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lib/tpm2: do not create all NVRAM spaces with the same set of attributes 

The TPM spaces created by the RO need to have different attributes
depending on the space's use. The firmware rollback counter and MRC
hash spaces are created by the RO code and need to be protected at the
highest level: it should be impossible to delete or modify the space
once the RO exits, and it is how it is done before this patch.

The rest of the spaces should be possible to modify or recreate even
after the RO exits. Let's use different set of NVRAM space attributes
to achieve that, and set the 'pcr0 unchanged' policy only for the
firmware counter and MRC cache spaces.

The definitions of the attributes can be found in "Trusted Platform
Module Library Part 2: Structures", Revision 01.16, section "13.2
TPMA_NV (NV Index Attributes)."

CQ-DEPEND=CL:410127
BRANCH=none
BUG=chrome-os-partner:59651
TEST=verified that the reef system boots fine in both normal and
     recovery modes; using tpmc confirmed that firmware, kernel and
     MRC cache NVRAM spaces are readable in both and writeable only in
     recovery mode.

Change-Id: I1a1d2459f56ec929c9a92b39175888b8d1bcda55
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://review.coreboot.org/17388
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Andrey Pronin <apronin@chromium.org>
This commit is contained in:
Vadim Bendebury 2016-11-11 09:36:50 -08:00
parent c446704e71
commit 289ee8f0e9
1 changed files with 41 additions and 21 deletions
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56
src/lib/tpm2_tlcl.c
View File

@ -4,6 +4,7 @@
* found in the LICENSE file.
*/
#include <antirollback.h>
#include <arch/early_variables.h>
#include <console/console.h>
#include <endian.h>
@ -299,14 +300,23 @@ uint32_t tlcl_define_space(uint32_t space_index, size_t space_size)
struct tpm2_nv_define_space_cmd nvds_cmd;
struct tpm2_response *response;
/*
* This policy digest was obtained using TPM2_PolicyPCR selecting only
* PCR_0 with a value of all zeros.
* Different sets of NVRAM space attributes apply to the "ro" spaces,
* i.e. those which should not be possible to delete or modify once
* the RO exits, and the rest of the NVRAM spaces.
*/
const uint8_t pcr0_unchanged_policy[] = {
0x09, 0x93, 0x3C, 0xCE, 0xEB, 0xB4, 0x41, 0x11,
0x18, 0x81, 0x1D, 0xD4, 0x47, 0x78, 0x80, 0x08,
0x88, 0x86, 0x62, 0x2D, 0xD7, 0x79, 0x94, 0x46,
0x62, 0x26, 0x68, 0x8E, 0xEE, 0xE6, 0x6A, 0xA1
const TPMA_NV ro_space_attributes = {
.TPMA_NV_PPWRITE = 1,
.TPMA_NV_AUTHREAD = 1,
.TPMA_NV_PPREAD = 1,
.TPMA_NV_PLATFORMCREATE = 1,
.TPMA_NV_WRITE_STCLEAR = 1,
.TPMA_NV_POLICY_DELETE = 1,
};
const TPMA_NV default_space_attributes = {
.TPMA_NV_PPWRITE = 1,
.TPMA_NV_AUTHREAD = 1,
.TPMA_NV_PPREAD = 1,
.TPMA_NV_PLATFORMCREATE = 1,
};
/* Prepare the define space command structure. */
@ -316,21 +326,31 @@ uint32_t tlcl_define_space(uint32_t space_index, size_t space_size)
nvds_cmd.publicInfo.nvIndex = HR_NV_INDEX + space_index;
nvds_cmd.publicInfo.nameAlg = TPM_ALG_SHA256;
/* Attributes common for all NVRAM spaces used by firmware. */
nvds_cmd.publicInfo.attributes.TPMA_NV_PPWRITE = 1;
nvds_cmd.publicInfo.attributes.TPMA_NV_AUTHREAD = 1;
nvds_cmd.publicInfo.attributes.TPMA_NV_PPREAD = 1;
nvds_cmd.publicInfo.attributes.TPMA_NV_PLATFORMCREATE = 1;
nvds_cmd.publicInfo.attributes.TPMA_NV_WRITE_STCLEAR = 1;
nvds_cmd.publicInfo.attributes.TPMA_NV_POLICY_DELETE = 1;
/* RO only NV spaces should be impossible to destroy. */
if ((space_index == FIRMWARE_NV_INDEX) ||
(space_index == REC_HASH_NV_INDEX)) {
/*
* Use policy digest based on default pcr0 value. This makes sure that
* the space can not be deleted as soon as PCR0 value has been
* extended from default.
* This policy digest was obtained using TPM2_PolicyPCR
* selecting only PCR_0 with a value of all zeros.
*/
const uint8_t pcr0_unchanged_policy[] = {
0x09, 0x93, 0x3C, 0xCE, 0xEB, 0xB4, 0x41, 0x11,
0x18, 0x81, 0x1D, 0xD4, 0x47, 0x78, 0x80, 0x08,
0x88, 0x86, 0x62, 0x2D, 0xD7, 0x79, 0x94, 0x46,
0x62, 0x26, 0x68, 0x8E, 0xEE, 0xE6, 0x6A, 0xA1
};
nvds_cmd.publicInfo.attributes = ro_space_attributes;
/*
* Use policy digest based on default pcr0 value. This makes
* sure that the space can not be deleted as soon as PCR0
* value has been extended from default.
*/
nvds_cmd.publicInfo.authPolicy.t.buffer = pcr0_unchanged_policy;
nvds_cmd.publicInfo.authPolicy.t.size = sizeof(pcr0_unchanged_policy);
} else {
nvds_cmd.publicInfo.attributes = default_space_attributes;
}
response = tpm_process_command(TPM2_NV_DefineSpace, &nvds_cmd);
printk(BIOS_INFO, "%s: response is %x\n",