Hey @Foxboron

want to use this on windows. Mac and Linux.

Any ideas what OS types are supported ? You’re using Google’s tpm package I see .

also planning to build a basic gui with basic query capabilities with gioui

Since TPM keys are deterministic we can actually save the key context outside of the TPM isntead of a persistent handle. This saves resources on the limited hardware with the downside that the host is storing a blob.

Would need to use tpm2.ContextSave instead of tpm2.EvictControl without key handle. Then we need to use tpm2.ContextLoad before using the key again.

Test case:

# Generate a key inside of a TPM
$ age-plugin-tpm -g > age-tpm.txt

# Generate a 1KB plaintext and encrypt it
$ dd if=/dev/urandom bs=1024 count=1 | age -a -r "$(age-plugin-tpm -l | tail -n1)" > test.txt.age
1+0 records in
1+0 records out
1024 bytes (1.0 kB, 1.0 KiB) copied, 4.4513e-05 s, 23.0 MB/s

# Try decrypting it
$ cat test.txt.age | age -d -i age-tpm.txt | wc -c
1024

# Generate another 1KB plaintext and try to encrypt it to multiple keys
$ dd if=/dev/urandom bs=1024 count=1 | age -a -r "$(age-plugin-tpm -l | tail -n1)" -r "$(age-keygen 2>/dev/null | age-keygen -y)" > test.txt.age
1+0 records in
1+0 records out
1024 bytes (1.0 kB, 1.0 KiB) copied, 4.2366e-05 s, 24.2 MB/s

# Try to decrypt it... wait, what?!
$ cat test.txt.age | age -d -i age-tpm.txt
age: error: tpm plugin: failed to read line: EOF
age: report unexpected or unhelpful errors at https://filippo.io/age/report

# `rage` also fails:
$ cat test.txt.age | rage -d -i age-tpm.txt
Error: incomplete response

[ Did rage not do what you expected? Could an error be more useful? ]
[ Tell us: https://str4d.xyz/rage/report                            ]

# Interestingly, if a file is encrypted with rage, it is unable to be decrypted at all:
$ dd if=/dev/urandom bs=1024 count=1 | rage -a -r "$(age-plugin-tpm -l | tail -n1)" > test.txt.age
1+0 records in
1+0 records out
1024 bytes (1.0 kB, 1.0 KiB) copied, 4.4326e-05 s, 23.1 MB/s

$ cat test.txt.age | age -d -i age-tpm.txt
age: error: tpm plugin: failed to read line: EOF
age: report unexpected or unhelpful errors at https://filippo.io/age/report

$ cat test.txt.age | rage -d -i age-tpm.txt
Error: incomplete response

[ Did rage not do what you expected? Could an error be more useful? ]
[ Tell us: https://str4d.xyz/rage/report                            ]

Note that in case of multiple keys encrypting a message, other keys decrypt the message successfully, no matter what it's encrypted with.

age-plugin-yubikey implements a tag as part of the piv-p256 stanza that is essentially a truncated sha256sum of the key bytes.

I think it's mainly used as a simple canary to ensure the correct key is used?

We only make RSA keys, we should make ECDSA keys as well.

C2SP/C2SP#31

We should support pins for the key we create. This should be supplyable through -p, --pin or the environment variable AGE_PLUGIN_TPM_KEY_PIN.

On a completely unrelated machine to the one with the actual keys on it; a machine which does not have the TPM configured to be accessible to the user, this happens when I encrypt a file. I don't expect this to happen when I try to encrypt a file, since I only should need the public key and not the actual tpm. Indeed, when I gave myself permission to the tpm, it encrypted fine.

/tmp/recipients.txt:

age1tpm1qgfe8w2vrkrerx9eyc8yjsluelas9l62nm0g72cuzcspxlu8t70a5znvftj

[jade@snowflake:~/.dotfiles/configs/nix]$ AGEDEBUG=plugin rage -R /tmp/recipients.txt -e flake.nix > /tmp/nya
-> add-recipient age1tpm1qgfe8w2vrkrerx9eyc8yjsluelas9l62nm0g72cuzcspxlu8t70a5znvftj

-> wrap-file-key
JfGaksEZOwWERXUhkDd2kw
-> done

Error: open /dev/tpmrm0: permission denied
Usage:
  age-plugin-tpm [flags]

Examples:

  $ age-plugin-tpm --generate -o age-identity.txt
  # Created: 2023-07-10 22:13:57.864450969 +0200 CEST m=+0.475252114
  # Recipient: age1tpm1qt92lcdxj75rjz9e4t9nud7fv6t2cfn8rhzdfnc0z2rnfgv3cqwrqgme4dq

  AGE-PLUGIN-TPM-1QYQQQKQQYVQQKQQZQPEQQQQQZQQPJQQTQQPSQYQQYR92LCDXJ75RJZ9E4T9NUD7[...]

  $ echo "Hello World" | age -r "age1tpm1syqqqpqrtxsnkkqlmu505zzrq439hetls4qwwmyhsv8dgjhks
vtewvx29lxs7s68qy" > secret.age

  $ age --decrypt -i age-identity.txt -o - secret.age
  Hello World

Flags:
  -y, --convert           Convert identities to recipients.
  -o, --output string     Write the result to the file.
  -g, --generate          Generate a identity.
  -p, --pin               Include a pin with the key. Alternatively export AGE_TPM_PIN.
      --log-file string   Logging file for debug output
      --swtpm             Use a software TPM for key storage (Testing only and requires sw
tpm installed)
  -h, --help              help for age-plugin-tpm

2024/02/15 16:56:18 open /dev/tpmrm0: permission denied
Error: 'age-plugin-tpm' unexpectedly died.
If you are developing a plugin, run with AGEDEBUG=plugin for more information.
Warning: this prints private encryption key material to standard error.

[ Did rage not do what you expected? Could an error be more useful? ]
[ Tell us: https://str4d.xyz/rage/report                            ]

Version: 0.2.0 from nixpkgs.

Currently age-plugin-tpm makes ephemeral NIST P256 key in software when the someone encrypt something with the recipient.

There is probably(?) nothing stopping us from creating an ephemeral key inside the TPM on the remote side and use this for ECDH.

We could make this toggle-able if this is not something the remote end wants.

It would be nice if we could also seal the keys given a set of PCR values.

Even nicer would be support for FAPI policies which could be provided in a JSON file. But I currently see no FAPI support in go-tpm. So its probably quite difficult to implement this without tpm2-tss's Fapi_Import()?

This would allow us to seal existing age keys and maybe do something cool.

Decrypting a 1 line text file with this plugins takes about 2 seconds, is this expected?

age-plugin-yubikey has a pretty cool setup menu. Should probably consider doing something similar for the sake of usability.

I think it would be better to print prompts like

This became problematic for me when I was trying the following:

age-plugin-tpm --generate --pin > test.tpm

And the prompt didn't show