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package cryptoutil
import (
"bytes"
"errors"
"io"
"strings"
"git.sr.ht/~rjarry/aerc/app"
"git.sr.ht/~rjarry/aerc/lib/rfc822"
"github.com/emersion/go-message/mail"
)
func Cleartext(r io.Reader, header mail.Header) ([]byte, error) {
msg, err := app.CryptoProvider().Decrypt(
rfc822.NewCRLFReader(r), app.DecryptKeys)
if err != nil {
return nil, errors.New("decrypt error")
}
full, err := createMessage(header, msg.Body)
if err != nil {
return nil, errors.New("failed to create decrypted message")
}
return full, nil
}
func createMessage(header mail.Header, body io.Reader) ([]byte, error) {
e, err := rfc822.ReadMessage(body)
if err != nil {
return nil, err
}
// copy the header values from the "decrypted body". This should set
// the correct content type.
hf := e.Header.Fields()
for hf.Next() {
header.Set(hf.Key(), hf.Value())
}
ctype, params, err := header.ContentType()
if err != nil {
return nil, err
}
// in case there remains a multipart/{encrypted,signed} content type,
// manually correct them to multipart/mixed as a fallback.
ct := strings.ToLower(ctype)
if strings.Contains(ct, "multipart/encrypted") ||
strings.Contains(ct, "multipart/signed") {
delete(params, "protocol")
delete(params, "micalg")
header.SetContentType("multipart/mixed", params)
}
// a SingleInlineWriter is sufficient since the "decrypted body"
// already contains the proper boundaries of the parts; we just want to
// combine it with the headers.
var message bytes.Buffer
w, err := mail.CreateSingleInlineWriter(&message, header)
if err != nil {
return nil, err
}
if _, err := io.Copy(w, e.Body); err != nil {
return nil, err
}
w.Close()
return message.Bytes(), nil
}
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