/* * lib80211 crypt: host-based CCMP encryption implementation for lib80211 * * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi> * Copyright (c) 2008, John W. Linville <linville@tuxdriver.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. See README and COPYING for * more details. */ #include <linux/kernel.h> #include <linux/err.h> #include <linux/module.h> #include <linux/init.h> #include <linux/slab.h> #include <linux/random.h> #include <linux/skbuff.h> #include <linux/netdevice.h> #include <linux/if_ether.h> #include <linux/if_arp.h> #include <asm/string.h> #include <linux/wireless.h> #include <linux/ieee80211.h> #include <linux/crypto.h> #include <net/lib80211.h> MODULE_AUTHOR("Jouni Malinen"); MODULE_DESCRIPTION("Host AP crypt: CCMP"); MODULE_LICENSE("GPL"); #define AES_BLOCK_LEN 16 #define CCMP_HDR_LEN 8 #define CCMP_MIC_LEN 8 #define CCMP_TK_LEN 16 #define CCMP_PN_LEN 6 struct lib80211_ccmp_data { u8 key[CCMP_TK_LEN]; int key_set; u8 tx_pn[CCMP_PN_LEN]; u8 rx_pn[CCMP_PN_LEN]; u32 dot11RSNAStatsCCMPFormatErrors; u32 dot11RSNAStatsCCMPReplays; u32 dot11RSNAStatsCCMPDecryptErrors; int key_idx; struct crypto_cipher *tfm; /* scratch buffers for virt_to_page() (crypto API) */ u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN], tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN]; u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN]; }; static inline void lib80211_ccmp_aes_encrypt(struct crypto_cipher *tfm, const u8 pt[16], u8 ct[16]) { crypto_cipher_encrypt_one(tfm, ct, pt); } static void *lib80211_ccmp_init(int key_idx) { struct lib80211_ccmp_data *priv; priv = kzalloc(sizeof(*priv), GFP_ATOMIC); if (priv == NULL) goto fail; priv->key_idx = key_idx; priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC); if (IS_ERR(priv->tfm)) { printk(KERN_DEBUG "lib80211_crypt_ccmp: could not allocate " "crypto API aes\n"); priv->tfm = NULL; goto fail; } return priv; fail: if (priv) { if (priv->tfm) crypto_free_cipher(priv->tfm); kfree(priv); } return NULL; } static void lib80211_ccmp_deinit(void *priv) { struct lib80211_ccmp_data *_priv = priv; if (_priv && _priv->tfm) crypto_free_cipher(_priv->tfm); kfree(priv); } static inline void xor_block(u8 * b, u8 * a, size_t len) { int i; for (i = 0; i < len; i++) b[i] ^= a[i]; } static void ccmp_init_blocks(struct crypto_cipher *tfm, struct ieee80211_hdr *hdr, u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0) { u8 *pos, qc = 0; size_t aad_len; int a4_included, qc_included; u8 aad[2 * AES_BLOCK_LEN]; a4_included = ieee80211_has_a4(hdr->frame_control); qc_included = ieee80211_is_data_qos(hdr->frame_control); aad_len = 22; if (a4_included) aad_len += 6; if (qc_included) { pos = (u8 *) & hdr->addr4; if (a4_included) pos += 6; qc = *pos & 0x0f; aad_len += 2; } /* CCM Initial Block: * Flag (Include authentication header, M=3 (8-octet MIC), * L=1 (2-octet Dlen)) * Nonce: 0x00 | A2 | PN * Dlen */ b0[0] = 0x59; b0[1] = qc; memcpy(b0 + 2, hdr->addr2, ETH_ALEN); memcpy(b0 + 8, pn, CCMP_PN_LEN); b0[14] = (dlen >> 8) & 0xff; b0[15] = dlen & 0xff; /* AAD: * FC with bits 4..6 and 11..13 masked to zero; 14 is always one * A1 | A2 | A3 * SC with bits 4..15 (seq#) masked to zero * A4 (if present) * QC (if present) */ pos = (u8 *) hdr; aad[0] = 0; /* aad_len >> 8 */ aad[1] = aad_len & 0xff; aad[2] = pos[0] & 0x8f; aad[3] = pos[1] & 0xc7; memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN); pos = (u8 *) & hdr->seq_ctrl; aad[22] = pos[0] & 0x0f; aad[23] = 0; /* all bits masked */ memset(aad + 24, 0, 8); if (a4_included) memcpy(aad + 24, hdr->addr4, ETH_ALEN); if (qc_included) { aad[a4_included ? 30 : 24] = qc; /* rest of QC masked */ } /* Start with the first block and AAD */ lib80211_ccmp_aes_encrypt(tfm, b0, auth); xor_block(auth, aad, AES_BLOCK_LEN); lib80211_ccmp_aes_encrypt(tfm, auth, auth); xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN); lib80211_ccmp_aes_encrypt(tfm, auth, auth); b0[0] &= 0x07; b0[14] = b0[15] = 0; lib80211_ccmp_aes_encrypt(tfm, b0, s0); } static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len, u8 *aeskey, int keylen, void *priv) { struct lib80211_ccmp_data *key = priv; int i; u8 *pos; if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len) return -1; if (aeskey != NULL && keylen >= CCMP_TK_LEN) memcpy(aeskey, key->key, CCMP_TK_LEN); pos = skb_push(skb, CCMP_HDR_LEN); memmove(pos, pos + CCMP_HDR_LEN, hdr_len); pos += hdr_len; i = CCMP_PN_LEN - 1; while (i >= 0) { key->tx_pn[i]++; if (key->tx_pn[i] != 0) break; i--; } *pos++ = key->tx_pn[5]; *pos++ = key->tx_pn[4]; *pos++ = 0; *pos++ = (key->key_idx << 6) | (1 << 5) /* Ext IV included */ ; *pos++ = key->tx_pn[3]; *pos++ = key->tx_pn[2]; *pos++ = key->tx_pn[1]; *pos++ = key->tx_pn[0]; return CCMP_HDR_LEN; } static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv) { struct lib80211_ccmp_data *key = priv; int data_len, i, blocks, last, len; u8 *pos, *mic; struct ieee80211_hdr *hdr; u8 *b0 = key->tx_b0; u8 *b = key->tx_b; u8 *e = key->tx_e; u8 *s0 = key->tx_s0; if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len) return -1; data_len = skb->len - hdr_len; len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv); if (len < 0) return -1; pos = skb->data + hdr_len + CCMP_HDR_LEN; hdr = (struct ieee80211_hdr *)skb->data; ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0); blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN); last = data_len % AES_BLOCK_LEN; for (i = 1; i <= blocks; i++) { len = (i == blocks && last) ? last : AES_BLOCK_LEN; /* Authentication */ xor_block(b, pos, len); lib80211_ccmp_aes_encrypt(key->tfm, b, b); /* Encryption, with counter */ b0[14] = (i >> 8) & 0xff; b0[15] = i & 0xff; lib80211_ccmp_aes_encrypt(key->tfm, b0, e); xor_block(pos, e, len); pos += len; } mic = skb_put(skb, CCMP_MIC_LEN); for (i = 0; i < CCMP_MIC_LEN; i++) mic[i] = b[i] ^ s0[i]; return 0; } /* * deal with seq counter wrapping correctly. * refer to timer_after() for jiffies wrapping handling */ static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o) { u32 iv32_n, iv16_n; u32 iv32_o, iv16_o; iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3]; iv16_n = (pn_n[4] << 8) | pn_n[5]; iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3]; iv16_o = (pn_o[4] << 8) | pn_o[5]; if ((s32)iv32_n - (s32)iv32_o < 0 || (iv32_n == iv32_o && iv16_n <= iv16_o)) return 1; return 0; } static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv) { struct lib80211_ccmp_data *key = priv; u8 keyidx, *pos; struct ieee80211_hdr *hdr; u8 *b0 = key->rx_b0; u8 *b = key->rx_b; u8 *a = key->rx_a; u8 pn[6]; int i, blocks, last, len; size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN; u8 *mic = skb->data + skb->len - CCMP_MIC_LEN; if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) { key->dot11RSNAStatsCCMPFormatErrors++; return -1; } hdr = (struct ieee80211_hdr *)skb->data; pos = skb->data + hdr_len; keyidx = pos[3]; if (!(keyidx & (1 << 5))) { if (net_ratelimit()) { printk(KERN_DEBUG "CCMP: received packet without ExtIV" " flag from %pM\n", hdr->addr2); } key->dot11RSNAStatsCCMPFormatErrors++; return -2; } keyidx >>= 6; if (key->key_idx != keyidx) { printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame " "keyidx=%d priv=%p\n", key->key_idx, keyidx, priv); return -6; } if (!key->key_set) { if (net_ratelimit()) { printk(KERN_DEBUG "CCMP: received packet from %pM" " with keyid=%d that does not have a configured" " key\n", hdr->addr2, keyidx); } return -3; } pn[0] = pos[7]; pn[1] = pos[6]; pn[2] = pos[5]; pn[3] = pos[4]; pn[4] = pos[1]; pn[5] = pos[0]; pos += 8; if (ccmp_replay_check(pn, key->rx_pn)) { #ifdef CONFIG_LIB80211_DEBUG if (net_ratelimit()) { printk(KERN_DEBUG "CCMP: replay detected: STA=%pM " "previous PN %02x%02x%02x%02x%02x%02x " "received PN %02x%02x%02x%02x%02x%02x\n", hdr->addr2, key->rx_pn[0], key->rx_pn[1], key->rx_pn[2], key->rx_pn[3], key->rx_pn[4], key->rx_pn[5], pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]); } #endif key->dot11RSNAStatsCCMPReplays++; return -4; } ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b); xor_block(mic, b, CCMP_MIC_LEN); blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN); last = data_len % AES_BLOCK_LEN; for (i = 1; i <= blocks; i++) { len = (i == blocks && last) ? last : AES_BLOCK_LEN; /* Decrypt, with counter */ b0[14] = (i >> 8) & 0xff; b0[15] = i & 0xff; lib80211_ccmp_aes_encrypt(key->tfm, b0, b); xor_block(pos, b, len); /* Authentication */ xor_block(a, pos, len); lib80211_ccmp_aes_encrypt(key->tfm, a, a); pos += len; } if (memcmp(mic, a, CCMP_MIC_LEN) != 0) { if (net_ratelimit()) { printk(KERN_DEBUG "CCMP: decrypt failed: STA=" "%pM\n", hdr->addr2); } key->dot11RSNAStatsCCMPDecryptErrors++; return -5; } memcpy(key->rx_pn, pn, CCMP_PN_LEN); /* Remove hdr and MIC */ memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len); skb_pull(skb, CCMP_HDR_LEN); skb_trim(skb, skb->len - CCMP_MIC_LEN); return keyidx; } static int lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv) { struct lib80211_ccmp_data *data = priv; int keyidx; struct crypto_cipher *tfm = data->tfm; keyidx = data->key_idx; memset(data, 0, sizeof(*data)); data->key_idx = keyidx; data->tfm = tfm; if (len == CCMP_TK_LEN) { memcpy(data->key, key, CCMP_TK_LEN); data->key_set = 1; if (seq) { data->rx_pn[0] = seq[5]; data->rx_pn[1] = seq[4]; data->rx_pn[2] = seq[3]; data->rx_pn[3] = seq[2]; data->rx_pn[4] = seq[1]; data->rx_pn[5] = seq[0]; } crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN); } else if (len == 0) data->key_set = 0; else return -1; return 0; } static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv) { struct lib80211_ccmp_data *data = priv; if (len < CCMP_TK_LEN) return -1; if (!data->key_set) return 0; memcpy(key, data->key, CCMP_TK_LEN); if (seq) { seq[0] = data->tx_pn[5]; seq[1] = data->tx_pn[4]; seq[2] = data->tx_pn[3]; seq[3] = data->tx_pn[2]; seq[4] = data->tx_pn[1]; seq[5] = data->tx_pn[0]; } return CCMP_TK_LEN; } static char *lib80211_ccmp_print_stats(char *p, void *priv) { struct lib80211_ccmp_data *ccmp = priv; p += sprintf(p, "key[%d] alg=CCMP key_set=%d " "tx_pn=%02x%02x%02x%02x%02x%02x " "rx_pn=%02x%02x%02x%02x%02x%02x " "format_errors=%d replays=%d decrypt_errors=%d\n", ccmp->key_idx, ccmp->key_set, ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2], ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5], ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2], ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5], ccmp->dot11RSNAStatsCCMPFormatErrors, ccmp->dot11RSNAStatsCCMPReplays, ccmp->dot11RSNAStatsCCMPDecryptErrors); return p; } static struct lib80211_crypto_ops lib80211_crypt_ccmp = { .name = "CCMP", .init = lib80211_ccmp_init, .deinit = lib80211_ccmp_deinit, .build_iv = lib80211_ccmp_hdr, .encrypt_mpdu = lib80211_ccmp_encrypt, .decrypt_mpdu = lib80211_ccmp_decrypt, .encrypt_msdu = NULL, .decrypt_msdu = NULL, .set_key = lib80211_ccmp_set_key, .get_key = lib80211_ccmp_get_key, .print_stats = lib80211_ccmp_print_stats, .extra_mpdu_prefix_len = CCMP_HDR_LEN, .extra_mpdu_postfix_len = CCMP_MIC_LEN, .owner = THIS_MODULE, }; static int __init lib80211_crypto_ccmp_init(void) { return lib80211_register_crypto_ops(&lib80211_crypt_ccmp); } static void __exit lib80211_crypto_ccmp_exit(void) { lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp); } module_init(lib80211_crypto_ccmp_init); module_exit(lib80211_crypto_ccmp_exit);