container: move capset implementation

Signed-off-by: Ophestra <cat@gensokyo.uk>

1 files changed, 45 insertions, 0 deletions

diff --git a/container/capability.go b/container/capability.go
new file mode 100644
index 00000000..7c36ce9e
--- /dev/null
+++ b/container/capability.go
@@ -0,0 +1,45 @@
+package container
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+const (
+	_LINUX_CAPABILITY_VERSION_3 = 0x20080522
+
+	PR_CAP_AMBIENT           = 0x2f
+	PR_CAP_AMBIENT_RAISE     = 0x2
+	PR_CAP_AMBIENT_CLEAR_ALL = 0x4
+
+	CAP_SYS_ADMIN = 0x15
+	CAP_SETPCAP   = 0x8
+)
+
+type (
+	capHeader struct {
+		version uint32
+		pid     int32
+	}
+
+	capData struct {
+		effective   uint32
+		permitted   uint32
+		inheritable uint32
+	}
+)
+
+// See CAP_TO_INDEX in linux/capability.h:
+func capToIndex(cap uintptr) uintptr { return cap >> 5 }
+
+// See CAP_TO_MASK in linux/capability.h:
+func capToMask(cap uintptr) uint32 { return 1 << uint(cap&31) }
+
+func capset(hdrp *capHeader, datap *[2]capData) error {
+	if _, _, errno := syscall.Syscall(syscall.SYS_CAPSET,
+		uintptr(unsafe.Pointer(hdrp)),
+		uintptr(unsafe.Pointer(&datap[0])), 0); errno != 0 {
+		return errno
+	}
+	return nil
+}