Skip to content
Bootstrapping and Maintaining Trust in the Cloud
Branch: master
Clone or download
lukehinds Merge pull request #124 from keylime/detailed-slides
Add more detailed Keylime architecture slides
Latest commit 9432832 May 10, 2019


Build Status Gitter chat


Keylime is an open source scalable cloud 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.)

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 provisoned with secrets stored within an encrypted payload released by the TPM.

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 1.2 & 2.0 support

Keylime supports both TPM versions 1.2 and 2.0. Although going forwards new feature development will be more focused on the newer TPM 2.0 version.

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



Keylime requires Python 2.7.10 or newer for proper TLS support.

Installation can be performed via an automated shell script, The following command line options are available:

Usage: ./ [option...]
-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 TPM in socket/simulator mode (vs. chardev)
-p PATH         Use PATH as Keylime path
-h              This help info

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.

Ansible (Development Only)

Ansible roles are available to deploy keylime in either TPM 1.2 or 2.0 mode (with the relevant TPM 1.2 or 2.0 Emulator). Since this role currently uses a TPM emulator, it should only be used for development or testing and NOT in production.

Please proceed to the Keylime Ansible Repository.

Docker (Development Only)

Python 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 here or our local CI script here which will automate the build and pull of keylime on TPM 1.2 or 2.0.


Keylime requires Python 2.7.10 or newer for proper TLS support. This is newer than some LTS distributions like Ubuntu 14.04 or CentOS 7. See google for instructions on how to get a newer Python onto those platforms.

Python-based prerequisites

The following python packages are required:

  • pycryptodomex>=3.4.1
  • tornado>=4.3
  • m2crypto>=0.21.1
  • pyzmq>=14.4
  • setuptools>=0.7
  • python-dev
  • pyyaml

The latter of these are usually available as distro packages. See for more information if you want to install them this way. You can also let keylime's install them via PyPI.

TPM utility prerequisites

TPM 1.2 Support

You also need a patched version of tpm4720 the IBM software TPM emulator and utilities. This is available at Even if you are using keylime with a real TPM, you must install the IBM emulator because keylime uses the command line utilities that come with it. See in that project for detailed instructions on how to build and install it.

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

git clone
cd tpm4720-keylime/libtpm
sudo make install

To build tpm4720 to use the TPM emulator replace ./ with ./

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

TPM 2.0 Support

Keylime uses the Intel TPM2 software set to provide TPM 2.0 support. You will need to install the tpm2-tss software stack (available at as well as a patched version of the tpm2-tools utilities available at See 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 tpm2-tss
pushd tpm2-tss
./configure --prefix=/usr
sudo make install

git clone tpm2-tools
pushd tpm2-tools
./configure --prefix=/usr/local
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 (available at as well instead of communicating directly with the TPM. See at that project 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 tpm2-abrmd
pushd tpm2-abrmd
./configure --with-dbuspolicydir=/etc/dbus-1/system.d \
            --with-systemdsystemunitdir=/lib/systemd/system \
            --with-systemdpresetdir=/lib/systemd/system-preset \
sudo make install
sudo ldconfig
sudo pkill -HUP dbus-daemon
sudo systemctl daemon-reload
sudo service tpm2-abrmd start
export TPM2TOOLS_TCTI=""

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

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 python install

To run on OSX 10.11+

You need to build m2crypto from source with

brew install openssl
git clone
python build build_ext --openssl=/usr/local/opt/openssl/
sudo -E python 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 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:

dmesg | grep -i tpm

to see if the kernel is initializing the TPM driver during boot. 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.


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.


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 with UUID D432FBB3-D2F1-4A97-9EF7-75BD81C00000 and talk to a cloud verifier at 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 -v -u D432FBB3-D2F1-4A97-9EF7-75BD81C00000 -f filetosend

To stop keylime from requesting attestations:

keylime_tenant -c delete -t -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 cloud 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

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

This will zip the above files and place them in /var/lib/keylime/ca/ 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 -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 cloud 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 cloud 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).

Report a Security Vulnerability

Please contact us directly at 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 gitter chat

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

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.


Copyright (c) 2019 Massachusetts Institute of Technology.

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.


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.

Delivered to the US Government with Unlimited Rights, as defined in DFARS Part 252.227-7013 or 7014 (Feb 2014). Notwithstanding any copyright notice, U.S. Government rights in this work are defined by DFARS 252.227-7013 or DFARS 252.227-7014 as detailed above. Use of this work other than as specifically authorized by the U.S. Government may violate any copyrights that exist in this work.

You can’t perform that action at this time.