pkgfile

Documentation

Overview

Package pkgfile extracts files from Debian and RPM packages.

This is deliberately not a package manager: it reads the payload archive and nothing else. No control metadata is parsed, no dependencies are resolved, no scripts are considered. The only use case is harvesting files that live at a well-known path inside a package, such as the CA certificates in ca-certificates.deb.

Payloads compressed with xz are rejected rather than decompressed: a pure-Go xz decoder is not in the standard library, and the core img tool deliberately takes no dependency beyond go-containerregistry and the stdlib.

Index

• type Entry
  • func ExtractDeb(debPath string, match Matcher) ([]Entry, error)
  • func ExtractRPM(rpmPath string, match Matcher) ([]Entry, error)
• type ErrUnsupportedCompression
  • func (e *ErrUnsupportedCompression) Error() string
• type Matcher
  • func PrefixMatcher(prefixes ...string) Matcher

Types

type Entry

type Entry struct {
	// Path is the file's path inside the package, without a leading "/".
	Path string
	// Content is the file's bytes.
	Content []byte
}

Entry is one extracted regular file.

func ExtractDeb

func ExtractDeb(debPath string, match Matcher) ([]Entry, error)

ExtractDeb returns the files of a .deb package's data archive that match.

A .deb is an ar archive holding, in order, debian-binary, control.tar* and data.tar*. Only the data member is read.

func ExtractRPM

func ExtractRPM(rpmPath string, match Matcher) ([]Entry, error)

ExtractRPM returns the files of an .rpm package's payload that match.

The layout read here is: a 96-byte lead, the signature header (padded to an 8-byte boundary), the main header, and then the compressed cpio payload. Only the payload compressor is read out of the header; nothing else about the package is interpreted.

type ErrUnsupportedCompression

type ErrUnsupportedCompression struct {
	// Package is the path of the package file.
	Package string
	// Compression names the format, e.g. "xz".
	Compression string
}

ErrUnsupportedCompression reports a payload this package cannot decompress.

func (*ErrUnsupportedCompression) Error

func (e *ErrUnsupportedCompression) Error() string

type Matcher

type Matcher func(path string) bool

Matcher decides whether a path inside a package should be extracted.

func PrefixMatcher

func PrefixMatcher(prefixes ...string) Matcher

PrefixMatcher matches any path under one of the given directory prefixes, or equal to one of them.