Do not crash with a null pointer dereference when opening the BSMTP file

fails. Improve error checking and reporting. Reported by Reto Schttel, 
Debian Bug#416625. Fix based on a patch by Nico Golde.

svn path=/branches/BRANCH_6-3/; revision=5070

2 files changed, 11 insertions, 2 deletions

diff --git a/NEWS b/NEWS
index 2a75864f..1b79f5e5 100644
--- a/NEWS
+++ b/NEWS
@@ -74,6 +74,9 @@ fetchmail 6.3.8 (not yet released):
   Reported by Nico Golde.
 * If SOCKS support was compiled in, add 'socks' to the feature_options Python
   list emitted in --configdump. Reported by Rob MacGregor.
+* Do not crash with a null pointer dereference when opening the BSMTP file 
+  fails. Improve error checking and reporting. Reported by Reto Schüttel,
+  Debian Bug#416625. Fix based on a patch by Nico Golde.
 
 # DOCUMENTATION:
 * Extend --mda documentation, discourage use of qmail-inject.
diff --git a/sink.c b/sink.c
index 92477ef9..22d2243a 100644
--- a/sink.c
+++ b/sink.c
@@ -708,6 +708,12 @@ static int open_bsmtp_sink(struct query *ctl, struct msgblk *msg,
     else
 	sinkfp = fopen(ctl->bsmtp, "a");
 
+    if (!sinkfp || ferror(sinkfp)) {
+	report(stderr, GT_("BSMTP file open failed: %s\n"), 
+		strerror(errno));
+        return(PS_BSMTP);
+    }
+
     /* see the ap computation under the SMTP branch */
     need_anglebrs = (msg->return_path[0] != '<');
     fprintf(sinkfp,
@@ -747,9 +753,9 @@ static int open_bsmtp_sink(struct query *ctl, struct msgblk *msg,
 
     fputs("DATA\r\n", sinkfp);
 
-    if (ferror(sinkfp))
+    if (fflush(sinkfp) || ferror(sinkfp))
     {
-	report(stderr, GT_("BSMTP file open or preamble write failed\n"));
+	report(stderr, GT_("BSMTP preamble write failed.\n"));
 	return(PS_BSMTP);
     }