From 080d3b14470f6ac59f4cfb97a4200ed18df5c260 Mon Sep 17 00:00:00 2001

From: Fabian Henneke <fabian@henneke.me>

Date: Wed, 21 Aug 2019 11:17:59 +0200

Subject: [PATCH] udev: Add id program and rule for FIDO security tokens

Add a fido_id program meant to be run for devices in the hidraw

subsystem via an IMPORT directive. The program parses the HID report

descriptor and assigns the ID_SECURITY_TOKEN environment variable if a

declared usage matches the FIDO_CTAPHID_USAGE declared in the FIDO CTAP

specification. This replaces the previous approach of whitelisting all

known security token models manually.

This commit is accompanied by a test suite and a fuzzer target for the

descriptor parsing routine.

Fixes: #11996.

(cherry picked from commit d45ee2f31a8358db0accde2e7c81777cedadc3c2)

Resolves: #1753369

---

 rules/60-fido-id.rules              |   7 ++

 rules/meson.build                   |   1 +

 src/fuzz/fuzz-fido-id-desc.c        |  23 +++++++

 src/fuzz/fuzz-fido-id-desc.dict     |   6 ++

 src/fuzz/meson.build                |   4 ++

 src/test/meson.build                |   4 ++

 src/test/test-fido-id-desc.c        |  85 +++++++++++++++++++++++

 src/udev/fido_id/fido_id.c          | 103 ++++++++++++++++++++++++++++

 src/udev/fido_id/fido_id_desc.c     |  92 +++++++++++++++++++++++++

 src/udev/fido_id/fido_id_desc.h     |   8 +++

 src/udev/meson.build                |   3 +

 test/fuzz/fuzz-fido-id-desc/crash0  |   1 +

 test/fuzz/fuzz-fido-id-desc/crash1  |   1 +

 test/fuzz/fuzz-fido-id-desc/report0 | Bin 0 -> 71 bytes

 test/fuzz/fuzz-fido-id-desc/report1 | Bin 0 -> 34 bytes

 15 files changed, 338 insertions(+)

 create mode 100644 rules/60-fido-id.rules

 create mode 100644 src/fuzz/fuzz-fido-id-desc.c

 create mode 100644 src/fuzz/fuzz-fido-id-desc.dict

 create mode 100644 src/test/test-fido-id-desc.c

 create mode 100644 src/udev/fido_id/fido_id.c

 create mode 100644 src/udev/fido_id/fido_id_desc.c

 create mode 100644 src/udev/fido_id/fido_id_desc.h

 create mode 100644 test/fuzz/fuzz-fido-id-desc/crash0

 create mode 100644 test/fuzz/fuzz-fido-id-desc/crash1

 create mode 100644 test/fuzz/fuzz-fido-id-desc/report0

 create mode 100644 test/fuzz/fuzz-fido-id-desc/report1

diff --git a/rules/60-fido-id.rules b/rules/60-fido-id.rules

new file mode 100644

index 0000000000..fcf5079704

--- /dev/null

+++ b/rules/60-fido-id.rules

@@ -0,0 +1,7 @@

+# do not edit this file, it will be overwritten on update

+

+ACTION=="remove", GOTO="fido_id_end"

+

+SUBSYSTEM=="hidraw", IMPORT{program}="fido_id"

+

+LABEL="fido_id_end"

diff --git a/rules/meson.build b/rules/meson.build

index b6aae596b6..6363f8bf2e 100644

--- a/rules/meson.build

+++ b/rules/meson.build

@@ -7,6 +7,7 @@ rules = files('''

         60-cdrom_id.rules

         60-drm.rules

         60-evdev.rules

+        60-fido-id.rules

         60-input-id.rules

         60-persistent-alsa.rules

         60-persistent-input.rules

diff --git a/src/fuzz/fuzz-fido-id-desc.c b/src/fuzz/fuzz-fido-id-desc.c

new file mode 100644

index 0000000000..cf98dee044

--- /dev/null

+++ b/src/fuzz/fuzz-fido-id-desc.c

@@ -0,0 +1,23 @@

+/* SPDX-License-Identifier: LGPL-2.1+ */

+

+#include <linux/hid.h>

+#include <stdbool.h>

+#include <stdint.h>

+#include <stdlib.h>

+

+#include "fido_id/fido_id_desc.h"

+#include "fuzz.h"

+#include "log.h"

+

+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {

+        /* We don't want to fill the logs with messages about parse errors.

+         * Disable most logging if not running standalone */

+        if (!getenv("SYSTEMD_LOG_LEVEL"))

+                log_set_max_level(LOG_CRIT);

+

+        if (size > HID_MAX_DESCRIPTOR_SIZE)

+                return 0;

+        (void) is_fido_security_token_desc(data, size);

+

+        return 0;

+}

diff --git a/src/fuzz/fuzz-fido-id-desc.dict b/src/fuzz/fuzz-fido-id-desc.dict

new file mode 100644

index 0000000000..d2d2679e18

--- /dev/null

+++ b/src/fuzz/fuzz-fido-id-desc.dict

@@ -0,0 +1,6 @@

+"\xfe"

+"\x00"

+"\x01"

+"\xf1"

+"\xd0"

+"\xf1\xd0\x00\x01"

diff --git a/src/fuzz/meson.build b/src/fuzz/meson.build

index 1dbe28e57e..483a952421 100644

--- a/src/fuzz/meson.build

+++ b/src/fuzz/meson.build

@@ -47,4 +47,8 @@ fuzzers += [

          [libsystemd_journal_remote,

           libshared],

          []],

+        [['src/fuzz/fuzz-fido-id-desc.c',

+          'src/udev/fido_id/fido_id_desc.c'],

+         [],

+         []]

 ]

diff --git a/src/test/meson.build b/src/test/meson.build

index 0998f59897..4259421f98 100644

--- a/src/test/meson.build

+++ b/src/test/meson.build

@@ -663,6 +663,10 @@ tests += [

         [['src/test/test-bus-util.c'],

          [],

          []],

+        [['src/test/test-fido-id-desc.c',

+          'src/udev/fido_id/fido_id_desc.c'],

+         [],

+         []],

 ]

 ############################################################

diff --git a/src/test/test-fido-id-desc.c b/src/test/test-fido-id-desc.c

new file mode 100644

index 0000000000..cf55dd3266

--- /dev/null

+++ b/src/test/test-fido-id-desc.c

@@ -0,0 +1,85 @@

+/* SPDX-License-Identifier: LGPL-2.1+ */

+

+#include <stdint.h>

+#include <stdlib.h>

+

+#include "fido_id/fido_id_desc.h"

+#include "macro.h"

+

+static void test_is_fido_security_token_desc__fido(void) {

+        static const uint8_t FIDO_HID_DESC_1[] = {

+                0x06, 0xd0, 0xf1, 0x09, 0x01, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,

+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,

+                0x40, 0x91, 0x02, 0xc0,

+        };

+        assert_se(is_fido_security_token_desc(FIDO_HID_DESC_1, sizeof(FIDO_HID_DESC_1)) > 0);

+

+        static const uint8_t FIDO_HID_DESC_2[] = {

+                0x05, 0x01, 0x09, 0x06, 0xa1, 0x01, 0x05, 0x07, 0x19, 0xe0, 0x29, 0xe7, 0x15, 0x00, 0x25,

+                0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x95, 0x01, 0x75, 0x08, 0x81, 0x01, 0x95, 0x05,

+                0x75, 0x01, 0x05, 0x08, 0x19, 0x01, 0x29, 0x05, 0x91, 0x02, 0x95, 0x01, 0x75, 0x03, 0x91,

+                0x01, 0x95, 0x06, 0x75, 0x08, 0x15, 0x00, 0x25, 0x65, 0x05, 0x07, 0x19, 0x00, 0x29, 0x65,

+                0x81, 0x00, 0x09, 0x03, 0x75, 0x08, 0x95, 0x08, 0xb1, 0x02, 0xc0,

+                0x06, 0xd0, 0xf1, 0x09, 0x01, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,

+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,

+                0x40, 0x91, 0x02, 0xc0,

+        };

+        assert_se(is_fido_security_token_desc(FIDO_HID_DESC_2, sizeof(FIDO_HID_DESC_2)) > 0);

+}

+

+static void test_is_fido_security_token_desc__non_fido(void) {

+        /* Wrong usage page */

+        static const uint8_t NON_FIDO_HID_DESC_1[] = {

+                0x06, 0xd0, 0xf0, 0x09, 0x01, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,

+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,

+                0x40, 0x91, 0x02, 0xc0,

+        };

+        assert_se(is_fido_security_token_desc(NON_FIDO_HID_DESC_1, sizeof(NON_FIDO_HID_DESC_1)) == 0);

+

+        /* Wrong usage */

+        static const uint8_t NON_FIDO_HID_DESC_2[] = {

+                0x06, 0xd0, 0xf1, 0x09, 0x02, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,

+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,

+                0x40, 0x91, 0x02, 0xc0,

+        };

+        assert_se(is_fido_security_token_desc(NON_FIDO_HID_DESC_2, sizeof(NON_FIDO_HID_DESC_2)) == 0);

+

+        static const uint8_t NON_FIDO_HID_DESC_3[] = {

+                0x05, 0x01, 0x09, 0x06, 0xa1, 0x01, 0x05, 0x07, 0x19, 0xe0, 0x29, 0xe7, 0x15, 0x00, 0x25,

+                0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x95, 0x01, 0x75, 0x08, 0x81, 0x01, 0x95, 0x05,

+                0x75, 0x01, 0x05, 0x08, 0x19, 0x01, 0x29, 0x05, 0x91, 0x02, 0x95, 0x01, 0x75, 0x03, 0x91,

+                0x01, 0x95, 0x06, 0x75, 0x08, 0x15, 0x00, 0x25, 0x65, 0x05, 0x07, 0x19, 0x00, 0x29, 0x65,

+                0x81, 0x00, 0x09, 0x03, 0x75, 0x08, 0x95, 0x08, 0xb1, 0x02, 0xc0,

+        };

+        assert_se(is_fido_security_token_desc(NON_FIDO_HID_DESC_3, sizeof(NON_FIDO_HID_DESC_3)) == 0);

+}

+

+static void test_is_fido_security_token_desc__invalid(void) {

+        /* Size coded on 1 byte, but no byte given */

+        static const uint8_t INVALID_HID_DESC_1[] = { 0x01 };

+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_1, sizeof(INVALID_HID_DESC_1)) < 0);

+

+        /* Size coded on 2 bytes, but only 1 byte given */

+        static const uint8_t INVALID_HID_DESC_2[] = { 0x02, 0x01 };

+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_2, sizeof(INVALID_HID_DESC_2)) < 0);

+

+        /* Size coded on 4 bytes, but only 3 bytes given */

+        static const uint8_t INVALID_HID_DESC_3[] = { 0x03, 0x01, 0x02, 0x03 };

+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_3, sizeof(INVALID_HID_DESC_3)) < 0);

+

+        /* Long item without a size byte */

+        static const uint8_t INVALID_HID_DESC_4[] = { 0xfe };

+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_4, sizeof(INVALID_HID_DESC_4)) < 0);

+

+        /* Usage pages are coded on at most 2 bytes */

+        static const uint8_t INVALID_HID_DESC_5[] = { 0x07, 0x01, 0x02, 0x03, 0x04 };

+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_5, sizeof(INVALID_HID_DESC_5)) < 0);

+}

+

+int main(int argc, char *argv[]) {

+        test_is_fido_security_token_desc__fido();

+        test_is_fido_security_token_desc__non_fido();

+        test_is_fido_security_token_desc__invalid();

+

+        return EXIT_SUCCESS;

+}

diff --git a/src/udev/fido_id/fido_id.c b/src/udev/fido_id/fido_id.c

new file mode 100644

index 0000000000..7e1cc804f2

--- /dev/null

+++ b/src/udev/fido_id/fido_id.c

@@ -0,0 +1,103 @@

+/* SPDX-License-Identifier: LGPL-2.1+ */

+/*

+ * Identifies FIDO CTAP1 ("U2F")/CTAP2 security tokens based on the usage declared in their report

+ * descriptor and outputs suitable environment variables.

+ *

+ * Inspired by Andrew Lutomirski's 'u2f-hidraw-policy.c'

+ */

+

+#include <errno.h>

+#include <fcntl.h>

+#include <linux/hid.h>

+#include <stdio.h>

+#include <stdlib.h>

+#include <sys/types.h>

+#include <unistd.h>

+

+#include "sd-device.h"

+

+#include "device-internal.h"

+#include "device-private.h"

+#include "device-util.h"

+#include "fd-util.h"

+#include "fido_id_desc.h"

+#include "log.h"

+#include "macro.h"

+#include "path-util.h"

+#include "string-util.h"

+#include "udev-util.h"

+

+static int run(int argc, char **argv) {

+        _cleanup_(sd_device_unrefp) struct sd_device *device = NULL;

+        _cleanup_free_ char *desc_path = NULL;

+        _cleanup_close_ int fd = -1;

+

+        struct sd_device *hid_device;

+        const char *sys_path;

+        uint8_t desc[HID_MAX_DESCRIPTOR_SIZE];

+        ssize_t desc_len;

+

+        int r;

+

+        log_set_target(LOG_TARGET_AUTO);

+        udev_parse_config();

+        log_parse_environment();

+        log_open();

+

+        if (argc > 2)

+                return log_error_errno(EINVAL, "Usage: %s [SYSFS_PATH]", program_invocation_short_name);

+

+        if (argc == 1) {

+                r = device_new_from_strv(&device, environ);

+                if (r < 0)

+                        return log_error_errno(r, "Failed to get current device from environment: %m");

+        } else {

+                r = sd_device_new_from_syspath(&device, argv[1]);

+                if (r < 0)

+                        return log_error_errno(r, "Failed to get device from syspath: %m");

+        }

+

+        r = sd_device_get_parent(device, &hid_device);

+        if (r < 0)

+                return log_device_error_errno(device, r, "Failed to get parent HID device: %m");

+

+        r = sd_device_get_syspath(hid_device, &sys_path);

+        if (r < 0)

+                return log_device_error_errno(hid_device, r, "Failed to get syspath for HID device: %m");

+

+        desc_path = path_join(NULL, sys_path, "report_descriptor");

+        if (!desc_path)

+                return log_oom();

+

+        fd = open(desc_path, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);

+        if (fd < 0)

+                return log_device_error_errno(hid_device, errno,

+                                              "Failed to open report descriptor at '%s': %m", desc_path);

+

+        desc_len = read(fd, desc, sizeof(desc));

+        if (desc_len < 0)

+                return log_device_error_errno(hid_device, errno,

+                                              "Failed to read report descriptor at '%s': %m", desc_path);

+        if (desc_len == 0)

+                return log_device_debug_errno(hid_device, EINVAL,

+                                              "Empty report descriptor at '%s'.", desc_path);

+

+        r = is_fido_security_token_desc(desc, desc_len);

+        if (r < 0)

+                return log_device_debug_errno(hid_device, r,

+                                              "Failed to parse report descriptor at '%s'.", desc_path);

+        if (r > 0) {

+                printf("ID_FIDO_TOKEN=1\n");

+                printf("ID_SECURITY_TOKEN=1\n");

+        }

+

+        return 0;

+}

+

+int main(int argc, char *argv[]) {

+    int r;

+

+    r = run(argc, argv);

+

+    return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;

+}

diff --git a/src/udev/fido_id/fido_id_desc.c b/src/udev/fido_id/fido_id_desc.c

new file mode 100644

index 0000000000..bbfcf93709

--- /dev/null

+++ b/src/udev/fido_id/fido_id_desc.c

@@ -0,0 +1,92 @@

+/* SPDX-License-Identifier: LGPL-2.1+ */

+/* Inspired by Andrew Lutomirski's 'u2f-hidraw-policy.c' */

+

+#include <errno.h>

+#include <stdbool.h>

+#include <stddef.h>

+#include <stdint.h>

+

+#include "fido_id_desc.h"

+

+#define HID_RPTDESC_FIRST_BYTE_LONG_ITEM 0xfeu

+#define HID_RPTDESC_TYPE_GLOBAL 0x1u

+#define HID_RPTDESC_TYPE_LOCAL 0x2u

+#define HID_RPTDESC_TAG_USAGE_PAGE 0x0u

+#define HID_RPTDESC_TAG_USAGE 0x0u

+

+/*

+ * HID usage for FIDO CTAP1 ("U2F") and CTAP2 security tokens.

+ * https://fidoalliance.org/specs/fido-u2f-v1.0-ps-20141009/fido-u2f-u2f_hid.h-v1.0-ps-20141009.txt

+ * https://fidoalliance.org/specs/fido-v2.0-ps-20190130/fido-client-to-authenticator-protocol-v2.0-ps-20190130.html#usb-discovery

+ * https://www.usb.org/sites/default/files/hutrr48.pdf

+ */

+#define FIDO_FULL_USAGE_CTAPHID 0xf1d00001u

+

+/*

+ * Parses a HID report descriptor and identifies FIDO CTAP1 ("U2F")/CTAP2 security tokens based on their

+ * declared usage.

+ * A positive return value indicates that the report descriptor belongs to a FIDO security token.

+ * https://www.usb.org/sites/default/files/documents/hid1_11.pdf (Section 6.2.2)

+ */

+int is_fido_security_token_desc(const uint8_t *desc, size_t desc_len) {

+        uint32_t usage = 0;

+

+        for (size_t pos = 0; pos < desc_len; ) {

+                uint8_t tag, type, size_code;

+                size_t size;

+                uint32_t value;

+

+                /* Report descriptors consists of short items (1-5 bytes) and long items (3-258 bytes). */

+                if (desc[pos] == HID_RPTDESC_FIRST_BYTE_LONG_ITEM) {

+                        /* No long items are defined in the spec; skip them.

+                         * The length of the data in a long item is contained in the byte after the long

+                         * item tag. The header consists of three bytes: special long item tag, length,

+                         * actual tag. */

+                        if (pos + 1 >= desc_len)

+                                return -EINVAL;

+                        pos += desc[pos + 1] + 3;

+                        continue;

+                }

+

+                /* The first byte of a short item encodes tag, type and size. */

+                tag = desc[pos] >> 4;          /* Bits 7 to 4 */

+                type = (desc[pos] >> 2) & 0x3; /* Bits 3 and 2 */

+                size_code = desc[pos] & 0x3;   /* Bits 1 and 0 */

+                /* Size is coded as follows:

+                 * 0 -> 0 bytes, 1 -> 1 byte, 2 -> 2 bytes, 3 -> 4 bytes

+                 */

+                size = size_code < 3 ? size_code : 4;

+                /* Consume header byte. */

+                pos++;

+

+                /* Extract the item value coded on size bytes. */

+                if (pos + size > desc_len)

+                        return -EINVAL;

+                value = 0;

+                for (size_t i = 0; i < size; i++)

+                        value |= (uint32_t) desc[pos + i] << (8 * i);

+                /* Consume value bytes. */

+                pos += size;

+

+                if (type == HID_RPTDESC_TYPE_GLOBAL && tag == HID_RPTDESC_TAG_USAGE_PAGE) {

+                        /* A usage page is a 16 bit value coded on at most 16 bits. */

+                        if (size > 2)

+                                return -EINVAL;

+                        /* A usage page sets the upper 16 bits of a following usage. */

+                        usage = (value & 0x0000ffffu) << 16;

+                }

+

+                if (type == HID_RPTDESC_TYPE_LOCAL && tag == HID_RPTDESC_TAG_USAGE) {

+                        /* A usage is a 32 bit value, but is prepended with the current usage page if

+                         * coded on less than 4 bytes (that is, at most 2 bytes). */

+                        if (size == 4)

+                                usage = value;

+                        else

+                                usage = (usage & 0xffff0000u) | (value & 0x0000ffffu);

+                        if (usage == FIDO_FULL_USAGE_CTAPHID)

+                                return 1;

+                }

+        }

+

+        return 0;

+}

diff --git a/src/udev/fido_id/fido_id_desc.h b/src/udev/fido_id/fido_id_desc.h

new file mode 100644

index 0000000000..c813a3a454

--- /dev/null

+++ b/src/udev/fido_id/fido_id_desc.h

@@ -0,0 +1,8 @@

+/* SPDX-License-Identifier: LGPL-2.1+ */

+

+#pragma once

+

+#include <stddef.h>

+#include <stdint.h>

+

+int is_fido_security_token_desc(const uint8_t *desc, size_t desc_len);

diff --git a/src/udev/meson.build b/src/udev/meson.build

index 3bcd2bd3d7..5931a6da7d 100644

--- a/src/udev/meson.build

+++ b/src/udev/meson.build

@@ -160,6 +160,9 @@ libudev_core = static_library(

 foreach prog : [['ata_id/ata_id.c'],

                 ['cdrom_id/cdrom_id.c'],

                 ['collect/collect.c'],

+                ['fido_id/fido_id.c',

+                 'fido_id/fido_id_desc.c',

+                 'fido_id/fido_id_desc.h'],

                 ['scsi_id/scsi_id.c',

                  'scsi_id/scsi_id.h',

                  'scsi_id/scsi_serial.c',

diff --git a/test/fuzz/fuzz-fido-id-desc/crash0 b/test/fuzz/fuzz-fido-id-desc/crash0

new file mode 100644

index 0000000000..e066656502

--- /dev/null

+++ b/test/fuzz/fuzz-fido-id-desc/crash0

@@ -0,0 +1 @@

+????Ì?

\ No newline at end of file

diff --git a/test/fuzz/fuzz-fido-id-desc/crash1 b/test/fuzz/fuzz-fido-id-desc/crash1

new file mode 100644

index 0000000000..aef3e18335

--- /dev/null

+++ b/test/fuzz/fuzz-fido-id-desc/crash1

@@ -0,0 +1 @@

+øûøûûÜ

\ No newline at end of file

diff --git a/test/fuzz/fuzz-fido-id-desc/report0 b/test/fuzz/fuzz-fido-id-desc/report0

new file mode 100644

index 0000000000000000000000000000000000000000..48757cba682ffddd5a1ddd8988bb8bcdc7db0a7a

GIT binary patch

literal 71

zcmZQ&<YZgO$jUDHK=ZjMgDPVw<5Z4Drm2jj9F2@qSxXsNIV2f1Sto)-m?tt$Wh>

Xs!9c_XV6S-WZ+~j<(SH`k?8;c6l@Pq

literal 0

HcmV?d00001

diff --git a/test/fuzz/fuzz-fido-id-desc/report1 b/test/fuzz/fuzz-fido-id-desc/report1

new file mode 100644

index 0000000000000000000000000000000000000000..b70b7fb871aeccf4074ccbd20e3cdbaca42e23b3

GIT binary patch

literal 34

icmZR(@R5^oAtR@PD1+L6hEk5H4vkElig3

literal 0

HcmV?d00001