[wpa] Add TKIP backend (legacy RC4-based cryptosystem)

Signed-off-by: Marty Connor <mdc@etherboot.org>

4 files changed, 593 insertions, 1 deletions

diff --git a/src/config/config_net80211.c b/src/config/config_net80211.c
index 59986b90..b1b640d7 100644
--- a/src/config/config_net80211.c
+++ b/src/config/config_net80211.c
@@ -38,3 +38,8 @@ REQUIRE_OBJECT ( wireless_errors );
 #ifdef CRYPTO_80211_WEP
 REQUIRE_OBJECT ( wep );
 #endif
+
+#ifdef CRYPTO_80211_WPA
+REQUIRE_OBJECT ( wpa_psk );
+REQUIRE_OBJECT ( wpa_tkip );
+#endif
diff --git a/src/config/general.h b/src/config/general.h
index 8855a872..72fda10d 100644
--- a/src/config/general.h
+++ b/src/config/general.h
@@ -69,7 +69,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
  *
  */
 #define	CRYPTO_80211_WEP	/* WEP encryption (deprecated and insecure!) */
-#define CRYPTO_80211_WPA_PSK	/* WPA "Personal" frontend using a passphrase */
+#define	CRYPTO_80211_WPA	/* WPA Personal, authenticating with passphrase */
 
 /*
  * Name resolution modules
diff --git a/src/include/gpxe/errfile.h b/src/include/gpxe/errfile.h
index b79ac437..d5d6a31b 100644
--- a/src/include/gpxe/errfile.h
+++ b/src/include/gpxe/errfile.h
@@ -163,6 +163,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define ERRFILE_eapol			( ERRFILE_NET | 0x00250000 )
 #define ERRFILE_wpa			( ERRFILE_NET | 0x00260000 )
 #define ERRFILE_wpa_psk			( ERRFILE_NET | 0x00270000 )
+#define ERRFILE_wpa_tkip		( ERRFILE_NET | 0x00280000 )
 
 #define ERRFILE_image		      ( ERRFILE_IMAGE | 0x00000000 )
 #define ERRFILE_elf		      ( ERRFILE_IMAGE | 0x00010000 )
diff --git a/src/net/80211/wpa_tkip.c b/src/net/80211/wpa_tkip.c
new file mode 100644
index 00000000..0cb697fa
--- /dev/null
+++ b/src/net/80211/wpa_tkip.c
@@ -0,0 +1,586 @@
+/*
+ * 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/md5.h>
+#include <gpxe/crc32.h>
+#include <gpxe/arc4.h>
+#include <gpxe/wpa.h>
+#include <byteswap.h>
+#include <errno.h>
+
+/** @file
+ *
+ * Backend for WPA using the TKIP encryption standard.
+ */
+
+/** Context for one direction of TKIP, either encryption or decryption */
+struct tkip_dir_ctx
+{
+	/** High 32 bits of last sequence counter value used */
+	u32 tsc_hi;
+
+	/** Low 32 bits of last sequence counter value used */
+	u16 tsc_lo;
+
+	/** MAC address used to derive TTAK */
+	u8 mac[ETH_ALEN];
+
+	/** If TRUE, TTAK is valid */
+	u16 ttak_ok;
+
+	/** TKIP-mixed transmit address and key, depends on tsc_hi and MAC */
+	u16 ttak[5];
+};
+
+/** Context for TKIP encryption and decryption */
+struct tkip_ctx
+{
+	/** Temporal key to use */
+	struct tkip_tk tk;
+
+	/** State for encryption */
+	struct tkip_dir_ctx enc;
+
+	/** State for decryption */
+	struct tkip_dir_ctx dec;
+};
+
+/** Header structure at the beginning of TKIP frame data */
+struct tkip_head
+{
+	u8 tsc1;		/**< High byte of low 16 bits of TSC */
+	u8 seed1;		/**< Second byte of WEP seed */
+	u8 tsc0;		/**< Low byte of TSC */
+	u8 kid;			/**< Key ID and ExtIV byte */
+	u32 tsc_hi;		/**< High 32 bits of TSC, as an ExtIV */
+} __attribute__ (( packed ));
+
+
+/** TKIP header overhead (IV + KID + ExtIV) */
+#define TKIP_HEAD_LEN	8
+
+/** TKIP trailer overhead (MIC + ICV) [assumes unfragmented] */
+#define TKIP_FOOT_LEN	12
+
+/** TKIP MIC length */
+#define TKIP_MIC_LEN	8
+
+/** TKIP ICV length */
+#define TKIP_ICV_LEN	4
+
+
+/** TKIP S-box */
+static const u16 Sbox[256] = {
+	0xC6A5, 0xF884, 0xEE99, 0xF68D, 0xFF0D, 0xD6BD, 0xDEB1, 0x9154,
+	0x6050, 0x0203, 0xCEA9, 0x567D, 0xE719, 0xB562, 0x4DE6, 0xEC9A,
+	0x8F45, 0x1F9D, 0x8940, 0xFA87, 0xEF15, 0xB2EB, 0x8EC9, 0xFB0B,
+	0x41EC, 0xB367, 0x5FFD, 0x45EA, 0x23BF, 0x53F7, 0xE496, 0x9B5B,
+	0x75C2, 0xE11C, 0x3DAE, 0x4C6A, 0x6C5A, 0x7E41, 0xF502, 0x834F,
+	0x685C, 0x51F4, 0xD134, 0xF908, 0xE293, 0xAB73, 0x6253, 0x2A3F,
+	0x080C, 0x9552, 0x4665, 0x9D5E, 0x3028, 0x37A1, 0x0A0F, 0x2FB5,
+	0x0E09, 0x2436, 0x1B9B, 0xDF3D, 0xCD26, 0x4E69, 0x7FCD, 0xEA9F,
+	0x121B, 0x1D9E, 0x5874, 0x342E, 0x362D, 0xDCB2, 0xB4EE, 0x5BFB,
+	0xA4F6, 0x764D, 0xB761, 0x7DCE, 0x527B, 0xDD3E, 0x5E71, 0x1397,
+	0xA6F5, 0xB968, 0x0000, 0xC12C, 0x4060, 0xE31F, 0x79C8, 0xB6ED,
+	0xD4BE, 0x8D46, 0x67D9, 0x724B, 0x94DE, 0x98D4, 0xB0E8, 0x854A,
+	0xBB6B, 0xC52A, 0x4FE5, 0xED16, 0x86C5, 0x9AD7, 0x6655, 0x1194,
+	0x8ACF, 0xE910, 0x0406, 0xFE81, 0xA0F0, 0x7844, 0x25BA, 0x4BE3,
+	0xA2F3, 0x5DFE, 0x80C0, 0x058A, 0x3FAD, 0x21BC, 0x7048, 0xF104,
+	0x63DF, 0x77C1, 0xAF75, 0x4263, 0x2030, 0xE51A, 0xFD0E, 0xBF6D,
+	0x814C, 0x1814, 0x2635, 0xC32F, 0xBEE1, 0x35A2, 0x88CC, 0x2E39,
+	0x9357, 0x55F2, 0xFC82, 0x7A47, 0xC8AC, 0xBAE7, 0x322B, 0xE695,
+	0xC0A0, 0x1998, 0x9ED1, 0xA37F, 0x4466, 0x547E, 0x3BAB, 0x0B83,
+	0x8CCA, 0xC729, 0x6BD3, 0x283C, 0xA779, 0xBCE2, 0x161D, 0xAD76,
+	0xDB3B, 0x6456, 0x744E, 0x141E, 0x92DB, 0x0C0A, 0x486C, 0xB8E4,
+	0x9F5D, 0xBD6E, 0x43EF, 0xC4A6, 0x39A8, 0x31A4, 0xD337, 0xF28B,
+	0xD532, 0x8B43, 0x6E59, 0xDAB7, 0x018C, 0xB164, 0x9CD2, 0x49E0,
+	0xD8B4, 0xACFA, 0xF307, 0xCF25, 0xCAAF, 0xF48E, 0x47E9, 0x1018,
+	0x6FD5, 0xF088, 0x4A6F, 0x5C72, 0x3824, 0x57F1, 0x73C7, 0x9751,
+	0xCB23, 0xA17C, 0xE89C, 0x3E21, 0x96DD, 0x61DC, 0x0D86, 0x0F85,
+	0xE090, 0x7C42, 0x71C4, 0xCCAA, 0x90D8, 0x0605, 0xF701, 0x1C12,
+	0xC2A3, 0x6A5F, 0xAEF9, 0x69D0, 0x1791, 0x9958, 0x3A27, 0x27B9,
+	0xD938, 0xEB13, 0x2BB3, 0x2233, 0xD2BB, 0xA970, 0x0789, 0x33A7,
+	0x2DB6, 0x3C22, 0x1592, 0xC920, 0x8749, 0xAAFF, 0x5078, 0xA57A,
+	0x038F, 0x59F8, 0x0980, 0x1A17, 0x65DA, 0xD731, 0x84C6, 0xD0B8,
+	0x82C3, 0x29B0, 0x5A77, 0x1E11, 0x7BCB, 0xA8FC, 0x6DD6, 0x2C3A,
+};
+
+/**
+ * Perform S-box mapping on a 16-bit value
+ *
+ * @v v		Value to perform S-box mapping on
+ * @ret Sv	S-box mapped value
+ */
+static inline u16 S ( u16 v )
+{
+	return Sbox[v & 0xFF] ^ swap16 ( Sbox[v >> 8] );
+}
+
+/**
+ * Rotate 16-bit value right
+ *
+ * @v v		Value to rotate
+ * @v bits	Number of bits to rotate by
+ * @ret rotv	Rotated value
+ */
+static inline u16 ror16 ( u16 v, int bits )
+{
+	return ( v >> bits ) | ( v << ( 16 - bits ) );
+}
+
+/**
+ * Rotate 32-bit value right
+ *
+ * @v v		Value to rotate
+ * @v bits	Number of bits to rotate by
+ * @ret rotv	Rotated value
+ */
+static inline u32 ror32 ( u32 v, int bits )
+{
+	return ( v >> bits ) | ( v << ( 32 - bits ) );
+}
+
+/**
+ * Rotate 32-bit value left
+ *
+ * @v v		Value to rotate
+ * @v bits	Number of bits to rotate by
+ * @ret rotv	Rotated value
+ */
+static inline u32 rol32 ( u32 v, int bits )
+{
+	return ( v << bits ) | ( v >> ( 32 - bits ) );
+}
+
+
+/**
+ * Initialise TKIP state and install key
+ *
+ * @v crypto	TKIP cryptosystem structure
+ * @v key	Pointer to tkip_tk to install
+ * @v keylen	Length of key (32 bytes)
+ * @v rsc	Initial receive sequence counter
+ */
+static int tkip_init ( struct net80211_crypto *crypto, const void *key,
+		       int keylen, const void *rsc )
+{
+	struct tkip_ctx *ctx = crypto->priv;
+	const u8 *rscb = rsc;
+
+	if ( keylen != sizeof ( ctx->tk ) )
+		return -EINVAL;
+
+	if ( rscb ) {
+		ctx->dec.tsc_lo =   ( rscb[1] <<  8 ) |   rscb[0];
+		ctx->dec.tsc_hi = ( ( rscb[5] << 24 ) | ( rscb[4] << 16 ) |
+				    ( rscb[3] <<  8 ) |   rscb[2] );
+	}
+
+	memcpy ( &ctx->tk, key, sizeof ( ctx->tk ) );
+
+	return 0;
+}
+
+/**
+ * Perform TKIP key mixing, phase 1
+ *
+ * @v dctx	TKIP directional context
+ * @v tk	TKIP temporal key
+ * @v mac	MAC address of transmitter
+ *
+ * This recomputes the TTAK in @a dctx if necessary, and sets
+ * @c dctx->ttak_ok.
+ */
+static void tkip_mix_1 ( struct tkip_dir_ctx *dctx, struct tkip_tk *tk, u8 *mac )
+{
+	int i, j;
+
+	if ( dctx->ttak_ok && ! memcmp ( mac, dctx->mac, ETH_ALEN ) )
+		return;
+
+	memcpy ( dctx->mac, mac, ETH_ALEN );
+
+	dctx->ttak[0] = dctx->tsc_hi & 0xFFFF;
+	dctx->ttak[1] = dctx->tsc_hi >> 16;
+	dctx->ttak[2] = ( mac[1] << 8 ) | mac[0];
+	dctx->ttak[3] = ( mac[3] << 8 ) | mac[2];
+	dctx->ttak[4] = ( mac[5] << 8 ) | mac[4];
+
+	for ( i = 0; i < 8; i++ ) {
+		j = 2 * ( i & 1 );
+
+		dctx->ttak[0] += S ( dctx->ttak[4] ^ ( ( tk->key[1 + j] << 8 ) |
+						         tk->key[0 + j] ) );
+		dctx->ttak[1] += S ( dctx->ttak[0] ^ ( ( tk->key[5 + j] << 8 ) |
+						         tk->key[4 + j] ) );
+		dctx->ttak[2] += S ( dctx->ttak[1] ^ ( ( tk->key[9 + j] << 8 ) |
+						         tk->key[8 + j] ) );
+		dctx->ttak[3] += S ( dctx->ttak[2] ^ ( ( tk->key[13+ j] << 8 ) |
+						         tk->key[12+ j] ) );
+		dctx->ttak[4] += S ( dctx->ttak[3] ^ ( ( tk->key[1 + j] << 8 ) |
+						         tk->key[0 + j] ) ) + i;
+	}
+
+	dctx->ttak_ok = 1;
+}
+
+/**
+ * Perform TKIP key mixing, phase 2
+ *
+ * @v dctx	TKIP directional context
+ * @v tk	TKIP temporal key
+ * @ret key	ARC4 key, 16 bytes long
+ */
+static void tkip_mix_2 ( struct tkip_dir_ctx *dctx, struct tkip_tk *tk,
+			 void *key )
+{
+	u8 *kb = key;
+	u16 ppk[6];
+	int i;
+
+	memcpy ( ppk, dctx->ttak, sizeof ( dctx->ttak ) );
+	ppk[5] = dctx->ttak[4] + dctx->tsc_lo;
+
+	ppk[0] += S ( ppk[5] ^ ( ( tk->key[1] << 8 ) | tk->key[0] ) );
+	ppk[1] += S ( ppk[0] ^ ( ( tk->key[3] << 8 ) | tk->key[2] ) );
+	ppk[2] += S ( ppk[1] ^ ( ( tk->key[5] << 8 ) | tk->key[4] ) );
+	ppk[3] += S ( ppk[2] ^ ( ( tk->key[7] << 8 ) | tk->key[6] ) );
+	ppk[4] += S ( ppk[3] ^ ( ( tk->key[9] << 8 ) | tk->key[8] ) );
+	ppk[5] += S ( ppk[4] ^ ( ( tk->key[11] << 8 ) | tk->key[10] ) );
+
+	ppk[0] += ror16 ( ppk[5] ^ ( ( tk->key[13] << 8 ) | tk->key[12] ), 1 );
+	ppk[1] += ror16 ( ppk[0] ^ ( ( tk->key[15] << 8 ) | tk->key[14] ), 1 );
+	ppk[2] += ror16 ( ppk[1], 1 );
+	ppk[3] += ror16 ( ppk[2], 1 );
+	ppk[4] += ror16 ( ppk[3], 1 );
+	ppk[5] += ror16 ( ppk[4], 1 );
+
+	kb[0] = dctx->tsc_lo >> 8;
+	kb[1] = ( ( dctx->tsc_lo >> 8 ) | 0x20 ) & 0x7F;
+	kb[2] = dctx->tsc_lo & 0xFF;
+	kb[3] = ( ( ppk[5] ^ ( ( tk->key[1] << 8 ) | tk->key[0] ) ) >> 1 )
+		& 0xFF;
+
+	for ( i = 0; i < 6; i++ ) {
+		kb[4 + 2*i] = ppk[i] & 0xFF;
+		kb[5 + 2*i] = ppk[i] >> 8;
+	}
+}
+
+/**
+ * Update Michael message integrity code based on next 32-bit word of data
+ *
+ * @v V		Michael code state (two 32-bit words)
+ * @v word	Next 32-bit word of data
+ */
+static void tkip_feed_michael ( u32 *V, u32 word )
+{
+	V[0] ^= word;
+	V[1] ^= rol32 ( V[0], 17 );
+	V[0] += V[1];
+	V[1] ^= ( ( V[0] & 0xFF00FF00 ) >> 8 ) | ( ( V[0] & 0x00FF00FF ) << 8 );
+	V[0] += V[1];
+	V[1] ^= rol32 ( V[0], 3 );
+	V[0] += V[1];
+	V[1] ^= ror32 ( V[0], 2 );
+	V[0] += V[1];
+}
+
+/**
+ * Calculate Michael message integrity code
+ *
+ * @v key	MIC key to use (8 bytes)
+ * @v da	Destination link-layer address
+ * @v sa	Source link-layer address
+ * @v data	Start of data to calculate over
+ * @v len	Length of header + data
+ * @ret mic	Calculated Michael MIC (8 bytes)
+ */
+static void tkip_michael ( const void *key, const void *da, const void *sa,
+			   const void *data, size_t len, void *mic )
+{
+	u32 V[2];		/* V[0] = "l", V[1] = "r" in 802.11 */
+	union {
+		u8 byte[12];
+		u32 word[3];
+	} cap;
+	const u8 *ptr = data;
+	const u8 *end = ptr + len;
+	int i;
+
+	memcpy ( V, key, sizeof ( V ) );
+	V[0] = le32_to_cpu ( V[0] );
+	V[1] = le32_to_cpu ( V[1] );
+
+	/* Feed in header (we assume non-QoS, so Priority = 0) */
+	memcpy ( &cap.byte[0], da, ETH_ALEN );
+	memcpy ( &cap.byte[6], sa, ETH_ALEN );
+	tkip_feed_michael ( V, le32_to_cpu ( cap.word[0] ) );
+	tkip_feed_michael ( V, le32_to_cpu ( cap.word[1] ) );
+	tkip_feed_michael ( V, le32_to_cpu ( cap.word[2] ) );
+	tkip_feed_michael ( V, 0 );
+
+	/* Feed in data */
+	while ( ptr + 4 <= end ) {
+		tkip_feed_michael ( V, le32_to_cpu ( *( u32 * ) ptr ) );
+		ptr += 4;
+	}
+
+	/* Add unaligned part and padding */
+	for ( i = 0; ptr < end; i++ )
+		cap.byte[i] = *ptr++;
+	cap.byte[i++] = 0x5a;
+	for ( ; i < 8; i++ )
+		cap.byte[i] = 0;
+
+	/* Feed in padding */
+	tkip_feed_michael ( V, le32_to_cpu ( cap.word[0] ) );
+	tkip_feed_michael ( V, le32_to_cpu ( cap.word[1] ) );
+
+	/* Output MIC */
+	V[0] = cpu_to_le32 ( V[0] );
+	V[1] = cpu_to_le32 ( V[1] );
+	memcpy ( mic, V, sizeof ( V ) );
+}
+
+/**
+ * Encrypt a packet using TKIP
+ *
+ * @v crypto	TKIP cryptosystem
+ * @v iob	I/O buffer containing cleartext packet
+ * @ret eiob	I/O buffer containing encrypted packet
+ */
+static struct io_buffer * tkip_encrypt ( struct net80211_crypto *crypto,
+					 struct io_buffer *iob )
+{
+	struct tkip_ctx *ctx = crypto->priv;
+	struct ieee80211_frame *hdr = iob->data;
+	struct io_buffer *eiob;
+	struct arc4_ctx arc4;
+	u8 key[16];
+	struct tkip_head head;
+	u8 mic[8];
+	u32 icv;
+	const int hdrlen = IEEE80211_TYP_FRAME_HEADER_LEN;
+	int datalen = iob_len ( iob ) - hdrlen;
+
+	ctx->enc.tsc_lo++;
+	if ( ctx->enc.tsc_lo == 0 ) {
+		ctx->enc.tsc_hi++;
+		ctx->enc.ttak_ok = 0;
+	}
+
+	tkip_mix_1 ( &ctx->enc, &ctx->tk, hdr->addr2 );
+	tkip_mix_2 ( &ctx->enc, &ctx->tk, key );
+
+	eiob = alloc_iob ( iob_len ( iob ) + TKIP_HEAD_LEN + TKIP_FOOT_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 IV and key ID byte, and extended IV */
+	memcpy ( &head, key, 3 );
+	head.kid = 0x20;		/* have Extended IV, key ID 0 */
+	head.tsc_hi = cpu_to_le32 ( ctx->enc.tsc_hi );
+	memcpy ( iob_put ( eiob, sizeof ( head ) ), &head, sizeof ( head ) );
+
+	/* Copy and encrypt the data */
+	cipher_setkey ( &arc4_algorithm, &arc4, key, 16 );
+	cipher_encrypt ( &arc4_algorithm, &arc4, iob->data + hdrlen,
+			 iob_put ( eiob, datalen ), datalen );
+
+	/* Add MIC */
+	hdr = iob->data;
+	tkip_michael ( &ctx->tk.mic.tx, hdr->addr3, hdr->addr2,
+		       iob->data + hdrlen, datalen, mic );
+	cipher_encrypt ( &arc4_algorithm, &arc4, mic,
+			 iob_put ( eiob, sizeof ( mic ) ), sizeof ( mic ) );
+
+	/* Add ICV */
+	icv = crc32_le ( ~0, iob->data + hdrlen, datalen );
+	icv = crc32_le ( icv, mic, sizeof ( mic ) );
+	icv = cpu_to_le32 ( ~icv );
+	cipher_encrypt ( &arc4_algorithm, &arc4, &icv,
+			 iob_put ( eiob, TKIP_ICV_LEN ), TKIP_ICV_LEN );
+
+	DBGC2 ( ctx, "WPA-TKIP %p: encrypted packet %p -> %p\n", ctx,
+		iob, eiob );
+
+	return eiob;
+}
+
+/**
+ * Decrypt a packet using TKIP
+ *
+ * @v crypto	TKIP cryptosystem
+ * @v eiob	I/O buffer containing encrypted packet
+ * @ret iob	I/O buffer containing cleartext packet
+ */
+static struct io_buffer * tkip_decrypt ( struct net80211_crypto *crypto,
+					 struct io_buffer *eiob )
+{
+	struct tkip_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 - TKIP_HEAD_LEN - TKIP_FOOT_LEN;
+	struct tkip_head *head;
+	struct arc4_ctx arc4;
+	u16 rx_tsc_lo;
+	u8 key[16];
+	u8 mic[8];
+	u32 icv, crc;
+
+	iob = alloc_iob ( hdrlen + datalen + TKIP_FOOT_LEN );
+	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 TSC */
+	head = eiob->data + hdrlen;
+	rx_tsc_lo = ( head->tsc1 << 8 ) | head->tsc0;
+
+	if ( head->tsc_hi < ctx->dec.tsc_hi ||
+	     ( head->tsc_hi == ctx->dec.tsc_hi &&
+	       rx_tsc_lo <= ctx->dec.tsc_lo ) ) {
+		DBGC ( ctx, "WPA-TKIP %p: packet received out of order "
+		       "(%08x:%04x <= %08x:%04x)\n", ctx, head->tsc_hi,
+		       rx_tsc_lo, ctx->dec.tsc_hi, ctx->dec.tsc_lo );
+		free_iob ( iob );
+		return NULL;
+	}
+	ctx->dec.tsc_lo = rx_tsc_lo;
+	if ( ctx->dec.tsc_hi != head->tsc_hi ) {
+		ctx->dec.ttak_ok = 0;
+		ctx->dec.tsc_hi = head->tsc_hi;
+	}
+
+	/* Calculate key */
+	tkip_mix_1 ( &ctx->dec, &ctx->tk, hdr->addr2 );
+	tkip_mix_2 ( &ctx->dec, &ctx->tk, key );
+
+	/* Copy-decrypt data, MIC, ICV */
+	cipher_setkey ( &arc4_algorithm, &arc4, key, 16 );
+	cipher_decrypt ( &arc4_algorithm, &arc4,
+			 eiob->data + hdrlen + TKIP_HEAD_LEN,
+			 iob_put ( iob, datalen ), datalen + TKIP_FOOT_LEN );
+
+	/* Check ICV */
+	icv = le32_to_cpu ( *( u32 * ) ( iob->tail + TKIP_MIC_LEN ) );
+	crc = ~crc32_le ( ~0, iob->data + hdrlen, datalen + TKIP_MIC_LEN );
+	if ( crc != icv ) {
+		DBGC ( ctx, "WPA-TKIP %p CRC mismatch: expect %08x, get %08x\n",
+		       ctx, icv, crc );
+		free_iob ( iob );
+		return NULL;
+	}
+
+	/* Check MIC */
+	tkip_michael ( &ctx->tk.mic.rx, hdr->addr1, hdr->addr3,
+		       iob->data + hdrlen, datalen, mic );
+	if ( memcmp ( mic, iob->tail, TKIP_MIC_LEN ) != 0 ) {
+		DBGC ( ctx, "WPA-TKIP %p ALERT! MIC failure\n", ctx );
+		/* XXX we should do the countermeasures here */
+		free_iob ( iob );
+		return NULL;
+	}
+
+	DBGC2 ( ctx, "WPA-TKIP %p: decrypted packet %p -> %p\n", ctx,
+		eiob, iob );
+
+	return iob;
+}
+
+/** TKIP cryptosystem */
+struct net80211_crypto tkip_crypto __net80211_crypto = {
+	.algorithm = NET80211_CRYPT_TKIP,
+	.init = tkip_init,
+	.encrypt = tkip_encrypt,
+	.decrypt = tkip_decrypt,
+	.priv_len = sizeof ( struct tkip_ctx ),
+};
+
+
+
+
+/**
+ * Calculate HMAC-MD5 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 tkip_kie_mic ( const void *kck, const void *msg, size_t len,
+			   void *mic )
+{
+	struct md5_ctx md5;
+	u8 kckb[16];
+	size_t kck_len = 16;
+
+	memcpy ( kckb, kck, kck_len );
+
+	hmac_init ( &md5_algorithm, &md5, kckb, &kck_len );
+	hmac_update ( &md5_algorithm, &md5, msg, len );
+	hmac_final ( &md5_algorithm, &md5, kckb, &kck_len, mic );
+}
+
+/**
+ * Decrypt key data in EAPOL-Key frame
+ *
+ * @v kek	Key Encryption Key, 16 bytes
+ * @v iv	Initialisation vector, 16 bytes
+ * @v msg	Message to decrypt
+ * @v len	Length of message
+ * @ret msg	Decrypted message in place of original
+ * @ret len	Unchanged
+ * @ret rc	Always 0 for success
+ */
+static int tkip_kie_decrypt ( const void *kek, const void *iv,
+			      void *msg, u16 *len )
+{
+	u8 key[32];
+	memcpy ( key, iv, 16 );
+	memcpy ( key + 16, kek, 16 );
+
+	arc4_skip ( key, 32, 256, msg, msg, *len );
+
+	return 0;
+}
+
+
+/** TKIP-style key integrity and encryption handler */
+struct wpa_kie tkip_kie __wpa_kie = {
+	.version = EAPOL_KEY_VERSION_WPA,
+	.mic = tkip_kie_mic,
+	.decrypt = tkip_kie_decrypt,
+};