ffi: Avoid NULL pointer dereference.

  - The callback can fail to return the secret.  Fail gracefully.

2 files changed, 11 insertions, 0 deletions

diff --git a/ffi/src/error.rs b/ffi/src/error.rs
index 75fa4f3e..96a64c96 100644
--- a/ffi/src/error.rs
+++ b/ffi/src/error.rs
@@ -86,6 +86,9 @@ pub enum Status {
     /// Invalid session key.
     InvalidSessionKey = -12,
 
+    /// Missing session key.
+    MissingSessionKey = -27,
+
     /// Malformed TPK.
     MalformedTPK = -13,
 
@@ -119,6 +122,7 @@ pub enum Status {
 
     // XXX: Skipping ManipulatedMessage = -25
     // XXX: Skipping UnsupportedAEADAlgorithm = -26
+    // XXX: Skipping MissingSessionKey = -27
 }
 
 impl<'a> From<&'a failure::Error> for Status {
@@ -156,6 +160,8 @@ impl<'a> From<&'a failure::Error> for Status {
                     Status::InvalidPassword,
                 &openpgp::Error::InvalidSessionKey(_) =>
                     Status::InvalidSessionKey,
+                &openpgp::Error::MissingSessionKey(_) =>
+                    Status::MissingSessionKey,
                 &openpgp::Error::MalformedMPI(_) =>
                     Status::MalformedMPI,
                 &openpgp::Error::BadSignature(_) =>
diff --git a/ffi/src/openpgp.rs b/ffi/src/openpgp.rs
index d772f2ef..cd158d85 100644
--- a/ffi/src/openpgp.rs
+++ b/ffi/src/openpgp.rs
@@ -2517,6 +2517,11 @@ impl DecryptionHelper for DHelper {
                 format!("{:?}", result)).into());
         }
 
+        if secret.is_null() {
+            return Err(openpgp::Error::MissingSessionKey(
+                "Callback did not return a session key".into()).into());
+        }
+
         let secret = unsafe {
             Box::from_raw(secret)
         };