FAB-14491 Bootstrap externalbuilders

This CR creates an externalbuilders package for chaincode, and adds one
simple method for checking if a path is a child, or potentially escapes
via relative or absolute path tricks.

Change-Id: I7db7ee22450b8417b838c0030bf6885469b7dadc
Signed-off-by: Jason Yellick <jyellick@us.ibm.com>

Author: Jason Yellick

core/container/externalbuilders/externalbuilders_suite_test.go

@@ -0,0 +1,19 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package externalbuilders_test
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+func TestExternalbuilders(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Externalbuilders Suite")
+}

core/container/externalbuilders/tar.go

@@ -0,0 +1,30 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package externalbuilders
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+// ValidPath checks to see if the path is absolute, or if it is a
+// relative path higher in the tree.  In these cases it returns false.
+func ValidPath(uncleanPath string) bool {
+	// sanitizedPath will eliminate non-prefix instances of '..', as well
+	// as strip './'
+	sanitizedPath := filepath.Clean(uncleanPath)
+
+	switch {
+	case filepath.IsAbs(sanitizedPath):
+		return false
+	case strings.HasPrefix(sanitizedPath, ".."):
+		return false
+	default:
+		// Path appears to be relative without escaping higher
+		return true
+	}
+}

core/container/externalbuilders/tar_test.go

@@ -0,0 +1,29 @@
+/*
+Copyright IBM Corp. All Rights Reserved.
+
+SPDX-License-Identifier: Apache-2.0
+*/
+
+package externalbuilders_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/hyperledger/fabric/core/container/externalbuilders"
+)
+
+var _ = Describe("Tar", func() {
+	Describe("ValidPath()", func() {
+		It("validates that a path is relative and a child", func() {
+			Expect(externalbuilders.ValidPath("a/simple/path")).To(BeTrue())
+			Expect(externalbuilders.ValidPath("../path/to/parent")).To(BeFalse())
+			Expect(externalbuilders.ValidPath("a/path/../with/intermediates")).To(BeTrue())
+			Expect(externalbuilders.ValidPath("a/path/../../../with/toomanyintermediates")).To(BeFalse())
+			Expect(externalbuilders.ValidPath("a/path/with/trailing/../..")).To(BeTrue())
+			Expect(externalbuilders.ValidPath("a/path/with/toomanytrailing/../../../../..")).To(BeFalse())
+			Expect(externalbuilders.ValidPath("/an/absolute/path")).To(BeFalse())
+		})
+	})
+
+})