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From "Goldstein Lyor (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (SSHD-860) org.apache.sshd.client.auth.pubkey.UserAuthPublicKeyIterator pre-loads client identities (private key files)
Date Tue, 06 Nov 2018 16:58:00 GMT

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

Goldstein Lyor updated SSHD-860:
    Priority: Minor  (was: Critical)

> 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
>            Priority: Minor
> {{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/commit/a71c62e66] 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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