wireguard: netlink: use WG_KEY_LEN in policies

When converting the netlink policies to YNL, the constants used
in the policy have to be visible to userspace.

As NOISE_*_KEY_LEN isn't visible to userspace, change the policy
to use WG_KEY_LEN, as also documented in the UAPI header:

$ grep WG_KEY_LEN include/uapi/linux/wireguard.h
 *    WGDEVICE_A_PRIVATE_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
 *    WGDEVICE_A_PUBLIC_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
 *            WGPEER_A_PUBLIC_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
 *            WGPEER_A_PRESHARED_KEY: NLA_EXACT_LEN, len WG_KEY_LEN
 [...]

Add a couple of BUILD_BUG_ON() to ensure that they stay in sync.

No behavioural changes intended.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

Author: Asbjørn Sloth Tønnesen

drivers/net/wireguard/netlink.c

@@ -24,17 +24,17 @@ static const struct nla_policy allowedip_policy[WGALLOWEDIP_A_MAX + 1];
 static const struct nla_policy device_policy[WGDEVICE_A_MAX + 1] = {
 	[WGDEVICE_A_IFINDEX]		= { .type = NLA_U32 },
 	[WGDEVICE_A_IFNAME]		= { .type = NLA_NUL_STRING, .len = IFNAMSIZ - 1 },
-	[WGDEVICE_A_PRIVATE_KEY]	= NLA_POLICY_EXACT_LEN(NOISE_PUBLIC_KEY_LEN),
-	[WGDEVICE_A_PUBLIC_KEY]		= NLA_POLICY_EXACT_LEN(NOISE_PUBLIC_KEY_LEN),
+	[WGDEVICE_A_PRIVATE_KEY]	= NLA_POLICY_EXACT_LEN(WG_KEY_LEN),
+	[WGDEVICE_A_PUBLIC_KEY]		= NLA_POLICY_EXACT_LEN(WG_KEY_LEN),
 	[WGDEVICE_A_FLAGS]		= NLA_POLICY_MASK(NLA_U32, __WGDEVICE_F_ALL),
 	[WGDEVICE_A_LISTEN_PORT]	= { .type = NLA_U16 },
 	[WGDEVICE_A_FWMARK]		= { .type = NLA_U32 },
 	[WGDEVICE_A_PEERS]		= NLA_POLICY_NESTED_ARRAY(peer_policy),
 };
 
 static const struct nla_policy peer_policy[WGPEER_A_MAX + 1] = {
-	[WGPEER_A_PUBLIC_KEY]				= NLA_POLICY_EXACT_LEN(NOISE_PUBLIC_KEY_LEN),
-	[WGPEER_A_PRESHARED_KEY]			= NLA_POLICY_EXACT_LEN(NOISE_SYMMETRIC_KEY_LEN),
+	[WGPEER_A_PUBLIC_KEY]				= NLA_POLICY_EXACT_LEN(WG_KEY_LEN),
+	[WGPEER_A_PRESHARED_KEY]			= NLA_POLICY_EXACT_LEN(WG_KEY_LEN),
 	[WGPEER_A_FLAGS]				= NLA_POLICY_MASK(NLA_U32, __WGPEER_F_ALL),
 	[WGPEER_A_ENDPOINT]				= NLA_POLICY_MIN_LEN(sizeof(struct sockaddr)),
 	[WGPEER_A_PERSISTENT_KEEPALIVE_INTERVAL]	= { .type = NLA_U16 },
@@ -643,6 +643,9 @@ static struct genl_family genl_family __ro_after_init = {
 
 int __init wg_genetlink_init(void)
 {
+	BUILD_BUG_ON(WG_KEY_LEN != NOISE_PUBLIC_KEY_LEN);
+	BUILD_BUG_ON(WG_KEY_LEN != NOISE_SYMMETRIC_KEY_LEN);
+
 	return genl_register_family(&genl_family);
 }