0,reason=ERR_R_BN_LIB;
86 MS_STATIC unsigned char rbuf[50]; /* assuming r is 20 bytes +extra */
87 MS_STATIC unsigned char sbuf[50]; /* assuming s is 20 bytes +extra */
93 i=BN_num_bytes(dsa->q); /* should be 20 */
94 if ((dlen > i) || (dlen > 50))
96 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
101 if (ctx == NULL) goto err;
103 if ((dsa->kinv == NULL) || (dsa->r == NULL))
105 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
115 if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err;
117 /* Compute s = inv(k) (m + xr) mod q */
118 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
119 if (!BN_add(&s, &xr, &m)) goto err; /* s = m + xr */
120 if (BN_cmp(&s,dsa->q) > 0)
121 BN_sub(&s,&s,dsa->q);
122 if (!BN_mod_mul(&s,&s,kinv,dsa->q,ctx)) goto err;
125 * Now create a ASN.1 sequence of the integers R and S.
129 rbs.type = V_ASN1_INTEGER;
130 sbs.type = V_ASN1_INTEGER;
131 rbs.length=BN_bn2bin(r,rbs.data);
132 sbs.length=BN_bn2bin(&s,sbs.data);
134 len =i2d_ASN1_INTEGER(&rbs,NULL);
135 len+=i2d_ASN1_INTEGER(&sbs,NULL);
138 ASN1_put_object(&p,1,len,V_ASN1_SEQUENCE,V_ASN1_UNIVERSAL);
139 i2d_ASN1_INTEGER(&rbs,&p);
140 i2d_ASN1_INTEGER(&sbs,&p);
144 if (!ret) DSAerr(DSA_F_DSA_SIGN,reason);
146 #if 1 /* do the right thing :-) */
147 if (kinv != NULL) BN_clear_free(kinv);
148 if (r != NULL) BN_clear_free(r);
150 if (ctx != NULL) BN_CTX_free(ctx);
157 int DSA_sign_setup(dsa,ctx_in,kinvp,rp)
164 BIGNUM k,*kinv=NULL,*r=NULL;
169 if ((ctx=BN_CTX_new()) == NULL) goto err;
175 if ((r=BN_new()) == NULL) goto err;
181 if (!BN_rand(&k, BN_num_bits(dsa->q), 1, 0)) goto err;
182 if (BN_cmp(&k,dsa->q) >= 0)
183 BN_sub(&k,&k,dsa->q);
184 if (!BN_is_zero(&k)) break;
187 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
189 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
190 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
191 dsa->p,ctx)) goto err;
194 /* Compute r = (g^k mod p) mod q */
195 if (!BN_mod_exp_mont(r,dsa->g,&k,dsa->p,ctx,
196 (BN_MONT_CTX *)dsa->method_mont_p)) goto err;
197 if (!BN_mod(r,r,dsa->q,ctx)) goto err;
199 /* Compute part of 's = inv(k) (m + xr) mod q' */
200 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
202 if (*kinvp != NULL) BN_clear_free(*kinvp);
205 if (*rp != NULL) BN_clear_free(*rp);
211 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
212 if (kinv != NULL) BN_clear_free(kinv);
213 if (r != NULL) BN_clear_free(r);
215 if (ctx_in == NULL) BN_CTX_free(ctx);
216 if (kinv != NULL) BN_clear_free(kinv);