buffered-reader: Fix returning partial reads ending in errors.

  - Make sure that we return the data we already have in our buffer,
    even though we encountered an IO error while filling it.

  - Notably, the packet parser assumes that data once read can be
    requested through the buffered reader protocol again and again.
    Unfortunately, that was not the case, leading to a panic.

  - As the generic reader is used to implement the buffered reader
    protocol on top of io::Read, this problem affects among other
    things the compression container.  Demonstrate this using test.

  - Fixes #1005.

1 files changed, 28 insertions, 0 deletions

diff --git a/openpgp/src/parse.rs b/openpgp/src/parse.rs
index d8b4fd07..d414cbe4 100644
--- a/openpgp/src/parse.rs
+++ b/openpgp/src/parse.rs
@@ -6463,4 +6463,32 @@ mod test {
 
         Ok(())
     }
+
+    /// Tests for a panic in the packet parser.
+    fn parse_message(message: &str) {
+        eprintln!("parsing {:?}", message);
+        let mut ppr = match PacketParser::from_bytes(message) {
+            Ok(ppr) => ppr,
+            Err(_) => return,
+        };
+        while let PacketParserResult::Some(pp) = ppr {
+            dbg!(&pp.packet);
+            if let Ok((_, tmp)) = pp.recurse() {
+                ppr = tmp;
+            } else {
+                break;
+            }
+        }
+    }
+
+    /// Tests issue 1005.
+    #[test]
+    fn panic_on_short_zip() {
+        parse_message("-----BEGIN PGP SIGNATURE-----
+
+owGjAA0=
+zXvj
+-----END PGP SIGNATURE-----
+");
+    }
 }