freebsd-src/sbin/veriexec/veriexec.8

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.Dd August 1, 2024
.Dt VERIEXEC 8
.Os
.Sh NAME
.Nm veriexec
.Nd manipulate state of mac_veriexec
.Sh SYNOPSIS
.Nm
.Op Fl v
.Op Fl C Ar directory
.Op Fl S
.Pa manifest
.Nm
.Fl z Ar state
.Nm
.Fl i Ar state
.Nm
.Fl l
.Ar file ...
.Nm
.Fl x
.Ar file ...
.Sh DESCRIPTION
.Nm
is a utility to query or manipulate the state of
.Xr mac_veriexec 4 .
.Pp
The first form is for loading a
.Pa manifest .
.Nm
first verifies a digital signature of the
.Ar manifest
and if successful, parses it and feeds its content to kernel.
The
.Fl S
flag indicates that certificate validity should be checked.
Without this, a valid signature with an expired certificate
will still be accepted.
.Pp
The second form with
.Fl z
is used to modify the
.Ar state ,
and with
.Fl i
to query the current
.Ar state .
.Pp
With
.Fl l
.Nm
will report any labels associated with the remaining arguments
assumed to be files.
If only a single file argument is given, the bare label (if any)
will be reported, otherwise the pathname followed by label.
.Pp
The final form with
.Fl x
is used to test whether
.Ar file
is verified or not.
This requires
.Xr mac_veriexec 4
to be in the
.Ql active
or
.Ql enforce
state.
.Pp
The possible states
are:
.Bl -tag -width enforce
.It Ar loaded
set automatically when the first
.Pa manifest
has been loaded.
.It Ar active
.Xr mac_veriexec 4
will begin checking files.
This state can only be entered from the
.Ar loaded
state.
.It Ar enforce
.Xr mac_veriexec 4
will fail attempts to
.Xr exec 2
or
.Xr open 2
files with
.Dv O_VERIFY
unless verified.
.It Ar locked
prevent loading of any more manifests.
.El
.Pp
When setting or querying the state, it is sufficient to provide
a unique prefix of the desired state.
So
.Fl i
.Ar a
or
.Fl z
.Ar e
are sufficient, but
.Fl i
.Ar loc
is the minimum required to avoid confusion with
.Ar loaded .
.Sh MANIFESTS
The manifest contains a mapping of relative pathnames to fingerprints
with optional flags.
For example:
.Bd -literal -offset indent
sbin/veriexec sha256=f22136...c0ff71 no_ptrace trusted
usr/bin/python sha256=5944d9...876525 indirect
sbin/somedaemon sha256=77fc2f...63f5687 label=mod1/val1,mod2/val2
.Ed
.Pp
The supported flags are:
.Bl -tag -width indirect
.It Ql indirect
the executable cannot be run directly,
but can be used as an interpreter for example via:
.Bd -literal -offset indent
#!/usr/bin/python
.Ed
.It Ql no_fips
If the system has a notion of running in FIPS mode,
a file marked with this flag will not be allowed to
exec.
.It Ql no_ptrace
do not allow running executable under a debugger.
Useful for any application critical to the security state of system.
.It Ql trusted
this flag is required for a process to use
.Xr veriexec 4
to interact with
.Xr mac_veriexec 4 .
Generally only
.Nm
should need this flag.
Implies
.Ql no_ptrace .

.El
.Pp
The
.Ql label
argument allows associating a
.Xr maclabel 7
with a file.
Neither
.Nm
nor
.Xr mac_veriexec 4
(if it supports labels)
pay any attention to the content of the label
they are provided for the use of other
.Xr mac 4
modules or indeed other applications.
.Sh EXAMPLES
Load the manifest for a
.Xr tarfs 5
package mounted on
.Pa /mnt
and be strict about enforcing certificate validity:
.Bd -literal -offset indent
# veriexec -S -C /mnt /mnt/manifest

.Ed
.Nm
will look for a detatched signature that it recognizes, such as
.Pa manifest.asc
(OpenPGP) or
.Pa manifest.*sig
(X.509).
In the case of an X.509 signature we also need a matching certificate chain
.Pa manifest.*certs .
In either case there needs to be a suitable trust anchor in the trust store.
.Pp
We can now activate:
.Bd -literal -offset indent
# veriexec -z active

.Ed
Any user can check if
.Xr mac_veriexec 4
is
.Ql active :
.Bd -literal -offset indent
$ veriexec -i active

.Ed
Any user can check that
.Pa /mnt/bin/app
is verified:
.Bd -literal -offset indent
$ veriexec -x /mnt/bin/app

.Ed
If it is not, we will get an Authentiaction error,
but unless
.Xr mac_veriexec 4
is enforcing we would still be able to run it.
.Sh NOTES
It is only safe to set
.Xr mac_veriexec 4
to
.Ql enforce
state, if sufficient manifests have been loaded
to cover all the applications that might need to be run.
.Sh HISTORY
The Verified Exec system first appeared in
.Nx .
This utility derives from the one found in Junos,
which requires that manifest files be digitally signed.