On 19.2.2014, at 15.15, Jernej Porenta <jernej.pore...@arnes.si> wrote:
> we are seeing some strange issues with IMAP ID command using latest Roundcube > builds on dovecot 2.2.10 responding "Input buffer full, aborting". > > Roundcube webmail connects to IMAP server and issues ID command first with > some long arguments to ID command, however shorter than 1024 octets, which > are specified in RFC2971 for ID IMAP extension. > > The situation is easily reproducible (see http://pastebin.com/q4HX4wqb): > # telnet hostname 143 > * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE > AUTH=PLAIN AUTH=LOGIN] Server ready. > . ID ("name" "Roundcube" "version" "1.0-git" "php" "5.3.3" "os" "Linux" > "command" "<$long_less_than_1024_octets_string>") > * BYE Input buffer full, aborting > > However, this problem does not occur when user is already logged in. Before logging in Dovecot uses pretty strict limits on memory usage to avoid DoSing it. > RFC2971 is saying "Field strings MUST NOT be longer than 30 octets. Value > strings MUST NOT be longer than 1024 octets. Implementations MUST NOT send > more than 30 field-value pairs." > > IMHO, dovecot is handling ID command before successful login successfully > only if the length of the whole command is less than 1024 octets (exactly 861 > octets is working fine, over that "Input buffer full" occurs). > > I tried finding the reference in the source code, however I am unable to find > where this limit actually occurs (maybe IMAP_ARG_STRING imap_arg->type?) lib-master/master-auth.h MASTER_AUTH_MAX_DATA_SIZE affects it. Anyway, after thinking about this for a while I guess it's good to be RFC compliant, so I added some extra code to handle this better: http://hg.dovecot.org/dovecot-2.2/rev/3ecb2b831402 Although it's still probably not 100% RFC compliant, as it allows the maximum IMAP string parameter to be 1024 bytes before dropping the '\' escaping from \" quotes.
