openpgp: Explicitly implement Eq and Hash if PartialEq is.

  - If we don't derive PartialEq, then deriving hash is unsafe.

  - See #92.

2 files changed, 26 insertions, 3 deletions

diff --git a/openpgp/src/crypto/mem.rs b/openpgp/src/crypto/mem.rs
index a67cf993..4dfe5457 100644
--- a/openpgp/src/crypto/mem.rs
+++ b/openpgp/src/crypto/mem.rs
@@ -2,6 +2,7 @@
 
 use std::cmp::{min, Ordering};
 use std::fmt;
+use std::hash::{Hash, Hasher};
 use std::ops::{Deref, DerefMut};
 use std::pin::Pin;
 
@@ -11,7 +12,7 @@ use memsec;
 ///
 /// The memory is guaranteed not to be copied around, and is cleared
 /// when the object is dropped.
-#[derive(Clone, Eq, Hash)]
+#[derive(Clone)]
 pub struct Protected(Pin<Box<[u8]>>);
 
 impl PartialEq for Protected {
@@ -20,6 +21,14 @@ impl PartialEq for Protected {
     }
 }
 
+impl Eq for Protected {}
+
+impl Hash for Protected {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.0.hash(state);
+    }
+}
+
 impl Protected {
     /// Converts to a buffer for modification.
     pub unsafe fn into_vec(self) -> Vec<u8> {
diff --git a/openpgp/src/crypto/mpis.rs b/openpgp/src/crypto/mpis.rs
index 37f75213..4460cc58 100644
--- a/openpgp/src/crypto/mpis.rs
+++ b/openpgp/src/crypto/mpis.rs
@@ -20,7 +20,7 @@ use crate::Error;
 use crate::Result;
 
 /// Holds a single MPI.
-#[derive(Clone, Hash)]
+#[derive(Clone)]
 pub struct MPI {
     /// Integer value as big-endian.
     value: Box<[u8]>,
@@ -216,10 +216,16 @@ impl PartialEq for MPI {
 
 impl Eq for MPI {}
 
+impl std::hash::Hash for MPI {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.value.hash(state);
+    }
+}
+
 /// Holds a single MPI containing secrets.
 ///
 /// The memory will be cleared when the object is dropped.
-#[derive(Clone, Hash)]
+#[derive(Clone)]
 pub struct ProtectedMPI {
     /// Integer value as big-endian.
     value: Protected,
@@ -245,6 +251,12 @@ impl From<MPI> for ProtectedMPI {
     }
 }
 
+impl std::hash::Hash for ProtectedMPI {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.value.hash(state);
+    }
+}
+
 impl ProtectedMPI {
     /// Returns the length of the MPI in bits.
     pub fn bits(&self) -> usize {
@@ -481,6 +493,8 @@ impl Arbitrary for PublicKey {
 ///
 /// Provides a typed and structured way of storing multiple MPIs in
 /// packets.
+// Deriving Hash here is okay: PartialEq is manually implemented to
+// ensure that secrets are compared in constant-time.
 #[derive(Clone, Hash)]
 pub enum SecretKeyMaterial {
     /// RSA secret key.