dump: Extract tar code to internal/dump

internal/dump/acl.go

@@ -0,0 +1,120 @@
+package dump
+
+// Adapted from https://github.com/maxymania/go-system/blob/master/posix_acl/posix_acl.go
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+)
+
+const (
+	aclUserOwner  = 0x0001
+	aclUser       = 0x0002
+	aclGroupOwner = 0x0004
+	aclGroup      = 0x0008
+	aclMask       = 0x0010
+	aclOthers     = 0x0020
+)
+
+type aclSID uint64
+
+type aclElem struct {
+	Tag  uint16
+	Perm uint16
+	ID   uint32
+}
+
+type acl struct {
+	Version uint32
+	List    []aclElement
+}
+
+type aclElement struct {
+	aclSID
+	Perm uint16
+}
+
+func (a aclSID) getType() int {
+	return int(a >> 32)
+}
+func (a aclSID) getID() uint32 {
+	return uint32(a & 0xffffffff)
+}
+func (a aclSID) String() string {
+	switch a >> 32 {
+	case aclUserOwner:
+		return "user::"
+	case aclUser:
+		return fmt.Sprintf("user:%v:", a.getID())
+	case aclGroupOwner:
+		return "group::"
+	case aclGroup:
+		return fmt.Sprintf("group:%v:", a.getID())
+	case aclMask:
+		return "mask::"
+	case aclOthers:
+		return "other::"
+	}
+	return "?:"
+}
+
+func (a aclElement) String() string {
+	str := ""
+	if (a.Perm & 4) != 0 {
+		str += "r"
+	} else {
+		str += "-"
+	}
+	if (a.Perm & 2) != 0 {
+		str += "w"
+	} else {
+		str += "-"
+	}
+	if (a.Perm & 1) != 0 {
+		str += "x"
+	} else {
+		str += "-"
+	}
+	return fmt.Sprintf("%v%v", a.aclSID, str)
+}
+
+func (a *acl) decode(xattr []byte) {
+	var elem aclElement
+	ae := new(aclElem)
+	nr := bytes.NewReader(xattr)
+	e := binary.Read(nr, binary.LittleEndian, &a.Version)
+	if e != nil {
+		a.Version = 0
+		return
+	}
+	if len(a.List) > 0 {
+		a.List = a.List[:0]
+	}
+	for binary.Read(nr, binary.LittleEndian, ae) == nil {
+		elem.aclSID = (aclSID(ae.Tag) << 32) | aclSID(ae.ID)
+		elem.Perm = ae.Perm
+		a.List = append(a.List, elem)
+	}
+}
+
+func (a *acl) encode() []byte {
+	buf := new(bytes.Buffer)
+	ae := new(aclElem)
+	binary.Write(buf, binary.LittleEndian, &a.Version)
+	for _, elem := range a.List {
+		ae.Tag = uint16(elem.getType())
+		ae.Perm = elem.Perm
+		ae.ID = elem.getID()
+		binary.Write(buf, binary.LittleEndian, ae)
+	}
+	return buf.Bytes()
+}
+
+func (a *acl) String() string {
+	var finalacl string
+	for _, acl := range a.List {
+		finalacl += acl.String() + "\n"
+	}
+	return finalacl
+}