[balsa] imap-handle: Do not crash on PREAUTH greeting

[Peter Bloomfield <peterb src gnome org>]

commit 4e245d758e1c826a01080d40c22ca8706f0339e5
Author: Albrecht Dreß <albrecht dress arcor de>
Date:   Sun Feb 16 14:39:59 2020 -0500

    imap-handle: Do not crash on PREAUTH greeting
    
    when it hasn't resulted in storing last-message.
    
    * libbalsa/imap/imap-handle.c
        (imap_mbox_connect): do not dereference NULL ImapHandle:last_msg;
        (ir_preauth): parse a PREAUTH greeting the same as an OK greeting.
    
    Fixes https://gitlab.gnome.org/GNOME/balsa/issues/23

 ChangeLog                   | 12 ++++++++++++
 libbalsa/imap/imap-handle.c | 12 ++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 34596991e..f501d2f35 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2020-02-16  Albrecht Dreß  <albrecht dress arcor de>
+
+       imap-handle: Do not crash on PREAUTH greeting
+
+       when it hasn't resulted in storing last-message.
+
+       * libbalsa/imap/imap-handle.c (imap_mbox_connect): do not
+       dereference NULL ImapHandle:last_msg;
+       (ir_preauth): parse PREAUTH greeting the same as OK.
+
+       Fixes https://gitlab.gnome.org/GNOME/balsa/issues/23
+
 2020-02-07  Peter Bloomfield  <pbloomfield bellsouth net>
 
        mailbox: Sort when new details about a message are found
diff --git a/libbalsa/imap/imap-handle.c b/libbalsa/imap/imap-handle.c
index 72404301b..62e87cd81 100644
--- a/libbalsa/imap/imap-handle.c
+++ b/libbalsa/imap/imap-handle.c
@@ -699,7 +699,7 @@ imap_mbox_connect(ImapMboxHandle* handle)
     imap_handle_disconnect(handle);
     return IMAP_PROTOCOL_ERROR;
   }
-  handle->can_fetch_body = 
+  handle->can_fetch_body = (handle->last_msg != NULL) &&
     (strncmp(handle->last_msg, "Microsoft Exchange", 18) != 0);
   if((handle->tls_mode == NET_CLIENT_CRYPT_ENCRYPTED) ||
         (handle->tls_mode == NET_CLIENT_CRYPT_NONE)) {
@@ -2344,9 +2344,13 @@ ir_bad(ImapMboxHandle *h)
 static ImapResponse
 ir_preauth(ImapMboxHandle *h)
 {
-  if(imap_mbox_handle_get_state(h) == IMHS_CONNECTED)
-    imap_mbox_handle_set_state(h, IMHS_AUTHENTICATED);
-  return IMR_OK;
+       ImapResponse resp;
+
+       resp = ir_ok(h);
+       if ((resp == IMR_OK) && (imap_mbox_handle_get_state(h) == IMHS_CONNECTED)) {
+               imap_mbox_handle_set_state(h, IMHS_AUTHENTICATED);
+       }
+       return resp;
 }
 
 /* ir_bye: