1SYSTEMD-CREDS(1) systemd-creds SYSTEMD-CREDS(1)
2
6 systemd-creds - Lists, shows, encrypts and decrypts service credentials
7
9 systemd-creds [OPTIONS...] COMMAND [ARGS...]
10
12 systemd-creds is a tool for listing, showing, encrypting and decrypting
13 unit credentials. Credentials are limited-size binary or textual
14 objects that may be passed to unit processes. They are primarily used
15 for passing cryptographic keys (both public and private) or
16 certificates, user account information or identity information from the
17 host to services.
18 Credentials are configured in unit files via the LoadCredential=,
20 SetCredential=, LoadCredentialEncrypted= and SetCredentialEncrypted=
21 settings, see systemd.exec(5) for details.
22 For further information see System and Service Credentials[1]
24 documentation.
25
27 The following commands are understood:
28 list
30 Show a list of credentials passed into the current execution
31 context. This command shows the files in the directory referenced
32 by the $CREDENTIALS_DIRECTORY environment variable, and is intended
33 to be executed from within service context.
34 Along with each credential name, the size and security state is
36 shown. The latter is one of "secure" (in case the credential is
37 backed by unswappable memory, i.e. "ramfs"), "weak" (in case it is
38 backed by any other type of memory), or "insecure" (if having any
39 access mode that is not 0400, i.e. if readable by anyone but the
40 owner).
41 cat credential...
43 Show contents of specified credentials passed into the current
44 execution context. Takes one or more credential names, whose
45 contents shall be written to standard output.
46 When combined with --json= or --transcode= the output is transcoded
48 in simple ways before outputting.
49 setup
51 Generates a host encryption key for credentials, if one has not
52 been generated already. This ensures the
53 /var/lib/systemd/credential.secret file is initialized with a
54 random secret key if it doesn't exist yet. This secret key is used
55 when encrypting/decrypting credentials with encrypt or decrypt, and
56 is only accessible to the root user. Note that there's typically no
57 need to invoke this command explicitly as it is implicitly called
58 when encrypt is invoked, and credential host key encryption
59 selected.
60 encrypt input|- output|-
62 Loads the specified (unencrypted plaintext) input credential file,
63 encrypts it and writes the (encrypted ciphertext) output to the
64 specified target credential file. The resulting file may be
65 referenced in the LoadCredentialEncrypted= setting in unit files,
66 or its contents used literally in SetCredentialEncrypted= settings.
67 Takes two file system paths. The file name part of the output path
69 is embedded as name in the encrypted credential, to ensure
70 encrypted credentials cannot be renamed and reused for different
71 purposes without this being noticed. The credential name to embed
72 may be overridden with the --name= setting. The input or output
73 paths may be specified as "-", in which case the credential data is
74 read from/written to standard input and standard output. If the
75 output path is specified as "-" the credential name cannot be
76 derived from the file system path, and thus should be specified
77 explicitly via the --name= switch.
78 The credential data is encrypted and authenticated symmetrically
80 with one of the following encryption keys:
81 1. A secret key automatically derived from the system's TPM2 chip.
83 This encryption key is not stored on the host system and thus
84 decryption is only possible with access to the original TPM2
85 chip. Or in other words, the credential secured in this way can
86 only be decrypted again by the local machine.
87 2. A secret key stored in the /var/lib/systemd/credential.secret
89 file which is only accessible to the root user. This "host"
90 encryption key is stored on the host file system, and thus
91 decryption is possible with access to the host file system and
92 sufficient privileges. The key is automatically generated when
93 needed, but can also be created explicitly with the setup
94 command, see above.
95 3. A combination of the above: an encryption key derived from both
97 the TPM2 chip and the host file system. This means decryption
98 requires both access to the original TPM2 chip and the OS
99 installation. This is the default mode of operation if a TPM2
100 chip is available and /var/lib/systemd/ resides on persistent
101 media.
102 Which of the three keys shall be used for encryption may be
104 configured with the --with-key= switch. Depending on the use-case
105 for the encrypted credential the key to use may differ. For
106 example, for credentials that shall be accessible from the initrd,
107 encryption with the host key is not appropriate, since access to
108 the host key is typically not available from the initrd. Thus, for
109 such credentials only the TPM2 key should be used.
110 Encrypted credentials are always encoded in Base64.
112 Use decrypt (see below) to undo the encryption operation, and
114 acquire the decrypted plaintext credential from the encrypted
115 ciphertext credential.
116 The credential data is encrypted using AES256-GCM, i.e. providing
118 both confidentiality and integrity, keyed by a SHA256 hash of one
119 or both of the secret keys described above.
120 decrypt input|- [output|-]
122 Undoes the effect of the encrypt operation: loads the specified
123 (encrypted ciphertext) input credential file, decrypts and
124 authenticates it and writes the (decrypted plaintext) output to the
125 specified target credential file.
126 Takes one or two file system paths. The file name part of the input
128 path is compared with the credential name embedded in the encrypted
129 file. If it does not match decryption fails. This is done in order
130 to ensure that encrypted credentials are not re-purposed without
131 this being detected. The credential name to compare with the
132 embedded credential name may also be overridden with the --name=
133 switch. If the input path is specified as "-", the encrypted
134 credential is read from standard input. If only one path is
135 specified or the output path specified as "-", the decrypted
136 credential is written to standard output. In this mode, the
137 expected name embedded in the credential cannot be derived from the
138 path and should be specified explicitly with --name=.
139 Decrypting credentials requires access to the original TPM2 chip
141 and/or credentials host key, see above. Information about which
142 keys are required is embedded in the encrypted credential data, and
143 thus decryption is entirely automatic.
144 has-tpm2
146 Reports whether the system is equipped with a TPM2 device usable
147 for protecting credentials. If a TPM2 device has been discovered,
148 is supported, and is being used by firmware, by the OS kernel
149 drivers and by userspace (i.e. systemd) this prints "yes" and exits
150 with exit status zero. If no such device is
151 discovered/supported/used, prints "no". Otherwise prints "partial".
152 In either of these two cases exits with non-zero exit status. It
153 also shows four lines indicating separately whether firmware,
154 drivers, the system and the kernel discovered/support/use TPM2.
155 Combine with --quiet to suppress the output.
157 -h, --help
159 Print a short help text and exit.
160 --version
162 Print a short version string and exit.
163
165 --system
166 When specified with the list and cat commands operates on the
167 credentials passed to system as a whole instead of on those passed
168 to the current execution context. This is useful in container
169 environments where credentials may be passed in from the container
170 manager.
171 --transcode=
173 When specified with the cat or decrypt commands, transcodes the
174 output before showing it. Takes one of "base64", "unbase64", "hex"
175 or "unhex" as argument, in order to encode/decode the credential
176 data with Base64 or as series of hexadecimal values.
177 Note that this has no effect on the encrypt command, as encrypted
179 credentials are unconditionally encoded in Base64.
180 --newline=
182 When specified with cat or decrypt controls whether to add a
183 trailing newline character to the end of the output if it doesn't
184 end in one, anyway. Takes one of "auto", "yes" or "no". The default
185 mode of "auto" will suffix the output with a single newline
186 character only when writing credential data to a TTY.
187 --pretty, -p
189 When specified with encrypt controls whether to show the encrypted
190 credential as SetCredentialEncrypted= setting that may be pasted
191 directly into a unit file.
192 --name=name
194 When specified with the encrypt command controls the credential
195 name to embed in the encrypted credential data. If not specified
196 the name is chosen automatically from the filename component of the
197 specified output path. If specified as empty string no credential
198 name is embedded in the encrypted credential, and no verification
199 of credential name is done when the credential is decrypted.
200 When specified with the decrypt command control the credential name
202 to validate the credential name embedded in the encrypted
203 credential with. If not specified the name is chosen automatically
204 from the filename component of the specified input path. If no
205 credential name is embedded in the encrypted credential file (i.e.
206 the --name= with an empty string was used when encrypted) the
207 specified name has no effect as no credential name validation is
208 done.
209 Embedding the credential name in the encrypted credential is done
211 in order to protect against reuse of credentials for purposes they
212 weren't originally intended for, under the assumption the
213 credential name is chosen carefully to encode its intended purpose.
214 --timestamp=timestamp
216 When specified with the encrypt command controls the timestamp to
217 embed into the encrypted credential. Defaults to the current time.
218 Takes a timestamp specification in the format described in
219 systemd.time(7).
220 When specified with the decrypt command controls the timestamp to
222 use to validate the "not-after" timestamp that was configured with
223 --not-after= during encryption. If not specified defaults to the
224 current system time.
225 --not-after=timestamp
227 When specified with the encrypt command controls the time when the
228 credential shall not be used anymore. This embeds the specified
229 timestamp in the encrypted credential. During decryption the
230 timestamp is checked against the current system clock, and if the
231 timestamp is in the past the decryption will fail. By default no
232 such timestamp is set. Takes a timestamp specification in the
233 format described in systemd.time(7).
234 --with-key=, -H, -T
236 When specified with the encrypt command controls the
237 encryption/signature key to use. Takes one of "host", "tpm2",
238 "host+tpm2", "tpm2-absent", "auto", "auto-initrd". See above for
239 details on the three key types. If set to "auto" (which is the
240 default) the TPM2 key is used if a TPM2 device is found and not
241 running in a container. The host key is used if /var/lib/systemd/
242 is on persistent media. This means on typical systems the
243 encryption is by default bound to both the TPM2 chip and the OS
244 installation, and both need to be available to decrypt the
245 credential again. If "auto" is selected but neither TPM2 is
246 available (or running in container) nor /var/lib/systemd/ is on
247 persistent media, encryption will fail. If set to "tpm2-absent" a
248 fixed zero length key is used (thus, in this mode no
249 confidentiality nor authenticity are provided!). This logic is
250 useful to cover for systems that lack a TPM2 chip but where
251 credentials shall be generated. Note that decryption of such
252 credentials is refused on systems that have a TPM2 chip and where
253 UEFI SecureBoot is enabled (this is done so that such a locked down
254 system cannot be tricked into loading a credential generated this
255 way that lacks authentication information). If set to "auto-initrd"
256 a TPM2 key is used if a TPM2 is found. If not a fixed zero length
257 key is used, equivalent to "tpm2-absent" mode. This option is
258 particularly useful to generate credentials files that are
259 encrypted/authenticated against TPM2 where available but still work
260 on systems lacking support for this.
261 The -H switch is a shortcut for --with-key=host. Similar, -T is a
263 shortcut for --with-key=tpm2.
264 When encrypting credentials that shall be used in the initrd (where
266 /var/lib/systemd/ is typically not available) make sure to use
267 --with-key=auto-initrd mode, to disable binding against the host
268 secret.
269 This switch has no effect on the decrypt command, as information on
271 which key to use for decryption is included in the encrypted
272 credential already.
273 --tpm2-device=PATH
275 Controls the TPM2 device to use. Expects a device node path
276 referring to the TPM2 chip (e.g. /dev/tpmrm0). Alternatively the
277 special value "auto" may be specified, in order to automatically
278 determine the device node of a suitable TPM2 device (of which there
279 must be exactly one). The special value "list" may be used to
280 enumerate all suitable TPM2 devices currently discovered.
281 --tpm2-pcrs= [PCR...]
283 Configures the TPM2 PCRs (Platform Configuration Registers) to bind
284 the encryption key to. Takes a "+" separated list of numeric PCR
285 indexes in the range 0...23. If not used, defaults to PCR 7 only.
286 If an empty string is specified, binds the encryption key to no
287 PCRs at all. For details about the PCRs available, see the
288 documentation of the switch of the same name for systemd-
289 cryptenroll(1).
290 --tpm2-public-key= [PATH], --tpm2-public-key-pcrs= [PCR...]
292 Configures a TPM2 signed PCR policy to bind encryption to, for use
293 with the encrypt command. The --tpm2-public-key= option accepts a
294 path to a PEM encoded RSA public key, to bind the encryption to. If
295 this is not specified explicitly, but a file
296 tpm2-pcr-public-key.pem exists in one of the directories
297 /etc/systemd/, /run/systemd/, /usr/lib/systemd/ (searched in this
298 order), it is automatically used. The --tpm2-public-key-pcrs=
299 option takes a list of TPM2 PCR indexes to bind to (same syntax as
300 --tpm2-pcrs= described above). If not specified defaults to 11
301 (i.e. this binds the policy to any unified kernel image for which a
302 PCR signature can be provided).
303 Note the difference between --tpm2-pcrs= and
305 --tpm2-public-key-pcrs=: the former binds decryption to the
306 current, specific PCR values; the latter binds decryption to any
307 set of PCR values for which a signature by the specified public key
308 can be provided. The latter is hence more useful in scenarios where
309 software updates shall be possible without losing access to all
310 previously encrypted secrets.
311 --tpm2-signature= [PATH]
313 Takes a path to a TPM2 PCR signature file as generated by the
314 systemd-measure(1) tool and that may be used to allow the decrypt
315 command to decrypt credentials that are bound to specific signed
316 PCR values. If this is not specified explicitly, and a credential
317 with a signed PCR policy is attempted to be decrypted, a suitable
318 signature file tpm2-pcr-signature.json is searched for in
319 /etc/systemd/, /run/systemd/, /usr/lib/systemd/ (in this order) and
320 used.
321 --quiet, -q
323 When used with has-tpm2 suppresses the output, and only returns an
324 exit status indicating support for TPM2.
325 --no-pager
327 Do not pipe output into a pager.
328 --no-legend
330 Do not print the legend, i.e. column headers and the footer with
331 hints.
332 --json=MODE
334 Shows output formatted as JSON. Expects one of "short" (for the
335 shortest possible output without any redundant whitespace or line
336 breaks), "pretty" (for a pretty version of the same, with
337 indentation and line breaks) or "off" (to turn off JSON output, the
338 default).
339
341 On success, 0 is returned.
342 In case of the has-tpm2 command returns 0 if a TPM2 device is
344 discovered, supported and used by firmware, driver, and userspace (i.e.
345 systemd). Otherwise returns the OR combination of the value 1 (in case
346 firmware support is missing), 2 (in case driver support is missing) and
347 4 (in case userspace support is missing). If no TPM2 support is
348 available at all, value 7 is hence returned.
349
351 Example 1. Encrypt a password for use as credential
352 The following command line encrypts the specified password "hunter2",
354 writing the result to a file password.cred.
355 # echo -n hunter2 | systemd-creds encrypt - password.cred
357 This decrypts the file password.cred again, revealing the literal
359 password:
360 # systemd-creds decrypt password.cred
362 hunter2
363 Example 2. Encrypt a password and include it in a unit file
365 The following command line prompts the user for a password and
367 generates a SetCredentialEncrypted= line from it for a credential named
368 "mysql-password", suitable for inclusion in a unit file.
369 # systemd-ask-password -n | systemd-creds encrypt --name=mysql-password -p - -
371 🔐 Password: ****
372 SetCredentialEncrypted=mysql-password: \
373 k6iUCUh0RJCQyvL8k8q1UyAAAAABAAAADAAAABAAAAASfFsBoPLIm/dlDoGAAAAAAAAAA \
374 NAAAAAgAAAAAH4AILIOZ3w6rTzYsBy9G7liaCAd4i+Kpvs8mAgArzwuKxd0ABDjgSeO5k \
375 mKQc58zM94ZffyRmuNeX1lVHE+9e2YD87KfRFNoDLS7F3YmCb347gCiSk2an9egZ7Y0Xs \
376 700Kr6heqQswQEemNEc62k9RJnEl2q7SbcEYguegnPQUATgAIAAsAAAASACA/B90W7E+6 \
377 yAR9NgiIJvxr9bpElztwzB5lUJAxtMBHIgAQACCaSV9DradOZz4EvO/LSaRyRSq2Hj0ym \
378 gVJk/dVzE8Uxj8H3RbsT7rIBH02CIgm/Gv1ukSXO3DMHmVQkDG0wEciyageTfrVEer8z5 \
379 9cUQfM5ynSaV2UjeUWEHuz4fwDsXGLB9eELXLztzUU9nsAyLvs3ZRR+eEK/A==
380 The generated line can be pasted 1:1 into a unit file, and will ensure
382 the acquired password will be made available in the
383 $CREDENTIALS_DIRECTORY/mysql-password credential file for the started
384 service.
385 Utilizing the unit file drop-in logic this can be used to securely pass
387 a password credential to a unit. A similar, more comprehensive set of
388 commands to insert a password into a service xyz.service:
389 # mkdir -p /etc/systemd/system/xyz.service.d
391 # systemd-ask-password -n | ( echo "[Service]" && systemd-creds encrypt --name=mysql-password -p - - ) >/etc/systemd/system/xyz.service.d/50-password.conf
392 # systemctl daemon-reload
393 # systemctl restart xyz.service
394
396 systemd(1), systemd.exec(5), systemd-measure(1)
397
399 1. System and Service Credentials
400 https://systemd.io/CREDENTIALS
401systemd 253 SYSTEMD-CREDS(1)