/*
* Copyright (c) 2009 Joshua Oreman <oremanj@rwcr.net>.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or any later version.
*
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
FILE_LICENCE ( GPL2_OR_LATER );
#include <gpxe/net80211.h>
#include <gpxe/crypto.h>
#include <gpxe/hmac.h>
#include <gpxe/sha1.h>
#include <gpxe/aes.h>
#include <gpxe/wpa.h>
#include <byteswap.h>
#include <errno.h>
/** @file
*
* Backend for WPA using the CCMP encryption method
*/
/** Context for CCMP encryption and decryption */
struct ccmp_ctx
{
/** AES context - only ever used for encryption */
u8 aes_ctx[AES_CTX_SIZE];
/** Most recently sent packet number */
u64 tx_seq;
/** Most recently received packet number */
u64 rx_seq;
};
/** Header structure at the beginning of CCMP frame data */
struct ccmp_head
{
u8 pn_lo[2]; /**< Bytes 0 and 1 of packet number */
u8 _rsvd; /**< Reserved byte */
u8 kid; /**< Key ID and ExtIV byte */
u8 pn_hi[4]; /**< Bytes 2-5 (2 first) of packet number */
} __attribute__ (( packed ));
/** CCMP header overhead */
#define CCMP_HEAD_LEN 8
/** CCMP MIC trailer overhead */
#define CCMP_MIC_LEN 8
/** CCMP nonce length */
#define CCMP_NONCE_LEN 13
/** CCMP nonce structure */
struct ccmp_nonce
{
u8 prio; /**< Packet priority, 0 for non-QoS */
u8 a2[ETH_ALEN]; /**< Address 2 from packet header (sender) */
u8 pn[6]; /**< Packet number */
} __attribute__ (( packed ));
/** CCMP additional authentication data length (for non-QoS, non-WDS frames) */
#define CCMP_AAD_LEN 22
/** CCMP additional authentication data structure */
struct ccmp_aad
{
u16 fc; /**< Frame Control field */
u8 a1[6]; /**< Address 1 */
u8 a2[6]; /**< Address 2 */
u8 a3[6]; /**< Address 3 */
u16 seq; /**< Sequence Control field */
/* Address 4 and QoS Control are included if present */
} __attribute__ (( packed ));
/** Mask for Frame Control field in AAD */
#define CCMP_AAD_FC_MASK 0xC38F
/** Mask for Sequence Control field in AAD */
#define CCMP_AAD_SEQ_MASK 0x000F
/**
* Convert 6-byte LSB packet number to 64-bit integer
*
* @v pn Pointer to 6-byte packet number
* @ret v 64-bit integer value of @a pn
*/
static u64 pn_to_u64 ( const u8 *pn )
{
int i;
u64 ret = 0;
for ( i = 5; i >= 0; i-- ) {
ret <<= 8;
ret |= pn[i];
}
return ret;
}
/**
* Convert 64-bit integer to 6-byte packet number
*
* @v v 64-bit integer
* @v msb If TRUE, reverse the output PN to be in MSB order
* @ret pn 6-byte packet number
*
* The PN is stored in LSB order in the packet header and in MSB order
* in the nonce. WHYYYYY?
*/
static void u64_to_pn ( u64 v, u8 *pn, int msb )
{
int i;
u8 *pnp = pn + ( msb ? 5 : 0 );
int delta = ( msb ? -1 : +1 );
for ( i = 0; i < 6; i++ ) {
*pnp = v & 0xFF;
pnp += delta;
v >>= 8;
}
}
/** Value for @a msb argument of u64_to_pn() for MSB output */
#define PN_MSB 1
/** Value for @a msb argument of u64_to_pn() for LSB output */
#define PN_LSB 0
/**
* Initialise CCMP state and install key
*
* @v crypto CCMP cryptosystem structure
* @v key Pointer to 16-byte temporal key to install
* @v keylen Length of key (16 bytes)
* @v rsc Initial receive sequence counter
*/
static int ccmp_init ( struct net80211_crypto *crypto, const void *key,
int keylen, const void *rsc )
{
struct ccmp_ctx *ctx = crypto->priv;
if ( keylen != 16 )
return -EINVAL;
if ( rsc )
ctx->rx_seq = pn_to_u64 ( rsc );
cipher_setkey ( &aes_algorithm, ctx->aes_ctx, key, keylen );
return 0;
}
/**
* Encrypt or decrypt data stream using AES in Counter mode
*
* @v ctx CCMP cryptosystem context
* @v nonce Nonce value, 13 bytes
* @v srcv Data to encrypt or decrypt
* @v len Number of bytes pointed to by @a src
* @v msrcv MIC value to encrypt or decrypt (may be NULL)
* @ret destv Encrypted or decrypted data
* @ret mdestv Encrypted or decrypted MIC value
*
* This assumes CCMP parameters of L=2 and M=8. The algorithm is
* defined in RFC 3610.
*/
static void ccmp_ctr_xor ( struct ccmp_ctx *ctx, const void *nonce,
const void *srcv, void *destv, int len,
const void *msrcv, void *mdestv )
{
u8 A[16], S[16];
u16 ctr;
int i;
const u8 *src = srcv, *msrc = msrcv;
u8 *dest = destv, *mdest = mdestv;
A[0] = 0x01; /* flags, L' = L - 1 = 1, other bits rsvd */
memcpy ( A + 1, nonce, CCMP_NONCE_LEN );
if ( msrcv ) {
A[14] = A[15] = 0;
cipher_encrypt ( &aes_algorithm, ctx->aes_ctx, A, S, 16 );
for ( i = 0; i < 8; i++ ) {
*mdest++ = *msrc++ ^ S[i];
}
}
for ( ctr = 1 ;; ctr++ ) {
A[14] = ctr >> 8;
A[15] = ctr & 0xFF;
cipher_encrypt ( &aes_algorithm, ctx->aes_ctx, A, S, 16 );
for ( i = 0; i < len && i < 16; i++ )
*dest++ = *src++ ^ S[i];
if ( len <= 16 )
break; /* we're done */
len -= 16;
}
}
/**
* Advance one block in CBC-MAC calculation
*
* @v aes_ctx AES encryption context with key set
* @v B Cleartext block to incorporate (16 bytes)
* @v X Previous ciphertext block (16 bytes)
* @ret B Clobbered
* @ret X New ciphertext block (16 bytes)
*
* This function does X := E[key] ( X ^ B ).
*/
static void ccmp_feed_cbc_mac ( void *aes_ctx, u8 *B, u8 *X )
{
int i;
for ( i = 0; i < 16; i++ )
B[i] ^= X[i];
cipher_encrypt ( &aes_algorithm, aes_ctx, B, X, 16 );
}
/**
* Calculate MIC on plaintext data using CBC-MAC
*
* @v ctx CCMP cryptosystem context
* @v nonce Nonce value, 13 bytes
* @v data Data to calculate MIC over
* @v datalen Length of @a data
* @v aad Additional authentication data, for MIC but not encryption
* @ret mic MIC value (unencrypted), 8 bytes
*
* @a aadlen is assumed to be 22 bytes long, as it always is for
* 802.11 use when transmitting non-QoS, not-between-APs frames (the
* only type we deal with).
*/
static void ccmp_cbc_mac ( struct ccmp_ctx *ctx, const void *nonce,
const void *data, u16 datalen,
const void *aad, void *mic )
{
u8 X[16], B[16];
/* Zeroth block: flags, nonce, length */
/* Rsv AAD - M'- - L'-
* 0 1 0 1 1 0 0 1 for an 8-byte MAC and 2-byte message length
*/
B[0] = 0x59;
memcpy ( B + 1, nonce, CCMP_NONCE_LEN );
B[14] = datalen >> 8;
B[15] = datalen & 0xFF;
cipher_encrypt ( &aes_algorithm, ctx->aes_ctx, B, X, 16 );
/* First block: AAD length field and 14 bytes of AAD */
B[0] = 0;
B[1] = CCMP_AAD_LEN;
memcpy ( B + 2, aad, 14 );
ccmp_feed_cbc_mac ( ctx->aes_ctx, B, X );
/* Second block: Remaining 8 bytes of AAD, 8 bytes zero pad */
memcpy ( B, aad + 14, 8 );
memset ( B + 8, 0, 8 );
ccmp_feed_cbc_mac ( ctx->aes_ctx, B, X );
/* Message blocks */
while ( datalen ) {
if ( datalen >= 16 ) {
memcpy ( B, data, 16 );
datalen -= 16;
} else {
memcpy ( B, data, datalen );
memset ( B + datalen, 0, 16 - datalen );
datalen = 0;
}
ccmp_feed_cbc_mac ( ctx->aes_ctx, B, X );
data += 16;
}
/* Get MIC from final value of X */
memcpy ( mic, X, 8 );
}
/**
* Encapsulate and encrypt a packet using CCMP
*
* @v crypto CCMP cryptosystem
* @v iob I/O buffer containing cleartext packet
* @ret eiob I/O buffer containing encrypted packet
*/
struct io_buffer * ccmp_encrypt ( struct net80211_crypto *crypto,
struct io_buffer *iob )
{
struct ccmp_ctx *ctx = crypto->priv;
struct ieee80211_frame *hdr = iob->data;
struct io_buffer *eiob;
const int hdrlen = IEEE80211_TYP_FRAME_HEADER_LEN;
int datalen = iob_len ( iob ) - hdrlen;
struct ccmp_head head;
struct ccmp_nonce nonce;
struct ccmp_aad aad;
u8 mic[8], tx_pn[6];
void *edata, *emic;
ctx->tx_seq++;
u64_to_pn ( ctx->tx_seq, tx_pn, PN_LSB );
/* Allocate memory */
eiob = alloc_iob ( iob_len ( iob ) + CCMP_HEAD_LEN + CCMP_MIC_LEN );
if ( ! eiob )
return NULL;
/* Copy frame header */
memcpy ( iob_put ( eiob, hdrlen ), iob->data, hdrlen );
hdr = eiob->data;
hdr->fc |= IEEE80211_FC_PROTECTED;
/* Fill in packet number and extended IV */
memcpy ( head.pn_lo, tx_pn, 2 );
memcpy ( head.pn_hi, tx_pn + 2, 4 );
head.kid = 0x20; /* have Extended IV, key ID 0 */
head._rsvd = 0;
memcpy ( iob_put ( eiob, sizeof ( head ) ), &head, sizeof ( head ) );
/* Form nonce */
nonce.prio = 0;
memcpy ( nonce.a2, hdr->addr2, ETH_ALEN );
u64_to_pn ( ctx->tx_seq, nonce.pn, PN_MSB );
/* Form additional authentication data */
aad.fc = hdr->fc & CCMP_AAD_FC_MASK;
memcpy ( aad.a1, hdr->addr1, 3 * ETH_ALEN ); /* all 3 at once */
aad.seq = hdr->seq & CCMP_AAD_SEQ_MASK;
/* Calculate MIC over the data */
ccmp_cbc_mac ( ctx, &nonce, iob->data + hdrlen, datalen, &aad, mic );
/* Copy and encrypt data and MIC */
edata = iob_put ( eiob, datalen );
emic = iob_put ( eiob, CCMP_MIC_LEN );
ccmp_ctr_xor ( ctx, &nonce,
iob->data + hdrlen, edata, datalen,
mic, emic );
/* Done! */
DBGC2 ( ctx, "WPA-CCMP %p: encrypted packet %p -> %p\n", ctx,
iob, eiob );
return eiob;
}
/**
* Decrypt a packet using CCMP
*
* @v crypto CCMP cryptosystem
* @v eiob I/O buffer containing encrypted packet
* @ret iob I/O buffer containing cleartext packet
*/
static struct io_buffer * ccmp_decrypt ( struct net80211_crypto *crypto,
struct io_buffer *eiob )
{
struct ccmp_ctx *ctx = crypto->priv;
struct ieee80211_frame *hdr;
struct io_buffer *iob;
const int hdrlen = IEEE80211_TYP_FRAME_HEADER_LEN;
int datalen = iob_len ( eiob ) - hdrlen - CCMP_HEAD_LEN - CCMP_MIC_LEN;
struct ccmp_head *head;
struct ccmp_nonce nonce;
struct ccmp_aad aad;
u8 rx_pn[6], their_mic[8], our_mic[8];
iob = alloc_iob ( hdrlen + datalen );
if ( ! iob )
return NULL;
/* Copy frame header */
memcpy ( iob_put ( iob, hdrlen ), eiob->data, hdrlen );
hdr = iob->data;
hdr->fc &= ~IEEE80211_FC_PROTECTED;
/* Check and update RX packet number */
head = eiob->data + hdrlen;
memcpy ( rx_pn, head->pn_lo, 2 );
memcpy ( rx_pn + 2, head->pn_hi, 4 );
if ( pn_to_u64 ( rx_pn ) <= ctx->rx_seq ) {
DBGC ( ctx, "WPA-CCMP %p: packet received out of order "
"(%012llx <= %012llx)\n", ctx, pn_to_u64 ( rx_pn ),
ctx->rx_seq );
free_iob ( iob );
return NULL;
}
ctx->rx_seq = pn_to_u64 ( rx_pn );
DBGC2 ( ctx, "WPA-CCMP %p: RX packet number %012llx\n", ctx, ctx->rx_seq );
/* Form nonce */
nonce.prio = 0;
memcpy ( nonce.a2, hdr->addr2, ETH_ALEN );
u64_to_pn ( ctx->rx_seq, nonce.pn, PN_MSB );
/* Form additional authentication data */
aad.fc = ( hdr->fc & CCMP_AAD_FC_MASK ) | IEEE80211_FC_PROTECTED;
memcpy ( aad.a1, hdr->addr1, 3 * ETH_ALEN ); /* all 3 at once */
aad.seq = hdr->seq & CCMP_AAD_SEQ_MASK;
/* Copy-decrypt data and MIC */
ccmp_ctr_xor ( ctx, &nonce, eiob->data + hdrlen + sizeof ( *head ),
iob_put ( iob, datalen ), datalen,
eiob->tail - CCMP_MIC_LEN, their_mic );
/* Check MIC */
ccmp_cbc_mac ( ctx, &nonce, iob->data + hdrlen, datalen, &aad,
our_mic );
if ( memcmp ( their_mic, our_mic, CCMP_MIC_LEN ) != 0 ) {
DBGC2 ( ctx, "WPA-CCMP %p: MIC failure\n", ctx );
free_iob ( iob );
return NULL;
}
DBGC2 ( ctx, "WPA-CCMP %p: decrypted packet %p -> %p\n", ctx,
eiob, iob );
return iob;
}
/** CCMP cryptosystem */
struct net80211_crypto ccmp_crypto __net80211_crypto = {
.algorithm = NET80211_CRYPT_CCMP,
.init = ccmp_init,
.encrypt = ccmp_encrypt,
.decrypt = ccmp_decrypt,
.priv_len = sizeof ( struct ccmp_ctx ),
};
/**
* Calculate HMAC-SHA1 MIC for EAPOL-Key frame
*
* @v kck Key Confirmation Key, 16 bytes
* @v msg Message to calculate MIC over
* @v len Number of bytes to calculate MIC over
* @ret mic Calculated MIC, 16 bytes long
*/
static void ccmp_kie_mic ( const void *kck, const void *msg, size_t len,
void *mic )
{
u8 sha1_ctx[SHA1_CTX_SIZE];
u8 kckb[16];
u8 hash[SHA1_SIZE];
size_t kck_len = 16;
memcpy ( kckb, kck, kck_len );
hmac_init ( &sha1_algorithm, sha1_ctx, kckb, &kck_len );
hmac_update ( &sha1_algorithm, sha1_ctx, msg, len );
hmac_final ( &sha1_algorithm, sha1_ctx, kckb, &kck_len, hash );
memcpy ( mic, hash, 16 );
}
/**
* Decrypt key data in EAPOL-Key frame
*
* @v kek Key Encryption Key, 16 bytes
* @v iv Initialisation vector, 16 bytes (unused)
* @v msg Message to decrypt
* @v len Length of message
* @ret msg Decrypted message in place of original
* @ret len Adjusted downward for 8 bytes of overhead
* @ret rc Return status code
*
* The returned message may still contain padding of 0xDD followed by
* zero or more 0x00 octets. It is impossible to remove the padding
* without parsing the IEs in the packet (another design decision that
* tends to make one question the 802.11i committee's intelligence...)
*/
static int ccmp_kie_decrypt ( const void *kek, const void *iv __unused,
void *msg, u16 *len )
{
if ( *len % 8 != 0 )
return -EINVAL;
if ( aes_unwrap ( kek, msg, msg, *len / 8 - 1 ) != 0 )
return -EINVAL;
*len -= 8;
return 0;
}
/** CCMP-style key integrity and encryption handler */
struct wpa_kie ccmp_kie __wpa_kie = {
.version = EAPOL_KEY_VERSION_WPA2,
.mic = ccmp_kie_mic,
.decrypt = ccmp_kie_decrypt,
};