fix BN serialization padding (thanks Michal Kazmierowski)

tools/itscertgen/generator/ecc_openssl.c

@@ -19,6 +19,8 @@
 #include <openssl/ecdsa.h>
 #include <string.h>
 
+#define FIELD_SIZE 32
+
 #define ARRAYSIZE(A) (sizeof(A)/sizeof(A[0]))
 
 static char * _bin2hex(char * hex, int hlen, const char * bin, int blen);
@@ -172,6 +174,7 @@ int    ecc_api_key_public(void* key, char * px, char * py)
 	BIGNUM x, y;
 	int bcount = -1;
 
+	if( key && px && py ) {
 		ecgroup = EC_KEY_get0_group(eckey);
 		ecpoint = EC_KEY_get0_public_key(eckey);
 
@@ -179,16 +182,17 @@ int    ecc_api_key_public(void* key, char * px, char * py)
 		BN_init(&x); BN_init(&y);
 		if (EC_POINT_get_affine_coordinates_GFp(ecgroup, ecpoint, &x, &y, NULL)){
 			bcount = BN_num_bytes(&x);
-		if (px){
+			for(; bcount < FIELD_SIZE; bcount++)
+				*(px++) = 0; // add padding with zeros
 			BN_bn2bin(&x, (unsigned char*)px);
-		}
 	
 			bcount = BN_num_bytes(&y);
-		if (py){
+			for(; bcount < FIELD_SIZE; bcount++)
+				*(py++) = 0; // add padding with zeros
 			BN_bn2bin(&y, (unsigned char*)py);
 		}
-	}
 		BN_clear_free(&x); BN_clear_free(&y);
+	}
 	return bcount;
 }
 
@@ -446,12 +450,16 @@ int    ecc_sign(void * key, const char * data, int length, char ** psig, int max
 			ecdsa = ECDSA_do_sign(hash, 32, eckey);
 			EC_KEY_free(eckey);
 			if (ecdsa){
-				int bcount;
+				int i, bcount;
 				*(sig++) = 0; // ECC_POINT type (x_coordinate_only)
 				bcount = BN_num_bytes(ecdsa->r);
+				for(i=bcount; i < FIELD_SIZE; i++)
+					*(sig++) = 0; // add padding with zeros
 				BN_bn2bin(ecdsa->r, sig);
 				sig += bcount;
 				bcount = BN_num_bytes(ecdsa->s);
+				for(i=bcount; i < FIELD_SIZE; i++)
+					*(sig++) = 0; // add padding with zeros
 				BN_bn2bin(ecdsa->s, sig);
 				sig += bcount;
 				ECDSA_SIG_free(ecdsa);