windows: add GetExplicitEntriesFromAcl

Author: yjhmelody

windows/security_windows.go

@@ -1122,6 +1122,7 @@ type OBJECTS_AND_NAME struct {
 //sys	SetSecurityInfo(handle Handle, objectType SE_OBJECT_TYPE, securityInformation SECURITY_INFORMATION, owner *SID, group *SID, dacl *ACL, sacl *ACL) = advapi32.SetSecurityInfo
 //sys	getNamedSecurityInfo(objectName string, objectType SE_OBJECT_TYPE, securityInformation SECURITY_INFORMATION, owner **SID, group **SID, dacl **ACL, sacl **ACL, sd **SECURITY_DESCRIPTOR) (ret error) = advapi32.GetNamedSecurityInfoW
 //sys	SetNamedSecurityInfo(objectName string, objectType SE_OBJECT_TYPE, securityInformation SECURITY_INFORMATION, owner *SID, group *SID, dacl *ACL, sacl *ACL) (ret error) = advapi32.SetNamedSecurityInfoW
+//sys	getExplicitEntriesFromAclW(acl *ACL, countAccessEntries *uint32, accessEntries **EXPLICIT_ACCESS) (ret error) = advapi32.GetExplicitEntriesFromAclW
 
 //sys	buildSecurityDescriptor(owner *TRUSTEE, group *TRUSTEE, countAccessEntries uint32, accessEntries *EXPLICIT_ACCESS, countAuditEntries uint32, auditEntries *EXPLICIT_ACCESS, oldSecurityDescriptor *SECURITY_DESCRIPTOR, sizeNewSecurityDescriptor *uint32, newSecurityDescriptor **SECURITY_DESCRIPTOR) (ret error) = advapi32.BuildSecurityDescriptorW
 //sys	initializeSecurityDescriptor(absoluteSD *SECURITY_DESCRIPTOR, revision uint32) (err error) = advapi32.InitializeSecurityDescriptor
@@ -1374,6 +1375,29 @@ func GetNamedSecurityInfo(objectName string, objectType SE_OBJECT_TYPE, security
 	return winHeapSD.copySelfRelativeSecurityDescriptor(), nil
 }
 
+// GetExplicitEntriesFromAcl queries the explicit entries from a given ACL
+func GetExplicitEntriesFromAcl(acl *ACL) ([]EXPLICIT_ACCESS, error) {
+	var entries *EXPLICIT_ACCESS
+	var size uint32
+	err := getExplicitEntriesFromAclW(
+		acl,
+		&size,
+		&entries,
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	defer LocalFree(Handle(unsafe.Pointer(entries)))
+	var accesses []EXPLICIT_ACCESS
+	for i := 0; i < int(size); i++ {
+		accesses = append(accesses, *entries)
+		entries = (*EXPLICIT_ACCESS)(unsafe.Pointer((uintptr(unsafe.Pointer(entries)) + unsafe.Sizeof(*entries))))
+	}
+
+	return accesses, nil
+}
+
 // BuildSecurityDescriptor makes a new security descriptor using the input trustees, explicit access lists, and
 // prior security descriptor to be merged, any of which can be nil, returning the self-relative security descriptor
 // result on the Go heap.

windows/syscall_windows_test.go

@@ -18,6 +18,50 @@ import (
 	"golang.org/x/sys/windows"
 )
 
+func TestGetExplicitEntriesFromAcl(t *testing.T) {
+	fileObject := os.ExpandEnv("${SystemRoot}")
+
+	sd, err := windows.GetNamedSecurityInfo(
+		fileObject,
+		windows.SE_FILE_OBJECT,
+		windows.DACL_SECURITY_INFORMATION,
+	)
+
+	dacl, _, err := sd.DACL()
+	if err != nil {
+		t.Fatal(err)
+	}
+	accesses, err := windows.GetExplicitEntriesFromAcl(dacl)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, access := range accesses {
+		_ = trusteeValueFrom(&access.Trustee)
+	}
+}
+
+func trusteeValueFrom(trustee *windows.TRUSTEE) interface{} {
+	var ret interface{}
+	switch trustee.TrusteeForm {
+	case windows.TRUSTEE_IS_SID:
+		ret = windows.TrusteeValueToSID(trustee.TrusteeValue).String()
+
+	case windows.TRUSTEE_IS_NAME:
+		ret = windows.TrusteeValueToString(trustee.TrusteeValue)
+
+	case windows.TRUSTEE_BAD_FORM:
+
+	case windows.TRUSTEE_IS_OBJECTS_AND_SID:
+		ret = windows.TrusteeValueToObjectsAndSid(trustee.TrusteeValue)
+
+	case windows.TRUSTEE_IS_OBJECTS_AND_NAME:
+		ret = windows.TrusteeValueToObjectsAndName(trustee.TrusteeValue)
+	}
+
+	return ret
+}
+
 func TestWin32finddata(t *testing.T) {
 	dir, err := ioutil.TempDir("", "go-build")
 	if err != nil {