checking mpz_export return value properly

fixes a potential DoS attack if a DH value of zero gets processed

src/libstrongswan/plugins/gmp/gmp_diffie_hellman.c

@@ -441,6 +441,10 @@ static status_t get_other_public_value(private_gmp_diffie_hellman_t *this,
 	}
 	value->len = this->p_len;
 	value->ptr = mpz_export(NULL, NULL, 1, value->len, 1, 0, this->yb);
+	if (value->ptr == NULL)
+	{
+		return FAILED;
+	}
 	return SUCCESS;
 }
 
@@ -451,6 +455,10 @@ static void get_my_public_value(private_gmp_diffie_hellman_t *this,chunk_t *valu
 {
 	value->len = this->p_len;
     value->ptr = mpz_export(NULL, NULL, 1, value->len, 1, 0, this->ya);
+    if (value->ptr == NULL)
+    {
+    	value->len = 0;
+    }
 }
 
 /**
@@ -464,6 +472,10 @@ static status_t get_shared_secret(private_gmp_diffie_hellman_t *this, chunk_t *s
 	}
 	secret->len = this->p_len;
 	secret->ptr = mpz_export(NULL, NULL, 1, secret->len, 1, 0, this->zz);
+	if (secret->ptr == NULL)
+	{
+		return FAILED;
+	}
 	return SUCCESS;
 }
 

src/libstrongswan/plugins/gmp/gmp_rsa_private_key.c

@@ -191,6 +191,10 @@ static chunk_t rsadp(private_gmp_rsa_private_key_t *this, chunk_t data)
 	
 	decrypted.len = this->k;
 	decrypted.ptr = mpz_export(NULL, NULL, 1, decrypted.len, 1, 0, t1);
+	if (decrypted.ptr == NULL)
+	{
+		decrypted.len = 0;
+	}
 	
 	mpz_clear_randomized(t1);
 	mpz_clear_randomized(t2);

src/libstrongswan/plugins/gmp/gmp_rsa_public_key.c

@@ -95,6 +95,10 @@ static chunk_t rsaep(private_gmp_rsa_public_key_t *this, chunk_t data)
 
 	encrypted.len = this->k;
 	encrypted.ptr = mpz_export(NULL, NULL, 1, encrypted.len, 1, 0, c);
+	if (encrypted.ptr == NULL)
+	{
+		encrypted.len = 0;
+	}
 	
 	mpz_clear(c);
 	mpz_clear(m);

src/openac/openac.c

@@ -103,6 +103,10 @@ static chunk_t mpz_to_chunk(mpz_t number)
 
 	chunk.len = 1 + mpz_sizeinbase(number, 2)/BITS_PER_BYTE;
 	chunk.ptr = mpz_export(NULL, NULL, 1, chunk.len, 1, 0, number);
+	if (chunk.ptr == NULL)
+	{
+		chunk.len = 0;
+	}
 	return chunk;
 }