srp_lib.c

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/* crypto/srp/srp_lib.c */
/* Written by Christophe Renou ([email protected]) with 
 * the precious help of Peter Sylvester ([email protected]) 
 * for the EdelKey project and contributed to the OpenSSL project 2004.
 */
/* ====================================================================
 * Copyright (c) 2004 The OpenSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    [email protected].
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * ([email protected]).  This product includes software written by Tim
 * Hudson ([email protected]).
 *
 */
#ifndef OPENSSL_NO_SRP
#include "cryptlib.h"
#include "srp_lcl.h"
#include <openssl/srp.h>
#include <openssl/evp.h>

#if (BN_BYTES == 8)
#define bn_pack4(a1,a2,a3,a4) 0x##a1##a2##a3##a4##ul
#endif
#if (BN_BYTES == 4)
#define bn_pack4(a1,a2,a3,a4)  0x##a3##a4##ul, 0x##a1##a2##ul
#endif
#if (BN_BYTES == 2)
#define bn_pack4(a1,a2,a3,a4) 0x##a4##u,0x##a3##u,0x##a2##u,0x##a1##u
#endif


#include "srp_grps.h"

static BIGNUM *srp_Calc_k(BIGNUM *N, BIGNUM *g)
    {
    /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */

    unsigned char digest[SHA_DIGEST_LENGTH];
    unsigned char *tmp;
    EVP_MD_CTX ctxt;
    int longg ;
    int longN = BN_num_bytes(N);

    if ((tmp = OPENSSL_malloc(longN)) == NULL)
        return NULL;
    BN_bn2bin(N,tmp) ;

    EVP_MD_CTX_init(&ctxt);
    EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
    EVP_DigestUpdate(&ctxt, tmp, longN);

    memset(tmp, 0, longN);
    longg = BN_bn2bin(g,tmp) ;
        /* use the zeros behind to pad on left */
    EVP_DigestUpdate(&ctxt, tmp + longg, longN-longg);
    EVP_DigestUpdate(&ctxt, tmp, longg);
    OPENSSL_free(tmp);

    EVP_DigestFinal_ex(&ctxt, digest, NULL);
    EVP_MD_CTX_cleanup(&ctxt);
    return BN_bin2bn(digest, sizeof(digest), NULL); 
    }

BIGNUM *SRP_Calc_u(BIGNUM *A, BIGNUM *B, BIGNUM *N)
    {
    /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */

    BIGNUM *u;  
    unsigned char cu[SHA_DIGEST_LENGTH];
    unsigned char *cAB;
    EVP_MD_CTX ctxt;
    int longN;  
    if ((A == NULL) ||(B == NULL) || (N == NULL))
        return NULL;

    longN= BN_num_bytes(N);

    if ((cAB = OPENSSL_malloc(2*longN)) == NULL) 
        return NULL;

    memset(cAB, 0, longN);

    EVP_MD_CTX_init(&ctxt);
    EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
    EVP_DigestUpdate(&ctxt, cAB + BN_bn2bin(A,cAB+longN), longN);
    EVP_DigestUpdate(&ctxt, cAB + BN_bn2bin(B,cAB+longN), longN);
    OPENSSL_free(cAB);
    EVP_DigestFinal_ex(&ctxt, cu, NULL);
    EVP_MD_CTX_cleanup(&ctxt);

    if (!(u = BN_bin2bn(cu, sizeof(cu), NULL)))
        return NULL;
    if (!BN_is_zero(u))
        return u;
    BN_free(u);
    return NULL;
}

BIGNUM *SRP_Calc_server_key(BIGNUM *A, BIGNUM *v, BIGNUM *u, BIGNUM *b, BIGNUM *N)
    {
    BIGNUM *tmp = NULL, *S = NULL;
    BN_CTX *bn_ctx; 
    
    if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)
        return NULL; 

    if ((bn_ctx = BN_CTX_new()) == NULL ||
        (tmp = BN_new()) == NULL ||
        (S = BN_new()) == NULL )
        goto err;

    /* S = (A*v**u) ** b */ 

    if (!BN_mod_exp(tmp,v,u,N,bn_ctx))
        goto err;
    if (!BN_mod_mul(tmp,A,tmp,N,bn_ctx))
        goto err;
    if (!BN_mod_exp(S,tmp,b,N,bn_ctx))
        goto err;
err:
    BN_CTX_free(bn_ctx);
    BN_clear_free(tmp);
    return S;
    }

BIGNUM *SRP_Calc_B(BIGNUM *b, BIGNUM *N, BIGNUM *g, BIGNUM *v)
    {
    BIGNUM  *kv = NULL, *gb = NULL;
    BIGNUM *B = NULL, *k = NULL;
    BN_CTX *bn_ctx;

    if (b == NULL || N == NULL || g == NULL || v == NULL ||
        (bn_ctx = BN_CTX_new()) == NULL)
        return NULL; 

    if ( (kv = BN_new()) == NULL ||
        (gb = BN_new()) == NULL ||
        (B = BN_new())== NULL)
        goto err;

    /* B = g**b + k*v */

    if (!BN_mod_exp(gb,g,b,N,bn_ctx) ||
       !(k = srp_Calc_k(N,g)) ||
       !BN_mod_mul(kv,v,k,N,bn_ctx) || 
       !BN_mod_add(B,gb,kv,N,bn_ctx))
        {
        BN_free(B);
        B = NULL;
        }
err:
    BN_CTX_free(bn_ctx);
    BN_clear_free(kv);
    BN_clear_free(gb);
    BN_free(k); 
    return B;
    }

BIGNUM *SRP_Calc_x(BIGNUM *s, const char *user, const char *pass)
    {
    unsigned char dig[SHA_DIGEST_LENGTH];
    EVP_MD_CTX ctxt;
    unsigned char *cs;

    if ((s == NULL) ||
        (user == NULL) ||
        (pass == NULL))
        return NULL;

    if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)
        return NULL;

    EVP_MD_CTX_init(&ctxt);
    EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
    EVP_DigestUpdate(&ctxt, user, strlen(user));
    EVP_DigestUpdate(&ctxt, ":", 1);
    EVP_DigestUpdate(&ctxt, pass, strlen(pass));
    EVP_DigestFinal_ex(&ctxt, dig, NULL);

    EVP_DigestInit_ex(&ctxt, EVP_sha1(), NULL);
    BN_bn2bin(s,cs);
    EVP_DigestUpdate(&ctxt, cs, BN_num_bytes(s));
    OPENSSL_free(cs);
    EVP_DigestUpdate(&ctxt, dig, sizeof(dig));
    EVP_DigestFinal_ex(&ctxt, dig, NULL);
    EVP_MD_CTX_cleanup(&ctxt);

    return BN_bin2bn(dig, sizeof(dig), NULL);
    }

BIGNUM *SRP_Calc_A(BIGNUM *a, BIGNUM *N, BIGNUM *g)
    {
    BN_CTX *bn_ctx; 
    BIGNUM * A = NULL;

    if (a == NULL || N == NULL || g == NULL ||
        (bn_ctx = BN_CTX_new()) == NULL) 
        return NULL;

    if ((A = BN_new()) != NULL &&
       !BN_mod_exp(A,g,a,N,bn_ctx))
        {
        BN_free(A);
        A = NULL;
        }
    BN_CTX_free(bn_ctx);
    return A;
    }


BIGNUM *SRP_Calc_client_key(BIGNUM *N, BIGNUM *B, BIGNUM *g, BIGNUM *x, BIGNUM *a, BIGNUM *u)
    {
    BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL , *k = NULL, *K = NULL;
    BN_CTX *bn_ctx;

    if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL || a == NULL ||
        (bn_ctx = BN_CTX_new()) == NULL)
        return NULL; 

    if ((tmp = BN_new()) == NULL ||
        (tmp2 = BN_new())== NULL ||
        (tmp3 = BN_new())== NULL ||
        (K = BN_new()) == NULL)
        goto err;
    
    if (!BN_mod_exp(tmp,g,x,N,bn_ctx))
        goto err;
    if (!(k = srp_Calc_k(N,g)))
        goto err;
    if (!BN_mod_mul(tmp2,tmp,k,N,bn_ctx))
        goto err;
    if (!BN_mod_sub(tmp,B,tmp2,N,bn_ctx))
        goto err;

    if (!BN_mod_mul(tmp3,u,x,N,bn_ctx))
        goto err;
    if (!BN_mod_add(tmp2,a,tmp3,N,bn_ctx))
        goto err;
    if (!BN_mod_exp(K,tmp,tmp2,N,bn_ctx))
        goto err;

err :
    BN_CTX_free(bn_ctx);
    BN_clear_free(tmp);
    BN_clear_free(tmp2);
    BN_clear_free(tmp3);
    BN_free(k);
    return K;   
    }

int SRP_Verify_B_mod_N(BIGNUM *B, BIGNUM *N)
    {
    BIGNUM *r;
    BN_CTX *bn_ctx; 
    int ret = 0;

    if (B == NULL || N == NULL ||
        (bn_ctx = BN_CTX_new()) == NULL)
        return 0;

    if ((r = BN_new()) == NULL)
        goto err;
    /* Checks if B % N == 0 */
    if (!BN_nnmod(r,B,N,bn_ctx))
        goto err;
    ret = !BN_is_zero(r);
err:
    BN_CTX_free(bn_ctx);
    BN_free(r);
    return ret;
    }

int SRP_Verify_A_mod_N(BIGNUM *A, BIGNUM *N)
    {
    /* Checks if A % N == 0 */
    return SRP_Verify_B_mod_N(A,N) ;
    }


/* Check if G and N are kwown parameters. 
   The values have been generated from the ietf-tls-srp draft version 8
*/
char *SRP_check_known_gN_param(BIGNUM *g, BIGNUM *N)
    {
    size_t i;
    if ((g == NULL) || (N == NULL))
        return 0;

    srp_bn_print(g);
    srp_bn_print(N);

    for(i = 0; i < KNOWN_GN_NUMBER; i++)
        {
        if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0) 
            return knowngN[i].id;
        }
    return NULL;
    }

SRP_gN *SRP_get_default_gN(const char *id)
    {
    size_t i;

    if (id == NULL) 
        return knowngN;
    for(i = 0; i < KNOWN_GN_NUMBER; i++)
        {
        if (strcmp(knowngN[i].id, id)==0)
            return knowngN + i;
        }
    return NULL;
    }
#endif