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authorDr. Stephen Henson <steve@openssl.org>2012-04-07 17:40:08 +0000
committerDr. Stephen Henson <steve@openssl.org>2012-04-07 17:40:08 +0000
commitb73a69a9c2e1c922ac7917f13a4911fb995ba0d6 (patch)
treec2b49f74837484a271a257402e424865e3ef1ed9 /crypto/dh
parente811eff5a9afcb35831823da3f467610de00c03a (diff)
Update DH_check() to peform sensible checks when q parameter is present.
(backport from HEAD)
Diffstat (limited to 'crypto/dh')
-rw-r--r--crypto/dh/dh.h3
-rw-r--r--crypto/dh/dh_check.c48
2 files changed, 42 insertions, 9 deletions
diff --git a/crypto/dh/dh.h b/crypto/dh/dh.h
index 027462d45b..c1440fb9b3 100644
--- a/crypto/dh/dh.h
+++ b/crypto/dh/dh.h
@@ -163,6 +163,9 @@ 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
diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
index 066898174e..fa1df0efc0 100644
--- a/crypto/dh/dh_check.c
+++ b/crypto/dh/dh_check.c
@@ -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);
}