In Daoli architecture, we only measure BIOS, TGrub and VMM. According to TCG spec, the integrity of BIOS is protected by CRTM, and BIOS should measure the first sector which locates in cylinder 0, head 0, sector 1 (i.e. sector’s LBA value is zero). So, we could ignore security of BIOS and OS Loader in figure 5. Because Fudan team has enhanced the structure of VMM for memory curtain and isolating process, so it should let an entity to protect VMM. In TxT? technology, it is required that CPU and chipsets measure VMM by using AC (Authenticated Code) module. But in Daoli architecture, the task is handled by Grub which will be replaced by TGrub. However, how to establish code integrity of TGrub is a key to trusted boot for forming concrete trusted chain. In here, we use TPM_SEAL function for binding TGrub entity and TPM. That to say, the sealed TGrub can only be decrypted in specific platform.

Protect TGrub

As to protecting TGrub, we use SRK in TPM to encrypt stage2 of TGrub during installing process, and let encrypted stage2 as a blob to replace original stage2. While TGrub is running, the decrypted code in stage 1.5 is executed for sending blob to TPM internal data buffer.

Measured VMM

TGrub is under VMM, and stage2 could establish file system. Fudan team requires that the compressed file, which is kernel of VMM like as xen-3.0.3.0.gz, should be measured by an entity. Here, we let stage2 in TGrub act as a judge to verdict the validity of VMM.

-- ZhangYu - 16 May 2008