openpgp: Fix crash in the packet parser.

  - The packet parser hashes packet bodies to provide a robust
    equality relation even when packet bodies are streamed.  To hash
    all bytes on the fly everywhere, we do that when it is consumed in
    PacketParser::consume.

  - This function assumes that if BufferedReader::data and friends
    returned n bytes, future calls to these interfaces will succeed if
    up to n bytes are requested, and no data was consumed in the
    meantime.

  - However, armor::Reader::data_helper did not provide that
    guarantee, making PacketParser::consume panic with the message "It
    is an error to consume more than data returns", which doesn't
    quite correctly name the problem at hand.

  - Fix this crash by fixing armor::Reader::data_helper in the same
    way the previous commit fixes
    buffered_reader::Generic::data_helper.

  - Fixes #957.

1 files changed, 11 insertions, 0 deletions

diff --git a/openpgp/src/parse.rs b/openpgp/src/parse.rs
index d414cbe4..2dc9fad5 100644
--- a/openpgp/src/parse.rs
+++ b/openpgp/src/parse.rs
@@ -6491,4 +6491,15 @@ zXvj
 -----END PGP SIGNATURE-----
 ");
     }
+
+    /// Tests issue 957.
+    #[test]
+    fn panic_on_malformed_armor() {
+        parse_message("-----BEGIN PGP MESSAGE-----
+
+heLBX8Pq0kUBwQz2iFAzRwOdgTBvH5KsDU9lmE
+
+-----END PGP MESSAGE-----
+");
+    }
 }