This default config is parsed and used a base before the actual
config is overlaid, so with these values not commented out, the
code to detect when no turn params were set and refuse to generate
credentials was never firing because the dummy default was always set.
We need to do a bit more validation when we get a server name, but don't want
to be re-doing it all over the shop, so factor out a separate
parse_and_validate_server_name, and do the extra validation.
Also, use it to verify the server name in the config file.
Make sure that server_names used in auth headers are sane, and reject them with
a sensible error code, before they disappear off into the depths of the system.
otherwise we explode with:
```
Traceback (most recent call last):
File /usr/lib/python2.7/logging/handlers.py, line 78, in emit
logging.FileHandler.emit(self, record)
File /usr/lib/python2.7/logging/__init__.py, line 950, in emit
StreamHandler.emit(self, record)
File /usr/lib/python2.7/logging/__init__.py, line 887, in emit
self.handleError(record)
File /usr/lib/python2.7/logging/__init__.py, line 810, in handleError
None, sys.stderr)
File /usr/lib/python2.7/traceback.py, line 124, in print_exception
_print(file, 'Traceback (most recent call last):')
File /usr/lib/python2.7/traceback.py, line 13, in _print
file.write(str+terminator)
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_io.py, line 170, in write
self.log.emit(self.level, format=u{log_io}, log_io=line)
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_logger.py, line 144, in emit
self.observer(event)
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_observer.py, line 136, in __call__
errorLogger = self._errorLoggerForObserver(brokenObserver)
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_observer.py, line 156, in _errorLoggerForObserver
if obs is not observer
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_observer.py, line 81, in __init__
self.log = Logger(observer=self)
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_logger.py, line 64, in __init__
namespace = self._namespaceFromCallingContext()
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/logger/_logger.py, line 42, in _namespaceFromCallingContext
return currentframe(2).f_globals[__name__]
File /home/matrix/.synapse/local/lib/python2.7/site-packages/twisted/python/compat.py, line 93, in currentframe
for x in range(n + 1):
RuntimeError: maximum recursion depth exceeded while calling a Python object
Logged from file site.py, line 129
File /usr/lib/python2.7/logging/__init__.py, line 859, in emit
msg = self.format(record)
File /usr/lib/python2.7/logging/__init__.py, line 732, in format
return fmt.format(record)
File /usr/lib/python2.7/logging/__init__.py, line 471, in format
record.message = record.getMessage()
File /usr/lib/python2.7/logging/__init__.py, line 335, in getMessage
msg = msg % self.args
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 4: ordinal not in range(128)
Logged from file site.py, line 129
```
...where the logger apparently recurses whilst trying to log the error, hitting the
maximum recursion depth and killing everything badly.
Most rooms have a trivial history visibility like "shared" or
"world_readable", especially large rooms, so lets not bother getting the
full membership of those rooms in that case.
