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Keylime

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keylime

Keylime is an open-source scalable trust system harnessing TPM Technology.

Keylime provides an end-to-end solution for bootstrapping hardware rooted cryptographic trust for remote machines, the provisioning of encrypted payloads, and run-time system integrity monitoring. It also provides a flexible framework for the remote attestation of any given PCR (Platform Configuration Register). Users can create their own customized actions that will trigger when a machine fails its attested measurements.

Keylime's mission is to make TPM Technology easily accessible to developers and users alike, without the need for a deep understanding of the lower levels of a TPM's operations. Amongst many scenarios, it well suited to tenants who need to remotely attest machines not under their own full control (such as a consumer of hybrid cloud or a remote Edge / IoT device in an insecure physical tamper prone location.)

Keylime can be driven with a CLI application, web front end, and a set of RESTful APIs.

Keylime consists of three main components; The Verifier, Registrar and the Agent.

  • The Verifier continuously verifies the integrity state of the machine that the agent is running on.

  • The Registrar is a database of all agents registered with Keylime and hosts the public keys of the TPM vendors.

  • The Agent is deployed to the remote machine that is to be measured or provisioned with secrets stored within an encrypted payload released once trust is established.

Rust based Keylime Agent

The verifier, registrar, and agent are all developed in Python and situated in this repository keylime. The agent is currently undergoing a port to the Rust programming language, with this work taking place in the rust-keylime repository.

The decision was made to port the agent to Rust, as rust is a low level performant systems language designed with security as a central tenet, by means of the rust compilers ownership model.

When the rust agent work is complete, the rust-keylime agent will become the recommended ongoing agent within Keylime. Until then the Python agent is fully functioning and available to use as a remote monitoring system to interact with the keylime verifier and registrar.

TPM Support

Keylime supports TPM version 2.0.

Keylime can be used with a hardware TPM, or a software TPM emulator for development, testing, or demonstration purposes. However, DO NOT USE keylime in production with a TPM emulator! A software TPM emulator does not provide a hardware root of trust and dramatically lowers the security benefits of using keylime.

A hardware TPM should always be used when real secrets and trust is required.

Table of Contents

Installation

Installer script

Keylimes installer requires Python 3.6 or greater.

The following command line options are available using installer.sh script:

Usage: ./installer.sh [option...]
Options:
-k              Download Keylime (stub installer mode)
-o              Use OpenSSL instead of CFSSL
-t              Create tarball with keylime_agent
-m              Use modern TPM 2.0 libraries (vs. TPM 1.2)
-s              Install & use a Software TPM emulator (development only)
-p PATH         Use PATH as Keylime path
-h              This help info

Should you not have the Keylime repository on your local machine, you can use the -k flag which will download the software. In this case, all you need is the installer.sh script locally.

Note that CFSSL is required if you want to support revocation. As noted above, do not use the TPM emulator option -s in production systems.

Installer Distribution coverage

Distribution Versions TPM2-Software
CentOS 7 / 8 Compiled
RHEL 7 / 8 Compiled
Fedora 32 / 33 / 34 Package Install
Ubuntu 19 LTS / 20 Compiled

Ansible

Ansible roles are available to deploy keylime for use with a hardware TPM or a software TPM emulator. Please proceed to the Keylime Ansible Repository. Or, alternatively the Keylime Ansible TPM Emulator Repository.

WARNING: The "Keylime Ansible TPM Emulator" role uses a software TPM, which is considered cryptographically insecure. It should only be used for development or testing and NOT in production!

Docker (Development Only)

keylime and related emulators can also be deployed using Docker. Since this docker configuration currently uses a TPM emulator, it should only be used for development or testing and NOT in production.

Please see either the Dockerfiles or our local CI script which will automate the build and pull of keylime on TPM 1.2 or 2.0.

Manual

Keylimes installer requires Python 3.6 or greater.

Python-based prerequisites

The list of Python packages needed to install keylime can be found in requirements.txt.

Some of them are usually available as distro packages. See installer.sh for more information, if you want to install them this way.

You can also install them using pip:

python3 -m pip install -r requirements.txt

TPM utility prerequisites

Keylime uses the Intel TPM2 software set to provide TPM 2.0 support.

These can be installed using your package manager.

  • On Fedora 32 (and greater):

sudo dnf install tpm2-tss tpm2-tools tpm2-abrmd

  • On Ubuntu 20 LTS:

sudo apt-get install tpm2-tss tpm2-tools tpm2-abrmd

You can also build the tpm2-tss software stack as well as tpm2-tools instead . See the README.md in these projects for detailed instructions on how to build and install.

The brief synopsis of a quick build/install (after installing dependencies) is:

git clone https://github.com/tpm2-software/tpm2-tss.git tpm2-tss
pushd tpm2-tss
./bootstrap
./configure --prefix=/usr
make
sudo make install
popd

git clone https://github.com/tpm2-software/tpm2-tools.git tpm2-tools
pushd tpm2-tools
./bootstrap
./configure --prefix=/usr/local
make
sudo make install

To ensure that you have the patched version installed ensure that you have the tpm2_checkquote utility in your path.

TPM 2.0 Resource Manager

Note that it is recommended that you use the tpm2-abrmd resource manager as well instead of communicating directly with the TPM. See README.md for detailed instructions on how to build and install.

A brief, workable example for Ubuntu 18 LTS systems is:

sudo useradd --system --user-group tss
git clone https://github.com/tpm2-software/tpm2-abrmd.git tpm2-abrmd
pushd tpm2-abrmd
./bootstrap
./configure --with-dbuspolicydir=/etc/dbus-1/system.d \
            --with-systemdsystemunitdir=/lib/systemd/system \
            --with-systemdpresetdir=/lib/systemd/system-preset \
            --datarootdir=/usr/share
make
sudo make install
sudo ldconfig
sudo pkill -HUP dbus-daemon
sudo systemctl daemon-reload
sudo service tpm2-abrmd start
export TPM2TOOLS_TCTI="tabrmd:bus_name=com.intel.tss2.Tabrmd"

# NOTE: if using swtpm2 emulator, you need to run the tpm2-abrmd service as:
sudo -u tss /usr/local/sbin/tpm2-abrmd --tcti=mssim &

A brief, workable example for Fedora is:

git clone https://github.com/tpm2-software/tpm2-abrmd.git ${TPM2_ABRMD}
pushd tpm2-abrmd
./bootstrap
./configure --prefix=/usr
make
make install
ldconfig
pkill -HUP dbus-daemon
systemctl enable tpm2-abrmd
systemctl start tpm2-abrmd

Note: if you use an emulator, you will need to add the --tcti=mssim argument to ExecStart within the systemd file (/usr/lib/systemd/system/tpm2-abrmd.service):

ExecStart=/usr/sbin/tpm2-abrmd --tcti=mssim

After this, reload systemd to pick up the above changes.

systemctl daemon-reload
systemctl restart tpm2-abrmd
TPM 2.0 Direct Access (without tpm2-abrmd)

Alternatively, it is also possible, though not recommended, to communicate directly with the TPM (and not use a resource manager). This can be done by setting the environment var TPM2TOOLS_TCTI to the appropriate value:

To talk directly to the swtpm2 emulator:

export TPM2TOOLS_TCTI="mssim:port=2321"

To talk directly to a real TPM:

export TPM2TOOLS_TCTI="device:/dev/tpm0"

Install Keylime

You're finally ready to install keylime!

sudo python3 -m pip install . -r requirements.txt

To run on OSX 10.11+

You need to build m2crypto from source with following steps:

brew install openssl
git clone https://gitlab.com/m2crypto/m2crypto.git
python setup.py build build_ext --openssl=/usr/local/opt/openssl/
sudo -E python setup.py install build_ext --openssl=/usr/local/opt/openssl/

Optional Requirements

If you want to support revocation, you also need to have cfssl installed and in your path on the tenant agent. It can be obtained from https://github.com/cloudflare/cfssl. You will also need to set ca_implementation to "cfssl" instead of "openssl" in /etc/keylime.conf.

Making sure your TPM is ready for keylime

The above instructions for installing the TPM libraries will be configured to talk to /dev/tpm0. If this device is not on your system, then you may need to build/install TPM support for your kernel. You can use following command to see if the kernel is initializing the TPM driver during boot:

dmesg | grep -i tpm

If you have the /dev/tpm0 device, you next need to get it into the right state. The kernel driver reports status on the TPM in /sys. You can locate the folder with relevant info from the driver using:

sudo find /sys -name tpm0

Several results may be returned, but the duplicates are just symlinks to one location. Go to one of the returned paths, for example, /sys/class/misc/tpm0. Now change to the device directory. Here you can find some information from the TPM like the current pcr values and sometimes the public EK is available. It will also report two important state values: active and enabled. To use keylime, both of these must be 1. If they are not, you may need to reboot into the BIOS to enable and activate the TPM. If you need to both enable and activate, then you must enable first, reboot, then activate and finally reboot again. It is also possible that you may need to assert physical presence (see manual for your system on how to do this) in order to accomplish these actions in your BIOS.

If your system shows enabled and activated, you can next check the "owned" status in the /sys directory. Keylime can take a system that is not owned (i.e., owned = 0) and take control of it. Keylime can also take a system that is already owned, provided that you know the owner password and that keylime or another trusted computing system that relies upon tpm4720 previously took ownership. If you know the owner password, you can set the option tpm_ownerpassword in keylime.conf to this known value.

Usage

Configuring keylime

keylime puts its configuration in /etc/keylime.conf. It will also take an alternate location for the config in the environment var KEYLIME_CONFIG.

This file is documented with comments and should be self-explanatory.

Running keylime

Keylime has three major component services that run: the registrar, verifier, and the agent:

  • The registrar is a simple HTTPS service that accepts TPM public keys. It then presents an interface to obtain these public keys for checking quotes.

  • The verifier is the most important component in keylime. It does initial and periodic checks of system integrity and supports bootstrapping a cryptographic key securely with the agent. The verifier uses mutual TLS for its control interface.

    By default, the verifier will create appropriate TLS certificates for itself in /var/lib/keylime/cv_ca/. The registrar and tenant will use this as well. If you use the generated TLS certificates then all the processes need to run as root to allow reading of private key files in /var/lib/keylime/.

  • The agent is the target of bootstrapping and integrity measurements. It puts its stuff into /var/lib/keylime/.

To run a basic test, run keylime_verifier, keylime_registrar, and keylime_agent. If the agent starts up properly, then you can proceed.

Provisioning

To kick everything off you need to tell keylime to provision a machine. This can be done either with the keylime tenant or webapp.

Provisioning with keylime_tenant

The keylime_tenant utility can be used to provision your agent.

As an example, the following command tells keylime to provision a new agent at 127.0.0.1 with UUID d432fbb3-d2f1-4a97-9ef7-75bd81c00000 and talk to a verifier at 127.0.0.1. Finally it will encrypt a file called filetosend and send it to the agent allowing it to decrypt it only if the configured TPM policy (in /etc/keylime.conf) is satisfied:

keylime_tenant -c add -t 127.0.0.1 -v 127.0.0.1 -u D432fbb3-d2f1-4a97-9ef7-75bd81c00000 -f filetosend

To stop keylime from requesting attestations:

keylime_tenant -c delete -t 127.0.0.1 -u d432fbb3-d2f1-4a97-9ef7-75bd81c00000

For additional advanced options for the tenant utility run:

keylime_tenant -h

Provisioning with keylime_webapp

There is also a WebApp GUI interface for the tenant, available by running keylime_webapp. Next, simply navigate to the WebApp in your web browser (https://localhost/webapp/ by default, as specified in /etc/keylime.conf).

Note that the webapp must be run on the same machine as the tenant, since it uses its keys for TLS authentication in /var/lib/keylime/.

Using keylime CA

A simple certificate authority is available to use with keylime. You can interact with it using keylime_ca or keylime_tenant. Options for configuring the certificates that keylime_ca creates are in /etc/keylime.conf.

NOTE: This CA functionality is different than the TLS support for talking to the verifier or registrar (though it uses some of the same config options in /etc/keylime.conf). This CA is for the Keylime Agents you provision and you can use keylime to bootstrap the private keys into agents.

To initialize a new certificate authority run:

keylime_ca --command init

This will create a certificate authority in /var/lib/keylime/ca and requires root access to write to the directory. Use -d to point it to another directory not necessarily requiring root.

You can create certificates under this ca using:

keylime_ca --command create --name certname.host.com

This will create a certificate signed by the CA in /var/lib/keylime/ca (-d also works here to have it use a different CA directory).

To obtain a zip file of the certificate, public key, and private key for a cert use:

keylime_ca --command pkg --name certname.host.com

This will zip the above files and place them in /var/lib/keylime/ca/certname.host.com-pkg.zip. The private key will be protected by the key that you were prompted with.

You may wonder why this is in keylime at all? Well, you can tell keylime_tenant to automatically create a key and then provision an agent with it. Use the --cert option in keylime_tenant to do this. This takes in the directory of the CA:

keylime_tenant -c add -t 127.0.0.1 -u d432fbb3-d2f1-4a97-9ef7-75bd81c00000 --cert /var/lib/keylime/ca

If you also have the option extract_payload_zip in /etc/keylime.conf set to True on the keylime agent, then it will automatically extract the zip containing an unprotected private key, public key, certificate and CA certificate to /var/lib/keylime/secure/unzipped.

If the keylime verifier option revocation_notifier is set to True, then the CV will sign a revocation message and send it over 0mq to any subscribers. The keylime CA supports listening to these notifications and will generate an updated CRL. To enable this feature, run:

keylime_ca -c listen

The revocation key will be automatically created by the tenant the first time you use the CA with keylime. Currently the CRL is only written back to the CA directory, unless IPsec configuration is being used (see Additional Reading).

Systemd service support

The directory services/ includes systemd service files for the verifier, agent and registrar.

You can install the services with the following command:

sudo ./services/install.sh

Once installed, you can run and inspect the services keylime_verifier, keylime_agent and keylime_registrar via systemctl.

Request a feature

Keylime feature requests are tracked as enhancements in the enhancements repository

The enhancement process has been implemented to provide a way to review and assess the impact(s) of significant changes to Keylime.

Security Vulnerability Management Policy

If you would have found a security vulnerability in Keylime and would like to report, first of all: thank you.

Please contact us directly at [email protected] for any bug that might impact the security of this project. Do not use a Github issue to report any potential security bugs.

Project Meetings

We meet every Wednesday @ 15:00 UTC to 15:30. Anyone is welcome to join the meeting.

The meeting is hosted in CNCF chat (Slack)

Meeting agenda are hosted and archived in the meetings repo as Github issues.

Contributing: First Timers Support

We welcome new contributors to Keylime of any form, including those of you who maybe new to working in an open source project.

So if you are new to open source development, don't worry, there are a myriad of ways you can get involved in our open source project. As a start, try exploring issues with good first issue label. We understand that the process of creating a Pull Request (PR) can be a barrier for new contributors. These issues are reserved for new contributors like you. If you need any help or advice in making the PR, feel free to jump into our chat room and ask for help there.

Your contribution is our gift to make our project even more robust. Check out CONTRIBUTING.md to find out more about how to contribute to our project.

Keylime uses Semantic Versioning. It is recommended you also read the RELEASE.md file to learn more about it and familiarise yourself with simple of examples of using it.

Testing

Please, see TESTING.md for details.

Additional Reading

Errata from the ACSAC Paper

We discovered a typo in Figure 5 of the published ACSAC paper. The final interaction between the Tenant and Cloud Verifier showed an HMAC of the node's ID using the key K_e. This should be using K_b. The paper in this repository and the ACSAC presentation have been updated to correct this typo.

The software that runs on the system with the TPM is now called the keylime agent rather than the node. We have made this change in the documentation and code. The ACSAC paper will remain as it was published using node.

Disclaimer

DISTRIBUTION STATEMENT A. Approved for public release: distribution unlimited.

This material is based upon work supported by the Assistant Secretary of Defense for Research and Engineering under Air Force Contract No. FA8721-05-C-0002 and/or FA8702-15-D-0001. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Assistant Secretary of Defense for Research and Engineering.

Keylime's license was changed from BSD Clause-2 to Apache 2.0. The original BSD Clause-2 licensed code can be found on the MIT github organization.