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