diff options
Diffstat (limited to 'kernel/drivers/usb/wusbcore/crypto.c')
| -rw-r--r-- | kernel/drivers/usb/wusbcore/crypto.c | 516 |
1 files changed, 516 insertions, 0 deletions
diff --git a/kernel/drivers/usb/wusbcore/crypto.c b/kernel/drivers/usb/wusbcore/crypto.c new file mode 100644 index 000000000..50ce80d60 --- /dev/null +++ b/kernel/drivers/usb/wusbcore/crypto.c @@ -0,0 +1,516 @@ +/* + * 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\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 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\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 */ +} |