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From 080d3b14470f6ac59f4cfb97a4200ed18df5c260 Mon Sep 17 00:00:00 2001
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From: Fabian Henneke <fabian@henneke.me>
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Date: Wed, 21 Aug 2019 11:17:59 +0200
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Subject: [PATCH] udev: Add id program and rule for FIDO security tokens
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Add a fido_id program meant to be run for devices in the hidraw
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subsystem via an IMPORT directive. The program parses the HID report
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descriptor and assigns the ID_SECURITY_TOKEN environment variable if a
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declared usage matches the FIDO_CTAPHID_USAGE declared in the FIDO CTAP
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specification. This replaces the previous approach of whitelisting all
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known security token models manually.
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This commit is accompanied by a test suite and a fuzzer target for the
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descriptor parsing routine.
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Fixes: #11996.
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(cherry picked from commit d45ee2f31a8358db0accde2e7c81777cedadc3c2)
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Resolves: #1753369
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---
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 rules/60-fido-id.rules              |   7 ++
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 rules/meson.build                   |   1 +
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 src/fuzz/fuzz-fido-id-desc.c        |  23 +++++++
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 src/fuzz/fuzz-fido-id-desc.dict     |   6 ++
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 src/fuzz/meson.build                |   4 ++
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 src/test/meson.build                |   4 ++
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 src/test/test-fido-id-desc.c        |  85 +++++++++++++++++++++++
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 src/udev/fido_id/fido_id.c          | 103 ++++++++++++++++++++++++++++
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 src/udev/fido_id/fido_id_desc.c     |  92 +++++++++++++++++++++++++
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 src/udev/fido_id/fido_id_desc.h     |   8 +++
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 src/udev/meson.build                |   3 +
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 test/fuzz/fuzz-fido-id-desc/crash0  |   1 +
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 test/fuzz/fuzz-fido-id-desc/crash1  |   1 +
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 test/fuzz/fuzz-fido-id-desc/report0 | Bin 0 -> 71 bytes
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 test/fuzz/fuzz-fido-id-desc/report1 | Bin 0 -> 34 bytes
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 15 files changed, 338 insertions(+)
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 create mode 100644 rules/60-fido-id.rules
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 create mode 100644 src/fuzz/fuzz-fido-id-desc.c
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 create mode 100644 src/fuzz/fuzz-fido-id-desc.dict
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 create mode 100644 src/test/test-fido-id-desc.c
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 create mode 100644 src/udev/fido_id/fido_id.c
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 create mode 100644 src/udev/fido_id/fido_id_desc.c
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 create mode 100644 src/udev/fido_id/fido_id_desc.h
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 create mode 100644 test/fuzz/fuzz-fido-id-desc/crash0
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 create mode 100644 test/fuzz/fuzz-fido-id-desc/crash1
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 create mode 100644 test/fuzz/fuzz-fido-id-desc/report0
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 create mode 100644 test/fuzz/fuzz-fido-id-desc/report1
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diff --git a/rules/60-fido-id.rules b/rules/60-fido-id.rules
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new file mode 100644
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index 0000000000..fcf5079704
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--- /dev/null
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+++ b/rules/60-fido-id.rules
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@@ -0,0 +1,7 @@
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+# do not edit this file, it will be overwritten on update
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+
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+ACTION=="remove", GOTO="fido_id_end"
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+
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+SUBSYSTEM=="hidraw", IMPORT{program}="fido_id"
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+
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+LABEL="fido_id_end"
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diff --git a/rules/meson.build b/rules/meson.build
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index b6aae596b6..6363f8bf2e 100644
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--- a/rules/meson.build
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+++ b/rules/meson.build
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@@ -7,6 +7,7 @@ rules = files('''
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         60-cdrom_id.rules
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         60-drm.rules
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         60-evdev.rules
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+        60-fido-id.rules
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         60-input-id.rules
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         60-persistent-alsa.rules
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         60-persistent-input.rules
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diff --git a/src/fuzz/fuzz-fido-id-desc.c b/src/fuzz/fuzz-fido-id-desc.c
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new file mode 100644
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index 0000000000..cf98dee044
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--- /dev/null
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+++ b/src/fuzz/fuzz-fido-id-desc.c
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@@ -0,0 +1,23 @@
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+/* SPDX-License-Identifier: LGPL-2.1+ */
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+
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+#include <linux/hid.h>
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+#include <stdbool.h>
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+#include <stdint.h>
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+#include <stdlib.h>
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+
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+#include "fido_id/fido_id_desc.h"
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+#include "fuzz.h"
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+#include "log.h"
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+
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+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
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+        /* We don't want to fill the logs with messages about parse errors.
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+         * Disable most logging if not running standalone */
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+        if (!getenv("SYSTEMD_LOG_LEVEL"))
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+                log_set_max_level(LOG_CRIT);
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+
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+        if (size > HID_MAX_DESCRIPTOR_SIZE)
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+                return 0;
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+        (void) is_fido_security_token_desc(data, size);
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+
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+        return 0;
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+}
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diff --git a/src/fuzz/fuzz-fido-id-desc.dict b/src/fuzz/fuzz-fido-id-desc.dict
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new file mode 100644
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index 0000000000..d2d2679e18
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--- /dev/null
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+++ b/src/fuzz/fuzz-fido-id-desc.dict
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@@ -0,0 +1,6 @@
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+"\xfe"
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+"\x00"
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+"\x01"
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+"\xf1"
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+"\xd0"
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+"\xf1\xd0\x00\x01"
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diff --git a/src/fuzz/meson.build b/src/fuzz/meson.build
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index 1dbe28e57e..483a952421 100644
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--- a/src/fuzz/meson.build
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+++ b/src/fuzz/meson.build
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@@ -47,4 +47,8 @@ fuzzers += [
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          [libsystemd_journal_remote,
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           libshared],
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          []],
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+        [['src/fuzz/fuzz-fido-id-desc.c',
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+          'src/udev/fido_id/fido_id_desc.c'],
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+         [],
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+         []]
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 ]
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diff --git a/src/test/meson.build b/src/test/meson.build
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index 0998f59897..4259421f98 100644
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--- a/src/test/meson.build
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+++ b/src/test/meson.build
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@@ -663,6 +663,10 @@ tests += [
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         [['src/test/test-bus-util.c'],
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          [],
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          []],
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+        [['src/test/test-fido-id-desc.c',
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+          'src/udev/fido_id/fido_id_desc.c'],
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+         [],
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+         []],
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 ]
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 ############################################################
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diff --git a/src/test/test-fido-id-desc.c b/src/test/test-fido-id-desc.c
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new file mode 100644
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index 0000000000..cf55dd3266
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--- /dev/null
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+++ b/src/test/test-fido-id-desc.c
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@@ -0,0 +1,85 @@
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+/* SPDX-License-Identifier: LGPL-2.1+ */
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+
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+#include <stdint.h>
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+#include <stdlib.h>
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+
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+#include "fido_id/fido_id_desc.h"
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+#include "macro.h"
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+
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+static void test_is_fido_security_token_desc__fido(void) {
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+        static const uint8_t FIDO_HID_DESC_1[] = {
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+                0x06, 0xd0, 0xf1, 0x09, 0x01, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,
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+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,
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+                0x40, 0x91, 0x02, 0xc0,
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+        };
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+        assert_se(is_fido_security_token_desc(FIDO_HID_DESC_1, sizeof(FIDO_HID_DESC_1)) > 0);
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+
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+        static const uint8_t FIDO_HID_DESC_2[] = {
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+                0x05, 0x01, 0x09, 0x06, 0xa1, 0x01, 0x05, 0x07, 0x19, 0xe0, 0x29, 0xe7, 0x15, 0x00, 0x25,
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+                0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x95, 0x01, 0x75, 0x08, 0x81, 0x01, 0x95, 0x05,
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+                0x75, 0x01, 0x05, 0x08, 0x19, 0x01, 0x29, 0x05, 0x91, 0x02, 0x95, 0x01, 0x75, 0x03, 0x91,
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+                0x01, 0x95, 0x06, 0x75, 0x08, 0x15, 0x00, 0x25, 0x65, 0x05, 0x07, 0x19, 0x00, 0x29, 0x65,
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+                0x81, 0x00, 0x09, 0x03, 0x75, 0x08, 0x95, 0x08, 0xb1, 0x02, 0xc0,
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+                0x06, 0xd0, 0xf1, 0x09, 0x01, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,
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+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,
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+                0x40, 0x91, 0x02, 0xc0,
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+        };
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+        assert_se(is_fido_security_token_desc(FIDO_HID_DESC_2, sizeof(FIDO_HID_DESC_2)) > 0);
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+}
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+
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+static void test_is_fido_security_token_desc__non_fido(void) {
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+        /* Wrong usage page */
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+        static const uint8_t NON_FIDO_HID_DESC_1[] = {
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+                0x06, 0xd0, 0xf0, 0x09, 0x01, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,
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+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,
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+                0x40, 0x91, 0x02, 0xc0,
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+        };
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+        assert_se(is_fido_security_token_desc(NON_FIDO_HID_DESC_1, sizeof(NON_FIDO_HID_DESC_1)) == 0);
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+
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+        /* Wrong usage */
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+        static const uint8_t NON_FIDO_HID_DESC_2[] = {
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+                0x06, 0xd0, 0xf1, 0x09, 0x02, 0xa1, 0x01, 0x09, 0x20, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75,
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+                0x08, 0x95, 0x40, 0x81, 0x02, 0x09, 0x21, 0x15, 0x00, 0x26, 0xff, 0x00, 0x75, 0x08, 0x95,
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+                0x40, 0x91, 0x02, 0xc0,
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+        };
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+        assert_se(is_fido_security_token_desc(NON_FIDO_HID_DESC_2, sizeof(NON_FIDO_HID_DESC_2)) == 0);
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+
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+        static const uint8_t NON_FIDO_HID_DESC_3[] = {
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+                0x05, 0x01, 0x09, 0x06, 0xa1, 0x01, 0x05, 0x07, 0x19, 0xe0, 0x29, 0xe7, 0x15, 0x00, 0x25,
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+                0x01, 0x75, 0x01, 0x95, 0x08, 0x81, 0x02, 0x95, 0x01, 0x75, 0x08, 0x81, 0x01, 0x95, 0x05,
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+                0x75, 0x01, 0x05, 0x08, 0x19, 0x01, 0x29, 0x05, 0x91, 0x02, 0x95, 0x01, 0x75, 0x03, 0x91,
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+                0x01, 0x95, 0x06, 0x75, 0x08, 0x15, 0x00, 0x25, 0x65, 0x05, 0x07, 0x19, 0x00, 0x29, 0x65,
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+                0x81, 0x00, 0x09, 0x03, 0x75, 0x08, 0x95, 0x08, 0xb1, 0x02, 0xc0,
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+        };
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+        assert_se(is_fido_security_token_desc(NON_FIDO_HID_DESC_3, sizeof(NON_FIDO_HID_DESC_3)) == 0);
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+}
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+
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+static void test_is_fido_security_token_desc__invalid(void) {
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+        /* Size coded on 1 byte, but no byte given */
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+        static const uint8_t INVALID_HID_DESC_1[] = { 0x01 };
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+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_1, sizeof(INVALID_HID_DESC_1)) < 0);
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+
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+        /* Size coded on 2 bytes, but only 1 byte given */
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+        static const uint8_t INVALID_HID_DESC_2[] = { 0x02, 0x01 };
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+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_2, sizeof(INVALID_HID_DESC_2)) < 0);
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+
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+        /* Size coded on 4 bytes, but only 3 bytes given */
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+        static const uint8_t INVALID_HID_DESC_3[] = { 0x03, 0x01, 0x02, 0x03 };
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+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_3, sizeof(INVALID_HID_DESC_3)) < 0);
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+
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+        /* Long item without a size byte */
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+        static const uint8_t INVALID_HID_DESC_4[] = { 0xfe };
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+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_4, sizeof(INVALID_HID_DESC_4)) < 0);
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+
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+        /* Usage pages are coded on at most 2 bytes */
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+        static const uint8_t INVALID_HID_DESC_5[] = { 0x07, 0x01, 0x02, 0x03, 0x04 };
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+        assert_se(is_fido_security_token_desc(INVALID_HID_DESC_5, sizeof(INVALID_HID_DESC_5)) < 0);
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+}
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+
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+int main(int argc, char *argv[]) {
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+        test_is_fido_security_token_desc__fido();
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+        test_is_fido_security_token_desc__non_fido();
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+        test_is_fido_security_token_desc__invalid();
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+
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+        return EXIT_SUCCESS;
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+}
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diff --git a/src/udev/fido_id/fido_id.c b/src/udev/fido_id/fido_id.c
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new file mode 100644
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index 0000000000..7e1cc804f2
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--- /dev/null
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+++ b/src/udev/fido_id/fido_id.c
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@@ -0,0 +1,103 @@
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+/* SPDX-License-Identifier: LGPL-2.1+ */
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+/*
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+ * Identifies FIDO CTAP1 ("U2F")/CTAP2 security tokens based on the usage declared in their report
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+ * descriptor and outputs suitable environment variables.
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+ *
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+ * Inspired by Andrew Lutomirski's 'u2f-hidraw-policy.c'
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+ */
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+
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+#include <errno.h>
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+#include <fcntl.h>
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+#include <linux/hid.h>
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+#include <stdio.h>
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+#include <stdlib.h>
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+#include <sys/types.h>
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+#include <unistd.h>
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+
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+#include "sd-device.h"
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+
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+#include "device-internal.h"
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+#include "device-private.h"
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+#include "device-util.h"
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+#include "fd-util.h"
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+#include "fido_id_desc.h"
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+#include "log.h"
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+#include "macro.h"
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+#include "path-util.h"
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+#include "string-util.h"
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+#include "udev-util.h"
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+
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+static int run(int argc, char **argv) {
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+        _cleanup_(sd_device_unrefp) struct sd_device *device = NULL;
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+        _cleanup_free_ char *desc_path = NULL;
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+        _cleanup_close_ int fd = -1;
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+
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+        struct sd_device *hid_device;
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+        const char *sys_path;
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+        uint8_t desc[HID_MAX_DESCRIPTOR_SIZE];
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+        ssize_t desc_len;
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+
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+        int r;
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+
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+        log_set_target(LOG_TARGET_AUTO);
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+        udev_parse_config();
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+        log_parse_environment();
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+        log_open();
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+
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+        if (argc > 2)
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+                return log_error_errno(EINVAL, "Usage: %s [SYSFS_PATH]", program_invocation_short_name);
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+
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+        if (argc == 1) {
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+                r = device_new_from_strv(&device, environ);
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+                if (r < 0)
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+                        return log_error_errno(r, "Failed to get current device from environment: %m");
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+        } else {
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+                r = sd_device_new_from_syspath(&device, argv[1]);
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+                if (r < 0)
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+                        return log_error_errno(r, "Failed to get device from syspath: %m");
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+        }
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+
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+        r = sd_device_get_parent(device, &hid_device);
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+        if (r < 0)
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+                return log_device_error_errno(device, r, "Failed to get parent HID device: %m");
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+
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+        r = sd_device_get_syspath(hid_device, &sys_path);
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+        if (r < 0)
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+                return log_device_error_errno(hid_device, r, "Failed to get syspath for HID device: %m");
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+
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+        desc_path = path_join(NULL, sys_path, "report_descriptor");
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+        if (!desc_path)
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+                return log_oom();
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+
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+        fd = open(desc_path, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
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+        if (fd < 0)
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+                return log_device_error_errno(hid_device, errno,
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+                                              "Failed to open report descriptor at '%s': %m", desc_path);
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+
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+        desc_len = read(fd, desc, sizeof(desc));
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+        if (desc_len < 0)
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+                return log_device_error_errno(hid_device, errno,
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+                                              "Failed to read report descriptor at '%s': %m", desc_path);
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+        if (desc_len == 0)
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+                return log_device_debug_errno(hid_device, EINVAL,
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+                                              "Empty report descriptor at '%s'.", desc_path);
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+
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+        r = is_fido_security_token_desc(desc, desc_len);
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+        if (r < 0)
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+                return log_device_debug_errno(hid_device, r,
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+                                              "Failed to parse report descriptor at '%s'.", desc_path);
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+        if (r > 0) {
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+                printf("ID_FIDO_TOKEN=1\n");
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+                printf("ID_SECURITY_TOKEN=1\n");
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+        }
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+
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+        return 0;
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+}
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+
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+int main(int argc, char *argv[]) {
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+    int r;
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+
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+    r = run(argc, argv);
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+
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+    return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
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+}
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diff --git a/src/udev/fido_id/fido_id_desc.c b/src/udev/fido_id/fido_id_desc.c
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new file mode 100644
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index 0000000000..bbfcf93709
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--- /dev/null
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+++ b/src/udev/fido_id/fido_id_desc.c
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@@ -0,0 +1,92 @@
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+/* SPDX-License-Identifier: LGPL-2.1+ */
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+/* Inspired by Andrew Lutomirski's 'u2f-hidraw-policy.c' */
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+
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+#include <errno.h>
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+#include <stdbool.h>
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+#include <stddef.h>
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+#include <stdint.h>
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+
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+#include "fido_id_desc.h"
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+
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+#define HID_RPTDESC_FIRST_BYTE_LONG_ITEM 0xfeu
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+#define HID_RPTDESC_TYPE_GLOBAL 0x1u
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+#define HID_RPTDESC_TYPE_LOCAL 0x2u
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+#define HID_RPTDESC_TAG_USAGE_PAGE 0x0u
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+#define HID_RPTDESC_TAG_USAGE 0x0u
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+
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+/*
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+ * HID usage for FIDO CTAP1 ("U2F") and CTAP2 security tokens.
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+ * https://fidoalliance.org/specs/fido-u2f-v1.0-ps-20141009/fido-u2f-u2f_hid.h-v1.0-ps-20141009.txt
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+ * https://fidoalliance.org/specs/fido-v2.0-ps-20190130/fido-client-to-authenticator-protocol-v2.0-ps-20190130.html#usb-discovery
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+ * https://www.usb.org/sites/default/files/hutrr48.pdf
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+ */
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+#define FIDO_FULL_USAGE_CTAPHID 0xf1d00001u
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+
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+/*
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+ * Parses a HID report descriptor and identifies FIDO CTAP1 ("U2F")/CTAP2 security tokens based on their
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+ * declared usage.
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+ * A positive return value indicates that the report descriptor belongs to a FIDO security token.
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+ * https://www.usb.org/sites/default/files/documents/hid1_11.pdf (Section 6.2.2)
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+ */
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+int is_fido_security_token_desc(const uint8_t *desc, size_t desc_len) {
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+        uint32_t usage = 0;
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+
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+        for (size_t pos = 0; pos < desc_len; ) {
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+                uint8_t tag, type, size_code;
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+                size_t size;
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+                uint32_t value;
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+
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+                /* Report descriptors consists of short items (1-5 bytes) and long items (3-258 bytes). */
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+                if (desc[pos] == HID_RPTDESC_FIRST_BYTE_LONG_ITEM) {
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+                        /* No long items are defined in the spec; skip them.
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+                         * The length of the data in a long item is contained in the byte after the long
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+                         * item tag. The header consists of three bytes: special long item tag, length,
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+                         * actual tag. */
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+                        if (pos + 1 >= desc_len)
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+                                return -EINVAL;
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+                        pos += desc[pos + 1] + 3;
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+                        continue;
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+                }
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+
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+                /* The first byte of a short item encodes tag, type and size. */
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+                tag = desc[pos] >> 4;          /* Bits 7 to 4 */
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+                type = (desc[pos] >> 2) & 0x3; /* Bits 3 and 2 */
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+                size_code = desc[pos] & 0x3;   /* Bits 1 and 0 */
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+                /* Size is coded as follows:
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+                 * 0 -> 0 bytes, 1 -> 1 byte, 2 -> 2 bytes, 3 -> 4 bytes
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+                 */
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+                size = size_code < 3 ? size_code : 4;
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+                /* Consume header byte. */
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+                pos++;
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+
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+                /* Extract the item value coded on size bytes. */
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+                if (pos + size > desc_len)
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+                        return -EINVAL;
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+                value = 0;
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+                for (size_t i = 0; i < size; i++)
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+                        value |= (uint32_t) desc[pos + i] << (8 * i);
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+                /* Consume value bytes. */
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+                pos += size;
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+
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+                if (type == HID_RPTDESC_TYPE_GLOBAL && tag == HID_RPTDESC_TAG_USAGE_PAGE) {
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+                        /* A usage page is a 16 bit value coded on at most 16 bits. */
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+                        if (size > 2)
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+                                return -EINVAL;
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+                        /* A usage page sets the upper 16 bits of a following usage. */
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+                        usage = (value & 0x0000ffffu) << 16;
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+                }
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+
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+                if (type == HID_RPTDESC_TYPE_LOCAL && tag == HID_RPTDESC_TAG_USAGE) {
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+                        /* A usage is a 32 bit value, but is prepended with the current usage page if
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+                         * coded on less than 4 bytes (that is, at most 2 bytes). */
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+                        if (size == 4)
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+                                usage = value;
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+                        else
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+                                usage = (usage & 0xffff0000u) | (value & 0x0000ffffu);
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+                        if (usage == FIDO_FULL_USAGE_CTAPHID)
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+                                return 1;
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+                }
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+        }
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+
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+        return 0;
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+}
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diff --git a/src/udev/fido_id/fido_id_desc.h b/src/udev/fido_id/fido_id_desc.h
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new file mode 100644
4fbe94
index 0000000000..c813a3a454
4fbe94
--- /dev/null
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+++ b/src/udev/fido_id/fido_id_desc.h
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@@ -0,0 +1,8 @@
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+/* SPDX-License-Identifier: LGPL-2.1+ */
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+
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+#pragma once
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+
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+#include <stddef.h>
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+#include <stdint.h>
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+
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+int is_fido_security_token_desc(const uint8_t *desc, size_t desc_len);
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diff --git a/src/udev/meson.build b/src/udev/meson.build
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index 3bcd2bd3d7..5931a6da7d 100644
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--- a/src/udev/meson.build
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+++ b/src/udev/meson.build
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@@ -160,6 +160,9 @@ libudev_core = static_library(
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 foreach prog : [['ata_id/ata_id.c'],
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                 ['cdrom_id/cdrom_id.c'],
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                 ['collect/collect.c'],
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+                ['fido_id/fido_id.c',
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+                 'fido_id/fido_id_desc.c',
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+                 'fido_id/fido_id_desc.h'],
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                 ['scsi_id/scsi_id.c',
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                  'scsi_id/scsi_id.h',
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                  'scsi_id/scsi_serial.c',
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diff --git a/test/fuzz/fuzz-fido-id-desc/crash0 b/test/fuzz/fuzz-fido-id-desc/crash0
4fbe94
new file mode 100644
4fbe94
index 0000000000..e066656502
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--- /dev/null
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+++ b/test/fuzz/fuzz-fido-id-desc/crash0
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@@ -0,0 +1 @@
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+????Ì?
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\ No newline at end of file
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diff --git a/test/fuzz/fuzz-fido-id-desc/crash1 b/test/fuzz/fuzz-fido-id-desc/crash1
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new file mode 100644
4fbe94
index 0000000000..aef3e18335
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--- /dev/null
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+++ b/test/fuzz/fuzz-fido-id-desc/crash1
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@@ -0,0 +1 @@
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+øûøûûÜ
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\ No newline at end of file
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diff --git a/test/fuzz/fuzz-fido-id-desc/report0 b/test/fuzz/fuzz-fido-id-desc/report0
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new file mode 100644
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index 0000000000000000000000000000000000000000..48757cba682ffddd5a1ddd8988bb8bcdc7db0a7a
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GIT binary patch
4fbe94
literal 71
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zcmZQ&<YZgO$jUDHK=ZjMgDPVw<5Z4Drm2jj9F2@qSxXsNIV2f1Sto)-m?tt$Wh>
4fbe94
Xs!9c_XV6S-WZ+~j<(SH`k?8;c6l@Pq
4fbe94
4fbe94
literal 0
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HcmV?d00001
4fbe94
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diff --git a/test/fuzz/fuzz-fido-id-desc/report1 b/test/fuzz/fuzz-fido-id-desc/report1
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new file mode 100644
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index 0000000000000000000000000000000000000000..b70b7fb871aeccf4074ccbd20e3cdbaca42e23b3
4fbe94
GIT binary patch
4fbe94
literal 34
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icmZR(@R5^oAtR@PD1+L6hEk5H4vkElig3
4fbe94
4fbe94
literal 0
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HcmV?d00001
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