Intro I stumbled across an old Cisco box in the basement. I thought i might have some fun (or frust?) with the aging Device. The Hardware still works fine, right ? And what about the Software ? Let’s give a try !
Hardware show version
Cisco 1841 (revision 7.0) with 352256K/40960K bytes of memory. Processor board ID FCZ1234757Y 6 FastEthernet interfaces 1 Virtual Private Network (VPN) Module DRAM configuration is 64 bits wide with parity disabled.
Stumbled upon something that I’ve missed for a long time: encrypting files with the ssh public key :)
Source https://github.com/FiloSottile/age Install Package OpenBSD (and most others *nix systems) got a package for age. Just install it.
doas pkg_add age Asymmetric Encryption Asymmetric Encryption encrypts and decrypts the data using two separate yet mathematically connected cryptographic keys. These keys are known as a ‘Public Key’ and a ‘Private Key’. Together, they’re called a ‘Public and Private Key Pair’
Signing Files with SSH 8.0 unsigned file
$ cat hosts 127.0.0.1 localhost ::1 localhost 1.2.3.4 egal sign
$ ssh-keygen -Y sign -f id_rsa -n file hosts Signing file hosts Write signature to hosts.sig signed file
$ cat hosts.sig -----BEGIN SSH SIGNATURE----- U1NIU0lHAAAAAQAAAZcAAAAHc3NoLXJzYQAAAAMBAAEAAAGBALJB+O4WCOM7V56H1xigpd uJem52Izwltl2cG9GQOO94HClebcr7C5aD24iI4wDcT9Ajv5/fu9cDVEXku83I/U0blUZe oMd8qCIH+4O+RVYyCvKFyEkcZ6n+RRH1G5EgcP0UXtmo4J3p8Hyo/6jtPA/r28+idi84A6 7yW1cmC5GpIw24Vr5aqA3e3rCJdFBZThzsTrwu/DHzIueQstEQdldycUit4X9UPBaCVnov +nhyijO9b8adzkTMxjcJAl65fdLUmwuJ5h3z0owdKOmrcNlbWxqTIuGU0in25ZDQVxLssc WI8oW7vR5F7+cXSV7fYliTG/XPsCkD1KpWc/xSOr35bALRQpxD1+T48mrbKToZuzu4hage cUSOvRI3R0hKIvcXYyf2SQoBfLNlpvl5CRcatlw2fMhFQPrVz0Bh543chEFsF4nxKQw8yq riJbqkvhW8tzKCnMA7vyTRxey6uSDJrw0YchXIJdprNUlgM1t+z9J3AwC4ugpvhgVd6H0v 9QAAAAxob3N0cy5zaWduZWQAAAAAAAAABnNoYTUxMgAAAZQAAAAMcnNhLXNoYTItNTEyAA ABgAB9zAZStPsSvPIBh66lAgGLE/JWPk0voZjTUz9pO5wl81aM6Kn1clY9n4jysEkiQ0xy yy/tWgFzKi10mVfh/SJ34L2Mdo8t+vBnha1KNlkFwXZl+GXiCLlVl+ei6xpRfp9knheoIh LyEHoxgkuI6lO0c8pi4ymNnrlfvkg9SvvZfSdXWUMfTWHDlHvFIGqMg3BWQu7ylTEgQVDF obpqDInU3hkisfsywQRQh6KVVe8eSUc0qVH/FSSLoG8X/IX9Vh3g4tT/2FJPrE4k464yie GdnLkp5edcnnE+jjoSQroMs52QWy2a3XXZC5KTaDL6w4mcry1RpavhXb5aJQ7o0852Pkc9 wDkwX/11JZhMmxNZbDlg+tHsWy12KUubKAxAjJ1HUFXMjTFI6HMu8WyU989e3dOTt/bL3W l7sDo5P8SGv3/6+tJxugz9shz8WaN9Xz6Oh2AfCM6+IROXaeUgWMXtDmGS5bUZxUOSxHa1 ww7wzYR0NKXuOk3IeJMSQ2f97g== -----END SSH SIGNATURE----- verify file allowed signers
$ cat /etc/allowed_signers mail@world.net ssh-rsa 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 verify
Need a small and smart utility to manage you ssh keys under linux ? got some scripts and cronjobs which requires an local ssh key ? have a look at keychain !
Install Software depending on your OS …
macos$ brew install keychain debian$ sudo apt-get install keychain openbsd$ pkg_add keychain freebsd$ pkg install keychain edit startup Scripts $HOME/.bashrc $HOME/.bash_profile /etc/profile $HOME/.profile
cat << 'EOF' >> $HOME/.bashrc # Keychain Startup eval `keychain --eval id_ed25519` EOF check service $ keychain $ ssh-add -L add to .
got a Server behing NAT / Firewall ? Need Shell access to … ?
Server behind NAT/FW user@server$ ssh -R 1234:localhost:22 my.public.jumpbox Access Server ssh my.public.jumpbox user@jumpbox$ ssh -p 1234 localhost user@server$ and you’re in :)
Any Comments ? sha256: 81b4dc1d84f9f8bcbf5060f382853759fffa1e5824e2ae98ad5508a082db5dfd
stumpled upon a bug in openssh … did a small config change in sshd_config, deployed it with ansible … and lost connectifity to all these boxes immediately … and of course, i did a config check before reloading the sshd daemon, and the config check was fine.
i can’t belife that nobody else found this before, as it’s really simple to reproduce. and it’s working with openbsd, debian, centos and mostly on all system which have opensshd implemented (and that’s a lot of …)
Did you know that you can easily forward a variable (or secret) via SSH … ?
This Variable is just available if you’re logged in and never stored in any configfile or backup. This can be a real advantage …
Sending Host /etc/ssh/ssh_conf Host trustedhost.world SendEnv _secret Receiving Host /etc/ssh/sshd_conf AcceptEnv _secret restart sshd
Connect user@myhost ~# export _secret=topsecret99 user@myhost ~# ssh trustedhost.world user@trustedhost ~# set |grep _secret _secret=topsecret99 here we are …
ssh-audit is a tool for ssh server auditing. Features SSH1 and SSH2 protocol server support;
grab banner, recognize device or software and operating system, detect compression;
gather key-exchange, host-key, encryption and message authentication code algorithms;
output algorithm information (available since, removed/disabled, unsafe/weak/legacy, etc);
output algorithm recommendations (append or remove based on recognized software version);
output security information (related issues, assigned CVE list, etc);
analyze SSH version compatibility based on algorithm information;
like ssh and secure keys ? Generate Secure Key ssh-keygen -o -a 100 -t ed25519 -C "MyFamousComment" ssh-keygen -o -a 100 -t ed25519 -C "$(whoami)@$(hostname)" ssh-keygen -o -a 100 -t ed25519 -C "$(whoami)@$(hostname) at $(date \"+%Y-%m-%d\")" ssh-keygen -o -a 100 -t ed25519 -C "$(whoami)@$(hostname) at $(date \"+%Y-%m-%d %H:%M\")" What’s ed25519 ? Wikipedia about Curve25519
Distribute Key ssh-copy-id user@remotehost Connect to Remote Connect to Remove without Agent Forwarding (use this unless you know what you’re dooing …)