summaryrefslogtreecommitdiffstats
path: root/Documentation/intel_txt.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/intel_txt.txt')
-rw-r--r--Documentation/intel_txt.txt210
1 files changed, 0 insertions, 210 deletions
diff --git a/Documentation/intel_txt.txt b/Documentation/intel_txt.txt
deleted file mode 100644
index 849de1a..0000000
--- a/Documentation/intel_txt.txt
+++ /dev/null
@@ -1,210 +0,0 @@
-Intel(R) TXT Overview:
-=====================
-
-Intel's technology for safer computing, Intel(R) Trusted Execution
-Technology (Intel(R) TXT), defines platform-level enhancements that
-provide the building blocks for creating trusted platforms.
-
-Intel TXT was formerly known by the code name LaGrande Technology (LT).
-
-Intel TXT in Brief:
-o Provides dynamic root of trust for measurement (DRTM)
-o Data protection in case of improper shutdown
-o Measurement and verification of launched environment
-
-Intel TXT is part of the vPro(TM) brand and is also available some
-non-vPro systems. It is currently available on desktop systems
-based on the Q35, X38, Q45, and Q43 Express chipsets (e.g. Dell
-Optiplex 755, HP dc7800, etc.) and mobile systems based on the GM45,
-PM45, and GS45 Express chipsets.
-
-For more information, see http://www.intel.com/technology/security/.
-This site also has a link to the Intel TXT MLE Developers Manual,
-which has been updated for the new released platforms.
-
-Intel TXT has been presented at various events over the past few
-years, some of which are:
- LinuxTAG 2008:
- http://www.linuxtag.org/2008/en/conf/events/vp-donnerstag.html
- TRUST2008:
- http://www.trust-conference.eu/downloads/Keynote-Speakers/
- 3_David-Grawrock_The-Front-Door-of-Trusted-Computing.pdf
- IDF, Shanghai:
- http://www.prcidf.com.cn/index_en.html
- IDFs 2006, 2007 (I'm not sure if/where they are online)
-
-Trusted Boot Project Overview:
-=============================
-
-Trusted Boot (tboot) is an open source, pre-kernel/VMM module that
-uses Intel TXT to perform a measured and verified launch of an OS
-kernel/VMM.
-
-It is hosted on SourceForge at http://sourceforge.net/projects/tboot.
-The mercurial source repo is available at http://www.bughost.org/
-repos.hg/tboot.hg.
-
-Tboot currently supports launching Xen (open source VMM/hypervisor
-w/ TXT support since v3.2), and now Linux kernels.
-
-
-Value Proposition for Linux or "Why should you care?"
-=====================================================
-
-While there are many products and technologies that attempt to
-measure or protect the integrity of a running kernel, they all
-assume the kernel is "good" to begin with. The Integrity
-Measurement Architecture (IMA) and Linux Integrity Module interface
-are examples of such solutions.
-
-To get trust in the initial kernel without using Intel TXT, a
-static root of trust must be used. This bases trust in BIOS
-starting at system reset and requires measurement of all code
-executed between system reset through the completion of the kernel
-boot as well as data objects used by that code. In the case of a
-Linux kernel, this means all of BIOS, any option ROMs, the
-bootloader and the boot config. In practice, this is a lot of
-code/data, much of which is subject to change from boot to boot
-(e.g. changing NICs may change option ROMs). Without reference
-hashes, these measurement changes are difficult to assess or
-confirm as benign. This process also does not provide DMA
-protection, memory configuration/alias checks and locks, crash
-protection, or policy support.
-
-By using the hardware-based root of trust that Intel TXT provides,
-many of these issues can be mitigated. Specifically: many
-pre-launch components can be removed from the trust chain, DMA
-protection is provided to all launched components, a large number
-of platform configuration checks are performed and values locked,
-protection is provided for any data in the event of an improper
-shutdown, and there is support for policy-based execution/verification.
-This provides a more stable measurement and a higher assurance of
-system configuration and initial state than would be otherwise
-possible. Since the tboot project is open source, source code for
-almost all parts of the trust chain is available (excepting SMM and
-Intel-provided firmware).
-
-How Does it Work?
-=================
-
-o Tboot is an executable that is launched by the bootloader as
- the "kernel" (the binary the bootloader executes).
-o It performs all of the work necessary to determine if the
- platform supports Intel TXT and, if so, executes the GETSEC[SENTER]
- processor instruction that initiates the dynamic root of trust.
- - If tboot determines that the system does not support Intel TXT
- or is not configured correctly (e.g. the SINIT AC Module was
- incorrect), it will directly launch the kernel with no changes
- to any state.
- - Tboot will output various information about its progress to the
- terminal, serial port, and/or an in-memory log; the output
- locations can be configured with a command line switch.
-o The GETSEC[SENTER] instruction will return control to tboot and
- tboot then verifies certain aspects of the environment (e.g. TPM NV
- lock, e820 table does not have invalid entries, etc.).
-o It will wake the APs from the special sleep state the GETSEC[SENTER]
- instruction had put them in and place them into a wait-for-SIPI
- state.
- - Because the processors will not respond to an INIT or SIPI when
- in the TXT environment, it is necessary to create a small VT-x
- guest for the APs. When they run in this guest, they will
- simply wait for the INIT-SIPI-SIPI sequence, which will cause
- VMEXITs, and then disable VT and jump to the SIPI vector. This
- approach seemed like a better choice than having to insert
- special code into the kernel's MP wakeup sequence.
-o Tboot then applies an (optional) user-defined launch policy to
- verify the kernel and initrd.
- - This policy is rooted in TPM NV and is described in the tboot
- project. The tboot project also contains code for tools to
- create and provision the policy.
- - Policies are completely under user control and if not present
- then any kernel will be launched.
- - Policy action is flexible and can include halting on failures
- or simply logging them and continuing.
-o Tboot adjusts the e820 table provided by the bootloader to reserve
- its own location in memory as well as to reserve certain other
- TXT-related regions.
-o As part of its launch, tboot DMA protects all of RAM (using the
- VT-d PMRs). Thus, the kernel must be booted with 'intel_iommu=on'
- in order to remove this blanket protection and use VT-d's
- page-level protection.
-o Tboot will populate a shared page with some data about itself and
- pass this to the Linux kernel as it transfers control.
- - The location of the shared page is passed via the boot_params
- struct as a physical address.
-o The kernel will look for the tboot shared page address and, if it
- exists, map it.
-o As one of the checks/protections provided by TXT, it makes a copy
- of the VT-d DMARs in a DMA-protected region of memory and verifies
- them for correctness. The VT-d code will detect if the kernel was
- launched with tboot and use this copy instead of the one in the
- ACPI table.
-o At this point, tboot and TXT are out of the picture until a
- shutdown (S<n>)
-o In order to put a system into any of the sleep states after a TXT
- launch, TXT must first be exited. This is to prevent attacks that
- attempt to crash the system to gain control on reboot and steal
- data left in memory.
- - The kernel will perform all of its sleep preparation and
- populate the shared page with the ACPI data needed to put the
- platform in the desired sleep state.
- - Then the kernel jumps into tboot via the vector specified in the
- shared page.
- - Tboot will clean up the environment and disable TXT, then use the
- kernel-provided ACPI information to actually place the platform
- into the desired sleep state.
- - In the case of S3, tboot will also register itself as the resume
- vector. This is necessary because it must re-establish the
- measured environment upon resume. Once the TXT environment
- has been restored, it will restore the TPM PCRs and then
- transfer control back to the kernel's S3 resume vector.
- In order to preserve system integrity across S3, the kernel
- provides tboot with a set of memory ranges (RAM and RESERVED_KERN
- in the e820 table, but not any memory that BIOS might alter over
- the S3 transition) that tboot will calculate a MAC (message
- authentication code) over and then seal with the TPM. On resume
- and once the measured environment has been re-established, tboot
- will re-calculate the MAC and verify it against the sealed value.
- Tboot's policy determines what happens if the verification fails.
- Note that the c/s 194 of tboot which has the new MAC code supports
- this.
-
-That's pretty much it for TXT support.
-
-
-Configuring the System:
-======================
-
-This code works with 32bit, 32bit PAE, and 64bit (x86_64) kernels.
-
-In BIOS, the user must enable: TPM, TXT, VT-x, VT-d. Not all BIOSes
-allow these to be individually enabled/disabled and the screens in
-which to find them are BIOS-specific.
-
-grub.conf needs to be modified as follows:
- title Linux 2.6.29-tip w/ tboot
- root (hd0,0)
- kernel /tboot.gz logging=serial,vga,memory
- module /vmlinuz-2.6.29-tip intel_iommu=on ro
- root=LABEL=/ rhgb console=ttyS0,115200 3
- module /initrd-2.6.29-tip.img
- module /Q35_SINIT_17.BIN
-
-The kernel option for enabling Intel TXT support is found under the
-Security top-level menu and is called "Enable Intel(R) Trusted
-Execution Technology (TXT)". It is marked as EXPERIMENTAL and
-depends on the generic x86 support (to allow maximum flexibility in
-kernel build options), since the tboot code will detect whether the
-platform actually supports Intel TXT and thus whether any of the
-kernel code is executed.
-
-The Q35_SINIT_17.BIN file is what Intel TXT refers to as an
-Authenticated Code Module. It is specific to the chipset in the
-system and can also be found on the Trusted Boot site. It is an
-(unencrypted) module signed by Intel that is used as part of the
-DRTM process to verify and configure the system. It is signed
-because it operates at a higher privilege level in the system than
-any other macrocode and its correct operation is critical to the
-establishment of the DRTM. The process for determining the correct
-SINIT ACM for a system is documented in the SINIT-guide.txt file
-that is on the tboot SourceForge site under the SINIT ACM downloads.