Draft: seccomp syscall and ioctls#1458
Draft: seccomp syscall and ioctls#1458rusty-snake wants to merge 1 commit intobytecodealliance:mainfrom
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sunfishcode
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sunfishcode
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At a first glance, this approach looks good.
| operation: super::types::SeccompOperation, | ||
| flags: Option<SetSecureComputingFilterFlags>, | ||
| args: *mut c::c_void, | ||
| ) -> io::Result<c::c_int> { |
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This function should be unsafe because it effectively dereferences args.
| operation: SeccompOperation, | ||
| flags: Option<SetSecureComputingModeFilterFlags>, | ||
| args: *mut c::c_void, | ||
| ) -> io::Result<()> { |
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This function should also be unsafe.
| Self( | ||
| c::sock_fprog { | ||
| // usize as u16 is lossy. However filter programs with more than BPF_MAXINSNS (4096) | ||
| // will be rejected by the kernel with EINVAL. |
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If the user passes a filter list that's too long, it seems like it's be better to fail than to silently truncate the list. The user may be assuming that if the call succeeds, the entire filter list is installed.
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The kernel will return EINVAL for len > 4096 (~32kB filter code). u16::MAX is 65535 (~500kb filter code). So this is more a theoretical than a practical issue - the filter will get rejected by the kernel. On the other hand edit: This would mean we can not use u16::try_from(length).map_err(|_| EINVAL)? isn't complicated.From. So under the assumption to keep using From we can:
u16::try_from(length).unwrap_or(u16::MAX)u16::try_from(length).unwrap_or(0)(Kernel:if (fprog->len == 0 || fprog->len > BPF_MAXINSNS) return ERR_PTR(-EINVAL);)assert!(filter_lines.len() < u16::MAX as usize)as it should not happen in practice.
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This is an early draft seeking for feedback on the API. The
SecureComputingFilteris based on my own seccomp abstractions https://codeberg.org/crabjail/crablock/src/commit/c6cadc33b0e605bf16b8dc2fc0ba8156c7693567/seccomp/src/bpf.rs#L416 .Closes #1451