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-rw-r--r--gpxe/src/net/80211/wpa_ccmp.c528
1 files changed, 528 insertions, 0 deletions
diff --git a/gpxe/src/net/80211/wpa_ccmp.c b/gpxe/src/net/80211/wpa_ccmp.c
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+/*
+ * 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,
+};