[ Upstream commit 7f3d176f5f ]
Require that the TCG_PCR_EVENT2.digests.count value strictly matches the
value of TCG_EfiSpecIdEvent.numberOfAlgorithms in the event field of the
TCG_PCClientPCREvent event log header. Also require that
TCG_EfiSpecIdEvent.numberOfAlgorithms is non-zero.
The TCG PC Client Platform Firmware Profile Specification section 9.1
(Family "2.0", Level 00 Revision 1.04) states:
For each Hash algorithm enumerated in the TCG_PCClientPCREvent entry,
there SHALL be a corresponding digest in all TCG_PCR_EVENT2 structures.
Note: This includes EV_NO_ACTION events which do not extend the PCR.
Section 9.4.5.1 provides this description of
TCG_EfiSpecIdEvent.numberOfAlgorithms:
The number of Hash algorithms in the digestSizes field. This field MUST
be set to a value of 0x01 or greater.
Enforce these restrictions, as required by the above specification, in
order to better identify and ignore invalid sequences of bytes at the
end of an otherwise valid TPM2 event log. Firmware doesn't always have
the means necessary to inform the kernel of the actual event log size so
the kernel's event log parsing code should be stringent when parsing the
event log for resiliency against firmware bugs. This is true, for
example, when firmware passes the event log to the kernel via a reserved
memory region described in device tree.
POWER and some ARM systems use the "linux,sml-base" and "linux,sml-size"
device tree properties to describe the memory region used to pass the
event log from firmware to the kernel. Unfortunately, the
"linux,sml-size" property describes the size of the entire reserved
memory region rather than the size of the event long within the memory
region and the event log format does not include information describing
the size of the event log.
tpm_read_log_of(), in drivers/char/tpm/eventlog/of.c, is where the
"linux,sml-size" property is used. At the end of that function,
log->bios_event_log_end is pointing at the end of the reserved memory
region. That's typically 0x10000 bytes offset from "linux,sml-base",
depending on what's defined in the device tree source.
The firmware event log only fills a portion of those 0x10000 bytes and
the rest of the memory region should be zeroed out by firmware. Even in
the case of a properly zeroed bytes in the remainder of the memory
region, the only thing allowing the kernel's event log parser to detect
the end of the event log is the following conditional in
__calc_tpm2_event_size():
if (event_type == 0 && event_field->event_size == 0)
size = 0;
If that wasn't there, __calc_tpm2_event_size() would think that a 16
byte sequence of zeroes, following an otherwise valid event log, was
a valid event.
However, problems can occur if a single bit is set in the offset
corresponding to either the TCG_PCR_EVENT2.eventType or
TCG_PCR_EVENT2.eventSize fields, after the last valid event log entry.
This could confuse the parser into thinking that an additional entry is
present in the event log and exposing this invalid entry to userspace in
the /sys/kernel/security/tpm0/binary_bios_measurements file. Such
problems have been seen if firmware does not fully zero the memory
region upon a warm reboot.
This patch significantly raises the bar on how difficult it is for
stale/invalid memory to confuse the kernel's event log parser but
there's still, ultimately, a reliance on firmware to properly initialize
the remainder of the memory region reserved for the event log as the
parser cannot be expected to detect a stale but otherwise properly
formatted firmware event log entry.
Fixes: fd5c78694f ("tpm: fix handling of the TPM 2.0 event logs")
Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 7dfc06a0f2 ]
It is possible that the first event in the event log is not actually a
log header at all, but rather a normal event. This leads to the cast in
__calc_tpm2_event_size being an invalid conversion, which means that
the values read are effectively garbage. Depending on the first event's
contents, this leads either to apparently normal behaviour, a crash or
a freeze.
While this behaviour of the firmware is not in accordance with the
TCG Client EFI Specification, this happens on a Dell Precision 5510
with the TPM enabled but hidden from the OS ("TPM On" disabled, state
otherwise untouched). The EFI firmware claims that the TPM is present
and active and that it supports the TCG 2.0 event log format.
Fortunately, this can be worked around by simply checking the header
of the first event and the event log header signature itself.
Commit b4f1874c62 ("tpm: check event log version before reading final
events") addressed a similar issue also found on Dell models.
Fixes: 6b03261902 ("efi: Attempt to get the TCG2 event log in the boot stub")
Signed-off-by: Fabian Vogt <fvogt@suse.de>
Link: https://lore.kernel.org/r/1927248.evlx2EsYKh@linux-e202.suse.de
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1165773
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
If __calc_tpm2_event_size() fails to parse an event it will return 0,
resulting tpm2_calc_event_log_size() returning -1. Currently there is
no check of this return value, and 'efi_tpm_final_log_size' can end up
being set to this negative value resulting in a crash like this one:
BUG: unable to handle page fault for address: ffffbc8fc00866ad
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
RIP: 0010:memcpy_erms+0x6/0x10
Call Trace:
tpm_read_log_efi()
tpm_bios_log_setup()
tpm_chip_register()
tpm_tis_core_init.cold.9+0x28c/0x466
tpm_tis_plat_probe()
platform_drv_probe()
...
Also __calc_tpm2_event_size() returns a size of 0 when it fails
to parse an event, so update function documentation to reflect this.
The root cause of the issue that caused the failure of event parsing
in this case is resolved by Peter Jone's patchset dealing with large
event logs where crossing over a page boundary causes the page with
the event count to be unmapped.
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Lyude Paul <lyude@redhat.com>
Cc: Matthew Garrett <mjg59@google.com>
Cc: Octavian Purdila <octavian.purdila@intel.com>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Talbert <swt@techie.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: linux-integrity@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: c46f340569 ("tpm: Reserve the TPM final events table")
Link: https://lkml.kernel.org/r/20191002165904.8819-6-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Some machines generate a lot of event log entries. When we're
iterating over them, the code removes the old mapping and adds a
new one, so once we cross the page boundary we're unmapping the page
with the count on it. Hilarity ensues.
This patch keeps the info from the header in local variables so we don't
need to access that page again or keep track of if it's mapped.
Tested-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Matthew Garrett <mjg59@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: Dave Young <dyoung@redhat.com>
Cc: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Octavian Purdila <octavian.purdila@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Talbert <swt@techie.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Cc: linux-integrity@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: 44038bc514 ("tpm: Abstract crypto agile event size calculations")
Link: https://lkml.kernel.org/r/20191002165904.8819-4-ard.biesheuvel@linaro.org
[ Minor edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
UEFI systems provide a boot services protocol for obtaining the TPM
event log, but this is unusable after ExitBootServices() is called.
Unfortunately ExitBootServices() itself triggers additional TPM events
that then can't be obtained using this protocol. The platform provides a
mechanism for the OS to obtain these events by recording them to a
separate UEFI configuration table which the OS can then map.
Unfortunately this table isn't self describing in terms of providing its
length, so we need to parse the events inside it to figure out how long
it is. Since the table isn't mapped at this point, we need to extend the
length calculation function to be able to map the event as it goes
along.
(Fixes by Bartosz Szczepanek <bsz@semihalf.com>)
Signed-off-by: Matthew Garrett <mjg59@google.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Bartosz Szczepanek <bsz@semihalf.com>
Tested-by: Bartosz Szczepanek <bsz@semihalf.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
We need to calculate the size of crypto agile events in multiple
locations, including in the EFI boot stub. The easiest way to do this is
to put it in a header file as an inline and leave a wrapper to ensure we
don't end up with multiple copies of it embedded in the existing code.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Reviewed-by: Bartosz Szczepanek <bsz@semihalf.com>
Tested-by: Bartosz Szczepanek <bsz@semihalf.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Rename tpm2_* to tpm_* and move the definitions to include/linux/tpm.h so
that these can be used by other kernel subsystems (e.g. IMA).
Also, set the length of the digest array in tpm_digest to a new constant
named TPM_MAX_DIGEST_SIZE, equal to SHA512_DIGEST_SIZE.
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
TCG defines two structures, TCG_EfiSpecIDEventStruct and TCG_PCR_EVENT2,
which contain variable-sized arrays in the middle of the definition.
Since these structures are not suitable for type casting, this patch
removes structure members after the variable-sized arrays and adds the
_head suffix to the structure name, to indicate that the renamed structures
do not contain all fields defined by TCG.
Lastly, given that variable-sized arrays are now in the last position, and
given that the size of the arrays cannot be determined in advance, this
patch also sets the size of those arrays to zero and removes the definition
of TPM2_ACTIVE_PCR_BANKS.
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Nayna Jain <nayna@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Although defined as part of the TCG EFI specification, we add these
definitions here so that any event log provider may reference them.
Signed-off-by: Thiebaud Weksteen <tweek@google.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
The generic definitions of data structures in tpm_eventlog.h are
required by other part of the kernel (namely, the EFI stub).
Signed-off-by: Thiebaud Weksteen <tweek@google.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Javier Martinez Canillas <javierm@redhat.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tyler Hicks