If a user indicated they preferred to authenticate using APOP or a SASL
mechanism, but neither were supported by the server, curl would always
fall back to clear text when CAPA wasn't supported, even though the
user didn't want to use this.
This also fixes the auto build failure caused by commit 6f2d5f0562.
This commit replaces that of 9f260b5d66 because according to RFC-2449,
section 6, there is no APOP capability "...even though APOP is an
optional command in [POP3]. Clients discover server support of APOP by
the presence in the greeting banner of an initial challenge enclosed in
angle brackets."
Although highlighted by a bug in commit 1cfb436a2f, APOP
authentication could be chosen if the server was to reply with an empty
or missing timestamp in the server greeting and APOP was given in the
capability list by the server.
Added a loop to pop3_statemach_act() in which Curl_pp_readresp() is
called until the cache is drained. Without this multiple responses
received in a single packet could result in a hang or delay.
Similar to the processing of untagged CAPABILITY responses in IMAP and
multi-line EHLO responses in SMTP, moved the processing of multi-line
CAPA responses to pop3_state_capa_resp().
In an effort to reduce what pop3_endofresp() does and bring the POP3
source back inline with the IMAP and SMTP protocols, moved the APOP
detection into pop3_state_servergreet_resp().
Added support for downgrading the SASL authentication mechanism when the
decoding of CRAM-MD5, DIGEST-MD5 and NTLM messages fails. This enhances
the previously added support for graceful cancellation by allowing the
client to retry a lesser SASL mechanism such as LOGIN or PLAIN, or even
APOP / clear text (in the case of POP3 and IMAP) when supported by the
server.
In preparation for the upcoming SASL downgrade feature renamed the
imap__perform_authenticate(), pop3__perform_authenticate() and
smtp__perform_authenticate() functions.
Should a client application fail to decode an authentication message
received from a server, or not support any of the parameters given by
the server in the message, then the authentication phrase should be
cancelled gracefully by the client rather than simply terminating the
connection.
The authentication phrase should be cancelled by simply sending a '*'
to the server, in response to erroneous data being received, as per
RFC-3501, RFC-4954 and RFC-5034.
This patch adds the necessary state machine constants and appropriate
response handlers in order to add this functionality for the CRAM-MD5,
DIGEST-MD5 and NTLM authentication mechanisms.
Moved the standard SASL mechanism strings into curl_sasl.h rather than
hard coding the same values over and over again in the protocols that
use SASL authentication.
For more information about the mechanism strings see:
http://www.iana.org/assignments/sasl-mechanisms
Added the ability to use an XOAUTH2 bearer token [RFC6750] with POP3 for
authentication using RFC6749 "OAuth 2.0 Authorization Framework".
The bearer token is expected to be valid for the user specified in
conn->user. If CURLOPT_XOAUTH2_BEARER is defined and the connection has
an advertised auth mechanism of "XOAUTH2", the user and access token are
formatted as a base64 encoded string and sent to the server as
"AUTH XOAUTH2 <bearer token>".
All protocol handler structs are now opaque (void *) in the
SessionHandle struct and moved in the request-specific sub-struct
'SingleRequest'. The intension is to keep the protocol specific
knowledge in their own dedicated source files [protocol].c etc.
There's some "leakage" where this policy is violated, to be addressed at
a later point in time.
1 - always allocate the struct in protocol->setup_connection. Some
protocol handlers had to get this function added.
2 - always free at the end of a request. This is also an attempt to keep
less memory in the handle after it is completed.
Removed the hard returns from imap and pop3 by using the same style for
sending the authentication string as smtp. Moved the "Other mechanisms
not supported" check in smtp to match that of imap and pop3 to provide
consistency between the three email protocols.
