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pcrextend: make use new nvindex-based PCRs

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This commit is contained in:
Lennart Poettering
2024-06-03 21:44:50 +02:00
parent f5f26332fa
commit 2b90bf1730
5 changed files with 188 additions and 28 deletions
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13
catalog/systemd.catalog.in
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@@ -743,6 +743,19 @@ PCRs ares extended with a different string, to ensure that security
policies for TPM-bound secrets and other resources are limited to specific
phases of the runtime.
-- 4c2e46d266a747c6ac1460aa54484fa7
Subject: TPM NvPCR Extended
Defined-By: systemd
Support: %SUPPORT_URL%
The Trusted Platform Module's (TPM) additional Platform Configuration Register
(PCR) stored in non-volatile indexes (NV Indexes) @NVPCR@, has been extended
with the string '@MEASURING@'.
System state, configuration and properties are cryptographically measured into
the security chip in an irreversible way to provide local and remote
attestation of system state and identity.
-- f9b0be465ad540d0850ad32172d57c21
Subject: Memory Trimmed
Defined-By: systemd

34
man/systemd-pcrphase.service.xml
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@@ -138,7 +138,8 @@
<title>Options</title>
<para>The <filename>/usr/lib/systemd/system-pcrextend</filename> executable may also be invoked from the
command line, where it expects the word to extend into PCR 11, as well as the following switches:</para>
command line, where it expects the word to extend into a PCR or NvPCR, as well as the following
switches:</para>
<variablelist>
<varlistentry>
@@ -155,11 +156,22 @@
<term><option>--pcr=</option></term>
<listitem><para>Takes the index of the PCR to extend. If <option>--machine-id</option> or
<option>--file-system=</option> are specified defaults to 15, otherwise defaults to 11.</para>
<option>--file-system=</option> are specified defaults to 15, otherwise defaults to 11. May not be
combined with <option>--nvpcr=</option>.</para>
<xi:include href="version-info.xml" xpointer="v255"/></listitem>
</varlistentry>
<varlistentry>
<term><option>--nvpcr=</option></term>
<listitem><para>Takes a name of an NvPCR to extend. NvPCRs are additional PCRs implemented via TPM NV
indexes. The name should be a short string such as <literal>hardware</literal> or
<literal>disk-encryption</literal>. May not be combined with <option>--pcr=</option>.</para>
<xi:include href="version-info.xml" xpointer="v259"/></listitem>
</varlistentry>
<varlistentry>
<term><option>--tpm2-device=<replaceable>PATH</replaceable></option></term>
@@ -182,6 +194,17 @@
<xi:include href="version-info.xml" xpointer="v253"/></listitem>
</varlistentry>
<varlistentry>
<term><option>--early</option></term>
<listitem><para>Selects early-boot mode. Specifically this means that the NvPCR anchor secret is not
attempted to be written into <filename>/var/lib/</filename> and the boot loader partition in addition
to <filename>/run/</filename>. (Unlike the latter the former are generally not mounted and writable
during early boot or in the initrd.)</para>
<xi:include href="version-info.xml" xpointer="v259"/></listitem>
</varlistentry>
<varlistentry>
<term><option>--machine-id</option></term>
@@ -230,6 +253,13 @@
<xi:include href="version-info.xml" xpointer="v252"/></listitem>
</varlistentry>
<varlistentry>
<term><filename>/usr/lib/nvpcr/*.nvpcr</filename></term>
<listitem><para>Definition files for NvPCRs.</para>
<xi:include href="version-info.xml" xpointer="v259"/></listitem>
</varlistentry>
</variablelist>
</refsect1>

161
src/pcrextend/pcrextend.c
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@@ -28,11 +28,14 @@ static char **arg_banks = NULL;
static char *arg_file_system = NULL;
static bool arg_machine_id = false;
static unsigned arg_pcr_index = UINT_MAX;
static char *arg_nvpcr_name = NULL;
static bool arg_varlink = false;
static bool arg_early = false;
STATIC_DESTRUCTOR_REGISTER(arg_banks, strv_freep);
STATIC_DESTRUCTOR_REGISTER(arg_tpm2_device, freep);
STATIC_DESTRUCTOR_REGISTER(arg_file_system, freep);
STATIC_DESTRUCTOR_REGISTER(arg_nvpcr_name, freep);
#define EXTENSION_STRING_SAFE_LIMIT 1024
@@ -53,10 +56,12 @@ static int help(int argc, char *argv[], void *userdata) {
" --version Print version\n"
" --bank=DIGEST Select TPM PCR bank (SHA1, SHA256)\n"
" --pcr=INDEX Select TPM PCR index (0…23)\n"
" --nvpcr=NAME Select TPM PCR mode nvindex name\n"
" --tpm2-device=PATH Use specified TPM2 device\n"
" --graceful Exit gracefully if no TPM2 device is found\n"
" --file-system=PATH Measure UUID/labels of file system into PCR 15\n"
" --machine-id Measure machine ID into PCR 15\n"
" --early Run in early boot mode, without access to /var/\n"
"\nSee the %2$s for details.\n",
program_invocation_short_name,
link,
@@ -73,10 +78,12 @@ static int parse_argv(int argc, char *argv[]) {
ARG_VERSION = 0x100,
ARG_BANK,
ARG_PCR,
ARG_NVPCR,
ARG_TPM2_DEVICE,
ARG_GRACEFUL,
ARG_FILE_SYSTEM,
ARG_MACHINE_ID,
ARG_EARLY,
};
static const struct option options[] = {
@@ -84,10 +91,12 @@ static int parse_argv(int argc, char *argv[]) {
{ "version", no_argument, NULL, ARG_VERSION },
{ "bank", required_argument, NULL, ARG_BANK },
{ "pcr", required_argument, NULL, ARG_PCR },
{ "nvpcr", required_argument, NULL, ARG_NVPCR },
{ "tpm2-device", required_argument, NULL, ARG_TPM2_DEVICE },
{ "graceful", no_argument, NULL, ARG_GRACEFUL },
{ "file-system", required_argument, NULL, ARG_FILE_SYSTEM },
{ "machine-id", no_argument, NULL, ARG_MACHINE_ID },
{ "early", no_argument, NULL, ARG_EARLY },
{}
};
@@ -127,6 +136,15 @@ static int parse_argv(int argc, char *argv[]) {
arg_pcr_index = r;
break;
case ARG_NVPCR:
if (!tpm2_nvpcr_name_is_valid(optarg))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "NvPCR name is not valid: %s", optarg);
r = free_and_strdup_warn(&arg_nvpcr_name, optarg);
if (r < 0)
return r;
break;
case ARG_TPM2_DEVICE: {
_cleanup_free_ char *device = NULL;
@@ -158,6 +176,10 @@ static int parse_argv(int argc, char *argv[]) {
arg_machine_id = true;
break;
case ARG_EARLY:
arg_early = true;
break;
case '?':
return -EINVAL;
@@ -165,15 +187,18 @@ static int parse_argv(int argc, char *argv[]) {
assert_not_reached();
}
if (arg_file_system && arg_machine_id)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "--file-system= and --machine-id may not be combined.");
if (!!arg_file_system + arg_machine_id > 1)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "--file-system=, --machine-id may not be combined.");
if (arg_pcr_index != UINT_MAX && arg_nvpcr_name)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "--pcr= and --nvpcr= may not be combined.");
r = sd_varlink_invocation(SD_VARLINK_ALLOW_ACCEPT);
if (r < 0)
return log_error_errno(r, "Failed to check if invoked in Varlink mode: %m");
if (r > 0)
arg_varlink = true;
else if (arg_pcr_index == UINT_MAX)
else if (arg_pcr_index == UINT_MAX && !arg_nvpcr_name)
arg_pcr_index = (arg_file_system || arg_machine_id) ?
TPM2_PCR_SYSTEM_IDENTITY : /* → PCR 15 */
TPM2_PCR_KERNEL_BOOT; /* → PCR 11 */
@@ -198,7 +223,34 @@ static int determine_banks(Tpm2Context *c, unsigned target_pcr_nr) {
return 0;
}
static int extend_now(unsigned pcr, const void *data, size_t size, Tpm2UserspaceEventType event) {
static int escape_and_truncate_data(const void *data, size_t size, char **ret) {
_cleanup_free_ char *safe = NULL;
assert(data || size == 0);
if (size > EXTENSION_STRING_SAFE_LIMIT) {
safe = cescape_length(data, EXTENSION_STRING_SAFE_LIMIT);
if (!safe)
return -ENOMEM;
if (!strextend(&safe, "..."))
return -ENOMEM;
} else {
safe = cescape_length(data, size);
if (!safe)
return -ENOMEM;
}
*ret = TAKE_PTR(safe);
return 0;
}
static int extend_pcr_now(
unsigned pcr,
const void *data,
size_t size,
Tpm2UserspaceEventType event) {
_cleanup_(tpm2_context_unrefp) Tpm2Context *c = NULL;
int r;
@@ -218,18 +270,8 @@ static int extend_now(unsigned pcr, const void *data, size_t size, Tpm2Userspace
return log_oom();
_cleanup_free_ char *safe = NULL;
if (size > EXTENSION_STRING_SAFE_LIMIT) {
safe = cescape_length(data, EXTENSION_STRING_SAFE_LIMIT);
if (!safe)
return log_oom();
if (!strextend(&safe, "..."))
return log_oom();
} else {
safe = cescape_length(data, size);
if (!safe)
return log_oom();
}
if (escape_and_truncate_data(data, size, &safe) < 0)
return log_oom();
log_debug("Measuring '%s' into PCR index %u, banks %s.", safe, pcr, joined_banks);
@@ -247,8 +289,55 @@ static int extend_now(unsigned pcr, const void *data, size_t size, Tpm2Userspace
return 0;
}
static int extend_nvpcr_now(
const char *name,
const void *data,
size_t size,
Tpm2UserspaceEventType event) {
_cleanup_(tpm2_context_unrefp) Tpm2Context *c = NULL;
int r;
r = tpm2_context_new_or_warn(arg_tpm2_device, &c);
if (r < 0)
return r;
_cleanup_free_ char *safe = NULL;
if (escape_and_truncate_data(data, size, &safe) < 0)
return log_oom();
log_debug("Measuring '%s' into NvPCR index '%s'.", safe, name);
r = tpm2_nvpcr_extend_bytes(c, /* session= */ NULL, name, &IOVEC_MAKE(data, size), /* secret= */ NULL, event, safe);
if (r == -ENETDOWN) {
/* NvPCR is not initialized yet. Let's do this now. */
_cleanup_(iovec_done_erase) struct iovec anchor_secret = {};
r = tpm2_nvpcr_acquire_anchor_secret(&anchor_secret, /* sync_secondary= */ !arg_early);
if (r < 0)
return r;
r = tpm2_nvpcr_initialize(c, /* session= */ NULL, name, &anchor_secret);
if (r < 0)
return log_error_errno(r, "Failed to extend NvPCR index '%s' with anchor secret: %m", name);
r = tpm2_nvpcr_extend_bytes(c, /* session= */ NULL, name, &IOVEC_MAKE(data, size), /* secret= */ NULL, event, safe);
}
if (r < 0)
return log_error_errno(r, "Could not extend NvPCR: %m");
log_struct(LOG_INFO,
"MESSAGE_ID=" SD_MESSAGE_TPM_NVPCR_EXTEND_STR,
LOG_MESSAGE("Extended NvPCR index '%s' with '%s'.", name, safe),
"MEASURING=%s", safe,
"NVPCR=%u", name);
return 0;
}
typedef struct MethodExtendParameters {
unsigned pcr;
const char *nvpcr;
const char *text;
struct iovec data;
} MethodExtendParameters;
@@ -262,9 +351,10 @@ static void method_extend_parameters_done(MethodExtendParameters *p) {
static int vl_method_extend(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
static const sd_json_dispatch_field dispatch_table[] = {
{ "pcr", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint, offsetof(MethodExtendParameters, pcr), SD_JSON_MANDATORY },
{ "text", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, offsetof(MethodExtendParameters, text), 0 },
{ "data", SD_JSON_VARIANT_STRING, json_dispatch_unbase64_iovec, offsetof(MethodExtendParameters, data), 0 },
{ "pcr", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint, offsetof(MethodExtendParameters, pcr), 0 },
{ "nvpcr", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, offsetof(MethodExtendParameters, nvpcr), 0 },
{ "text", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, offsetof(MethodExtendParameters, text), 0 },
{ "data", SD_JSON_VARIANT_STRING, json_dispatch_unbase64_iovec, offsetof(MethodExtendParameters, data), 0 },
{}
};
_cleanup_(method_extend_parameters_done) MethodExtendParameters p = {
@@ -278,19 +368,38 @@ static int vl_method_extend(sd_varlink *link, sd_json_variant *parameters, sd_va
if (r != 0)
return r;
if (!TPM2_PCR_INDEX_VALID(p.pcr))
if (p.nvpcr) {
/* Specifying both nvpcr name and pcr doesn't make sense */
if (p.pcr != UINT_MAX)
return sd_varlink_error_invalid_parameter_name(link, "nvpcr");
if (!tpm2_nvpcr_name_is_valid(p.nvpcr))
return sd_varlink_error_invalid_parameter_name(link, "nvpcr");
} else if (!TPM2_PCR_INDEX_VALID(p.pcr))
return sd_varlink_error_invalid_parameter_name(link, "pcr");
struct iovec *extend_iovec, text_iovec;
if (p.text) {
/* Specifying both the text string and the binary data is not allowed */
if (p.data.iov_base)
return sd_varlink_error_invalid_parameter_name(link, "data");
r = extend_now(p.pcr, p.text, strlen(p.text), _TPM2_USERSPACE_EVENT_TYPE_INVALID);
text_iovec = IOVEC_MAKE_STRING(p.text);
extend_iovec = &text_iovec;
} else if (p.data.iov_base)
r = extend_now(p.pcr, p.data.iov_base, p.data.iov_len, _TPM2_USERSPACE_EVENT_TYPE_INVALID);
extend_iovec = &p.data;
else
return sd_varlink_error_invalid_parameter_name(link, "text");
if (p.nvpcr) {
r = extend_nvpcr_now(p.nvpcr, extend_iovec->iov_base, extend_iovec->iov_len, _TPM2_USERSPACE_EVENT_TYPE_INVALID);
if (r == -ENOENT)
return sd_varlink_error(link, "io.systemd.PCRExtend.NoSuchNvPCR", NULL);
} else
r = extend_pcr_now(p.pcr, extend_iovec->iov_base, extend_iovec->iov_len, _TPM2_USERSPACE_EVENT_TYPE_INVALID);
if (r < 0)
return r;
@@ -354,7 +463,6 @@ static int run(int argc, char *argv[]) {
return r;
event = TPM2_EVENT_MACHINE_ID;
} else {
if (optind+1 != argc)
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Expected a single argument.");
@@ -386,9 +494,12 @@ static int run(int argc, char *argv[]) {
return EXIT_SUCCESS;
}
r = extend_now(arg_pcr_index, word, strlen(word), event);
if (arg_nvpcr_name)
r = extend_nvpcr_now(arg_nvpcr_name, word, strlen(word), event);
else
r = extend_pcr_now(arg_pcr_index, word, strlen(word), event);
if (r < 0)
return log_error_errno(r, "Failed to create TPM2 context: %m");
return r;
return EXIT_SUCCESS;
}

6
src/shared/varlink-io.systemd.PCRExtend.c
View File

@@ -6,14 +6,18 @@ static SD_VARLINK_DEFINE_METHOD(
Extend,
SD_VARLINK_FIELD_COMMENT("PCR number to extend, in range of 0…23"),
SD_VARLINK_DEFINE_INPUT(pcr, SD_VARLINK_INT, 0),
SD_VARLINK_DEFINE_INPUT(nvpcr, SD_VARLINK_INT, SD_VARLINK_NULLABLE),
SD_VARLINK_FIELD_COMMENT("Text string to measure. (Specify either this, or the 'data' field below, not both)"),
SD_VARLINK_DEFINE_INPUT(text, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
SD_VARLINK_FIELD_COMMENT("Binary data to measure, encoded in Base64. (Specify either this, or the 'text' field above, not both)"),
SD_VARLINK_DEFINE_INPUT(data, SD_VARLINK_STRING, SD_VARLINK_NULLABLE));
static SD_VARLINK_DEFINE_ERROR(NoSuchNvPCR);
SD_VARLINK_DEFINE_INTERFACE(
io_systemd_PCRExtend,
"io.systemd.PCRExtend",
SD_VARLINK_INTERFACE_COMMENT("TPM PCR Extension APIs"),
SD_VARLINK_SYMBOL_COMMENT("Measure some text or binary data into a PCR"),
&vl_method_Extend);
&vl_method_Extend,
&vl_error_NoSuchNvPCR);

2
src/systemd/sd-messages.h
View File

@@ -272,6 +272,8 @@ _SD_BEGIN_DECLARATIONS;
#define SD_MESSAGE_TPM_PCR_EXTEND SD_ID128_MAKE(3f,7d,5e,f3,e5,4f,43,02,b4,f0,b1,43,bb,27,0c,ab)
#define SD_MESSAGE_TPM_PCR_EXTEND_STR SD_ID128_MAKE_STR(3f,7d,5e,f3,e5,4f,43,02,b4,f0,b1,43,bb,27,0c,ab)
#define SD_MESSAGE_TPM_NVPCR_EXTEND SD_ID128_MAKE(4c,2e,46,d2,66,a7,47,c6,ac,14,60,aa,54,48,4f,a7)
#define SD_MESSAGE_TPM_NVPCR_EXTEND_STR SD_ID128_MAKE_STR(4c,2e,46,d2,66,a7,47,c6,ac,14,60,aa,54,48,4f,a7)
#define SD_MESSAGE_MEMORY_TRIM SD_ID128_MAKE(f9,b0,be,46,5a,d5,40,d0,85,0a,d3,21,72,d5,7c,21)
#define SD_MESSAGE_MEMORY_TRIM_STR SD_ID128_MAKE_STR(f9,b0,be,46,5a,d5,40,d0,85,0a,d3,21,72,d5,7c,21)