2013-12-01

How TPM-protected SSH keys work

Categories: hsm, security, unix

In my last blog post I described how to set up SSH with TPM-protected keys. This time I'll try to explain how it works.

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2013-11-27

TPM chip protecting SSH keys - properly

Categories: hsm, security, tpm, unix

Not long after getting my TPM chip to protect SSH keys in a recent blog post, it started to become obvious that OpenCryptoKi was not the best solution. It's large, complicated, and, frankly, insecure. I dug in to see if I could fix it, but there was too much I wanted to fix, and too many features I didn't need.

So I wrote my own. It's smaller, simpler, and more secure. This post is about this new solution.

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2013-11-13

TPM chip protecting SSH keys

Categories: hsm, security, tpm, unix

STOP! There is a better way. this post explains a simpler and more secure way.

Update 2: I have something I think will be better up my sleeve for using the TPM chip with SSH. Stay tuned. In the mean time, the below works.

Finally, I found out how to use a TPM chip to protect SSH keys. Thanks to Perry Lorier. I'm just going to note down those same steps, but with my notes.

I've written about hardware protecting crypto keys and increasing SSH security before:

but this is what I've always been after. With this solution the SSH key cannot be stolen. If someone uses this SSH key that means that the machine with the TPM chip is involved right now. Right now it's not turned off, or disconnected from the network.

Update: you need to delete /var/lib/opencryptoki/tpm/your-username/*.pem, because otherwise your keys will be migratable. I'm looking into how to either never generating these files, or making them unusable by having the TPM chip reject them. Update to come.

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2013-02-28

GPG and SSH with Yubikey NEO

Categories: hsm, security, unix

I'm a big fan of hardware tokens for access. The three basic technologies where you have public key crypto are SSH, GPG and SSL. Here I will show how to use a Yubikey NEO to protect GPG and SSH keys so that they cannot be stolen or copied. (well, they can be physically stolen, of course).

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2013-02-09

Plug computer for always-on VPN

Categories: network, security, unix

Last time I was at a hacker conference I for obvious reasons didn't want to connect to the local network. It's not just a matter of setting up some simple firewall rules, since the people around you are people who have and are inventing new and unusual attacks. Examples of this would be rogue IPv6 RA and NDs, and people who have actually generated their own signed root CAs. There's also the risk (or certainty) of having all your unencrypted traffic sniffed and altered.

For next time I've prepared a SheevaPlug computer I had laying around. I updated it to a modern Debian installation, added a USB network card, and set it up to provide always-on VPN. This could also be done using a raspberry pi, but I don't have one.

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2012-10-05

Interesting Arping bug report

Categories: coding, network, unix

A few months ago I was strolling in the Debian bug tracking system and found a curious bug filed against Arping, a program I maintain.

It said that unlike Arping 2.09, in Arping 2.11 the ARP cache was not updated after successful reply. I thought that was odd, since there's no code to touch the ARP cache, neither read nor write. Surely this behaviour hasn't changed?

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2012-05-19

Shared libraries diamond problem

Categories: coding, unix

If you split up code into different libraries you can get a diamond dependency problem. That is you have two parts of your code that depend on different incompatible versions of the same library.

Normally you shouldn't get in this situation. Only someone who hates their users makes a non backwards compatible change to a library ABI. You don't hate your users, do you?

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2011-10-15

Optimizing TCP slow start

Categories: network, unix

The short version of the problem and solution I will describe is that while TCP gets up to speed fairly fast, and "fast enough" for many uses, it doesn't accelerate fast enough for short-lived connections such as web page requests. If I have 10Mbps connection and the server has 10Mbps to spare, why doesn't a 17kB web page transfer at 10Mbps from first to last byte? (that is, when excluding TCP handshake, HTTP request and server side page rendering)

This is pretty Linux-focused, but I'll add pointers for other OSs if I see them.

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2011-07-17

Yubico is awesome

Categories: coding, hsm, security, unix

Yubico and their products are awesome.

That pretty much sums up this blog post but I'm going to go on anyway. If you're thinking of introducing two-factor authentication to your company, or you're using something that's fundamentally broken (like RSA SecureID) you simply must at least take Yubikeys into consideration.

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2011-07-06

OpenSSH certificates

Categories: security, unix

The documentation for OpenSSH certificates (introduced in OpenSSH 5.4) are, shall we say, a bit lacking. So I'm writing down the essentials of what they are and how to use them.

What they are NOT

They're not SSH PubkeyAuthentication

In other words if your .pub file doesn't end in -cert.pub and you haven't used ssh-keygen -s, then you aren't using certificates.

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