[jira] [Resolved] (SSHD-860) org.apache.sshd.client.auth.pubkey.UserAuthPublicKeyIterator pre-loads client identities (private key files)

["Goldstein Lyor (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SSHD-860?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Goldstein Lyor resolved SSHD-860.
---------------------------------
       Resolution: Fixed
    Fix Version/s: 2.1.1

Hi [~wolft], I believe I have alleviated if not fixed the flow you described. Can you get the latest code, compile it and see if indeed it solves the problem ? If not, please re-open the issue and describe the flow that seems to be flawed.

> 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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