tightens seccomp filter: allow only openat(O_RDONLY)

be more strict and allow an openat only with the O_RDONLY flag. This is kind of redundant with landlock, but still good to have. Landlock is not yet widely available and won't kill the process upon policy violation; furthermore, landlock can be disabled at boot time. tested on GNU and musl libc on arch and alpine amd64.
2022-02-13 16:20:27 +00:00 · 2022-02-13 16:20:27 +00:00 · 4f0e893cd3
parent 94c5f99ab0
commit 4f0e893cd3
1 changed files with 1 additions and 1 deletions
--- a/sandbox.c
+++ b/sandbox.c
@ -354,7 +354,7 @@ static struct sock_filter filter[] = {
 	SC_ALLOW(oldfstat),
 #endif
 #ifdef __NR_openat
-	SC_ALLOW(openat),
+	SC_ALLOW_ARG(__NR_openat, 3, O_RDONLY),
 #endif
 #ifdef __NR_prlimit64
 	SC_ALLOW(prlimit64),