Improve package URL support (#754)

* rename npm metadata struct

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* improve os package URLs

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* improve language package URLs

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

* wire up composer pURL method

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

syft/pkg/apk_metadata.go

@@ -3,15 +3,18 @@ package pkg
 import (
 	"sort"
 
-	"github.com/anchore/syft/syft/file"
-
 	"github.com/anchore/packageurl-go"
+	"github.com/anchore/syft/syft/file"
+	"github.com/anchore/syft/syft/linux"
 	"github.com/scylladb/go-set/strset"
 )
 
 const ApkDBGlob = "**/lib/apk/db/installed"
 
-var _ FileOwner = (*ApkMetadata)(nil)
+var (
+	_ FileOwner     = (*ApkMetadata)(nil)
+	_ urlIdentifier = (*ApkMetadata)(nil)
+)
 
 // ApkMetadata represents all captured data for a Alpine DB package entry.
 // See the following sources for more information:
@@ -45,22 +48,22 @@ type ApkFileRecord struct {
 }
 
 // PackageURL returns the PURL for the specific Alpine package (see https://github.com/package-url/purl-spec)
-func (m ApkMetadata) PackageURL() string {
+func (m ApkMetadata) PackageURL(distro *linux.Release) string {
-	pURL := packageurl.NewPackageURL(
+	return packageurl.NewPackageURL(
 		// note: this is currently a candidate and not technically within spec
 		// see https://github.com/package-url/purl-spec#other-candidate-types-to-define
 		"alpine",
 		"",
 		m.Package,
 		m.Version,
-		packageurl.Qualifiers{
+		purlQualifiers(
-			{
+			map[string]string{
-				Key:   "arch",
+				purlArchQualifier: m.Architecture,
-				Value: m.Architecture,
 			},
-		},
+			distro,
-		"")
+		),
-	return pURL.ToString()
+		"",
+	).ToString()
 }
 
 func (m ApkMetadata) OwnedFiles() (result []string) {

syft/pkg/apk_metadata_test.go

@@ -1,6 +1,7 @@
 package pkg
 
 import (
+	"github.com/anchore/syft/syft/linux"
 	"strings"
 	"testing"
 
@@ -11,16 +12,35 @@ import (
 
 func TestApkMetadata_pURL(t *testing.T) {
 	tests := []struct {
+		name     string
 		metadata ApkMetadata
+		distro   linux.Release
 		expected string
 	}{
 		{
+			name: "gocase",
 			metadata: ApkMetadata{
 				Package:      "p",
 				Version:      "v",
 				Architecture: "a",
 			},
-			expected: "pkg:alpine/p@v?arch=a",
+			distro: linux.Release{
+				ID:        "alpine",
+				VersionID: "3.4.6",
+			},
+			expected: "pkg:alpine/p@v?arch=a&distro=alpine-3.4.6",
+		},
+		{
+			name: "missing architecure",
+			metadata: ApkMetadata{
+				Package: "p",
+				Version: "v",
+			},
+			distro: linux.Release{
+				ID:        "alpine",
+				VersionID: "3.4.6",
+			},
+			expected: "pkg:alpine/p@v?distro=alpine-3.4.6",
 		},
 		// verify #351
 		{
@@ -29,7 +49,11 @@ func TestApkMetadata_pURL(t *testing.T) {
 				Version:      "v84",
 				Architecture: "am86",
 			},
-			expected: "pkg:alpine/g++@v84?arch=am86",
+			distro: linux.Release{
+				ID:        "alpine",
+				VersionID: "3.4.6",
+			},
+			expected: "pkg:alpine/g++@v84?arch=am86&distro=alpine-3.4.6",
 		},
 		{
 			metadata: ApkMetadata{
@@ -37,13 +61,17 @@ func TestApkMetadata_pURL(t *testing.T) {
 				Version:      "v84",
 				Architecture: "am86",
 			},
-			expected: "pkg:alpine/g%20plus%20plus@v84?arch=am86",
+			distro: linux.Release{
+				ID:        "alpine",
+				VersionID: "3.15.0",
+			},
+			expected: "pkg:alpine/g%20plus%20plus@v84?arch=am86&distro=alpine-3.15.0",
 		},
 	}
 
 	for _, test := range tests {
-		t.Run(test.expected, func(t *testing.T) {
+		t.Run(test.name, func(t *testing.T) {
-			actual := test.metadata.PackageURL()
+			actual := test.metadata.PackageURL(&test.distro)
 			if actual != test.expected {
 				dmp := diffmatchpatch.New()
 				diffs := dmp.DiffMain(test.expected, actual, true)

syft/pkg/cataloger/catalog.go

@@ -68,7 +68,7 @@ func Catalog(resolver source.FileResolver, release *linux.Release, catalogers ..
 			p.CPEs = cpe.Generate(p)
 
 			// generate PURL (note: this is excluded from package ID, so is safe to mutate)
-			p.PURL = generatePackageURL(p, release)
+			p.PURL = pkg.URL(p, release)
 
 			// create file-to-package relationships for files owned by the package
 			owningRelationships, err := packageFileOwnershipRelationships(p, resolver)

syft/pkg/cataloger/package_url.go

@@ -1,49 +0,0 @@
-package cataloger
-
-import (
-	"regexp"
-	"strings"
-
-	"github.com/anchore/packageurl-go"
-	"github.com/anchore/syft/syft/linux"
-	"github.com/anchore/syft/syft/pkg"
-)
-
-// generatePackageURL returns a package-URL representation of the given package (see https://github.com/package-url/purl-spec)
-func generatePackageURL(p pkg.Package, release *linux.Release) string {
-	// default to pURLs on the metadata
-	if p.Metadata != nil {
-		if i, ok := p.Metadata.(interface{ PackageURL() string }); ok {
-			return i.PackageURL()
-		} else if i, ok := p.Metadata.(interface{ PackageURL(*linux.Release) string }); ok {
-			return i.PackageURL(release)
-		}
-	}
-
-	var purlType = p.Type.PackageURLType()
-	var name = p.Name
-	var namespace = ""
-
-	switch {
-	case purlType == "":
-		// there is no purl type, don't attempt to craft a purl
-		// TODO: should this be a "generic" purl type instead?
-		return ""
-	case p.Type == pkg.GoModulePkg:
-		re := regexp.MustCompile(`(/)[^/]*$`)
-		fields := re.Split(p.Name, -1)
-		namespace = fields[0]
-		name = strings.TrimPrefix(p.Name, namespace+"/")
-	}
-
-	// generate a purl from the package data
-	pURL := packageurl.NewPackageURL(
-		purlType,
-		namespace,
-		name,
-		p.Version,
-		nil,
-		"")
-
-	return pURL.ToString()
-}

syft/pkg/cataloger/package_url_test.go

@@ -1,166 +0,0 @@
-package cataloger
-
-import (
-	"testing"
-
-	"github.com/anchore/syft/syft/linux"
-	"github.com/anchore/syft/syft/pkg"
-	"github.com/sergi/go-diff/diffmatchpatch"
-)
-
-func TestPackageURL(t *testing.T) {
-	tests := []struct {
-		name     string
-		pkg      pkg.Package
-		distro   *linux.Release
-		expected string
-	}{
-		{
-			name: "golang",
-			pkg: pkg.Package{
-				Name:    "github.com/anchore/syft",
-				Version: "v0.1.0",
-				Type:    pkg.GoModulePkg,
-			},
-			expected: "pkg:golang/github.com/anchore/syft@v0.1.0",
-		},
-		{
-			name: "pip with vcs url",
-			pkg: pkg.Package{
-				Name:    "bad-name",
-				Version: "bad-v0.1.0",
-				Type:    pkg.PythonPkg,
-				Metadata: pkg.PythonPackageMetadata{
-					Name:    "name",
-					Version: "v0.1.0",
-					DirectURLOrigin: &pkg.PythonDirectURLOriginInfo{
-						VCS:      "git",
-						URL:      "https://github.com/test/test.git",
-						CommitID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
-					},
-				},
-			},
-			expected: "pkg:pypi/name@v0.1.0?vcs_url=git+https:%2F%2Fgithub.com%2Ftest%2Ftest.git@aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
-		},
-		{
-			name: "pip without vcs url",
-			pkg: pkg.Package{
-				Name:    "bad-name",
-				Version: "bad-v0.1.0",
-				Type:    pkg.PythonPkg,
-				Metadata: pkg.PythonPackageMetadata{
-					Name:    "name",
-					Version: "v0.1.0",
-				},
-			},
-			expected: "pkg:pypi/name@v0.1.0",
-		},
-		{
-			name: "gem",
-			pkg: pkg.Package{
-				Name:    "name",
-				Version: "v0.1.0",
-				Type:    pkg.GemPkg,
-			},
-			expected: "pkg:gem/name@v0.1.0",
-		},
-		{
-			name: "npm",
-			pkg: pkg.Package{
-				Name:    "name",
-				Version: "v0.1.0",
-				Type:    pkg.NpmPkg,
-			},
-			expected: "pkg:npm/name@v0.1.0",
-		},
-		{
-			name: "deb with arch",
-			distro: &linux.Release{
-				ID: "ubuntu",
-			},
-			pkg: pkg.Package{
-				Name:    "bad-name",
-				Version: "bad-v0.1.0",
-				Type:    pkg.DebPkg,
-				Metadata: pkg.DpkgMetadata{
-					Package:      "name",
-					Version:      "v0.1.0",
-					Architecture: "amd64",
-				},
-			},
-			expected: "pkg:deb/ubuntu/name@v0.1.0?arch=amd64",
-		},
-		{
-			name: "deb with epoch",
-			distro: &linux.Release{
-				ID: "centos",
-			},
-			pkg: pkg.Package{
-				Name:    "bad-name",
-				Version: "bad-v0.1.0",
-				Type:    pkg.RpmPkg,
-				Metadata: pkg.RpmdbMetadata{
-					Name:    "name",
-					Version: "0.1.0",
-					Epoch:   intRef(2),
-					Arch:    "amd64",
-					Release: "3",
-				},
-			},
-			expected: "pkg:rpm/centos/name@0.1.0-3?arch=amd64&epoch=2",
-		},
-		{
-			name: "deb with nil epoch",
-			distro: &linux.Release{
-				ID: "centos",
-			},
-			pkg: pkg.Package{
-				Name:    "bad-name",
-				Version: "bad-v0.1.0",
-				Type:    pkg.RpmPkg,
-				Metadata: pkg.RpmdbMetadata{
-					Name:    "name",
-					Version: "0.1.0",
-					Epoch:   nil,
-					Arch:    "amd64",
-					Release: "3",
-				},
-			},
-			expected: "pkg:rpm/centos/name@0.1.0-3?arch=amd64",
-		},
-		{
-			name:   "deb with unknown distro",
-			distro: nil,
-			pkg: pkg.Package{
-				Name:    "name",
-				Version: "v0.1.0",
-				Type:    pkg.DebPkg,
-			},
-			expected: "pkg:deb/name@v0.1.0",
-		},
-		{
-			name: "cargo",
-			pkg: pkg.Package{
-				Name:    "name",
-				Version: "v0.1.0",
-				Type:    pkg.RustPkg,
-			},
-			expected: "pkg:cargo/name@v0.1.0",
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			actual := generatePackageURL(test.pkg, test.distro)
-			if actual != test.expected {
-				dmp := diffmatchpatch.New()
-				diffs := dmp.DiffMain(test.expected, actual, true)
-				t.Errorf("diff: %s", dmp.DiffPrettyText(diffs))
-			}
-		})
-	}
-}
-
-func intRef(i int) *int {
-	return &i
-}

syft/pkg/dpkg_metadata.go

@@ -12,7 +12,10 @@ import (
 
 const DpkgDBGlob = "**/var/lib/dpkg/{status,status.d/**}"
 
-var _ FileOwner = (*DpkgMetadata)(nil)
+var (
+	_ FileOwner     = (*DpkgMetadata)(nil)
+	_ urlIdentifier = (*DpkgMetadata)(nil)
+)
 
 // DpkgMetadata represents all captured data for a Debian package DB entry; available fields are described
 // at http://manpages.ubuntu.com/manpages/xenial/man1/dpkg-query.1.html in the --showformat section.
@@ -36,24 +39,25 @@ type DpkgFileRecord struct {
 
 // PackageURL returns the PURL for the specific Debian package (see https://github.com/package-url/purl-spec)
 func (m DpkgMetadata) PackageURL(distro *linux.Release) string {
-	if distro == nil {
+	var namespace string
-		return ""
+	if distro != nil {
+		namespace = distro.ID
 	}
-	pURL := packageurl.NewPackageURL(
+	return packageurl.NewPackageURL(
 		// TODO: replace with `packageurl.TypeDebian` upon merge of https://github.com/package-url/packageurl-go/pull/21
 		// TODO: or, since we're now using an Anchore fork of this module, we could do this sooner.
 		"deb",
-		distro.ID,
+		namespace,
 		m.Package,
 		m.Version,
-		packageurl.Qualifiers{
+		purlQualifiers(
-			{
+			map[string]string{
-				Key:   "arch",
+				purlArchQualifier: m.Architecture,
-				Value: m.Architecture,
 			},
-		},
+			distro,
-		"")
+		),
-	return pURL.ToString()
+		"",
+	).ToString()
 }
 
 func (m DpkgMetadata) OwnedFiles() (result []string) {

syft/pkg/dpkg_metadata_test.go

@@ -12,25 +12,29 @@ import (
 
 func TestDpkgMetadata_pURL(t *testing.T) {
 	tests := []struct {
-		distro   linux.Release
+		name     string
+		distro   *linux.Release
 		metadata DpkgMetadata
 		expected string
 	}{
 		{
-			distro: linux.Release{
+			name: "go case",
-				ID: "debian",
+			distro: &linux.Release{
+				ID:        "debian",
+				VersionID: "11",
 			},
 			metadata: DpkgMetadata{
-				Package:      "p",
+				Package: "p",
-				Source:       "s",
+				Source:  "s",
-				Version:      "v",
+				Version: "v",
-				Architecture: "a",
 			},
-			expected: "pkg:deb/debian/p@v?arch=a",
+			expected: "pkg:deb/debian/p@v?distro=debian-11",
 		},
 		{
-			distro: linux.Release{
+			name: "with arch info",
-				ID: "ubuntu",
+			distro: &linux.Release{
+				ID:        "ubuntu",
+				VersionID: "16.04",
 			},
 			metadata: DpkgMetadata{
 				Package:      "p",
@@ -38,13 +42,22 @@ func TestDpkgMetadata_pURL(t *testing.T) {
 				Version:      "v",
 				Architecture: "a",
 			},
-			expected: "pkg:deb/ubuntu/p@v?arch=a",
+			expected: "pkg:deb/ubuntu/p@v?arch=a&distro=ubuntu-16.04",
+		},
+		{
+			name: "missing distro",
+			metadata: DpkgMetadata{
+				Package: "p",
+				Source:  "s",
+				Version: "v",
+			},
+			expected: "pkg:deb/p@v",
 		},
 	}
 
 	for _, test := range tests {
-		t.Run(test.expected, func(t *testing.T) {
+		t.Run(test.name, func(t *testing.T) {
-			actual := test.metadata.PackageURL(&test.distro)
+			actual := test.metadata.PackageURL(test.distro)
 			if actual != test.expected {
 				dmp := diffmatchpatch.New()
 				diffs := dmp.DiffMain(test.expected, actual, true)

syft/pkg/java_metadata.go

@@ -3,10 +3,14 @@ package pkg
 import (
 	"strings"
 
+	"github.com/anchore/syft/syft/linux"
+
 	"github.com/anchore/packageurl-go"
 	"github.com/anchore/syft/internal"
 )
 
+var _ urlIdentifier = (*JavaMetadata)(nil)
+
 var JenkinsPluginPomPropertiesGroupIDs = []string{
 	"io.jenkins.plugins",
 	"org.jenkins.plugins",
@@ -69,7 +73,7 @@ type JavaManifest struct {
 }
 
 // PackageURL returns the PURL for the specific Alpine package (see https://github.com/package-url/purl-spec)
-func (m JavaMetadata) PackageURL() string {
+func (m JavaMetadata) PackageURL(_ *linux.Release) string {
 	if m.PomProperties != nil {
 		pURL := packageurl.NewPackageURL(
 			packageurl.TypeMaven,

syft/pkg/java_metadata_test.go

@@ -136,7 +136,7 @@ func TestJavaMetadata_pURL(t *testing.T) {
 
 	for _, test := range tests {
 		t.Run(test.expected, func(t *testing.T) {
-			actual := test.metadata.PackageURL()
+			actual := test.metadata.PackageURL(nil)
 			if actual != test.expected {
 				dmp := diffmatchpatch.New()
 				diffs := dmp.DiffMain(test.expected, actual, true)

syft/pkg/php_composer_json_metadata.go

@@ -4,8 +4,11 @@ import (
 	"strings"
 
 	"github.com/anchore/packageurl-go"
+	"github.com/anchore/syft/syft/linux"
 )
 
+var _ urlIdentifier = (*PhpComposerJSONMetadata)(nil)
+
 // PhpComposerJSONMetadata represents information found from composer v1/v2 "installed.json" files as well as composer.lock files
 type PhpComposerJSONMetadata struct {
 	Name            string                       `json:"name"`
@@ -40,7 +43,7 @@ type PhpComposerAuthors struct {
 	Homepage string `json:"homepage,omitempty"`
 }
 
-func (m PhpComposerJSONMetadata) PackageURL() string {
+func (m PhpComposerJSONMetadata) PackageURL(_ *linux.Release) string {
 	var name, vendor string
 	fields := strings.Split(m.Name, "/")
 	switch len(fields) {

syft/pkg/php_composer_json_metadata_test.go

@@ -20,7 +20,8 @@ func TestPhpComposerJsonMetadata_pURL(t *testing.T) {
 				Version: "1.0.1",
 			},
 			expected: "pkg:composer/ven/name@1.0.1",
-		}, {
+		},
+		{
 			name: "name with slashes (invalid)",
 			metadata: PhpComposerJSONMetadata{
 				Name:    "ven/name/component",
@@ -36,11 +37,23 @@ func TestPhpComposerJsonMetadata_pURL(t *testing.T) {
 			},
 			expected: "pkg:composer/name@1.0.1",
 		},
+		{
+			name: "ignores distro",
+			distro: &linux.Release{
+				ID:        "rhel",
+				VersionID: "8.4",
+			},
+			metadata: PhpComposerJSONMetadata{
+				Name:    "ven/name",
+				Version: "1.0.1",
+			},
+			expected: "pkg:composer/ven/name@1.0.1",
+		},
 	}
 
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {
-			actual := test.metadata.PackageURL()
+			actual := test.metadata.PackageURL(test.distro)
 			if actual != test.expected {
 				dmp := diffmatchpatch.New()
 				diffs := dmp.DiffMain(test.expected, actual, true)

syft/pkg/python_package_metadata.go

@@ -4,11 +4,16 @@ import (
 	"fmt"
 	"sort"
 
+	"github.com/anchore/syft/syft/linux"
+
 	"github.com/anchore/packageurl-go"
 	"github.com/scylladb/go-set/strset"
 )
 
-var _ FileOwner = (*PythonPackageMetadata)(nil)
+var (
+	_ FileOwner     = (*PythonPackageMetadata)(nil)
+	_ urlIdentifier = (*PythonPackageMetadata)(nil)
+)
 
 // PythonFileDigest represents the file metadata for a single file attributed to a python package.
 type PythonFileDigest struct {
@@ -76,7 +81,7 @@ func (m PythonPackageMetadata) OwnedFiles() (result []string) {
 	return result
 }
 
-func (m PythonPackageMetadata) PackageURL() string {
+func (m PythonPackageMetadata) PackageURL(_ *linux.Release) string {
 	// generate a purl from the package data
 	pURL := packageurl.NewPackageURL(
 		packageurl.TypePyPi,
@@ -101,7 +106,7 @@ func (p PythonDirectURLOriginInfo) vcsURLQualifier() packageurl.Qualifiers {
 	if p.VCS != "" {
 		// Taken from https://github.com/package-url/purl-spec/blob/master/PURL-SPECIFICATION.rst#known-qualifiers-keyvalue-pairs
 		// packageurl-go still doesn't support all qualifier names
-		return packageurl.Qualifiers{{Key: "vcs_url", Value: fmt.Sprintf("%s+%s@%s", p.VCS, p.URL, p.CommitID)}}
+		return packageurl.Qualifiers{{Key: purlVCSURL, Value: fmt.Sprintf("%s+%s@%s", p.VCS, p.URL, p.CommitID)}}
 	}
-	return packageurl.Qualifiers{}
+	return nil
 }

syft/pkg/python_package_metadata_test.go

@@ -1,12 +1,60 @@
 package pkg
 
 import (
+	"github.com/anchore/syft/syft/linux"
+	"github.com/sergi/go-diff/diffmatchpatch"
 	"strings"
 	"testing"
 
 	"github.com/go-test/deep"
 )
 
+func TestPythonPackageMetadata_pURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		distro   *linux.Release
+		metadata PythonPackageMetadata
+		expected string
+	}{
+		{
+			name: "with vcs info",
+			metadata: PythonPackageMetadata{
+				Name:    "name",
+				Version: "v0.1.0",
+				DirectURLOrigin: &PythonDirectURLOriginInfo{
+					VCS:      "git",
+					URL:      "https://github.com/test/test.git",
+					CommitID: "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+				},
+			},
+			expected: "pkg:pypi/name@v0.1.0?vcs_url=git+https:%2F%2Fgithub.com%2Ftest%2Ftest.git@aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+		},
+		{
+			name: "should not respond to release info",
+			distro: &linux.Release{
+				ID:        "rhel",
+				VersionID: "8.4",
+			},
+			metadata: PythonPackageMetadata{
+				Name:    "name",
+				Version: "v0.1.0",
+			},
+			expected: "pkg:pypi/name@v0.1.0",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			actual := test.metadata.PackageURL(test.distro)
+			if actual != test.expected {
+				dmp := diffmatchpatch.New()
+				diffs := dmp.DiffMain(test.expected, actual, true)
+				t.Errorf("diff: %s", dmp.DiffPrettyText(diffs))
+			}
+		})
+	}
+}
+
 func TestPythonMetadata_FileOwner(t *testing.T) {
 	tests := []struct {
 		metadata PythonPackageMetadata

syft/pkg/rpmdb_metadata.go

@@ -15,7 +15,10 @@ import (
 
 const RpmDBGlob = "**/var/lib/rpm/Packages"
 
-var _ FileOwner = (*RpmdbMetadata)(nil)
+var (
+	_ FileOwner     = (*RpmdbMetadata)(nil)
+	_ urlIdentifier = (*RpmdbMetadata)(nil)
+)
 
 // RpmdbMetadata represents all captured data for a RPM DB package entry.
 type RpmdbMetadata struct {
@@ -47,36 +50,32 @@ type RpmdbFileMode uint16
 
 // PackageURL returns the PURL for the specific RHEL package (see https://github.com/package-url/purl-spec)
 func (m RpmdbMetadata) PackageURL(distro *linux.Release) string {
-	if distro == nil {
+	var namespace string
-		return ""
+	if distro != nil {
+		namespace = distro.ID
 	}
 
-	qualifiers := packageurl.Qualifiers{
+	qualifiers := map[string]string{
-		{
+		purlArchQualifier: m.Arch,
-			Key:   "arch",
-			Value: m.Arch,
-		},
 	}
 
 	if m.Epoch != nil {
-		qualifiers = append(qualifiers,
+		qualifiers[purlEpochQualifier] = strconv.Itoa(*m.Epoch)
-			packageurl.Qualifier{
-				Key:   "epoch",
-				Value: strconv.Itoa(*m.Epoch),
-			},
-		)
 	}
 
-	pURL := packageurl.NewPackageURL(
+	return packageurl.NewPackageURL(
 		packageurl.TypeRPM,
-		distro.ID,
+		namespace,
 		m.Name,
 		// for purl the epoch is a qualifier, not part of the version
 		// see https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst under the RPM section
 		fmt.Sprintf("%s-%s", m.Version, m.Release),
-		qualifiers,
+		purlQualifiers(
-		"")
+			qualifiers,
-	return pURL.ToString()
+			distro,
+		),
+		"",
+	).ToString()
 }
 
 func (m RpmdbMetadata) OwnedFiles() (result []string) {

syft/pkg/rpmdb_metadata_test.go

@@ -12,13 +12,16 @@ import (
 
 func TestRpmMetadata_pURL(t *testing.T) {
 	tests := []struct {
-		distro   linux.Release
+		name     string
+		distro   *linux.Release
 		metadata RpmdbMetadata
 		expected string
 	}{
 		{
-			distro: linux.Release{
+			name: "with arch and epoch",
-				ID: "centos",
+			distro: &linux.Release{
+				ID:        "centos",
+				VersionID: "7",
 			},
 			metadata: RpmdbMetadata{
 				Name:    "p",
@@ -27,26 +30,37 @@ func TestRpmMetadata_pURL(t *testing.T) {
 				Release: "r",
 				Epoch:   intRef(1),
 			},
-			expected: "pkg:rpm/centos/p@v-r?arch=a&epoch=1",
+			expected: "pkg:rpm/centos/p@v-r?arch=a&epoch=1&distro=centos-7",
 		},
 		{
-			distro: linux.Release{
+			name: "go case",
-				ID: "rhel",
+			distro: &linux.Release{
+				ID:        "rhel",
+				VersionID: "8.4",
 			},
 			metadata: RpmdbMetadata{
 				Name:    "p",
 				Version: "v",
-				Arch:    "a",
 				Release: "r",
 				Epoch:   nil,
 			},
-			expected: "pkg:rpm/rhel/p@v-r?arch=a",
+			expected: "pkg:rpm/rhel/p@v-r?distro=rhel-8.4",
+		},
+		{
+			name: "missing distro",
+			metadata: RpmdbMetadata{
+				Name:    "p",
+				Version: "v",
+				Release: "r",
+				Epoch:   nil,
+			},
+			expected: "pkg:rpm/p@v-r",
 		},
 	}
 
 	for _, test := range tests {
-		t.Run(test.expected, func(t *testing.T) {
+		t.Run(test.name, func(t *testing.T) {
-			actual := test.metadata.PackageURL(&test.distro)
+			actual := test.metadata.PackageURL(test.distro)
 			if actual != test.expected {
 				dmp := diffmatchpatch.New()
 				diffs := dmp.DiffMain(test.expected, actual, true)

syft/pkg/url.go

@@ -0,0 +1,86 @@
+package pkg
+
+import (
+	"fmt"
+	"regexp"
+	"sort"
+	"strings"
+
+	"github.com/anchore/packageurl-go"
+	"github.com/anchore/syft/syft/linux"
+)
+
+const (
+	purlArchQualifier   = "arch"
+	purlDistroQualifier = "distro"
+	purlEpochQualifier  = "epoch"
+	purlVCSURL          = "vcs_url"
+)
+
+type urlIdentifier interface {
+	PackageURL(*linux.Release) string
+}
+
+func URL(p Package, release *linux.Release) string {
+	if p.Metadata != nil {
+		if i, ok := p.Metadata.(urlIdentifier); ok {
+			return i.PackageURL(release)
+		}
+	}
+
+	// the remaining cases are primarily reserved for packages without metadata struct instances
+
+	var purlType = p.Type.PackageURLType()
+	var name = p.Name
+	var namespace = ""
+
+	switch {
+	case purlType == "":
+		// there is no purl type, don't attempt to craft a purl
+		// TODO: should this be a "generic" purl type instead?
+		return ""
+	case p.Type == GoModulePkg:
+		re := regexp.MustCompile(`(/)[^/]*$`)
+		fields := re.Split(p.Name, -1)
+		namespace = fields[0]
+		name = strings.TrimPrefix(p.Name, namespace+"/")
+	}
+
+	// generate a purl from the package data
+	return packageurl.NewPackageURL(
+		purlType,
+		namespace,
+		name,
+		p.Version,
+		nil,
+		"",
+	).ToString()
+}
+
+func purlQualifiers(vars map[string]string, release *linux.Release) (q packageurl.Qualifiers) {
+	keys := make([]string, 0, len(vars))
+	for k := range vars {
+		keys = append(keys, k)
+	}
+	sort.Strings(keys)
+
+	for _, k := range keys {
+		val := vars[k]
+		if val == "" {
+			continue
+		}
+		q = append(q, packageurl.Qualifier{
+			Key:   k,
+			Value: vars[k],
+		})
+	}
+
+	if release != nil && release.ID != "" && release.VersionID != "" {
+		q = append(q, packageurl.Qualifier{
+			Key:   purlDistroQualifier,
+			Value: fmt.Sprintf("%s-%s", release.ID, release.VersionID),
+		})
+	}
+
+	return q
+}

syft/pkg/url_test.go

@@ -0,0 +1,200 @@
+package pkg
+
+import (
+	"testing"
+
+	"github.com/anchore/syft/syft/linux"
+	"github.com/scylladb/go-set/strset"
+	"github.com/sergi/go-diff/diffmatchpatch"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPackageURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		pkg      Package
+		distro   *linux.Release
+		expected string
+	}{
+		{
+			name: "golang",
+			pkg: Package{
+				Name:    "github.com/anchore/syft",
+				Version: "v0.1.0",
+				Type:    GoModulePkg,
+			},
+			expected: "pkg:golang/github.com/anchore/syft@v0.1.0",
+		},
+		{
+			name: "python",
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    PythonPkg,
+				Metadata: PythonPackageMetadata{
+					Name:    "name",
+					Version: "v0.1.0",
+				},
+			},
+			expected: "pkg:pypi/name@v0.1.0",
+		},
+		{
+			name: "gem",
+			pkg: Package{
+				Name:    "name",
+				Version: "v0.1.0",
+				Type:    GemPkg,
+			},
+			expected: "pkg:gem/name@v0.1.0",
+		},
+		{
+			name: "npm",
+			pkg: Package{
+				Name:    "name",
+				Version: "v0.1.0",
+				Type:    NpmPkg,
+			},
+			expected: "pkg:npm/name@v0.1.0",
+		},
+		{
+			name: "deb",
+			distro: &linux.Release{
+				ID:        "ubuntu",
+				VersionID: "20.04",
+			},
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    DebPkg,
+				Metadata: DpkgMetadata{
+					Package:      "name",
+					Version:      "v0.1.0",
+					Architecture: "amd64",
+				},
+			},
+			expected: "pkg:deb/ubuntu/name@v0.1.0?arch=amd64&distro=ubuntu-20.04",
+		},
+		{
+			name: "rpm",
+			distro: &linux.Release{
+				ID:        "centos",
+				VersionID: "7",
+			},
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    RpmPkg,
+				Metadata: RpmdbMetadata{
+					Name:    "name",
+					Version: "0.1.0",
+					Epoch:   intRef(2),
+					Arch:    "amd64",
+					Release: "3",
+				},
+			},
+			expected: "pkg:rpm/centos/name@0.1.0-3?arch=amd64&epoch=2&distro=centos-7",
+		},
+		{
+			name: "cargo",
+			pkg: Package{
+				Name:    "name",
+				Version: "v0.1.0",
+				Type:    RustPkg,
+			},
+			expected: "pkg:cargo/name@v0.1.0",
+		},
+		{
+			name: "apk",
+			distro: &linux.Release{
+				ID:        "alpine",
+				VersionID: "3.4.6",
+			},
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    ApkPkg,
+				Metadata: ApkMetadata{
+					Package:      "name",
+					Version:      "v0.1.0",
+					Architecture: "amd64",
+				},
+			},
+			expected: "pkg:alpine/name@v0.1.0?arch=amd64&distro=alpine-3.4.6",
+		},
+		{
+			name: "php-composer",
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    PhpComposerPkg,
+				Metadata: PhpComposerJSONMetadata{
+					Name:    "vendor/name",
+					Version: "2.0.1",
+				},
+			},
+			expected: "pkg:composer/vendor/name@2.0.1",
+		},
+		{
+			name: "java",
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    JavaPkg,
+				Metadata: JavaMetadata{
+					PomProperties: &PomProperties{
+						Path:       "p",
+						Name:       "n",
+						GroupID:    "g.id",
+						ArtifactID: "a",
+						Version:    "v",
+					},
+				},
+			},
+
+			expected: "pkg:maven/g.id/a@v",
+		},
+		{
+			name: "jenkins-plugin",
+			pkg: Package{
+				Name:    "bad-name",
+				Version: "bad-v0.1.0",
+				Type:    JenkinsPluginPkg,
+				Metadata: JavaMetadata{
+					PomProperties: &PomProperties{
+						Path:       "p",
+						Name:       "n",
+						GroupID:    "g.id",
+						ArtifactID: "a",
+						Version:    "v",
+					},
+				},
+			},
+
+			expected: "pkg:maven/g.id/a@v",
+		},
+	}
+
+	var pkgTypes []string
+	var expectedTypes = strset.New()
+	for _, ty := range AllPkgs {
+		expectedTypes.Add(string(ty))
+	}
+
+	// testing microsoft packages is not valid for purl at this time
+	expectedTypes.Remove(string(KbPkg))
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if test.pkg.Type != "" {
+				pkgTypes = append(pkgTypes, string(test.pkg.Type))
+			}
+			actual := URL(test.pkg, test.distro)
+			if actual != test.expected {
+				dmp := diffmatchpatch.New()
+				diffs := dmp.DiffMain(test.expected, actual, true)
+				t.Errorf("diff: %s", dmp.DiffPrettyText(diffs))
+			}
+		})
+	}
+	assert.ElementsMatch(t, expectedTypes.List(), pkgTypes, "missing one or more package types to test against (maybe a package type was added?)")
+}