Provided by: systemd_251.4-1ubuntu7_amd64 bug


       systemd-creds - Lists, shows, encrypts and decrypts service credentials


       systemd-creds [OPTIONS...] COMMAND [ARGS...]


       systemd-creds is a tool for listing, showing, encrypting and decrypting unit credentials.
       Credentials are limited-size binary or textual objects that may be passed to unit
       processes. They are primarily used for passing cryptographic keys (both public and
       private) or certificates, user account information or identity information from the host
       to services.

       Credentials are configured in unit files via the LoadCredential=, SetCredential=,
       LoadCredentialEncrypted= and SetCredentialEncrypted= settings, see systemd.exec(5) for

       For further information see System and Service Credentials[1] documentation.


       The following commands are understood:

           Show a list of credentials passed into the current execution context. This command
           shows the files in the directory referenced by the $CREDENTIALS_DIRECTORY environment
           variable, and is intended to be executed from within service context.

           Along with each credential name, the size and security state is shown. The latter is
           one of "secure" (in case the credential is backed by unswappable memory, i.e.
           "ramfs"), "weak" (in case it is backed by any other type of memory), or "insecure" (if
           having any access mode that is not 0400, i.e. if readable by anyone but the owner).

       cat credential...
           Show contents of specified credentials passed into the current execution context.
           Takes one or more credential names, whose contents shall be written to standard

           When combined with --json= or --transcode= the output is transcoded in simple ways
           before outputting.

           Generates a host encryption key for credentials, if one has not been generated
           already. This ensures the /var/lib/systemd/credential.secret file is initialized with
           a random secret key if it doesn't exist yet. This secret key is used when
           encrypting/decrypting credentials with encrypt or decrypt, and is only accessible to
           the root user. Note that there's typically no need to invoke this command explicitly
           as it is implicitly called when encrypt is invoked, and credential host key encryption

       encrypt input|- output|-
           Loads the specified (unencrypted plaintext) input credential file, encrypts it and
           writes the (encrypted ciphertext) output to the specified target credential file. The
           resulting file may be referenced in the LoadCredentialEncrypted= setting in unit
           files, or its contents used literally in SetCredentialEncrypted= settings.

           Takes two file system paths. The file name part of the output path is embedded as name
           in the encrypted credential, to ensure encrypted credentials cannot be renamed and
           reused for different purposes without this being noticed. The credential name to embed
           may be overridden with the --name= setting. The input or output paths may be specified
           as "-", in which case the credential data is read from/written to standard input and
           standard output. If the output path is specified as "-" the credential name cannot be
           derived from the file system path, and thus should be specified explicitly via the
           --name= switch.

           The credential data is encrypted and authenticated symmetrically with one of the
           following encryption keys:

            1. A secret key automatically derived from the system's TPM2 chip. This encryption
               key is not stored on the host system and thus decryption is only possible with
               access to the original TPM2 chip. Or in other words, the credential secured in
               this way can only be decrypted again by the local machine.

            2. A secret key stored in the /var/lib/systemd/credential.secret file which is only
               accessible to the root user. This "host" encryption key is stored on the host file
               system, and thus decryption is possible with access to the host file system and
               sufficient privileges. The key is automatically generated when needed, but can
               also be created explicitly with the setup command, see above.

            3. A combination of the above: an encryption key derived from both the TPM2 chip and
               the host file system. This means decryption requires both access to the original
               TPM2 chip and the OS installation. This is the default mode of operation if a TPM2
               chip is available and /var/lib/systemd/ resides on persistent media.

           Which of the three keys shall be used for encryption may be configured with the
           --with-key= switch. Depending on the use-case for the encrypted credential the key to
           use may differ. For example, for credentials that shall be accessible from the initial
           RAM disk (initrd) of the system encryption with the host key is not appropriate since
           access to the host key is typically not available from the initrd. Thus, for such
           credentials only the TPM2 key should be used.

           Encrypted credentials are always encoded in Base64.

           Use decrypt (see below) to undo the encryption operation, and acquire the decrypted
           plaintext credential from the encrypted ciphertext credential.

           The credential data is encrypted using AES256-GCM, i.e. providing both confidentiality
           and integrity, keyed by a SHA256 hash of one or both of the secret keys described

       decrypt input|- [output|-]
           Undoes the effect of the encrypt operation: loads the specified (encrypted ciphertext)
           input credential file, decrypts and authenticates it and writes the (decrypted
           plaintext) output to the specified target credential file.

           Takes one or two file system paths. The file name part of the input path is compared
           with the credential name embedded in the encrypted file. If it does not match
           decryption fails. This is done in order to ensure that encrypted credentials are not
           re-purposed without this being detected. The credential name to compare with the
           embedded credential name may also be overridden with the --name= switch. If the input
           path is specified as "-", the encrypted credential is read from standard input. If
           only one path is specified or the output path specified as "-", the decrypted
           credential is written to standard output. In this mode, the expected name embedded in
           the credential cannot be derived from the path and should be specified explicitly with

           Decrypting credentials requires access to the original TPM2 chip and/or credentials
           host key, see above. Information about which keys are required is embedded in the
           encrypted credential data, and thus decryption is entirely automatic.

           Reports whether the system is equipped with a TPM2 device usable for protecting
           credentials. If a TPM2 device has been discovered, is supported, and is being used by
           firmware, by the OS kernel drivers and by userspace (i.e. systemd) this prints "yes"
           and exits with exit status zero. If no such device is discovered/supported/used,
           prints "no". Otherwise prints "partial". In either of these two cases exits with
           non-zero exit status. It also shows three lines indicating separately whether drivers,
           firmware and the system discovered/support/use TPM2.

           Combine with --quiet to suppress the output.

       -h, --help
           Print a short help text and exit.

           Print a short version string and exit.


           When specified with the list and cat commands operates on the credentials passed to
           system as a whole instead of on those passed to the current execution context. This is
           useful in container environments where credentials may be passed in from the container

           When specified with the cat or decrypt commands, transcodes the output before showing
           it. Takes one of "base64", "unbase64", "hex" or "unhex" as argument, in order to
           encode/decode the credential data with Base64 or as series of hexadecimal values.

           Note that this has no effect on the encrypt command, as encrypted credentials are
           unconditionally encoded in Base64.

           When specified with cat or decrypt controls whether to add a trailing newline
           character to the end of the output if it doesn't end in one, anyway. Takes one of
           "auto", "yes" or "no". The default mode of "auto" will suffix the output with a single
           newline character only when writing credential data to a TTY.

       --pretty, -p
           When specified with encrypt controls whether to show the encrypted credential as
           SetCredentialEncrypted= setting that may be pasted directly into a unit file.

           When specified with the encrypt command controls the credential name to embed in the
           encrypted credential data. If not specified the name is chosen automatically from the
           filename component of the specified output path. If specified as empty string no
           credential name is embedded in the encrypted credential, and no verification of
           credential name is done when the credential is decrypted.

           When specified with the decrypt command control the credential name to validate the
           credential name embedded in the encrypted credential with. If not specified the name
           is chosen automatically from the filename component of the specified input path. If no
           credential name is embedded in the encrypted credential file (i.e. the --name= with an
           empty string was used when encrypted) the specified name has no effect as no
           credential name validation is done.

           Embedding the credential name in the encrypted credential is done in order to protect
           against reuse of credentials for purposes they weren't originally intended for, under
           the assumption the credential name is chosen carefully to encode its intended purpose.

           When specified with the encrypt command controls the timestamp to embed into the
           encrypted credential. Defaults to the current time. Takes a timestamp specification in
           the format described in systemd.time(7).

           When specified with the decrypt command controls the timestamp to use to validate the
           "not-after" timestamp that was configured with --not-after= during encryption. If not
           specified defaults to the current system time.

           When specified with the encrypt command controls the time when the credential shall
           not be used anymore. This embeds the specified timestamp in the encrypted credential.
           During decryption the timestamp is checked against the current system clock, and if
           the timestamp is in the past the decryption will fail. By default no such timestamp is
           set. Takes a timestamp specification in the format described in systemd.time(7).

       --with-key=, -H, -T
           When specified with the encrypt command controls the encryption/signature key to use.
           Takes one of "host", "tpm2", "host+tpm2", "tpm2-absent", "auto", "auto-initrd". See
           above for details on the three key types. If set to "auto" (which is the default) the
           TPM2 key is used if a TPM2 device is found and not running in a container. The host
           key is used if /var/lib/systemd/ is on persistent media. This means on typical systems
           the encryption is by default bound to both the TPM2 chip and the OS installation, and
           both need to be available to decrypt the credential again. If "auto" is selected but
           neither TPM2 is available (or running in container) nor /var/lib/systemd/ is on
           persistent media, encryption will fail. If set to "tpm2-absent" a fixed zero length
           key is used (thus, in this mode no confidentiality nor authenticity are provided!).
           This logic is useful to cover for systems that lack a TPM2 chip but where credentials
           shall be generated. Note that decryption of such credentials is refused on systems
           that have a TPM2 chip and where UEFI SecureBoot is enabled (this is done so that such
           a locked down system cannot be tricked into loading a credential generated this way
           that lacks authentication information). If set to "auto-initrd" a TPM2 key is used if
           a TPM2 is found. If not a fixed zero length key is used, equivalent to "tpm2-absent"
           mode. This option is particularly useful to generate credentials files that are
           encrypted/authenticated against TPM2 where available but still work on systems lacking
           support for this.

           The -H switch is a shortcut for --with-key=host. Similar, -T is a shortcut for

           When encrypting credentials that shall be used in the initial RAM disk (initrd) where
           /var/lib/systemd/ is typically not available make sure to use --with-key=auto-initrd
           mode, to disable binding against the host secret.

           This switch has no effect on the decrypt command, as information on which key to use
           for decryption is included in the encrypted credential already.

           Controls the TPM2 device to use. Expects a device node path referring to the TPM2 chip
           (e.g.  /dev/tpmrm0). Alternatively the special value "auto" may be specified, in order
           to automatically determine the device node of a suitable TPM2 device (of which there
           must be exactly one). The special value "list" may be used to enumerate all suitable
           TPM2 devices currently discovered.

       --tpm2-pcrs= [PCR...]
           Configures the TPM2 PCRs (Platform Configuration Registers) to bind the encryption key
           to. Takes a "+" separated list of numeric PCR indexes in the range 0...23. If not
           used, defaults to PCR 7 only. If an empty string is specified, binds the encryption
           key to no PCRs at all. For details about the PCRs available, see the documentation of
           the switch of the same name for systemd-cryptenroll(1).

       --quiet, -q
           When used with has-tpm2 suppresses the output, and only returns an exit status
           indicating support for TPM2.

           Do not pipe output into a pager.

           Do not print the legend, i.e. column headers and the footer with hints.

           Shows output formatted as JSON. Expects one of "short" (for the shortest possible
           output without any redundant whitespace or line breaks), "pretty" (for a pretty
           version of the same, with indentation and line breaks) or "off" (to turn off JSON
           output, the default).


       On success, 0 is returned.

       In case of the has-tpm2 command returns 0 if a TPM2 device is discovered, supported and
       used by firmware, driver, and userspace (i.e. systemd). Otherwise returns the OR
       combination of the value 1 (in case firmware support is missing), 2 (in case driver
       support is missing) and 4 (in case userspace support is missing). If no TPM2 support is
       available at all, value 7 is hence returned.


       Example 1. Encrypt a password for use as credential

       The following command line encrypts the specified password "hunter2", writing the result
       to a file password.cred.

           # echo -n hunter2 | systemd-creds encrypt - password.cred

       This decrypts the file password.cred again, revealing the literal password:

           # systemd-creds decrypt password.cred

       Example 2. Encrypt a password and include it in a unit file

       The following command line prompts the user for a password and generates a
       SetCredentialEncrypted= line from it for a credential named "mysql-password", suitable for
       inclusion in a unit file.

           # systemd-ask-password -n | systemd-creds encrypt --name=mysql-password -p - -
           🔐 Password: ****
           SetCredentialEncrypted=mysql-password: \
                   NAAAAAgAAAAAH4AILIOZ3w6rTzYsBy9G7liaCAd4i+Kpvs8mAgArzwuKxd0ABDjgSeO5k \
                   mKQc58zM94ZffyRmuNeX1lVHE+9e2YD87KfRFNoDLS7F3YmCb347gCiSk2an9egZ7Y0Xs \
                   700Kr6heqQswQEemNEc62k9RJnEl2q7SbcEYguegnPQUATgAIAAsAAAASACA/B90W7E+6 \
                   yAR9NgiIJvxr9bpElztwzB5lUJAxtMBHIgAQACCaSV9DradOZz4EvO/LSaRyRSq2Hj0ym \
                   gVJk/dVzE8Uxj8H3RbsT7rIBH02CIgm/Gv1ukSXO3DMHmVQkDG0wEciyageTfrVEer8z5 \

       The generated line can be pasted 1:1 into a unit file, and will ensure the acquired
       password will be made available in the $CREDENTIALS_DIRECTORY/mysql-password credential
       file for the started service.

       Utilizing the unit file drop-in logic this can be used to securely pass a password
       credential to a unit. A similar, more comprehensive set of commands to insert a password
       into a service xyz.service:

           # mkdir -p /etc/systemd/system/xyz.service.d
           # systemd-ask-password -n | systemd-creds encrypt --name=mysql-password -p - - > /etc/systemd/system/xyz.service.d/50-password.conf
           # systemctl daemon-reload
           # systemctl restart xyz.service


       systemd(1), systemd.exec(5)


        1. System and Service Credentials