drivers/usb/wusbcore/crypto.c - kernel/msm-4.9 - Gitiles

 /*
  * Ultra Wide Band
  * AES-128 CCM Encryption
  *
  * Copyright (C) 2007 Intel Corporation
  * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License version
  * 2 as published by the Free Software Foundation.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301, USA.
  *
  *
  * We don't do any encryption here; we use the Linux Kernel's AES-128
  * crypto modules to construct keys and payload blocks in a way
  * defined by WUSB1.0[6]. Check the erratas, as typos are are patched
  * there.
  *
  * Thanks a zillion to John Keys for his help and clarifications over
  * the designed-by-a-committee text.
  *
  * So the idea is that there is this basic Pseudo-Random-Function
  * defined in WUSB1.0[6.5] which is the core of everything. It works
  * by tweaking some blocks, AES crypting them and then xoring
  * something else with them (this seems to be called CBC(AES) -- can
  * you tell I know jack about crypto?). So we just funnel it into the
  * Linux Crypto API.
  *
  * We leave a crypto test module so we can verify that vectors match,
  * every now and then.
  *
  * Block size: 16 bytes -- AES seems to do things in 'block sizes'. I
  *             am learning a lot...
  *
  *             Conveniently, some data structures that need to be
  *             funneled through AES are...16 bytes in size!
  */

 #include <linux/crypto.h>
 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/uwb.h>
 #include <linux/usb/wusb.h>
 #include <linux/scatterlist.h>

 static int debug_crypto_verify = 0;

 module_param(debug_crypto_verify, int, 0);
 MODULE_PARM_DESC(debug_crypto_verify, "verify the key generation algorithms");

 static void wusb_key_dump(const void *buf, size_t len)
 {
 	print_hex_dump(KERN_ERR, "  ", DUMP_PREFIX_OFFSET, 16, 1,
 		       buf, len, 0);
 }

 /*
  * Block of data, as understood by AES-CCM
  *
  * The code assumes this structure is nothing but a 16 byte array
  * (packed in a struct to avoid common mess ups that I usually do with
  * arrays and enforcing type checking).
  */
 struct aes_ccm_block {
 	u8 data[16];
 } __attribute__((packed));

 /*
  * Counter-mode Blocks (WUSB1.0[6.4])
  *
  * According to CCM (or so it seems), for the purpose of calculating
  * the MIC, the message is broken in N counter-mode blocks, B0, B1,
  * ... BN.
  *
  * B0 contains flags, the CCM nonce and l(m).
  *
  * B1 contains l(a), the MAC header, the encryption offset and padding.
  *
  * If EO is nonzero, additional blocks are built from payload bytes
  * until EO is exahusted (FIXME: padding to 16 bytes, I guess). The
  * padding is not xmitted.
  */

 /* WUSB1.0[T6.4] */
 struct aes_ccm_b0 {
 	u8 flags;	/* 0x59, per CCM spec */
 	struct aes_ccm_nonce ccm_nonce;
 	__be16 lm;
 } __attribute__((packed));

 /* WUSB1.0[T6.5] */
 struct aes_ccm_b1 {
 	__be16 la;
 	u8 mac_header[10];
 	__le16 eo;
 	u8 security_reserved;	/* This is always zero */
 	u8 padding;		/* 0 */
 } __attribute__((packed));

 /*
  * Encryption Blocks (WUSB1.0[6.4.4])
  *
  * CCM uses Ax blocks to generate a keystream with which the MIC and
  * the message's payload are encoded. A0 always encrypts/decrypts the
  * MIC. Ax (x>0) are used for the sucesive payload blocks.
  *
  * The x is the counter, and is increased for each block.
  */
 struct aes_ccm_a {
 	u8 flags;	/* 0x01, per CCM spec */
 	struct aes_ccm_nonce ccm_nonce;
 	__be16 counter;	/* Value of x */
 } __attribute__((packed));

 static void bytewise_xor(void *_bo, const void *_bi1, const void *_bi2,
 			 size_t size)
 {
 	u8 *bo = _bo;
 	const u8 *bi1 = _bi1, *bi2 = _bi2;
 	size_t itr;
 	for (itr = 0; itr < size; itr++)
 		bo[itr] = bi1[itr] ^ bi2[itr];
 }

 /*
  * CC-MAC function WUSB1.0[6.5]
  *
  * Take a data string and produce the encrypted CBC Counter-mode MIC
  *
  * Note the names for most function arguments are made to (more or
  * less) match those used in the pseudo-function definition given in
  * WUSB1.0[6.5].
  *
  * @tfm_cbc: CBC(AES) blkcipher handle (initialized)
  *
  * @tfm_aes: AES cipher handle (initialized)
  *
  * @mic: buffer for placing the computed MIC (Message Integrity
  *       Code). This is exactly 8 bytes, and we expect the buffer to
  *       be at least eight bytes in length.
  *
  * @key: 128 bit symmetric key
  *
  * @n: CCM nonce
  *
  * @a: ASCII string, 14 bytes long (I guess zero padded if needed;
  *     we use exactly 14 bytes).
  *
  * @b: data stream to be processed; cannot be a global or const local
  *     (will confuse the scatterlists)
  *
  * @blen: size of b...
  *
  * Still not very clear how this is done, but looks like this: we
  * create block B0 (as WUSB1.0[6.5] says), then we AES-crypt it with
  * @key. We bytewise xor B0 with B1 (1) and AES-crypt that. Then we
  * take the payload and divide it in blocks (16 bytes), xor them with
  * the previous crypto result (16 bytes) and crypt it, repeat the next
  * block with the output of the previous one, rinse wash (I guess this
  * is what AES CBC mode means...but I truly have no idea). So we use
  * the CBC(AES) blkcipher, that does precisely that. The IV (Initial
  * Vector) is 16 bytes and is set to zero, so
  *
  * See rfc3610. Linux crypto has a CBC implementation, but the
  * documentation is scarce, to say the least, and the example code is
  * so intricated that is difficult to understand how things work. Most
  * of this is guess work -- bite me.
  *
  * (1) Created as 6.5 says, again, using as l(a) 'Blen + 14', and
  *     using the 14 bytes of @a to fill up
  *     b1.{mac_header,e0,security_reserved,padding}.
  *
  * NOTE: The definiton of l(a) in WUSB1.0[6.5] vs the definition of
  *       l(m) is orthogonal, they bear no relationship, so it is not
  *       in conflict with the parameter's relation that
  *       WUSB1.0[6.4.2]) defines.
  *
  * NOTE: WUSB1.0[A.1]: Host Nonce is missing a nibble? (1e); fixed in
  *       first errata released on 2005/07.
  *
  * NOTE: we need to clean IV to zero at each invocation to make sure
  *       we start with a fresh empty Initial Vector, so that the CBC
  *       works ok.
  *
  * NOTE: blen is not aligned to a block size, we'll pad zeros, that's
  *       what sg[4] is for. Maybe there is a smarter way to do this.
  */
 static int wusb_ccm_mac(struct crypto_blkcipher *tfm_cbc,
 			struct crypto_cipher *tfm_aes, void *mic,
 			const struct aes_ccm_nonce *n,
 			const struct aes_ccm_label *a, const void *b,
 			size_t blen)
 {
 	int result = 0;
 	struct blkcipher_desc desc;
 	struct aes_ccm_b0 b0;
 	struct aes_ccm_b1 b1;
 	struct aes_ccm_a ax;
 	struct scatterlist sg[4], sg_dst;
 	void *iv, *dst_buf;
 	size_t ivsize, dst_size;
 	const u8 bzero[16] = { 0 };
 	size_t zero_padding;

 	/*
 	 * These checks should be compile time optimized out
 	 * ensure @a fills b1's mac_header and following fields
 	 */
 	WARN_ON(sizeof(*a) != sizeof(b1) - sizeof(b1.la));
 	WARN_ON(sizeof(b0) != sizeof(struct aes_ccm_block));
 	WARN_ON(sizeof(b1) != sizeof(struct aes_ccm_block));
 	WARN_ON(sizeof(ax) != sizeof(struct aes_ccm_block));

 	result = -ENOMEM;
 	zero_padding = sizeof(struct aes_ccm_block)
 		- blen % sizeof(struct aes_ccm_block);
 	zero_padding = blen % sizeof(struct aes_ccm_block);
 	if (zero_padding)
 		zero_padding = sizeof(struct aes_ccm_block) - zero_padding;
 	dst_size = blen + sizeof(b0) + sizeof(b1) + zero_padding;
 	dst_buf = kzalloc(dst_size, GFP_KERNEL);
 	if (dst_buf == NULL) {
 		printk(KERN_ERR "E: can't alloc destination buffer\n");
 		goto error_dst_buf;
 	}

 	iv = crypto_blkcipher_crt(tfm_cbc)->iv;
 	ivsize = crypto_blkcipher_ivsize(tfm_cbc);
 	memset(iv, 0, ivsize);

 	/* Setup B0 */
 	b0.flags = 0x59;	/* Format B0 */
 	b0.ccm_nonce = *n;
 	b0.lm = cpu_to_be16(0);	/* WUSB1.0[6.5] sez l(m) is 0 */

 	/* Setup B1
 	 *
 	 * The WUSB spec is anything but clear! WUSB1.0[6.5]
 	 * says that to initialize B1 from A with 'l(a) = blen +
 	 * 14'--after clarification, it means to use A's contents
 	 * for MAC Header, EO, sec reserved and padding.
 	 */
 	b1.la = cpu_to_be16(blen + 14);
 	memcpy(&b1.mac_header, a, sizeof(*a));

 	sg_init_table(sg, ARRAY_SIZE(sg));
 	sg_set_buf(&sg[0], &b0, sizeof(b0));
 	sg_set_buf(&sg[1], &b1, sizeof(b1));
 	sg_set_buf(&sg[2], b, blen);
 	/* 0 if well behaved :) */
 	sg_set_buf(&sg[3], bzero, zero_padding);
 	sg_init_one(&sg_dst, dst_buf, dst_size);

 	desc.tfm = tfm_cbc;
 	desc.flags = 0;
 	result = crypto_blkcipher_encrypt(&desc, &sg_dst, sg, dst_size);
 	if (result < 0) {
 		printk(KERN_ERR "E: can't compute CBC-MAC tag (MIC): %d\n",
 		       result);
 		goto error_cbc_crypt;
 	}

 	/* Now we crypt the MIC Tag (*iv) with Ax -- values per WUSB1.0[6.5]
 	 * The procedure is to AES crypt the A0 block and XOR the MIC
 	 * Tag agains it; we only do the first 8 bytes and place it
 	 * directly in the destination buffer.
 	 *
 	 * POS Crypto API: size is assumed to be AES's block size.
 	 * Thanks for documenting it -- tip taken from airo.c
 	 */
 	ax.flags = 0x01;		/* as per WUSB 1.0 spec */
 	ax.ccm_nonce = *n;
 	ax.counter = 0;
 	crypto_cipher_encrypt_one(tfm_aes, (void *)&ax, (void *)&ax);
 	bytewise_xor(mic, &ax, iv, 8);
 	result = 8;
 error_cbc_crypt:
 	kfree(dst_buf);
 error_dst_buf:
 	return result;
 }

 /*
  * WUSB Pseudo Random Function (WUSB1.0[6.5])
  *
  * @b: buffer to the source data; cannot be a global or const local
  *     (will confuse the scatterlists)
  */
 ssize_t wusb_prf(void *out, size_t out_size,
 		 const u8 key[16], const struct aes_ccm_nonce *_n,
 		 const struct aes_ccm_label *a,
 		 const void *b, size_t blen, size_t len)
 {
 	ssize_t result, bytes = 0, bitr;
 	struct aes_ccm_nonce n = *_n;
 	struct crypto_blkcipher *tfm_cbc;
 	struct crypto_cipher *tfm_aes;
 	u64 sfn = 0;
 	__le64 sfn_le;

 	tfm_cbc = crypto_alloc_blkcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(tfm_cbc)) {
 		result = PTR_ERR(tfm_cbc);
 		printk(KERN_ERR "E: can't load CBC(AES): %d\n", (int)result);
 		goto error_alloc_cbc;
 	}
 	result = crypto_blkcipher_setkey(tfm_cbc, key, 16);
 	if (result < 0) {
 		printk(KERN_ERR "E: can't set CBC key: %d\n", (int)result);
 		goto error_setkey_cbc;
 	}

 	tfm_aes = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(tfm_aes)) {
 		result = PTR_ERR(tfm_aes);
 		printk(KERN_ERR "E: can't load AES: %d\n", (int)result);
 		goto error_alloc_aes;
 	}
 	result = crypto_cipher_setkey(tfm_aes, key, 16);
 	if (result < 0) {
 		printk(KERN_ERR "E: can't set AES key: %d\n", (int)result);
 		goto error_setkey_aes;
 	}

 	for (bitr = 0; bitr < (len + 63) / 64; bitr++) {
 		sfn_le = cpu_to_le64(sfn++);
 		memcpy(&n.sfn, &sfn_le, sizeof(n.sfn));	/* n.sfn++... */
 		result = wusb_ccm_mac(tfm_cbc, tfm_aes, out + bytes,
 				      &n, a, b, blen);
 		if (result < 0)
 			goto error_ccm_mac;
 		bytes += result;
 	}
 	result = bytes;
 error_ccm_mac:
 error_setkey_aes:
 	crypto_free_cipher(tfm_aes);
 error_alloc_aes:
 error_setkey_cbc:
 	crypto_free_blkcipher(tfm_cbc);
 error_alloc_cbc:
 	return result;
 }

 /* WUSB1.0[A.2] test vectors */
 static const u8 stv_hsmic_key[16] = {
 	0x4b, 0x79, 0xa3, 0xcf, 0xe5, 0x53, 0x23, 0x9d,
 	0xd7, 0xc1, 0x6d, 0x1c, 0x2d, 0xab, 0x6d, 0x3f
 };

 static const struct aes_ccm_nonce stv_hsmic_n = {
 	.sfn = { 0 },
 	.tkid = { 0x76, 0x98, 0x01,  },
 	.dest_addr = { .data = { 0xbe, 0x00 } },
 		.src_addr = { .data = { 0x76, 0x98 } },
 };

 /*
  * Out-of-band MIC Generation verification code
  *
  */
 static int wusb_oob_mic_verify(void)
 {
 	int result;
 	u8 mic[8];
 	/* WUSB1.0[A.2] test vectors
 	 *
 	 * Need to keep it in the local stack as GCC 4.1.3something
 	 * messes up and generates noise.
 	 */
 	struct usb_handshake stv_hsmic_hs = {
 		.bMessageNumber = 2,
 		.bStatus 	= 00,
 		.tTKID 		= { 0x76, 0x98, 0x01 },
 		.bReserved 	= 00,
 		.CDID 		= { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35,
 				    0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
 				    0x3c, 0x3d, 0x3e, 0x3f },
 		.nonce	 	= { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25,
 				    0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,
 				    0x2c, 0x2d, 0x2e, 0x2f },
 		.MIC	 	= { 0x75, 0x6a, 0x97, 0x51, 0x0c, 0x8c,
 				    0x14, 0x7b } ,
 	};
 	size_t hs_size;

 	result = wusb_oob_mic(mic, stv_hsmic_key, &stv_hsmic_n, &stv_hsmic_hs);
 	if (result < 0)
 		printk(KERN_ERR "E: WUSB OOB MIC test: failed: %d\n", result);
 	else if (memcmp(stv_hsmic_hs.MIC, mic, sizeof(mic))) {
 		printk(KERN_ERR "E: OOB MIC test: "
 		       "mismatch between MIC result and WUSB1.0[A2]\n");
 		hs_size = sizeof(stv_hsmic_hs) - sizeof(stv_hsmic_hs.MIC);
 		printk(KERN_ERR "E: Handshake2 in: (%zu bytes)\n", hs_size);
 		wusb_key_dump(&stv_hsmic_hs, hs_size);
 		printk(KERN_ERR "E: CCM Nonce in: (%zu bytes)\n",
 		       sizeof(stv_hsmic_n));
 		wusb_key_dump(&stv_hsmic_n, sizeof(stv_hsmic_n));
 		printk(KERN_ERR "E: MIC out:\n");
 		wusb_key_dump(mic, sizeof(mic));
 		printk(KERN_ERR "E: MIC out (from WUSB1.0[A.2]):\n");
 		wusb_key_dump(stv_hsmic_hs.MIC, sizeof(stv_hsmic_hs.MIC));
 		result = -EINVAL;
 	} else
 		result = 0;
 	return result;
 }

 /*
  * Test vectors for Key derivation
  *
  * These come from WUSB1.0[6.5.1], the vectors in WUSB1.0[A.1]
  * (errata corrected in 2005/07).
  */
 static const u8 stv_key_a1[16] __attribute__ ((__aligned__(4))) = {
 	0xf0, 0xe1, 0xd2, 0xc3, 0xb4, 0xa5, 0x96, 0x87,
 	0x78, 0x69, 0x5a, 0x4b, 0x3c, 0x2d, 0x1e, 0x0f
 };

 static const struct aes_ccm_nonce stv_keydvt_n_a1 = {
 	.sfn = { 0 },
 	.tkid = { 0x76, 0x98, 0x01,  },
 	.dest_addr = { .data = { 0xbe, 0x00 } },
 	.src_addr = { .data = { 0x76, 0x98 } },
 };

 static const struct wusb_keydvt_out stv_keydvt_out_a1 = {
 	.kck = {
 		0x4b, 0x79, 0xa3, 0xcf, 0xe5, 0x53, 0x23, 0x9d,
 		0xd7, 0xc1, 0x6d, 0x1c, 0x2d, 0xab, 0x6d, 0x3f
 	},
 	.ptk = {
 		0xc8, 0x70, 0x62, 0x82, 0xb6, 0x7c, 0xe9, 0x06,
 		0x7b, 0xc5, 0x25, 0x69, 0xf2, 0x36, 0x61, 0x2d
 	}
 };

 /*
  * Performa a test to make sure we match the vectors defined in
  * WUSB1.0[A.1](Errata2006/12)
  */
 static int wusb_key_derive_verify(void)
 {
 	int result = 0;
 	struct wusb_keydvt_out keydvt_out;
 	/* These come from WUSB1.0[A.1] + 2006/12 errata
 	 * NOTE: can't make this const or global -- somehow it seems
 	 *       the scatterlists for crypto get confused and we get
 	 *       bad data. There is no doc on this... */
 	struct wusb_keydvt_in stv_keydvt_in_a1 = {
 		.hnonce = {
 			0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
 			0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
 		},
 		.dnonce = {
 			0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
 			0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f
 		}
 	};

 	result = wusb_key_derive(&keydvt_out, stv_key_a1, &stv_keydvt_n_a1,
 				 &stv_keydvt_in_a1);
 	if (result < 0)
 		printk(KERN_ERR "E: WUSB key derivation test: "
 		       "derivation failed: %d\n", result);
 	if (memcmp(&stv_keydvt_out_a1, &keydvt_out, sizeof(keydvt_out))) {
 		printk(KERN_ERR "E: WUSB key derivation test: "
 		       "mismatch between key derivation result "
 		       "and WUSB1.0[A1] Errata 2006/12\n");
 		printk(KERN_ERR "E: keydvt in: key\n");
 		wusb_key_dump(stv_key_a1, sizeof(stv_key_a1));
 		printk(KERN_ERR "E: keydvt in: nonce\n");
 		wusb_key_dump( &stv_keydvt_n_a1, sizeof(stv_keydvt_n_a1));
 		printk(KERN_ERR "E: keydvt in: hnonce & dnonce\n");
 		wusb_key_dump(&stv_keydvt_in_a1, sizeof(stv_keydvt_in_a1));
 		printk(KERN_ERR "E: keydvt out: KCK\n");
 		wusb_key_dump(&keydvt_out.kck, sizeof(keydvt_out.kck));
 		printk(KERN_ERR "E: keydvt out: PTK\n");
 		wusb_key_dump(&keydvt_out.ptk, sizeof(keydvt_out.ptk));
 		result = -EINVAL;
 	} else
 		result = 0;
 	return result;
 }

 /*
  * Initialize crypto system
  *
  * FIXME: we do nothing now, other than verifying. Later on we'll
  * cache the encryption stuff, so that's why we have a separate init.
  */
 int wusb_crypto_init(void)
 {
 	int result;

 	if (debug_crypto_verify) {
 		result = wusb_key_derive_verify();
 		if (result < 0)
 			return result;
 		return wusb_oob_mic_verify();
 	}
 	return 0;
 }

 void wusb_crypto_exit(void)
 {
 	/* FIXME: free cached crypto transforms */
 }
	/*
	* Ultra Wide Band
	* AES-128 CCM Encryption
	*
	* Copyright (C) 2007 Intel Corporation
	* Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License version
	* 2 as published by the Free Software Foundation.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
	* 02110-1301, USA.
	*
	*
	* We don't do any encryption here; we use the Linux Kernel's AES-128
	* crypto modules to construct keys and payload blocks in a way
	* defined by WUSB1.0[6]. Check the erratas, as typos are are patched
	* there.
	*
	* Thanks a zillion to John Keys for his help and clarifications over
	* the designed-by-a-committee text.
	*
	* So the idea is that there is this basic Pseudo-Random-Function
	* defined in WUSB1.0[6.5] which is the core of everything. It works
	* by tweaking some blocks, AES crypting them and then xoring
	* something else with them (this seems to be called CBC(AES) -- can
	* you tell I know jack about crypto?). So we just funnel it into the
	* Linux Crypto API.
	*
	* We leave a crypto test module so we can verify that vectors match,
	* every now and then.
	*
	* Block size: 16 bytes -- AES seems to do things in 'block sizes'. I
	* am learning a lot...
	*
	* Conveniently, some data structures that need to be
	* funneled through AES are...16 bytes in size!
	*/

	#include <linux/crypto.h>
	#include <linux/module.h>
	#include <linux/err.h>
	#include <linux/uwb.h>
	#include <linux/usb/wusb.h>
	#include <linux/scatterlist.h>

	static int debug_crypto_verify = 0;

	module_param(debug_crypto_verify, int, 0);
	MODULE_PARM_DESC(debug_crypto_verify, "verify the key generation algorithms");

	static void wusb_key_dump(const void *buf, size_t len)
	{
	print_hex_dump(KERN_ERR, " ", DUMP_PREFIX_OFFSET, 16, 1,
	buf, len, 0);
	}

	/*
	* Block of data, as understood by AES-CCM
	*
	* The code assumes this structure is nothing but a 16 byte array
	* (packed in a struct to avoid common mess ups that I usually do with
	* arrays and enforcing type checking).
	*/
	struct aes_ccm_block {
	u8 data[16];
	} __attribute__((packed));

	/*
	* Counter-mode Blocks (WUSB1.0[6.4])
	*
	* According to CCM (or so it seems), for the purpose of calculating
	* the MIC, the message is broken in N counter-mode blocks, B0, B1,
	* ... BN.
	*
	* B0 contains flags, the CCM nonce and l(m).
	*
	* B1 contains l(a), the MAC header, the encryption offset and padding.
	*
	* If EO is nonzero, additional blocks are built from payload bytes
	* until EO is exahusted (FIXME: padding to 16 bytes, I guess). The
	* padding is not xmitted.
	*/

	/* WUSB1.0[T6.4] */
	struct aes_ccm_b0 {
	u8 flags; /* 0x59, per CCM spec */
	struct aes_ccm_nonce ccm_nonce;
	__be16 lm;
	} __attribute__((packed));

	/* WUSB1.0[T6.5] */
	struct aes_ccm_b1 {
	__be16 la;
	u8 mac_header[10];
	__le16 eo;
	u8 security_reserved; /* This is always zero */
	u8 padding; /* 0 */
	} __attribute__((packed));

	/*
	* Encryption Blocks (WUSB1.0[6.4.4])
	*
	* CCM uses Ax blocks to generate a keystream with which the MIC and
	* the message's payload are encoded. A0 always encrypts/decrypts the
	* MIC. Ax (x>0) are used for the sucesive payload blocks.
	*
	* The x is the counter, and is increased for each block.
	*/
	struct aes_ccm_a {
	u8 flags; /* 0x01, per CCM spec */
	struct aes_ccm_nonce ccm_nonce;
	__be16 counter; /* Value of x */
	} __attribute__((packed));

	static void bytewise_xor(void _bo, const void _bi1, const void *_bi2,
	size_t size)
	{
	u8 *bo = _bo;
	const u8 bi1 = _bi1, bi2 = _bi2;
	size_t itr;
	for (itr = 0; itr < size; itr++)
	bo[itr] = bi1[itr] ^ bi2[itr];
	}

	/*
	* CC-MAC function WUSB1.0[6.5]
	*
	* Take a data string and produce the encrypted CBC Counter-mode MIC
	*
	* Note the names for most function arguments are made to (more or
	* less) match those used in the pseudo-function definition given in
	* WUSB1.0[6.5].
	*
	* @tfm_cbc: CBC(AES) blkcipher handle (initialized)
	*
	* @tfm_aes: AES cipher handle (initialized)
	*
	* @mic: buffer for placing the computed MIC (Message Integrity
	* Code). This is exactly 8 bytes, and we expect the buffer to
	* be at least eight bytes in length.
	*
	* @key: 128 bit symmetric key
	*
	* @n: CCM nonce
	*
	* @a: ASCII string, 14 bytes long (I guess zero padded if needed;
	* we use exactly 14 bytes).
	*
	* @b: data stream to be processed; cannot be a global or const local
	* (will confuse the scatterlists)
	*
	* @blen: size of b...
	*
	* Still not very clear how this is done, but looks like this: we
	* create block B0 (as WUSB1.0[6.5] says), then we AES-crypt it with
	* @key. We bytewise xor B0 with B1 (1) and AES-crypt that. Then we
	* take the payload and divide it in blocks (16 bytes), xor them with
	* the previous crypto result (16 bytes) and crypt it, repeat the next
	* block with the output of the previous one, rinse wash (I guess this
	* is what AES CBC mode means...but I truly have no idea). So we use
	* the CBC(AES) blkcipher, that does precisely that. The IV (Initial
	* Vector) is 16 bytes and is set to zero, so
	*
	* See rfc3610. Linux crypto has a CBC implementation, but the
	* documentation is scarce, to say the least, and the example code is
	* so intricated that is difficult to understand how things work. Most
	* of this is guess work -- bite me.
	*
	* (1) Created as 6.5 says, again, using as l(a) 'Blen + 14', and
	* using the 14 bytes of @a to fill up
	* b1.{mac_header,e0,security_reserved,padding}.
	*
	* NOTE: The definiton of l(a) in WUSB1.0[6.5] vs the definition of
	* l(m) is orthogonal, they bear no relationship, so it is not
	* in conflict with the parameter's relation that
	* WUSB1.0[6.4.2]) defines.
	*
	* NOTE: WUSB1.0[A.1]: Host Nonce is missing a nibble? (1e); fixed in
	* first errata released on 2005/07.
	*
	* NOTE: we need to clean IV to zero at each invocation to make sure
	* we start with a fresh empty Initial Vector, so that the CBC
	* works ok.
	*
	* NOTE: blen is not aligned to a block size, we'll pad zeros, that's
	* what sg[4] is for. Maybe there is a smarter way to do this.
	*/
	static int wusb_ccm_mac(struct crypto_blkcipher *tfm_cbc,
	struct crypto_cipher tfm_aes, void mic,
	const struct aes_ccm_nonce *n,
	const struct aes_ccm_label a, const void b,
	size_t blen)
	{
	int result = 0;
	struct blkcipher_desc desc;
	struct aes_ccm_b0 b0;
	struct aes_ccm_b1 b1;
	struct aes_ccm_a ax;
	struct scatterlist sg[4], sg_dst;
	void iv, dst_buf;
	size_t ivsize, dst_size;
	const u8 bzero[16] = { 0 };
	size_t zero_padding;

	/*
	* These checks should be compile time optimized out
	* ensure @a fills b1's mac_header and following fields
	*/
	WARN_ON(sizeof(*a) != sizeof(b1) - sizeof(b1.la));
	WARN_ON(sizeof(b0) != sizeof(struct aes_ccm_block));
	WARN_ON(sizeof(b1) != sizeof(struct aes_ccm_block));
	WARN_ON(sizeof(ax) != sizeof(struct aes_ccm_block));

	result = -ENOMEM;
	zero_padding = sizeof(struct aes_ccm_block)
	- blen % sizeof(struct aes_ccm_block);
	zero_padding = blen % sizeof(struct aes_ccm_block);
	if (zero_padding)
	zero_padding = sizeof(struct aes_ccm_block) - zero_padding;
	dst_size = blen + sizeof(b0) + sizeof(b1) + zero_padding;
	dst_buf = kzalloc(dst_size, GFP_KERNEL);
	if (dst_buf == NULL) {
	printk(KERN_ERR "E: can't alloc destination buffer\n");
	goto error_dst_buf;
	}

	iv = crypto_blkcipher_crt(tfm_cbc)->iv;
	ivsize = crypto_blkcipher_ivsize(tfm_cbc);
	memset(iv, 0, ivsize);

	/* Setup B0 */
	b0.flags = 0x59; /* Format B0 */
	b0.ccm_nonce = *n;
	b0.lm = cpu_to_be16(0); /* WUSB1.0[6.5] sez l(m) is 0 */

	/* Setup B1
	*
	* The WUSB spec is anything but clear! WUSB1.0[6.5]
	* says that to initialize B1 from A with 'l(a) = blen +
	* 14'--after clarification, it means to use A's contents
	* for MAC Header, EO, sec reserved and padding.
	*/
	b1.la = cpu_to_be16(blen + 14);
	memcpy(&b1.mac_header, a, sizeof(*a));

	sg_init_table(sg, ARRAY_SIZE(sg));
	sg_set_buf(&sg[0], &b0, sizeof(b0));
	sg_set_buf(&sg[1], &b1, sizeof(b1));
	sg_set_buf(&sg[2], b, blen);
	/* 0 if well behaved :) */
	sg_set_buf(&sg[3], bzero, zero_padding);
	sg_init_one(&sg_dst, dst_buf, dst_size);

	desc.tfm = tfm_cbc;
	desc.flags = 0;
	result = crypto_blkcipher_encrypt(&desc, &sg_dst, sg, dst_size);
	if (result < 0) {
	printk(KERN_ERR "E: can't compute CBC-MAC tag (MIC): %d\n",
	result);
	goto error_cbc_crypt;
	}

	/* Now we crypt the MIC Tag (*iv) with Ax -- values per WUSB1.0[6.5]
	* The procedure is to AES crypt the A0 block and XOR the MIC
	* Tag agains it; we only do the first 8 bytes and place it
	* directly in the destination buffer.
	*
	* POS Crypto API: size is assumed to be AES's block size.
	* Thanks for documenting it -- tip taken from airo.c
	*/
	ax.flags = 0x01; /* as per WUSB 1.0 spec */
	ax.ccm_nonce = *n;
	ax.counter = 0;
	crypto_cipher_encrypt_one(tfm_aes, (void )&ax, (void )&ax);
	bytewise_xor(mic, &ax, iv, 8);
	result = 8;
	error_cbc_crypt:
	kfree(dst_buf);
	error_dst_buf:
	return result;
	}

	/*
	* WUSB Pseudo Random Function (WUSB1.0[6.5])
	*
	* @b: buffer to the source data; cannot be a global or const local
	* (will confuse the scatterlists)
	*/
	ssize_t wusb_prf(void *out, size_t out_size,
	const u8 key[16], const struct aes_ccm_nonce *_n,
	const struct aes_ccm_label *a,
	const void *b, size_t blen, size_t len)
	{
	ssize_t result, bytes = 0, bitr;
	struct aes_ccm_nonce n = *_n;
	struct crypto_blkcipher *tfm_cbc;
	struct crypto_cipher *tfm_aes;
	u64 sfn = 0;
	__le64 sfn_le;

	tfm_cbc = crypto_alloc_blkcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(tfm_cbc)) {
	result = PTR_ERR(tfm_cbc);
	printk(KERN_ERR "E: can't load CBC(AES): %d\n", (int)result);
	goto error_alloc_cbc;
	}
	result = crypto_blkcipher_setkey(tfm_cbc, key, 16);
	if (result < 0) {
	printk(KERN_ERR "E: can't set CBC key: %d\n", (int)result);
	goto error_setkey_cbc;
	}

	tfm_aes = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(tfm_aes)) {
	result = PTR_ERR(tfm_aes);
	printk(KERN_ERR "E: can't load AES: %d\n", (int)result);
	goto error_alloc_aes;
	}
	result = crypto_cipher_setkey(tfm_aes, key, 16);
	if (result < 0) {
	printk(KERN_ERR "E: can't set AES key: %d\n", (int)result);
	goto error_setkey_aes;
	}

	for (bitr = 0; bitr < (len + 63) / 64; bitr++) {
	sfn_le = cpu_to_le64(sfn++);
	memcpy(&n.sfn, &sfn_le, sizeof(n.sfn)); /* n.sfn++... */
	result = wusb_ccm_mac(tfm_cbc, tfm_aes, out + bytes,
	&n, a, b, blen);
	if (result < 0)
	goto error_ccm_mac;
	bytes += result;
	}
	result = bytes;
	error_ccm_mac:
	error_setkey_aes:
	crypto_free_cipher(tfm_aes);
	error_alloc_aes:
	error_setkey_cbc:
	crypto_free_blkcipher(tfm_cbc);
	error_alloc_cbc:
	return result;
	}

	/* WUSB1.0[A.2] test vectors */
	static const u8 stv_hsmic_key[16] = {
	0x4b, 0x79, 0xa3, 0xcf, 0xe5, 0x53, 0x23, 0x9d,
	0xd7, 0xc1, 0x6d, 0x1c, 0x2d, 0xab, 0x6d, 0x3f
	};

	static const struct aes_ccm_nonce stv_hsmic_n = {
	.sfn = { 0 },
	.tkid = { 0x76, 0x98, 0x01, },
	.dest_addr = { .data = { 0xbe, 0x00 } },
	.src_addr = { .data = { 0x76, 0x98 } },
	};

	/*
	* Out-of-band MIC Generation verification code
	*
	*/
	static int wusb_oob_mic_verify(void)
	{
	int result;
	u8 mic[8];
	/* WUSB1.0[A.2] test vectors
	*
	* Need to keep it in the local stack as GCC 4.1.3something
	* messes up and generates noise.
	*/
	struct usb_handshake stv_hsmic_hs = {
	.bMessageNumber = 2,
	.bStatus = 00,
	.tTKID = { 0x76, 0x98, 0x01 },
	.bReserved = 00,
	.CDID = { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35,
	0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
	0x3c, 0x3d, 0x3e, 0x3f },
	.nonce = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25,
	0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,
	0x2c, 0x2d, 0x2e, 0x2f },
	.MIC = { 0x75, 0x6a, 0x97, 0x51, 0x0c, 0x8c,
	0x14, 0x7b } ,
	};
	size_t hs_size;

	result = wusb_oob_mic(mic, stv_hsmic_key, &stv_hsmic_n, &stv_hsmic_hs);
	if (result < 0)
	printk(KERN_ERR "E: WUSB OOB MIC test: failed: %d\n", result);
	else if (memcmp(stv_hsmic_hs.MIC, mic, sizeof(mic))) {
	printk(KERN_ERR "E: OOB MIC test: "
	"mismatch between MIC result and WUSB1.0[A2]\n");
	hs_size = sizeof(stv_hsmic_hs) - sizeof(stv_hsmic_hs.MIC);
	printk(KERN_ERR "E: Handshake2 in: (%zu bytes)\n", hs_size);
	wusb_key_dump(&stv_hsmic_hs, hs_size);
	printk(KERN_ERR "E: CCM Nonce in: (%zu bytes)\n",
	sizeof(stv_hsmic_n));
	wusb_key_dump(&stv_hsmic_n, sizeof(stv_hsmic_n));
	printk(KERN_ERR "E: MIC out:\n");
	wusb_key_dump(mic, sizeof(mic));
	printk(KERN_ERR "E: MIC out (from WUSB1.0[A.2]):\n");
	wusb_key_dump(stv_hsmic_hs.MIC, sizeof(stv_hsmic_hs.MIC));
	result = -EINVAL;
	} else
	result = 0;
	return result;
	}

	/*
	* Test vectors for Key derivation
	*
	* These come from WUSB1.0[6.5.1], the vectors in WUSB1.0[A.1]
	* (errata corrected in 2005/07).
	*/
	static const u8 stv_key_a1[16] __attribute__ ((__aligned__(4))) = {
	0xf0, 0xe1, 0xd2, 0xc3, 0xb4, 0xa5, 0x96, 0x87,
	0x78, 0x69, 0x5a, 0x4b, 0x3c, 0x2d, 0x1e, 0x0f
	};

	static const struct aes_ccm_nonce stv_keydvt_n_a1 = {
	.sfn = { 0 },
	.tkid = { 0x76, 0x98, 0x01, },
	.dest_addr = { .data = { 0xbe, 0x00 } },
	.src_addr = { .data = { 0x76, 0x98 } },
	};

	static const struct wusb_keydvt_out stv_keydvt_out_a1 = {
	.kck = {
	0x4b, 0x79, 0xa3, 0xcf, 0xe5, 0x53, 0x23, 0x9d,
	0xd7, 0xc1, 0x6d, 0x1c, 0x2d, 0xab, 0x6d, 0x3f
	},
	.ptk = {
	0xc8, 0x70, 0x62, 0x82, 0xb6, 0x7c, 0xe9, 0x06,
	0x7b, 0xc5, 0x25, 0x69, 0xf2, 0x36, 0x61, 0x2d
	}
	};

	/*
	* Performa a test to make sure we match the vectors defined in
	* WUSB1.0[A.1](Errata2006/12)
	*/
	static int wusb_key_derive_verify(void)
	{
	int result = 0;
	struct wusb_keydvt_out keydvt_out;
	/* These come from WUSB1.0[A.1] + 2006/12 errata
	* NOTE: can't make this const or global -- somehow it seems
	* the scatterlists for crypto get confused and we get
	* bad data. There is no doc on this... */
	struct wusb_keydvt_in stv_keydvt_in_a1 = {
	.hnonce = {
	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
	},
	.dnonce = {
	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f
	}
	};

	result = wusb_key_derive(&keydvt_out, stv_key_a1, &stv_keydvt_n_a1,
	&stv_keydvt_in_a1);
	if (result < 0)
	printk(KERN_ERR "E: WUSB key derivation test: "
	"derivation failed: %d\n", result);
	if (memcmp(&stv_keydvt_out_a1, &keydvt_out, sizeof(keydvt_out))) {
	printk(KERN_ERR "E: WUSB key derivation test: "
	"mismatch between key derivation result "
	"and WUSB1.0[A1] Errata 2006/12\n");
	printk(KERN_ERR "E: keydvt in: key\n");
	wusb_key_dump(stv_key_a1, sizeof(stv_key_a1));
	printk(KERN_ERR "E: keydvt in: nonce\n");
	wusb_key_dump( &stv_keydvt_n_a1, sizeof(stv_keydvt_n_a1));
	printk(KERN_ERR "E: keydvt in: hnonce & dnonce\n");
	wusb_key_dump(&stv_keydvt_in_a1, sizeof(stv_keydvt_in_a1));
	printk(KERN_ERR "E: keydvt out: KCK\n");
	wusb_key_dump(&keydvt_out.kck, sizeof(keydvt_out.kck));
	printk(KERN_ERR "E: keydvt out: PTK\n");
	wusb_key_dump(&keydvt_out.ptk, sizeof(keydvt_out.ptk));
	result = -EINVAL;
	} else
	result = 0;
	return result;
	}

	/*
	* Initialize crypto system
	*
	* FIXME: we do nothing now, other than verifying. Later on we'll
	* cache the encryption stuff, so that's why we have a separate init.
	*/
	int wusb_crypto_init(void)
	{
	int result;

	if (debug_crypto_verify) {
	result = wusb_key_derive_verify();
	if (result < 0)
	return result;
	return wusb_oob_mic_verify();
	}
	return 0;
	}

	void wusb_crypto_exit(void)
	{
	/* FIXME: free cached crypto transforms */
	}