openpgp: Fix std::hash::Hash for Signature4.

  - If we PartialEq over a subset of fields, we cannot derive Hash,
    because we must only hash the same subset of fields.

1 files changed, 13 insertions, 1 deletions

diff --git a/openpgp/src/packet/signature/mod.rs b/openpgp/src/packet/signature/mod.rs
index 347b8d38..902e95e4 100644
--- a/openpgp/src/packet/signature/mod.rs
+++ b/openpgp/src/packet/signature/mod.rs
@@ -269,7 +269,7 @@ impl<'a> From<&'a Signature4> for &'a Builder {
 ///
 ///   [Section 5.2 of RFC 4880]: https://tools.ietf.org/html/rfc4880#section-5.2
 // Note: we can't derive PartialEq, because it includes the cached data.
-#[derive(Eq, Hash, Clone)]
+#[derive(Eq, Clone)]
 pub struct Signature4 {
     /// CTB packet header fields.
     pub(crate) common: packet::Common,
@@ -358,6 +358,18 @@ impl PartialEq for Signature4 {
     }
 }
 
+impl std::hash::Hash for Signature4 {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        use std::hash::Hash as StdHash;
+        self.fields.version.hash(state);
+        self.fields.sigtype.hash(state);
+        self.fields.pk_algo.hash(state);
+        self.fields.hash_algo.hash(state);
+        self.fields.hashed_area.hash(state);
+        StdHash::hash(&self.mpis, state);
+    }
+}
+
 impl Signature4 {
     /// Creates a new signature packet.
     ///