Signed-off-by: Andra Paraschiv <andraprs@xxxxxxxxxx> --- Documentation/nitro_enclaves/ne_overview.txt | 86 ++++++++++++++++++++ 1 file changed, 86 insertions(+) create mode 100644 Documentation/nitro_enclaves/ne_overview.txt diff --git a/Documentation/nitro_enclaves/ne_overview.txt b/Documentation/nitro_enclaves/ne_overview.txt new file mode 100644 index 000000000000..be8bb3d84132 --- /dev/null +++ b/Documentation/nitro_enclaves/ne_overview.txt @@ -0,0 +1,86 @@ +Nitro Enclaves +============== + +Nitro Enclaves (NE) is a new Amazon Elastic Compute Cloud (EC2) capability +that allows customers to carve out isolated compute environments within EC2 +instances [1]. + +For example, an application that processes sensitive data and runs in a VM, +can be separated from other applications running in the same VM. This +application then runs in a separate VM than the primary VM, namely an enclave. + +An enclave runs alongside the VM that spawned it. This setup matches low latency +applications needs. The resources that are allocated for the enclave, such as +memory and CPU, are carved out of the primary VM. Each enclave is mapped to a +process running in the primary VM, that communicates with the NE driver via an +ioctl interface. + +In this sense, there are two components: + +1. An enclave abstraction process - a user space process running in the primary +VM guest that uses the provided ioctl interface of the NE driver to spawn an +enclave VM (that's 2 below). + +How does all gets to an enclave VM running on the host? + +There is a NE emulated PCI device exposed to the primary VM. The driver for this +new PCI device is included in the NE driver. + +The ioctl logic is mapped to PCI device commands e.g. the NE_START_ENCLAVE ioctl +maps to an enclave start PCI command or the KVM_SET_USER_MEMORY_REGION maps to +an add memory PCI command. The PCI device commands are then translated into +actions taken on the hypervisor side; that's the Nitro hypervisor running on the +host where the primary VM is running. The Nitro hypervisor is based on core KVM +technology. + +2. The enclave itself - a VM running on the same host as the primary VM that +spawned it. Memory and CPUs are carved out of the primary VM and are dedicated +for the enclave VM. An enclave does not have persistent storage attached. + +An enclave communicates with the primary VM via a local communication channel, +using virtio-vsock [2]. The primary VM has virtio-pci vsock emulated device, +while the enclave VM has a virtio-mmio vsock emulated device. The vsock device +uses eventfd for signaling. The enclave VM sees the usual interfaces - local +APIC and IOAPIC - to get interrupts from virtio-vsock device. The virtio-mmio +device is placed in memory below the typical 4 GiB. + +The application that runs in the enclave needs to be packaged in an enclave +image together with the OS ( e.g. kernel, ramdisk, init ) that will run in the +enclave VM. The enclave VM has its own kernel and follows the standard Linux +boot protocol. + +The kernel bzImage, the kernel command line, the ramdisk(s) are part of the +Enclave Image Format (EIF); plus an EIF header including metadata such as magic +number, eif version, image size and CRC. + +Hash values are computed for the entire enclave image (EIF), the kernel and +ramdisk(s). That's used, for example, to check that the enclave image that is +loaded in the enclave VM is the one that was intended to be run. + +These crypto measurements are included in a signed attestation document +generated by the Nitro Hypervisor and further used to prove the identity of the +enclave; KMS is an example of service that NE is integrated with and that checks +the attestation doc. + +The enclave image (EIF) is loaded in the enclave memory at offset 8 MiB. The +init process in the enclave connects to the vsock CID of the primary VM and a +predefined port - 9000 - to send a heartbeat value - 0xb7. This mechanism is +used to check in the primary VM that the enclave has booted. + +If the enclave VM crashes or gracefully exits, an interrupt event is received by +the NE driver. This event is sent further to the user space enclave process +running in the primary VM via a poll notification mechanism. Then the user space +enclave process can exit. + +The NE driver for enclave lifetime management provides an ioctl interface to the +user space. It includes the NE PCI device driver that is the means of +communication with the hypervisor running on the host where the primary VM and +the enclave are launched. + +The proposed solution is following the KVM model and uses KVM ioctls to be able +to create and set resources for enclaves. Additional NE ioctl commands, besides +the ones provided by KVM, are used to start an enclave and get memory offset for +in-memory enclave image loading. + +[1] https://aws.amazon.com/ec2/nitro/nitro-enclaves/ +[2] http://man7.org/linux/man-pages/man7/vsock.7.html -- 2.20.1 (Apple Git-117) Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.
