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// Copyright 2021 Northern.tech AS
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package awriter
import (
"archive/tar"
"io"
"github.com/pkg/errors"
"github.com/mendersoftware/mender-artifact/artifact"
)
var ErrAlreadyExistingSignature = errors.New(
"The Artifact is already signed, will not overwrite existing signature",
)
var ErrManifestNotFound = errors.New("`manifest` not found. Corrupt Artifact?")
// Special fast-track to just sign, nothing else. This skips all the expensive
// and complicated repacking, and simply adds the manifest.sig file.
func SignExisting(src io.Reader, dst io.Writer, key artifact.Signer, overwrite bool) error {
var foundManifest bool
rTar := tar.NewReader(src)
wTar := tar.NewWriter(dst)
for {
header, err := rTar.Next()
if err == io.EOF {
break
} else if err != nil {
return errors.Wrap(err, "Could not read tar header")
}
switch header.Name {
case "manifest":
err = signManifestAndOutputSignature(header, rTar, wTar, key)
if err != nil {
return err
}
foundManifest = true
continue
case "manifest.sig":
if overwrite {
continue
} else {
return ErrAlreadyExistingSignature
}
}
err = wTar.WriteHeader(header)
if err != nil {
return errors.Wrap(err, "Could not write tar header")
}
_, err = io.Copy(wTar, rTar)
if err != nil {
return errors.Wrap(err, "Failed to copy tar body")
}
}
err := wTar.Close()
if err != nil {
return errors.Wrap(err, "Could not finalize tar archive")
}
if !foundManifest {
return ErrManifestNotFound
}
return nil
}
func signManifestAndOutputSignature(
header *tar.Header,
src *tar.Reader,
dst *tar.Writer,
key artifact.Signer,
) error {
buf := make([]byte, header.Size)
read, err := src.Read(buf)
if err != nil && err != io.EOF {
return errors.Wrap(err, "Could not read manifest")
} else if int64(read) != header.Size {
return errors.New("Unexpected mismatch between header size and read size")
}
err = dst.WriteHeader(header)
if err != nil {
return errors.Wrap(err, "Could not write manifest header")
}
written, err := dst.Write(buf)
if err != nil {
return errors.Wrap(err, "Could not write manifest")
} else if written != read {
return errors.New("Could not write entire manifest")
}
signedBuf, err := key.Sign(buf)
if err != nil {
return errors.Wrap(err, "Could not sign manifest")
}
signedHeader := &tar.Header{
Name: "manifest.sig",
Size: int64(len(signedBuf)),
Mode: 0644,
}
err = dst.WriteHeader(signedHeader)
if err != nil {
return errors.Wrap(err, "Could not write signature header")
}
written, err = dst.Write(signedBuf)
if err != nil {
return errors.Wrap(err, "Could not write signature")
} else if written != len(signedBuf) {
return errors.New("Could not write entire manifest.sig")
}
read, err = src.Read(buf)
if err != io.EOF || read != 0 {
return errors.New("File bigger than its header size")
}
return nil
}
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