/* * Copyright (c) 2009 Joshua Oreman . * * 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 #include #include #include #include #include #include #include #include /** @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, };