diff --git a/docs/hsi.md b/docs/hsi.md index 208113e21..88c2573c7 100644 --- a/docs/hsi.md +++ b/docs/hsi.md @@ -392,6 +392,28 @@ To meet HSI-2 on systems that run this test, the result must be `locked`. *[v1.5 - [Intel Direct Connect Interface](https://www.intel.co.uk/content/www/uk/en/support/articles/000029393/processors.html) + + +### [Empty PCR in TPM](#org.fwupd.hsi.Tpm.EmptyPcr) + +The system firmware is responsible for measuring values about its boot stage in PCRs 0 through 7. +Some firmwares have bugs that prevent them from measuring some of those values, breaking the fundamental assumption of the Measured Boot chain-of-trust. + +**Impact:** A local attacker could measure fake values into the empty PCR, corresponding to a firmware and OS that do not match the ones actually loaded. +This allows hiding a compromised boot chain or fooling a remote-attestation server into believing that a different kernel is running. + +**Possible results:** + +- `valid`: all correct +- `not-valid`: at least one empty checksum has been found +- `not-found`: no TPM hardware could be found + +To meet HSI-1 on systems that run this test, all PCRs from 0 to 7 in all banks must have non-empty measurements *[v1.7.2]* + +**References:** + +- [CVE-2021-42299: TPM Carte Blanche](https://github.com/google/security-research/blob/master/pocs/bios/tpm-carte-blanche/writeup.md) + ### [PCR0 TPM Event Log Reconstruction](#org.fwupd.hsi.Tpm.ReconstructionPcr0) diff --git a/libfwupd/fwupd-security-attr-private.h b/libfwupd/fwupd-security-attr-private.h index a1ad657d7..228433c9a 100644 --- a/libfwupd/fwupd-security-attr-private.h +++ b/libfwupd/fwupd-security-attr-private.h @@ -221,6 +221,14 @@ G_BEGIN_DECLS * Since: 1.5.0 **/ #define FWUPD_SECURITY_ATTR_ID_SUSPEND_TO_RAM "org.fwupd.hsi.SuspendToRam" +/** + * FWUPD_SECURITY_ATTR_ID_TPM_EMPTY_PCR: + * + * Host Security ID attribute for empty PCR + * + * Since: 1.7.2 + **/ +#define FWUPD_SECURITY_ATTR_ID_TPM_EMPTY_PCR "org.fwupd.hsi.Tpm.EmptyPcr" /** * FWUPD_SECURITY_ATTR_ID_TPM_RECONSTRUCTION_PCR0: * diff --git a/plugins/tpm/fu-plugin-tpm.c b/plugins/tpm/fu-plugin-tpm.c index 04130147c..8fe9b1486 100644 --- a/plugins/tpm/fu-plugin-tpm.c +++ b/plugins/tpm/fu-plugin-tpm.c @@ -153,8 +153,7 @@ fu_plugin_tpm_add_security_attr_eventlog(FuPlugin *plugin, FuSecurityAttrs *attr fu_security_attrs_append(attrs, attr); /* check reconstructed to PCR0 */ - if (fu_plugin_has_flag(plugin, FWUPD_PLUGIN_FLAG_DISABLED) || data->bios_device == NULL || - data->ev_items == NULL) { + if (data->ev_items == NULL || data->bios_device == NULL) { fwupd_security_attr_set_result(attr, FWUPD_SECURITY_ATTR_RESULT_NOT_FOUND); return; } @@ -197,11 +196,59 @@ fu_plugin_tpm_add_security_attr_eventlog(FuPlugin *plugin, FuSecurityAttrs *attr fwupd_security_attr_set_result(attr, FWUPD_SECURITY_ATTR_RESULT_VALID); } +static void +fu_plugin_tpm_add_security_attr_empty(FuPlugin *plugin, FuSecurityAttrs *attrs) +{ + FuPluginData *data = fu_plugin_get_data(plugin); + g_autoptr(FwupdSecurityAttr) attr = NULL; + + /* no TPM device */ + if (data->tpm_device == NULL) + return; + + /* add attributes */ + attr = fwupd_security_attr_new(FWUPD_SECURITY_ATTR_ID_TPM_EMPTY_PCR); + fwupd_security_attr_set_plugin(attr, fu_plugin_get_name(plugin)); + fwupd_security_attr_set_level(attr, FWUPD_SECURITY_ATTR_LEVEL_CRITICAL); + fwupd_security_attr_add_guids(attr, fu_device_get_guids(data->tpm_device)); + fu_security_attrs_append(attrs, attr); + + /* check PCRs 0 through 7 for empty checksums */ + for (guint pcr = 0; pcr <= 7; pcr++) { + g_autoptr(GPtrArray) checksums = fu_tpm_device_get_checksums(data->tpm_device, pcr); + for (guint i = 0; i < checksums->len; i++) { + const gchar *checksum = g_ptr_array_index(checksums, i); + gboolean empty = TRUE; + + /* empty checksum is zero, so made entirely of zeroes */ + for (guint j = 0; checksum[j] != '\0'; j++) { + if (checksum[j] != '0') { + empty = FALSE; + break; + } + } + if (empty) { + fwupd_security_attr_set_result( + attr, + FWUPD_SECURITY_ATTR_RESULT_NOT_VALID); + return; + } + } + } + + /* success */ + fwupd_security_attr_add_flag(attr, FWUPD_SECURITY_ATTR_FLAG_SUCCESS); + fwupd_security_attr_set_result(attr, FWUPD_SECURITY_ATTR_RESULT_VALID); +} + static void fu_plugin_tpm_add_security_attrs(FuPlugin *plugin, FuSecurityAttrs *attrs) { + if (fu_plugin_has_flag(plugin, FWUPD_PLUGIN_FLAG_DISABLED)) + return; fu_plugin_tpm_add_security_attr_version(plugin, attrs); fu_plugin_tpm_add_security_attr_eventlog(plugin, attrs); + fu_plugin_tpm_add_security_attr_empty(plugin, attrs); } static gchar * diff --git a/plugins/tpm/fu-self-test.c b/plugins/tpm/fu-self-test.c index f7a0acd89..4c1b70513 100644 --- a/plugins/tpm/fu-self-test.c +++ b/plugins/tpm/fu-self-test.c @@ -23,7 +23,6 @@ fu_tpm_device_1_2_func(void) GPtrArray *devices; gboolean ret; g_autofree gchar *pluginfn = NULL; - g_autofree gchar *testdatadir = NULL; g_autoptr(FuContext) ctx = fu_context_new(); g_autoptr(FuPlugin) plugin = fu_plugin_new(ctx); g_autoptr(FuSecurityAttrs) attrs = fu_security_attrs_new(); @@ -60,13 +59,18 @@ fu_tpm_device_1_2_func(void) g_assert_nonnull(pcrXs); g_assert_cmpint(pcrXs->len, ==, 0); - /* verify HSI attr */ + /* verify HSI attributes */ fu_plugin_runner_add_security_attrs(plugin, attrs); attr = fu_security_attrs_get_by_appstream_id(attrs, FWUPD_SECURITY_ATTR_ID_TPM_VERSION_20); g_assert_nonnull(attr); g_assert_cmpint(fwupd_security_attr_get_result(attr), ==, FWUPD_SECURITY_ATTR_RESULT_NOT_ENABLED); + + attr = fu_security_attrs_get_by_appstream_id(attrs, FWUPD_SECURITY_ATTR_ID_TPM_EMPTY_PCR); + g_assert_nonnull(attr); + /* Some PCRs are empty, but PCRs 0-7 are set (tests/tpm0/pcrs) */ + g_assert_cmpint(fwupd_security_attr_get_result(attr), ==, FWUPD_SECURITY_ATTR_RESULT_VALID); } static void @@ -84,6 +88,7 @@ fu_tpm_device_2_0_func(void) if (tpm_server_running == NULL && (getuid() != 0 || geteuid() != 0)) { g_test_skip("TPM2.0 tests require simulated TPM2.0 running or need root access " "with physical TPM"); + g_unsetenv("FWUPD_FORCE_TPM2"); return; } #endif @@ -92,6 +97,7 @@ fu_tpm_device_2_0_func(void) if (tpm_server_running == NULL && g_error_matches(error, FWUPD_ERROR, FWUPD_ERROR_NOT_FOUND)) { g_test_skip("no physical or simulated TPM 2.0 device available"); + g_unsetenv("FWUPD_FORCE_TPM2"); return; } } @@ -179,6 +185,53 @@ fu_tpm_eventlog_parse_v2_func(void) "6d9fed68092cfb91c9552bcb7879e75e1df36efd407af67690dc3389a5722fab"); } +static void +fu_tpm_empty_pcr_func(void) +{ + gboolean ret; + g_autofree gchar **environ = NULL; + g_autofree gchar *pluginfn = NULL; + g_autofree gchar *testdatadir = NULL; + g_autoptr(FuContext) ctx = fu_context_new(); + g_autoptr(FuPlugin) plugin = fu_plugin_new(ctx); + g_autoptr(FuSecurityAttrs) attrs = fu_security_attrs_new(); + g_autoptr(FwupdSecurityAttr) attr = NULL; + g_autoptr(GError) error = NULL; + g_autoptr(GPtrArray) pcr0s = NULL; + g_autoptr(GPtrArray) pcrXs = NULL; + + /* do not save silo */ + ret = fu_context_load_quirks(ctx, FU_QUIRKS_LOAD_FLAG_NO_CACHE, &error); + g_assert_no_error(error); + g_assert_true(ret); + + /* save environment and set broken PCR data */ + environ = g_get_environ(); + testdatadir = g_test_build_filename(G_TEST_DIST, "tests", "empty_pcr", NULL); + g_setenv("FWUPD_SYSFSTPMDIR", testdatadir, TRUE); + + /* load the plugin */ + pluginfn = g_test_build_filename(G_TEST_BUILT, "libfu_plugin_tpm." G_MODULE_SUFFIX, NULL); + ret = fu_plugin_open(plugin, pluginfn, &error); + g_assert_no_error(error); + g_assert_true(ret); + ret = fu_plugin_runner_startup(plugin, &error); + g_assert_no_error(error); + g_assert_true(ret); + + /* verify HSI attr */ + fu_plugin_runner_add_security_attrs(plugin, attrs); + attr = fu_security_attrs_get_by_appstream_id(attrs, FWUPD_SECURITY_ATTR_ID_TPM_EMPTY_PCR); + g_assert_nonnull(attr); + /* PCR 6 is empty (tests/empty_pcr/tpm0/pcrs) */ + g_assert_cmpint(fwupd_security_attr_get_result(attr), + ==, + FWUPD_SECURITY_ATTR_RESULT_NOT_VALID); + + /* restore default environment */ + g_setenv("FWUPD_SYSFSTPMDIR", g_environ_getenv(environ, "FWUPD_SYSFSTPMDIR"), TRUE); +} + int main(int argc, char **argv) { @@ -187,8 +240,6 @@ main(int argc, char **argv) g_test_init(&argc, &argv, NULL); testdatadir = g_test_build_filename(G_TEST_DIST, "tests", NULL); - g_setenv("FWUPD_SYSFSFWDIR", testdatadir, TRUE); - g_setenv("FWUPD_SYSFSDRIVERDIR", testdatadir, TRUE); g_setenv("FWUPD_SYSFSTPMDIR", testdatadir, TRUE); g_setenv("FWUPD_UEFI_TEST", "1", TRUE); @@ -199,6 +250,7 @@ main(int argc, char **argv) /* tests go here */ g_test_add_func("/tpm/pcrs1.2", fu_tpm_device_1_2_func); g_test_add_func("/tpm/pcrs2.0", fu_tpm_device_2_0_func); + g_test_add_func("/tpm/empty-pcr", fu_tpm_empty_pcr_func); g_test_add_func("/tpm/eventlog-parse{v1}", fu_tpm_eventlog_parse_v1_func); g_test_add_func("/tpm/eventlog-parse{v2}", fu_tpm_eventlog_parse_v2_func); return g_test_run(); diff --git a/plugins/tpm/tests/empty_pcr/tpm0/active b/plugins/tpm/tests/empty_pcr/tpm0/active new file mode 100644 index 000000000..d00491fd7 --- /dev/null +++ b/plugins/tpm/tests/empty_pcr/tpm0/active @@ -0,0 +1 @@ +1 diff --git a/plugins/tpm/tests/empty_pcr/tpm0/caps b/plugins/tpm/tests/empty_pcr/tpm0/caps new file mode 100644 index 000000000..af0d3cb00 --- /dev/null +++ b/plugins/tpm/tests/empty_pcr/tpm0/caps @@ -0,0 +1,3 @@ +Manufacturer: 0x49465800 +TCG version: 1.2 +Firmware version: 6.40 diff --git a/plugins/tpm/tests/empty_pcr/tpm0/enabled b/plugins/tpm/tests/empty_pcr/tpm0/enabled new file mode 100644 index 000000000..d00491fd7 --- /dev/null +++ b/plugins/tpm/tests/empty_pcr/tpm0/enabled @@ -0,0 +1 @@ +1 diff --git a/plugins/tpm/tests/empty_pcr/tpm0/owned b/plugins/tpm/tests/empty_pcr/tpm0/owned new file mode 100644 index 000000000..d00491fd7 --- /dev/null +++ b/plugins/tpm/tests/empty_pcr/tpm0/owned @@ -0,0 +1 @@ +1 diff --git a/plugins/tpm/tests/empty_pcr/tpm0/pcrs b/plugins/tpm/tests/empty_pcr/tpm0/pcrs new file mode 100644 index 000000000..1f8a19c91 --- /dev/null +++ b/plugins/tpm/tests/empty_pcr/tpm0/pcrs @@ -0,0 +1,24 @@ +PCR-00: 3C 97 99 20 C9 00 99 60 09 27 D5 DA B3 81 EB 95 1E 7F C8 68 +PCR-01: CE 9F A4 B2 01 09 D8 81 14 EA 1A 6D 13 94 CD 45 5F 52 69 23 +PCR-02: 47 09 7A 9A AD C3 26 A4 93 91 26 63 A1 6F DF 53 D7 88 96 8E +PCR-03: B2 A8 3B 0E BF 2F 83 74 29 9A 5B 2B DF C3 1E A9 55 AD 72 36 +PCR-04: A4 A5 87 4C 59 94 8D 9B 93 66 0A F4 19 D8 6F F8 94 36 20 CC +PCR-05: 00 0B 58 00 89 72 EF 6C 2A AC 79 33 C4 AE 67 6B A6 EF CF 6A +PCR-06: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-07: 0A 2A 68 15 85 0D AC B2 D1 F4 E0 C1 F4 56 D5 E2 81 08 6D EA +PCR-08: DB A7 29 4E 49 BA D7 9E 53 99 0A 6E 3A CB 52 97 B9 08 3A 66 +PCR-09: 19 F9 6F 10 83 F5 5B 50 98 26 C3 14 73 43 35 21 1F E6 39 E9 +PCR-10: 37 3D 89 9E 10 0D DD 2D 21 B5 F4 96 8D 4F DC A7 6D 1A C7 BD +PCR-11: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-12: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-13: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-14: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-15: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-16: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 +PCR-17: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF +PCR-18: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF +PCR-19: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF +PCR-20: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF +PCR-21: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF +PCR-22: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF +PCR-23: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 diff --git a/src/fu-security-attr.c b/src/fu-security-attr.c index ea28a018d..9dd39d4ec 100644 --- a/src/fu-security-attr.c +++ b/src/fu-security-attr.c @@ -113,6 +113,10 @@ fu_security_attr_get_name(FwupdSecurityAttr *attr) /* TRANSLATORS: Title: SB is a way of locking down UEFI */ return g_strdup(_("UEFI secure boot")); } + if (g_strcmp0(appstream_id, FWUPD_SECURITY_ATTR_ID_TPM_EMPTY_PCR) == 0) { + /* TRANSLATORS: Title: PCRs (Platform Configuration Registers) shouldn't be empty */ + return g_strdup(_("TPM empty PCRs")); + } if (g_strcmp0(appstream_id, FWUPD_SECURITY_ATTR_ID_TPM_RECONSTRUCTION_PCR0) == 0) { /* TRANSLATORS: Title: the PCR is rebuilt from the TPM event log */ return g_strdup(_("TPM PCR0 reconstruction")); diff --git a/src/fu-util-common.c b/src/fu-util-common.c index 75680c86e..722381b78 100644 --- a/src/fu-util-common.c +++ b/src/fu-util-common.c @@ -2012,6 +2012,22 @@ fu_util_security_event_to_string(FwupdSecurityAttr *attr) FWUPD_SECURITY_ATTR_RESULT_ENABLED, /* TRANSLATORS: HSI event title */ _("Secure Boot enabled")}, + /* ------------------------------------------*/ + {"org.fwupd.hsi.Tpm.EmptyPcr", + FWUPD_SECURITY_ATTR_RESULT_UNKNOWN, + FWUPD_SECURITY_ATTR_RESULT_VALID, + /* TRANSLATORS: HSI event title */ + _("All TPM PCRs are valid")}, + {"org.fwupd.hsi.Tpm.EmptyPcr", + FWUPD_SECURITY_ATTR_RESULT_VALID, + FWUPD_SECURITY_ATTR_RESULT_NOT_VALID, + /* TRANSLATORS: HSI event title */ + _("All TPM PCRs are now valid")}, + {"org.fwupd.hsi.Uefi.SecureBoot", + FWUPD_SECURITY_ATTR_RESULT_NOT_VALID, + FWUPD_SECURITY_ATTR_RESULT_VALID, + /* TRANSLATORS: HSI event title */ + _("A TPM PCR is now an invalid value")}, {NULL, 0, 0, NULL}}; /* sanity check */