Language: C
Label: vulnerable
CWE: CWE-190 \u2014 Integer Overflow or Wraparound
The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control.

Code:
int cp_vbnn_ver(const ec_t r, const bn_t z, const bn_t h, const uint8_t *id,
		size_t id_len, const uint8_t *msg, int msg_len, const ec_t mpk) {
	int len, result = 0;
	uint8_t *buf = NULL, *buf_i, hash[RLC_MD_LEN];
	bn_t n, c, _h;
	ec_t Z;
	ec_t t;

	/* zero variables */
	bn_null(n);
	bn_null(c);
	bn_null(_h);
	ec_null(Z);
	ec_null(t);

	RLC_TRY {
		bn_new(n);
		bn_new(c);
		bn_new(_h);
		ec_new(Z);
		ec_new(t);

		/* calculate c */
		len = id_len + msg_len + 2 * ec_size_bin(r, 1);
		buf = RLC_ALLOCA(uint8_t, len);
		if (buf == NULL) {
			RLC_THROW(ERR_NO_MEMORY);
		}

		/* get order of ECC group */
		ec_curve_get_ord(n);

		buf_i = buf;
		memcpy(buf_i, id, id_len);
		buf_i += id_len;
		ec_write_bin(buf_i, ec_size_bin(r, 1), r, 1);

		len = id_len + ec_size_bin(r, 1);
		md_map(hash, buf, len);
		bn_read_bin(c, hash, RLC_MD_LEN);
		bn_mod(c, c, n);

		/* calculate Z */
		ec_mul_gen(Z, z);
		ec_mul(t, mpk, c);
		ec_add(t, t, r);
		ec_norm(t, t);
		ec_mul(t, t, h);
		ec_sub(Z, Z, t);
		ec_norm(Z, Z);

		/* calculate h_verify */
		buf_i = buf;
		memcpy(buf_i, id, id_len);
		buf_i += id_len;
		memcpy(buf_i, msg, msg_len);
		buf_i += msg_len;
		ec_write_bin(buf_i, ec_size_bin(r, 1), r, 1);
		buf_i += ec_size_bin(r, 1);
		ec_write_bin(buf_i, ec_size_bin(Z, 1), Z, 1);

		len = id_len + msg_len + ec_size_bin(r, 1) + ec_size_bin(Z, 1);
		md_map(hash, buf, len);
		bn_read_bin(_h, hash, RLC_MD_LEN);
		bn_mod(_h, _h, n);
		RLC_FREE(buf);

		if (bn_cmp(h, _h) == RLC_EQ) {
			result = 1;
		} else {
			result = 0;
		}
	}
	RLC_CATCH_ANY {
		RLC_THROW(ERR_CAUGHT);
	}
	RLC_FINALLY {
		/* free variables */
		bn_free(n);
		bn_free(c);
		bn_free(_h);
		ec_free(Z);
		ec_free(t);
		RLC_FREE(buf);
	}
	return result;
}