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https://issues.apache.org/jira/browse/SSHD-860?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16689430#comment-16689430
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Konrad Windszus commented on SSHD-860:
--------------------------------------
[~lgoldstein] Does that mean the fix-version 2.1.1 indicated on this JIRA is
not correct?
> 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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