STOP! There is a better way.
I’ve written a post that explains a simpler and more secure way.
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.
You need to delete
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.
When I run this again on a completely blank system I’ll add more exact outputs.
1. Install dependencies
$ apt-get install trousers tpm-tools
Make sure tcsd is running and only listening on localhost.
$ sudo netstat -nap | grep :30003.*LISTEN tcp 0 0 127.0.0.1:30003 0.0.0.0:* LISTEN 3103/tcsd
2. Verify TPM chip
tpm_selftest don’t give errors.
$ tpm_version TPM 1.2 Version Info: Chip Version: 188.8.131.52 Spec Level: 2 Errata Revision: 2 TPM Vendor ID: INTC Vendor Specific data: 00040001 0003040e TPM Version: 01010000 Manufacturer Info: 494e5443 $ tpm_selftest TPM Test Results: 00000000
3. Initialise the TPM chip
If you’ve already taken ownership, but set an SRK password, then run
sudo tpm_changeownerauth -s -r. Not all tools support
SRK passwords, so you have to remove it, or in other words change it
to the “well known password” that is 20 zero bytes (I’m not making
If it says
Tspi_TPM_TakeOwnership failed then you may have to use
tpm_clear to reset the chip to factory state and try again. This may
involve cold reboots, enabling the TPM chip in the BIOS, and other
sudo pkcs11_startup; sudo service opencryptoki restart
4. Add users to TPM groups
Add all users who will be using the TPM chip to the ‘tss’ and ‘pkcs11’ groups.
Don’t forget to log out and in again, or run
5. As every user, initialize the user’s TPM PKCS#11 data store</h1>
If you get
Bus Error (core dumped) then check for, and delete, any
/var/lib/opencryptoki/tpm/your-user-name-here/.stmapfile file laying
6. Generate an RSA key pair
$ pkcs11-tool --module=/usr/lib/opencryptoki/libopencryptoki.so.0 \ --login --keypairgen -d 01 \ -a "$(whoami)@$(hostname --fqdn) key" \ --key-type rsa:2048 [...]
7. Try some pkcs11-tool commands
$ pkcs11-tool --module=/usr/lib/opencryptoki/libopencryptoki.so.0 -O Using slot 0 with a present token (0x0) Public Key Object; RSA 2048 bits label: [email protected] ID: XX Usage: encrypt, verify, wrap $ pkcs11-tool --module /usr/lib/opencryptoki/libopencryptoki.so.0 -O --login Using slot 0 with a present token (0x0) Logging in to "IBM PKCS#11 TPM Token". Please enter User PIN: Private Key Object; RSA label: [email protected] ID: XX Usage: decrypt, sign, unwrap warning: PKCS11 function C_GetAttributeValue(ALWAYS_AUTHENTICATE) failed: rv = CKR_ATTRIBUTE_TYPE_INVALID (0x12) [Thomas note: ignore this warning] Public Key Object; RSA 2048 bits label: [email protected] ID: XX Usage: encrypt, verify, wrap
8. Set up simple SSH
Extract the public part of the key in SSH format:
$ ssh-keygen -D /usr/lib/opencryptoki/libopencryptoki.so.0 ssh-rsa AAAAB3NzaHjn[...]uiimW
Put it in an
~/.ssh/authorized_keys or something.
$ ssh -I /usr/lib/opencryptoki/libopencryptoki.so.0 [email protected] Enter PIN for 'IBM PKCS#11 TPM Token': You have new mail. Last login: Wed Nov 13 22:14:11 2013 from XXXX.XXXX.com [email protected]$
Add this to your
Host * PKCS11Provider /usr/lib/opencryptoki/libopencryptoki.so.0
Or add it to your
$ ssh-add -s /usr/lib/opencryptoki/libopencryptoki.so.0 Enter passphrase for PKCS#11: Card added: /usr/lib/opencryptoki/libopencryptoki.so.0 $ ssh-add -l 2048 xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx /usr/lib/opencryptoki/libopencryptoki.so.0 (RSA)
9. If you want, set up SSH certificates
- Don’t set an SRK password. Some tools don’t specifying it (like
tpmtoken_init), and only work with the default all-null SRK password.
- If you get a “No EK” error anywhere along the lines, try
- The default “security officer” password is “87654321”.
ssh-add -Ddoes not disconnect completely from the pkcs11 provider (the TPM chip), use
ssh-add -e /usr/lib/opencryptoki/libopencryptoki.so.0if
ssh-add -s /usr/lib/opencryptoki/libopencryptoki.so.0gives errors
- You can use the TPM chip with Chrome. See Lorier’s documentation for details.
- Another useful tool: