feat: Add archive extraction support for http(s)

This enables archive extraction for the zip format and the
gz/tar/tar.gz formats. If a user provides an http(s) link to one of
these formats, pullman will now automatically extract the contents
into the destination directory.

Signed-off-by: Paul Van Eck <pvaneck@us.ibm.com>

pullman/helpers.go

@@ -14,12 +14,61 @@
 package pullman
 
 import (
+	"archive/tar"
+	"archive/zip"
+	"bufio"
+	"bytes"
+	"compress/gzip"
 	"fmt"
 	"hash/fnv"
+	"io"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
+type FileFormat struct {
+	MagicBytes []byte
+	Offset     int
+	Extension  string
+}
+
+// Magic byte values pulled from: https://en.wikipedia.org/wiki/List_of_file_signatures
+var fileFormats = []FileFormat{
+	{
+		MagicBytes: []byte{0x75, 0x73, 0x74, 0x61, 0x72, 0x00, 0x30, 0x30},
+		Offset:     257,
+		Extension:  "tar",
+	},
+	{
+		MagicBytes: []byte{0x75, 0x73, 0x74, 0x61, 0x72, 0x20, 0x20, 0x00},
+		Offset:     257,
+		Extension:  "tar",
+	},
+	{
+		MagicBytes: []byte{0x1F, 0x8B},
+		Offset:     0,
+		Extension:  "gz",
+	},
+	{
+		MagicBytes: []byte{0x50, 0x4B, 0x03, 0x04},
+		Offset:     0,
+		Extension:  "zip",
+	},
+
+	{
+		MagicBytes: []byte{0x50, 0x4B, 0x05, 0x06},
+		Offset:     0,
+		Extension:  "zip",
+	},
+
+	{
+		MagicBytes: []byte{0x50, 0x4B, 0x07, 0x08},
+		Offset:     0,
+		Extension:  "zip",
+	},
+}
+
 // OpenFile will check the path and the filesystem for mismatch errors
 func OpenFile(path string) (*os.File, error) {
 	// resource paths need to be compatible with a local filesystem download
@@ -57,3 +106,147 @@ func HashStrings(strings ...string) string {
 
 	return fmt.Sprintf("%#x", h.Sum64())
 }
+
+// Extract a zip file into the provided destination directory.
+func ExtractZip(filePath string, dest string) error {
+	zipReader, err := zip.OpenReader(filePath)
+	if err != nil {
+		return fmt.Errorf("unable to open '%s' for reading: %w", filePath, err)
+	}
+	defer zipReader.Close()
+
+	prefix := filepath.Clean(dest) + string(os.PathSeparator)
+	for _, zipFileEntry := range zipReader.File {
+		destFilePath := filepath.Join(dest, zipFileEntry.Name)
+
+		// Zip slip vulnerability check
+		if !strings.HasPrefix(destFilePath, prefix) {
+			return fmt.Errorf("%s: illegal file path", destFilePath)
+		}
+
+		if zipFileEntry.FileInfo().IsDir() {
+			err = os.MkdirAll(destFilePath, 0755)
+			if err != nil {
+				return fmt.Errorf("error creating new directory %s", destFilePath)
+			}
+			continue
+		}
+
+		file, fileErr := OpenFile(destFilePath)
+		if fileErr != nil {
+			return fmt.Errorf("unable to open local file '%s' for writing: %w", destFilePath, fileErr)
+		}
+		defer file.Close()
+
+		zippedRc, err := zipFileEntry.Open()
+		if err != nil {
+			return fmt.Errorf("error opening zip file entry: %w", err)
+		}
+		defer zippedRc.Close()
+
+		if _, err = io.Copy(file, zippedRc); err != nil {
+			return fmt.Errorf("error writing zip resource to local file '%s': %w", destFilePath, err)
+		}
+
+	}
+	return nil
+}
+
+// Extract a tar archive file into the provided destination directory.
+func ExtractTar(filePath string, dest string) error {
+	tarFile, err := os.Open(filePath)
+	if err != nil {
+		return fmt.Errorf("unable to open '%s' for reading: %w", filePath, err)
+	}
+	defer tarFile.Close()
+
+	tr := tar.NewReader(tarFile)
+	for {
+		header, err := tr.Next()
+
+		if err == io.EOF {
+			break
+		}
+
+		if err != nil {
+			return fmt.Errorf("error reading tar archive entry: %w", err)
+		}
+
+		if header == nil {
+			continue
+		}
+
+		destFilePath := filepath.Join(dest, header.Name)
+		if header.Typeflag == tar.TypeDir {
+			err = os.MkdirAll(destFilePath, 0755)
+			if err != nil {
+				return fmt.Errorf("error creating new directory %s", destFilePath)
+			}
+			continue
+		}
+
+		file, fileErr := OpenFile(destFilePath)
+		if fileErr != nil {
+			return fmt.Errorf("unable to open local file '%s' for writing: %w", destFilePath, fileErr)
+		}
+		defer file.Close()
+		if _, err = io.Copy(file, tr); err != nil {
+			return fmt.Errorf("error writing tar resource to local file '%s': %w", destFilePath, err)
+		}
+	}
+	return nil
+}
+
+// Extract a gzip compressed file into the provided destination file path.
+func ExtractGzip(filePath string, dest string) error {
+	gzipFile, err := os.Open(filePath)
+	if err != nil {
+		return fmt.Errorf("unable to open '%s' for reading: %w", filePath, err)
+	}
+	defer gzipFile.Close()
+	gzr, err := gzip.NewReader(gzipFile)
+	if err != nil {
+		return fmt.Errorf("unable to create gzip reader: %w", err)
+	}
+	defer gzr.Close()
+
+	file, fileErr := OpenFile(dest)
+	if fileErr != nil {
+		return fmt.Errorf("unable to open local file '%s' for writing: %w", dest, fileErr)
+	}
+	defer file.Close()
+
+	if _, err = io.Copy(file, gzr); err != nil {
+		return fmt.Errorf("error writing gzip resource to local file '%s': %w", dest, err)
+	}
+
+	return nil
+}
+
+// Get the file type based on the first few hundred bytes of the stream.
+// If the file isn't one of the expected formats, nil is returned.
+// If an error occurs while determining the file format, nil is returned.
+func GetFileFormat(filePath string) *FileFormat {
+
+	file, err := os.Open(filePath)
+	if err != nil {
+		return nil
+	}
+	defer file.Close()
+
+	r := bufio.NewReader(file)
+
+	// Due to the tar magic bytes offset, this is the minimum number of bytes we need to read.
+	numBytes := 264
+	fileBytes, err := r.Peek(numBytes)
+	if err != nil {
+		return nil
+	}
+
+	for _, format := range fileFormats {
+		if bytes.Equal(fileBytes[format.Offset:format.Offset+len(format.MagicBytes)], format.MagicBytes) {
+			return &format
+		}
+	}
+	return nil
+}