pop3: Added support for SASL based authentication mechanism detection

Added support for detecting the supported SASL authentication mechanisms
via the AUTH command. There are two ways of detecting them, either by
using the AUTH command, that will return -ERR if not supported or by
using the CAPA command which will return SASL and the list of mechanisms
if supported, not include SASL if SASL authentication is not supported
or -ERR if the CAPA command is not supported. As such it seems simpler
to use the AUTH command and fallback to normal clear text authentication
if the the command is not supported.

Additionally updated the test cases to return -ERR when the AUTH command
is encountered. Additional test cases will be added when support for the
individual authentication mechanisms is added.

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/data/test815 b/tests/data/test815
index df7b1b6dd..9779fe690 100644
--- a/tests/data/test815
+++ b/tests/data/test815
@@ -9,6 +9,9 @@ RETR
 #
 # Server-side
 <reply>
+<servercmd>

+REPLY AUTH -ERR unsupported command

+</servercmd>

 <data>
 From: me@somewhere

 To: fake@nowhere

@@ -49,6 +52,7 @@ pop3://%HOSTIP:%POP3PORT/815 -u user:secret
 # Verify data after the test has been "shot"
 <verify>
 <protocol>
+AUTH

 USER user

 PASS secret

 RETR 815