Make D-H safer, include well-known primes.

4 files changed, 36 insertions, 0 deletions

diff --git a/crypto/dh/dh.h b/crypto/dh/dh.h
index d1559fd..7871882 100644
--- a/crypto/dh/dh.h
+++ b/crypto/dh/dh.h
@@ -145,6 +145,10 @@ struct dh_st
 #define DH_UNABLE_TO_CHECK_GENERATOR	0x04
 #define DH_NOT_SUITABLE_GENERATOR	0x08
 
+/* DH_check_pub_key error codes */
+#define DH_CHECK_PUBKEY_TOO_SMALL	0x01
+#define DH_CHECK_PUBKEY_TOO_LARGE	0x02
+
 /* primes p where (p-1)/2 is prime too are called "safe"; we define
    this for backward compatibility: */
 #define DH_CHECK_P_NOT_STRONG_PRIME	DH_CHECK_P_NOT_SAFE_PRIME
@@ -183,6 +187,7 @@ DH *	DH_generate_parameters(int prime_len,int generator,
 int	DH_generate_parameters_ex(DH *dh, int prime_len,int generator, BN_GENCB *cb);
 
 int	DH_check(const DH *dh,int *codes);
+int	DH_check_pub_key(const DH *dh,const BIGNUM *pub_key, int *codes);
 int	DH_generate_key(DH *dh);
 int	DH_compute_key(unsigned char *key,const BIGNUM *pub_key,DH *dh);
 DH *	d2i_DHparams(DH **a,const unsigned char **pp, long length);
@@ -216,6 +221,7 @@ void ERR_load_DH_strings(void);
 /* Reason codes. */
 #define DH_R_BAD_GENERATOR				 101
 #define DH_R_NO_PRIVATE_VALUE				 100
+#define DH_R_INVALID_PUBKEY				 102
 
 #ifdef  __cplusplus
 }
diff --git a/crypto/dh/dh_check.c b/crypto/dh/dh_check.c
index bfc9c3a..10217c8 100644
--- a/crypto/dh/dh_check.c
+++ b/crypto/dh/dh_check.c
@@ -118,3 +118,25 @@ err:
 	if (q != NULL) BN_free(q);
 	return(ok);
 	}
+
+int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
+	{
+	int ok=0;
+	BIGNUM *q=NULL;
+
+	*ret=0;
+	q=BN_new();
+	if (q == NULL) goto err;
+	BN_set_word(q,1);
+	if (BN_cmp(pub_key,q)<=0)
+		*ret|=DH_CHECK_PUBKEY_TOO_SMALL;
+	BN_copy(q,dh->p);
+	BN_sub_word(q,1);
+	if (BN_cmp(pub_key,q)>=0)
+		*ret|=DH_CHECK_PUBKEY_TOO_LARGE;
+
+	ok = 1;
+err:
+	if (q != NULL) BN_free(q);
+	return(ok);
+	}
diff --git a/crypto/dh/dh_err.c b/crypto/dh/dh_err.c
index edce2c7..ea67fb7 100644
--- a/crypto/dh/dh_err.c
+++ b/crypto/dh/dh_err.c
@@ -84,6 +84,7 @@ static ERR_STRING_DATA DH_str_reasons[]=
 	{
 {ERR_REASON(DH_R_BAD_GENERATOR)          ,"bad generator"},
 {ERR_REASON(DH_R_NO_PRIVATE_VALUE)       ,"no private value"},
+{ERR_REASON(DH_R_INVALID_PUBKEY)         ,"invalid public key"},
 {0,NULL}
 	};
 
diff --git a/crypto/dh/dh_key.c b/crypto/dh/dh_key.c
index 39eefe3..cc17c88 100644
--- a/crypto/dh/dh_key.c
+++ b/crypto/dh/dh_key.c
@@ -177,6 +177,7 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 	BN_MONT_CTX *mont=NULL;
 	BIGNUM *tmp;
 	int ret= -1;
+        int check_result;
 
 	ctx = BN_CTX_new();
 	if (ctx == NULL) goto err;
@@ -202,6 +203,12 @@ static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
 			goto err;
 		}
 
+        if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
+		{
+		DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
+		goto err;
+		}
+
 	if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
 		{
 		DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB);