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_cmlhs_sig(g1_t sig, g2_t z, g1_t a, g1_t c, g1_t r, g2_t s,
		const bn_t msg, const char *data, int label, const bn_t x, const g1_t h,
		const uint8_t prf[], size_t plen, const bn_t d, const bn_t sk,
		int bls) {
	bn_t k, m, n;
	g1_t t;
	uint8_t mac[RLC_MD_LEN];
	int len, dlen = strlen(data), result = RLC_OK;
	uint8_t *buf = RLC_ALLOCA(uint8_t, 1 + 8 * RLC_PC_BYTES + dlen);

	bn_null(k);
	bn_null(m);
	bn_null(n);
	g1_null(t);

	RLC_TRY {
		bn_new(k);
		bn_new(m);
		bn_new(n);
		g1_new(t);
		if (buf == NULL) {
			RLC_THROW(ERR_NO_MEMORY);
		}

		pc_get_ord(n);
		/* Generate r and s. */
		bn_rand_mod(k, n);
		bn_rand_mod(m, n);

		/* Compute S = -g2^s, C = g1^s. */
		g2_mul_gen(s, m);
		g2_neg(s, s);
		g1_mul_gen(c, m);
		/* Compute R = g1^(r - ys). */
		bn_mul(m, d, m);
		bn_mod(m, m, n);
		bn_sub(m, k, m);
		bn_mod(m, m, n);
		g1_mul_gen(r, m);

		/* Compute A = g1^(x + r) * \prod H_j^(y * m_j). */
		bn_add(k, x, k);
		bn_mod(k, k, n);
		g1_mul_gen(a, k);
		bn_mul(k, d, msg);
		bn_mod(k, k, n);
		g1_mul(t, h, k);
		g1_add(a, a, t);
		g1_norm(a, a);
		/* Compute z = F_K(delta), Z = g2^z, A = A^(1/z). */
		md_hmac(mac, (const uint8_t *)data, dlen, prf, plen);
		bn_read_bin(k, mac, RLC_MD_LEN);
		bn_mod(k, k, n);
		g2_mul_gen(z, k);
		bn_mod_inv(k, k, n);
		g1_mul(a, a, k);

		/* Compute C = C * sum H_j^m_j. */
		bn_mod(k, msg, n);
		g1_mul(t, h, k);
		g1_add(c, c, t);
		g1_norm(c, c);

		len = g2_size_bin(z, 0);
		g2_write_bin(buf, len, z, 0);
		memcpy(buf + len, data, dlen);
		if (bls) {
			cp_bls_sig(sig, buf, len + dlen, sk);
		} else {
			cp_ecdsa_sig(m, n, buf, len + dlen, 0, sk);
			fp_prime_conv(sig->x, m);
			fp_prime_conv(sig->y, n);
			fp_set_dig(sig->z, 1);
		}
	}
	RLC_CATCH_ANY {
		result = RLC_ERR;
	}
	RLC_FINALLY {
		bn_free(k);
		bn_free(m);
		bn_free(n);
		g1_free(t);
		RLC_FREE(buf);
	}
	return result;
}