[PATCH 1/2] wifi: nl80211: force WLAN_AKM_SUITE_SAE in big endian in NL80211_CMD_EXTERNAL_AUTH

[Alexis Lothoré]

User-space supplicant (observed at least on wpa_supplicant) historically
parses the NL80211_ATTR_AKM_SUITES from the NL80211_CMD_EXTERNAL_AUTH
message as big endian _only_ when its value is WLAN_AKM_SUITE_SAE, while
processing anything else in host endian. This behavior makes any driver
relying on SAE external auth to switch AKM suite to big endian if it is
WLAN_AKM_SUITE_SAE. A fix bringing compatibility with both endianness
has been brought into wpa_supplicant, however we must keep compatibility
with older versions, while trying to reduce the occurences of this manual
conversion in wireless drivers.

Add the be32 conversion specifically on WLAN_AKM_SUITE_SAE in nl80211 layer
to keep compatibility with older wpa_supplicant versions.

Suggested-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Alexis Lothoré <alexis.lothore@xxxxxxxxxxx>
---
Only a few minor modifications from Johannes' initial suggestion:
- fixed unbalanced parenthesis
- slightly reworded the inlined documentation
---
 net/wireless/nl80211.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 5f18cbf7cc3d..046ce0513d31 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -20136,9 +20136,26 @@ int cfg80211_external_auth_request(struct net_device *dev,
 	if (!hdr)
 		goto nla_put_failure;
 
+	/* Some historical mistakes in drivers <-> userspace interface (notably
+	 * between drivers and wpa_supplicant) led to a big-endian conversion
+	 * being needed on NL80211_ATTR_AKM_SUITES _only_ when its value is
+	 * WLAN_AKM_SUITE_SAE. This is now fixed on userspace side, but for the
+	 * benefit of older wpa_supplicant versions, send this particular value
+	 * in big-endian. Note that newer wpa_supplicant will also detect this
+	 * particular value in big endian still, so it all continues to work.
+	 */
+	if (params->key_mgmt_suite == WLAN_AKM_SUITE_SAE) {
+		if (nla_put_be32(msg, NL80211_ATTR_AKM_SUITES,
+				 cpu_to_be32(WLAN_AKM_SUITE_SAE)))
+			goto nla_put_failure;
+	} else {
+		if (nla_put_u32(msg, NL80211_ATTR_AKM_SUITES,
+				params->key_mgmt_suite))
+			goto nla_put_failure;
+	}
+
 	if (nla_put_u32(msg, NL80211_ATTR_WIPHY, rdev->wiphy_idx) ||
 	    nla_put_u32(msg, NL80211_ATTR_IFINDEX, dev->ifindex) ||
-	    nla_put_u32(msg, NL80211_ATTR_AKM_SUITES, params->key_mgmt_suite) ||
 	    nla_put_u32(msg, NL80211_ATTR_EXTERNAL_AUTH_ACTION,
 			params->action) ||
 	    nla_put(msg, NL80211_ATTR_BSSID, ETH_ALEN, params->bssid) ||

-- 
2.43.0