NAME

       clevis -- Automated decryption policy framework

SYNOPSIS

       clevis COMMAND [OPTIONS]

OVERVIEW

       Clevis  is  a  framework for automated decryption policy.  It allows you to define a policy at encryption
       time that must be satisfied for the data to decrypt.  Once this policy is met, the data is decrypted.

       Clevis is pluggable.  Our plugins are called pins.  The job of a pin is to take a policy as its first ar‐
       gument and plaintext on standard input and to encrypt the data so that it can be automatically  decrypted
       if the policy is met.  Lets walk through an example.

HTTP ESCROW

       When  using the HTTP pin, we create a new, cryptographically-strong, random key.  This key is stored in a
       remote HTTP escrow server (using a simple PUT or POST).  Then at decryption time, we attempt to fetch the
       key back again in order to decrypt our data.  So, for our configuration we need to pass the  URL  to  the
       key location:

              $ clevis encrypt http '{"url":"https://escrow.srv/1234"}' < PT > JWE

       To decrypt the data, simply provide the ciphertext (JWE):

              $ clevis decrypt < JWE > PLAINTEXT

       Notice  that  we did not pass any configuration during decryption.  The decrypt command extracted the URL
       (and possibly other configuration) from the JWE object, fetched the encryption key from  the  escrow  and
       performed decryption.

       For more information, see clevis-encrypt-http(1).

TANG BINDING

       Clevis  provides support for the Tang network binding server.  Tang provides a stateless, lightweight al‐
       ternative to escrows.  Encrypting data using the Tang pin works much like our HTTP pin above:

              $ clevis encrypt tang '{"url":"http://tang.srv"}' < PT > JWE
              The advertisement contains the following signing keys:

              _OsIk0T-E2l6qjfdDiwVmidoZjA

              Do you wish to trust these keys? [ynYN] y

       As you can see above, Tang utilizes a trust-on-first-use workflow.  Alternatively, Tang can  perform  en‐
       tirely  offline  encryption  if  you  pre-share the server advertisement.  Decryption, too works like our
       first example:

              $ clevis decrypt < JWE > PT

       For more information, see clevis-encrypt-tang(1).

SHAMIR'S SECRET SHARING

       Clevis provides a way to mix pins together to create sophisticated unlocking and high availability  poli‐
       cies.  This is accomplished by using an algorithm called Shamir's Secret Sharing (SSS).

       SSS  is  a  thresholding scheme.  It creates a key and divides it into a number of pieces.  Each piece is
       encrypted using another pin (possibly even SSS recursively).  Additionally, you define the  threshold  t.
       If  at  least t pieces can be decrypted, then the encryption key can be recovered and decryption can suc‐
       ceed.

       For example, let's create a high-availability setup using Tang:

              $ cfg='{"t":1,"pins":{"tang":[{"url":...},{"url":...}]}}'
              $ clevis encrypt sss "$cfg" < PT > JWE

       In this policy, we are declaring that we have a threshold of 1, but that there are multiple key fragments
       encrypted using different Tang servers.  Since our threshold is 1, so long as any of the Tang servers are
       available, decryption will succeed.  As always, decryption is simply:

              $ clevis decrypt < JWE > PT

       For more information, see clevis-encrypt-tang(1).

LUKS BINDING

       Clevis can be used to bind an existing LUKS volume to its automation policy.  This is accomplished with a
       simple command:

              $ clevis luks bind -d /dev/sda tang '{"url":...}'

       This command performs four steps:

       1. Creates a new key with the same entropy as the LUKS master key.

       2. Encrypts the new key with Clevis.

       3. Stores the Clevis JWE in the LUKS header with LUKSMeta.

       4. Enables the new key for use with LUKS.

       This disk can now be unlocked with your existing password as well as with the Clevis policy.  Clevis pro‐
       vides two unlockers for LUKS volumes.  First, we provide integration with Dracut to automatically  unlock
       your  root volume during early boot.  Second, we provide integration with UDisks2 to automatically unlock
       your removable media in your desktop session.

       For more information, see clevis-luks-bind(1).

SEE ALSO

       clevis-encrypt-http(1), clevis-encrypt-tang(1),  clevis-encrypt-sss(1),  clevis-luks-bind(1),  clevis-de‐
       crypt(1)

AUTHORS

       Nathaniel McCallum <npmccallum@redhat.com>.

                                                  Sepember 2017                                        CLEVIS(1)