How to change a JWT provisioners (key) password?

[realk1ko]

Is there a way to change an existing provisioners (key) password?

To my knowledge the encryptedKey part of the configuration of a provisioner should contain the private (?) key of a provisioner used for authentication/authorization. Additionally I did find this discussion where it was shown that it indeed is possible to decrypt the key of a provisioner and use it without encryption: #427 (reply in thread)

But I'm missing some info on how to use the encrypt option of step crypto jwe to reencrypt the key. I've tried various different combinations of the command and arguments, but to no avail: I simply don't have the expertise about JWT/JWE unfortunately.

Can anybody help me out here? I would like to use this opportunity to learn more about JWT/JWE.

Many thanks in advance!

[maraino]

Hi @realk1ko, I'm gonna go step by step, and finally provide you a one-liner combining everything

Let's start creating a key and the compact version of the jwk.priv (password is password)

$ step crypto jwk create jwk.pub jwk.priv
$ cat jwk.priv | step crypto jose format
eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJjdHkiOiJqd2sranNvbiIsImVuYyI6IkEyNTZHQ00iLCJwMmMiOjEwMDAwMCwicDJzIjoiMFFOQ1FqRjhYWld1VTQ5NzF5UV9uQSJ9.2wKtwondscO3mg9v5klopbZu4zlaqt3sIpNOL5bWRL4sCKOMBRvO4g.fa7xNy2yHkT7KP0A.Zykb8mu7vnU1M8QdZJ2YgTCmP-k-wqjAa2zk0U18NapFA6Oqd__JdkTX3XCMRkCbH259AMes2Bm7tQHaXin6DD-Mw03pbrKraTpYO6Jz61wui1p2VdxF9IA9mwB2Fm61tuOKZ2rEP9Fr6QCD1SeczU26KQNT8yvPEPckRVsOsep5J2EycF5fkEKMiE32zLQSgbbhvlGiFJ-VH3FOq4WmJp9LlSDmkswUPZQqfAVpUruwtGfNKDv3cpgRBqvVlx3TmmXm6wEB8IVqeCr1fUs27tNM9UWPwFChDQ6LVeSX1LS3ntJUeVH_pb273Gq0E8o9ydJPxZX_x0rKW1XAfGk.GstSOCDgiYFhi8qHwUOrJw

Let's decrypt now that:

$ echo eyJhbGci... | step crypto jwe decrypt
{"use":"sig","kty":"EC","kid":"4Y4_pv4LC-Rg0aW7Gbo_Nk8lnuzegpfpQYt3NO4IEN0","crv":"P-256","alg":"ES256","x":"LIHm8OtNcZ2Y2xIOy6cftxw-xWUYe1wA7_pOf9ummgM","y":"FOlKgs8Y4243u_NV6ar_ITqYc3yiBjN9WWBnsN27fco","d":"WGHmDLLiwhEeKQt-5p7PvXiu7JPM3G-QH4I7gKDVLI4"}

And finally encrypt that again with a new password and use the compact format (new password is pass)

$ echo '{"use":"sig","kty":"EC","kid":"4Y4_pv4LC-Rg0aW7Gbo_Nk8lnuzegpfpQYt3NO4IEN0","crv":"P-256","alg":"ES256","x":"LIHm8OtNcZ2Y2xIOy6cftxw-xWUYe1wA7_pOf9ummgM","y":"FOlKgs8Y4243u_NV6ar_ITqYc3yiBjN9WWBnsN27fco","d":"WGHmDLLiwhEeKQt-5p7PvXiu7JPM3G-QH4I7gKDVLI4"}' | step crypto jwe encrypt --alg PBES2-HS256+A128KW | step crypto jose format
eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMjU2R0NNIiwicDJjIjoxMDAwMDAsInAycyI6IkR5Z1dqYlhKaGNRSFEwNnhCZTlhNVEifQ.tGamBiz_1kuyY-4BaJknPH_MiUt9unznkt_azwNVHyaOI00Mck8SJQ.eZLAgtaU6BXxYLwZ.7_DSTl7l7PXD-V9BJbWAdoxjkRIWdPjQs6eMLPQRqhl1WGB-n35OD7KHq-mhYu_LZLPMb8eoQSa7BC6G_kA4IOnkHnhjOesB6GoHS25WgQCCupz3db1F2tEAOxblKvUGNQ2fIPSnyGAtex7A7vU9nXBmcQUmaEtFIEkkoxcU2t_Zm5ejcDDm_maXTOoCqf1SALV5mFMowyl0azwPBMkUSZnjLWCzV7VCJwfCGxpquckOfkh5rFvwjgjM8EJaHtkw4kOkElNWAtsirXGNDgE9rThG0bv3eUk2iYyyIJ1l_6jHxO8UWIMdQxyVoj9BgGARm-eE28UT6UEPpbDwyT8n.ifNdzx_mz0jbfRcjsIGbQA

All in one from an encrypted key:

$ echo eyJhbGci... | step crypto jwe decrypt | step crypto jwe encrypt --alg PBES2-HS256+A128KW | step crypto jose format
Please enter the password to decrypt the content encryption key: password
Please enter the password to encrypt the content encryption key: pass
eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMjU2R0NNIiwicDJjIjoxMDAwMDAsInAycyI6ImpUN09FQTdJWmJ5WVdxb1lCdDNyNXcifQ.Y4XColO6eD7X8Qd1b7_i8UXdCm3odmRUtYJ0pokazgjvxXASJI1NHQ.XY1P056h9Bygc_D2.b0hvJkKQpU_Kmi6Kk1MsUN456b3fdGIBP_QDht9HySaKIJd3nWbkO4EGIZ3rrpLtCZx2IeTOebb3U5ZRajF7XlwzllvA17yWF9LgmFumTiPhYqf0SQOY4lXbtIPHxwSU9V1gBa7OarvtBUrIwFeOULDOaYT-0zi6PMbn-00Vvdi8v3oScCwlotNEpHjRtV6DLVxQ-88EL7KzYZPAK7uGL6NTLT3N2XOM_GShZBGSdtL6qWJapvXGUn7A_5wIhZp1GrkcB3q2ev8v3n1VQt0nLr_yxtYMYtVk05Q6y9ad6f-tC_xpzj__phKV_xWEy81FUNVIEwbCKR2up_PAdIM.FFPjKyRAUdYgEwAO-hP6cw

[maraino]

The detail here is the use of --alg PBES2-HS256+A128KW. If we look at initial key in the full format:

{
  "protected": "eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJjdHkiOiJqd2sranNvbiIsImVuYyI6IkEyNTZHQ00iLCJwMmMiOjEwMDAwMCwicDJzIjoiMFFOQ1FqRjhYWld1VTQ5NzF5UV9uQSJ9",
  "encrypted_key": "2wKtwondscO3mg9v5klopbZu4zlaqt3sIpNOL5bWRL4sCKOMBRvO4g",
  "iv": "fa7xNy2yHkT7KP0A",
  "ciphertext": "Zykb8mu7vnU1M8QdZJ2YgTCmP-k-wqjAa2zk0U18NapFA6Oqd__JdkTX3XCMRkCbH259AMes2Bm7tQHaXin6DD-Mw03pbrKraTpYO6Jz61wui1p2VdxF9IA9mwB2Fm61tuOKZ2rEP9Fr6QCD1SeczU26KQNT8yvPEPckRVsOsep5J2EycF5fkEKMiE32zLQSgbbhvlGiFJ-VH3FOq4WmJp9LlSDmkswUPZQqfAVpUruwtGfNKDv3cpgRBqvVlx3TmmXm6wEB8IVqeCr1fUs27tNM9UWPwFChDQ6LVeSX1LS3ntJUeVH_pb273Gq0E8o9ydJPxZX_x0rKW1XAfGk",
  "tag": "GstSOCDgiYFhi8qHwUOrJw"
}

The protected part defines the algorithm to use to decrypt the key:

$ echo eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJjdHkiOiJqd2sranNvbiIsImVuYyI6IkEyNTZHQ00iLCJwMmMiOjEwMDAwMCwicDJzIjoiMFFOQ1FqRjhYWld1VTQ5NzF5UV9uQSJ9 | step base64 -d | jq
{
  "alg": "PBES2-HS256+A128KW",
  "cty": "jwk+json",
  "enc": "A256GCM",
  "p2c": 100000,
  "p2s": "0QNCQjF8XZWuU4971yQ_nA"
}

This is a password based encryption for a JWE, and is defined at https://datatracker.ietf.org/doc/html/rfc7518#section-4.8

[maraino]

And another one-liner using step crypto key format:

$ echo eyJhbGci... | step crypto key format -jwk | step crypto jose format
Please enter the password to decrypt the key: password
Please enter the password to encrypt the private JWK: pass
eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJjdHkiOiJqd2sranNvbiIsImVuYyI6IkEyNTZHQ00iLCJwMmMiOjEwMDAwMCwicDJzIjoid1JrRzN1SHFVdzZHdEhUa2tUbFB0USJ9.piEhHzl7Ue3eJaC923wRnEO_9GwbZ8cYfeRJIKkUTdkK3Hh4i63AlA.IgPR-sgBi5x1X7Yw.JywAni_5qMXZ72dchIVgNLQQI10K-Lz_aAWizS-R6LoFV_cOiiVogsu0bVNS0A1r6c59W7AoQ5PCuzwg28PYWZm7Me7lEq-4IBDI1m8tYZJV9fRGS-8vphS2TIgVS0t6M-elGOpuV8ZQYfGi76O9LQjEFHASiL3LufijoweHNu-fnqenUwvI-sAeUbZhLP2Fd-Er4xmmGz9ItcB2dPOpJBQqREApPZiEi9vZZusSllo.SHDXATrRcAvxm4OtoyvKeQ

[realk1ko]

Thank you so much for your help!

I have a few things to note though, since I tried this locally with the encrypted key of the first provisioner, not a newly created one.

Using the following command works perfectly fine when replacing the encryptedKey in the ca.json attribute afterwards:

cat old_key.txt | step crypto jose format |  step crypto jwe decrypt | step crypto jwe encrypt --alg PBES2-HS256+A128KW | step crypto jose format > new_key.txt
cat new_key.json # I replaced encryptedKey with this

The other one-liner does not work, but I'm not sure why. I've been playing around with it a little to understand it more.

cat old_key.txt | step crypto key format -jwk | step crypto jose format > broken_new_key.txt

wc -m *_key.txt # shows about 100 characters of difference between old and broken, 20 between old and new

cat old_key.txt | step crypto jose format | step crypto jwe decrypt | jq
cat new_key.txt | step crypto jose format | step crypto jwe decrypt | jq
cat broken_new_key.txt | step crypto jose format | step crypto jwe decrypt | jq

Where it gets interesting is after the last command. The decrypted broken key using step crypto key format -jwk looks as follows:

{
  "kty": "EC",
  "crv": "P-256"
  "x": "...",
  "y": "...",
  "d": "..."
}

The decrypted old and new key look almost identical:

{
  "use": "sig",
  "kty": "EC",
  "kid": "...",
  "crv": "P-256",
  "alg": "ES256",
  "x": "...",
  "y": "...",
  "d": "..."
}

It seems that using the latter method removes some of the info from the original key?

Additionally, comparing the protected attributes on the old and (working) new key, I noticed that the new key after encryption is missing the cty attribute/parameter. Is this important?

Old:

{
  "alg": "PBES2-HS256+A128KW",
  "cty": "jwk+json",
  "enc": "A256GCM",
  "p2c": 100000,
  "p2s": "..."
}

New:

{
  "alg": "PBES2-HS256+A128KW",
  "enc": "A256GCM",
  "p2c": 100000,
  "p2s": "..."
}

[realk1ko]

Seems that the manual is quite comprehensive: https://smallstep.com/docs/step-cli/reference/crypto/jwe/encrypt

Adding --cty=jwk+json as parameter when re-encrypting the key adds the missing parameter (although it is not really necessary):

cat old_key.txt | step crypto jose format |  step crypto jwe decrypt | step crypto jwe encrypt --alg PBES2-HS256+A128KW --cty jwk+json | step crypto jose format > new_key.txt

So the last question I have answered myself. :-)

[maraino]

I see what is going on, step crypto key format only takes into account the key itself and not other attributes that are used on the JWK provisioner.

Encoded data using step crypto key format:

{
  "kty": "EC",
  "crv": "P-256",
  "x": "LIHm8OtNcZ2Y2xIOy6cftxw-xWUYe1wA7_pOf9ummgM",
  "y": "FOlKgs8Y4243u_NV6ar_ITqYc3yiBjN9WWBnsN27fco",
  "d": "WGHmDLLiwhEeKQt-5p7PvXiu7JPM3G-QH4I7gKDVLI4"
}

Encoded data using step crypto jwe ...:

{
  "use": "sig",
  "kty": "EC",
  "kid": "4Y4_pv4LC-Rg0aW7Gbo_Nk8lnuzegpfpQYt3NO4IEN0",
  "crv": "P-256",
  "alg": "ES256",
  "x": "LIHm8OtNcZ2Y2xIOy6cftxw-xWUYe1wA7_pOf9ummgM",
  "y": "FOlKgs8Y4243u_NV6ar_ITqYc3yiBjN9WWBnsN27fco",
  "d": "WGHmDLLiwhEeKQt-5p7PvXiu7JPM3G-QH4I7gKDVLI4"
}

[tashian]

I've just added docs for this, as part of the JWK provisioner documentation.