Andrew Stitcher created PROTON-862:
Summary: Proton using Cyrus SASL library is problematic because
the library has global state
Project: Qpid Proton
Issue Type: Bug
Affects Versions: 0.10
Reporter: Andrew Stitcher
The Cyrus SASL library is not 100% suitable for use in other libraries because
it has global state and needs to be globally initialised before use as either a
SASL client or SASL server. One requirement for this global initialisation
seems to be to load the mechanism plugins.
This global state is problematic because we cannot dictate what the linked in
application and other libraries may do with Cyrus SASL themselves.
In particular we currently use the sasl_server_init() call to set the basename
for the config file that is used for the SASL settings. It is possible to work
around this by passing in NULL instead of a name and so not changing whatever
the application may have set. However we will then need to set the Cyrus SASL
options "manually" by implementing the SASL_CB_GETOPT callback which returns
the options set in the config file, so that we don't need Cyrus to do it for us.
Even so we would still have to be setting the global callbacks to NULL in our
initialisation, as there is no way to make Cyrus ignore the global callback
initialisation - this implies that for correct interop no library (and probably
no application either) can ever set these global callbacks, as they will have
no way to ensure that some random library loaded in doesn't reset them!
Another (perhaps better) alternative would be to port Proton to use another
SASL library, which better respects being used in a library and has no global
state. A good example of this would be libgsasl. However its API is
significantly more complex to use, largely because it doesn't do the user
authentication part itself and requires the application or dependant library to
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