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seccomp.sh: Handle missing ausyscall(8) or unknown syscall number

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...try sourcing it with the compiler from <sys/syscalls.h> before
giving up.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
Stefano Brivio 2021-10-21 01:21:26 +02:00
parent 849308d207
commit 819d13bb92
1 changed files with 26 additions and 3 deletions
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29
seccomp.sh
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@ -8,7 +8,7 @@
# PASTA - Pack A Subtle Tap Abstraction
# for network namespace/tap device mode
#
# seccomp.sh - Build seccomp profiles from "#syscalls[:PROFILE]" comments in code
# seccomp.sh - Build seccomp profiles from "#syscalls[:PROFILE]" code comments
#
# Copyright (c) 2021 Red Hat GmbH
# Author: Stefano Brivio <sbrivio@redhat.com>
@ -41,8 +41,15 @@ CALL=' BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, @NR@, @ALLOW@, 0), /* @NAME@ */'
# Binary search tree node or leaf, @NR@: value, @R@: right jump, @L@: left jump
BST=' BPF_JUMP(BPF_JMP | BPF_JGE | BPF_K, @NR@, @R@, @L@),'
# cleanup() - Remove temporary file if it exists
cleanup() {
rm -f "${TMP}"
}
trap "cleanup" EXIT
# sub() - Substitute in-place file line with processed template line
# $1: Line number
# $2: Template name (variable name)
# $@: Replacement for @KEY@ in the form KEY:value
sub() {
IFS=
@ -90,6 +97,15 @@ log2() {
echo ${__x}
}
# cc_syscall_nr - Try to get syscall number from compiler
# $1: Name of syscall
cc_syscall_nr() {
__in="$(printf "#include <sys/syscall.h>\n__NR_%s" ${1})"
__out="$(echo "${__in}" | cc -E -xc - -o - | tail -1)"
[ "${__out}" = "__NR_$1" ] && return 1
echo "${__out}"
}
# gen_profile() - Build struct sock_filter for a single profile
# $1: Profile name
# $@: Names of allowed system calls, amount padded to next power of two
@ -106,7 +122,14 @@ gen_profile() {
echo -1 >> "${TMP}"
done
for __i in $(seq 1 ${__statements_calls} ); do
ausyscall $(eval echo \${${__i}}) --exact >> "${TMP}"
__syscall_name="$(eval echo \${${__i}})"
if { ! command -V ausyscall >/dev/null 2>&1 || \
! ausyscall "${__syscall_name}" --exact >> "${TMP}"; } && \
! cc_syscall_nr "${__syscall_name}" >> "${TMP}"; then
echo "Cannot get syscall number for ${__syscall_name}"
exit 1
fi
eval __syscall_nr_$(tail -1 "${TMP}")="${__syscall_name}"
done
sort -go "${TMP}" "${TMP}"
@ -153,7 +176,7 @@ gen_profile() {
# Calls
for __i in $(seq $(( __statements_bst + 1 )) ${__statements}); do
__nr="$(sed -n ${__i}p "${TMP}")"
__name=$(ausyscall ${__nr})
eval __name="\${__syscall_nr_${__nr}}"
__allow=$(( __statements - __i + 1 ))
sub ${__i} CALL "NR:${__nr}" "NAME:${__name}" "ALLOW:${__allow}"
done