Reducing Trust Domain with TXT Daniel De Graaf

TXT overview Original TPM – Static Root of Trust – BIOS, all boot ROMs, bootloader, hypervisor, OS TPM 1.2 – dynamic root of trust – Hypervisor startup (Xen) – Normal OS startup (Linux)

Application Trust Standard system – Kernel and hypervisor – All root processes (those with debug capabilities) – All processes with same UID Reduced system – Kernel – TSS daemon (verifies application)

Trusted Process Launch 1.Notify TSS daemon (attach request) 2.Execute trusted application 3.TSS inspects memory map 4.Continue launch – Shared libraries must be checked by application – Stack (argv/environ) and heap are not checked

Attestation Information Virtual memory mappings – Program “text” and BSS (data) – Dynamic linker (if used) TSS signature – Dedicated PCR for signatures (random value) – Performed by TSS upon application request

Test Application SSL server with built-in public key Signed client certificates Server authentication provided by TPM – TPM Quote of: app hash, client cert hash, nonce – Secure if client cert is secure Trusted Storage needed for normal SSL