1 files changed, 82 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/sys_seccomp.go b/pkg/sentry/syscalls/linux/sys_seccomp.go
new file mode 100644
index 000000000..4323a4df4
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_seccomp.go
@@ -0,0 +1,82 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package linux
+
+import (
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/bpf"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// userSockFprog is equivalent to Linux's struct sock_fprog on amd64.
+type userSockFprog struct {
+	// Len is the length of the filter in BPF instructions.
+	Len uint16
+
+	_ [6]byte // padding for alignment
+
+	// Filter is a user pointer to the struct sock_filter array that makes up
+	// the filter program. Filter is a uint64 rather than a usermem.Addr
+	// because usermem.Addr is actually uintptr, which is not a fixed-size
+	// type, and encoding/binary.Read objects to this.
+	Filter uint64
+}
+
+// seccomp applies a seccomp policy to the current task.
+func seccomp(t *kernel.Task, mode, flags uint64, addr usermem.Addr) error {
+	// We only support SECCOMP_SET_MODE_FILTER at the moment.
+	if mode != linux.SECCOMP_SET_MODE_FILTER {
+		// Unsupported mode.
+		return syscall.EINVAL
+	}
+
+	tsync := flags&linux.SECCOMP_FILTER_FLAG_TSYNC != 0
+
+	// The only flag we support now is SECCOMP_FILTER_FLAG_TSYNC.
+	if flags&^linux.SECCOMP_FILTER_FLAG_TSYNC != 0 {
+		// Unsupported flag.
+		return syscall.EINVAL
+	}
+
+	var fprog userSockFprog
+	if _, err := t.CopyIn(addr, &fprog); err != nil {
+		return err
+	}
+	filter := make([]linux.BPFInstruction, int(fprog.Len))
+	if _, err := t.CopyIn(usermem.Addr(fprog.Filter), &filter); err != nil {
+		return err
+	}
+	compiledFilter, err := bpf.Compile(filter)
+	if err != nil {
+		t.Debugf("Invalid seccomp-bpf filter: %v", err)
+		return syscall.EINVAL
+	}
+
+	err = t.AppendSyscallFilter(compiledFilter)
+	if err == nil && tsync {
+		// Now we must copy this seccomp program to all other threads.
+		err = t.SyncSyscallFiltersToThreadGroup()
+	}
+	return err
+}
+
+// Seccomp implements linux syscall seccomp(2).
+func Seccomp(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	return 0, nil, seccomp(t, args[0].Uint64(), args[1].Uint64(), args[2].Pointer())
+}