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:
static void ep4_mul_sim_plain(ep4_t r, const ep4_t p, const bn_t k,
		const ep4_t q, const bn_t m, ep4_t *t) {
	int i, l, l0, l1, n0, n1, w, gen;
	int8_t naf0[2 * RLC_FP_BITS + 1], naf1[2 * RLC_FP_BITS + 1], *_k, *_m;
	ep4_t t0[1 << (EP_WIDTH - 2)];
	ep4_t t1[1 << (EP_WIDTH - 2)];

	RLC_TRY {
		gen = (t == NULL ? 0 : 1);
		if (!gen) {
			for (i = 0; i < (1 << (EP_WIDTH - 2)); i++) {
				ep4_null(t0[i]);
				ep4_new(t0[i]);
			}
			ep4_tab(t0, p, EP_WIDTH);
			t = (ep4_t *)t0;
		}

		/* Prepare the precomputation table. */
		for (i = 0; i < (1 << (EP_WIDTH - 2)); i++) {
			ep4_null(t1[i]);
			ep4_new(t1[i]);
		}
		/* Compute the precomputation table. */
		ep4_tab(t1, q, EP_WIDTH);

		/* Compute the w-TNAF representation of k. */
		if (gen) {
			w = EP_DEPTH;
		} else {
			w = EP_WIDTH;
		}
		l0 = l1 = 2 * RLC_FP_BITS + 1;
		bn_rec_naf(naf0, &l0, k, w);
		bn_rec_naf(naf1, &l1, m, EP_WIDTH);

		l = RLC_MAX(l0, l1);
		_k = naf0 + l - 1;
		_m = naf1 + l - 1;
		if (bn_sign(k) == RLC_NEG) {
			for (i =  0; i < l0; i++) {
				naf0[i] = -naf0[i];
			}
		}
		if (bn_sign(m) == RLC_NEG) {
			for (i =  0; i < l1; i++) {
				naf1[i] = -naf1[i];
			}
		}

		ep4_set_infty(r);
		for (i = l - 1; i >= 0; i--, _k--, _m--) {
			ep4_dbl(r, r);

			n0 = *_k;
			n1 = *_m;
			if (n0 > 0) {
				ep4_add(r, r, t[n0 / 2]);
			}
			if (n0 < 0) {
				ep4_sub(r, r, t[-n0 / 2]);
			}
			if (n1 > 0) {
				ep4_add(r, r, t1[n1 / 2]);
			}
			if (n1 < 0) {
				ep4_sub(r, r, t1[-n1 / 2]);
			}
		}
		/* Convert r to affine coordinates. */
		ep4_norm(r, r);
	}
	RLC_CATCH_ANY {
		RLC_THROW(ERR_CAUGHT);
	}
	RLC_FINALLY {
		/* Free the precomputation tables. */
		if (!gen) {
			for (i = 0; i < (1 << (EP_WIDTH - 2)); i++) {
				ep4_free(t0[i]);
			}
		}
		for (i = 0; i < (1 << (EP_WIDTH - 2)); i++) {
			ep4_free(t1[i]);
		}
	}
}