tool_writeout: fixed a buffer read overrun on --write-out

If a % ended the statement, the string's trailing NUL would be skipped
and memory past the end of the buffer would be accessed and potentially
displayed as part of the --write-out output. Added tests 1440 and 1441
to check for this kind of condition.

Reported-by: Brian Carpenter

src/tool_writeout.c

@@ -113,7 +113,7 @@ void ourWriteOut(CURL *curl, struct OutStruct *outs, const char *writeinfo)
   double doubleinfo;
 
   while(ptr && *ptr) {
-    if('%' == *ptr) {
+    if('%' == *ptr && ptr[1]) {
       if('%' == ptr[1]) {
         /* an escaped %-letter */
         fputc('%', stream);

tests/data/Makefile.inc

@@ -153,7 +153,7 @@ test1408 test1409 test1410 test1411 test1412 test1413 test1414 test1415 \
 test1416 test1417 test1418 test1419 test1420 test1421 test1422 test1423 \
 test1424 \
 test1428 test1429 test1430 test1431 test1432 test1433 test1434 test1435 \
-test1436 test1437 test1438 test1439 \
+test1436 test1437 test1438 test1439 test1440 test1441 \
 \
 test1500 test1501 test1502 test1503 test1504 test1505 test1506 test1507 \
 test1508 test1509 test1510 test1511 test1512 test1513 test1514 test1515 \

tests/data/test1440

@@ -0,0 +1,31 @@
+<testcase>
+<info>
+<keywords>
+--write-out
+</keywords>
+</info>
+# Server-side
+<reply>
+</reply>
+
+# Client-side
+<client>
+<server>
+file
+</server>
+
+<name>
+Check --write-out with trailing %{
+</name>
+<command>
+file://localhost/%PWD/log/ --write-out '%{'
+</command>
+</client>
+
+# Verify data
+<verify>
+<stdout nonewline="yes">
+%{
+</stdout>
+</verify>
+</testcase>

tests/data/test1441

@@ -0,0 +1,31 @@
+<testcase>
+<info>
+<keywords>
+--write-out
+</keywords>
+</info>
+# Server-side
+<reply>
+</reply>
+
+# Client-side
+<client>
+<server>
+file
+</server>
+
+<name>
+Check --write-out with trailing %
+</name>
+<command>
+file://localhost/%PWD/log/ --write-out '%'
+</command>
+</client>
+
+# Verify data
+<verify>
+<stdout nonewline="yes">
+%
+</stdout>
+</verify>
+</testcase>