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diff --git a/Documentation/security/intel/acm.md b/Documentation/security/intel/acm.md new file mode 100644 index 000000000000..b7dfacde8c71 --- /dev/null +++ b/Documentation/security/intel/acm.md @@ -0,0 +1,57 @@ +# Intel Authenticated Code Modules + +The Authenticated Code Modules (ACMs) are Intel digitally signed modules +that contain code to be run before the traditional x86 CPU reset vector. +The ACMs can be invoked at runtime through the GETSEC instruction, too. + +A platform that wants to use Intel TXT must use two ACMs: +1. BIOS ACM + * The BIOS ACM must be present in the boot flash. + * The BIOS ACM must be referenced by the [FIT]. +2. SINIT ACM + * The SINIT ACM isn't referenced by the [FIT]. + * The SINIT ACM should be provided by the boot firmware, but bootloaders + like [TBOOT] are able to load them from the filesystem as well. + +## Retrieving ACMs + +The ACMs can be downloaded on Intel's website: +[Intel Trusted Execution Technology](https://software.intel.com/en-us/articles/intel-trusted-execution-technology) + +If you want to extract the BLOB from vendor firmware you can search for the +string ``LCP_POLICY_DATA`` or ``TXT``. + +## Header + +Every ACM has a fixed size header: + +```c +/* + * ACM Header v0.0 without dynamic part + * Chapter A.1 + * Intel TXT Software Development Guide (Document: 315168-015) + */ +struct acm_header_v0 { + uint16_t module_type; + uint16_t module_sub_type; + uint32_t header_len; + uint16_t header_version[2]; + uint16_t chipset_id; + uint16_t flags; + uint32_t module_vendor; + uint32_t date; + uint32_t size; + uint16_t txt_svn; + uint16_t se_svn; + uint32_t code_control; + uint32_t error_entry_point; + uint32_t gdt_limit; + uint32_t gdt_ptr; + uint32_t seg_sel; + uint32_t entry_point; + uint8_t reserved2[63]; +} __packed; +``` + +[FIT]: ../../soc/intel/fit.md +[TBOOT]: https://sourceforge.net/p/tboot/wiki/Home/ |