[fetchmail-devel] Fetchmail 6.3.8: "Invalid SSL protocol..." Error

[Stefano <fet...@po...>]

I recently installed Fetchmail (6.3.8) to collect my mail from various 
accounts, so that they could be automatically filtered and sorted. 
Since installation, I had been getting the following error whenever it 
polled my ISP's server (POP3):

Invalid SSL protocol '' specified, using default (SSLv23).

This does not happen when accessing other IMAP servers, but they don't 
support IMAP.  Given that I had added a cron job to check the accounts 
periodically, I kept receiving messages from the cron daemon with these 
errors; rather irritating.  Thus began my quest to track down and 
silence the error.

The documentation seems to indicate that an empty SSL protocol type 
string is valid, and would cause a default negotiation. Yet I was 
getting the error despite having specified ssl23 in the run control file.

I finally tracked it down to the fact that the particular POP3 server 
they use was rejecting the CAPA command, and, upon re-poll, sslproto was 
being set to "" (line 454 or so of pop3.c).

The subsequent call to SSLOpen() (driver.c:1625 or so, if I recall) was 
generating the error, after my protocol specification had been changed 
to '', as described above.

My solution was to modify socket.c as in the attached patch.  This seems 
to me to cause the correct behaviour, and appears to be more in keeping 
with the documentation.

I apologise for being so long winded, but wanted to try giving a 
sufficient description of the problem, so that others will have an idea 
of where the error comes from in the event that the provided patch turns 
out to be total nonsense or causes other problems.

I had read about this problem while trying to solve it, but it didn't 
seem to have been fixed in the latest development code, so I took a stab 
at it.