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.

2 files changed, 90 insertions, 0 deletions

diff --git a/src/test/meson.build b/src/test/meson.build
index de31e977bc..a8c3e59098 100644
--- a/src/test/meson.build
+++ b/src/test/meson.build
@@ -771,6 +771,11 @@ tests += [
         [['src/test/test-local-addresses.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;
+}