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77 lines
2.1 KiB
Perl
Executable file
77 lines
2.1 KiB
Perl
Executable file
#!/usr/bin/perl
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#
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# A simple helper script to help people build seccomp profiles for
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# Docker/LXC. The goal is mostly to reduce the attack surface to the
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# kernel, by restricting access to rarely used, recently added or not used
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# syscalls.
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#
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# This script processes one or more files which contain the list of system
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# calls to be allowed. See mkseccomp.sample for more information how you
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# can configure the list of syscalls. When run, this script produces output
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# which, when stored in a file, can be passed to docker as follows:
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#
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# docker run -lxc-conf="lxc.seccomp=$file" <rest of arguments>
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#
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# The included sample file shows how to cut about a quarter of all syscalls,
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# which affecting most applications.
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#
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# For specific situations it is possible to reduce the list further. By
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# reducing the list to just those syscalls required by a certain application
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# you can make it difficult for unknown/unexpected code to run.
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#
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# Run this script as follows:
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#
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# ./mkseccomp.pl < mkseccomp.sample >syscalls.list
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# or
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# ./mkseccomp.pl mkseccomp.sample >syscalls.list
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#
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# Multiple files can be specified, in which case the lists of syscalls are
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# combined.
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#
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# By Martijn van Oosterhout <kleptog@svana.org> Nov 2013
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# How it works:
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#
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# This program basically spawns two processes to form a chain like:
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#
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# <process data section to prefix __NR_> | cpp | <add header and filter unknown syscalls>
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use strict;
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use warnings;
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if( -t ) {
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print STDERR "Helper script to make seccomp filters for Docker/LXC.\n";
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print STDERR "Usage: mkseccomp.pl < [files...]\n";
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exit 1;
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}
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my $pid = open(my $in, "-|") // die "Couldn't fork1 ($!)\n";
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if($pid == 0) { # Child
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$pid = open(my $out, "|-") // die "Couldn't fork2 ($!)\n";
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if($pid == 0) { # Child, which execs cpp
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exec "cpp" or die "Couldn't exec cpp ($!)\n";
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exit 1;
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}
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# Process the DATA section and output to cpp
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print $out "#include <sys/syscall.h>\n";
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while(<>) {
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if(/^\w/) {
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print $out "__NR_$_";
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}
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}
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close $out;
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exit 0;
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}
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# Print header and then process output from cpp.
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print "1\n";
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print "whitelist\n";
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while(<$in>) {
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print if( /^[0-9]/ );
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}
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