crypto.c revision e43ace891229607c43d35597cbba77c2e40f48d4
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 55static int debug_crypto_verify = 0; 56 57module_param(debug_crypto_verify, int, 0); 58MODULE_PARM_DESC(debug_crypto_verify, "verify the key generation algorithms"); 59 60static 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 */ 73struct 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] */ 94struct 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] */ 101struct 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 */ 118struct 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 124static 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 */ 197static 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; 286error_cbc_crypt: 287 kfree(dst_buf); 288error_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 */ 298ssize_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; 344error_ccm_mac: 345error_setkey_aes: 346 crypto_free_cipher(tfm_aes); 347error_alloc_aes: 348error_setkey_cbc: 349 crypto_free_blkcipher(tfm_cbc); 350error_alloc_cbc: 351 return result; 352} 353 354/* WUSB1.0[A.2] test vectors */ 355static 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 360static 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 */ 371static 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 */ 424static 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 429static 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 436static 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 */ 451static 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 */ 501int 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 514void wusb_crypto_exit(void) 515{ 516 /* FIXME: free cached crypto transforms */ 517} 518