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https://issues.apache.org/jira/browse/SSHD-860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16679404#comment-16679404
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Thomas Wolf commented on SSHD-860:
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Thanks for the effort. But it doesn't work yet.
# The first call to {{current.hasNext()}} in {{UserAuthPublicKeyIterator}} now
still loads the two keys of the first KeyPair iterator. Basically
{{LazyIterablesConcatenator.lazyConcatenateIterables(one, two)}} isn't lazy
yet. There's pre-loading going on for "one", and once "one" is exhausted and
the first {{hasNext()}} on "two" is called, there's pre-loading happening on
"two".
# It is legal to call {{Iterator.next()}} without having called
{{Iterator.hasNext()}} before. So all those cases where the new code does
{{throw new IllegalStateException("'next()' called without a preceding
'hasNext()' query");}} are wrong.
And actually I should test (1) in the solution I implemented in JGit, too. I
noticed that the JGit tests exercise this only with iterators containing one
element each, so I wouldn't have noticed. I need to add a test in JGit with
several identities per iterator. I suspect I'll then see that same behavior in
JGit, too. :(
> org.apache.sshd.client.auth.pubkey.UserAuthPublicKeyIterator pre-loads client
> identities (private key files)
> ------------------------------------------------------------------------------------------------------------
>
> Key: SSHD-860
> URL: https://issues.apache.org/jira/browse/SSHD-860
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 2.0.0, 2.1.0, 2.1.1
> Reporter: Thomas Wolf
> Assignee: Goldstein Lyor
> Priority: Major
> Fix For: 2.1.1
>
>
> {{org.apache.sshd.client.auth.pubkey.UserAuthPublicKeyIterator}} loads and
> caches in memory private keys prematurely. Keys are loaded even if they are
> not used at all in the end. In other words, incremental loading of keys
> doesn't work.
> This is bad for two reasons:
> # Private keys should be kept in memory only if and when needed. Loading
> completely unused private keys must be avoided.
> # With encrypted private keys, the user may end up being asked for
> passphrases for keys that are not used at all in the end, which is highly
> disruptive.
> {{org.apache.sshd.client.auth.pubkey.UserAuthPublicKeyIterator}} does in its
> constructor:
> {code:java}
> Iterator<? extends PublicKeyIdentity> current;
> Collection<Stream<? extends PublicKeyIdentity>> identities = new
> LinkedList<>();
> ...
> identities.add(Stream.of(ClientSession.providerOf(session))
> .map(KeyIdentityProvider::loadKeys)
> .flatMap(GenericUtils::stream)
> .map(kp -> new KeyPairIdentity(signatureFactories, session, kp)));
> current = identities.stream().flatMap(r -> r).iterator();
> {code}
> The final {{current}} iterator uses some internal buffer (size unknown;
> didn't try to determine it) and will pre-fill this buffer completely. So with
> buffer size _N_ it'll pre-load the first _N_ keys from the combined identity
> stream. If the first key authenticates successfully, loading all the others
> must not be done.
> See my [test
> case|https://github.com/tomaswolf/mina-sshd/blob/SSHD-860/sshd-core/src/test/java/org/apache/sshd/client/ClientKeyLoadTest.java]
> showing this faulty behavior. It does exactly the same as the
> {{UserAuthPublicKeyIterator}} constructor, using two iterators with two
> identity files each, and then tests the resulting iterator. The first
> {{hasNext()/next()}} call on the {{current}} iterator _loads all four keys!_
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