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 argument 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  alternative  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  entirely  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  policies.  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 succeed.

       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 provides 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-decrypt(1)

AUTHORS

       Nathaniel McCallum <npmccallum@redhat.com>.

                                          Sepember 2017                                 CLEVIS(1)