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KeyLocker is a new security feature available in new Intel CPUs that
protects data-encryption keys for the Advanced Encryption Standard (AES)
algorithm. These keys are more valuable than what they guard. If stolen
once, the key can be repeatedly used even on another system and even
after vulnerability closed.
It also introduces a CPU-internal wrapping key (IWKey), which is a key-
encryption key to wrap AES keys into handles. While the IWKey is
inaccessible to software, randomizing the value during the boot-time
helps its value unpredictable.
Keylocker usage:
- New “ENCODEKEY” instructions take original key input and returns HANDLE
crypted by an internal wrap key (IWKey, init by “LOADIWKEY” instruction)
- Software can then delete the original key from memory
- Early in boot/software, less likely to have vulnerability that allows
stealing original key
- Later encrypt/decrypt can use the HANDLE through new AES KeyLocker
instructions
- Note:
* Software can use original key without knowing it (use HANDLE)
* HANDLE cannot be used on other systems or after warm/cold reset
* IWKey cannot be read from CPU after it's loaded (this is the
nature of this feature) and only 1 copy of IWKey inside CPU.
The virtualization implementation of Key Locker on ACRN is:
- Each vCPU has a 'struct iwkey' to store its IWKey in struct
acrn_vcpu_arch.
- At initilization, every vCPU is created with a random IWKey.
- Hypervisor traps the execution of LOADIWKEY (by 'LOADIWKEY exiting'
VM-exectuion control) of vCPU to capture and save the IWKey if guest
set a new IWKey. Don't support randomization (emulate CPUID to
disable) of the LOADIWKEY as hypervisor cannot capture and save the
random IWKey. From keylocker spec:
"Note that a VMM may wish to enumerate no support for HW random IWKeys
to the guest (i.e. enumerate CPUID.19H:ECX[1] as 0) as such IWKeys
cannot be easily context switched. A guest ENCODEKEY will return the
type of IWKey used (IWKey.KeySource) and thus will notice if a VMM
virtualized a HW random IWKey with a SW specified IWKey."
- In context_switch_in() of each vCPU, hypervisor loads that vCPU's
IWKey into pCPU by LOADIWKEY instruction.
- There is an assumption that ACRN hypervisor will never use the
KeyLocker feature itself.
This patch implements the vCPU's IWKey management and the next patch
implements host context save/restore IWKey logic.
Tracked-On: #5695
Signed-off-by: Shuo A Liu <shuo.a.liu@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>
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