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, 2 insertions, 0 deletions

diff --git a/lib/pop3.h b/lib/pop3.h
index 99b514e4c..01701e4d7 100644
--- a/lib/pop3.h
+++ b/lib/pop3.h
@@ -29,6 +29,7 @@ typedef enum {
   POP3_STOP,         /* do nothing state, stops the state machine */
   POP3_SERVERGREET,  /* waiting for the initial greeting immediately after
                         a connect */
+  POP3_AUTH,
   POP3_USER,
   POP3_PASS,
   POP3_STARTTLS,
@@ -46,6 +47,7 @@ struct pop3_conn {
   size_t eob;        /* number of bytes of the EOB (End Of Body) that has been
                         received thus far */
   size_t strip;      /* number of bytes from the start to ignore as non-body */
+  unsigned int authmechs; /* Accepted authentication methods */
   pop3state state;   /* always use pop3.c:state() to change state! */
 };