From 2b4d4942980e01a6b33e439ad18f42f5d4b2cb8a Mon Sep 17 00:00:00 2001
From: Marcus Glocker <mglocker@cvs.openbsd.org>
Date: Mon, 15 Feb 2021 11:26:01 +0000
Subject: Back-out USB data toggle fix for HID devices, since we received
 multiple reports about broken devices, e.g. for ukbd(4) and fido(4).

ok mpi@
---
 lib/libfido2/src/hid_openbsd.c | 66 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

(limited to 'lib/libfido2')

diff --git a/lib/libfido2/src/hid_openbsd.c b/lib/libfido2/src/hid_openbsd.c
index 38edc41d4c6..58b8c3e9475 100644
--- a/lib/libfido2/src/hid_openbsd.c
+++ b/lib/libfido2/src/hid_openbsd.c
@@ -88,6 +88,62 @@ fido_hid_manifest(fido_dev_info_t *devlist, size_t ilen, size_t *olen)
 	return FIDO_OK;
 }
 
+/*
+ * Workaround for OpenBSD <=6.6-current (as of 201910) bug that loses
+ * sync of DATA0/DATA1 sequence bit across uhid open/close.
+ * Send pings until we get a response - early pings with incorrect
+ * sequence bits will be ignored as duplicate packets by the device.
+ */
+static int
+terrible_ping_kludge(struct hid_openbsd *ctx)
+{
+	u_char data[256];
+	int i, n;
+	struct pollfd pfd;
+
+	if (sizeof(data) < ctx->report_out_len + 1)
+		return -1;
+	for (i = 0; i < 4; i++) {
+		memset(data, 0, sizeof(data));
+		/* broadcast channel ID */
+		data[1] = 0xff;
+		data[2] = 0xff;
+		data[3] = 0xff;
+		data[4] = 0xff;
+		/* Ping command */
+		data[5] = 0x81;
+		/* One byte ping only, Vasili */
+		data[6] = 0;
+		data[7] = 1;
+		fido_log_debug("%s: send ping %d", __func__, i);
+		if (fido_hid_write(ctx, data, ctx->report_out_len + 1) == -1)
+			return -1;
+		fido_log_debug("%s: wait reply", __func__);
+		memset(&pfd, 0, sizeof(pfd));
+		pfd.fd = ctx->fd;
+		pfd.events = POLLIN;
+		if ((n = poll(&pfd, 1, 100)) == -1) {
+			fido_log_debug("%s: poll: %s", __func__, strerror(errno));
+			return -1;
+		} else if (n == 0) {
+			fido_log_debug("%s: timed out", __func__);
+			continue;
+		}
+		if (fido_hid_read(ctx, data, ctx->report_out_len, 250) == -1)
+			return -1;
+		/*
+		 * Ping isn't always supported on the broadcast channel,
+		 * so we might get an error, but we don't care - we're
+		 * synched now.
+		 */
+		fido_log_debug("%s: got reply", __func__);
+		fido_log_xxd(data, ctx->report_out_len);
+		return 0;
+	}
+	fido_log_debug("%s: no response", __func__);
+	return -1;
+}
+
 void *
 fido_hid_open(const char *path)
 {
@@ -102,6 +158,16 @@ fido_hid_open(const char *path)
 	fido_log_debug("%s: inlen = %zu outlen = %zu", __func__,
 	    ret->report_in_len, ret->report_out_len);
 
+	/*
+	 * OpenBSD (as of 201910) has a bug that causes it to lose
+	 * track of the DATA0/DATA1 sequence toggle across uhid device
+	 * open and close. This is a terrible hack to work around it.
+	 */
+	if (terrible_ping_kludge(ret) != 0) {
+		fido_hid_close(ret);
+		return NULL;
+	}
+
 	return (ret);
 }
 
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