Authentication, authorization, traceability and auditability for SSH accesses.
Bastions are a cluster of machines used as the unique entry point by operational teams (such as sysadmins, developers, database admins, …) to securely connect to devices (servers, virtual machines, cloud instances, network equipment, …), usually using ssh
.
The Bastion provides mechanisms for authentication, authorization, traceability and auditability for your whole infrastructure.
Being between your users and your infrastructure, The Bastion adds a layer of abstraction in-between so that your infrastructure doesn’t need to know your operational team members individually.
Each of your team member has an individual account on The Bastion, and may be a member of one or several bastion groups that may give them access to one or more infrastructures. The infrastructure devices only need to know and trust the bastion group(s) they may be a part of.
The Bastion fine-grained RBAC makes it possible to delegate some responsibilities to any account, group-scoped or bastion-wide, including to accounts that might be used by your automation to e.g. manage the lifecycle of the accounts (linked to your human resources management system, your LDAP or AD), ensure a group’s ACL is up to date (linked to your CMDB), etc. Automated processes are easy to implement through the JSON API over SSH.
Want to know more while viewing some nice drawings? Here is a series of blog posts that dig more into the core functionalities and principles of The Bastion:
Other resources that might be of interest:
Nothing fancy is needed either on the ingress or the egress side of The Bastion to make it work.
Only your good old ssh
client is needed to connect through it, and on the other side, any standard sshd
server will do the trick. This includes, for example, network devices on which you may not have the possibility to install any custom software.
Ancient devices that only support low-security cryptography algorithms or telnet can be hidden from the Internet by firewalling them and only allowing The Bastion, hereby avoiding a low-security trade-off by still allowing only high-security grade connections on the bastion ingress side.
Please see the online documentation, or the corresponding text-based version found in the doc/
folder.
This is a good way to test The Bastion within seconds, but read the FAQ if you’re serious about using containerization in production.
The sandbox image is available for the following architectures: linux/386, linux/amd64, linux/arm/v6, linux/arm/v7, linux/arm64, linux/ppc64le, linux/s390x.
Let’s run the docker image:
docker run -d -p 22 --name bastiontest ovhcom/the-bastion:sandbox
Get your public SSH key at hand, then configure the first administrator account:
docker exec -it bastiontest /opt/bastion/bin/admin/setup-first-admin-account.sh poweruser auto
We’re now up and running with the default configuration! Let’s setup a handy bastion alias, and test the info
command:
PORT=$(docker port bastiontest | cut -d: -f2)
alias bastion="ssh poweruser@127.0.0.1 -tp $PORT -- "
bastion --osh info
It should greet you as being a bastion admin, which means you have access to all commands. Let’s enter interactive mode:
bastion -i
This is useful to call several --osh
plugins in a row. Now we can ask for help to see all plugins:
$> help
If you have a remote machine you want to try to connect to through the bastion, fetch your egress key:
$> selfListEgressKeys
Copy this public key to the remote machine’s authorized_keys
under the .ssh/
folder of the account you want to connect to, then:
$> selfAddPersonalAccess --host <remote_host> --user <remote_account_name> --port-any
$> ssh <remote_account_name>@<remote_host>
Note that you can connect directly without using interactive mode, with:
bastion <remote_account_name>@<remote_machine_host_or_ip>
That’s it! Of course, there is a lot more to it, documentation is available under the doc/
folder and online.
Be sure to check the help of the bastion (bastion --help
) and the help of each osh plugin (bastion --osh command --help
).
Also don’t forget to customize your bastion.conf
file, which can be found in /etc/bastion/bastion.conf
(for Linux).
Linux distros below are tested with each release, but as this is a security product, you are warmly advised to run it on the latest up-to-date stable version of your favorite OS:
*: Note that these versions have no out-of-the-box MFA support, as they lack packaged versions of pamtester
, pam-google-authenticator
, or both. Of course, you may compile those yourself.
Any other so-called “modern” Linux version are not tested with each release, but should work with no or minor adjustments.
The following OS are also tested with each release:
**: Note that these have partial MFA support, due to their reduced set of available pam
plugins. Support for either an additional password or TOTP factor can be configured, but not both at the same time. The code is actually known to work on FreeBSD/HardenedBSD 10+, but it’s only regularly tested under 14.2.
Other BSD variants, such as OpenBSD and NetBSD, are unsupported as they have a severe limitation over the maximum number of supplementary groups, causing problems for group membership and restricted commands checks, as well as no filesystem-level ACL support and missing PAM support (hence no MFA).
perltidy
perlcritic
Even with the most conservative, precautionous and paranoid coding process, code has bugs, so it shouldn’t be trusted blindly. Hence the bastion doesn’t trust its own code. It leverages the operating system security primitives to get additional security, as seen below.
Uses the well-known and trusted UNIX Discretionary Access Control:
The bastion main script is declared as the bastion user’s system shell:
bash
-like) shell access on the systemThe code is modular
ssh
access to other machinesAll the code needing extended system privileges is separated from the main code, in modules called helpers
sudo
sudoers
configuration is attached to a system group specific to the command, which is granted to accounts on a need-to-use basissudoers
configuration-T
) is used for all code running under sudo
, preventing any user-input to interfere with the logic, by halting execution immediatelysudo
doesn’t trust its caller and re-checks every inputA protocol break is operated between the ingress and the egress side, rendering most protocol-based vulnerabilities ineffective
syslog
, which should also be sent to a remote syslog server to ensure even bastion administrators can’t tamper their tracks, and/orsqlite3
databases for easy searchingttyrec
, helper scripts are provided to encrypt and push these records on a remote escrow filerA non-exhaustive list of related tools that are maintained by the community:
Licensed under the Apache License, Version 2.0 (the “License”);
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an “AS IS” BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.