Tickets :: Comment on [#12282] Handling IMAP server errors can lead to DoS

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Comment	> I've selected IMP as the category, because that's where it occurs, > and I'm not sure where it should be fixed. > The problem happens when I do some IMAP operations and the server > gives back an error, like here: > * 11 FETCH (UID 19 FLAGS (\Seen) RFC822.SIZE 2418 ENVELOPE ("Fri, 28 > Nov 2008 19:20:40 +0100" {102} > A Magyar =?iso-8859-1?Q?Di=E1ksport_Sz=F6v?= > =?iso-8859-1?Q?ets=E9g_H=EDrei_2008=2E_november_28-=E1n?= > (("Diaksporthir" NIL "diaksporthir" "mdsz.hu")) (("Diaksporthir" NIL > "diaksporthir" "mdsz.hu")) ((NIL NIL "diaksporthir" "mdsz.hu")) ((NIL > NIL "bra" "fsn.hu")) NIL NIL NIL "<20081128182040.GA20477@mdsz.hu>") > BODY[HEADER.FIELDS (IMPORTANCE LIST-POST X-PRIORITY)] {2} > > ) > * 12 FETCH (UID 20 FLAGS (\Seen Junk)) > * BYE Internal error occurred. Refer to server log for more > information. [2013-05-29 17:30:25] > > After this, the PHP process goes berserk by logging these lines (I > use syslog, so syslog also gets some heavy times): > May 29 17:31:47 wm01a HORDE: [imp] PHP ERROR: fgets() expects > parameter 1 to be resource, null given [pid 1474 on line 4203 of > "/usr/local/share/pear/Horde/Imap/Client/Socket.php"] > May 29 17:31:47 wm01a HORDE: [imp] PHP ERROR: feof() expects > parameter 1 to be resource, null given [pid 1474 on line 4190 of > "/usr/local/share/pear/Horde/Imap/Client/Socket.php"] > May 29 17:31:47 wm01a HORDE: [imp] PHP ERROR: fgets() expects > parameter 1 to be resource, null given [pid 1474 on line 4203 of > "/usr/local/share/pear/Horde/Imap/Client/Socket.php"] > > This goes in an infinite loop (until max execution time is reached), > logging into syslog as fast as it can. Repeating this some more times > on the web UI makes the whole system unusable, even denying logging > in via sshd (syslogd is so overwhelmed that it blocks it). > > I think it would be nice to prepare for IMAP errors other than > logging more than 2000 lines per second, effectively causing a DoS to > the system. :)
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