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Update DH_check() to peform sensible checks when q parameter is present.

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This commit is contained in:
Dr. Stephen Henson 2011-12-01 17:27:36 +00:00
parent 28ff14779e
commit 0798170966
2 changed files with 42 additions and 9 deletions
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3
crypto/dh/dh.h
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@ -165,6 +165,9 @@ struct dh_st
#define DH_CHECK_P_NOT_SAFE_PRIME 0x02
#define DH_UNABLE_TO_CHECK_GENERATOR 0x04
#define DH_NOT_SUITABLE_GENERATOR 0x08
#define DH_CHECK_Q_NOT_PRIME 0x10
#define DH_CHECK_INVALID_Q_VALUE 0x20
#define DH_CHECK_INVALID_J_VALUE 0x40
/* DH_check_pub_key error codes */
#define DH_CHECK_PUBKEY_TOO_SMALL 0x01

48
crypto/dh/dh_check.c
View File

@ -75,15 +75,42 @@ int DH_check(const DH *dh, int *ret)
int ok=0;
BN_CTX *ctx=NULL;
BN_ULONG l;
BIGNUM *q=NULL;
BIGNUM *t1=NULL, *t2 = NULL;
*ret=0;
ctx=BN_CTX_new();
if (ctx == NULL) goto err;
q=BN_new();
if (q == NULL) goto err;
BN_CTX_start(ctx);
t1=BN_CTX_get(ctx);
t2=BN_CTX_get(ctx);
if (t2 == NULL) goto err;
if (BN_is_word(dh->g,DH_GENERATOR_2))
if (dh->q)
{
if (BN_cmp(dh->g, BN_value_one()) <= 0)
*ret|=DH_NOT_SUITABLE_GENERATOR;
else if (BN_cmp(dh->g, dh->p) >= 0)
*ret|=DH_NOT_SUITABLE_GENERATOR;
else
{
/* Check g^q == 1 mod p */
if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
goto err;
if (!BN_is_one(t1))
*ret|=DH_NOT_SUITABLE_GENERATOR;
}
if (!BN_is_prime_ex(dh->q,BN_prime_checks,ctx,NULL))
*ret|=DH_CHECK_Q_NOT_PRIME;
/* Check p == 1 mod q i.e. q divides p - 1 */
if (!BN_div(t1, t2, dh->p, dh->q, ctx))
goto err;
if (!BN_is_one(t2))
*ret|=DH_CHECK_INVALID_Q_VALUE;
if (dh->j && BN_cmp(dh->j, t1))
*ret|=DH_CHECK_INVALID_J_VALUE;
}
else if (BN_is_word(dh->g,DH_GENERATOR_2))
{
l=BN_mod_word(dh->p,24);
if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR;
@ -106,16 +133,19 @@ int DH_check(const DH *dh, int *ret)
if (!BN_is_prime_ex(dh->p,BN_prime_checks,ctx,NULL))
*ret|=DH_CHECK_P_NOT_PRIME;
else
else if (!dh->q)
{
if (!BN_rshift1(q,dh->p)) goto err;
if (!BN_is_prime_ex(q,BN_prime_checks,ctx,NULL))
if (!BN_rshift1(t1,dh->p)) goto err;
if (!BN_is_prime_ex(t1,BN_prime_checks,ctx,NULL))
*ret|=DH_CHECK_P_NOT_SAFE_PRIME;
}
ok=1;
err:
if (ctx != NULL) BN_CTX_free(ctx);
if (q != NULL) BN_free(q);
if (ctx != NULL)
{
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return(ok);
}