Add a salt to the pin and store it in the TPM2 LUKS header for future
this. This adds entropy to user supplied pins and helps brute forcing
the passphrase on the key residing in the TPM or brute forcing bind key
encrypted sessions with low entropy passphrases.
Signed-off-by: malikabhi05 <abhishek.malik@intel.com>
Signed-off-by: William Roberts <william.c.roberts@intel.com>
Let's introduce a common implementation of a function that checks
whether we are booted on a kernel with systemd-stub that has TPM PCR
measurements enabled. Do our own userspace measurements only if we
detect that.
PCRs are scarce and most likely there are projects which already make
use of them in other ways. Hence, instead of blindly stepping into their
territory let's conditionalize things so that people have to explicitly
buy into our PCR assignments before we start measuring things into them.
Specifically bind everything to an UKI that reported measurements.
This was previously already implemented in systemd-pcrphase, but with
this change we expand this to all tools that process PCR measurement
settings.
The env var to override the check is renamed to SYSTEMD_FORCE_MEASURE,
to make it more generic (since we'll use it at multiple places now).
This is not a compat break, since the original env var for that was not
included in any stable release yet.
These options allow measuring the volume key used for unlocking the
volume to a TPM2 PCR. This is ideally used for the volume key of the
root file system and can then be used to bind other resources to the
root file system volume in a secure way.
See: #24503
This returns an ssize_t, not an int. On populare archs that's the
difference between 64bit and 32bit. hence, let's be more careful here,
and not silently drop half the bits on the ground by assigning the
return value to "int".
As noticed by @malikabhi05:
https://github.com/systemd/systemd/pull/24754#discussion_r1062903159
`acquire_fido2_key_auto()` will not be used in PLAIN mode, and
parameters such as the salt will be acquired from the LUKS header.
Parameters intended for PLAIN mode are useless in
`acquire_fido2_key_auto()`.
After #25268, it is now possible to check whether a credential
is present on a FIDO2 token without actually attempting to retrieve said
credential. However, when cryptsetup plugins are not enabled, the
fallback unlock routines are not able to make multiple attempts with
multiple different FIDO2 key slots.
Instead of looking for one FIDO2 key slot when trying to unlock, we now
attempt to use all key slots applicable.
Fixes#19208.
This works becuase TPM2_FLAGS_USE_PIN is 1 and bool is a 1 so the bits
line up as expected, however if for some reason flags change values and
for clarity check if the boolean indicates this flag and pass the flag
value.
Signed-off-by: William Roberts <william.c.roberts@intel.com>
This splits out the JSON parser used by the systemd-cryptsetup code.
This is preparation for later work to reuse it in the tpm2 cryptsetup
token module, which currently uses a separate but very similar parser
for the same data.
No change in behaviour.
Traditionally, TPM2 PCR policies are bound against literal PCR values,
which makes them hard to work with when updating software that is
measured into PCRs: each update will change the PCR values, and thus
break TPM2 policies of existing objects.
Let's improve the situation: let's allow signed PCR policies. Secrets
and other TPM2 objects can be associated with a public key that signs a
PCR policy. Thus, if the signed policy and the public key is presented,
access to the TPM2 object can be granted. This allows a less brittle
handling of updates: for example, whenever a kernel image is updated a
new signed PCR policy can be shipped along with it, signed by a private
key owned by the kernel vendor (ideally: same private key that is used
to sign the kernel image itself). TPM2 objects can then be bound to the
associated public key, thus allowing objects that can only be unlocked
by kernels of the same vendor. This makes it very easy to update kernels
without affecting locked secrets.
This does not hook up any of the consuming code (just passes NULL/0
everywhere). This is for later commits.
Add a new tpm2_parse_pcr_argument() helper that unifies how we merge PCR
masks in a single function, we can use all over the place. Previously we
had basically the same code for this at 4 places.
Previously the env var was only checked when conditionalizing use of our
own libcryptsetup loadable token modules. But let's also use it for any
other kind of token module, including possible internal ones by
libcryptsetup.
Instead of always asking for passphrase, if the device has LUKS2 header check:
- If only regular passphrases are registered, ask for passphrase.
- If only recovery keys are registered, ask for recovery key.
- If both regular passphrases and recovery keys are registered, ask for
passphrase or recovery key.
crypt_activate_by_token() fails with ENOANO if the token is protected with a
PIN, in this case we need to call crypt_activate_by_token_pin() with a PIN.
This logic is already implemented in
crypt_activate_by_token_pin_ask_password().
This code path is relevant when using systemd-gpt-auto-generator because there
is no a priory information about the type of the used security device, so
systemd-cryptsetup tries to unlock the volume using the corresponding
cryptsetup plugin.
Use the helper function introduced in the previous commit ("cryptsetup:
implement cryptsetup_token_open_pin for systemd-tpm2 LUKS2 token") for
cryptsetup-token-systemd-tpm2.
This finishes the implementation started in commit
1f895adac2 ("cryptsetup: add libcryptsetup TPM2
PIN support").
Note that the previous implementation took a shortcut by returning EOPNOTSUPP
instead of the correct ENOANO as per the cryptsetup documentation. This meant
that systemd-cryptsetup fell back to the non-plugin implementation in order to
ask for the PIN. Since this does not happen any more when returning ENOANO, we
need to ask for the PIN in attach_luks2_by_tpm2_via_plugin() instead like
attach_luks2_by_fido2_via_plugin() does.
```
...
../src/cryptsetup/cryptsetup-tokens/cryptsetup-token-systemd-fido2.c:33:13: error: variable 'r' set but not used [-Werror,-Wunused-but-set-variable]
int r;
^
1 error generated.
...
../src/cryptsetup/cryptsetup-tokens/cryptsetup-token-systemd-pkcs11.c:34:13: error: variable 'r' set but not used [-Werror,-Wunused-but-set-variable]
int r;
^
1 error generated.
ninja: build stopped: subcommand failed.
+ fatal ''\''meson compile'\'' failed with -Db_ndebug=true'
```
Let's upgrade log levels of some noteworthy messages from LOG_DEBUG to
LOG_NOTICE. These messages contain information that previous log
messages in the error path didn't say, namely that we'll now fall back
to traditional unlocking.
Note that this leaves similar log messages for cases where
TPM2/PKCS#11/FIDO2 support is disabled at build at LOG_DEBUG, since in
that case nothing really failed, we just systematically can't do
TPM2/PKCS#11/FIDO2 and hence it is pointless and not actionable for
users to do anything about it...
The are so many different flavours of functions that attach volumes,
hence say explicitly that these are about libcryptsetup plugins, and
nothing else.
Just some renaming, no code changes beyond that.
Some refactoring: split efi-loader.[ch] in two: isolate the calls that
implement out boot loader interface spec, and those which implement
access to upstream UEFI firmware features.
They are quite different in nature and behaviour, and even semantically
it makes to keep these two separate. At the very least because the
previous name "efi-loader.[ch]" suggests all was about loader-specific
APIs, but much of it is generic uefi stuff...
While we are at it, I renamed a bunch of return parameters to follow our
usual ret_xyz naming. But besides renaming no real code changes.
Handle the case where TPM2 metadata is not available and explicitly
provided in crypttab. This adds a new "tpm2-pin" option to crypttab
options for this purpose.
This is unfinished: we don't have any way to actually query for PINs
interactively this way. It is similar to FIDO2 and PKCS#11 in this
regard.
Nonetheless, this code is capable of validating and dumping tokens, so
it is already useful as-is.
Modify TPM2 authentication policy to optionally include an authValue, i.e.
a password/PIN. We use the "PIN" terminology since it's used by other
systems such as Windows, even though the PIN is not necessarily numeric.
The pin is hashed via SHA256 to allow for arbitrary length PINs.
v2: fix tpm2_seal in sd-repart
v3: applied review feedback
The new helper combines a bunch of steps every invocation of
unsetenv_erase() did so far: getenv() + strdup() + unsetenv_erase().
Let's unify this into one helper that is harder to use incorrectly. It's
in inspired by TAKE_PTR() in a way: get the env var out and invalidate
where it was before.
Lennart Poettering
Yu Watanabe
William Roberts
Peter Cai
Daan De Meyer
Zbigniew Jędrzejewski-Szmek
David Tardon
Jan Janssen
Antonio Alvarez Feijoo
Chih-Hsuan Yen
Jonas Witschel
Frantisek Sumsal
Michael Biebl
Grigori Goronzy