New setcred() system call and associated MAC hooks

This new system call allows to set all necessary credentials of
a process in one go: Effective, real and saved UIDs, effective, real and
saved GIDs

New setcred() system call and associated MAC hooks

This new system call allows to set all necessary credentials of
a process in one go: Effective, real and saved UIDs, effective, real and
saved GIDs, supplementary groups and the MAC label. Its advantage over
standard credential-setting system calls (such as setuid(), seteuid(),
etc.) is that it enables MAC modules, such as MAC/do, to restrict the
set of credentials some process may gain in a fine-grained manner.

Traditionally, credential changes rely on setuid binaries that call
multiple credential system calls and in a specific order (setuid() must
be last, so as to remain root for all other credential-setting calls,
which would otherwise fail with insufficient privileges). This
piecewise approach causes the process to transiently hold credentials
that are neither the original nor the final ones. For the kernel to
enforce that only certain transitions of credentials are allowed, either
these possibly non-compliant transient states have to disappear (by
setting all relevant attributes in one go), or the kernel must delay
setting or checking the new credentials. Delaying setting credentials
could be done, e.g., by having some mode where the standard system calls
contribute to building new credentials but without committing them. It
could be started and ended by a special system call. Delaying checking
could mean that, e.g., the kernel only verifies the credentials
transition at the next non-credential-setting system call (we just
mention this possibility for completeness, but are certainly not
endorsing it).

We chose the simpler approach of a new system call, as we don't expect
the set of credentials one can set to change often. It has the
advantages that the traditional system calls' code doesn't have to be
changed and that we can establish a special MAC protocol for it, by
having some cleanup function called just before returning (this is
a requirement for MAC/do), without disturbing the existing ones.

The mac_cred_check_setcred() hook is passed the flags received by
setcred() (including the version) and both the old and new kernel's
'struct ucred' instead of 'struct setcred' as this should simplify
evolving existing hooks as the 'struct setcred' structure evolves. The
mac_cred_setcred_enter() and mac_cred_setcred_exit() hooks are always
called by pairs around potential calls to mac_cred_check_setcred().
They allow MAC modules to allocate/free data they may need in their
mac_cred_check_setcred() hook, as the latter is called under the current
process' lock, rendering sleepable allocations impossible. MAC/do is
going to leverage these in a subsequent commit. A scheme where
mac_cred_check_setcred() could return ERESTART was considered but is
incompatible with proper composition of MAC modules.

While here, add missing includes and declarations for standalone
inclusion of <sys/ucred.h> both from kernel and userspace (for the
latter, it has been working thanks to <bsm/audit.h> already including
<sys/types.h>).

Reviewed by: brooks
Approved by: markj (mentor)
Relnotes: yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D47618

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Regen

sysent: regen for typo fix

sysent: regen comments

Regen

syscalls.master: correct return type of {read,write}v

This was missed when read/write, etc were updated to return ssize_t.

Fixes: 2e83b2816183 Fix a few syscall arguments to use size_t instead of

syscalls.master: correct return type of {read,write}v

This was missed when read/write, etc were updated to return ssize_t.

Fixes: 2e83b2816183 Fix a few syscall arguments to use size_t instead of u_int.

Reviewed by: imp, kib
Differential Revision: https://reviews.freebsd.org/D44930

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sysent: regen

regen

Remove never implemented sbrk and sstk syscalls

Both system calls were stubs returning EOPNOTSUPP and libc did not
provide _ or __sys_ prefixed symbols. The actual implementation of
sbrk(2) is on t

Remove never implemented sbrk and sstk syscalls

Both system calls were stubs returning EOPNOTSUPP and libc did not
provide _ or __sys_ prefixed symbols. The actual implementation of
sbrk(2) is on top of the undocumented break(2) system call.

Technically this is a change in ABI, but no non-contrived program ever
called these syscalls.

Reviewed by: kib, emaste
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D42872

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timerfd: Move implementation from linux compat to sys/kern

Move the timerfd impelemntation from linux compat code to sys/kern. Use
it to implement the new system calls for timerfd. Add a hook to ker

timerfd: Move implementation from linux compat to sys/kern

Move the timerfd impelemntation from linux compat code to sys/kern. Use
it to implement the new system calls for timerfd. Add a hook to kern_tc
to allow timerfd to know when the system time has stepped. Add kqueue
support to timerfd. Adjust a few names to be less Linux centric.

RelNotes: YES
Reviewed by: markj (on irc), imp, kib (with reservations), jhb (slack)
Differential Revision: https://reviews.freebsd.org/D38459

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Regen

Regenerate sysent stuff after $FreeBSD$ removal

Sponsored by: Netflix

Regen

Regen

Regen

syscalls: regen

syscalls: regen

syscalls: regen

syscalls: regen

syscalls: regen

syscalls: regen

syscalls: regen

syscalls: regen

syscalls: use struct siginfo rather than siginfo_t

This allows freebsd32 to use struct siginfo32 with an automatable
conversion.

Reviewed by: kevans

syscalls: use __socklen_t as appropriate

No functional change as __socklen_t is an int.

Obtained from: CheriBSD

Reviewed by: kevans