kernel/net/mac80211/key.c, branch linux-5.1.y

mac80211: Honor SW_CRYPTO_CONTROL for unicast keys in AP VLAN mode

2019-04-09T11:40:32Z

Restore SW_CRYPTO_CONTROL operation on AP_VLAN interfaces for unicast keys, the original override was intended to be done for group keys as those are treated specially by mac80211 and would always have been rejected. Now the situation is that AP_VLAN support must be enabled by the driver if it can support it (meaning it can support software crypto GTK TX). Thus, also simplify the code - if we get here with AP_VLAN and non- pairwise key, software crypto must be used (driver doesn't know about the interface) and can be used (driver must've advertised AP_VLAN if it also uses SW_CRYPTO_CONTROL). Fixes: db3bdcb9c3ff ("mac80211: allow AP_VLAN operation on crypto controlled devices") Signed-off-by: Alexander Wetzel [rewrite commit message] Signed-off-by: Johannes Berg

mac80211: remove unnecessary NULL check

2018-09-05T08:15:48Z

Both old and new cannot be NULL at the same time, hence checking new when old is not NULL is unnecessary. Also, notice that new is being dereferenced before it is checked: idx = new->conf.keyidx; The above triggers a static code analysis warning. Address this by removing the NULL check on new and adding a code comment based on the following piece of code: 387 /* caller must provide at least one old/new */ 388 if (WARN_ON(!new && !old)) 389 return 0; Addresses-Coverity-ID: 1473176 ("Dereference before null check") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Johannes Berg

mac80211: Fix PTK rekey freezes and clear text leak

2018-09-05T08:03:17Z

Rekeying PTK keys without "Extended Key ID for Individually Addressed Frames" did use a procedure not suitable to replace in-use keys and could caused the following issues: 1) Freeze caused by incoming frames: If the local STA installed the key prior to the remote STA we still had the old key active in the hardware when mac80211 switched over to the new key. Therefore there was a window where the card could hand over frames decoded with the old key to mac80211 and bump the new PN (IV) value to an incorrect high number. When it happened the local replay detection silently started to drop all frames sent with the new key. 2) Freeze caused by outgoing frames: If mac80211 was providing the PN (IV) and handed over a clear text frame for encryption to the hardware prior to a key change the driver/card could have processed the queued frame after switching to the new key. This bumped the PN value on the remote STA to an incorrect high number, tricking the remote STA to discard all frames we sent later. 3) Freeze caused by RX aggregation reorder buffer: An aggregation session started with the old key and ending after the switch to the new key also bumped the PN to an incorrect high number, freezing the connection quite similar to 1). 4) Freeze caused by repeating lost frames in an aggregation session: A driver could repeat a lost frame and encrypt it with the new key while in a TX aggregation session without updating the PN for the new key. This also could freeze connections similar to 2). 5) Clear text leak: Removing encryption offload from the card cleared the encryption offload flag only after the card had deleted the key and we did not stop TX during the rekey. The driver/card could therefore get unencrypted frames from mac80211 while no longer be instructed to encrypt them. To prevent those issues the key install logic has been changed: - Mac80211 divers known to be able to rekey PTK0 keys have to set @NL80211_EXT_FEATURE_CAN_REPLACE_PTK0, - mac80211 stops queuing frames depending on the key during the replace - the key is first replaced in the hardware and after that in mac80211 - and mac80211 stops/blocks new aggregation sessions during the rekey. For drivers not setting @NL80211_EXT_FEATURE_CAN_REPLACE_PTK0 the user space must avoid PTK rekeys if "Extended Key ID for Individually Addressed Frames" is not being used. Rekeys for mac80211 drivers without this flag will generate a warning and use an extra call to ieee80211_flush_queues() to both highlight and try to prevent the issues with not updated drivers. The core of the fix changes the key install procedure from: - atomic switch over to the new key in mac80211 - remove the old key in the hardware (stops encryption offloading, fall back to software encryption with a potential clear text packet leak in between) - delete the inactive old key in mac80211 - enable hardware encryption offloading for the new key to: - if it's a PTK mark the old key as tainted to drop TX frames with the outgoing key - replace the key in hardware with the new one - atomic switch over to the new (not marked as tainted) key in mac80211 (which also resumes TX) - delete the inactive old key in mac80211 With the new sequence the hardware will be unable to decrypt frames encrypted with the old key prior to switching to the new key in mac80211 and thus prevent PNs from packets decrypted with the old key to be accounted against the new key. For that to work the drivers have to provide a clear boundary. Mac80211 drivers setting @NL80211_EXT_FEATURE_CAN_REPLACE_PTK0 confirm to provide it and mac80211 will then be able to correctly rekey in-use PTK keys with those drivers. The mac80211 requirements for drivers to set the flag have been added to the "Hardware crypto acceleration" documentation section. It drills down to: The drivers must not hand over frames decrypted with the old key to mac80211 once the call to set_key() with %DISABLE_KEY has been completed. It's allowed to either drop or continue to use the old key for any outgoing frames which are already in the queues, but it must not send out any of them unencrypted or encrypted with the new key. Even with the new boundary in place aggregation sessions with the reorder buffer are problematic: RX aggregation session started prior and completed after the rekey could still dump frames received with the old key at mac80211 after it switched over to the new key. This is side stepped by stopping all (RX and TX) aggregation sessions when replacing a PTK key and hardware key offloading. Stopping TX aggregation sessions avoids the need to get the PNs (IVs) updated in frames prepared for the old key and (re)transmitted after the switch to the new key. As a bonus it improves the compatibility when the remote STA is not handling rekeys as it should. When using software crypto aggregation sessions are not stopped. Mac80211 won't be able to decode the dangerous frames and discard them without special handling. Signed-off-by: Alexander Wetzel [trim overly long rekey warning] Signed-off-by: Johannes Berg

mac80211: restrict delayed tailroom needed decrement

2018-07-24T07:21:12Z

As explained in ieee80211_delayed_tailroom_dec(), during roam, keys of the old AP will be destroyed and new keys will be installed. Deletion of the old key causes crypto_tx_tailroom_needed_cnt to go from 1 to 0 and the new key installation causes a transition from 0 to 1. Whenever crypto_tx_tailroom_needed_cnt transitions from 0 to 1, we invoke synchronize_net(); the reason for doing this is to avoid a race in the TX path as explained in increment_tailroom_need_count(). This synchronize_net() operation can be slow and can affect the station roam time. To avoid this, decrementing the crypto_tx_tailroom_needed_cnt is delayed for a while so that upon installation of new key the transition would be from 1 to 2 instead of 0 to 1 and thereby improving the roam time. This is all correct for a STA iftype, but deferring the tailroom_needed decrement for other iftypes may be unnecessary. For example, let's consider the case of a 4-addr client connecting to an AP for which AP_VLAN interface is also created, let the initial value for tailroom_needed on the AP be 1. * 4-addr client connects to the AP (AP: tailroom_needed = 1) * AP will clear old keys, delay decrement of tailroom_needed count * AP_VLAN is created, it takes the tailroom count from master (AP_VLAN: tailroom_needed = 1, AP: tailroom_needed = 1) * Install new key for the station, assume key is plumbed in the HW, there won't be any change in tailroom_needed count on AP iface * Delayed decrement of tailroom_needed count on AP (AP: tailroom_needed = 0, AP_VLAN: tailroom_needed = 1) Because of the delayed decrement on AP iface, tailroom_needed count goes out of sync between AP(master iface) and AP_VLAN(slave iface) and there would be unnecessary tailroom created for the packets going through AP_VLAN iface. Also, WARN_ONs were observed while trying to bring down the AP_VLAN interface: (warn_slowpath_common) (warn_slowpath_null+0x18/0x20) (warn_slowpath_null) (ieee80211_free_keys+0x114/0x1e4) (ieee80211_free_keys) (ieee80211_del_virtual_monitor+0x51c/0x850) (ieee80211_del_virtual_monitor) (ieee80211_stop+0x30/0x3c) (ieee80211_stop) (__dev_close_many+0x94/0xb8) (__dev_close_many) (dev_close_many+0x5c/0xc8) Restricting delayed decrement to station interface alone fixes the problem and it makes sense to do so because delayed decrement is done to improve roam time which is applicable only for client devices. Signed-off-by: Manikanta Pubbisetty Signed-off-by: Johannes Berg

mac80211: allow AP_VLAN operation on crypto controlled devices

2018-03-29T09:35:22Z

In the current implementation, mac80211 advertises the support of AP_VLANs based on the driver's support for AP mode; it also blocks encrypted AP_VLAN operation on devices advertising SW_CRYPTO_CONTROL. The implementation seems weird in it's current form and could be often confusing, this is because there can be drivers advertising both SW_CRYPTO_CONTROL and AP mode support (ex: ath10k) in which case AP_VLAN will still be supported but only in open BSS and not in secured BSS. When SW_CRYPTO_CONTROL is enabled, it makes more sense if the decision to support AP_VLANs is left to the driver. Mac80211 can then allow AP_VLAN operations depending on the driver support. Signed-off-by: Manikanta Pubbisetty Signed-off-by: Johannes Berg

mac80211: Add MIC space only for TX key option

2017-12-11T11:20:17Z

Add a key flag to indicates that the device only needs MIC space and not a real MIC. In such cases, keep the MIC zeroed for ease of debug. Signed-off-by: David Spinadel Signed-off-by: Luca Coelho Signed-off-by: Johannes Berg

mac80211: don't compare TKIP TX MIC key in reinstall prevention

2017-10-25T09:04:45Z

For the reinstall prevention, the code I had added compares the whole key. It turns out though that iwlwifi firmware doesn't provide the TKIP TX MIC key as it's not needed in client mode, and thus the comparison will always return false. For client mode, thus always zero out the TX MIC key part before doing the comparison in order to avoid accepting the reinstall of the key with identical encryption and RX MIC key, but not the same TX MIC key (since the supplicant provides the real one.) Fixes: fdf7cb4185b6 ("mac80211: accept key reinstall without changing anything") Signed-off-by: Johannes Berg

mac80211: use constant time comparison with keys

2017-10-18T07:39:14Z

Otherwise we risk leaking information via timing side channel. Fixes: fdf7cb4185b6 ("mac80211: accept key reinstall without changing anything") Signed-off-by: Jason A. Donenfeld Signed-off-by: Johannes Berg

mac80211: accept key reinstall without changing anything

2017-10-16T11:02:03Z

When a key is reinstalled we can reset the replay counters etc. which can lead to nonce reuse and/or replay detection being impossible, breaking security properties, as described in the "KRACK attacks". In particular, CVE-2017-13080 applies to GTK rekeying that happened in firmware while the host is in D3, with the second part of the attack being done after the host wakes up. In this case, the wpa_supplicant mitigation isn't sufficient since wpa_supplicant doesn't know the GTK material. In case this happens, simply silently accept the new key coming from userspace but don't take any action on it since it's the same key; this keeps the PN replay counters intact. Signed-off-by: Johannes Berg

mac80211: don't call drv_set_default_unicast_key() for VLANs

2016-12-13T14:57:59Z

Since drivers know nothing about AP_VLAN interfaces, trying to call drv_set_default_unicast_key() just results in a warning and no call to the driver. Avoid the warning by not calling the driver for this on AP_VLAN interfaces. This means that drivers that somehow need this call for AP mode will fail to work properly in the presence of VLAN interfaces, but the current drivers don't seem to use it, and mac80211 will select and indicate the key - so drivers should be OK now. Reported-by: Jouni Malinen Signed-off-by: Johannes Berg