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AWS Certificate Manager for Nitro Enclaves

This is a PKCS#11 provider intended to be executed within the confines of a Nitro Enclave.

Development is aided by Docker containers that can be used to build and test run the PKCS#11 provider as a p11-kit module. These containers are designed to be mostly transparent to the developer, and employed via the omnitool at tools/devtool.

How to install and setup

The user guide for the ACM for Nitro Enclaves can be found at https://docs.aws.amazon.com/enclaves/latest/user/nitro-enclave-refapp.html.

Managed tokens

Each token can store an end-entity private key and its associated ACM certificate chain. Up to 128 SSL/TLS X.509 ACM certificates can be managed via provisioned tokens by the nitro-enclaves-acm service. Configuration options can be found in the /etc/nitro_enclaves/acm.yaml post service installation.

Design Overview

ACM for Nitro Enclaves is a PKCS#11 provider (i.e. a dynamic library exposing the PKCS#11 API). The p11-kit client and server are used to transport crypto operation calls from the parent instance to the enclave, where they are handled by this provider via the AWS cryptographic library.

Here is the general flow of a parent instance crypto operation:

        [parent instance]                 |            [enclave]
                                          |
    OpenSSL client (e.g. nginx)           |
                |                         |
                v                         |
              OpenSSL                     |
                |                         |
                v                         |
        OpenSSL PKCS#11 Engine            |
                |                         |
                v                         |
          p11-kit client ------- vsock channel ---> p11-kit server
                                          |              |
                                          |              v
                                          |    ACM for Nitro Enclaves module
                                          |              |
                                          |              v
                                          |	        AWS libcrypto

Dependencies

name version link
aws-lc v1.12.0 https://github.com/awslabs/aws-lc/
aws-nitro-enclaves-sdk v0.4.1 https://github.com/aws/aws-nitro-enclaves-sdk-c
s2n-tls v1.3.46 https://github.com/aws/s2n-tls.git
aws-c-common v0.8.0 https://github.com/awslabs/aws-c-common
aws-c-io v0.11.0 https://github.com/awslabs/aws-c-io
aws-c-compression v0.2.14 https://github.com/awslabs/aws-c-compression
aws-c-http v0.6.19 https://github.com/awslabs/aws-c-http
aws-c-cal v0.5.18 https://github.com/awslabs/aws-c-cal
aws-c-auth v0.6.15 https://github.com/awslabs/aws-c-auth
aws-c-sdkutils v0.1.2 https://github.com/awslabs/aws-c-sdkutils
aws-nitro-enclaves-nsm-api v0.4.0 https://github.com/aws/aws-nitro-enclaves-nsm-api
json-c json-c-0.16-20220414 https://github.com/json-c/json-c

devtool sets up two containers: one for emulating the enclave environment, and another for emulating the parent instance environment.

If using Docker is not an option, have a look at the Dockerfile for a full list of packages needed to build and run the ACM for Nitro Enclaves module. Additionally, the devtool source (it's just a BASH script) may provide useful details on what environment setup is required prior to building and/or running.

Components

ACM for Nitro Enclaves has a few different components, some meant to be run inside the enclave, others inside the parent instance:

  • enclave-side components:
    • p11ne-srv - the AWS for NE RPC server, used to query the state of the pkcs#11 enclave device, and to provision its database;
    • libvtok_p11.so - the PKCS#11 provider implementation;
  • parent-instance-side components:
    • p11ne-client - the ACM for NE RPC client, providing a low-level interface to the ACM for NE RPC server;
    • p11ne-cli - a user-facing CLI tool that can be used to manage the ACM for NE enclave (e.g. provision a PKCS#11 token);
    • p11ne-db- a user-facing CLI tool that can be used to pack a private key and its associated certificate (or certificate chain) in a database format for provisioning a PKCS#11 token

Building

Use devtool to build any ACM for NE component, by invoking devtool build <component>.

E.g. building the PKCS#11 provider:

tools/devtool build libvtok_p11.so

Building the (development version of) ACM for NE enclave image (EIF):

tools/devtool build dev-image

See devtool help for more build options.

Testing in the development environment

devtool uses development containers to simulate both the enclave and parent instance environments. The communication channel between p11-kit client and p11-kit server is emulated via a Unix socket, bind-mounted into both container environments (parent and enclave).

Note: The emulated enclave environment differs substantially from the production enclave, and it is only to be used for testing the PKCS#11 API functionality of the ACM for Nitro Enclaves module. Most notably, attestation and token provisioning are both missing from the emulated environment.

First, the enclave container needs to be running:

tools/devtool simulate-enclave

This will start p11-kit server with the ACM for Nitro Enclaves module loaded (the module is first built if unavailable). The server is run in foreground mode, so the pkcs#11 provider module log will show up at stderr.

With the enclave environment up and running, the parent environment can be started:

tools/devtool simulate-parent

This will spin up a container with p11-kit configured to access the remote module exposed by the enclave container via a Unix socket. devtool simulate-parent starts a BASH shell, so the user can manually test / inspect the functionality of the ACM for Nitro Enclaves module; for instance, via running openssl manually, directed to use the PKCS#11 engine and a URI pointing to the pkcs#11 provider module token:

openssl pkeyutl -keyform engine -engine pkcs11 -sign -inkey \
	"pkcs11:model=p11ne-token;manufacturer=Amazon;serial=EVT00;token=my-token-label;id=%52;type=private" \
	-in hello.txt -out test.sig

The tests directory contains integration tests that can be executed to validate the PKCS#11 module functionality using openssl or OpenSC pkcs11-tool.

Build the testhelper binary:

$ cd tests/helpers && cargo build --release

$ cd - && cp build/target/release/testhelpers ./tests

After this, the test suite can be executed via the command:

$ ./tests/testtool openssl --kms-key-id <your-kms-key-id> --kms-region <your-kms-key-region>

The above cryptographic test suite is applicable when using real enclaves on EC2 instances where an instance role and a KMS key has already been setup accordingly for provisioning the test pkcs#11 token with the private keys.

License

This project is licensed under the Apache-2.0 License.

Security issue notifications

If you discover a potential security issue in ACM for Nitro Enclaves, we ask that you notify AWS Security via our vulnerability reporting page. Please do not create a public GitHub issue.