refactor: Decompose fetch func

pkg/config/error.go

@@ -3,6 +3,16 @@ package config
 import "errors"
 
 var (
-	ErrUnsupportedEncryptionFormat  = errors.New("unsupported encryption format")
 	ErrUnsupportedCompressionFormat = errors.New("unsupported compression format")
+	ErrUnsupportedEncryptionFormat  = errors.New("unsupported encryption format")
+	ErrUnsupportedSignatureFormat   = errors.New("unsupported signature format")
+
+	ErrIdentityUnparsable  = errors.New("recipient could not be parsed")
+	ErrRecipientUnparsable = errors.New("recipient could not be parsed")
+
+	ErrEmbeddedHeaderMissing = errors.New("embedded header is missing")
+
+	ErrSignatureFormatOnlyRegularSupport = errors.New("this signature format only supports regular files, not i.e. tape drives")
+	ErrSignatureInvalid                  = errors.New("signature invalid")
+	ErrSignatureMissing                  = errors.New("signature missing")
 )

pkg/recovery/fetch.go

@@ -1,6 +1,19 @@
 package recovery
 
 import (
+	"archive/tar"
+	"bufio"
+	"io"
+	"os"
+	"path/filepath"
+
+	"github.com/pojntfx/stfs/internal/compression"
+	"github.com/pojntfx/stfs/internal/controllers"
+	"github.com/pojntfx/stfs/internal/encryption"
+	"github.com/pojntfx/stfs/internal/formatting"
+	"github.com/pojntfx/stfs/internal/pax"
+	"github.com/pojntfx/stfs/internal/signature"
+	"github.com/pojntfx/stfs/internal/tape"
 	"github.com/pojntfx/stfs/pkg/config"
 )
 
@@ -13,7 +26,131 @@ func Fetch(
 	record int,
 	block int,
 	to string,
-	preview string,
+	preview bool,
+
+	showHeader bool,
 ) error {
+	f, isRegular, err := tape.OpenTapeReadOnly(state.Drive)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	var tr *tar.Reader
+	if isRegular {
+		// Seek to record and block
+		if _, err := f.Seek(int64((recordSize*controllers.BlockSize*record)+block*controllers.BlockSize), io.SeekStart); err != nil {
+			return err
+		}
+
+		tr = tar.NewReader(f)
+	} else {
+		// Seek to record
+		if err := controllers.SeekToRecordOnTape(f, int32(record)); err != nil {
+			return err
+		}
+
+		// Seek to block
+		br := bufio.NewReaderSize(f, controllers.BlockSize*recordSize)
+		if _, err := br.Read(make([]byte, block*controllers.BlockSize)); err != nil {
+			return err
+		}
+
+		tr = tar.NewReader(br)
+	}
+
+	hdr, err := tr.Next()
+	if err != nil {
+		return err
+	}
+
+	if err := encryption.DecryptHeader(hdr, pipes.Encryption, crypto.Identity); err != nil {
+		return err
+	}
+
+	if err := signature.VerifyHeader(hdr, isRegular, pipes.Signature, crypto.Recipient); err != nil {
+		return err
+	}
+
+	if showHeader {
+		if err := formatting.PrintCSV(formatting.TARHeaderCSV); err != nil {
+			return err
+		}
+
+		if err := formatting.PrintCSV(formatting.GetTARHeaderAsCSV(int64(record), int64(block), hdr)); err != nil {
+			return err
+		}
+	}
+
+	if !preview {
+		if to == "" {
+			to = filepath.Base(hdr.Name)
+		}
+
+		if hdr.Typeflag == tar.TypeDir {
+			return os.MkdirAll(to, hdr.FileInfo().Mode())
+		}
+
+		dstFile, err := os.OpenFile(to, os.O_WRONLY|os.O_CREATE, hdr.FileInfo().Mode())
+		if err != nil {
+			return err
+		}
+
+		if err := dstFile.Truncate(0); err != nil {
+			return err
+		}
+
+		// Don't decompress non-regular files
+		if !hdr.FileInfo().Mode().IsRegular() {
+			if _, err := io.Copy(dstFile, tr); err != nil {
+				return err
+			}
+
+			return nil
+		}
+
+		decryptor, err := encryption.Decrypt(tr, pipes.Encryption, crypto.Identity)
+		if err != nil {
+			return err
+		}
+
+		decompressor, err := compression.Decompress(decryptor, pipes.Compression)
+		if err != nil {
+			return err
+		}
+
+		sig := ""
+		if hdr.PAXRecords != nil {
+			if s, ok := hdr.PAXRecords[pax.STFSRecordSignature]; ok {
+				sig = s
+			}
+		}
+
+		verifier, verify, err := signature.Verify(decompressor, isRegular, pipes.Signature, crypto.Recipient, sig)
+		if err != nil {
+			return err
+		}
+
+		if _, err := io.Copy(dstFile, verifier); err != nil {
+			return err
+		}
+
+		if err := verify(); err != nil {
+			return err
+		}
+
+		if err := decryptor.Close(); err != nil {
+			return err
+		}
+
+		if err := decompressor.Close(); err != nil {
+			return err
+		}
+
+		if err := dstFile.Close(); err != nil {
+			return err
+		}
+	}
+
 	return nil
 }