openpgp: Only impl Serialize for objects that are normally exported.

  - Add two new traits: `Marshal` and `MarshalInto`.

  - Implement them instead of `Serialize` and `SerializeInto`.

  - Only implement `Serialize` and `SerializeInto` for data structures
    that are normally exported.

  - This should prevent users from accidentally serializing a bare
    signature (`Signature`) when they meant to serialize a signature
    packet (`Packet`), for instance.

  - Fixes #368.

1 files changed, 4 insertions, 2 deletions

diff --git a/autocrypt/src/serialize.rs b/autocrypt/src/serialize.rs
index 0375c774..85979057 100644
--- a/autocrypt/src/serialize.rs
+++ b/autocrypt/src/serialize.rs
@@ -1,5 +1,5 @@
 use sequoia_openpgp as openpgp;
-use openpgp::serialize::Serialize;
+use openpgp::serialize::Marshal;
 
 use super::{
     AutocryptHeader,
@@ -7,7 +7,9 @@ use super::{
     Result,
 };
 
-impl Serialize for AutocryptHeader {
+impl openpgp::serialize::Serialize for AutocryptHeader {}
+
+impl Marshal for AutocryptHeader {
     fn serialize(&self, o: &mut dyn std::io::Write) -> Result<()> {
         if self.key.is_none() {
             return Err(Error::InvalidOperation("No key".into()).into());