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Authentication Header and XMl

Jan.6

While working on the Django Alfresco integration I came across one of the most miserable bugs so far in the process. In order to make sure no one else has to go through it again, I'll write a little about it.

I was in the process of moving authentication out of the get parameters and into the header when I started getting the following error on POST or PUT.


   Wrapped Exception (with status template): 
   com.ctc.wstx.exc.WstxParsingException: Illegal processing 
   instruction target ("xml"); xml (case insensitive) is
   reserved by the specs.n at [row,col {unknown-source}]: [2,5]

Alfresco was not happy and I didn't really know why. Now best method to add an auth header is to use urllib's password manager, but that doesn't work because Alfresco accepts both username/password and a ticket for authentication. The ticket doesn't work with the password manager so we add the header manually.

The code looked something like this, where auth is user:password or a ticket.

class RESTRequest(urllib2.Request):
    def __init__(self, *args, **kwargs):
        self._method = kwargs.pop('method', 'GET')
        self._auth = kwargs.pop('auth', None)
        assert self._method in ['GET', 'POST', 'PUT', 'DELETE']
        urllib2.Request.__init__(self, *args, **kwargs)
        if self._auth:
            self.add_header('Authorization', 'Basic %s' 
            %  base64.encodestring(self._auth))

    def get_method(self):
        return self._method

Google wasn't that friendly at first, so I went through every line of Alfresco Restful services code to try to figure what was wrong with it. Obviously not the issue.

Then I found this post. Apparently base64.encodestring() adds a newline which makes the xml declaration the second line in the document and everything gets hosed up. Adding a strip() after the encoding fixes this.

self.add_header('Authorization', 'Basic %s' 
    %  base64.encodestring(self._auth).strip())

screeley.com

Authentication Header and XMl

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