slachiewicz opened a new pull request, #903:
URL: https://github.com/apache/maven-wagon/pull/903
Same change as #902, on `master`. The cherry-pick was clean.
Two commits, separable: the first swaps the SSH library, the second fixes an
authentication bug that is independent of it.
Fixes #901. Fixes #503. Carries forward #680.
### 1. Move to the maintained JSch fork
`com.jcraft:jsch:0.1.55` was last released in 2018. The provider is not
merely unmaintained, it is already broken against current keys — here is 0.1.55
against two keys `ssh-keygen` produced with defaults on this machine:
```
jsch-0.1.55 enc_key -> JSchException: invalid privatekey
plain_key -> JSchException: invalid privatekey
com.github.mwiede enc_key -> OK
plain_key -> OK
```
It cannot read the OpenSSH-v1 format `ssh-keygen` has emitted by default
since OpenSSH 7.8, encrypted or not, and it has no `rsa-sha2-*`, so RSA
authentication fails against OpenSSH 8.8 and later anyway.
`com.github.mwiede:jsch:2.28.6` keeps the `com.jcraft.jsch` package, so the
API is unchanged. Its base bytecode is Java 8.
Two things needed care rather than a straight coordinate swap:
**The agent.** The `jsch.agentproxy` artifacts have no counterpart, and
their `ConnectorFactory` used to pick between agent kinds. The choice is now
explicit and still covers all three the old stack could reach —
`SSH_AUTH_SOCK`, Win32 OpenSSH, Pageant. One capability does narrow: reaching
the `SSH_AUTH_SOCK` agent needs a Unix domain socket, which the JDK provides
only from Java 16, and the fork declares no dependencies, so on Java 8–15 that
particular agent is out of reach without a helper library on the class path.
The other two need nothing. An agent holding no identities is now skipped
rather than installed as an empty repository.
**Passphrases.** `getPrivateKey()` substitutes an empty passphrase when the
settings name none. The old JSch discarded the result of `setPassphrase`, so an
encrypted key stayed encrypted and was unlocked later; the fork rejects it
instead. Left alone, that would have failed *every* encrypted key. Empty is now
translated back to none before the key is added:
```
enc_key, settings gave no passphrase -> accepted
plain_key, settings gave no passphrase -> accepted
enc_key, correct passphrase -> accepted
enc_key, wrong passphrase -> rejected
```
### 2. Stop a stray key file shadowing the agent (#503)
The agent was consulted only when no key file was found, and
`getPrivateKey()` finds one whenever no password is configured. On any machine
with a key in `~/.ssh` the agent was therefore unreachable — which is why the
reported workaround was to point `wagon.privateKeyDirectory` at an empty
directory.
The order is now: a key named in `settings.xml`, then the agent, then a key
file that merely happens to be in `~/.ssh`. Naming a key keeps today's
behaviour.
**This is a behaviour change to note in the release notes.** A reachable
agent holding identities now outranks a discovered key file, so someone whose
agent holds unrelated keys while the needed key sits unloaded in `~/.ssh` must
load it or name it. Combining both is not available to us: adding a file
identity on top of an agent repository makes JSch push that key *into* the
user's agent.
Also in this commit, key discovery looks for `id_ed25519`, `id_ecdsa`,
`id_rsa` instead of `id_dsa` then `id_rsa`. That code is in `ScpHelper`, so it
also changes which key `wagon-ssh-external` passes to `ssh -i`.
### Verification, and its limits
Modules build, `spotless:check` clean, default test run green.
**The change is not verified by the project's own SSH tests, because those
do not run.** The `-Dssh-tests` profile is excluded by default, and on the
unmodified branch point it gives 112 tests / 94 errors —
`ComponentLookupException: Unable to lookup component
'org.apache.maven.wagon.Wagon', roleHint: scp`, i.e. plexus test wiring rather
than anything SSH. My branch gives exactly the same 112 / 94, so this change
neither helps nor hurts it, but it means the embedded-MINA-server suite that
would genuinely exercise a library swap is unavailable. That harness deserves
fixing before this is relied on, and it is worth doing regardless of this PR.
What was verified directly is the key-handling matrix above, run against
both libraries.
Not yet done, and worth someone's hands before release: a real `site-deploy`
over scp and sftp against a current OpenSSH, on both Java 11 and Java 17, and
one Windows check of the agent path.
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