Fix code and add a test case. The old code passed on the original input
stream, which has already been consumed.

Bug: 570501
Change-Id: I81f60698ce42443df57e59b1d1ab155574136fa8
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Add detection for the key-value pair format that was available in
gpg-agent for some time already and that has become the default since
gpg-agent 2.2.20. If a secret key in the .gnupg/private-keys-v1.d
directory is found to have this format, extract the human-readable key
from it, convert it to the binary serialized form and hand that to
BouncyCastle.

Encrypted keys in the new format may use AES/OCB. OCB is a patent-
encumbered algorithm; although there is a license for open-source
software, that may not be good enough and OCB may not be available in
Java. It is not available in the default security provider in Java,
and it is also not available in the BouncyCastle version included in
Eclipse.

Implement AES/OCB decryption, throwing a PGPException with a nice
message if the algorithm is not available. Include a copy of the normal
s-expression parser of BouncyCastle and fix it to properly handle data
from such keys: such keys do not contain an internal hash since the
AES/OCB cipher includes and checks a MAC already.

Bug: 570501
Change-Id: Ifa6391a809a84cfc6ae7c6610af6a79204b4143b
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Otherwise client code has no way to ever create an instance without
using internal non-API.

Change-Id: I6201f98d4b1704a053159967b8adacd98e368522
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

The gpg-agent stores secret keys in individual files in the secret
key directory private-keys-v1.d. The files have the key's keygrip
(in upper case) as name and extension ".key".

A keygrip is a SHA1 hash over the parameters of the public key. By
computing this keygrip, we can pre-compute the expected file name and
then check only that one file instead of having to iterate over all
keys stored in that directory.

This file naming scheme is actually an implementation detail of
gpg-agent. It is unlikely to change, though. The keygrip itself is
computed via libgcrypt and will remain stable according to the GPG
main author.[1]

Add an implementation for calculating the keygrip and include tests.
Do not iterate over files in BouncyCastleGpgKeyLocator but only check
the single file identified by the keygrip.

Ideally upstream BouncyCastle would provide such a getKeyGrip() method.
But as it re-builds GPG and libgcrypt internals, it's doubtful it would
be included there, and since BouncyCastle even lacks a number of curve
OIDs for ed25519/curve25519 and uses the short-Weierstrass parameters
instead of the more common Montgomery parameters, including it there
might be quite a bit of work.

[1] http://gnupg.10057.n7.nabble.com/GnuPG-2-1-x-and-2-2-x-keyring-formats-tp54146p54154.html

Bug: 547536
Change-Id: I30022a0e7b33b1bf35aec1222f84591f0c30ddfd
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Add a GpgSignatureVerifier interface, plus a factory to create
instances thereof that is provided via the ServiceLoader mechanism.

Implement the new interface for BouncyCastle. A verifier maintains
an internal LRU cache of previously found public keys to speed up
verifying multiple objects (tag or commits). Mergetags are not handled.

Provide a new VerifySignatureCommand in org.eclipse.jgit.api together
with a factory method Git.verifySignature(). The command can verify
signatures on tags or commits, and can be limited to accept only tags
or commits. Provide a new public WrongObjectTypeException thrown when
the command is limited to either tags or commits and a name resolves
to some other object kind.

In jgit.pgm, implement "git tag -v", "git log --show-signature", and
"git show --show-signature". The output is similar to command-line
gpg invoked via git, but not identical. In particular, lines are not
prefixed by "gpg:" but by "bc:".

Trust levels for public keys are read from the keys' trust packets,
not from GPG's internal trust database. A trust packet may or may
not be set. Command-line GPG produces more warning lines depending
on the trust level, warning about keys with a trust level below
"full".

There are no unit tests because JGit still doesn't have any setup to
do signing unit tests; this would require at least a faked .gpg
directory with pre-created key rings and keys, and a way to make the
BouncyCastle classes use that directory instead of the default. See
bug 547538 and also bug 544847.

Tested manually with a small test repository containing signed and
unsigned commits and tags, with signatures made with different keys
and made by command-line git using GPG 2.2.25 and by JGit using
BouncyCastle 1.65.

Bug: 547751
Change-Id: If7e34aeed6ca6636a92bf774d893d98f6d459181
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Add it to the GpgConfig. Change GpgConfig to load the values once only.
Add a parameter to the GpgObjectSigner interface's operations to pass
in a GpgConfig. Update CommitCommand and TagCommand to pass the value
to the signer. Let the signer decide whether it can actually produce
the wanted signature type (openpgp or x509).

No behavior change. But this makes it possible to implement different
signers that might support x509 signatures, or use gpg.program and
shell out to an external GPG executable for signing.

Change-Id: I427f83eb1ece81c310e1cddd85315f6f88cc99ea
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Although not mentioned in the GPG documentation at [1], GPG uses
case-insensitive matching also for the '<' (exact e-mail) and '@'
(partial e-mail) operators. Matching for '=' (full exact match) is
case-sensitive. Compare [2].

[1] https://www.gnupg.org/documentation/manuals/gnupg/Specify-a-User-ID.html
[2] https://dev.gnupg.org/source/gnupg/browse/master/g10/keyring.c;22f7dddc34446a8c3e9eddf6cb281f16802351d7$890

Bug: 547789
Change-Id: I2f5ab65807d5dde3aa00ff032894701bbd8418c9
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Factor out a common ObjectBuilder as super class of CommitBuilder
and TagBuilder, and make the GpgSigner work on ObjectBuilder.

In order not to break API, add the new method for signing an
ObjectBuilder in a new interface GpgObjectSigner.

The signature for a tag is just tacked onto the end of the tag
message. The message of a signed tag must end in LF.

Bug: 386908
Change-Id: I5e021e3c927f4051825cd7355b129113b949455e
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Signing a commit with command line git and gpg 2.2.20 includes the
e-mail part of the key's user ID as a "Signer's User ID" subpacket
on the signature.

Implement this for signing via Bouncy Castle.

Bug: 564386
Change-Id: I68906b895349359596cf3451d65f2840c60df856
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

BouncyCastle supports reading GPG keys without passphrase since 1.62.
Handle this in JGit, too, and don't prompt for a passphrase unless
it's necessary.

Make two passes over the private key files, a first pass without
passphrase provider. If that succeeds it has managed to read a
matching key without passphrase. Otherwise, ask the user for
the passphrase and make a second pass over the key files.

BouncyCastle 1.65 still has no method to get the GPG "key grip" from
a given public key, so JGit still cannot determine the correct file
to read up front. (The file name is the key grip as 40 hex digits,
upper case, with extension ".key").

Bug: 548763
Change-Id: I448181276548c08716d913c7ba1b4bc64c62f952
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Motivation: BouncyCastle serves as 'default' implementation of
the GPG Signer. If a client application does not use it there is no need
to pull in this dependency, especially since BouncyCastle is a large
library.

Move the classes depending on BouncyCastle to an OSGi fragment extending
the org.eclipse.jgit bundle. They are moved to a distinct internal
package in order to avoid split packages. This doesn't break public API
since these classes were already in an internal package before this
change.

Add a new feature org.eclipse.jgit.gpg.bc to enable installation. With
that users can now decide if they want to install it.

Attempts to sign a commit if org.eclipse.jgit.gpg.bc isn't available
will result in ServiceUnavailableException being thrown.

Bug: 559106
Change-Id: I42fd6c00002e17aa9a7be96ae434b538ea86ccf8
Also-by: Michael Dardis <git@md-5.net>
Signed-off-by: Michael Dardis <git@md-5.net>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: David Ostrovsky <david@ostrovsky.org>