int tb_domain_challenge_switch_key()

in domain.c [708:770]

• 48 lines of code
• 11 McCabe index (conditional complexity)

int tb_domain_challenge_switch_key(struct tb *tb, struct tb_switch *sw)
{
	u8 challenge[TB_SWITCH_KEY_SIZE];
	u8 response[TB_SWITCH_KEY_SIZE];
	u8 hmac[TB_SWITCH_KEY_SIZE];
	struct tb_switch *parent_sw;
	struct crypto_shash *tfm;
	struct shash_desc *shash;
	int ret;

	if (!tb->cm_ops->approve_switch || !tb->cm_ops->challenge_switch_key)
		return -EPERM;

	/* The parent switch must be authorized before this one */
	parent_sw = tb_to_switch(sw->dev.parent);
	if (!parent_sw || !parent_sw->authorized)
		return -EINVAL;

	get_random_bytes(challenge, sizeof(challenge));
	ret = tb->cm_ops->challenge_switch_key(tb, sw, challenge, response);
	if (ret)
		return ret;

	tfm = crypto_alloc_shash("hmac(sha256)", 0, 0);
	if (IS_ERR(tfm))
		return PTR_ERR(tfm);

	ret = crypto_shash_setkey(tfm, sw->key, TB_SWITCH_KEY_SIZE);
	if (ret)
		goto err_free_tfm;

	shash = kzalloc(sizeof(*shash) + crypto_shash_descsize(tfm),
			GFP_KERNEL);
	if (!shash) {
		ret = -ENOMEM;
		goto err_free_tfm;
	}

	shash->tfm = tfm;

	memset(hmac, 0, sizeof(hmac));
	ret = crypto_shash_digest(shash, challenge, sizeof(hmac), hmac);
	if (ret)
		goto err_free_shash;

	/* The returned HMAC must match the one we calculated */
	if (memcmp(response, hmac, sizeof(hmac))) {
		ret = -EKEYREJECTED;
		goto err_free_shash;
	}

	crypto_free_shash(tfm);
	kfree(shash);

	return tb->cm_ops->approve_switch(tb, sw);

err_free_shash:
	kfree(shash);
err_free_tfm:
	crypto_free_shash(tfm);

	return ret;
}