feat: add support for encoding to older spec versions

.licenserc.yml

@@ -3,17 +3,18 @@ header:
     spdx-id: Apache-2.0
     copyright-owner: OWASP Foundation
   paths-ignore:
+    - "**/*.md"
+    - "**/go.mod"
+    - "**/go.sum"
+    - "**/testdata/**"
     - ".github/**"
     - ".gitignore"
     - ".gitpod.*"
     - ".golangci.yml"
     - ".goreleaser.yml"
     - ".licenserc.yml"
-    - "**/*.md"
-    - "**/go.mod"
-    - "**/go.sum"
-    - "**/testdata/**"
     - "CODEOWNERS"
     - "LICENSE"
     - "Makefile"
-    - "NOTICE"
+    - "NOTICE"
+    - "cyclonedx_string.go"

Makefile

@@ -10,5 +10,9 @@ clean:
 	go clean
 .PHONY: clean
 
+generate:
+	go generate
+.PHONY: generate
+
 all: clean build test
 .PHONY: all

README.md

@@ -28,15 +28,18 @@ Also, checkout the [`examples`](./example_test.go) to get an idea of how this li
 
 | cyclonedx-go versions | Supported Go versions | Supported CycloneDX spec |
 |:---------------------:|:---------------------:|:------------------------:|
-|    < v0.4.0           |         1.14+         |           1.2            |
-|   == v0.4.0           |         1.14+         |           1.3            |
-|   >= v0.5.0           |         1.15+         |           1.4            |
+|       < v0.4.0        |         1.14+         |           1.2            |
+|       == v0.4.0       |         1.14+         |           1.3            |
+|       >= v0.5.0       |         1.15+         |           1.4            |
+|       >= v0.7.0       |         1.15+         |         1.0-1.4          |
 
 We're aiming to support all [officially supported](https://golang.org/doc/devel/release.html#policy) Go versions, plus
 an additional older version.
 
-This library will only support the latest version of the CycloneDX specification. While it's generally possible to 
-*read* BOMs of an older spec, *writing* will exclusively produce BOMs conforming to the latest supported spec.
+Prior to v0.7.0, this library only supported the latest version of the CycloneDX specification. While it is generally 
+possible to *read* BOMs of an older spec, *writing* would exclusively produce BOMs conforming to the latest supported spec.
+
+Starting with v0.7.0, writing BOMs conforming to all previous version of the spec is also possible.
 
 ## Copyright & License
 

copy.go

@@ -0,0 +1,43 @@
+// This file is part of CycloneDX Go
+//
+// 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.
+//
+// SPDX-License-Identifier: Apache-2.0
+// Copyright (c) OWASP Foundation. All Rights Reserved.
+
+package cyclonedx
+
+import (
+	"bytes"
+	"encoding/gob"
+	"fmt"
+)
+
+// copy creates a deep copy of the BOM in a given destination.
+// Copying is currently done be encoding and decoding the BOM struct using the gop.
+// In the future we may choose to switch to a more efficient strategy,
+// and consider to export this API.
+func (b BOM) copy(dst *BOM) error {
+	buf := bytes.Buffer{}
+	err := gob.NewEncoder(&buf).Encode(b)
+	if err != nil {
+		return fmt.Errorf("failed to encode bom: %w", err)
+	}
+
+	err = gob.NewDecoder(&buf).Decode(dst)
+	if err != nil {
+		return fmt.Errorf("failed to decode bom: %w", err)
+	}
+
+	return nil
+}

cyclonedx.go

@@ -26,11 +26,10 @@ import (
 	"regexp"
 )
 
+//go:generate stringer -linecomment -output cyclonedx_string.go -type SpecVersion
+
 const (
-	BOMFormat      = "CycloneDX"
-	defaultVersion = 1
-	SpecVersion    = "1.4"
-	XMLNamespace   = "http://cyclonedx.org/schema/bom/1.4"
+	BOMFormat = "CycloneDX"
 )
 
 type Advisory struct {
@@ -61,8 +60,8 @@ type BOM struct {
 	XMLNS   string   `json:"-" xml:"xmlns,attr"`
 
 	// JSON specific fields
-	BOMFormat   string `json:"bomFormat" xml:"-"`
-	SpecVersion string `json:"specVersion" xml:"-"`
+	BOMFormat   string      `json:"bomFormat" xml:"-"`
+	SpecVersion SpecVersion `json:"specVersion" xml:"-"`
 
 	SerialNumber       string               `json:"serialNumber,omitempty" xml:"serialNumber,attr,omitempty"`
 	Version            int                  `json:"version" xml:"version,attr"`
@@ -78,10 +77,10 @@ type BOM struct {
 
 func NewBOM() *BOM {
 	return &BOM{
-		XMLNS:       XMLNamespace,
+		XMLNS:       xmlNamespaces[SpecVersion1_4],
 		BOMFormat:   BOMFormat,
-		SpecVersion: SpecVersion,
-		Version:     defaultVersion,
+		SpecVersion: SpecVersion1_4,
+		Version:     1,
 	}
 }
 
@@ -590,6 +589,70 @@ type Source struct {
 	URL  string `json:"url,omitempty" xml:"url,omitempty"`
 }
 
+type SpecVersion int
+
+const (
+	SpecVersion1_0 SpecVersion = iota + 1 // 1.0
+	SpecVersion1_1                        // 1.1
+	SpecVersion1_2                        // 1.2
+	SpecVersion1_3                        // 1.3
+	SpecVersion1_4                        // 1.4
+)
+
+func (sv SpecVersion) MarshalJSON() ([]byte, error) {
+	return json.Marshal(sv.String())
+}
+
+func (sv *SpecVersion) UnmarshalJSON(bytes []byte) error {
+	var v string
+	err := json.Unmarshal(bytes, &v)
+	if err != nil {
+		return err
+	}
+
+	switch v {
+	case SpecVersion1_0.String():
+		*sv = SpecVersion1_0
+	case SpecVersion1_1.String():
+		*sv = SpecVersion1_1
+	case SpecVersion1_2.String():
+		*sv = SpecVersion1_2
+	case SpecVersion1_3.String():
+		*sv = SpecVersion1_3
+	case SpecVersion1_4.String():
+		*sv = SpecVersion1_4
+	}
+
+	return nil
+}
+
+func (sv SpecVersion) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+	return e.EncodeElement(sv.String(), start)
+}
+
+func (sv *SpecVersion) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
+	var v string
+	err := d.DecodeElement(&v, &start)
+	if err != nil {
+		return err
+	}
+
+	switch v {
+	case SpecVersion1_0.String():
+		*sv = SpecVersion1_0
+	case SpecVersion1_1.String():
+		*sv = SpecVersion1_1
+	case SpecVersion1_2.String():
+		*sv = SpecVersion1_2
+	case SpecVersion1_3.String():
+		*sv = SpecVersion1_3
+	case SpecVersion1_4.String():
+		*sv = SpecVersion1_4
+	}
+
+	return nil
+}
+
 type SWID struct {
 	Text       *AttachedText `json:"text,omitempty" xml:"text,omitempty"`
 	URL        string        `json:"url,omitempty" xml:"url,attr,omitempty"`
@@ -657,3 +720,11 @@ const (
 	VulnerabilityStatusAffected    VulnerabilityStatus = "affected"
 	VulnerabilityStatusNotAffected VulnerabilityStatus = "unaffected"
 )
+
+var xmlNamespaces = map[SpecVersion]string{
+	SpecVersion1_0: "http://cyclonedx.org/schema/bom/1.0",
+	SpecVersion1_1: "http://cyclonedx.org/schema/bom/1.1",
+	SpecVersion1_2: "http://cyclonedx.org/schema/bom/1.2",
+	SpecVersion1_3: "http://cyclonedx.org/schema/bom/1.3",
+	SpecVersion1_4: "http://cyclonedx.org/schema/bom/1.4",
+}

cyclonedx_test.go

@@ -20,12 +20,19 @@ package cyclonedx
 import (
 	"encoding/json"
 	"encoding/xml"
+	"fmt"
+	"os/exec"
+	"strings"
 	"testing"
 
+	"github.com/bradleyjkemp/cupaloy/v2"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+var snapShooter = cupaloy.NewDefaultConfig().
+	WithOptions(cupaloy.SnapshotSubdirectory("./testdata/snapshots"))
+
 func TestBool(t *testing.T) {
 	assert.Equal(t, true, *Bool(true))
 	assert.Equal(t, false, *Bool(false))
@@ -228,3 +235,17 @@ func TestVulnerability_Properties(t *testing.T) {
 	// EXPECT
 	assert.Equal(t, 0, len(*vuln.Properties))
 }
+
+func assertValidBOM(t *testing.T, bomFilePath string, version SpecVersion) {
+	inputFormat := "xml"
+	if strings.HasSuffix(bomFilePath, ".json") {
+		inputFormat = "json"
+	}
+	inputVersion := fmt.Sprintf("v%s", strings.ReplaceAll(version.String(), ".", "_"))
+	valCmd := exec.Command("cyclonedx", "validate", "--input-file", bomFilePath, "--input-format", inputFormat, "--input-version", inputVersion, "--fail-on-errors")
+	valOut, err := valCmd.CombinedOutput()
+	if !assert.NoError(t, err) {
+		// Provide some context when test is failing
+		fmt.Printf("validation error: %s\n", string(valOut))
+	}
+}

decode.go

@@ -38,6 +38,7 @@ type jsonBOMDecoder struct {
 	reader io.Reader
 }
 
+// Decode implements the BOMDecoder interface.
 func (j jsonBOMDecoder) Decode(bom *BOM) error {
 	return json.NewDecoder(j.reader).Decode(bom)
 }
@@ -46,6 +47,7 @@ type xmlBOMDecoder struct {
 	reader io.Reader
 }
 
+// Decode implements the BOMDecoder interface.
 func (x xmlBOMDecoder) Decode(bom *BOM) error {
 	return xml.NewDecoder(x.reader).Decode(bom)
 }