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| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" |
| "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
| <!-- SPDX-License-Identifier: LGPL-2.1-or-later --> |
| |
| <refentry id="systemd-creds" |
| xmlns:xi="http://www.w3.org/2001/XInclude"> |
| |
| <refentryinfo> |
| <title>systemd-creds</title> |
| <productname>systemd</productname> |
| </refentryinfo> |
| |
| <refmeta> |
| <refentrytitle>systemd-creds</refentrytitle> |
| <manvolnum>1</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>systemd-creds</refname> |
| <refpurpose>Lists, shows, encrypts and decrypts service credentials</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <cmdsynopsis> |
| <command>systemd-creds</command> |
| <arg choice="opt" rep="repeat">OPTIONS</arg> |
| <arg choice="plain">COMMAND</arg> |
| <arg choice="opt" rep="repeat">ARGS</arg> |
| </cmdsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para><command>systemd-creds</command> 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.</para> |
| |
| <para>Credentials are configured in unit files via the <varname>LoadCredential=</varname>, |
| <varname>SetCredential=</varname>, <varname>LoadCredentialEncrypted=</varname> and |
| <varname>SetCredentialEncrypted=</varname> settings, see |
| <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for |
| details.</para> |
| |
| <para>For further information see <ulink url="https://systemd.io/CREDENTIALS">System and Service |
| Credentials</ulink> documentation.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Commands</title> |
| |
| <para>The following commands are understood:</para> |
| |
| <variablelist> |
| <varlistentry> |
| <term><command>list</command></term> |
| |
| <listitem><para>Show a list of credentials passed into the current execution context. This command |
| shows the files in the directory referenced by the <varname>$CREDENTIALS_DIRECTORY</varname> |
| environment variable, and is intended to be executed from within service context.</para> |
| |
| <para>Along with each credential name, the size and security state is shown. The latter is one of |
| <literal>secure</literal> (in case the credential is backed by unswappable memory, |
| i.e. <literal>ramfs</literal>), <literal>weak</literal> (in case it is backed by any other type of |
| memory), or <literal>insecure</literal> (if having any access mode that is not 0400, i.e. if readable |
| by anyone but the owner).</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><command>cat</command> <replaceable>credential...</replaceable></term> |
| |
| <listitem><para>Show contents of specified credentials passed into the current execution |
| context. Takes one or more credential names, whose contents shall be written to standard |
| output.</para> |
| |
| <para>When combined with <option>--json=</option> or <option>--transcode=</option> the output is |
| transcoded in simple ways before outputting.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><command>setup</command></term> |
| |
| <listitem><para>Generates a host encryption key for credentials, if one has not been generated |
| already. This ensures the <filename>/var/lib/systemd/credential.secret</filename> file is initialized |
| with a random secret key if it doesn't exist yet. This secret key is used when encrypting/decrypting |
| credentials with <command>encrypt</command> or <command>decrypt</command>, 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 <command>encrypt</command> is invoked, and credential host key encryption |
| selected.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><command>encrypt</command> <replaceable>input|-</replaceable> <replaceable>output|-</replaceable></term> |
| |
| <listitem><para>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 <varname>LoadCredentialEncrypted=</varname> setting in unit files, or its |
| contents used literally in <varname>SetCredentialEncrypted=</varname> settings.</para> |
| |
| <para>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 |
| <option>--name=</option> setting. The input or output paths may be specified as <literal>-</literal>, |
| in which case the credential data is read from/written to standard input and standard output. If the |
| output path is specified as <literal>-</literal> the credential name cannot be derived from the file |
| system path, and thus should be specified explicitly via the <option>--name=</option> switch.</para> |
| |
| <para>The credential data is encrypted and authenticated symmetrically with one of the following |
| encryption keys:</para> |
| |
| <orderedlist> |
| <listitem><para>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.</para></listitem> |
| |
| <listitem><para>A secret key stored in the <filename>/var/lib/systemd/credential.secret</filename> |
| 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 <command>setup</command> command, see above.</para></listitem> |
| |
| <listitem><para>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 |
| <filename>/var/lib/systemd/</filename> resides on persistent media.</para></listitem> |
| </orderedlist> |
| |
| <para>Which of the three keys shall be used for encryption may be configured with the |
| <option>--with-key=</option> 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 initrd, 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.</para> |
| |
| <para>Encrypted credentials are always encoded in Base64.</para> |
| |
| <para>Use <command>decrypt</command> (see below) to undo the encryption operation, and acquire the |
| decrypted plaintext credential from the encrypted ciphertext credential.</para> |
| |
| <para>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 above.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><command>decrypt</command> <replaceable>input|-</replaceable> |
| <optional><replaceable>output|-</replaceable></optional></term> |
| |
| <listitem><para>Undoes the effect of the <command>encrypt</command> 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.</para> |
| |
| <para>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 |
| <option>--name=</option> switch. If the input path is specified as <literal>-</literal>, the |
| encrypted credential is read from standard input. If only one path is specified or the output path |
| specified as <literal>-</literal>, 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 <option>--name=</option>.</para> |
| |
| <para>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.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><command>has-tpm2</command></term> |
| |
| <listitem><para>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 <literal>yes</literal> and exits |
| with exit status zero. If no such device is discovered/supported/used, prints |
| <literal>no</literal>. Otherwise prints <literal>partial</literal>. In either of these two cases |
| exits with non-zero exit status. It also shows four lines indicating separately whether firmware, |
| drivers, the system and the kernel discovered/support/use TPM2.</para> |
| |
| <para>Combine with <option>--quiet</option> to suppress the output.</para></listitem> |
| </varlistentry> |
| |
| <xi:include href="standard-options.xml" xpointer="help" /> |
| <xi:include href="standard-options.xml" xpointer="version" /> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Options</title> |
| |
| <variablelist> |
| |
| <varlistentry> |
| <term><option>--system</option></term> |
| |
| <listitem><para>When specified with the <command>list</command> and <command>cat</command> 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 manager.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--transcode=</option></term> |
| |
| <listitem><para>When specified with the <command>cat</command> or <command>decrypt</command> |
| commands, transcodes the output before showing it. Takes one of <literal>base64</literal>, |
| <literal>unbase64</literal>, <literal>hex</literal> or <literal>unhex</literal> as argument, in order |
| to encode/decode the credential data with Base64 or as series of hexadecimal values.</para> |
| |
| <para>Note that this has no effect on the <command>encrypt</command> command, as encrypted |
| credentials are unconditionally encoded in Base64.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--newline=</option></term> |
| |
| <listitem><para>When specified with <command>cat</command> or <command>decrypt</command> 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 <literal>auto</literal>, <literal>yes</literal> or <literal>no</literal>. The |
| default mode of <literal>auto</literal> will suffix the output with a single newline character only |
| when writing credential data to a TTY.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--pretty</option></term> |
| <term><option>-p</option></term> |
| |
| <listitem><para>When specified with <command>encrypt</command> controls whether to show the encrypted |
| credential as <varname>SetCredentialEncrypted=</varname> setting that may be pasted directly into a |
| unit file.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--name=</option><replaceable>name</replaceable></term> |
| |
| <listitem><para>When specified with the <command>encrypt</command> 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.</para> |
| |
| <para>When specified with the <command>decrypt</command> 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 <option>--name=</option> with an empty string |
| was used when encrypted) the specified name has no effect as no credential name validation is |
| done.</para> |
| |
| <para>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.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--timestamp=</option><replaceable>timestamp</replaceable></term> |
| |
| <listitem><para>When specified with the <command>encrypt</command> command controls the timestamp to |
| embed into the encrypted credential. Defaults to the current time. Takes a timestamp specification in |
| the format described in |
| <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para> |
| |
| <para>When specified with the <command>decrypt</command> command controls the timestamp to use to |
| validate the "not-after" timestamp that was configured with <option>--not-after=</option> during |
| encryption. If not specified defaults to the current system time.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--not-after=</option><replaceable>timestamp</replaceable></term> |
| |
| <listitem><para>When specified with the <command>encrypt</command> 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 |
| <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--with-key=</option></term> |
| <term><option>-H</option></term> |
| <term><option>-T</option></term> |
| |
| <listitem><para>When specified with the <command>encrypt</command> command controls the |
| encryption/signature key to use. Takes one of <literal>host</literal>, <literal>tpm2</literal>, |
| <literal>host+tpm2</literal>, <literal>tpm2-absent</literal>, <literal>auto</literal>, |
| <literal>auto-initrd</literal>. See above for details on the three key types. If set to |
| <literal>auto</literal> (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 <filename>/var/lib/systemd/</filename> 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 |
| <literal>auto</literal> is selected but neither TPM2 is available (or running in container) nor |
| <filename>/var/lib/systemd/</filename> is on persistent media, encryption will fail. If set to |
| <literal>tpm2-absent</literal> 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 <literal>auto-initrd</literal> a TPM2 key is used if a TPM2 is found. If not |
| a fixed zero length key is used, equivalent to <literal>tpm2-absent</literal> 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.</para> |
| |
| <para>The <option>-H</option> switch is a shortcut for <option>--with-key=host</option>. Similar, |
| <option>-T</option> is a shortcut for <option>--with-key=tpm2</option>.</para> |
| |
| <para>When encrypting credentials that shall be used in the initrd (where |
| <filename>/var/lib/systemd/</filename> is typically not available) make sure to use |
| <option>--with-key=auto-initrd</option> mode, to disable binding against the host secret.</para> |
| |
| <para>This switch has no effect on the <command>decrypt</command> command, as information on which |
| key to use for decryption is included in the encrypted credential already.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--tpm2-device=</option><replaceable>PATH</replaceable></term> |
| |
| <listitem><para>Controls the TPM2 device to use. Expects a device node path referring to the TPM2 |
| chip (e.g. <filename>/dev/tpmrm0</filename>). Alternatively the special value <literal>auto</literal> |
| 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 <literal>list</literal> may be used to enumerate |
| all suitable TPM2 devices currently discovered.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--tpm2-pcrs=</option><arg rep="repeat">PCR</arg></term> |
| |
| <listitem><para>Configures the TPM2 PCRs (Platform Configuration Registers) to bind the encryption |
| key to. Takes a <literal>+</literal> 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 |
| <citerefentry><refentrytitle>systemd-cryptenroll</refentrytitle><manvolnum>1</manvolnum></citerefentry>.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--tpm2-public-key=</option><arg>PATH</arg></term> |
| <term><option>--tpm2-public-key-pcrs=</option><arg rep="repeat">PCR</arg></term> |
| |
| <listitem><para>Configures a TPM2 signed PCR policy to bind encryption to, for use with the |
| <command>encrypt</command> command. The <option>--tpm2-public-key=</option> option accepts a path to |
| a PEM encoded RSA public key, to bind the encryption to. If this is not specified explicitly, but a |
| file <filename>tpm2-pcr-public-key.pem</filename> exists in one of the directories |
| <filename>/etc/systemd/</filename>, <filename>/run/systemd/</filename>, |
| <filename>/usr/lib/systemd/</filename> (searched in this order), it is automatically used. The |
| <option>--tpm2-public-key-pcrs=</option> option takes a list of TPM2 PCR indexes to bind to (same |
| syntax as <option>--tpm2-pcrs=</option> described above). If not specified defaults to 11 (i.e. this |
| binds the policy to any unified kernel image for which a PCR signature can be provided).</para> |
| |
| <para>Note the difference between <option>--tpm2-pcrs=</option> and |
| <option>--tpm2-public-key-pcrs=</option>: the former binds decryption to the current, specific PCR |
| values; the latter binds decryption to any set of PCR values for which a signature by the specified |
| public key can be provided. The latter is hence more useful in scenarios where software updates shall |
| be possible without losing access to all previously encrypted secrets.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--tpm2-signature=</option><arg>PATH</arg></term> |
| |
| <listitem><para>Takes a path to a TPM2 PCR signature file as generated by the |
| <citerefentry><refentrytitle>systemd-measure</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| tool and that may be used to allow the <command>decrypt</command> command to decrypt credentials that |
| are bound to specific signed PCR values. If this is not specified explicitly, and a credential |
| with a signed PCR policy is attempted to be decrypted, a suitable signature file |
| <filename>tpm2-pcr-signature.json</filename> is searched for in <filename>/etc/systemd/</filename>, |
| <filename>/run/systemd/</filename>, <filename>/usr/lib/systemd/</filename> (in this order) and |
| used.</para></listitem> |
| </varlistentry> |
| |
| <varlistentry> |
| <term><option>--quiet</option></term> |
| <term><option>-q</option></term> |
| |
| <listitem><para>When used with <command>has-tpm2</command> suppresses the output, and only returns an |
| exit status indicating support for TPM2.</para></listitem> |
| </varlistentry> |
| |
| <xi:include href="standard-options.xml" xpointer="no-pager" /> |
| <xi:include href="standard-options.xml" xpointer="no-legend" /> |
| <xi:include href="standard-options.xml" xpointer="json" /> |
| </variablelist> |
| </refsect1> |
| |
| <refsect1> |
| <title>Exit status</title> |
| |
| <para>On success, 0 is returned.</para> |
| |
| <para>In case of the <command>has-tpm2</command> 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.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Examples</title> |
| |
| <example> |
| <title>Encrypt a password for use as credential</title> |
| |
| <para>The following command line encrypts the specified password <literal>hunter2</literal>, writing the result |
| to a file <filename>password.cred</filename>.</para> |
| |
| <programlisting># echo -n hunter2 | systemd-creds encrypt - password.cred</programlisting> |
| |
| <para>This decrypts the file <filename>password.cred</filename> again, revealing the literal password:</para> |
| |
| <programlisting># systemd-creds decrypt password.cred |
| hunter2</programlisting> |
| </example> |
| |
| <example> |
| <title>Encrypt a password and include it in a unit file</title> |
| |
| <para>The following command line prompts the user for a password and generates a |
| <varname>SetCredentialEncrypted=</varname> line from it for a credential named |
| <literal>mysql-password</literal>, suitable for inclusion in a unit file.</para> |
| |
| <programlisting># systemd-ask-password -n | systemd-creds encrypt --name=mysql-password -p - - |
| 🔐 Password: **** |
| SetCredentialEncrypted=mysql-password: \ |
| k6iUCUh0RJCQyvL8k8q1UyAAAAABAAAADAAAABAAAAASfFsBoPLIm/dlDoGAAAAAAAAAA \ |
| NAAAAAgAAAAAH4AILIOZ3w6rTzYsBy9G7liaCAd4i+Kpvs8mAgArzwuKxd0ABDjgSeO5k \ |
| mKQc58zM94ZffyRmuNeX1lVHE+9e2YD87KfRFNoDLS7F3YmCb347gCiSk2an9egZ7Y0Xs \ |
| 700Kr6heqQswQEemNEc62k9RJnEl2q7SbcEYguegnPQUATgAIAAsAAAASACA/B90W7E+6 \ |
| yAR9NgiIJvxr9bpElztwzB5lUJAxtMBHIgAQACCaSV9DradOZz4EvO/LSaRyRSq2Hj0ym \ |
| gVJk/dVzE8Uxj8H3RbsT7rIBH02CIgm/Gv1ukSXO3DMHmVQkDG0wEciyageTfrVEer8z5 \ |
| 9cUQfM5ynSaV2UjeUWEHuz4fwDsXGLB9eELXLztzUU9nsAyLvs3ZRR+eEK/A==</programlisting> |
| |
| <para>The generated line can be pasted 1:1 into a unit file, and will ensure the acquired password will |
| be made available in the <varname>$CREDENTIALS_DIRECTORY</varname><filename>/mysql-password</filename> |
| credential file for the started service.</para> |
| |
| <para>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 |
| <filename>xyz.service</filename>:</para> |
| |
| <programlisting># 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</programlisting> |
| </example> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd-measure</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |
