`fido2_is_cred_in_specific_token()` should simply not return error codes
for non-fatal errors. For example, `-ENODEV` can be safely translated to
a `false` return value. When the pre-flight request is not supported, we
should simply return true to instruct the caller to attempt to use the
device anyway.
All error codes returned by the funtion should now be fatal and logged
at error level. Non-fatal errors should only appear in debug logs.
This prevents unnecessary user interactions when `fido2-device` is set to
something other than `auto` -- a case overlooked in the original PR #23577
(and later #25268).
We do not move pre-flight checks to `fido2_use_hmac_hash_specific_token`
because the behaviors are different between different cases: when the
device path is NULL, we try to automatically choose the correct device,
in which case pre-flight errors should be "soft" errors, without
spamming the tty with error outputs; but when a specific device path is
given, a pre-flight request that determined the non-existence of the
credential should be treated the same as a failed assertion request.
According to the FIDO2 spec, tokens may not support pre-flight checks
for credentials requiring UV, at least not without at least
`pinUvAuthParam` or `uv = true`. Originally, in #25268, this was
handled by passing a PIN to satisfy `pinUvAuthParams`, but this is not
ideal, since `pinUvAuthParam` can be obtained from either a PIN
or a UV verification. Forcing the user to enter the PIN here (which is
often just the fallback option on UV devices) is no better than just
trying out each device with the actual assertion request.
As a result, this commit disables pre-flight checks when the credential
requires UV, and instead reverts to the old behavior (trying out each
device and each key slot, requiring multiple user interactions) for this
type of credentials.
Do not attempt to decrypt using a key slot unless its corresponding
credential is found on an available FIDO2 token. Avoids multiple touches
/ confirmations when unlocking a LUKS2 device with multiple FIDO2 tokens
enrolled.
Partially fixes#19208 (when the libcryptsetup plugin is in use).
We currently have a convoluted and complex selection of which random
numbers to use. We can simplify this down to two functions that cover
all of our use cases:
1) Randomness for crypto: this one needs to wait until the RNG is
initialized. So it uses getrandom(0). If that's not available, it
polls on /dev/random, and then reads from /dev/urandom. This function
returns whether or not it was successful, as before.
2) Randomness for other things: this one uses getrandom(GRND_INSECURE).
If it's not available it uses getrandom(GRND_NONBLOCK). And if that
would block, then it falls back to /dev/urandom. And if /dev/urandom
isn't available, it uses the fallback code. It never fails and
doesn't return a value.
These two cases match all the uses of randomness inside of systemd.
I would prefer to make both of these return void, and get rid of the
fallback code, and simply assert in the incredibly unlikely case that
/dev/urandom doesn't exist. But Luca disagrees, so this commit attempts
to instead keep case (1) returning a return value, which all the callers
already check, and fix the fallback code in (2) to be less bad than
before.
For the less bad fallback code for (2), we now use auxval and some
timestamps, together with various counters representing the invocation,
hash it all together and provide the output. Provided that AT_RANDOM is
secure, this construction is probably okay too, though notably it
doesn't have any forward secrecy. Fortunately, it's only used by
random_bytes() and not by crypto_random_bytes().
These functions are used pretty much independently of locale, i.e. the
only info relevant is whether th locale is UTF-8 or not. Hence let's
give this its own pair of .c/.h files.
FIDO2 device access is serialised by libfido2 using flock().
Therefore, make sure to close a FIDO2 device once we are done
with it, or we risk opening it again at a later point and
deadlocking. Fixes#20664.
We warn when the operation fails, not when it succeeds. Hence this should be
"<do>_or_<handle failure>", not "<do>_and_<handle failure>". We *could* use
whatever convention we want, but rust and perl are rather consistent in using
the logical convention. We don't care about perl that much, but having a naming
convention inverted wrt. rust would be rather confusing.
Also, pretty much every implementation does similar steps, so add a nice
wrapper which combines opening of the library and loading of the symbols.
Also add missing sentinel attribute in dlopen_or_warn().
Let's show the touch emoji whenever the user is likely going to have to
interact with the security token. We had this at many but not all such
messages. Let's add it everywhere.
Also, upgrade all messages where the user is supposed to do something to
LOG_NOTICE. Previously some where at LOG_NOTICE and others at LOG_INFO.
These messages are more than informational after all, they require user
action, hence deserve the higher prio, in particular as that formats
them bold with our usual log coloring.
Always use the word "test" in log messages, instead of "check".
Finally, always use the same wording: "confirm presence on security
token" for "up" and "verify user on security token" for "uv"
Let's improve compatibility with systemd 248 enrollments of FIDO2 keys:
if we have no information about the up/uv/pin settings, let's try to
determine them automatically, i.e. use up and pin if needed.
This only has an effect on LUKS2 volumes where a FIDO2 key was enrolled
with systemd 248 and thus the JSON data lacks the up/uv/pin fields. It
also matters if the user configured FIDO2 parameters explicitly via
crypttab options, so that the JSON data is not used.
For newer enrollments we'll stick to the explicit settings, as that's
generally much safer and robust.
We need really need to trust the feature set, since we are about to set
it in stone storing the result in JSON, hence react a bit more allergic
about token that misadvertise the feature.
Note that I added this to be defensive, I am not aware any token that
actually misadvertises this. hence it should be safe to make this fatal,
and should this not work we can always revisit things.
Let's try to handle keys gracefully that do not implement all features
we ask for: simply turn the feature off, and continue.
This is in particular relevant since we enroll with PIN and UP by
default, and on devices that don't support that we should just work.
Replaces: #18509
Some tokens support authorization via fingerprint or other biometric
ID. Add support for "user verification" to cryptenroll and cryptsetup.
Disable by default, as it is still quite uncommon.
In some cases user presence might not be required to get _a_
secret out of a FIDO2 device, but it might be required to
the get actual secret that was used to lock the volume.
Record whether we used it in the LUKS header JSON metadata.
Let the cryptenroll user ask for the feature, but bail out if it is
required by the token and the user disabled it.
Enabled by default.
Closes: https://github.com/systemd/systemd/issues/19246
Some FIDO2 devices allow the user to choose whether to use a PIN or not
and will HMAC with a different secret depending on the choice.
Some other devices (or some device-specific configuration) can instead
make it mandatory.
Allow the cryptenroll user to choose whether to use a PIN or not, but
fail immediately if it is a hard requirement.
Record the choice in the JSON-encoded LUKS header metadata so that the
right set of options can be used on unlock.
This adds generic support for the SetCredential=/LoadCredential= logic
to our password querying infrastructure: if a password is requested by a
program that has a credential store configured via
$CREDENTIALS_DIRECTORY we'll look in it for a password.
The "systemd-ask-password" tool is updated with an option to specify the
credential to look for.
Dmitry V. Levin
Peter Cai
MkfsSion
Zbigniew Jędrzejewski-Szmek
Jason A. Donenfeld
Yu Watanabe
Lennart Poettering
pedro martelletto
Luca Boccassi