Re: [PATCH] mac80211: Scale down to non-HT association with TKIP/WEP as pairwise cipher

[Johannes Berg <johannes@sipsolutions.net>]

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On Tue, 2008-12-23 at 21:30 +0530, Vasanthakumar Thiagarajan wrote:
> As TKIP is not updated to new security needs which arise when
> TKIP is used to encrypt A-MPDU aggregated data frames, IEEE802.11n
> does not allow any cipher other than CCMP (Which has new extensions
> defined) as pairwise cipher between HT peers.
> 
> When such configuration (TKIP/WEP in HT) is forced, we still
> associate in non-HT mode (11a/b/g).
> 
> Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>

Ok, we'll revisit this when we do normal key config in cfg80211, until
then this looks good to me.

Acked-by: Johannes Berg <johannes@sipsolutions.net>

> ---
>  net/mac80211/ieee80211_i.h |    1 +
>  net/mac80211/iface.c       |    3 ++-
>  net/mac80211/mlme.c        |    9 ++++++++-
>  net/mac80211/wext.c        |   12 +++++++++++-
>  4 files changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
> index f3eec98..5f8ad88 100644
> --- a/net/mac80211/ieee80211_i.h
> +++ b/net/mac80211/ieee80211_i.h
> @@ -258,6 +258,7 @@ struct mesh_preq_queue {
>  #define IEEE80211_STA_AUTO_BSSID_SEL	BIT(11)
>  #define IEEE80211_STA_AUTO_CHANNEL_SEL	BIT(12)
>  #define IEEE80211_STA_PRIVACY_INVOKED	BIT(13)
> +#define IEEE80211_STA_TKIP_WEP_USED	BIT(14)
>  /* flags for MLME request */
>  #define IEEE80211_STA_REQ_SCAN 0
>  #define IEEE80211_STA_REQ_DIRECT_PROBE 1
> diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
> index 5abbc3f..19cfc0a 100644
> --- a/net/mac80211/iface.c
> +++ b/net/mac80211/iface.c
> @@ -459,7 +459,8 @@ static int ieee80211_stop(struct net_device *dev)
>  		synchronize_rcu();
>  		skb_queue_purge(&sdata->u.sta.skb_queue);
>  
> -		sdata->u.sta.flags &= ~IEEE80211_STA_PRIVACY_INVOKED;
> +		sdata->u.sta.flags &= ~(IEEE80211_STA_PRIVACY_INVOKED |
> +					IEEE80211_STA_TKIP_WEP_USED);
>  		kfree(sdata->u.sta.extra_ie);
>  		sdata->u.sta.extra_ie = NULL;
>  		sdata->u.sta.extra_ie_len = 0;
> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> index c75d0ea..4998dc5 100644
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -391,10 +391,17 @@ static void ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata,
>  	}
>  
>  	/* wmm support is a must to HT */
> +	/*
> +	 * IEEE802.11n does not allow TKIP/WEP as pairwise
> +	 * ciphers in HT mode. We still associate in non-ht
> +	 * mode (11a/b/g) if any one of these ciphers is
> +	 * configured as pairwise.
> +	 */
>  	if (wmm && (ifsta->flags & IEEE80211_STA_WMM_ENABLED) &&
>  	    sband->ht_cap.ht_supported &&
>  	    (ht_ie = ieee80211_bss_get_ie(bss, WLAN_EID_HT_INFORMATION)) &&
> -	    ht_ie[1] >= sizeof(struct ieee80211_ht_info)) {
> +	    ht_ie[1] >= sizeof(struct ieee80211_ht_info) &&
> +	    (!(ifsta->flags & IEEE80211_STA_TKIP_WEP_USED))) {
>  		struct ieee80211_ht_info *ht_info =
>  			(struct ieee80211_ht_info *)(ht_ie + 2);
>  		u16 cap = sband->ht_cap.cap;
> diff --git a/net/mac80211/wext.c b/net/mac80211/wext.c
> index 7162d58..011592f 100644
> --- a/net/mac80211/wext.c
> +++ b/net/mac80211/wext.c
> @@ -903,12 +903,22 @@ static int ieee80211_ioctl_siwauth(struct net_device *dev,
>  
>  	switch (data->flags & IW_AUTH_INDEX) {
>  	case IW_AUTH_WPA_VERSION:
> -	case IW_AUTH_CIPHER_PAIRWISE:
>  	case IW_AUTH_CIPHER_GROUP:
>  	case IW_AUTH_WPA_ENABLED:
>  	case IW_AUTH_RX_UNENCRYPTED_EAPOL:
>  	case IW_AUTH_KEY_MGMT:
>  		break;
> +	case IW_AUTH_CIPHER_PAIRWISE:
> +		if (sdata->vif.type == NL80211_IFTYPE_STATION) {
> +			if (data->value & (IW_AUTH_CIPHER_WEP40 |
> +			    IW_AUTH_CIPHER_WEP104 | IW_AUTH_CIPHER_TKIP))
> +				sdata->u.sta.flags |=
> +					IEEE80211_STA_TKIP_WEP_USED;
> +			else
> +				sdata->u.sta.flags &=
> +					~IEEE80211_STA_TKIP_WEP_USED;
> +		}
> +		break;
>  	case IW_AUTH_DROP_UNENCRYPTED:
>  		sdata->drop_unencrypted = !!data->value;
>  		break;

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