fix lading zeroes in PubKey generation

tools/itscertgen/generator/ecc_openssl.c

@@ -21,6 +21,7 @@
 
 #define ARRAYSIZE(A) (sizeof(A)/sizeof(A[0]))
 
+static char * _bin2hex(char * hex, int hlen, const char * bin, int blen);
 typedef struct {
 	int nid;
 	const char * name;
@@ -105,7 +106,6 @@ void * ecc_api_key_gen(ecc_pk_algorithm pk_alg, ecc_sym_algorithm sym_alg)
 		if (key){
 			EC_KEY_set_group(key, _curves[pk_alg]);
 			EC_KEY_set_asn1_flag(key, OPENSSL_EC_NAMED_CURVE);
-
 			if (!EC_KEY_generate_key(key)){
 				ERR_print_errors_fp(stderr);
 				fflush(stderr);
@@ -215,22 +215,19 @@ int    ecc_api_key_private_save(void* key, const char* path, ecc_format format)
 				const BIGNUM   * ecbn;
 				ecbn = EC_KEY_get0_private_key(eckey);
 				if (ecbn){
-					char * buf = NULL;
-					int len = BN_num_bytes(ecbn);
-					if (format == ecc_bin){
-						buf = (char *)OPENSSL_malloc(len);
-						BN_bn2bin(ecbn, (unsigned char *)buf);
-						rc = 0;
-					}
-					else if (format == ecc_hex){
-						buf = BN_bn2hex(ecbn);
-						len = strlen(buf);
+					int bnlen = BN_num_bytes(ecbn);
+					int len = (bnlen < 32) ? 32 : bnlen;
+					char * buf = (char *)OPENSSL_malloc(len*2+1);
+					if (bnlen < len) memset(buf, 0, len - bnlen);
+					BN_bn2bin(ecbn, (unsigned char *)(buf + len - bnlen));
+					if (format == ecc_hex){
+						char * c = _bin2hex(buf, len * 2 + 1, buf, len);
+						*c = 0;
+						len = c - buf;
 						rc = 0;
 					}
-					if (buf){
-						rc = (len == fwrite(buf, 1, len, f)) ? 0 : -1;
-						OPENSSL_free(buf);
-					}
+					rc = (len == fwrite(buf, 1, len, f)) ? 0 : -1;
+					OPENSSL_free(buf);
 				}
 			}
 			fclose(f);
@@ -465,3 +462,24 @@ int    ecc_sign(void * key, const char * data, int length, char ** psig, int max
 	}
 	return -1;
 }
+
+
+static const char* _hexDigits = "0123456789ABCDEF";
+static char * _bin2hex(char * hex, int hlen, const char * bin, int blen)
+{
+	const unsigned char *b, *e;
+	char * s;
+
+	// sanity check
+	if (hlen >= 0 && hlen < blen * 2) return NULL;
+
+	b = (const unsigned char *)bin;
+	e = b + blen - 1;
+	s = hex + blen * 2;
+	if (s < hex + hlen) *s = 0;
+	for (; b <= e; e--){
+		*(--s) = _hexDigits[(*e) & 0xF];
+		*(--s) = _hexDigits[(*e) >> 4];
+	}
+	return hex + blen * 2;
+}