I managed to get an SSH client working using an SSH pubkey protected by a TPM.

Optional: Take ownership of the TPM chip

This is not needed, since TPM operations only need well known SRK PIN, not owner PIN, to do useful stuff. I only document it here in case you want to do it. Microsoft recommends against it.

  1. Set OSManagedAuthLevel to 4 HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\TPM\OSManagedAuthLevel 2 -> 4

    Reboot.

  2. Clear TPM

    Run tpm.msc and choose “Clear TPM”. The machine will reboot and ask you to press F12 or something for physical proof of presence to clear it.

  3. Set owner password from within tpm.msc

Set up TPM for SSH

  1. Create key

    tpmvscmgr.exe create /name "myhostnamehere VSC" /pin prompt /adminkey random /generate
    

    PIN must be at least 8 characters.

  2. Create CSR

    Create a new text file req.inf:

    [NewRequest]
    Subject = "CN=myhostnamehere"
    Keylength = 2048
    Exportable = FALSE
    UserProtected = TRUE
    MachineKeySet = FALSE
    ProviderName = "Microsoft Base Smart Card Crypto Provider"
    ProviderType = 1
    RequestType = PKCS10
    KeyUsage = 0x80
    
    certreq -new -f req.inf myhostname.csr
    

    If you get any errors, just reboot and try again with the command that failed.

  3. Get the CSR signed by any CA at all

    We just need it to be a certificate so that Windows will install it.

    This should work (on a Linux system) by creating a dummy CA and using it to sign:

    yes '' | openssl req -x509 -newkey rsa:2048 -keyout ca.pem -nodes -out ca.pem -days 3650;echo
    openssl x509 -req -days 3650 -in myhostname.csr -out myhostname.crt -CA ca.pem -CAkey ca.pem -CAcreateserial
    
  4. Double-click on the resulting .crt file

    Click the “Install Certificate…” button and go through the motions.

  5. Extract the public key in SSH format.

    $ openssl req -in khan.csr  -pubkey -noout > pub.txt
    $ ssh-keygen -i -m PKCS8 -f pub.txt
    ssh-rsa AAAAB3Nzaxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
    

    This should give you the public key in SSH format. Just put that in ~/.ssh/authorized_keys, and probably add something descriptive at the end.

  6. Log in with PuttyWinCrypt

    You can’t use normal Putty because PuttyWinCrypt includes required support for smart card and Windows crypto.

    Under “Connection > SSH > Auth” you need to set “Private key file for authentication” to cert://*.