From patchwork Wed Apr 23 14:40:20 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ludovico de Nittis X-Patchwork-Id: 883618 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6913327F75E for ; Wed, 23 Apr 2025 14:41:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745419266; cv=none; b=j0JrMUiLLD1/lJEu1zP8ApmVcygIIgZleHgU1BwYFrDerVHKgvVmxZAE8+bFJcvMGtp7yuq/5Uw5CTKTiWEkKHS8B4tbhYMPLAgttBxeSRH9xTpae6k+F/Vpy/RxcAeJf+pJfmwF1OnnwnsFo/Q0Gjbio+w6xFHhU1431JxbsM4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745419266; c=relaxed/simple; bh=KRMvqAGraYxp/JfLc0lzaBUL/5SN7siwJb6c/xxtkzw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JZ3D1XlbkvxqMkHDBsdHihxmBbelxMVDYGsb63lzFtL6rl+7EW2KoArglL/n9omFC7dbkmZnELDr0zbwtg4xqL4Fl4FndRZDZbqAmsTQ6jKja5XYObMZFowkGDprZ6HJd+owoI7PEtltlsVqRl7uh1VVdhrf5Qz9pFZZw7fW+lk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=MIqnlu+c; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="MIqnlu+c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1745419261; bh=KRMvqAGraYxp/JfLc0lzaBUL/5SN7siwJb6c/xxtkzw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=MIqnlu+cb///TL1QzbVamAWawqk+f/9Ynl2T3R/VkirGgHqcV6xCAaM+fLqa9VOO+ +1OCJj2CTvzue7Y0Salu445bq/q8ozO5W2zvilZmxoeCoJRmIbeT39rHSqcNDy2Otd SMaOt3XQ49Z0By5RvGTDl7fsDkYGtgdHzGGmSCfXP8qrkpImmwf1xNL1vl977MCqwx rCZpftCCOT6mAKCuR0UbPy6VJRkzG8+9GCkkC2qBW+PEyYQngMP9KijyU/75jMEY7V fIVG9ityVU4lYVz4TItIXOitoDAGM22WvsJD6n7Jbd9hVVzXLJxSepCvHIIsB7xQOW 2lbW1i/5ra2rw== Received: from localhost.localdomain (unknown [81.56.51.115]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: denittis) by bali.collaboradmins.com (Postfix) with ESMTPSA id D0B7F17E36BD; Wed, 23 Apr 2025 16:41:00 +0200 (CEST) From: Ludovico de Nittis To: linux-bluetooth@vger.kernel.org Cc: Ludovico de Nittis Subject: [PATCH BlueZ v2 8/8] input: Validate the Sixaxis HID report descriptor Date: Wed, 23 Apr 2025 16:40:20 +0200 Message-ID: <20250423144020.358828-9-ludovico.denittis@collabora.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250423144020.358828-1-ludovico.denittis@collabora.com> References: <20250423144020.358828-1-ludovico.denittis@collabora.com> Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Given that the Sixaxis devices can't work with encryption, i.e. they only work with BT_IO_SEC_LOW, this makes it harder to notice if the device we are talking to is the expected Sixaxis gamepad or an impostor. To reduce the possible attack surface, we ensure that the report descriptor that the device provided resembles what a real Sixaxis gamepad should have. E.g. it should only have Usages for `Joystick`, `Pointer` etc... and nothing unexpected like `Keyboard`. --- profiles/input/device.c | 71 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) diff --git a/profiles/input/device.c b/profiles/input/device.c index 9f05757a6..6f538759b 100644 --- a/profiles/input/device.c +++ b/profiles/input/device.c @@ -1062,9 +1062,72 @@ static gboolean encrypt_notify(GIOChannel *io, GIOCondition condition, return FALSE; } +static bool validate_sixaxis_rd_data(const uint8_t *rd_data, uint16_t rd_size) +{ + uint16_t i; + size_t data_size = 0; + + for (i = 0; i < rd_size; i += 1 + data_size) { + uint8_t b = rd_data[i]; + + /* Long items are reserved for future use, HID 1.11 Section 6.2.2.3 */ + if (b == 0xFE) { + DBG("The sixaxis HID report descriptor has an unexpected long item"); + return false; + } + + /* Extract data following the HID 1.11 Section 6.2.2.2 */ + uint8_t bSize = b & 0x03; + uint8_t bType = (b >> 2) & 0x03; + uint8_t bTag = (b >> 4) & 0x0F; + data_size = bSize == 3 ? 4 : bSize; + + if ((i + 1 + data_size) > rd_size) + break; + + const uint8_t *data = &rd_data[i + 1]; + + if (bType == 1 && bTag == 0x0 && data_size >= 1) { + /* Usage Page (Generic Desktop) */ + if (data_size == 1 && data[0] == 0x01) + continue; + + /* Usage Page (Button) */ + if (data_size == 1 && data[0] == 0x09) + continue; + + /* Usage Page (Vendor Defined Page 1) */ + if (data_size == 2 && data[0] == 0x00 && data[1] == 0xFF) + continue; + + DBG("The sixaxis HID report descriptor has an unexpected Usage Page: 0x%02X", data[0]); + return false; + } + + if (bType == 2 && bTag == 0x0 && data_size >= 1) { + /* Usage (Joystick) */ + if (data_size == 1 && data[0] == 0x04) + continue; + + /* Usage (Pointer) */ + if (data_size == 1 && data[0] == 0x01) + continue; + + /* Axis usages, e.g. Usage (X) */ + if (data_size == 1 && data[0] >= 0x30 && data[0] <= 0x35) + continue; + + DBG("The sixaxis HID report descriptor has an unexpected Usage: 0x%02X", data[0]); + return false; + } + } + return true; +} + static int hidp_add_connection(struct input_device *idev) { struct hidp_connadd_req *req; + bool sixaxis_cable_pairing; GError *gerr = NULL; int err; @@ -1090,6 +1153,14 @@ static int hidp_add_connection(struct input_device *idev) sixaxis_cable_pairing = device_is_sixaxis_cable_pairing(idev->device); + /* The Sixaxis devices must use the security level BT_IO_SEC_LOW to work. */ + /* We reduce the attack surface by ensuring that the report descriptor only */ + /* contains the expected Usages that a real Sixaxis gamepad has */ + if (sixaxis_cable_pairing && !validate_sixaxis_rd_data(req->rd_data, req->rd_size)) { + error("The sixaxis HID SDP record has unexpected entries, rejecting the connection to %s", idev->path); + goto cleanup; + } + /* Make sure the device is bonded if required */ if (!sixaxis_cable_pairing && classic_bonded_only && !input_device_bonded(idev)) { error("Rejected connection from !bonded device %s", idev->path);