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>

If oldLine is null #updateModifiedServerKey shouldn't be called since it
would derefence it. Spotbugs raised this as problem
RCN_REDUNDANT_NULLCHECK_WOULD_HAVE_BEEN_A_NPE. Fix it by checking if
oldLine is null before calling #updateModifiedServerKey.

Change-Id: I8a2000492986e52ce7dbe25f48b321c05fd371e4
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>

Validate the extra headers and log but otherwise ignore invalid
headers. An empty http.extraHeader starts the list afresh.

The http.userAgent is restricted to printable 7-bit ASCII, other
characters are replaced by '.'.

Moves a support method from the ssh.apache bundle to HttpSupport in
the main JGit bundle.

Bug:541500
Change-Id: Id2d8df12914e2cdbd936ff00dc824d8f871bd580
Signed-off-by: James Wynn <james@jameswynn.com>
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Use a dedicated exception class to be able to detect this case in the
SshdSessionFactory and skip the generic SshException in that case.

Change-Id: I2a0bacf47bae82f154a0f4e79efbb2af2a17d0cf
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

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>

Close the channel gracefully to give the server a chance to clean up
properly on its side.

Bug: 565854
Change-Id: Iedda5af3b97c8321f08f7ce854274cbb30e401de
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

The timeout on RemoteSession.exec() cannot be a timeout for the
whole command. It can only be a timeout for setting up the process;
after that it's the application's responsibility to implement some
timeout for the execution of the command, for instance by calling
Process.waitFor(int, TimeUnit) or through other means.

Sessions returned by an SshSessionFactory are already connected and
authenticated -- they must be, because RemoteSession offers no
operations for connecting or authenticating a session.

Change the implementation of SshdExecProcess.waitFor() to wait
indefinitely. The original implementation used the timeout from
RemoteSession.exec() because of that erroneous javadoc.

Change-Id: I3c7ede24ab66d4c81f72d178ce5012d383cd826e
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>

Don't store session properties on the client but in a dedicated
per-session object that is attached to the sshd session.

Also make sure that each sshd session gets its own instance of
IdentityPasswordProvider that asks for passphrases of encrypted
private keys, and also store it on the session itself.

Bug: 563380
Change-Id: Ia88bf9f91cd22b5fd32b5972d8204d60f2de56bf
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>

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>

Log the stack trace in order to help understanding the bug 563380

Bug: 563380
Change-Id: If993a63ccec5042b10e1d5e945b18f4b5f06d8ff
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change target platforms to Orbit I20200319180910 and regenerate them.
Change package imports to [2.4.0,2.5.0); adapt code to upstream API
changes.

Maven build: update version in root pom.

Bazel build: update version & hash in WORKSPACE file.

Proxy functionality verified manually using 3proxy (HTTP & SOCKS,
with basic authentication) and ssh -vvv -D7020 localhost (SOCKS, no
authentication).

Bug: 561078
Change-Id: I582f6b98055b013c006f2c749890fe6db801cbaa
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

As reported by Sonar Lint:

Array designators should always be located on the type for better code
readability. Otherwise, developers must look both at the type and the
variable name to know whether or not a variable is an array.

Change-Id: If6b41fed3483d0992d402d8680552ab4bef89ffb
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

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>

and switch over strings where possible. Sometimes if statements are
chained and form a series of comparisons against constants. Using switch
statements improves readability.

Bug: 545856
Change-Id: Iacb78956ee5c20db4d793e6b668508ec67466606
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Since [1] the gerrit project includes jgit as a submodule, and has this
warning enabled, resulting in 100s of warnings in the console.

Also enable the warning here, and fix them.

At the same time, add missing braces around adjacent and nearby one-line
blocks.

[1] https://gerrit-review.googlesource.com/c/gerrit/+/227897

Change-Id: I81df3fc7ed6eedf6874ce1a3bedfa727a1897e4c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

The java.net.ProxySelector is quite a bit different from the one
in Eclipse. Eclipse (and the OS) uses "socks" as URI scheme to
look up a SOCKS proxy. java.net.ProxySelector needs "socket" as
scheme (and internally maps that to "socks" if and when it asks
the OS about the proxies).

Moreover, java.net.ProxySelector may return unresolved addresses,
whereas the Eclipse proxy selector always returns resolved addresses.

Fix both by explicitly resolving unresolved proxy addresses and using
scheme "socket" in the DefaultProxyDataFactory.

Tested manually with the jgit command-line tool using ssh -vvv -D7020
localhost and 3proxy as SOCKS5 proxies on localhost (3proxy with
user/password authentication). Start jgit with _JAVA_OPTIONS set to
"-DsocksProxyHost=<host> -DsocksProxyPort=<port>
-Djava.net.useSystemProxies=false" to test manually.

Bug: 548965
Change-Id: Ib81ae8255ac2f9c48268f172e7d8ebb4a792b66d
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

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>

The same effect could already be obtained if the ~/.ssh/config file
did not exist. But that is more difficult to control by clients,
since JGit would pick up the config if it was then created. Therefore
allow specifying a null config explicitly to permanently switch off
config file handling.

Change-Id: Iedf8a7f4d5c1ca08e0a513ed28301d8e5261b22a
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Reduce the dependency on the ClientSession in preparation to
remove it altogether. Remove the internal helper, re-implement
the needed bits. We have not implemented any configuration
possibility in JGit for creating hashed host names in known hosts
files, so we don't need the sshd code that theoretically would
enable this.

Change-Id: I295f5106b60e1cc3a9d085b0cb7ff747daae88be
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

We're actually interested only in the known public keys, we don't need
the corresponding host entry from the config.

Change-Id: Ibde6dffe9e3f87bfbb7c70d1f733b2b0e28cad71
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

The proxy handler may be re-set from an unspecified I/O thread.
Declare the shared variable as volatile.

Change-Id: I4e7ce393ae2cdc7f1cd4edf40c137da6d6c50ad5
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>

Convert anonymous inner classes to lambda expressions or member
references

Bug: 545856
CQ: 19537
Change-Id: I621431c178e8b99316314602f7c66c9a36f9ae98
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Add encrypted ed25519 keys in the tests; sshd 2.2.0 can finally
decrypt encrypted new-style OpenSSH key files. (Needs the "unlimited
strength" JCE, which is the default since Java 8u161. On older JREs,
users should install the policy files available from Oracle.)

The "expensive" key added has been generated with OpenSSH's
ssh-keygen -t ed25519 -a 256, i.e., with 256 bcrypt KDF rounds
instead of the default 16. On my machine it takes about 2sec to
decrypt.

Bug: 541703
Change-Id: Id3872ca2fd75d8f009cbc932eeb6357d3d1f267c
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Update target platforms, maven and bazel builds to use sshd 2.2.0.

Adapt internal classes to changed sshd interfaces and remove previous
work-arounds for asking repeatedly for key passwords and for loading
keys lazily; both are now done by sshd.

CQ: 19034
CQ: 19035
Bug: 541425
Change-Id: I85e1df6ebb8a94953a912d9b2b8a7b5bdfbd608a
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

The message delaying for the initial SSH messages (client
identification followed by the initial key exchange request)
was broken. sendKexInit() is _also_ called when a new key exchange
is requested. We inadvertently also re-sent the client identification
at that point, which is wrong and makes the server terminate the
connection.

Re-keying occurs from time to time during an SSH connection depending
on time, the number of messages (packets/blocks) exchanged, or the
amount of data exchanged. The net result was that for large
repositories data-intensive operations failed on the first re-keying.

Change the initial message delay such that the two messages for the
client identification and the initial key exchange can be buffered
individually while the proxy protocol is still in progress. The
AbstractClientProxyConnector can now buffer several commands, which
should also resolve bug 544715.

Bug: 545920
Change-Id: If09ee963a439b39098a0f52a1510237b428df8dd
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Change-Id: Ie44950f7d2f2f94a0412efb6c274f6e1e31efcd6
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I1a9112e6a4f938638c599b489cb0858eca27ab91
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Provide a mechanism for a subclass to provide its own set
of default identities from anywhere as an Iterable<KeyPair>.

The default implementation is functionally unchanged and uses
the known default identity files in the ~/.ssh directory. A subclass
can override the getDefaultKeys() function and return whatever keys
are appropriate.

Bug: 543152
Change-Id: I500d63146bc67e20e051f617790eb87c7cb500b6
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Change-Id: I143c242c0e3299323ae166a59947b1195539e6bf
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Don't use the ~/.ssh directory as cache key for the key provider
but the configured paths of the default keys. Otherwise changes
in that list of paths are not picked up.

This is in particular a problem for EGit, where the user can modify
this list of keys interactively in the preferences. Without this
change, Eclipse needs to be restarted to pick up such changes.

Bug: 542845
Change-Id: I63432fb10729a90b3c5e14f13e39bf482aef811b
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Change-Id: I0fdf595cba93f5a5cdd0496cee07ac91db304532
Signed-off-by: Mincong Huang <mincong.h@gmail.com>

Change-Id: I6bed174c062a0785641dc8ad69151bf7e843cdcf
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

This continues what commit d9ac7ddf10
(Remove unnecessary modifiers from interfaces, 2018-11-15) started.

Change-Id: I89720985a5a986722a0dcb9b5e9bbc25996bd5b3

ProxyDataFactory had a parameter of type HostConfigEntry, but actually
it wasn't used anywhere. Remove it -- it was the last leaked type from
Apache MINA sshd.

Also use the logger provided by upstream SshClient instead of creating
a new Logger.

Bug: 520927
Change-Id: Iaa78bbb998a5e574fa091664b75c48a3b9cfb897
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Add tests for password and keyboard-interactive authentication.
Implement password authentication; the default provided by sshd
is non-interactive, which is not useful for JGit.

Make sure the CredentialsProvider gets reset on successive password
retrieval attempts. Otherwise it might always return the same non-
accepted password from a secure storage. (That one was discovered
by actually trying this via EGit; the JGit tests don't catch this.)

Change the default order of authentication mechanisms to prefer
password over keyboard-interactive. This is a mitigation for upstream
bug SSHD-866.[1]

Also include a fix for upstream bug SSHD-867.[2]

[1] https://issues.apache.org/jira/projects/SSHD/issues/SSHD-866
[2] https://issues.apache.org/jira/projects/SSHD/issues/SSHD-867

Bug: 520927
Change-Id: I423e548f06d3b51531016cf08938c8bd7acaa2a9
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>

We will get an API evolution problem if we expose as API classes and
interfaces that derive from upstream classes or interfaces. Upstream
interfaces also evolve quite erratically and evolution doesn't seem
to follow semantic versioning.

Introduce a new KeyPasswordProvider interface so that we don't have
to depend on the upstream FilePasswordProvider in our API. (We do
need _some_ abstraction for getting passwords for encrypted keys in
the API; EGit will need to provide its own implementation.)

Move some other upstream dependencies (HostConfigEntry, and various
previously protected methods in SshdSessionFactory) out of the API:
classes moved to internal space, and methods made private.

The only dependencies on upstream interfaces are thus in a few method
parameter types. Those cannot be avoided, but should also not pose
problems.

Bug: 520927
Change-Id: Idc9c6b0f237f29f46343c0fe15179242f2007bec
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

sshd only asks exactly once for the password. C.f. upstream issue
SSHD-850.[1] So we have to work around this limitation for now.
Once we move to sshd > 2.1.0, this can be simplified somewhat.

[1] https://issues.apache.org/jira/browse/SSHD-850

Bug: 520927
Change-Id: Id65650228486c5ed30affa9c62eac982e01ae207
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

By default sshd will use its default built-in list, which matches
the one of openssh (as far as the algorithms exist in sshd at all).
But it doesn't handle HostKeyAlgorithms from the ssh config at all.

Implement this as in openssh, including the '+' and '-' modifiers
and reordering the default if there are known host keys for a
server already.

Add tests for the reordering.

Also use a more robust reader for the known hosts file. The default
aborts on the first error.

Bug: 520927
Change-Id: Ib1684440bfe2e96140536aa1a93c4bd4a0d35916
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

Set the internal property on the session as defined in the ssh config.

Note that NumberOfPasswordPrompts in openssh applies independently to
both user logins in keyboard-interactive authentication _and_ to
passphrases for identity files (encrypted keys). Apache MINA sshd uses
the setting only for keyboard-interactive authentication, but not for
identity file passphrase prompts. For identity files, it asks exactly
once. This has been reported as issue SSHD-850 upstream.[1]

[1] https://issues.apache.org/jira/browse/SSHD-850

Bug: 520927
Change-Id: I390ffe9e1c52b96d3e8e28fd8edbdc73dde9edb4
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

sshd does support gssapi-with-mic on the server side, but has no
built-in client-side support for this authentication mechanism.

Add our own implementation for it, following RFC 4462.[1] To avoid
needlessly re-trying mechanisms that aren't even configured on the
client, we disable mechanisms that fail on the very first attempt
to use them.

Since we have no real Kerberos5 test setup, this cannot be fully
tested in CI. The disabling of the authentication mechanism and
that it is skipped when not successful _is_ tested.

[1] https://www.ietf.org/rfc/rfc4462.txt

Bug: 520927
Change-Id: I5d0cdb14103588a57c52f927df541b589ab88d88
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>