linux-kernel - Re: [PATCH 5/7] staging: usbip: Add encryption support to kernel

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Date:	Mon, 23 Sep 2013 13:58:42 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Dominik Paulus <dominik.paulus@....de>
Cc:	usbip-devel@...ts.sourceforge.net,
	Anthony Foiani <anthony.foiani@...il.com>,
	devel@...verdev.osuosl.org, linux-kernel@...cs.fau.de,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org,
	Kurt Kanzenbach <ly80toro@....cs.fau.de>,
	Tobias Polzer <tobias.polzer@....de>,
	Harvey Yang <harvey.huawei.yang@...il.com>,
	linux-kernel@...r.kernel.org,
	Ilija Hadzic <ihadzic@...earch.bell-labs.com>,
	Bart Westgeest <bart@...rys.com>,
	Joe Perches <joe@...ches.com>,
	Jake Champlin <jake.champlin.27@...il.com>,
	Stefan Reif <ke42caxa@....cs.fau.de>,
	Bernard Blackham <b-linuxgit@...gestprime.net>
Subject: Re: [PATCH 5/7] staging: usbip: Add encryption support to kernel

On Thu, Sep 19, 2013 at 04:11:57PM +0200, Dominik Paulus wrote:
> +/*
> + * Perform encryption/decryption on one chunk of data.
> + * Uses global crypto state stored in usbip_device.
> + * Parameters:
> + * encrypt: 1 to perform encryption, 0 to perform decryption operation

Make this a define:
#define USBIP_ENCRYPT 1
#define USBIP_ENCRYPT 0

> + * packetsize: Size of the encrypted packet, including the authentication tag,
> + * not including the associated data (length field).
> + * plaintext and ciphertext have to be appropiately managed by the caller
> + * (i.e. they must be at least packetsize bytes long).
> + * Returns: 0 on success
> + */
> +static int usbip_crypt(struct usbip_device *ud, int encrypt, uint32_t
> +		packetsize, unsigned char *plaintext, unsigned char
> +		*ciphertext)

Don't break put line breaks between the type and the variable name.  It
should be:

static int usbip_crypt(struct usbip_device *ud, int encrypt,
		uint32_t packetsize, unsigned char *plaintext,
		unsigned char *ciphertext)

This applies to earlier patches in this series as well.

> +{
> +	struct crypto_aead *tfm;
> +	struct aead_request *req;
> +	struct tcrypt_result result;
> +	struct scatterlist plain, cipher, assoc;
> +	char iv[16];
> +	u64 *iv_num;
> +	u64 iv_net;
> +	const int plainsize = packetsize - USBIP_AUTHSIZE;

Is it possible that packetsize is less than USBIP_AUTHSIZE?

> +	int ret;
> +
> +	memset(iv, 0, sizeof(iv));
> +	if (encrypt) {
> +		tfm = ud->tfm_send;
> +		iv_num = &ud->ctr_send;
> +	} else {
> +		tfm = ud->tfm_recv;
> +		iv_num = &ud->ctr_recv;
> +	}
> +	iv_net = cpu_to_be64(*iv_num);
> +	memcpy(iv, &iv_net, sizeof(iv_net));
> +
> +	req = aead_request_alloc(tfm, GFP_KERNEL);
> +	if (IS_ERR(req))
> +		return -PTR_ERR(req);
> +
> +	init_completion(&result.completion);
> +	aead_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
> +			tcrypt_complete, &result);

Align this up like:

	aead_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
				  tcrypt_complete, &result);


> +
> +	sg_init_one(&cipher, ciphertext, packetsize);
> +	sg_init_one(&plain, plaintext, plainsize);
> +	crypto_aead_clear_flags(tfm, ~0);
> +
> +	if (encrypt)
> +		aead_request_set_crypt(req, &plain, &cipher, plainsize, iv);
> +	else
> +		aead_request_set_crypt(req, &cipher, &plain, packetsize, iv);
> +	packetsize = cpu_to_be32(packetsize);
> +	sg_init_one(&assoc, &packetsize, sizeof(packetsize));
> +	/* Associated data: Unencrypted length tag */
> +	aead_request_set_assoc(req, &assoc, sizeof(packetsize));
> +
> +	if (encrypt)
> +		ret = crypto_aead_encrypt(req);
> +	else
> +		ret = crypto_aead_decrypt(req);
> +

Good on you for figuring out what crypto_aead_en/decrypt() returns.
Where are these functions documented?

> +	switch (ret) {
> +	case 0: /* Success */
> +		break;
> +	case -EINPROGRESS:
> +	case -EBUSY:
> +		wait_for_completion(&result.completion);
> +		break;
> +	default:
> +		aead_request_free(req);
> +		return ret;
> +	}
> +

regards,
dan carpenter

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