drivers/usb/wusbcore/crypto.c

   1 /*
   2  * Ultra Wide Band
   3  * AES-128 CCM Encryption
   4  *
   5  * Copyright (C) 2007 Intel Corporation
   6  * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version
  10  * 2 as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20  * 02110-1301, USA.
  21  *
  22  *
  23  * We don't do any encryption here; we use the Linux Kernel's AES-128
  24  * crypto modules to construct keys and payload blocks in a way
  25  * defined by WUSB1.0[6]. Check the erratas, as typos are are patched
  26  * there.
  27  *
  28  * Thanks a zillion to John Keys for his help and clarifications over
  29  * the designed-by-a-committee text.
  30  *
  31  * So the idea is that there is this basic Pseudo-Random-Function
  32  * defined in WUSB1.0[6.5] which is the core of everything. It works
  33  * by tweaking some blocks, AES crypting them and then xoring
  34  * something else with them (this seems to be called CBC(AES) -- can
  35  * you tell I know jack about crypto?). So we just funnel it into the
  36  * Linux Crypto API.
  37  *
  38  * We leave a crypto test module so we can verify that vectors match,
  39  * every now and then.
  40  *
  41  * Block size: 16 bytes -- AES seems to do things in 'block sizes'. I
  42  *             am learning a lot...
  43  *
  44  *             Conveniently, some data structures that need to be
  45  *             funneled through AES are...16 bytes in size!
  46  */
  47
  48 #include <linux/crypto.h>
  49 #include <linux/module.h>
  50 #include <linux/err.h>
  51 #include <linux/uwb.h>
  52 #include <linux/usb/wusb.h>
  53 #include <linux/scatterlist.h>
  54
  55 static int debug_crypto_verify = 0;
  56
  57 module_param(debug_crypto_verify, int, 0);
  58 MODULE_PARM_DESC(debug_crypto_verify, "verify the key generation algorithms");
  59
  60 static void wusb_key_dump(const void *buf, size_t len)
  61 {
  62         print_hex_dump(KERN_ERR, "  ", DUMP_PREFIX_OFFSET, 16, 1,
  63                        buf, len, 0);
  64 }
  65
  66 /*
  67  * Block of data, as understood by AES-CCM
  68  *
  69  * The code assumes this structure is nothing but a 16 byte array
  70  * (packed in a struct to avoid common mess ups that I usually do with
  71  * arrays and enforcing type checking).
  72  */
  73 struct aes_ccm_block {
  74         u8 data[16];
  75 } __attribute__((packed));
  76
  77 /*
  78  * Counter-mode Blocks (WUSB1.0[6.4])
  79  *
  80  * According to CCM (or so it seems), for the purpose of calculating
  81  * the MIC, the message is broken in N counter-mode blocks, B0, B1,
  82  * ... BN.
  83  *
  84  * B0 contains flags, the CCM nonce and l(m).
  85  *
  86  * B1 contains l(a), the MAC header, the encryption offset and padding.
  87  *
  88  * If EO is nonzero, additional blocks are built from payload bytes
  89  * until EO is exahusted (FIXME: padding to 16 bytes, I guess). The
  90  * padding is not xmitted.
  91  */
  92
  93 /* WUSB1.0[T6.4] */
  94 struct aes_ccm_b0 {
  95         u8 flags;       /* 0x59, per CCM spec */
  96         struct aes_ccm_nonce ccm_nonce;
  97         __be16 lm;
  98 } __attribute__((packed));
  99
 100 /* WUSB1.0[T6.5] */
 101 struct aes_ccm_b1 {
 102         __be16 la;
 103         u8 mac_header[10];
 104         __le16 eo;
 105         u8 security_reserved;   /* This is always zero */
 106         u8 padding;             /* 0 */
 107 } __attribute__((packed));
 108
 109 /*
 110  * Encryption Blocks (WUSB1.0[6.4.4])
 111  *
 112  * CCM uses Ax blocks to generate a keystream with which the MIC and
 113  * the message's payload are encoded. A0 always encrypts/decrypts the
 114  * MIC. Ax (x>0) are used for the sucesive payload blocks.
 115  *
 116  * The x is the counter, and is increased for each block.
 117  */
 118 struct aes_ccm_a {
 119         u8 flags;       /* 0x01, per CCM spec */
 120         struct aes_ccm_nonce ccm_nonce;
 121         __be16 counter; /* Value of x */
 122 } __attribute__((packed));
 123
 124 static void bytewise_xor(void *_bo, const void *_bi1, const void *_bi2,
 125                          size_t size)
 126 {
 127         u8 *bo = _bo;
 128         const u8 *bi1 = _bi1, *bi2 = _bi2;
 129         size_t itr;
 130         for (itr = 0; itr < size; itr++)
 131                 bo[itr] = bi1[itr] ^ bi2[itr];
 132 }
 133
 134 /*
 135  * CC-MAC function WUSB1.0[6.5]
 136  *
 137  * Take a data string and produce the encrypted CBC Counter-mode MIC
 138  *
 139  * Note the names for most function arguments are made to (more or
 140  * less) match those used in the pseudo-function definition given in
 141  * WUSB1.0[6.5].
 142  *
 143  * @tfm_cbc: CBC(AES) blkcipher handle (initialized)
 144  *
 145  * @tfm_aes: AES cipher handle (initialized)
 146  *
 147  * @mic: buffer for placing the computed MIC (Message Integrity
 148  *       Code). This is exactly 8 bytes, and we expect the buffer to
 149  *       be at least eight bytes in length.
 150  *
 151  * @key: 128 bit symmetric key
 152  *
 153  * @n: CCM nonce
 154  *
 155  * @a: ASCII string, 14 bytes long (I guess zero padded if needed;
 156  *     we use exactly 14 bytes).
 157  *
 158  * @b: data stream to be processed; cannot be a global or const local
 159  *     (will confuse the scatterlists)
 160  *
 161  * @blen: size of b...
 162  *
 163  * Still not very clear how this is done, but looks like this: we
 164  * create block B0 (as WUSB1.0[6.5] says), then we AES-crypt it with
 165  * @key. We bytewise xor B0 with B1 (1) and AES-crypt that. Then we
 166  * take the payload and divide it in blocks (16 bytes), xor them with
 167  * the previous crypto result (16 bytes) and crypt it, repeat the next
 168  * block with the output of the previous one, rinse wash (I guess this
 169  * is what AES CBC mode means...but I truly have no idea). So we use
 170  * the CBC(AES) blkcipher, that does precisely that. The IV (Initial
 171  * Vector) is 16 bytes and is set to zero, so
 172  *
 173  * See rfc3610. Linux crypto has a CBC implementation, but the
 174  * documentation is scarce, to say the least, and the example code is
 175  * so intricated that is difficult to understand how things work. Most
 176  * of this is guess work -- bite me.
 177  *
 178  * (1) Created as 6.5 says, again, using as l(a) 'Blen + 14', and
 179  *     using the 14 bytes of @a to fill up
 180  *     b1.{mac_header,e0,security_reserved,padding}.
 181  *
 182  * NOTE: The definiton of l(a) in WUSB1.0[6.5] vs the definition of
 183  *       l(m) is orthogonal, they bear no relationship, so it is not
 184  *       in conflict with the parameter's relation that
 185  *       WUSB1.0[6.4.2]) defines.
 186  *
 187  * NOTE: WUSB1.0[A.1]: Host Nonce is missing a nibble? (1e); fixed in
 188  *       first errata released on 2005/07.
 189  *
 190  * NOTE: we need to clean IV to zero at each invocation to make sure
 191  *       we start with a fresh empty Initial Vector, so that the CBC
 192  *       works ok.
 193  *
 194  * NOTE: blen is not aligned to a block size, we'll pad zeros, that's
 195  *       what sg[4] is for. Maybe there is a smarter way to do this.
 196  */
 197 static int wusb_ccm_mac(struct crypto_blkcipher *tfm_cbc,
 198                         struct crypto_cipher *tfm_aes, void *mic,
 199                         const struct aes_ccm_nonce *n,
 200                         const struct aes_ccm_label *a, const void *b,
 201                         size_t blen)
 202 {
 203         int result = 0;
 204         struct blkcipher_desc desc;
 205         struct aes_ccm_b0 b0;
 206         struct aes_ccm_b1 b1;
 207         struct aes_ccm_a ax;
 208         struct scatterlist sg[4], sg_dst;
 209         void *iv, *dst_buf;
 210         size_t ivsize, dst_size;
 211         const u8 bzero[16] = { 0 };
 212         size_t zero_padding;
 213
 214         /*
 215          * These checks should be compile time optimized out
 216          * ensure @a fills b1's mac_header and following fields
 217          */
 218         WARN_ON(sizeof(*a) != sizeof(b1) - sizeof(b1.la));
 219         WARN_ON(sizeof(b0) != sizeof(struct aes_ccm_block));
 220         WARN_ON(sizeof(b1) != sizeof(struct aes_ccm_block));
 221         WARN_ON(sizeof(ax) != sizeof(struct aes_ccm_block));
 222
 223         result = -ENOMEM;
 224         zero_padding = sizeof(struct aes_ccm_block)
 225                 - blen % sizeof(struct aes_ccm_block);
 226         zero_padding = blen % sizeof(struct aes_ccm_block);
 227         if (zero_padding)
 228                 zero_padding = sizeof(struct aes_ccm_block) - zero_padding;
 229         dst_size = blen + sizeof(b0) + sizeof(b1) + zero_padding;
 230         dst_buf = kzalloc(dst_size, GFP_KERNEL);
 231         if (dst_buf == NULL) {
 232                 printk(KERN_ERR "E: can't alloc destination buffer\n");
 233                 goto error_dst_buf;
 234         }
 235
 236         iv = crypto_blkcipher_crt(tfm_cbc)->iv;
 237         ivsize = crypto_blkcipher_ivsize(tfm_cbc);
 238         memset(iv, 0, ivsize);
 239
 240         /* Setup B0 */
 241         b0.flags = 0x59;        /* Format B0 */
 242         b0.ccm_nonce = *n;
 243         b0.lm = cpu_to_be16(0); /* WUSB1.0[6.5] sez l(m) is 0 */
 244
 245         /* Setup B1
 246          *
 247          * The WUSB spec is anything but clear! WUSB1.0[6.5]
 248          * says that to initialize B1 from A with 'l(a) = blen +
 249          * 14'--after clarification, it means to use A's contents
 250          * for MAC Header, EO, sec reserved and padding.
 251          */
 252         b1.la = cpu_to_be16(blen + 14);
 253         memcpy(&b1.mac_header, a, sizeof(*a));
 254
 255         sg_init_table(sg, ARRAY_SIZE(sg));
 256         sg_set_buf(&sg[0], &b0, sizeof(b0));
 257         sg_set_buf(&sg[1], &b1, sizeof(b1));
 258         sg_set_buf(&sg[2], b, blen);
 259         /* 0 if well behaved :) */
 260         sg_set_buf(&sg[3], bzero, zero_padding);
 261         sg_init_one(&sg_dst, dst_buf, dst_size);
 262
 263         desc.tfm = tfm_cbc;
 264         desc.flags = 0;
 265         result = crypto_blkcipher_encrypt(&desc, &sg_dst, sg, dst_size);
 266         if (result < 0) {
 267                 printk(KERN_ERR "E: can't compute CBC-MAC tag (MIC): %d\n",
 268                        result);
 269                 goto error_cbc_crypt;
 270         }
 271
 272         /* Now we crypt the MIC Tag (*iv) with Ax -- values per WUSB1.0[6.5]
 273          * The procedure is to AES crypt the A0 block and XOR the MIC
 274          * Tag agains it; we only do the first 8 bytes and place it
 275          * directly in the destination buffer.
 276          *
 277          * POS Crypto API: size is assumed to be AES's block size.
 278          * Thanks for documenting it -- tip taken from airo.c
 279          */
 280         ax.flags = 0x01;                /* as per WUSB 1.0 spec */
 281         ax.ccm_nonce = *n;
 282         ax.counter = 0;
 283         crypto_cipher_encrypt_one(tfm_aes, (void *)&ax, (void *)&ax);
 284         bytewise_xor(mic, &ax, iv, 8);
 285         result = 8;
 286 error_cbc_crypt:
 287         kfree(dst_buf);
 288 error_dst_buf:
 289         return result;
 290 }
 291
 292 /*
 293  * WUSB Pseudo Random Function (WUSB1.0[6.5])
 294  *
 295  * @b: buffer to the source data; cannot be a global or const local
 296  *     (will confuse the scatterlists)
 297  */
 298 ssize_t wusb_prf(void *out, size_t out_size,
 299                  const u8 key[16], const struct aes_ccm_nonce *_n,
 300                  const struct aes_ccm_label *a,
 301                  const void *b, size_t blen, size_t len)
 302 {
 303         ssize_t result, bytes = 0, bitr;
 304         struct aes_ccm_nonce n = *_n;
 305         struct crypto_blkcipher *tfm_cbc;
 306         struct crypto_cipher *tfm_aes;
 307         u64 sfn = 0;
 308         __le64 sfn_le;
 309
 310         tfm_cbc = crypto_alloc_blkcipher("cbc(aes)", 0, CRYPTO_ALG_ASYNC);
 311         if (IS_ERR(tfm_cbc)) {
 312                 result = PTR_ERR(tfm_cbc);
 313                 printk(KERN_ERR "E: can't load CBC(AES): %d\n", (int)result);
 314                 goto error_alloc_cbc;
 315         }
 316         result = crypto_blkcipher_setkey(tfm_cbc, key, 16);
 317         if (result < 0) {
 318                 printk(KERN_ERR "E: can't set CBC key: %d\n", (int)result);
 319                 goto error_setkey_cbc;
 320         }
 321
 322         tfm_aes = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
 323         if (IS_ERR(tfm_aes)) {
 324                 result = PTR_ERR(tfm_aes);
 325                 printk(KERN_ERR "E: can't load AES: %d\n", (int)result);
 326                 goto error_alloc_aes;
 327         }
 328         result = crypto_cipher_setkey(tfm_aes, key, 16);
 329         if (result < 0) {
 330                 printk(KERN_ERR "E: can't set AES key: %d\n", (int)result);
 331                 goto error_setkey_aes;
 332         }
 333
 334         for (bitr = 0; bitr < (len + 63) / 64; bitr++) {
 335                 sfn_le = cpu_to_le64(sfn++);
 336                 memcpy(&n.sfn, &sfn_le, sizeof(n.sfn)); /* n.sfn++... */
 337                 result = wusb_ccm_mac(tfm_cbc, tfm_aes, out + bytes,
 338                                       &n, a, b, blen);
 339                 if (result < 0)
 340                         goto error_ccm_mac;
 341                 bytes += result;
 342         }
 343         result = bytes;
 344 error_ccm_mac:
 345 error_setkey_aes:
 346         crypto_free_cipher(tfm_aes);
 347 error_alloc_aes:
 348 error_setkey_cbc:
 349         crypto_free_blkcipher(tfm_cbc);
 350 error_alloc_cbc:
 351         return result;
 352 }
 353
 354 /* WUSB1.0[A.2] test vectors */
 355 static const u8 stv_hsmic_key[16] = {
 356         0x4b, 0x79, 0xa3, 0xcf, 0xe5, 0x53, 0x23, 0x9d,
 357         0xd7, 0xc1, 0x6d, 0x1c, 0x2d, 0xab, 0x6d, 0x3f
 358 };
 359
 360 static const struct aes_ccm_nonce stv_hsmic_n = {
 361         .sfn = { 0 },
 362         .tkid = { 0x76, 0x98, 0x01,  },
 363         .dest_addr = { .data = { 0xbe, 0x00 } },
 364                 .src_addr = { .data = { 0x76, 0x98 } },
 365 };
 366
 367 /*
 368  * Out-of-band MIC Generation verification code
 369  *
 370  */
 371 static int wusb_oob_mic_verify(void)
 372 {
 373         int result;
 374         u8 mic[8];
 375         /* WUSB1.0[A.2] test vectors
 376          *
 377          * Need to keep it in the local stack as GCC 4.1.3something
 378          * messes up and generates noise.
 379          */
 380         struct usb_handshake stv_hsmic_hs = {
 381                 .bMessageNumber = 2,
 382                 .bStatus        = 00,
 383                 .tTKID          = { 0x76, 0x98, 0x01 },
 384                 .bReserved      = 00,
 385                 .CDID           = { 0x30, 0x31, 0x32, 0x33, 0x34, 0x35,
 386                                     0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
 387                                     0x3c, 0x3d, 0x3e, 0x3f },
 388                 .nonce          = { 0x20, 0x21, 0x22, 0x23, 0x24, 0x25,
 389                                     0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,
 390                                     0x2c, 0x2d, 0x2e, 0x2f },
 391                 .MIC            = { 0x75, 0x6a, 0x97, 0x51, 0x0c, 0x8c,
 392                                     0x14, 0x7b } ,
 393         };
 394         size_t hs_size;
 395
 396         result = wusb_oob_mic(mic, stv_hsmic_key, &stv_hsmic_n, &stv_hsmic_hs);
 397         if (result < 0)
 398                 printk(KERN_ERR "E: WUSB OOB MIC test: failed: %d\n", result);
 399         else if (memcmp(stv_hsmic_hs.MIC, mic, sizeof(mic))) {
 400                 printk(KERN_ERR "E: OOB MIC test: "
 401                        "mismatch between MIC result and WUSB1.0[A2]\n");
 402                 hs_size = sizeof(stv_hsmic_hs) - sizeof(stv_hsmic_hs.MIC);
 403                 printk(KERN_ERR "E: Handshake2 in: (%zu bytes)\n", hs_size);
 404                 wusb_key_dump(&stv_hsmic_hs, hs_size);
 405                 printk(KERN_ERR "E: CCM Nonce in: (%zu bytes)\n",
 406                        sizeof(stv_hsmic_n));
 407                 wusb_key_dump(&stv_hsmic_n, sizeof(stv_hsmic_n));
 408                 printk(KERN_ERR "E: MIC out:\n");
 409                 wusb_key_dump(mic, sizeof(mic));
 410                 printk(KERN_ERR "E: MIC out (from WUSB1.0[A.2]):\n");
 411                 wusb_key_dump(stv_hsmic_hs.MIC, sizeof(stv_hsmic_hs.MIC));
 412                 result = -EINVAL;
 413         } else
 414                 result = 0;
 415         return result;
 416 }
 417
 418 /*
 419  * Test vectors for Key derivation
 420  *
 421  * These come from WUSB1.0[6.5.1], the vectors in WUSB1.0[A.1]
 422  * (errata corrected in 2005/07).
 423  */
 424 static const u8 stv_key_a1[16] __attribute__ ((__aligned__(4))) = {
 425         0xf0, 0xe1, 0xd2, 0xc3, 0xb4, 0xa5, 0x96, 0x87,
 426         0x78, 0x69, 0x5a, 0x4b, 0x3c, 0x2d, 0x1e, 0x0f
 427 };
 428
 429 static const struct aes_ccm_nonce stv_keydvt_n_a1 = {
 430         .sfn = { 0 },
 431         .tkid = { 0x76, 0x98, 0x01,  },
 432         .dest_addr = { .data = { 0xbe, 0x00 } },
 433         .src_addr = { .data = { 0x76, 0x98 } },
 434 };
 435
 436 static const struct wusb_keydvt_out stv_keydvt_out_a1 = {
 437         .kck = {
 438                 0x4b, 0x79, 0xa3, 0xcf, 0xe5, 0x53, 0x23, 0x9d,
 439                 0xd7, 0xc1, 0x6d, 0x1c, 0x2d, 0xab, 0x6d, 0x3f
 440         },
 441         .ptk = {
 442                 0xc8, 0x70, 0x62, 0x82, 0xb6, 0x7c, 0xe9, 0x06,
 443                 0x7b, 0xc5, 0x25, 0x69, 0xf2, 0x36, 0x61, 0x2d
 444         }
 445 };
 446
 447 /*
 448  * Performa a test to make sure we match the vectors defined in
 449  * WUSB1.0[A.1](Errata2006/12)
 450  */
 451 static int wusb_key_derive_verify(void)
 452 {
 453         int result = 0;
 454         struct wusb_keydvt_out keydvt_out;
 455         /* These come from WUSB1.0[A.1] + 2006/12 errata
 456          * NOTE: can't make this const or global -- somehow it seems
 457          *       the scatterlists for crypto get confused and we get
 458          *       bad data. There is no doc on this... */
 459         struct wusb_keydvt_in stv_keydvt_in_a1 = {
 460                 .hnonce = {
 461                         0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
 462                         0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f
 463                 },
 464                 .dnonce = {
 465                         0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
 466                         0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f
 467                 }
 468         };
 469
 470         result = wusb_key_derive(&keydvt_out, stv_key_a1, &stv_keydvt_n_a1,
 471                                  &stv_keydvt_in_a1);
 472         if (result < 0)
 473                 printk(KERN_ERR "E: WUSB key derivation test: "
 474                        "derivation failed: %d\n", result);
 475         if (memcmp(&stv_keydvt_out_a1, &keydvt_out, sizeof(keydvt_out))) {
 476                 printk(KERN_ERR "E: WUSB key derivation test: "
 477                        "mismatch between key derivation result "
 478                        "and WUSB1.0[A1] Errata 2006/12\n");
 479                 printk(KERN_ERR "E: keydvt in: key\n");
 480                 wusb_key_dump(stv_key_a1, sizeof(stv_key_a1));
 481                 printk(KERN_ERR "E: keydvt in: nonce\n");
 482                 wusb_key_dump( &stv_keydvt_n_a1, sizeof(stv_keydvt_n_a1));
 483                 printk(KERN_ERR "E: keydvt in: hnonce & dnonce\n");
 484                 wusb_key_dump(&stv_keydvt_in_a1, sizeof(stv_keydvt_in_a1));
 485                 printk(KERN_ERR "E: keydvt out: KCK\n");
 486                 wusb_key_dump(&keydvt_out.kck, sizeof(keydvt_out.kck));
 487                 printk(KERN_ERR "E: keydvt out: PTK\n");
 488                 wusb_key_dump(&keydvt_out.ptk, sizeof(keydvt_out.ptk));
 489                 result = -EINVAL;
 490         } else
 491                 result = 0;
 492         return result;
 493 }
 494
 495 /*
 496  * Initialize crypto system
 497  *
 498  * FIXME: we do nothing now, other than verifying. Later on we'll
 499  * cache the encryption stuff, so that's why we have a separate init.
 500  */
 501 int wusb_crypto_init(void)
 502 {
 503         int result;
 504
 505         if (debug_crypto_verify) {
 506                 result = wusb_key_derive_verify();
 507                 if (result < 0)
 508                         return result;
 509                 return wusb_oob_mic_verify();
 510         }
 511         return 0;
 512 }
 513
 514 void wusb_crypto_exit(void)
 515 {
 516         /* FIXME: free cached crypto transforms */
 517 }