Re: capsicum(4): .. and SIGTRAP causing syscall really is in siginfo_t.si_errno?

From: Steffen Nurpmeso <>
Date: Fri, 14 Apr 2023 23:57:08 UTC
P.S.: as an addendum.

Steffen Nurpmeso wrote in
 |Ed Maste wrote in
 | <>:
 ||On Wed, 12 Apr 2023 at 16:34, Steffen Nurpmeso <> wrote:
 ||Indeed. These limitations all stem from the properties that give
 ||Capsicum its security properties (no access to global namespaces or
 ||ambient authority). It is "relatively" straightforward to use when
 ||incorporated into new software from the beginning, but certainly
 ||harder to retrofit.
 ||realpath is an interesting case, as in capability mode there is no
 ||absolute root directory. All paths are necessarily relative to a
 ||directory fd. The Casper fileargs service provides a realpath
 ||replacement, but I've also started looking into what a Capsicum-native
 ||realpathat would be.

I changed the program in that, on FreeBSD, configuration reload
after SIGHUP is only performed in --untamed mode (no OS sandbox,
only generic setrlimit(2)).

Like this i can tighten the capsicum(4) sandbox in that (instead)
only a descriptor to our --store-path is open, an actual "chroot"
thus (we chdir(2) to that on startup).  'Allowed to get rid of all
realpath(3) etc (of course), all special path treatment is gone.

P.P.S.: i learned quite a bit the last weeks.  postfix for example
does not use anything such (except a bit setrlimit), but i trust
it.  I do not know.  I think next time i have to bite the bullet
and design it with such a supercapable process from the start.
Ah, is all that expensive!  Compared to strict manager / worker
thread scheme with almost no shared data, thread-specific memory
etc etc.  I was really wondering how the usage of TLS aka OpenSSL
fits this, if workers are capsicum(4)ized; they need to access CA
files / directories, and, hm, private keys.  I saw ressl commit
messages fly by with "in-memory-images", years ago, but i never
really looked.
That is the thing that i wonder of, all the libraries that i have
to use, how does this fit such a security scheme.  All black
boxes, all/most evolving targets that can change at any time.

Ciao, and a nice weekend i wish!
And thanks again.

|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)