man/systemd-cryptenroll.xml

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   3 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   5 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
   6 <refentry id="systemd-cryptenroll" xmlns:xi="http://www.w3.org/2001/XInclude" conditional='HAVE_LIBCRYPTSETUP'>
   7
   8   <refentryinfo>
   9     <title>systemd-cryptenroll</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd-cryptenroll</refentrytitle>
  15     <manvolnum>1</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd-cryptenroll</refname>
  20     <refpurpose>Enroll PKCS#11, FIDO2, TPM2 token/devices to LUKS2 encrypted volumes</refpurpose>
  21   </refnamediv>
  22
  23   <refsynopsisdiv>
  24     <cmdsynopsis>
  25       <command>systemd-cryptenroll</command>
  26       <arg choice="opt" rep="repeat">OPTIONS</arg>
  27       <arg choice="opt">DEVICE</arg>
  28     </cmdsynopsis>
  29   </refsynopsisdiv>
  30
  31   <refsect1>
  32     <title>Description</title>
  33
  34     <para><command>systemd-cryptenroll</command> is a tool for enrolling hardware security tokens and devices
  35     into a LUKS2 encrypted volume, which may then be used to unlock the volume during boot. Specifically, it
  36     supports tokens and credentials of the following kind to be enrolled:</para>
  37
  38     <orderedlist>
  39       <listitem><para>PKCS#11 security tokens and smartcards that may carry an RSA or EC key pair (e.g.
  40       various YubiKeys)</para></listitem>
  41
  42       <listitem><para>FIDO2 security tokens that implement the <literal>hmac-secret</literal> extension (most
  43       FIDO2 keys, including YubiKeys)</para></listitem>
  44
  45       <listitem><para>TPM2 security devices</para></listitem>
  46
  47       <listitem><para>Regular passphrases</para></listitem>
  48
  49       <listitem><para>Recovery keys. These are similar to regular passphrases, however are randomly generated
  50       on the computer and thus generally have higher entropy than user-chosen passphrases. Their character
  51       set has been designed to ensure they are easy to type in, while having high entropy. They may also be
  52       scanned off screen using QR codes. Recovery keys may be used for unlocking LUKS2 volumes wherever
  53       passphrases are accepted. They are intended to be used in combination with an enrolled hardware
  54       security token, as a recovery option when the token is lost.</para></listitem>
  55     </orderedlist>
  56
  57     <para>In addition, the tool may be used to enumerate currently enrolled security tokens and wipe a subset
  58     of them. The latter may be combined with the enrollment operation of a new security token, in order to
  59     update or replace enrollments.</para>
  60
  61     <para>The tool supports only LUKS2 volumes, as it stores token meta-information in the LUKS2 JSON token
  62     area, which is not available in other encryption formats.</para>
  63
  64     <refsect2>
  65       <title>TPM2 PCRs and policies</title>
  66
  67       <para>PCRs allow binding of the encryption of secrets to specific software versions and system state,
  68       so that the enrolled key is only accessible (may be "unsealed") if specific trusted software and/or
  69       configuration is used. Such bindings may be created with the option <option>--tpm2-pcrs=</option>
  70       described below.</para>
  71
  72       <para>Secrets may also be bound indirectly: a signed policy for a state of some combination of PCR
  73       values is provided, and the secret is bound to the public part of the key used to sign this policy.
  74       This means that the owner of a key can generate a sequence of signed policies, for specific software
  75       versions and system states, and the secret can be decrypted as long as the machine state matches one of
  76       those policies. For example, a vendor may provide such a policy for each kernel+initrd update, allowing
  77       users to encrypt secrets so that they can be decrypted when running any kernel+initrd signed by the
  78       vendor. Such bindings may be created with the options <option>--tpm2-public-key=</option>,
  79       <option>--tpm2-public-key-pcrs=</option>, <option>--tpm2-signature=</option> described below.
  80       </para>
  81
  82       <para>See <ulink url="https://uapi-group.org/specifications/specs/linux_tpm_pcr_registry/">Linux TPM
  83       PCR Registry</ulink> for an authoritative list of PCRs and how they are updated. The table below
  84       contains a quick reference, describing in particular the PCRs modified by systemd.</para>
  85
  86       <table>
  87         <title>Well-known PCR Definitions</title>
  88
  89         <!-- See: https://trustedcomputinggroup.org/resource/pc-client-specific-platform-firmware-profile-specification/ -->
  90         <!-- See: https://github.com/rhboot/shim/blob/main/README.tpm -->
  91         <!-- See: https://www.gnu.org/software/grub/manual/grub/html_node/Measured-Boot.html -->
  92         <!-- See: https://sourceforge.net/p/linux-ima/wiki/Home/ -->
  93         <!-- See: https://github.com/tianocore-docs/edk2-TrustedBootChain/blob/main/4_Other_Trusted_Boot_Chains.md -->
  94         <!-- See: https://wiki.archlinux.org/title/Trusted_Platform_Module#Accessing_PCR_registers -->
  95
  96         <tgroup cols='3' align='left' colsep='1' rowsep='1'>
  97           <colspec colname="pcr" />
  98           <colspec colname="name" />
  99           <colspec colname="definition" />
 100
 101           <thead>
 102             <row>
 103               <entry>PCR</entry>
 104               <entry>name</entry>
 105               <entry>Explanation</entry>
 106             </row>
 107           </thead>
 108
 109           <tbody>
 110             <row>
 111               <entry>0</entry>
 112               <entry>platform-code</entry>
 113               <entry>Core system firmware executable code; changes on firmware updates</entry>
 114             </row>
 115
 116             <row>
 117               <entry>1</entry>
 118               <entry>platform-config</entry>
 119               <entry>Core system firmware data/host platform configuration; typically contains serial and model numbers, changes on basic hardware/CPU/RAM replacements</entry>
 120             </row>
 121
 122             <row>
 123               <entry>2</entry>
 124               <entry>external-code</entry>
 125               <entry>Extended or pluggable executable code; includes option ROMs on pluggable hardware</entry>
 126             </row>
 127
 128             <row>
 129               <entry>3</entry>
 130               <entry>external-config</entry>
 131               <entry>Extended or pluggable firmware data; includes information about pluggable hardware</entry>
 132             </row>
 133
 134             <row>
 135               <entry>4</entry>
 136               <entry>boot-loader-code</entry>
 137               <entry>Boot loader and additional drivers, PE binaries invoked by the boot loader; changes on boot loader updates. <citerefentry><refentrytitle>sd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> measures system extension images read from the ESP here too (see <citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry>).</entry>
 138             </row>
 139
 140             <row>
 141               <entry>5</entry>
 142               <entry>boot-loader-config</entry>
 143               <entry>GPT/Partition table; changes when the partitions are added, modified, or removed</entry>
 144             </row>
 145
 146             <row>
 147               <entry>7</entry>
 148               <entry>secure-boot-policy</entry>
 149               <entry>Secure Boot state; changes when UEFI SecureBoot mode is enabled/disabled, or firmware certificates (PK, KEK, db, dbx, …) changes.</entry>
 150             </row>
 151
 152             <row>
 153               <entry>9</entry>
 154               <entry>kernel-initrd</entry>
 155               <entry>The Linux kernel measures all initrds it receives into this PCR.</entry>
 156               <!-- Strictly speaking only Linux >= 5.17 using the LOAD_FILE2 protocol, see https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f046fff8bc4c4d8f8a478022e76e40b818f692df -->
 157             </row>
 158
 159             <row>
 160               <entry>10</entry>
 161               <entry>ima</entry>
 162               <entry>The IMA project measures its runtime state into this PCR.</entry>
 163             </row>
 164
 165             <row>
 166               <entry>11</entry>
 167               <entry>kernel-boot</entry>
 168               <entry><citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> measures the ELF kernel image, embedded initrd and other payload of the PE image it is placed in into this PCR. <citerefentry><refentrytitle>systemd-pcrphase.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> measures boot phase strings into this PCR at various milestones of the boot process.</entry>
 169             </row>
 170
 171             <row>
 172               <entry>12</entry>
 173               <entry>kernel-config</entry>
 174               <entry><citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry> measures the kernel command line into this PCR. <citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> measures any manually specified kernel command line (i.e. a kernel command line that overrides the one embedded in the unified PE image) and loaded credentials into this PCR.</entry>
 175             </row>
 176
 177             <row>
 178               <entry>13</entry>
 179               <entry>sysexts</entry>
 180               <entry><citerefentry><refentrytitle>systemd-stub</refentrytitle><manvolnum>7</manvolnum></citerefentry> measures any <citerefentry><refentrytitle>systemd-sysext</refentrytitle><manvolnum>8</manvolnum></citerefentry> images it passes to the booted kernel into this PCR.</entry>
 181             </row>
 182
 183             <row>
 184               <entry>14</entry>
 185               <entry>shim-policy</entry>
 186               <entry>The shim project measures its "MOK" certificates and hashes into this PCR.</entry>
 187             </row>
 188
 189             <row>
 190               <entry>15</entry>
 191               <entry>system-identity</entry>
 192               <entry><citerefentry><refentrytitle>systemd-cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry> optionally measures the volume key of activated LUKS volumes into this PCR. <citerefentry><refentrytitle>systemd-pcrmachine.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> measures the <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> into this PCR. <citerefentry><refentrytitle>systemd-pcrfs@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> measures mount points, file system UUIDs, labels, partition UUIDs of the root and <filename>/var/</filename> filesystems into this PCR.</entry>
 193             </row>
 194
 195             <row>
 196               <entry>16</entry>
 197               <entry>debug</entry>
 198               <entry>Debug</entry>
 199             </row>
 200
 201             <row>
 202               <entry>23</entry>
 203               <entry>application-support</entry>
 204               <entry>Application Support</entry>
 205             </row>
 206           </tbody>
 207         </tgroup>
 208       </table>
 209
 210       <para>In general, encrypted volumes would be bound to some combination of PCRs 7, 11, and 14 (if
 211       shim/MOK is used). In order to allow firmware and OS version updates, it is typically not advisable to
 212       use PCRs such as 0 and 2, since the program code they cover should already be covered indirectly
 213       through the certificates measured into PCR 7. Validation through certificates hashes is typically
 214       preferable over validation through direct measurements as it is less brittle in context of OS/firmware
 215       updates: the measurements will change on every update, but signatures should remain unchanged. See the
 216       <ulink url="https://uapi-group.org/specifications/specs/linux_tpm_pcr_registry/">Linux TPM PCR
 217       Registry</ulink> for more discussion.</para>
 218     </refsect2>
 219   </refsect1>
 220
 221   <refsect1>
 222     <title>Limitations</title>
 223
 224     <para>Note that currently when enrolling a new key of one of the five supported types listed above, it is
 225     required to first provide a passphrase, a recovery key or a FIDO2 token. It's currently not supported to
 226     unlock a device with a TPM2/PKCS#11 key in order to enroll a new TPM2/PKCS#11 key. Thus, if in future key
 227     roll-over is desired it's generally recommended to ensure a passphrase, a recovery key or a FIDO2 token
 228     is always enrolled.</para>
 229
 230     <para>Also note that support for enrolling multiple FIDO2 tokens is currently limited. When multiple FIDO2
 231     tokens are enrolled, <command>systemd-cryptseup</command> will perform pre-flight requests to attempt to
 232     identify which of the enrolled tokens are currently plugged in. However, this is not possible for FIDO2
 233     tokens with user verification (UV, usually via biometrics), in which case it will fall back to attempting
 234     each enrolled token one by one. This will result in multiple prompts for PIN and user verification. This
 235     limitation does not apply to PKCS#11 tokens.</para>
 236   </refsect1>
 237
 238   <refsect1>
 239     <title>Compatibility</title>
 240
 241     <para>Security technology both in systemd and in the general industry constantly evolves. In order to
 242     provide best security guarantees, the way TPM2, FIDO2, PKCS#11 devices are enrolled is regularly updated
 243     in newer versions of systemd. Whenever this happens the following compatibility guarantees are given:</para>
 244
 245     <itemizedlist>
 246       <listitem><para>Old enrollments continue to be supported and may be unlocked with newer versions of
 247       <citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para></listitem>
 248
 249       <listitem><para>The opposite is not guaranteed however: it might not be possible to unlock volumes with
 250       enrollments done with a newer version of <command>systemd-cryptenroll</command> with an older version
 251       of <command>systemd-cryptsetup</command>.</para></listitem>
 252     </itemizedlist>
 253
 254     <para>That said, it is generally recommended to use matching versions of
 255     <command>systemd-cryptenroll</command> and <command>systemd-cryptsetup</command>, since this is best
 256     tested and supported.</para>
 257
 258     <para>It might be advisable to re-enroll existing enrollments to take benefit of newer security features,
 259     as they are added to systemd.</para>
 260   </refsect1>
 261
 262   <refsect1>
 263     <title>Options</title>
 264
 265     <para>The following options are understood:</para>
 266
 267     <variablelist>
 268       <varlistentry>
 269         <term><option>--password</option></term>
 270
 271         <listitem><para>Enroll a regular password/passphrase. This command is mostly equivalent to
 272         <command>cryptsetup luksAddKey</command>, however may be combined with
 273         <option>--wipe-slot=</option> in one call, see below.</para>
 274
 275         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 276       </varlistentry>
 277
 278       <varlistentry>
 279         <term><option>--recovery-key</option></term>
 280
 281         <listitem><para>Enroll a recovery key. Recovery keys are mostly identical to passphrases, but are
 282         computer-generated instead of being chosen by a human, and thus have a guaranteed high entropy. The
 283         key uses a character set that is easy to type in, and may be scanned off screen via a QR code.
 284         </para>
 285
 286         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 287       </varlistentry>
 288
 289       <varlistentry>
 290         <term><option>--unlock-key-file=</option><replaceable>PATH</replaceable></term>
 291
 292         <listitem><para>Use a file instead of a password/passphrase read from stdin to unlock the volume.
 293         Expects the PATH to the file containing your key to unlock the volume. Currently there is nothing like
 294         <option>--key-file-offset=</option> or <option>--key-file-size=</option> so this file has to only
 295         contain the full key.</para>
 296
 297         <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 298       </varlistentry>
 299
 300       <varlistentry>
 301         <term><option>--unlock-fido2-device=</option><replaceable>PATH</replaceable></term>
 302
 303         <listitem><para>Use a FIDO2 device instead of a password/passphrase read from stdin to unlock the
 304         volume. Expects a <filename>hidraw</filename> device referring to the FIDO2 device (e.g.
 305         <filename>/dev/hidraw1</filename>). Alternatively the special value <literal>auto</literal> may be
 306         specified, in order to automatically determine the device node of a currently plugged in security
 307         token (of which there must be exactly one). This automatic discovery is unsupported if
 308         <option>--fido2-device=</option> option is also specified.</para>
 309
 310         <xi:include href="version-info.xml" xpointer="v253"/></listitem>
 311       </varlistentry>
 312
 313       <varlistentry>
 314         <term><option>--pkcs11-token-uri=</option><replaceable>URI</replaceable></term>
 315
 316         <listitem><para>Enroll a PKCS#11 security token or smartcard (e.g. a YubiKey). Expects a PKCS#11 URI
 317         that allows to find an X.509 certificate on the token. The URI must also be suitable to find
 318         a related private key after changing the type of object in it. Alternatively the special value
 319         <literal>auto</literal> may be specified, in order to automatically determine the suitable URI if
 320         a single security token containing a single key pair is plugged in. The special value
 321         <literal>list</literal> may be used to enumerate all suitable PKCS#11 tokens currently plugged in.
 322         </para>
 323
 324         <para>The PKCS#11 token must contain an RSA or EC key pair which will be used to unlock a LUKS2 volume.
 325         For RSA, a randomly generated volume key is encrypted with a public key in the token, and stored in
 326         the LUKS2 JSON token header area. To unlock a volume, the stored encrypted volume key will be decrypted
 327         with a private key in the token. For ECC, ECDH algorithm is used: we generate a pair of EC keys in
 328         the same EC group, then derive a shared secret using the generated private key and the public key
 329         in the token. The derived shared secret is used as a volume key. The generated public key is
 330         stored in the LUKS2 JSON token header area. The generated private key is erased. To unlock a volume,
 331         we derive the shared secret with the stored public key and a private key in the token.</para>
 332
 333         <para>In order to unlock a LUKS2 volume with an enrolled PKCS#11 security token, specify the
 334         <option>pkcs11-uri=</option> option in the respective <filename>/etc/crypttab</filename> line:</para>
 335
 336         <programlisting>myvolume /dev/sda1 - pkcs11-uri=auto</programlisting>
 337
 338         <para>See
 339         <citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry> for a
 340         more comprehensive example of a <command>systemd-cryptenroll</command> invocation and its matching
 341         <filename>/etc/crypttab</filename> line.</para>
 342
 343         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 344       </varlistentry>
 345
 346       <varlistentry>
 347         <term><option>--fido2-credential-algorithm=</option><replaceable>STRING</replaceable></term>
 348         <listitem><para>Specify COSE algorithm used in credential generation. The default value is
 349         <literal>es256</literal>. Supported values are <literal>es256</literal>, <literal>rs256</literal>
 350         and <literal>eddsa</literal>.</para>
 351
 352         <para><literal>es256</literal> denotes ECDSA over NIST P-256 with SHA-256. <literal>rs256</literal>
 353         denotes 2048-bit RSA with PKCS#1.5 padding and SHA-256. <literal>eddsa</literal> denotes
 354         EDDSA over Curve25519 with SHA-512.</para>
 355
 356         <para>Note that your authenticator may not support some algorithms.</para>
 357
 358         <xi:include href="version-info.xml" xpointer="v251"/></listitem>
 359       </varlistentry>
 360
 361       <varlistentry>
 362         <term><option>--fido2-device=</option><replaceable>PATH</replaceable></term>
 363
 364         <listitem><para>Enroll a FIDO2 security token that implements the <literal>hmac-secret</literal>
 365         extension (e.g. a YubiKey). Expects a <filename>hidraw</filename> device referring to the FIDO2
 366         device (e.g. <filename>/dev/hidraw1</filename>). Alternatively the special value
 367         <literal>auto</literal> may be specified, in order to automatically determine the device node of a
 368         currently plugged in security token (of which there must be exactly one). This automatic discovery
 369         is unsupported if <option>--unlock-fido2-device=</option> option is also specified. The special value
 370         <literal>list</literal> may be used to enumerate all suitable FIDO2 tokens currently plugged in. Note
 371         that many hardware security tokens that implement FIDO2 also implement the older PKCS#11
 372         standard. Typically FIDO2 is preferable, given it's simpler to use and more modern.</para>
 373
 374         <para>In order to unlock a LUKS2 volume with an enrolled FIDO2 security token, specify the
 375         <option>fido2-device=</option> option in the respective <filename>/etc/crypttab</filename> line:</para>
 376
 377         <programlisting>myvolume /dev/sda1 - fido2-device=auto</programlisting>
 378
 379         <para>See
 380         <citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry> for a
 381         more comprehensive example of a <command>systemd-cryptenroll</command> invocation and its matching
 382         <filename>/etc/crypttab</filename> line.</para>
 383
 384         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 385       </varlistentry>
 386
 387       <varlistentry>
 388         <term><option>--fido2-with-client-pin=</option><replaceable>BOOL</replaceable></term>
 389
 390         <listitem><para>When enrolling a FIDO2 security token, controls whether to require the user to enter
 391         a PIN when unlocking the volume (the FIDO2 <literal>clientPin</literal> feature). Defaults to
 392         <literal>yes</literal>. (Note: this setting is without effect if the security token does not support
 393         the <literal>clientPin</literal> feature at all, or does not allow enabling or disabling
 394         it.)</para>
 395
 396         <xi:include href="version-info.xml" xpointer="v249"/></listitem>
 397       </varlistentry>
 398
 399       <varlistentry>
 400         <term><option>--fido2-with-user-presence=</option><replaceable>BOOL</replaceable></term>
 401
 402         <listitem><para>When enrolling a FIDO2 security token, controls whether to require the user to
 403         verify presence (tap the token, the FIDO2 <literal>up</literal> feature) when unlocking the volume.
 404         Defaults to <literal>yes</literal>. (Note: this setting is without effect if the security token does not support
 405         the <literal>up</literal> feature at all, or does not allow enabling or disabling it.)
 406         </para>
 407
 408         <xi:include href="version-info.xml" xpointer="v249"/></listitem>
 409       </varlistentry>
 410
 411       <varlistentry>
 412         <term><option>--fido2-with-user-verification=</option><replaceable>BOOL</replaceable></term>
 413
 414         <listitem><para>When enrolling a FIDO2 security token, controls whether to require user verification
 415         when unlocking the volume (the FIDO2 <literal>uv</literal> feature). Defaults to
 416         <literal>no</literal>. (Note: this setting is without effect if the security token does not support
 417         the <literal>uv</literal> feature at all, or does not allow enabling or disabling it.)</para>
 418
 419         <xi:include href="version-info.xml" xpointer="v249"/></listitem>
 420       </varlistentry>
 421
 422       <varlistentry>
 423         <term><option>--tpm2-device=</option><replaceable>PATH</replaceable></term>
 424
 425         <listitem><para>Enroll a TPM2 security chip. Expects a device node path referring to the TPM2 chip
 426         (e.g. <filename>/dev/tpmrm0</filename>). Alternatively the special value <literal>auto</literal> may
 427         be specified, in order to automatically determine the device node of a currently discovered TPM2
 428         device (of which there must be exactly one). The special value <literal>list</literal> may be used to
 429         enumerate all suitable TPM2 devices currently discovered.</para>
 430
 431         <para>In order to unlock a LUKS2 volume with an enrolled TPM2 security chip, specify the
 432         <option>tpm2-device=</option> option in the respective <filename>/etc/crypttab</filename> line:</para>
 433
 434         <programlisting>myvolume /dev/sda1 - tpm2-device=auto</programlisting>
 435
 436         <para>See
 437         <citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry> for a
 438         more comprehensive example of a <command>systemd-cryptenroll</command> invocation and its matching
 439         <filename>/etc/crypttab</filename> line.</para>
 440
 441         <para>Use <option>--tpm2-pcrs=</option> (see below) to configure which TPM2 PCR indexes to bind the
 442         enrollment to.</para>
 443
 444         <xi:include href="version-info.xml" xpointer="v248"/></listitem>
 445       </varlistentry>
 446
 447       <varlistentry>
 448         <term><option>--tpm2-device-key=</option><replaceable>PATH</replaceable></term>
 449
 450         <listitem><para>Enroll a TPM2 security chip using its public key. Expects a path referring to the
 451         TPM2 public key in TPM2B_PUBLIC format. This cannot be used with <option>--tpm2-device=</option>, as
 452         it performs the same operation, but without connecting to the TPM2 security chip; instead the
 453         enrollment is calculated using the provided TPM2 key. This is useful in situations where the TPM2
 454         security chip is not available at the time of enrollment.</para>
 455
 456         <para>The key, in most cases, should be the Storage Root Key (SRK) from a local TPM2 security
 457         chip. If a key from a different handle (not the SRK) is used, you must specify its handle index using
 458         <option>--tpm2-seal-key-handle=</option>.</para>
 459
 460         <para>The
 461         <citerefentry><refentrytitle>systemd-tpm2-setup.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 462         service writes the SRK to <filename>/run/systemd/tpm2-srk-public-key.tpm2b_public</filename>
 463         automatically during boot, in the correct format.</para>
 464
 465         <para>Alternatively, you may use <command>systemd-analyze srk</command> to retrieve the SRK from the
 466         TPM2 security chip explicitly. See
 467         <citerefentry><refentrytitle>systemd-analyze</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 468         for details. Example:</para>
 469
 470         <programlisting>systemd-analyze srk &gt; srk.tpm2b_public</programlisting>
 471
 472         <xi:include href="version-info.xml" xpointer="v255"/></listitem>
 473       </varlistentry>
 474
 475       <varlistentry>
 476         <term><option>--tpm2-seal-key-handle=</option><replaceable>HANDLE</replaceable></term>
 477
 478         <listitem><para>Configures which parent key to use for sealing, using the TPM handle (index) of the
 479         key. This is used to "seal" (encrypt) a secret and must be used later to "unseal" (decrypt) the
 480         secret. Expects a hexadecimal 32bit integer, optionally prefixed with
 481         <literal>0x</literal>. Allowable values are any handle index in the persistent
 482         (<literal>0x81000000</literal>-<literal>0x81ffffff</literal>) or transient
 483         (<literal>0x80000000</literal>-<literal>0x80ffffff</literal>) ranges. Since transient handles are
 484         lost after a TPM reset, and may be flushed during TPM context switching, they should not be used
 485         except for very specific use cases, e.g. testing.</para>
 486
 487         <para>The default is the Storage Root Key (SRK) handle index <literal>0x81000001</literal>. A value
 488         of 0 will use the default. For the SRK handle, a new key will be created and stored in the TPM if one
 489         does not already exist; for any other handle, the key must already exist in the TPM at the specified
 490         handle index.</para>
 491
 492         <para>This should not be changed unless you know what you are doing.</para>
 493
 494         <xi:include href="version-info.xml" xpointer="v255"/></listitem>
 495       </varlistentry>
 496
 497       <varlistentry>
 498         <term><option>--tpm2-pcrs=</option><arg rep="repeat">PCR</arg></term>
 499
 500         <listitem><para>Configures the TPM2 PCRs (Platform Configuration Registers) to bind to when
 501         enrollment is requested via <option>--tpm2-device=</option>. Takes a list of PCR entries, where each
 502         entry starts with a name or numeric index in the range 0…23, optionally followed by
 503         <literal>:</literal> and a hash algorithm name (specifying the PCR bank), optionally followed by
 504         <literal>=</literal> and a hash digest value. Multiple PCR entries are separated by
 505         <literal>+</literal>. If not specified, the default is to use PCR 7 only. If an empty string is
 506         specified, binds the enrollment to no PCRs at all. See the table above for a list of available
 507         PCRs.</para>
 508
 509         <para>Example: <option>--tpm2-pcrs=boot-loader-code+platform-config+boot-loader-config</option>
 510         specifies that PCR registers 4, 1, and 5 should be used.</para>
 511         <para>Example: <option>--tpm2-pcrs=7:sha256</option> specifies that PCR register 7 from the SHA256
 512         bank should be used.</para>
 513         <para>Example: <option>--tpm2-pcrs=4:sha1=3a3f780f11a4b49969fcaa80cd6e3957c33b2275</option>
 514         specifies that PCR register 4 from the SHA1 bank should be used, and a hash digest value of
 515         3a3f780f11a4b49969fcaa80cd6e3957c33b2275 will be used instead of reading the current PCR
 516         value.</para>
 517
 518         <xi:include href="version-info.xml" xpointer="v248"/>
 519         </listitem>
 520       </varlistentry>
 521
 522       <varlistentry>
 523         <term><option>--tpm2-with-pin=</option><replaceable>BOOL</replaceable></term>
 524
 525         <listitem><para>When enrolling a TPM2 device, controls whether to require the user to enter a PIN
 526         when unlocking the volume in addition to PCR binding, based on TPM2 policy authentication. Defaults
 527         to <literal>no</literal>. Despite being called PIN, any character can be used, not just numbers.
 528         </para>
 529
 530         <para>Note that incorrect PIN entry when unlocking increments the TPM dictionary attack lockout
 531         mechanism, and may lock out users for a prolonged time, depending on its configuration. The lockout
 532         mechanism is a global property of the TPM, <command>systemd-cryptenroll</command> does not control or
 533         configure the lockout mechanism. You may use tpm2-tss tools to inspect or configure the dictionary
 534         attack lockout, with <citerefentry
 535         project='mankier'><refentrytitle>tpm2_getcap</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 536         and <citerefentry
 537         project='mankier'><refentrytitle>tpm2_dictionarylockout</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 538         commands, respectively.</para>
 539
 540         <xi:include href="version-info.xml" xpointer="v251"/></listitem>
 541       </varlistentry>
 542
 543       <varlistentry>
 544         <term><option>--tpm2-public-key=</option><arg>PATH</arg></term>
 545         <term><option>--tpm2-public-key-pcrs=</option><arg rep="repeat">PCR</arg></term>
 546         <term><option>--tpm2-signature=</option><arg>PATH</arg></term>
 547
 548         <listitem><para>Configures a TPM2 signed PCR policy to bind encryption to. The
 549         <option>--tpm2-public-key=</option> option accepts a path to a PEM encoded RSA public key, to bind
 550         the encryption to. If this is not specified explicitly, but a file
 551         <filename>tpm2-pcr-public-key.pem</filename> exists in one of the directories
 552         <filename>/etc/systemd/</filename>, <filename>/run/systemd/</filename>,
 553         <filename>/usr/lib/systemd/</filename> (searched in this order), it is automatically used. The
 554         <option>--tpm2-public-key-pcrs=</option> option takes a list of TPM2 PCR indexes to bind to (same
 555         syntax as <option>--tpm2-pcrs=</option> described above). If not specified defaults to 11 (i.e. this
 556         binds the policy to any unified kernel image for which a PCR signature can be provided).</para>
 557
 558         <para>Note the difference between <option>--tpm2-pcrs=</option> and
 559         <option>--tpm2-public-key-pcrs=</option>: the former binds decryption to the current, specific PCR
 560         values; the latter binds decryption to any set of PCR values for which a signature by the specified
 561         public key can be provided. The latter is hence more useful in scenarios where software updates shell
 562         be possible without losing access to all previously encrypted LUKS2 volumes. Like with
 563         <option>--tpm2-pcrs=</option>, names defined in the table above can also be used to specify the
 564         registers, for instance
 565         <option>--tpm2-public-key-pcrs=boot-loader-code+system-identity</option>.</para>
 566
 567         <para>The <option>--tpm2-signature=</option> option takes a path to a TPM2 PCR signature file as
 568         generated by the
 569         <citerefentry><refentrytitle>systemd-measure</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 570         tool. If this is not specified explicitly, a suitable signature file
 571         <filename>tpm2-pcr-signature.json</filename> is searched for in <filename>/etc/systemd/</filename>,
 572         <filename>/run/systemd/</filename>, <filename>/usr/lib/systemd/</filename> (in this order) and used.
 573         If a signature file is specified or found it is used to verify if the volume can be unlocked with it
 574         given the current PCR state, before the new slot is written to disk. This is intended as safety net
 575         to ensure that access to a volume is not lost if a public key is enrolled for which no valid
 576         signature for the current PCR state is available. If the supplied signature does not unlock the
 577         current PCR state and public key combination, no slot is enrolled and the operation will fail. If no
 578         signature file is specified or found no such safety verification is done.</para>
 579
 580         <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 581       </varlistentry>
 582
 583       <varlistentry>
 584         <term><option>--tpm2-pcrlock=</option><arg>PATH</arg></term>
 585
 586         <listitem><para>Configures a TPM2 pcrlock policy to bind encryption to. Expects a path to a pcrlock
 587         policy file as generated by the
 588         <citerefentry><refentrytitle>systemd-pcrlock</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 589         tool. If a TPM2 device is enrolled and this option is not used but a file
 590         <filename>pcrlock.json</filename> is found in <filename>/run/systemd/</filename> or
 591         <filename>/var/lib/systemd/</filename> it is automatically used. Assign an empty string to turn this
 592         behaviour off.</para>
 593
 594         <xi:include href="version-info.xml" xpointer="v255"/></listitem>
 595       </varlistentry>
 596
 597       <varlistentry>
 598         <term><option>--wipe-slot=</option><arg rep="repeat">SLOT</arg></term>
 599
 600         <listitem><para>Wipes one or more LUKS2 key slots. Takes a comma separated list of numeric slot
 601         indexes, or the special strings <literal>all</literal> (for wiping all key slots),
 602         <literal>empty</literal> (for wiping all key slots that are unlocked by an empty passphrase),
 603         <literal>password</literal> (for wiping all key slots that are unlocked by a traditional passphrase),
 604         <literal>recovery</literal> (for wiping all key slots that are unlocked by a recovery key),
 605         <literal>pkcs11</literal> (for wiping all key slots that are unlocked by a PKCS#11 token),
 606         <literal>fido2</literal> (for wiping all key slots that are unlocked by a FIDO2 token),
 607         <literal>tpm2</literal> (for wiping all key slots that are unlocked by a TPM2 chip), or any
 608         combination of these strings or numeric indexes, in which case all slots matching either are
 609         wiped. As safety precaution an operation that wipes all slots without exception (so that the volume
 610         cannot be unlocked at all anymore, unless the volume key is known) is refused.</para>
 611
 612         <para>This switch may be used alone, in which case only the requested wipe operation is executed. It
 613         may also be used in combination with any of the enrollment options listed above, in which case the
 614         enrollment is completed first, and only when successful the wipe operation executed — and the newly
 615         added slot is always excluded from the wiping. Combining enrollment and slot wiping may thus be used to
 616         update existing enrollments:</para>
 617
 618         <programlisting>systemd-cryptenroll /dev/sda1 --wipe-slot=tpm2 --tpm2-device=auto</programlisting>
 619
 620         <para>The above command will enroll the TPM2 chip, and then wipe all previously created TPM2
 621         enrollments on the LUKS2 volume, leaving only the newly created one. Combining wiping and enrollment
 622         may also be used to replace enrollments of different types, for example for changing from a PKCS#11
 623         enrollment to a FIDO2 one:</para>
 624
 625         <programlisting>systemd-cryptenroll /dev/sda1 --wipe-slot=pkcs11 --fido2-device=auto</programlisting>
 626
 627         <para>Or for replacing an enrolled empty password by TPM2:</para>
 628
 629         <programlisting>systemd-cryptenroll /dev/sda1 --wipe-slot=empty --tpm2-device=auto</programlisting>
 630
 631         <xi:include href="version-info.xml" xpointer="v248"/>
 632         </listitem>
 633       </varlistentry>
 634
 635       <xi:include href="standard-options.xml" xpointer="help" />
 636       <xi:include href="standard-options.xml" xpointer="version" />
 637     </variablelist>
 638
 639   </refsect1>
 640
 641   <refsect1>
 642     <title>Exit status</title>
 643
 644     <para>On success, 0 is returned, a non-zero failure code otherwise.</para>
 645   </refsect1>
 646
 647   <refsect1>
 648     <title>Examples</title>
 649
 650     <para><citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry> and
 651     <citerefentry><refentrytitle>systemd-measure</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 652     contain various examples employing <command>systemd-cryptenroll</command>.</para>
 653   </refsect1>
 654
 655   <refsect1>
 656     <title>See Also</title>
 657     <para><simplelist type="inline">
 658       <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 659       <member><citerefentry><refentrytitle>systemd-cryptsetup@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 660       <member><citerefentry><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum></citerefentry></member>
 661       <member><citerefentry project='die-net'><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
 662       <member><citerefentry><refentrytitle>systemd-measure</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
 663      </simplelist></para>
 664   </refsect1>
 665
 666 </refentry>