openpgp: Add support for OnePassSig packets.

  - Handling OnePassSig packets in an unbuffered manner introduces a
    layering violation: when we encounter a OnePassSig packet, we want
    to push a HashedReader on the BufferedReader stack, but that is
    popped when the readers associated with the OnePassSig are popped!
    Thus, we need to introduce a bit of ugliness (OnePassSig::parse
    needs to pop its readers and then push the HashedReader at the
    high level).  This is unfortunate, but it appears to be necessary.

  - Hashing literal data packets is ugly!  Only the content of a
    literal data packet is hashed; neither the packet's headers, the
    packet's meta-data nor the length information is included in the
    hash.  This, in particular, adds some ugliness to the
    BufferedReaderPartialBodyFilter implementation: it needs to
    disable hashing when decoding a literal data packet.

  - This implementation has several limitations:

    - We only handle a single level of Signature nesting.  That is, we
      don't support things like having two OnePassSig packets, both of
      which have their 'last' bit set (meaning that the outer
      signature is over the inner Signature and the content, not just
      the content).  If the parser encounters such a message, it
      silently ignores the nesting.  In practice, this functionality
      is rarely used: GnuPG neither produces such messages nor does it
      correctly handle them.

    - Each OnePassSig packet pushes another HashedReader on the
      BufferedReader stack.  This can cause a stack overflow if there
      are too many OnePassSig packets.  Instead, there should only be
      a single HashedReader per level of nesting, and the amount of
      nesting must be limited.

    - If there are multiple OnePassSig packets at a nesting level
      using the same hash algorithm, we don't reuse hashes, because
      Nettle doesn't currently support cloning hashes.

3 files changed, 0 insertions, 0 deletions

diff --git a/openpgp/tests/data/messages/signed-1.gpg b/openpgp/tests/data/messages/signed-1.gpg
new file mode 100644
index 00000000..9728be18
--- /dev/null
+++ b/openpgp/tests/data/messages/signed-1.gpg
diff --git a/openpgp/tests/data/messages/signed-2-partial-body.gpg b/openpgp/tests/data/messages/signed-2-partial-body.gpg
new file mode 100644
index 00000000..06aa84be
--- /dev/null
+++ b/openpgp/tests/data/messages/signed-2-partial-body.gpg
diff --git a/openpgp/tests/data/messages/signed-3-partial-body-multiple-sigs.gpg b/openpgp/tests/data/messages/signed-3-partial-body-multiple-sigs.gpg
new file mode 100644
index 00000000..e3df57f8
--- /dev/null
+++ b/openpgp/tests/data/messages/signed-3-partial-body-multiple-sigs.gpg