1SYSTEMD-CREDS(1) systemd-creds SYSTEMD-CREDS(1)
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6 systemd-creds - Lists, shows, encrypts and decrypts service credentials
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9 systemd-creds [OPTIONS...] COMMAND [ARGS...]
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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 initial
107 RAM disk (initrd) of the system encryption with the host key is not
108 appropriate since access to the host key is typically not available
109 from the initrd. Thus, for such credentials only the TPM2 key
110 should be used.
111 Encrypted credentials are always encoded in Base64.
113 Use decrypt (see below) to undo the encryption operation, and
115 acquire the decrypted plaintext credential from the encrypted
116 ciphertext credential.
117 The credential data is encrypted using AES256-GCM, i.e. providing
119 both confidentiality and integrity, keyed by a SHA256 hash of one
120 or both of the secret keys described above.
121 decrypt input|- [output|-]
123 Undoes the effect of the encrypt operation: loads the specified
124 (encrypted ciphertext) input credential file, decrypts and
125 authenticates it and writes the (decrypted plaintext) output to the
126 specified target credential file.
127 Takes one or two file system paths. The file name part of the input
129 path is compared with the credential name embedded in the encrypted
130 file. If it does not match decryption fails. This is done in order
131 to ensure that encrypted credentials are not re-purposed without
132 this being detected. The credential name to compare with the
133 embedded credential name may also be overridden with the --name=
134 switch. If the input path is specified as "-", the encrypted
135 credential is read from standard input. If only one path is
136 specified or the output path specified as "-", the decrypted
137 credential is written to standard output. In this mode, the
138 expected name embedded in the credential cannot be derived from the
139 path and should be specified explicitly with --name=.
140 Decrypting credentials requires access to the original TPM2 chip
142 and/or credentials host key, see above. Information about which
143 keys are required is embedded in the encrypted credential data, and
144 thus decryption is entirely automatic.
145 has-tpm2
147 Reports whether the system is equipped with a TPM2 device usable
148 for protecting credentials. If a TPM2 device has been discovered,
149 is supported, and is being used by firmware, by the OS kernel
150 drivers and by userspace (i.e. systemd) this prints "yes" and exits
151 with exit status zero. If no such device is
152 discovered/supported/used, prints "no". Otherwise prints "partial".
153 In either of these two cases exits with non-zero exit status. It
154 also shows four lines indicating separately whether firmware,
155 drivers, the system and the kernel discovered/support/use TPM2.
156 Combine with --quiet to suppress the output.
158 -h, --help
160 Print a short help text and exit.
161 --version
163 Print a short version string and exit.
164
166 --system
167 When specified with the list and cat commands operates on the
168 credentials passed to system as a whole instead of on those passed
169 to the current execution context. This is useful in container
170 environments where credentials may be passed in from the container
171 manager.
172 --transcode=
174 When specified with the cat or decrypt commands, transcodes the
175 output before showing it. Takes one of "base64", "unbase64", "hex"
176 or "unhex" as argument, in order to encode/decode the credential
177 data with Base64 or as series of hexadecimal values.
178 Note that this has no effect on the encrypt command, as encrypted
180 credentials are unconditionally encoded in Base64.
181 --newline=
183 When specified with cat or decrypt controls whether to add a
184 trailing newline character to the end of the output if it doesn't
185 end in one, anyway. Takes one of "auto", "yes" or "no". The default
186 mode of "auto" will suffix the output with a single newline
187 character only when writing credential data to a TTY.
188 --pretty, -p
190 When specified with encrypt controls whether to show the encrypted
191 credential as SetCredentialEncrypted= setting that may be pasted
192 directly into a unit file.
193 --name=name
195 When specified with the encrypt command controls the credential
196 name to embed in the encrypted credential data. If not specified
197 the name is chosen automatically from the filename component of the
198 specified output path. If specified as empty string no credential
199 name is embedded in the encrypted credential, and no verification
200 of credential name is done when the credential is decrypted.
201 When specified with the decrypt command control the credential name
203 to validate the credential name embedded in the encrypted
204 credential with. If not specified the name is chosen automatically
205 from the filename component of the specified input path. If no
206 credential name is embedded in the encrypted credential file (i.e.
207 the --name= with an empty string was used when encrypted) the
208 specified name has no effect as no credential name validation is
209 done.
210 Embedding the credential name in the encrypted credential is done
212 in order to protect against reuse of credentials for purposes they
213 weren't originally intended for, under the assumption the
214 credential name is chosen carefully to encode its intended purpose.
215 --timestamp=timestamp
217 When specified with the encrypt command controls the timestamp to
218 embed into the encrypted credential. Defaults to the current time.
219 Takes a timestamp specification in the format described in
220 systemd.time(7).
221 When specified with the decrypt command controls the timestamp to
223 use to validate the "not-after" timestamp that was configured with
224 --not-after= during encryption. If not specified defaults to the
225 current system time.
226 --not-after=timestamp
228 When specified with the encrypt command controls the time when the
229 credential shall not be used anymore. This embeds the specified
230 timestamp in the encrypted credential. During decryption the
231 timestamp is checked against the current system clock, and if the
232 timestamp is in the past the decryption will fail. By default no
233 such timestamp is set. Takes a timestamp specification in the
234 format described in systemd.time(7).
235 --with-key=, -H, -T
237 When specified with the encrypt command controls the
238 encryption/signature key to use. Takes one of "host", "tpm2",
239 "host+tpm2", "tpm2-absent", "auto", "auto-initrd". See above for
240 details on the three key types. If set to "auto" (which is the
241 default) the TPM2 key is used if a TPM2 device is found and not
242 running in a container. The host key is used if /var/lib/systemd/
243 is on persistent media. This means on typical systems the
244 encryption is by default bound to both the TPM2 chip and the OS
245 installation, and both need to be available to decrypt the
246 credential again. If "auto" is selected but neither TPM2 is
247 available (or running in container) nor /var/lib/systemd/ is on
248 persistent media, encryption will fail. If set to "tpm2-absent" a
249 fixed zero length key is used (thus, in this mode no
250 confidentiality nor authenticity are provided!). This logic is
251 useful to cover for systems that lack a TPM2 chip but where
252 credentials shall be generated. Note that decryption of such
253 credentials is refused on systems that have a TPM2 chip and where
254 UEFI SecureBoot is enabled (this is done so that such a locked down
255 system cannot be tricked into loading a credential generated this
256 way that lacks authentication information). If set to "auto-initrd"
257 a TPM2 key is used if a TPM2 is found. If not a fixed zero length
258 key is used, equivalent to "tpm2-absent" mode. This option is
259 particularly useful to generate credentials files that are
260 encrypted/authenticated against TPM2 where available but still work
261 on systems lacking support for this.
262 The -H switch is a shortcut for --with-key=host. Similar, -T is a
264 shortcut for --with-key=tpm2.
265 When encrypting credentials that shall be used in the initial RAM
267 disk (initrd) where /var/lib/systemd/ is typically not available
268 make sure to use --with-key=auto-initrd mode, to disable binding
269 against the host secret.
270 This switch has no effect on the decrypt command, as information on
272 which key to use for decryption is included in the encrypted
273 credential already.
274 --tpm2-device=PATH
276 Controls the TPM2 device to use. Expects a device node path
277 referring to the TPM2 chip (e.g. /dev/tpmrm0). Alternatively the
278 special value "auto" may be specified, in order to automatically
279 determine the device node of a suitable TPM2 device (of which there
280 must be exactly one). The special value "list" may be used to
281 enumerate all suitable TPM2 devices currently discovered.
282 --tpm2-pcrs= [PCR...]
284 Configures the TPM2 PCRs (Platform Configuration Registers) to bind
285 the encryption key to. Takes a "+" separated list of numeric PCR
286 indexes in the range 0...23. If not used, defaults to PCR 7 only.
287 If an empty string is specified, binds the encryption key to no
288 PCRs at all. For details about the PCRs available, see the
289 documentation of the switch of the same name for systemd-
290 cryptenroll(1).
291 --quiet, -q
293 When used with has-tpm2 suppresses the output, and only returns an
294 exit status indicating support for TPM2.
295 --no-pager
297 Do not pipe output into a pager.
298 --no-legend
300 Do not print the legend, i.e. column headers and the footer with
301 hints.
302 --json=MODE
304 Shows output formatted as JSON. Expects one of "short" (for the
305 shortest possible output without any redundant whitespace or line
306 breaks), "pretty" (for a pretty version of the same, with
307 indentation and line breaks) or "off" (to turn off JSON output, the
308 default).
309
311 On success, 0 is returned.
312 In case of the has-tpm2 command returns 0 if a TPM2 device is
314 discovered, supported and used by firmware, driver, and userspace (i.e.
315 systemd). Otherwise returns the OR combination of the value 1 (in case
316 firmware support is missing), 2 (in case driver support is missing) and
317 4 (in case userspace support is missing). If no TPM2 support is
318 available at all, value 7 is hence returned.
319
321 Example 1. Encrypt a password for use as credential
322 The following command line encrypts the specified password "hunter2",
324 writing the result to a file password.cred.
325 # echo -n hunter2 | systemd-creds encrypt - password.cred
327 This decrypts the file password.cred again, revealing the literal
329 password:
330 # systemd-creds decrypt password.cred
332 hunter2
333 Example 2. Encrypt a password and include it in a unit file
335 The following command line prompts the user for a password and
337 generates a SetCredentialEncrypted= line from it for a credential named
338 "mysql-password", suitable for inclusion in a unit file.
339 # systemd-ask-password -n | systemd-creds encrypt --name=mysql-password -p - -
341 🔐 Password: ****
342 SetCredentialEncrypted=mysql-password: \
343 k6iUCUh0RJCQyvL8k8q1UyAAAAABAAAADAAAABAAAAASfFsBoPLIm/dlDoGAAAAAAAAAA \
344 NAAAAAgAAAAAH4AILIOZ3w6rTzYsBy9G7liaCAd4i+Kpvs8mAgArzwuKxd0ABDjgSeO5k \
345 mKQc58zM94ZffyRmuNeX1lVHE+9e2YD87KfRFNoDLS7F3YmCb347gCiSk2an9egZ7Y0Xs \
346 700Kr6heqQswQEemNEc62k9RJnEl2q7SbcEYguegnPQUATgAIAAsAAAASACA/B90W7E+6 \
347 yAR9NgiIJvxr9bpElztwzB5lUJAxtMBHIgAQACCaSV9DradOZz4EvO/LSaRyRSq2Hj0ym \
348 gVJk/dVzE8Uxj8H3RbsT7rIBH02CIgm/Gv1ukSXO3DMHmVQkDG0wEciyageTfrVEer8z5 \
349 9cUQfM5ynSaV2UjeUWEHuz4fwDsXGLB9eELXLztzUU9nsAyLvs3ZRR+eEK/A==
350 The generated line can be pasted 1:1 into a unit file, and will ensure
352 the acquired password will be made available in the
353 $CREDENTIALS_DIRECTORY/mysql-password credential file for the started
354 service.
355 Utilizing the unit file drop-in logic this can be used to securely pass
357 a password credential to a unit. A similar, more comprehensive set of
358 commands to insert a password into a service xyz.service:
359 # mkdir -p /etc/systemd/system/xyz.service.d
361 # systemd-ask-password -n | systemd-creds encrypt --name=mysql-password -p - - > /etc/systemd/system/xyz.service.d/50-password.conf
362 # systemctl daemon-reload
363 # systemctl restart xyz.service
364
366 systemd(1), systemd.exec(5)
367
369 1. System and Service Credentials
370 https://systemd.io/CREDENTIALS
371systemd 251 SYSTEMD-CREDS(1)