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-rw-r--r--Documentation/security/vboot/measured_boot.md83
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diff --git a/Documentation/security/vboot/measured_boot.md b/Documentation/security/vboot/measured_boot.md
index 3ec3729edf..45d66dd2d2 100644
--- a/Documentation/security/vboot/measured_boot.md
+++ b/Documentation/security/vboot/measured_boot.md
@@ -1,6 +1,8 @@
# Measured Boot
coreboot measured boot is implemented as Google Verified Boot extension. This
-means in order to use it, vboot needs to be available for your platform.
+means in order to use it, vboot needs to be available for your platform. The
+goal of this implementation is to implement an easy to understand and
+transparent measured boot mechanism.
## IBB/CRTM
The "Initial Boot Block" or "Core Root of Trust for Measurement" is the first
@@ -21,10 +23,85 @@ measured boot extension because of platform constraints.
The "Static Root of Trust for Measurement" is the easiest way doing measurements
by measuring code before it is loaded.
+### Measurements
+SRTM mode measurements are done starting with the IBB as root of trust.
+Only CBFS contents are measured at the moment.
+
+#### CBFS files (stages, blobs)
+* CBFS data is measured as raw data before decompression happens.
+* CBFS header is excluded from measurements.
+* Measurements are stored in PCR 2.
+
+#### Runtime Data
+* CBFS data which changes by external input dynamically. Never stays the same.
+* It is identified by VBOOT_MEASURED_BOOT_RUNTIME_DATA kconfig option and
+ measured into a different PCR 3 in order to avoid PCR pre-calculation issues.
+
![][srtm]
[srtm]: srtm.png
+### TCPA eventlog
+coreboot makes use of its own TCPA log implementation. Normally the eventlog
+specification can be found via the TCG homepage:
+
+[UEFI Specification](https://trustedcomputinggroup.org/resource/tcg-efi-platform-specification/)
+
+[BIOS Specification](https://www.trustedcomputinggroup.org/wp-content/uploads/TCG_PCClientImplementation_1-21_1_00.pdf)
+
+Both of them are not representing firmware measurements in a generalized way.
+Therefore we have to implement our own solution.
+
+We decided to provide an easy to understand TCPA log which can be read out
+from the operating system and firmware itself.
+
+#### Table Format
+The first column describes the PCR index used for measurement.
+The second column is the hash of the raw data. The third column contains
+the hash algorithm used in the operation. The last column provides
+information about what is measured. First the namespace from where the data
+came from, CBFS or FMAP, then the name used to look up the data
+(region or file name).
+
+#### Example:
+```bash
+PCR-2 e8f2b57c9ec5ea06d1bbd3240a753974d4c3e7c8cd305c20a8ea26eed906dc89 SHA256 [FMAP: COREBOOT CBFS: bootblock]
+PCR-2 309a5fcb231d3a39127de2521792f332f9a69e05675ec52535d2dcded756dc19 SHA256 [FMAP: COREBOOT CBFS: fallback/verstage]
+PCR-2 0fbba07a833d4dcfc7024eaf313661a0ba8f80a05c6d29b8801c612e10e60dee SHA256 [FMAP: RO_VPD]
+PCR-2 431681113ed44cbf6f68a12c6e5687e901052f1d728a4777b2ad36e559962047 SHA256 [FMAP: GBB]
+PCR-2 f47a8ec3e9aff2318d896942282ad4fe37d6391c82914f54a5da8a37de1300c6 SHA256 [FMAP: SI_DESC]
+PCR-3 237f6f567f8597dbdff0a00690d34d21616af0dbe434b9a2d432b136c012765f SHA256 [FMAP: SI_ME]
+PCR-2 7d2c7ac4888bfd75cd5f56e8d61f69595121183afc81556c876732fd3782c62f SHA256 [FMAP: SI_GBE]
+PCR-0 62571891215b4efc1ceab744ce59dd0b66ea6f73 SHA1 [GBB flags]
+PCR-1 a66c8c2cda246d332d0c2025b6266e1e23c89410051002f46bfad1c9265f43d0 SHA256 [GBB HWID]
+PCR-2 ceca357524caf8fc73f5fa130f05a75293031962af884e18990d281eb259f5ff SHA256 [FMAP: FW_MAIN_B CBFS: fallback/romstage]
+PCR-2 548a097604e0a975de76f98b04c7f0b0ddec03883dd69179e47a784704a1c571 SHA256 [FMAP: FW_MAIN_B CBFS: fspm.bin]
+PCR-2 1e86b27008818244c221df2436b0113bd20a86ec6ec9d8259defe87f45d2f604 SHA256 [FMAP: FW_MAIN_B CBFS: spd2.bin]
+PCR-2 05d78005fcfc9edd4ca5625f11b1f49991d17bdb7cee33b72e722bc785db55ae SHA256 [FMAP: FW_MAIN_B CBFS: fallback/postcar]
+PCR-2 c13e95829af12a584046f1a6f3e1f6e4af691209324cfeeec573633399384141 SHA256 [FMAP: FW_MAIN_B CBFS: fallback/ramstage]
+PCR-2 a6ec2761b597abd252dba2a7237140ef4a5a8e0d47cad8afb65fa16314413401 SHA256 [FMAP: FW_MAIN_B CBFS: cpu_microcode_blob.bin]
+PCR-2 c81ffa40df0b6cd6cfde4f476d452a1f6f2217bc96a3b98a4fa4a037ee7039cf SHA256 [FMAP: FW_MAIN_B CBFS: fsps.bin]
+PCR-2 4e95f57bbf3c6627eb1c72be9c48df3aaa8e6da4f5f63d85e554cf6803505609 SHA256 [FMAP: FW_MAIN_B CBFS: vbt.bin]
+PCR-3 b7663f611ecf8637a59d72f623ae92a456c30377d4175e96021c85362f0323c8 SHA256 [FMAP: RW_NVRAM]
+PCR-2 178561f046e2adbc621b12b47d65be82756128e2a1fe5116b53ef3637da700e8 SHA256 [FMAP: FW_MAIN_B CBFS: fallback/dsdt.aml]
+PCR-2 091706f5fce3eb123dd9b96c15a9dcc459a694f5e5a86e7bf6064b819a8575c7 SHA256 [FMAP: FW_MAIN_B CBFS: fallback/payload]
+```
+
+#### Dump TCPA eventlog in the OS:
+```bash
+cbmem -L
+```
+
+#### Get CBFS file and print the hash
+```bash
+cbfstool coreboot.rom extract -r COREBOOT -n fallback/romstage -U -f /dev/stdout | sha256sum
+```
+
+#### Get FMAP partition and print the hash
+```bash
+cbfstool coreboot.rom read -n SI_ME -f /dev/stdout | sha256sum
+```
+
## DRTM Mode
The "Dynamic Root of Trust for Measurement" is realised by platform features
like Intel TXT or Boot Guard. The features provide a way of loading a signed
@@ -42,17 +119,21 @@ PCR-7 are left empty.
### PCR-0
_Hash:_ SHA1
+
_Description:_ Google VBoot GBB flags.
### PCR-1
_Hash:_ SHA1/SHA256
+
_Description:_ Google VBoot GBB HWID.
### PCR-2
_Hash:_ SHA1/SHA256
+
_Description:_ Core Root of Trust for Measurement which includes all stages,
data and blobs.
### PCR-3
_Hash:_ SHA1/SHA256
+
_Description:_ Runtime data like hwinfo.hex or MRC cache.