/*
   * 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/slab.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 exhausted (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 successive 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 definition 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 = 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
  ");
  		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
  ",
  		       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 against 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
  ", (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
  ", (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
  ", (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
  ", (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
  ", 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]
  ");
  		hs_size = sizeof(stv_hsmic_hs) - sizeof(stv_hsmic_hs.MIC);
  		printk(KERN_ERR "E: Handshake2 in: (%zu bytes)
  ", hs_size);
  		wusb_key_dump(&stv_hsmic_hs, hs_size);
  		printk(KERN_ERR "E: CCM Nonce in: (%zu bytes)
  ",
  		       sizeof(stv_hsmic_n));
  		wusb_key_dump(&stv_hsmic_n, sizeof(stv_hsmic_n));
  		printk(KERN_ERR "E: MIC out:
  ");
  		wusb_key_dump(mic, sizeof(mic));
  		printk(KERN_ERR "E: MIC out (from WUSB1.0[A.2]):
  ");
  		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
  ", 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
  ");
  		printk(KERN_ERR "E: keydvt in: key
  ");
  		wusb_key_dump(stv_key_a1, sizeof(stv_key_a1));
  		printk(KERN_ERR "E: keydvt in: nonce
  ");
  		wusb_key_dump( &stv_keydvt_n_a1, sizeof(stv_keydvt_n_a1));
  		printk(KERN_ERR "E: keydvt in: hnonce & dnonce
  ");
  		wusb_key_dump(&stv_keydvt_in_a1, sizeof(stv_keydvt_in_a1));
  		printk(KERN_ERR "E: keydvt out: KCK
  ");
  		wusb_key_dump(&keydvt_out.kck, sizeof(keydvt_out.kck));
  		printk(KERN_ERR "E: keydvt out: PTK
  ");
  		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 */
  }