From dcd532e2e416aa81ca9ac42dc153731855f91418 Mon Sep 17 00:00:00 2001 From: Ian Lewis Date: Tue, 15 Sep 2020 23:17:36 -0700 Subject: Add support for OCI seccomp filters in the sandbox. OCI configuration includes support for specifying seccomp filters. In runc, these filter configurations are converted into seccomp BPF programs and loaded into the kernel via libseccomp. runsc needs to be a static binary so, for runsc, we cannot rely on a C library and need to implement the functionality in Go. The generator added here implements basic support for taking OCI seccomp configuration and converting it into a seccomp BPF program with the same behavior as a program generated by libseccomp. - New conditional operations were added to pkg/seccomp to support operations available in OCI. - AllowAny and AllowValue were renamed to MatchAny and EqualTo to better reflect that syscalls matching the conditionals result in the provided action not simply SCMP_RET_ALLOW. - BuildProgram in pkg/seccomp no longer panics if provided an empty list of rules. It now builds a program with the architecture sanity check only. - ProgramBuilder now allows adding labels that are unused. However, backwards jumps are still not permitted. Fixes #510 PiperOrigin-RevId: 331938697 --- pkg/abi/linux/seccomp.go | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) (limited to 'pkg/abi') diff --git a/pkg/abi/linux/seccomp.go b/pkg/abi/linux/seccomp.go index d0607e256..b07cafe12 100644 --- a/pkg/abi/linux/seccomp.go +++ b/pkg/abi/linux/seccomp.go @@ -34,11 +34,11 @@ type BPFAction uint32 const ( SECCOMP_RET_KILL_PROCESS BPFAction = 0x80000000 - SECCOMP_RET_KILL_THREAD = 0x00000000 - SECCOMP_RET_TRAP = 0x00030000 - SECCOMP_RET_ERRNO = 0x00050000 - SECCOMP_RET_TRACE = 0x7ff00000 - SECCOMP_RET_ALLOW = 0x7fff0000 + SECCOMP_RET_KILL_THREAD BPFAction = 0x00000000 + SECCOMP_RET_TRAP BPFAction = 0x00030000 + SECCOMP_RET_ERRNO BPFAction = 0x00050000 + SECCOMP_RET_TRACE BPFAction = 0x7ff00000 + SECCOMP_RET_ALLOW BPFAction = 0x7fff0000 ) func (a BPFAction) String() string { @@ -64,6 +64,19 @@ func (a BPFAction) Data() uint16 { return uint16(a & SECCOMP_RET_DATA) } +// WithReturnCode sets the lower 16 bits of the SECCOMP_RET_ERRNO or +// SECCOMP_RET_TRACE actions to the provided return code, overwriting the previous +// action, and returns a new BPFAction. If not SECCOMP_RET_ERRNO or +// SECCOMP_RET_TRACE then this panics. +func (a BPFAction) WithReturnCode(code uint16) BPFAction { + // mask out the previous return value + baseAction := a & SECCOMP_RET_ACTION_FULL + if baseAction == SECCOMP_RET_ERRNO || baseAction == SECCOMP_RET_TRACE { + return BPFAction(uint32(baseAction) | uint32(code)) + } + panic("WithReturnCode only valid for SECCOMP_RET_ERRNO and SECCOMP_RET_TRACE") +} + // SockFprog is sock_fprog taken from . type SockFprog struct { Len uint16 -- cgit v1.2.3