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mac80211: fix CCMP races
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Since we can process multiple packets at the
same time for different ACs, but the PN is
allocated from a single counter, we need to
use an atomic value there. Use atomic64_t to
make this cheaper on 64-bit platforms, other
platforms will support this through software
emulation, see lib/atomic64.c.

We also need to use an on-stack scratch buf
so that multiple packets won't corrupt each
others scratch buffers.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Johannes Berg authored and John W. Linville committed Jul 8, 2011
1 parent 523b02e commit aba83a0
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Showing 4 changed files with 32 additions and 25 deletions.
14 changes: 8 additions & 6 deletions net/mac80211/cfg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -209,6 +209,7 @@ static int ieee80211_get_key(struct wiphy *wiphy, struct net_device *dev,
u8 seq[6] = {0};
struct key_params params;
struct ieee80211_key *key = NULL;
u64 pn64;
u32 iv32;
u16 iv16;
int err = -ENOENT;
Expand Down Expand Up @@ -256,12 +257,13 @@ static int ieee80211_get_key(struct wiphy *wiphy, struct net_device *dev,
params.seq_len = 6;
break;
case WLAN_CIPHER_SUITE_CCMP:
seq[0] = key->u.ccmp.tx_pn[5];
seq[1] = key->u.ccmp.tx_pn[4];
seq[2] = key->u.ccmp.tx_pn[3];
seq[3] = key->u.ccmp.tx_pn[2];
seq[4] = key->u.ccmp.tx_pn[1];
seq[5] = key->u.ccmp.tx_pn[0];
pn64 = atomic64_read(&key->u.ccmp.tx_pn);
seq[0] = pn64;
seq[1] = pn64 >> 8;
seq[2] = pn64 >> 16;
seq[3] = pn64 >> 24;
seq[4] = pn64 >> 32;
seq[5] = pn64 >> 40;
params.seq = seq;
params.seq_len = 6;
break;
Expand Down
6 changes: 4 additions & 2 deletions net/mac80211/debugfs_key.c
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,7 @@ static ssize_t key_tx_spec_read(struct file *file, char __user *userbuf,
size_t count, loff_t *ppos)
{
const u8 *tpn;
u64 pn;
char buf[20];
int len;
struct ieee80211_key *key = file->private_data;
Expand All @@ -94,9 +95,10 @@ static ssize_t key_tx_spec_read(struct file *file, char __user *userbuf,
key->u.tkip.tx.iv16);
break;
case WLAN_CIPHER_SUITE_CCMP:
tpn = key->u.ccmp.tx_pn;
pn = atomic64_read(&key->u.ccmp.tx_pn);
len = scnprintf(buf, sizeof(buf), "%02x%02x%02x%02x%02x%02x\n",
tpn[0], tpn[1], tpn[2], tpn[3], tpn[4], tpn[5]);
(u8)(pn >> 40), (u8)(pn >> 32), (u8)(pn >> 24),
(u8)(pn >> 16), (u8)(pn >> 8), (u8)pn);
break;
case WLAN_CIPHER_SUITE_AES_CMAC:
tpn = key->u.aes_cmac.tx_pn;
Expand Down
5 changes: 1 addition & 4 deletions net/mac80211/key.h
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,7 @@ struct ieee80211_key {
struct tkip_ctx rx[NUM_RX_DATA_QUEUES];
} tkip;
struct {
u8 tx_pn[6];
atomic64_t tx_pn;
/*
* Last received packet number. The first
* NUM_RX_DATA_QUEUES counters are used with Data
Expand All @@ -92,12 +92,9 @@ struct ieee80211_key {
u8 rx_pn[NUM_RX_DATA_QUEUES + 1][6];
struct crypto_cipher *tfm;
u32 replays; /* dot11RSNAStatsCCMPReplays */
/* scratch buffers for virt_to_page() (crypto API) */
#ifndef AES_BLOCK_LEN
#define AES_BLOCK_LEN 16
#endif
u8 tx_crypto_buf[6 * AES_BLOCK_LEN];
u8 rx_crypto_buf[6 * AES_BLOCK_LEN];
} ccmp;
struct {
u8 tx_pn[6];
Expand Down
32 changes: 19 additions & 13 deletions net/mac80211/wpa.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include <linux/gfp.h>
#include <asm/unaligned.h>
#include <net/mac80211.h>
#include <crypto/aes.h>

#include "ieee80211_i.h"
#include "michael.h"
Expand Down Expand Up @@ -290,6 +291,8 @@ static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
unsigned int hdrlen;
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;

memset(scratch, 0, 6 * AES_BLOCK_LEN);

b_0 = scratch + 3 * AES_BLOCK_LEN;
aad = scratch + 4 * AES_BLOCK_LEN;

Expand Down Expand Up @@ -380,8 +383,10 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
struct ieee80211_key *key = tx->key;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
int hdrlen, len, tail;
u8 *pos, *pn;
int i;
u8 *pos;
u8 pn[6];
u64 pn64;
u8 scratch[6 * AES_BLOCK_LEN];

if (info->control.hw_key &&
!(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
Expand Down Expand Up @@ -409,14 +414,14 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
hdr = (struct ieee80211_hdr *) pos;
pos += hdrlen;

/* PN = PN + 1 */
pn = key->u.ccmp.tx_pn;
pn64 = atomic64_inc_return(&key->u.ccmp.tx_pn);

for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
pn[i]++;
if (pn[i])
break;
}
pn[5] = pn64;
pn[4] = pn64 >> 8;
pn[3] = pn64 >> 16;
pn[2] = pn64 >> 24;
pn[1] = pn64 >> 32;
pn[0] = pn64 >> 40;

ccmp_pn2hdr(pos, pn, key->conf.keyidx);

Expand All @@ -425,8 +430,8 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
return 0;

pos += CCMP_HDR_LEN;
ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
ccmp_special_blocks(skb, pn, scratch, 0);
ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, scratch, pos, len,
pos, skb_put(skb, CCMP_MIC_LEN));

return 0;
Expand Down Expand Up @@ -482,11 +487,12 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
}

if (!(status->flag & RX_FLAG_DECRYPTED)) {
u8 scratch[6 * AES_BLOCK_LEN];
/* hardware didn't decrypt/verify MIC */
ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
ccmp_special_blocks(skb, pn, scratch, 1);

if (ieee80211_aes_ccm_decrypt(
key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
key->u.ccmp.tfm, scratch,
skb->data + hdrlen + CCMP_HDR_LEN, data_len,
skb->data + skb->len - CCMP_MIC_LEN,
skb->data + hdrlen + CCMP_HDR_LEN))
Expand Down

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