feat: support for ipk packages (#818)

Implements #507.

* Adds ipk support for keywords used by OpenWRT and Yocto.
* MD5sum is explicitly excluded due to insecurity.
* SHA256Sum excluded due packages not being individually signed,
  instead, the feed of packages is checksummed and signed externally.
* Adds code to nfpm package to automatically enumerate the supported
  packaging types where possible.

.github/workflows/build.yml

@@ -65,7 +65,7 @@ jobs:
   acceptance-tests:
     strategy:
       matrix:
-        pkgFormat: [deb, rpm, apk, archlinux]
+        pkgFormat: [deb, rpm, apk, archlinux, ipk]
         pkgPlatform: [amd64, arm64, 386, ppc64le, armv6, armv7, s390x]
     runs-on: ubuntu-latest
     env:

acceptance_test.go

@@ -15,6 +15,7 @@ import (
 	_ "github.com/goreleaser/nfpm/v2/apk"
 	_ "github.com/goreleaser/nfpm/v2/arch"
 	_ "github.com/goreleaser/nfpm/v2/deb"
+	_ "github.com/goreleaser/nfpm/v2/ipk"
 	_ "github.com/goreleaser/nfpm/v2/rpm"
 	"github.com/stretchr/testify/require"
 )
@@ -23,6 +24,7 @@ import (
 var formatArchs = map[string][]string{
 	"apk":       {"amd64", "arm64", "386", "ppc64le", "armv6", "armv7", "s390x"},
 	"deb":       {"amd64", "arm64", "ppc64le", "armv7", "s390x"},
+	"ipk":       {"x86_64", "aarch64_generic"},
 	"rpm":       {"amd64", "arm64", "ppc64le"},
 	"archlinux": {"amd64"},
 }
@@ -261,6 +263,38 @@ func TestDebSpecific(t *testing.T) {
 	}
 }
 
+func TestIPKSpecific(t *testing.T) {
+	t.Parallel()
+	format := "ipk"
+	testNames := []string{
+		"alternatives",
+		"conflicts",
+		"predepends",
+	}
+	for _, name := range testNames {
+		for _, arch := range formatArchs[format] {
+			func(t *testing.T, testName, testArch string) {
+				t.Run(fmt.Sprintf("%s/%s/%s", format, testArch, testName), func(t *testing.T) {
+					t.Parallel()
+					if testArch == "ppc64le" && os.Getenv("NO_TEST_PPC64LE") == "true" {
+						t.Skip("ppc64le arch not supported in pipeline")
+					}
+					accept(t, acceptParms{
+						Name:   fmt.Sprintf("%s_%s", testName, testArch),
+						Conf:   fmt.Sprintf("%s.%s.yaml", format, testName),
+						Format: format,
+						Docker: dockerParams{
+							File:   fmt.Sprintf("%s.dockerfile", format),
+							Target: testName,
+							Arch:   testArch,
+						},
+					})
+				})
+			}(t, name, arch)
+		}
+	}
+}
+
 func TestRPMSign(t *testing.T) {
 	t.Parallel()
 	for _, os := range []string{"centos9", "centos8", "fedora34", "fedora36", "fedora38"} {

cmd/nfpm/main.go

@@ -33,7 +33,7 @@ func main() {
 
 func buildVersion(version, commit, date, builtBy, treeState string) goversion.Info {
 	return goversion.GetVersionInfo(
-		goversion.WithAppDetails("nfpm", "a simple and 0-dependencies deb, rpm, apk and arch linux packager written in Go", website),
+		goversion.WithAppDetails("nfpm", "a simple and 0-dependencies apk, arch linux, deb, ipk, and rpm packager written in Go", website),
 		goversion.WithASCIIName(asciiArt),
 		func(i *goversion.Info) {
 			if commit != "" {

internal/cmd/package.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"strings"
 
 	"github.com/goreleaser/nfpm/v2"
 	"github.com/spf13/cobra"
@@ -37,9 +38,12 @@ func newPackageCmd() *packageCmd {
 	_ = cmd.MarkFlagFilename("config", "yaml", "yml")
 	cmd.Flags().StringVarP(&root.target, "target", "t", "", "where to save the generated package (filename, folder or empty for current folder)")
 	_ = cmd.MarkFlagFilename("target")
-	cmd.Flags().StringVarP(&root.packager, "packager", "p", "", "which packager implementation to use [apk|deb|rpm|archlinux]")
-	_ = cmd.RegisterFlagCompletionFunc("packager", cobra.FixedCompletions(
-		[]string{"apk", "deb", "rpm", "archlinux"},
+
+	pkgs := nfpm.Enumerate()
+
+	cmd.Flags().StringVarP(&root.packager, "packager", "p", "",
+		fmt.Sprintf("which packager implementation to use [%s]", strings.Join(pkgs, "|")))
+	_ = cmd.RegisterFlagCompletionFunc("packager", cobra.FixedCompletions(pkgs,
 		cobra.ShellCompDirectiveNoFileComp,
 	))
 

internal/cmd/root.go

@@ -7,6 +7,7 @@ import (
 	_ "github.com/goreleaser/nfpm/v2/apk"  // apk packager
 	_ "github.com/goreleaser/nfpm/v2/arch" // archlinux packager
 	_ "github.com/goreleaser/nfpm/v2/deb"  // deb packager
+	_ "github.com/goreleaser/nfpm/v2/ipk"  // ipk packager
 	_ "github.com/goreleaser/nfpm/v2/rpm"  // rpm packager
 	"github.com/spf13/cobra"
 )
@@ -35,8 +36,8 @@ func newRootCmd(version goversion.Info, exit func(int)) *rootCmd {
 	}
 	cmd := &cobra.Command{
 		Use:               "nfpm",
-		Short:             "Packages apps on RPM, Deb, APK and Arch Linux formats based on a YAML configuration file",
-		Long:              `nFPM is a simple and 0-dependencies deb, rpm, apk and arch linux packager written in Go.`,
+		Short:             "Packages apps on RPM, Deb, APK, Arch Linux, and ipk formats based on a YAML configuration file",
+		Long:              `nFPM is a simple and 0-dependencies apk, arch, deb, ipk and rpm linux packager written in Go.`,
 		Version:           version.String(),
 		SilenceUsage:      true,
 		SilenceErrors:     true,

ipk/ipk.go

@@ -0,0 +1,512 @@
+// Package ipk implements nfpm.Packager providing .ipk bindings.
+//
+// IPK is a package format used by the opkg package manager, which is very
+// similar to the Debian package format.  Generally, the package format is
+// stripped down and simplified compared to the Debian package format.
+// Yocto/OpenEmbedded/OpenWRT uses the IPK format for its package management.
+package ipk
+
+import (
+	"archive/tar"
+	"bufio"
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+	"text/template"
+	"time"
+
+	"github.com/goreleaser/nfpm/v2"
+	"github.com/goreleaser/nfpm/v2/deprecation"
+	"github.com/goreleaser/nfpm/v2/files"
+	"github.com/goreleaser/nfpm/v2/internal/modtime"
+)
+
+const packagerName = "ipk"
+
+// nolint: gochecknoinits
+func init() {
+	nfpm.RegisterPackager(packagerName, Default)
+}
+
+// nolint: gochecknoglobals
+var archToIPK = map[string]string{
+	// all --> all
+	"386":      "i386",
+	"amd64":    "x86_64",
+	"arm64":    "arm64",
+	"arm5":     "armel",
+	"arm6":     "armhf",
+	"arm7":     "armhf",
+	"mips64le": "mips64el",
+	"mipsle":   "mipsel",
+	"ppc64le":  "ppc64el",
+	"s390":     "s390x",
+}
+
+func ensureValidArch(info *nfpm.Info) *nfpm.Info {
+	if info.IPK.Arch != "" {
+		info.Arch = info.IPK.Arch
+	} else if arch, ok := archToIPK[info.Arch]; ok {
+		info.Arch = arch
+	}
+
+	return info
+}
+
+// Default ipk packager.
+// nolint: gochecknoglobals
+var Default = &IPK{}
+
+// IPK is a ipk packager implementation.
+type IPK struct{}
+
+// ConventionalFileName returns a file name according
+// to the conventions for ipk packages. Ipk packages generally follow
+// the conventions set by debian.  See:
+// https://manpages.debian.org/buster/dpkg-dev/dpkg-name.1.en.html
+func (*IPK) ConventionalFileName(info *nfpm.Info) string {
+	info = ensureValidArch(info)
+
+	version := info.Version
+	if info.Prerelease != "" {
+		version += "~" + info.Prerelease
+	}
+
+	if info.VersionMetadata != "" {
+		version += "+" + info.VersionMetadata
+	}
+
+	if info.Release != "" {
+		version += "-" + info.Release
+	}
+
+	// package_version_architecture.package-type
+	return fmt.Sprintf("%s_%s_%s.ipk", info.Name, version, info.Arch)
+}
+
+// ConventionalExtension returns the file name conventionally used for IPK packages
+func (*IPK) ConventionalExtension() string {
+	return ".ipk"
+}
+
+// SetPackagerDefaults sets the default values for the IPK packager.
+func (*IPK) SetPackagerDefaults(info *nfpm.Info) {
+	// Priority should be set on all packages per:
+	//   https://www.debian.org/doc/debian-policy/ch-archive.html#priorities
+	// "optional" seems to be the safe/sane default here
+	if info.Priority == "" {
+		info.Priority = "optional"
+	}
+
+	// The safe thing here feels like defaulting to something like below.
+	// That will prevent existing configs from breaking anyway...  Wondering
+	// if in the long run we should be more strict about this and error when
+	// not set?
+	if strings.TrimSpace(info.Maintainer) == "" {
+		deprecation.Println("Leaving the 'maintainer' field unset will not be allowed in a future version")
+		info.Maintainer = "Unset Maintainer <unset@localhost>"
+	}
+}
+
+// Package writes a new ipk package to the given writer using the given info.
+func (d *IPK) Package(info *nfpm.Info, ipk io.Writer) error {
+	info = ensureValidArch(info)
+
+	if err := nfpm.PrepareForPackager(info, packagerName); err != nil {
+		return err
+	}
+
+	// Set up some ipk specific defaults
+	d.SetPackagerDefaults(info)
+
+	// Strip out any custom fields that are disallowed.
+	stripDisallowedFields(info)
+
+	contents, err := newTGZ("ipk",
+		func(tw *tar.Writer) error {
+			return createIPK(info, tw)
+		},
+	)
+	if err != nil {
+		return err
+	}
+
+	_, err = ipk.Write(contents)
+
+	return err
+}
+
+// createIPK creates a new ipk package using the given tar writer and info.
+func createIPK(info *nfpm.Info, ipk *tar.Writer) error {
+	var installSize int64
+
+	data, err := newTGZ("data.tar.gz",
+		func(tw *tar.Writer) error {
+			var err error
+			installSize, err = populateDataTar(info, tw)
+			return err
+		},
+	)
+	if err != nil {
+		return err
+	}
+
+	control, err := newTGZ("control.tar.gz",
+		func(tw *tar.Writer) error {
+			return populateControlTar(info, tw, installSize)
+		},
+	)
+	if err != nil {
+		return err
+	}
+
+	mtime := modtime.Get(info.MTime)
+
+	if err := writeToFile(ipk, "debian-binary", []byte("2.0\n"), mtime); err != nil {
+		return err
+	}
+
+	if err := writeToFile(ipk, "control.tar.gz", control, mtime); err != nil {
+		return err
+	}
+
+	if err := writeToFile(ipk, "data.tar.gz", data, mtime); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// populateDataTar populates the data tarball with the files specified in the info.
+func populateDataTar(info *nfpm.Info, tw *tar.Writer) (instSize int64, err error) {
+	// create files and implicit directories
+	for _, file := range info.Contents {
+		var size int64
+
+		switch file.Type {
+		case files.TypeDir, files.TypeImplicitDir:
+			err = tw.WriteHeader(
+				&tar.Header{
+					Name:     files.AsExplicitRelativePath(file.Destination),
+					Typeflag: tar.TypeDir,
+					Format:   tar.FormatGNU,
+					ModTime:  modtime.Get(info.MTime),
+					Mode:     int64(file.FileInfo.Mode),
+					Uname:    file.FileInfo.Owner,
+					Gname:    file.FileInfo.Group,
+				})
+		case files.TypeSymlink:
+			err = tw.WriteHeader(
+				&tar.Header{
+					Name:     files.AsExplicitRelativePath(file.Destination),
+					Typeflag: tar.TypeSymlink,
+					Format:   tar.FormatGNU,
+					ModTime:  modtime.Get(info.MTime),
+					Linkname: file.Source,
+				})
+		case files.TypeFile, files.TypeTree, files.TypeConfig, files.TypeConfigNoReplace:
+			size, err = writeFile(tw, file)
+		default:
+			// ignore everything else
+		}
+		if err != nil {
+			return 0, err
+		}
+		instSize += size
+	}
+
+	return instSize, nil
+}
+
+// getScripts returns the scripts for the given info.
+func getScripts(info *nfpm.Info, mtime time.Time) []files.Content {
+	return []files.Content{
+		{
+			Destination: "preinst",
+			Source:      info.Scripts.PreInstall,
+			FileInfo: &files.ContentFileInfo{
+				Mode:  0o755,
+				MTime: mtime,
+			},
+		}, {
+			Destination: "postinst",
+			Source:      info.Scripts.PostInstall,
+			FileInfo: &files.ContentFileInfo{
+				Mode:  0o755,
+				MTime: mtime,
+			},
+		}, {
+			Destination: "prerm",
+			Source:      info.Scripts.PreRemove,
+			FileInfo: &files.ContentFileInfo{
+				Mode:  0o755,
+				MTime: mtime,
+			},
+		}, {
+			Destination: "postrm",
+			Source:      info.Scripts.PostRemove,
+			FileInfo: &files.ContentFileInfo{
+				Mode:  0o755,
+				MTime: mtime,
+			},
+		},
+	}
+}
+
+// populateControlTar populates the control tarball with the control files defined
+// in the info.
+func populateControlTar(info *nfpm.Info, out *tar.Writer, instSize int64) error {
+	var body bytes.Buffer
+
+	cd := controlData{
+		Info:          info,
+		InstalledSize: instSize / 1024,
+	}
+
+	if err := renderControl(&body, cd); err != nil {
+		return err
+	}
+
+	mtime := modtime.Get(info.MTime)
+	if err := writeToFile(out, "./control", body.Bytes(), mtime); err != nil {
+		return err
+	}
+	if err := writeToFile(out, "./conffiles", conffiles(info), mtime); err != nil {
+		return err
+	}
+
+	scripts := getScripts(info, mtime)
+	for _, file := range scripts {
+		if file.Source != "" {
+			if _, err := writeFile(out, &file); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// conffiles returns the conffiles file bytes for the given info.
+func conffiles(info *nfpm.Info) []byte {
+	// nolint: prealloc
+	var confs []string
+	for _, file := range info.Contents {
+		switch file.Type {
+		case files.TypeConfig, files.TypeConfigNoReplace:
+			confs = append(confs, files.NormalizeAbsoluteFilePath(file.Destination))
+		}
+	}
+	return []byte(strings.Join(confs, "\n") + "\n")
+}
+
+// The ipk format is not formally defined, but it is similar to the deb format.
+// The two sources that were used to create this template are:
+// - https://git.yoctoproject.org/opkg/
+// - https://github.com/openwrt/opkg-lede
+//
+// Supported Fields
+//
+// R = Required
+// O = Optional
+// e = Extra
+// - = Not Supported/Ignored/Extra
+//
+//
+//              OpenWRT   Yocto
+//                    |   |
+// | Field          | W | Y | Status |
+// |----------------|---|---|--------|
+// | ABIVersion     | O | - | ✓
+// | Alternatives   | O | - | ✓
+// | Architecture   | R | R | ✓
+// | Auto-Installed | O | O | ✓
+// | Conffiles      | O | O | not needed since config files are listed in .conffiles
+// | Conflicts      | O | O | ✓
+// | Depends        | R | R | ✓
+// | Description    | R | R | ✓
+// | Essential      | O | O | ✓
+// | Filename       | - | - | an opkg field, not a package field
+// | Homepage       | e | e | ✓
+// | Installed-Size | O | O | ✓
+// | Installed-Time | - | - | an opkg field, not a package field
+// | License        | e | e | ✓
+// | Maintainer     | R | R | ✓
+// | MD5sum		    | - | - | insecure, not supported
+// | Package        | R | R | ✓
+// | Pre-Depends    | e | O | ✓
+// | Priority       | R | R | ✓
+// | Provides       | O | O | ✓
+// | Recommends     | O | O | ✓
+// | Replaces       | O | O | ✓
+// | Section        | O | O | ✓
+// | SHA256sum      | - | - | an opkg field, not a package field
+// | Size           | - | - | an opkg field, not a package field
+// | Source         | - | - | use the Fields field
+// | Status		    | - | - | an opkg state, not a package field
+// | Suggests       | O | O | ✓
+// | Tags           | O | O | ✓
+// | Vendor         | e | e | ✓
+// | Version        | R | R | ✓
+//
+// If any values in user supplied Fields are found to be duplicates of the above
+// fields, they will be stripped out.
+
+// nolint: gochecknoglobals
+var controlFields = []string{
+	"ABIVersion",
+	"Alternatives",
+	"Architecture",
+	"Auto-Installed",
+	"Conffiles",
+	"Conflicts",
+	"Depends",
+	"Description",
+	"Essential",
+	"Filename",
+	"Homepage",
+	"Installed-Size",
+	"Installed-Time",
+	"License",
+	"Maintainer",
+	"MD5sum",
+	"Package",
+	"Pre-Depends",
+	"Priority",
+	"Provides",
+	"Recommends",
+	"Replaces",
+	"Section",
+	"SHA256sum",
+	"Size",
+	// "Source", Allowed
+	"Status",
+	"Suggests",
+	"Tags",
+	"Vendor",
+	"Version",
+}
+
+// stripDisallowedFields strips out any fields that are disallowed in the ipk
+// format, ignoring case.
+func stripDisallowedFields(info *nfpm.Info) {
+	for key := range info.IPK.Fields {
+		for _, disallowed := range controlFields {
+			if strings.EqualFold(key, disallowed) {
+				delete(info.IPK.Fields, key)
+			}
+		}
+	}
+}
+
+const controlTemplate = `
+{{- /* Mandatory fields */ -}}
+Architecture: {{.Info.Arch}}
+Description: {{multiline .Info.Description}}
+Maintainer: {{.Info.Maintainer}}
+Package: {{.Info.Name}}
+Priority: {{.Info.Priority}}
+Version: {{ if .Info.Epoch}}{{ .Info.Epoch }}:{{ end }}{{.Info.Version}}
+         {{- if .Info.Prerelease}}~{{ .Info.Prerelease }}{{- end }}
+         {{- if .Info.VersionMetadata}}+{{ .Info.VersionMetadata }}{{- end }}
+         {{- if .Info.Release}}-{{ .Info.Release }}{{- end }}
+{{- /* Optional fields */ -}}
+{{- if .Info.IPK.ABIVersion}}
+ABIVersion: {{.Info.IPK.ABIVersion}}
+{{- end}}
+{{- if .Info.IPK.Alternatives}}
+Alternatives: {{ range $index, $element := .Info.IPK.Alternatives }}{{ if $index }}, {{end}}{{ $element.Priority }}:{{ $element.LinkName}}:{{ $element.Target}}{{- end }}
+{{- end}}
+{{- if .Info.IPK.AutoInstalled}}
+Auto-Installed: yes
+{{- end }}
+{{- with .Info.Conflicts}}
+Conflicts: {{join .}}
+{{- end }}
+{{- with .Info.Depends}}
+Depends: {{join .}}
+{{- end }}
+{{- if .Info.IPK.Essential}}
+Essential: yes
+{{- end }}
+{{- if .Info.Homepage}}
+Homepage: {{.Info.Homepage}}
+{{- end }}
+{{- if .Info.License}}
+License: {{.Info.License}}
+{{- end }}
+{{- if .InstalledSize }}
+Installed-Size: {{.InstalledSize}}
+{{- end }}
+{{- with .Info.IPK.Predepends}}
+Pre-Depends: {{join .}}
+{{- end }}
+{{- with nonEmpty .Info.Provides}}
+Provides: {{join .}}
+{{- end }}
+{{- with .Info.Recommends}}
+Recommends: {{join .}}
+{{- end }}
+{{- with .Info.Replaces}}
+Replaces: {{join .}}
+{{- end }}
+{{- if .Info.Section}}
+Section: {{.Info.Section}}
+{{- end }}
+{{- with .Info.Suggests}}
+Suggests: {{join .}}
+{{- end }}
+{{- with .Info.IPK.Tags}}
+Tags: {{join .}}
+{{- end }}
+{{- if .Info.Vendor}}
+Vendor: {{.Info.Vendor}}
+{{- end }}
+{{- range $key, $value := .Info.IPK.Fields }}
+{{- if $value }}
+{{$key}}: {{$value}}
+{{- end }}
+{{- end }}
+`
+
+type controlData struct {
+	Info          *nfpm.Info
+	InstalledSize int64
+}
+
+func renderControl(w io.Writer, data controlData) error {
+	tmpl := template.New("control")
+	tmpl.Funcs(template.FuncMap{
+		"join": func(strs []string) string {
+			return strings.Trim(strings.Join(strs, ", "), " ")
+		},
+		"multiline": func(strs string) string {
+			var b strings.Builder
+			s := bufio.NewScanner(strings.NewReader(strings.TrimSpace(strs)))
+			s.Scan()
+			b.Write(bytes.TrimSpace(s.Bytes()))
+			for s.Scan() {
+				b.WriteString("\n ")
+				l := bytes.TrimSpace(s.Bytes())
+				if len(l) == 0 {
+					b.WriteByte('.')
+				} else {
+					b.Write(l)
+				}
+			}
+			return b.String()
+		},
+		"nonEmpty": func(strs []string) []string {
+			var result []string
+			for _, s := range strs {
+				s := strings.TrimSpace(s)
+				if s == "" {
+					continue
+				}
+				result = append(result, s)
+			}
+			return result
+		},
+	})
+	return template.Must(tmpl.Parse(controlTemplate)).Execute(w, data)
+}

ipk/tar.go

@@ -0,0 +1,108 @@
+package ipk
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/goreleaser/nfpm/v2/files"
+)
+
+// newTGZ creates a new tar.gz archive with the given name and populates it
+// with the given function.
+//
+// The function returns the bytes of the archive, its size and an error if any.
+func newTGZ(name string, populate func(*tar.Writer) error) ([]byte, error) {
+	var buf bytes.Buffer
+
+	gz := gzip.NewWriter(&buf)
+	tarball := tar.NewWriter(gz)
+
+	// the writers are properly closed later, this is just in case that we error out
+	defer gz.Close()      // nolint: errcheck
+	defer tarball.Close() // nolint: errcheck
+
+	if err := populate(tarball); err != nil {
+		return nil, fmt.Errorf("cannot populate '%s': %w", name, err)
+	}
+
+	if err := tarball.Close(); err != nil {
+		return nil, fmt.Errorf("cannot close '%s': %w", name, err)
+	}
+
+	if err := gz.Close(); err != nil {
+		return nil, fmt.Errorf("cannot close '%s': %w", name, err)
+	}
+
+	return buf.Bytes(), nil
+}
+
+// writeFile writes a file from the filesystem to the tarball.
+func writeFile(out *tar.Writer, file *files.Content) (int64, error) {
+	f, err := os.OpenFile(file.Source, os.O_RDONLY, 0o600) //nolint:gosec
+	if err != nil {
+		return 0, fmt.Errorf("could not open file %s to read and include in the archive: %w", file.Source, err)
+	}
+	defer f.Close() // nolint: errcheck
+
+	header, err := tar.FileInfoHeader(file, file.Source)
+	if err != nil {
+		return 0, err
+	}
+
+	content, err := io.ReadAll(f)
+	if err != nil {
+		return 0, err
+	}
+
+	size := int64(len(content))
+
+	// tar.FileInfoHeader only uses file.Mode().Perm() which masks the mode with
+	// 0o777 which we don't want because we want to be able to set the suid bit.
+	header.Mode = int64(file.Mode())
+	header.Format = tar.FormatGNU
+	header.Name = files.AsExplicitRelativePath(file.Destination)
+	header.Size = size
+	header.Uname = file.FileInfo.Owner
+	header.Gname = file.FileInfo.Group
+	if err := out.WriteHeader(header); err != nil {
+		return 0, fmt.Errorf("cannot write tar header for file %s to archive: %w", file.Source, err)
+	}
+
+	n, err := out.Write(content)
+	if err != nil {
+		return 0, fmt.Errorf("%s: failed to copy: %w", file.Source, err)
+	}
+
+	if int64(n) != size {
+		return 0, fmt.Errorf("%s: failed to copy: expected %d bytes, copied %d", file.Source, size, n)
+	}
+
+	return size, nil
+}
+
+// writeToFile writes a file to the tarball where the contents are an array of bytes.
+func writeToFile(out *tar.Writer, filename string, content []byte, mtime time.Time) error {
+	header := tar.Header{
+		Name:     files.AsExplicitRelativePath(filename),
+		Size:     int64(len(content)),
+		Mode:     0o644,
+		ModTime:  mtime,
+		Typeflag: tar.TypeReg,
+		Format:   tar.FormatGNU,
+	}
+
+	if err := out.WriteHeader(&header); err != nil {
+		return fmt.Errorf("cannot write file header %s to archive: %w", header.Name, err)
+	}
+
+	_, err := out.Write(content)
+	if err != nil {
+		return fmt.Errorf("cannot write file %s payload: %w", header.Name, err)
+	}
+	return nil
+}

ipk/tar_test.go

@@ -0,0 +1,167 @@
+package ipk
+
+import (
+	"archive/tar"
+	"bytes"
+	"compress/gzip"
+	"errors"
+	"io"
+	"path"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_newTGZ(t *testing.T) {
+	unknownErr := errors.New("unknown error")
+
+	tests := []struct {
+		description string
+		name        string
+		populate    func(*tar.Writer) error
+		file        string
+		expectedErr error
+	}{
+		{
+			description: "simple",
+			name:        "simple.tar",
+			populate: func(tw *tar.Writer) error {
+				return writeToFile(tw, "simple.txt", []byte("hello, world"), time.Now())
+			},
+			file: "./simple.txt",
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.description, func(t *testing.T) {
+			assert := assert.New(t)
+			require := require.New(t)
+
+			got, err := newTGZ(tc.name, tc.populate)
+
+			if tc.expectedErr == nil {
+				require.NoError(err)
+				require.NotNil(got)
+
+				gz, err := gzip.NewReader(bytes.NewReader(got))
+				require.NoError(err)
+				require.NotNil(gz)
+				defer gz.Close() // nolint: errcheck
+
+				assert.True(tarContains(t, gz, tc.file))
+				return
+			}
+
+			require.Error(err)
+			if !errors.Is(tc.expectedErr, unknownErr) {
+				assert.ErrorIs(err, tc.expectedErr)
+			}
+		})
+	}
+}
+
+func extractFileFromTar(tb testing.TB, tarFile []byte, filename string) []byte {
+	tb.Helper()
+
+	tr := tar.NewReader(bytes.NewReader(tarFile))
+	for {
+		hdr, err := tr.Next()
+		if errors.Is(err, io.EOF) {
+			break // End of archive
+		}
+		require.NoError(tb, err)
+
+		if path.Join("/", hdr.Name) != path.Join("/", filename) {
+			continue
+		}
+
+		fileContents, err := io.ReadAll(tr)
+		require.NoError(tb, err)
+
+		return fileContents
+	}
+
+	tb.Fatalf("file %q does not exist in tar", filename)
+
+	return nil
+}
+
+func tarContains(tb testing.TB, r io.Reader, filename string) bool {
+	tb.Helper()
+
+	tr := tar.NewReader(r)
+	for {
+		hdr, err := tr.Next()
+		if errors.Is(err, io.EOF) {
+			break // End of archive
+		}
+		require.NoError(tb, err)
+
+		if path.Join("/", hdr.Name) == path.Join("/", filename) { // nolint:gosec
+			return true
+		}
+	}
+
+	return false
+}
+
+func tarContents(tb testing.TB, tarFile []byte) []string {
+	tb.Helper()
+
+	contents := []string{}
+
+	tr := tar.NewReader(bytes.NewReader(tarFile))
+	for {
+		hdr, err := tr.Next()
+		if errors.Is(err, io.EOF) {
+			break // End of archive
+		}
+		require.NoError(tb, err)
+
+		contents = append(contents, hdr.Name)
+	}
+
+	return contents
+}
+
+func getTree(tb testing.TB, tarFile []byte) []string {
+	tb.Helper()
+
+	var result []string
+	tr := tar.NewReader(bytes.NewReader(tarFile))
+	for {
+		hdr, err := tr.Next()
+		if errors.Is(err, io.EOF) {
+			break // End of archive
+		}
+		require.NoError(tb, err)
+
+		result = append(result, hdr.Name)
+	}
+
+	return result
+}
+
+func extractFileHeaderFromTar(tb testing.TB, tarFile []byte, filename string) *tar.Header {
+	tb.Helper()
+
+	tr := tar.NewReader(bytes.NewReader(tarFile))
+	for {
+		hdr, err := tr.Next()
+		if errors.Is(err, io.EOF) {
+			break // End of archive
+		}
+		require.NoError(tb, err)
+
+		if path.Join("/", hdr.Name) != path.Join("/", filename) { // nolint:gosec
+			continue
+		}
+
+		return hdr
+	}
+
+	tb.Fatalf("file %q does not exist in tar", filename)
+
+	return nil
+}

ipk/testdata/bad_provides.golden

@@ -0,0 +1,15 @@
+Architecture: amd64
+Description: Foo does things
+Maintainer: Carlos A Becker <pkg@carlosbecker.com>
+Package: foo
+Priority: extra
+Version: 1.0.0
+Conflicts: zsh
+Depends: bash
+Homepage: http://carlosbecker.com
+Pre-Depends: less
+Recommends: git
+Replaces: svn
+Section: default
+Suggests: bash
+Vendor: nope

ipk/testdata/control.golden

@@ -0,0 +1,17 @@
+Architecture: amd64
+Description: Foo does things
+Maintainer: Carlos A Becker <pkg@carlosbecker.com>
+Package: foo
+Priority: extra
+Version: 1.0.0
+Conflicts: zsh
+Depends: bash
+Homepage: http://carlosbecker.com
+Installed-Size: 10
+Pre-Depends: less
+Provides: bzr
+Recommends: git
+Replaces: svn
+Section: default
+Suggests: bash
+Vendor: nope

ipk/testdata/control2.golden

@@ -0,0 +1,10 @@
+Architecture: amd64
+Description: Foo does things
+Maintainer: Carlos A Becker <pkg@carlosbecker.com>
+Package: foo
+Priority: extra
+Version: 1.0.0
+Homepage: http://carlosbecker.com
+Installed-Size: 10
+Section: default
+Vendor: nope

ipk/testdata/control3.golden

@@ -0,0 +1,10 @@
+Architecture: amd64
+Description: Foo does things
+Maintainer: Carlos A Becker <pkg@carlosbecker.com>
+Package: foo
+Priority: extra
+Version: 1.0.0
+Homepage: http://carlosbecker.com
+Installed-Size: 10
+Section: default
+Bugs: https://github.com/goreleaser/nfpm/issues

ipk/testdata/control4.golden

@@ -0,0 +1,10 @@
+Architecture: amd64
+Description: Foo does things
+Maintainer: Carlos A Becker <pkg@carlosbecker.com>
+Package: foo
+Priority: extra
+Version: 1.0.0~beta+meta-2
+Homepage: http://carlosbecker.com
+Installed-Size: 10
+Section: default
+Vendor: nope

ipk/testdata/control_most.golden

@@ -0,0 +1,14 @@
+Architecture: amd64
+Description: Foo does things
+Maintainer: Carlos A Becker <pkg@carlosbecker.com>
+Package: foo
+Priority: extra
+Version: 1.0.0
+ABIVersion: 1
+Auto-Installed: yes
+Essential: yes
+Homepage: http://carlosbecker.com
+License: MIT
+Installed-Size: 10
+Section: default
+Bugs: https://github.com/goreleaser/nfpm/issues

ipk/testdata/minimal.golden

@@ -0,0 +1,6 @@
+Architecture: arm64
+Description: Minimal does nothing
+Maintainer: maintainer
+Package: minimal
+Priority: extra
+Version: 1.0.0

ipk/testdata/multiline.golden

@@ -0,0 +1,9 @@
+Architecture: riscv64
+Description: This field is a
+ multiline field
+ .
+ that should work.
+Maintainer: someone
+Package: multiline
+Priority: extra
+Version: 1.0.0

ipk/testdata/templates.golden

@@ -0,0 +1,4 @@
+Template: templates/lala
+Type: string
+Description: Set lala for templates.
+ For the test purpose this templates.golden is created.

ipk/testdata/withepoch.golden

@@ -0,0 +1,7 @@
+Architecture: arm64
+Description: Has an epoch added to it's version
+Maintainer: 
+Package: withepoch
+Priority: extra
+Version: 2:1.0.0
+Section: default

nfpm.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"io/fs"
 	"os"
+	"sort"
 	"strings"
 	"sync"
 	"time"
@@ -59,6 +60,22 @@ func Get(format string) (Packager, error) {
 	return p, nil
 }
 
+// Enumerate lists the available packagers
+func Enumerate() []string {
+	lock.Lock()
+	defer lock.Unlock()
+
+	list := make([]string, 0, len(packagers))
+	for key := range packagers {
+		if key != "" {
+			list = append(list, key)
+		}
+	}
+
+	sort.Strings(list)
+	return list
+}
+
 // Parse decodes YAML data from an io.Reader into a configuration struct.
 func Parse(in io.Reader) (config Config, err error) {
 	return ParseWithEnvMapping(in, os.Getenv)
@@ -252,6 +269,15 @@ func (c *Config) expandEnvVars() {
 		c.Info.Deb.Fields[k] = os.Expand(v, c.envMappingFunc)
 	}
 	c.Info.Deb.Predepends = c.expandEnvVarsStringSlice(c.Info.Deb.Predepends)
+
+	// IPK specific
+	for k, v := range c.Info.IPK.Fields {
+		c.Info.IPK.Fields[k] = os.Expand(v, c.envMappingFunc)
+	}
+	c.Info.IPK.Predepends = c.expandEnvVarsStringSlice(c.Info.IPK.Predepends)
+
+	// RPM specific
+	c.Info.RPM.Packager = os.Expand(c.RPM.Packager, c.envMappingFunc)
 }
 
 // Info contains information about a single package.
@@ -332,6 +358,7 @@ type Overridables struct {
 	Deb        Deb            `yaml:"deb,omitempty" json:"deb,omitempty" jsonschema:"title=deb-specific settings"`
 	APK        APK            `yaml:"apk,omitempty" json:"apk,omitempty" jsonschema:"title=apk-specific settings"`
 	ArchLinux  ArchLinux      `yaml:"archlinux,omitempty" json:"archlinux,omitempty" jsonschema:"title=archlinux-specific settings"`
+	IPK        IPK            `yaml:"ipk,omitempty" json:"ipk,omitempty" jsonschema:"title=ipk-specific settings"`
 }
 
 type ArchLinux struct {
@@ -440,6 +467,25 @@ type DebScripts struct {
 	Config    string `yaml:"config,omitempty" json:"config,omitempty" jsonschema:"title=config"`
 }
 
+// IPK is custom configs that are only available on deb packages.
+type IPK struct {
+	ABIVersion    string            `yaml:"abi_version,omitempty" json:"abi_version,omitempty" jsonschema:"title=abi version"`
+	Alternatives  []IPKAlternative  `yaml:"alternatives,omitempty" json:"alternatives,omitempty" jsonschema:"title=alternatives"`
+	Arch          string            `yaml:"arch,omitempty" json:"arch,omitempty" jsonschema:"title=architecture in deb nomenclature"`
+	AutoInstalled bool              `yaml:"auto_installed,omitempty" json:"auto_installed,omitempty" jsonschema:"title=auto installed,default=false"`
+	Essential     bool              `yaml:"essential,omitempty" json:"essential,omitempty" jsonschema:"title=whether package is essential,default=false"`
+	Fields        map[string]string `yaml:"fields,omitempty" json:"fields,omitempty" jsonschema:"title=fields"`
+	Predepends    []string          `yaml:"predepends,omitempty" json:"predepends,omitempty" jsonschema:"title=predepends directive,example=nfpm"`
+	Tags          []string          `yaml:"tags,omitempty" json:"tags,omitempty" jsonschema:"title=tags"`
+}
+
+// IPKAlternative represents an alternative for an IPK package.
+type IPKAlternative struct {
+	Priority int    `yaml:"priority,omitempty" json:"priority,omitempty" jsonschema:"title=priority"`
+	Target   string `yaml:"target,omitempty" json:"target,omitempty" jsonschema:"title=target"`
+	LinkName string `yaml:"link_name,omitempty" json:"link_name,omitempty" jsonschema:"title=link name"`
+}
+
 // Scripts contains information about maintainer scripts for packages.
 type Scripts struct {
 	PreInstall  string `yaml:"preinstall,omitempty" json:"preinstall,omitempty" jsonschema:"title=pre install"`

nfpm_test.go

@@ -299,6 +299,7 @@ func TestParseFile(t *testing.T) {
 	nfpm.RegisterPackager("deb", &fakePackager{})
 	nfpm.RegisterPackager("rpm", &fakePackager{})
 	nfpm.RegisterPackager("apk", &fakePackager{})
+	nfpm.RegisterPackager("ipk", &fakePackager{})
 	_, err = parseAndValidate("./testdata/overrides.yaml")
 	require.NoError(t, err)
 	_, err = parseAndValidate("./testdata/doesnotexist.yaml")

testdata/acceptance/core.complex.yaml

@@ -62,6 +62,12 @@ contents:
     file_info:
       mode: 04755
 
+  - packager: ipk
+    src: ./testdata/fake
+    dst: /usr/bin/fake2
+    file_info:
+      mode: 04755
+
 scripts:
   preinstall: ./testdata/acceptance/scripts/preinstall.sh
   postinstall: ./testdata/acceptance/scripts/postinstall.sh

testdata/acceptance/core.overrides.yaml

@@ -49,3 +49,10 @@ overrides:
     scripts:
       postinstall: ./testdata/acceptance/scripts/postinstall.sh
       preremove: ./testdata/acceptance/scripts/preremove.sh
+  ipk:
+    depends:
+      - bash
+      - fish
+    scripts:
+      postinstall: ./testdata/acceptance/scripts/postinstall.sh
+      preremove: ./testdata/acceptance/scripts/preremove.sh

testdata/acceptance/ipk.alternatives.yaml

@@ -0,0 +1,18 @@
+name: "foo"
+arch: "all"
+platform: "linux"
+version: "v1.0.0"
+maintainer: "John Doe <john@example.com>"
+description: Foo conflicts dummy
+contents:
+- src: ./testdata/fake
+  dst: /usr/bin/fake
+ipk:
+  alternatives:
+  - priority: 100
+    target: /usr/bin/fake
+    link_name: /usr/bin/bar
+      
+  - link_name: /usr/bin/baz
+    target: /usr/bin/fake
+    priority: 200

testdata/acceptance/ipk.conflicts.yaml

@@ -0,0 +1,8 @@
+name: "foo"
+arch: "all"
+platform: "linux"
+version: "v1.0.0"
+maintainer: "John Doe <john@example.com>"
+description: Foo conflicts dummy
+conflicts:
+  - dummy

testdata/acceptance/ipk.dockerfile

@@ -0,0 +1,172 @@
+FROM openwrt/rootfs AS test_base
+ARG package
+#ARG CACHEBUST=1 
+RUN mkdir -p /var/lock && \
+    mkdir -p /var/run && \
+    mkdir -p /tmp
+RUN echo "${package}"
+COPY ${package} /tmp/foo.ipk
+
+# ---- minimal test ----
+FROM test_base AS min
+RUN opkg install /tmp/foo.ipk
+
+
+# ---- symlink test ----
+FROM min AS symlink
+RUN ls -l /path/to/symlink | grep "/path/to/symlink -> /etc/foo/whatever.conf"
+
+
+# ---- simple test ----
+FROM min AS simple
+RUN test -e /usr/bin/fake
+RUN test -f /etc/foo/whatever.conf
+RUN echo wat >> /etc/foo/whatever.conf
+RUN opkg remove foo
+RUN test -f /etc/foo/whatever.conf
+RUN test ! -f /usr/bin/fake
+
+
+# ---- no-glob test ----
+FROM min AS no-glob
+RUN test -d /usr/share/whatever/
+RUN test -f /usr/share/whatever/file1
+RUN test -f /usr/share/whatever/file2
+RUN test -d /usr/share/whatever/folder2
+RUN test -f /usr/share/whatever/folder2/file1
+RUN test -f /usr/share/whatever/folder2/file2
+
+
+# ---- complex test ----
+FROM test_base AS complex
+RUN opkg install coreutils-stat
+RUN test "$(opkg status fish)" = ""
+RUN opkg install /tmp/foo.ipk > install.log
+RUN opkg depends foo | grep "bash"
+RUN cat install.log | grep "package foo suggests installing zsh"
+RUN test "$(opkg status fish)" != ""
+RUN opkg info foo | grep "Provides: fake"
+RUN test -e /usr/bin/fake
+RUN test -f /etc/foo/whatever.conf
+RUN test -d /usr/share/whatever/
+RUN test -d /usr/share/whatever/folder
+RUN test -f /usr/share/whatever/folder/file1
+RUN test -f /usr/share/whatever/folder/file2
+RUN test -d /usr/share/whatever/folder/folder2
+RUN test -f /usr/share/whatever/folder/folder2/file1
+RUN test -f /usr/share/whatever/folder/folder2/file2
+RUN test -d /var/log/whatever
+RUN test -d /usr/share/foo
+RUN test -d /usr/foo/bar/something
+RUN test -d /etc/something
+RUN test -f /etc/something/a
+RUN test -f /etc/something/b
+RUN test -d /etc/something/c
+RUN test -f /etc/something/c/d
+RUN test $(stat -c %a /usr/bin/fake2) -eq 4755
+RUN test -f /tmp/preinstall-proof
+RUN test -f /tmp/postinstall-proof
+RUN test ! -f /tmp/preremove-proof
+RUN test ! -f /tmp/postremove-proof
+RUN echo wat >> /etc/foo/whatever.conf
+RUN opkg remove foo
+RUN test -f /etc/foo/whatever.conf
+RUN test ! -f /usr/bin/fake
+RUN test ! -f /usr/bin/fake2
+RUN test -f /tmp/preremove-proof
+RUN test -f /tmp/postremove-proof
+
+# ---- overrides test ----
+FROM min AS overrides
+RUN test -e /usr/bin/fake
+RUN test -f /etc/foo/whatever.conf
+RUN test ! -f /tmp/preinstall-proof
+RUN test -f /tmp/postinstall-proof
+RUN test ! -f /tmp/preremove-proof
+RUN test ! -f /tmp/postremove-proof
+RUN echo wat >> /etc/foo/whatever.conf
+RUN opkg remove foo
+RUN test -f /etc/foo/whatever.conf
+RUN test ! -f /usr/bin/fake
+RUN test -f /tmp/preremove-proof
+RUN test ! -f /tmp/postremove-proof
+
+# ---- meta test ----
+FROM test_base AS meta
+RUN opkg install /tmp/foo.ipk
+RUN command -v zsh
+
+# ---- env-var-version test ----
+FROM min AS env-var-version
+ENV EXPECTVER="Version: 1.0.0~0.1.b1+git.abcdefgh"
+RUN opkg info foo | grep "Version" > found
+RUN export FOUND_VER="$(cat found)" && \
+	echo "Expected: '${EXPECTVER}' :: Found: '${FOUND_VER}'" && \
+	test "${FOUND_VER}" = "${EXPECTVER}"
+
+# ---- changelog test ----
+FROM test_base AS withchangelog
+
+# ---- signed test ----
+FROM test_base AS signed
+
+# ----- IPK Specific Tests -----
+
+# ---- alternatives test ----
+FROM test_base AS alternatives
+RUN test ! -e /usr/bin/foo
+RUN test ! -e /usr/bin/bar
+RUN test ! -e /usr/bin/baz
+RUN opkg install /tmp/foo.ipk
+RUN test -e /usr/bin/fake
+RUN test -e /usr/bin/bar
+RUN test -e /usr/bin/baz
+
+# ---- conflicts test ----
+FROM test_base AS conflicts
+COPY dummy.ipk /tmp/dummy.ipk
+# install dummy package
+RUN opkg install /tmp/dummy.ipk
+# make sure foo can't be installed
+RUN opkg install /tmp/foo.ipk 2>&1 | grep "Cannot install package foo"
+# make sure foo can be installed if dummy is not installed
+RUN opkg remove dummy
+RUN opkg install /tmp/foo.ipk
+
+# ---- predepends test ----
+FROM test_base AS predepends
+COPY dummy.ipk /tmp/dummy.ipk
+RUN opkg install /tmp/foo.ipk 2>&1 | grep "cannot find dependency dummy for foo"
+RUN opkg install /tmp/dummy.ipk
+RUN opkg install /tmp/foo.ipk
+
+
+# ---- upgrade test ----
+FROM test_base AS upgrade
+ARG oldpackage
+RUN echo "${oldpackage}"
+COPY ${oldpackage} /tmp/old_foo.ipk
+RUN opkg install /tmp/old_foo.ipk
+
+RUN test -f /tmp/preinstall-proof
+RUN cat /tmp/preinstall-proof | grep "Install"
+
+RUN test -f /tmp/postinstall-proof
+RUN cat /tmp/postinstall-proof | grep "Install"
+
+# The upgrade process doesn't allow a local upgrade.
+RUN opkg install /tmp/foo.ipk
+
+RUN test -f /tmp/preremove-proof
+RUN cat /tmp/preremove-proof | grep "Upgrade"
+
+RUN test -f /tmp/postremove-proof
+RUN cat /tmp/postremove-proof | grep "Upgrade"
+
+RUN test -f /tmp/preinstall-proof
+RUN cat /tmp/preinstall-proof | grep "Upgrade"
+
+# The upgrade process doesn't allow a local upgrade,
+# so the following test will fail.
+#RUN test -d /tmp/postinstall-proof
+#RUN cat /tmp/postinstall-proof | grep "Upgrade"

testdata/acceptance/ipk.predepends.yaml

@@ -0,0 +1,9 @@
+name: "foo"
+arch: "all"
+platform: "linux"
+version: "v1.0.0"
+maintainer: "John Doe <john@example.com>"
+description: Foo breaks dummy
+ipk:
+  predepends:
+    - dummy