Module Name: src
Committed By: riastradh
Date: Thu Aug 20 21:31:37 UTC 2020
Modified Files:
src/sys/net: if_wg.c
Log Message:
Implement sliding window for wireguard replay detection.
To generate a diff of this commit:
cvs rdiff -u -r1.5 -r1.6 src/sys/net/if_wg.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/net/if_wg.c
diff -u src/sys/net/if_wg.c:1.5 src/sys/net/if_wg.c:1.6
--- src/sys/net/if_wg.c:1.5 Thu Aug 20 21:31:16 2020
+++ src/sys/net/if_wg.c Thu Aug 20 21:31:36 2020
@@ -1,4 +1,4 @@
-/* $NetBSD: if_wg.c,v 1.5 2020/08/20 21:31:16 riastradh Exp $ */
+/* $NetBSD: if_wg.c,v 1.6 2020/08/20 21:31:36 riastradh Exp $ */
/*
* Copyright (C) Ryota Ozaki <[email protected]>
@@ -43,7 +43,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_wg.c,v 1.5 2020/08/20 21:31:16 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wg.c,v 1.6 2020/08/20 21:31:36 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_inet.h"
@@ -337,6 +337,82 @@ struct wg_msg_cookie {
#define WG_MSG_TYPE_DATA 4
#define WG_MSG_TYPE_MAX WG_MSG_TYPE_DATA
+/* Sliding windows */
+
+#define SLIWIN_BITS 2048u
+#define SLIWIN_TYPE uint32_t
+#define SLIWIN_BPW NBBY*sizeof(SLIWIN_TYPE)
+#define SLIWIN_WORDS howmany(SLIWIN_BITS, SLIWIN_BPW)
+#define SLIWIN_NPKT (SLIWIN_BITS - NBBY*sizeof(SLIWIN_TYPE))
+
+struct sliwin {
+ SLIWIN_TYPE B[SLIWIN_WORDS];
+ uint64_t T;
+};
+
+static void
+sliwin_reset(struct sliwin *W)
+{
+
+ memset(W, 0, sizeof(*W));
+}
+
+static int
+sliwin_check_fast(const volatile struct sliwin *W, uint64_t S)
+{
+
+ /*
+ * If it's more than one window older than the highest sequence
+ * number we've seen, reject.
+ */
+ if (S + SLIWIN_NPKT < atomic_load_relaxed(&W->T))
+ return EAUTH;
+
+ /*
+ * Otherwise, we need to take the lock to decide, so don't
+ * reject just yet. Caller must serialize a call to
+ * sliwin_update in this case.
+ */
+ return 0;
+}
+
+static int
+sliwin_update(struct sliwin *W, uint64_t S)
+{
+ unsigned word, bit;
+
+ /*
+ * If it's more than one window older than the highest sequence
+ * number we've seen, reject.
+ */
+ if (S + SLIWIN_NPKT < W->T)
+ return EAUTH;
+
+ /*
+ * If it's higher than the highest sequence number we've seen,
+ * advance the window.
+ */
+ if (S > W->T) {
+ uint64_t i = W->T / SLIWIN_BPW;
+ uint64_t j = S / SLIWIN_BPW;
+ unsigned k;
+
+ for (k = 0; k < MIN(j - i, SLIWIN_WORDS); k++)
+ W->B[(i + k + 1) % SLIWIN_WORDS] = 0;
+ atomic_store_relaxed(&W->T, S);
+ }
+
+ /* Test and set the bit -- if already set, reject. */
+ word = (S / SLIWIN_BPW) % SLIWIN_WORDS;
+ bit = S % SLIWIN_BPW;
+ if (W->B[word] & (1UL << bit))
+ return EAUTH;
+ W->B[word] |= 1UL << bit;
+
+ /* Accept! */
+ return 0;
+}
+
struct wg_worker {
kmutex_t wgw_lock;
kcondvar_t wgw_cv;
@@ -370,8 +446,11 @@ struct wg_session {
uint32_t wgs_receiver_index;
volatile uint64_t
wgs_send_counter;
- volatile uint64_t
- wgs_recv_counter;
+
+ struct {
+ kmutex_t lock;
+ struct sliwin window;
+ } *wgs_recvwin;
uint8_t wgs_handshake_hash[WG_HASH_LEN];
uint8_t wgs_chaining_key[WG_CHAINING_KEY_LEN];
@@ -1942,7 +2021,7 @@ wg_clear_states(struct wg_session *wgs)
{
wgs->wgs_send_counter = 0;
- wgs->wgs_recv_counter = 0;
+ sliwin_reset(&wgs->wgs_recvwin->window);
#define wgs_clear(v) explicit_memset(wgs->wgs_##v, 0, sizeof(wgs->wgs_##v))
wgs_clear(handshake_hash);
@@ -2231,6 +2310,15 @@ wg_handle_msg_data(struct wg_softc *wg,
}
wgp = wgs->wgs_peer;
+ error = sliwin_check_fast(&wgs->wgs_recvwin->window,
+ wgmd->wgmd_counter);
+ if (error) {
+ WG_LOG_RATECHECK(&wgp->wgp_ppsratecheck, LOG_DEBUG,
+ "out-of-window packet: %"PRIu64"\n",
+ wgmd->wgmd_counter);
+ goto out;
+ }
+
mlen = m_length(m);
encrypted_len = mlen - sizeof(*wgmd);
@@ -2281,17 +2369,17 @@ wg_handle_msg_data(struct wg_softc *wg,
}
WG_DLOG("outsize=%u\n", (u_int)decrypted_len);
- /* TODO deal with reordering with a sliding window */
- if (wgs->wgs_recv_counter != 0 &&
- wgmd->wgmd_counter <= wgs->wgs_recv_counter) {
+ mutex_enter(&wgs->wgs_recvwin->lock);
+ error = sliwin_update(&wgs->wgs_recvwin->window,
+ wgmd->wgmd_counter);
+ mutex_exit(&wgs->wgs_recvwin->lock);
+ if (error) {
WG_LOG_RATECHECK(&wgp->wgp_ppsratecheck, LOG_DEBUG,
- "wgmd_counter is equal to or smaller than wgs_recv_counter:"
- " %"PRIu64" <= %"PRIu64"\n", wgmd->wgmd_counter,
- wgs->wgs_recv_counter);
+ "replay or out-of-window packet: %"PRIu64"\n",
+ wgmd->wgmd_counter);
m_freem(n);
goto out;
}
- wgs->wgs_recv_counter = wgmd->wgmd_counter;
m_freem(m);
m = NULL;
@@ -3020,11 +3108,16 @@ wg_alloc_peer(struct wg_softc *wg)
wgs->wgs_state = WGS_STATE_UNKNOWN;
psref_target_init(&wgs->wgs_psref, wg_psref_class);
wgs->wgs_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
+ wgs->wgs_recvwin = kmem_zalloc(sizeof(*wgs->wgs_recvwin), KM_SLEEP);
+ mutex_init(&wgs->wgs_recvwin->lock, MUTEX_DEFAULT, IPL_NONE);
+
wgs = wgp->wgp_session_unstable;
wgs->wgs_peer = wgp;
wgs->wgs_state = WGS_STATE_UNKNOWN;
psref_target_init(&wgs->wgs_psref, wg_psref_class);
wgs->wgs_lock = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
+ wgs->wgs_recvwin = kmem_zalloc(sizeof(*wgs->wgs_recvwin), KM_SLEEP);
+ mutex_init(&wgs->wgs_recvwin->lock, MUTEX_DEFAULT, IPL_NONE);
return wgp;
}
@@ -3061,10 +3154,14 @@ wg_destroy_peer(struct wg_peer *wgp)
wgs = wgp->wgp_session_unstable;
psref_target_destroy(&wgs->wgs_psref, wg_psref_class);
mutex_obj_free(wgs->wgs_lock);
+ mutex_destroy(&wgs->wgs_recvwin->lock);
+ kmem_free(wgs->wgs_recvwin, sizeof(*wgs->wgs_recvwin));
kmem_free(wgs, sizeof(*wgs));
wgs = wgp->wgp_session_stable;
psref_target_destroy(&wgs->wgs_psref, wg_psref_class);
mutex_obj_free(wgs->wgs_lock);
+ mutex_destroy(&wgs->wgs_recvwin->lock);
+ kmem_free(wgs->wgs_recvwin, sizeof(*wgs->wgs_recvwin));
kmem_free(wgs, sizeof(*wgs));
psref_target_destroy(&wgp->wgp_endpoint->wgsa_psref, wg_psref_class);
