openpgp: Verify messages using the Cleartext Signature Framework.

  - Implement verification of messages using the Cleartext Signature
    Framework by detecting them in the armor reader, and transforming
    them on the fly to inline signed messages.

  - The transformation is not perfect.  We need to synthesize
    one-pass-signatures, but we only know the hash algorithm(s) used.
    Luckily, this is the only information the packet parser needs.

  - We only enable the transformation when using stream::Verifier.
    The transformation is transparent to the caller.  Currently, there
    is no way to disable this.  In the next major revision, we may add
    ways to control this behavior.

  - Fixes #151.

3 files changed, 133 insertions, 0 deletions

diff --git a/openpgp/tests/data/messages/a-cypherpunks-manifesto.txt.cleartext.sig b/openpgp/tests/data/messages/a-cypherpunks-manifesto.txt.cleartext.sig
new file mode 100644
index 00000000..b709f571
--- /dev/null
+++ b/openpgp/tests/data/messages/a-cypherpunks-manifesto.txt.cleartext.sig
@@ -0,0 +1,109 @@
+-----BEGIN PGP SIGNED MESSAGE-----
+Hash: SHA256
+
+A Cypherpunk's Manifesto
+by Eric Hughes
+
+Privacy is necessary for an open society in the electronic
+age. Privacy is not secrecy. A private matter is something one doesn't
+want the whole world to know, but a secret matter is something one
+doesn't want anybody to know. Privacy is the power to selectively
+reveal oneself to the world.
+
+If two parties have some sort of dealings, then each has a memory of
+their interaction. Each party can speak about their own memory of
+this; how could anyone prevent it? One could pass laws against it, but
+the freedom of speech, even more than privacy, is fundamental to an
+open society; we seek not to restrict any speech at all. If many
+parties speak together in the same forum, each can speak to all the
+others and aggregate together knowledge about individuals and other
+parties. The power of electronic communications has enabled such group
+speech, and it will not go away merely because we might want it to.
+
+Since we desire privacy, we must ensure that each party to a
+transaction have knowledge only of that which is directly necessary
+for that transaction. Since any information can be spoken of, we must
+ensure that we reveal as little as possible. In most cases personal
+identity is not salient. When I purchase a magazine at a store and
+hand cash to the clerk, there is no need to know who I am. When I ask
+my electronic mail provider to send and receive messages, my provider
+need not know to whom I am speaking or what I am saying or what others
+are saying to me; my provider only need know how to get the message
+there and how much I owe them in fees. When my identity is revealed by
+the underlying mechanism of the transaction, I have no privacy. I
+cannot here selectively reveal myself; I must always reveal myself.
+
+Therefore, privacy in an open society requires anonymous transaction
+systems. Until now, cash has been the primary such system. An
+anonymous transaction system is not a secret transaction system. An
+anonymous system empowers individuals to reveal their identity when
+desired and only when desired; this is the essence of privacy.
+
+Privacy in an open society also requires cryptography. If I say
+something, I want it heard only by those for whom I intend it. If the
+content of my speech is available to the world, I have no privacy. To
+encrypt is to indicate the desire for privacy, and to encrypt with
+weak cryptography is to indicate not too much desire for
+privacy. Furthermore, to reveal one's identity with assurance when the
+default is anonymity requires the cryptographic signature.
+
+We cannot expect governments, corporations, or other large, faceless
+organizations to grant us privacy out of their beneficence. It is to
+their advantage to speak of us, and we should expect that they will
+speak. To try to prevent their speech is to fight against the
+realities of information. Information does not just want to be free,
+it longs to be free. Information expands to fill the available storage
+space. Information is Rumor's younger, stronger cousin; Information is
+fleeter of foot, has more eyes, knows more, and understands less than
+Rumor.
+
+We must defend our own privacy if we expect to have any. We must come
+together and create systems which allow anonymous transactions to take
+place. People have been defending their own privacy for centuries with
+whispers, darkness, envelopes, closed doors, secret handshakes, and
+couriers. The technologies of the past did not allow for strong
+privacy, but electronic technologies do.
+
+We the Cypherpunks are dedicated to building anonymous systems. We are
+defending our privacy with cryptography, with anonymous mail
+forwarding systems, with digital signatures, and with electronic
+money.
+
+Cypherpunks write code. We know that someone has to write software to
+defend privacy, and since we can't get privacy unless we all do, we're
+going to write it. We publish our code so that our fellow Cypherpunks
+may practice and play with it. Our code is free for all to use,
+worldwide. We don't much care if you don't approve of the software we
+write. We know that software can't be destroyed and that a widely
+dispersed system can't be shut down.
+
+Cypherpunks deplore regulations on cryptography, for encryption is
+fundamentally a private act. The act of encryption, in fact, removes
+information from the public realm. Even laws against cryptography
+reach only so far as a nation's border and the arm of its
+violence. Cryptography will ineluctably spread over the whole globe,
+and with it the anonymous transactions systems that it makes possible.
+
+For privacy to be widespread it must be part of a social
+contract. People must come and together deploy these systems for the
+common good. Privacy only extends so far as the cooperation of one's
+fellows in society. We the Cypherpunks seek your questions and your
+concerns and hope we may engage you so that we do not deceive
+ourselves. We will not, however, be moved out of our course because
+some may disagree with our goals.
+
+The Cypherpunks are actively engaged in making the networks safer for
+privacy. Let us proceed together apace.
+
+Onward.
+
+Eric Hughes <hughes@soda.berkeley.edu>
+
+9 March 1993 
+-----BEGIN PGP SIGNATURE-----
+
+iHUEARYIAB0WIQQ50QCrZ9W9jAQBAgX7N1HxWH2u8QUCYCabqgAKCRD7N1HxWH2u
+8Wt0AP9LgduU7UPE+sYJaE/7TjUcHcHrkBy2zviCXVp2H+yRYwD+IGVDAJ3fD+1F
+S4n1oYb+QK1HpBSpgGEwwggKQ2iqtAo=
+=F/g5
+-----END PGP SIGNATURE-----
diff --git a/openpgp/tests/data/messages/a-problematic-poem.txt b/openpgp/tests/data/messages/a-problematic-poem.txt
new file mode 100644
index 00000000..9709619b
--- /dev/null
+++ b/openpgp/tests/data/messages/a-problematic-poem.txt
@@ -0,0 +1,7 @@
+This is a poem about a great escape.
+
+From the depths of the underworld, a monster roared in the morning.
+The villagers were wary, for they have all heard the awful stories
+-told by their parents when they were very young.
+
+-- Unknown Artist
diff --git a/openpgp/tests/data/messages/a-problematic-poem.txt.cleartext.sig b/openpgp/tests/data/messages/a-problematic-poem.txt.cleartext.sig
new file mode 100644
index 00000000..c2e72594
--- /dev/null
+++ b/openpgp/tests/data/messages/a-problematic-poem.txt.cleartext.sig
@@ -0,0 +1,17 @@
+-----BEGIN PGP SIGNED MESSAGE-----
+Hash: SHA256
+
+This is a poem about a great escape.
+
+- From the depths of the underworld, a monster roared in the morning.
+The villagers were wary, for they have all heard the awful stories
+- -told by their parents when they were very young.
+
+- -- Unknown Artist
+-----BEGIN PGP SIGNATURE-----
+
+iHUEARYIAB0WIQQ50QCrZ9W9jAQBAgX7N1HxWH2u8QUCYCad2gAKCRD7N1HxWH2u
+8Vs+AP4iITZS0BxoCeJbyUHMcArrZbte9msAndEO9clJG5wpCAEA2e7FSZ/GaAzq
+X5YLqccgcod6K94lAMGzkFgerOSHpA8=
+=0W4n
+-----END PGP SIGNATURE-----