For RSA keys, there may be several configured signature algorithms:
rsa-sha2-512, rsa-sha2-256, and ssh-rsa. Upstream sshd has bug
SSHD-1105 [1] and always and unconditionally uses only the first
configured algorithm. With the default order, this means that it cannot
connect to a server that knows only ssh-rsa, like for instance Apache
MINA sshd servers older than 2.6.0.

This affects for instance bitbucket.org or also AWS Code Commit.

Re-introduce our own pubkey authenticator that fixes this.

Note that a server may impose a penalty (back-off delay) for subsequent
authentication attempts with signature algorithms unknown to the server.
In such cases, users can re-order the signature algorithm list via the
PubkeyAcceptedAlgorithms (formerly PubkeyAcceptedKeyTypes) ssh config.

[1] https://issues.apache.org/jira/browse/SSHD-1105

Bug: 572056
Change-Id: I7fb9c759ab6532e5f3b6524e9084085ddb2f30d6
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Apache MINA sshd 2.6.0 appears to use only the first appropriate
public key signature algorithm for a particular key. See [1]. For
RSA keys, that is rsa-sha2-512. This breaks authentication at servers
that only know the older (and deprecated) ssh-rsa algorithm.

With PubkeyAcceptedAlgorithms, users can re-order algorithms in
the ssh config file per host, if needed. Setting

  PubkeyAcceptedAlgorithms ^ssh-rsa

will put "ssh-rsa" at the front of the list of algorithms, and then
authentication at such servers with RSA keys works again.

[1] https://issues.apache.org/jira/browse/SSHD-1105

Bug: 572056
Change-Id: I86c3b93f05960c68936e80642965815926bb2532
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Re-enable DSA, DSA_CERT, and RSA_CERT public key authentication.
DSA is discouraged for a long time already, but it might still be
way too disruptive to completely drop it. RSA is discouraged for
far less long, and dropping that would be really disruptive.

Adapt to the changed property handling. Remove work-arounds for
shortcomings of earlier sshd versions.

Use Orbit I20210203173513, which includes sshd 2.6.0. This also bumps
apache.httpclient to 4.5.13 and apache.httpcore to 4.4.14.

Change-Id: I2d24a1ce4cc9f616a94bb5c4bdaedbf20dc6638e
Signed-off-by: David Ostrovsky <david@ostrovsky.org>
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Make all transports request protocol V2 when fetching. Depending on
the transport, set the GIT_PROTOCOL environment variable (file and
ssh), pass the Git-Protocol header (http), or set the hidden
"\0version=2\0" (git anon). We'll fall back to V0 if the server
doesn't reply with a version 2 answer.

A user can control which protocol the client requests via the git
config protocol.version; if not set, JGit requests protocol V2 for
fetching. Pushing always uses protocol V0 still.

In the API, there is only a new Transport.openFetch() version that
takes a collection of RefSpecs plus additional patterns to construct
the Ref prefixes for the "ls-refs" command in protocol V2. If none
are given, the server will still advertise all refs, even in protocol
V2.

BasePackConnection.readAdvertisedRefs() handles falling back to
protocol V0. It newly returns true if V0 was used and the advertised
refs were read, and false if V2 is used and an explicit "ls-refs" is
needed. (This can't be done transparently inside readAdvertisedRefs()
because a "stateless RPC" transport like TransportHttp may need to
open a new connection for writing.)

BasePackFetchConnection implements the changes needed for the protocol
V2 "fetch" command (stateless protocol, simplified ACK handling,
delimiters, section headers).

In TransportHttp, change readSmartHeaders() to also recognize the
"version 2" packet line as a valid smart server indication.

Adapt tests, and run all the HTTP tests not only with both HTTP
connection factories (JDK and Apache HttpClient) but also with both
protocol V0 and V2. The SSH tests are much slower and much more
focused on the SSH protocol and SSH key handling. Factor out two
very simple cloning and pulling tests and make those run with
protocol V2.

Bug: 553083
Change-Id: I357c7f5daa7efb2872f1c64ee6f6d54229031ae1
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Change-Id: Id78f4fd7d11a8908f41160a2ab9f3d81b7f771da
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This reverts commit f802f06e7f.

I had misunderstood how protocol V2 works. This implementation only
works if the negotiation during fetch is done in one round.

Fixing this is substantial work in BasePackFetchConnection. Basically
I think I'd have to change back negotiate to the V0 version, and have
a doFetch() that does

  if protocol V2
    doFetchV2()
  else
    doFetchV0()

with doFetchV0 the old code, and doFetchV2 completely new.

Plus there would need to be a HTTP test case requiring several
negotiation rounds.

This is a couple of days work at least, and I don't know when I will
have the time to revisit this. So although the rest of the code is
fine I prefer to back this out completely and not leave a only half
working implementation in the code for an indeterminate time.

Bug: 553083
Change-Id: Icbbbb09882b3b83f9897deac4a06d5f8dc99d84e
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Make all transports request protocol V2 when fetching. Depending on
the transport, set the GIT_PROTOCOL environment variable (file and
ssh), pass the Git-Protocol header (http), or set the hidden
"\0version=2\0" (git anon). We'll fall back to V0 if the server
doesn't reply with a version 2 answer.

A user can control which protocol the client requests via the git
config protocol.version; if not set, JGit requests protocol V2 for
fetching. Pushing always uses protocol V0 still.

In the API, there is only a new Transport.openFetch() version that
takes a collection of RefSpecs plus additional patterns to construct
the Ref prefixes for the "ls-refs" command in protocol V2. If none
are given, the server will still advertise all refs, even in protocol
V2.

BasePackConnection.readAdvertisedRefs() handles falling back to
protocol V0. It newly returns true if V0 was used and the advertised
refs were read, and false if V2 is used and an explicit "ls-refs" is
needed. (This can't be done transparently inside readAdvertisedRefs()
because a "stateless RPC" transport like TransportHttp may need to
open a new connection for writing.)

BasePackFetchConnection implements the changes needed for the protocol
V2 "fetch" command (simplified ACK handling, delimiters, section
headers).

In TransportHttp, change readSmartHeaders() to also recognize the
"version 2" packet line as a valid smart server indication.

Adapt tests, and run all the HTTP tests not only with both HTTP
connection factories (JDK and Apache HttpClient) but also with both
protocol V0 and V2. Do the same for the SSH transport tests.

Bug: 553083
Change-Id: Ice9866aa78020f5ca8f397cde84dc224bf5d41b4
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This is useful to access git repositories behind a bastion server
(jump host).

Add a constant for the config; rewrite the whole connection initiation
to parse the value and (recursively) set up the chain of hops. Add
tests for a single hop and two different ways to configure a two-hop
chain.

The connection timeout applies to each hop in the chain individually.

Change-Id: Idd25af95aa2ec5367404587e4e530b0663c03665
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

When exceptions occur very early in the SSH connection setup, it's
possible that an exception gets lost. A subsequent authentication
attempt may then never be notified of the failure, and then wait
indefinitely or until its timeout expires.

This is caused by race conditions in sshd. The issue has been reported
upstream as SSHD-1050,[1] but will be fixed at the earliest in sshd
2.6.0.

[1] https://issues.apache.org/jira/projects/SSHD/issues/SSHD-1050

Bug: 565394
Change-Id: If9b62839db38f9e59a5e1137c2257039ba82de98
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Improve the SshTestGitServer API for accessing the server properties.
Instead of returning the raw property map, return the proper sshd API
abstraction PropertyResolver.

This makes the interface more resilient against upstream changes.

Change-Id: Ie5b685bddc4e59f3eb6c121026d3658d57618ca4
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Change-Id: Ibb0bf0b1895a07a80a1f73d2fd6df2cb2d09fd77
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

SSHD-1028:[1] server doesn't close server-side sessions properly when
client disconnects.

[1] https://issues.apache.org/jira/projects/SSHD/issues/SSHD-1028

Change-Id: I0d67f49e35abe8375cb1370a494dc01d0fb2c9b1
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Motivation: JSch serves as 'default' implementations of the SSH
transport. If a client application does not use it then there is no need
to pull in this dependency.

Move the classes depending on JSch to an OSGi fragment extending the
org.eclipse.jgit bundle and keep them in the same package as before
since moving them to another package would break API. Defer moving them
to a separate package to the next major release.

Add a new feature org.eclipse.jgit.ssh.jsch feature to enable
installation. With that users can now decide which of the ssh client
integrations (JCraft JSch or Apache Mina SSHD) they want to install.
We will remove the JCraft JSch integration in a later step due to the
reasons discussed in bug 520927.

Bug: 553625
Change-Id: I5979c8a9dbbe878a2e8ac0fbfde7230059d74dc2
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>

Avoid using a key written to a file. This makes it clearer that
the test does not rely on files being present.

Change-Id: I31cf4f404aab5b891c32fc4bda906b7f8fe03777
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

A builder API provides a more convenient way to define a customized
SshdSessionFactory by hiding the subclassing.

Also provide a new interface SshConfigStore to abstract away the
specifics of reading a ssh config file, and provide a way to customize
the concrete ssh config implementation to be used. This facilitates
using an alternate ssh config implementation that may or may not be
based on files.

Change-Id: Ib9038e8ff2a4eb3a9ce7b3554d1450befec8e1e1
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

This is the format given by the Eclipse legal doc generator [1].

[1] https://www.eclipse.org/projects/tools/documentation.php?id=technology.jgit

Bug: 548298
Change-Id: I8d8cabc998ba1b083e3f0906a8d558d391ffb6c4
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Add the constant, and implement hashing of known host names in
OpenSshServerKeyDatabase. Add a test verifying that the hashing
works.

Bug: 548492
Change-Id: Iabe82b666da627bd7f4d82519a366d166aa9ddd4
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Provide a wrapper interface and change the implementation such that
a client can substitute its own database of known hosts keys instead
of the default file-based mechanism.

Bug: 547619
Change-Id: Ifc25a4519fa5bcf7bb8541b9f3e2de15215e3d66
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

RFC 4253 section 4.2 allows an ssh server to send additional lines
before its server identification string. Apache MINA sshd enforces
for these lines the constraints specified for the server identification
line, too: no NUL characters and not longer than 255 characters. That
is too strict. RFC 4253 doesn't mandate this, and it also doesn't
make sense given the rationale for these lines in RFC 4253: a TCP
wrapper may not be aware of SSH restrictions, and may not adhere to
these constraints.

Be more lenient when parsing the server's protocol version. Allow
NULs and longer lines in the preamble, and also handle line endings
more leniently. Only enforce the restrictions for the actual server
identification line.

Bug: 545939
Change-Id: I75955e9d8a8daef7c04fc0f39539c2ee93514e1c
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Include the net.i2p.crypto.eddsa bundle via a hard dependency.

Add tests for dealing with ed25519 host keys and user key files.

Manual tests: fetching from git.eclipse.org with an ed25519 user key,
and pushing this change itself using the same ed25519 key.

Note that sshd 2.0.0 does not yet support encrypted ed25519 private
keys.

Bug: 541272
Change-Id: I7072f4014d9eca755b4a2412e19c086235e5eae9
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

This is not about the ssh config ProxyCommand but about programmatic
support for HTTP and SOCKS5 proxies. Eclipse allows the user to
specify such proxies, and JSch at least contains code to connect
through proxies. So our Apache MINA sshd client also should be able
to do this.

Add interfaces and provide two implementations for HTTP and SOCKS5
proxies. Adapt the core code to be able to deal with proxy connections
at all. The built-in client-side support for this in sshd 2.0.0 is
woefully inadequate.

Tested manually by running proxies and then fetching various real-
world repositories via these proxies from different servers. Proxies
tested: ssh -D (SOCKS, anonymous), tinyproxy (HTTP, anonymous), and
3proxy (SOCKS & HTTP, username-password authentication). The GSS-API
authentication is untested since I have no Kerberos setup.

Bug: 520927
Change-Id: I1a5c34687d439b3ef8373c5d58e24004f93e63ae
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Add a new ssh client implementation based on Apach MINA sshd 2.0.0.

This implementation uses JGit's own config file parser and host entry
resolver. Code inspection of the Apache MINA implementation revealed
a few bugs or idiosyncrasies that immediately would re-introduce bugs
already fixed in the past in JGit.

Apache MINA sshd is not without quirks either, and I had to configure
and override more than I had expected. But at least it was all doable
in clean ways.

Apache MINA boasts support for Bouncy Castle, so in theory this should
open the way to using more ssh key algorithms, such as ed25519.

The implementation is in a separate bundle and is still not used in
the core org.eclipse.jgit bundle. The tests re-use the ssh tests from
the core test bundle.

Bug: 520927
Change-Id: Ib35e73c35799140fe050d1ff4fb18d0d3596580e
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>