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From "michael goulish (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PROTON-992) Proton's use of Cyrus SASL is not thread-safe.
Date Fri, 29 Apr 2016 19:26:12 GMT

    [ https://issues.apache.org/jira/browse/PROTON-992?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15264603#comment-15264603
] 

michael goulish commented on PROTON-992:
----------------------------------------

Dispatch is not yet immune to this issue.
Also, I think Proton needs to let the application handle initialization and shutdown of Cyrus
SASL.

I made a test that brings up a 6-router network, and randomly kills and restarts routers.
I get a router core, usually within 5 iterations, because of this issue.

Here is how I fixed it:

  1. Let dispatch code call sasl_client_init() and sasl_server_init()  at the top of qd_server_run().
 And remove these calls from Proton.  In keeping these calls to itself, Proton cannot prevent
two threads from simultaneously getting into sasl_*_init().  SegV City.

  2. Prevent proton from calling sasl_{client,server}_done(), in pni_sasl_impl_free().   Being
thread-agnostic, Proton cannot possibly know when it's safe to dispose of the sasl object,
which is being used by many threads.   Both of those Cyrus calls affect global state by NULLing
out a global pointer that stores the mechanisms string.

With these changes, my test has now run to 400 iterations with no crash.



> Proton's use of Cyrus SASL is not thread-safe.
> ----------------------------------------------
>
>                 Key: PROTON-992
>                 URL: https://issues.apache.org/jira/browse/PROTON-992
>             Project: Qpid Proton
>          Issue Type: Bug
>          Components: proton-c
>    Affects Versions: 0.10
>            Reporter: michael goulish
>            Assignee: Andrew Stitcher
>            Priority: Critical
>
> Documentation for the Cyrus SASL library says that the library is believed to be thread-safe
only if the code that uses it meets several requirements.
> The requirements are:
>     * you supply mutex functions (see sasl_set_mutex())
>     * you make no libsasl calls until sasl_client/server_init() completes
>     * no libsasl calls are made after sasl_done() is begun
>     * when using GSSAPI, you use a thread-safe GSS / Kerberos 5 library.
> It says explicitly that that sasl_set* calls are not thread safe, since they set global
state.
> The proton library makes calls to sasl_set* functions in :
>           pni_init_client()
>           pni_init_server(), and
>           pni_process_init()
> Since those are internal functions, there is no way for code that uses Proton to lock
around those calls.
> I think proton needs a new API call to let applications call sasl_set_mutex().  Or something.
> We probably also need other protections to meet the other requirements specified in the
Cyrus documentation (and quoted above).



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