cookie: CURLOPT_COOKIEFILE set to NULL switches off cookies

Add test 676 to verify that setting CURLOPT_COOKIEFILE to NULL again clears
the cookiejar from memory.

Reported-by: Stefan Karpinski
Fixes #6889
Closes #6891

6 files changed, 175 insertions, 3 deletions

diff --git a/docs/libcurl/opts/CURLOPT_COOKIEFILE.3 b/docs/libcurl/opts/CURLOPT_COOKIEFILE.3
index 48706b741..039f60a85 100644
--- a/docs/libcurl/opts/CURLOPT_COOKIEFILE.3
+++ b/docs/libcurl/opts/CURLOPT_COOKIEFILE.3
@@ -5,7 +5,7 @@
 .\" *                            | (__| |_| |  _ <| |___
 .\" *                             \___|\___/|_| \_\_____|
 .\" *
-.\" * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+.\" * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
 .\" *
 .\" * This software is licensed as described in the file COPYING, which
 .\" * you should have received as part of this distribution. The terms
@@ -57,6 +57,9 @@ Subsequent files will add more cookies.
 
 The application does not have to keep the string around after setting this
 option.
+
+Setting this option to NULL will (since 7.77.0) explicitly disable the cookie
+engine and clear the list of files to read cookies from.
 .SH DEFAULT
 NULL
 .SH PROTOCOLS
diff --git a/lib/setopt.c b/lib/setopt.c
index 022dd3800..5944482a8 100644
--- a/lib/setopt.c
+++ b/lib/setopt.c
@@ -752,6 +752,20 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option, va_list param)
       }
       data->state.cookielist = cl; /* store the list for later use */
     }
+    else {
+      /* clear the list of cookie files */
+      curl_slist_free_all(data->state.cookielist);
+      data->state.cookielist = NULL;
+
+      if(!data->share || !data->share->cookies) {
+        /* throw away all existing cookies if this isn't a shared cookie
+           container */
+        Curl_cookie_clearall(data->cookies);
+        Curl_cookie_cleanup(data->cookies);
+      }
+      /* disable the cookie engine */
+      data->cookies = NULL;
+    }
     break;
 
   case CURLOPT_COOKIEJAR:
diff --git a/tests/data/Makefile.inc b/tests/data/Makefile.inc
index d083baffa..02ac45efd 100644
--- a/tests/data/Makefile.inc
+++ b/tests/data/Makefile.inc
@@ -90,7 +90,7 @@ test635 test636 test637 test638 test639 test640 test641 test642 \
 test643 test644 test645 test646 test647 test648 test649 test650 test651 \
 test652 test653 test654 test655 test656 test658 test659 test660 test661 \
 test662 test663 test664 test665 test666 test667 test668 test669 \
-test670 test671 test672 test673 test674 test675 \
+test670 test671 test672 test673 test674 test675 test676 \
 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \
 test709 test710 test711 test712 test713 test714 test715 test716 test717 \
diff --git a/tests/data/test676 b/tests/data/test676
new file mode 100644
index 000000000..a3916e526
--- /dev/null
+++ b/tests/data/test676
@@ -0,0 +1,83 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+HTTP set cookie
+cookies
+CURLOPT_REFERER
+curl_easy_reset
+</keywords>
+</info>
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK

+Date: Tue, 09 Nov 2010 14:49:00 GMT

+Content-Length: 6

+Connection: close

+Content-Type: text/html

+

+-foo-
+</data>
+
+# since the request runs twice
+<datacheck>
+HTTP/1.1 200 OK

+Date: Tue, 09 Nov 2010 14:49:00 GMT

+Content-Length: 6

+Connection: close

+Content-Type: text/html

+

+-foo-
+HTTP/1.1 200 OK

+Date: Tue, 09 Nov 2010 14:49:00 GMT

+Content-Length: 6

+Connection: close

+Content-Type: text/html

+

+-foo-
+</datacheck>
+
+</reply>
+
+# Client-side
+<client>
+<file name="log/cookies676">
+%HOSTIP	TRUE	/we/want/	FALSE	2118138987	proven	yes
+</file>
+<server>
+http
+</server>
+# tool is what to use instead of 'curl'
+<tool>
+lib%TESTNUMBER
+</tool>
+
+ <name>
+verify setting CURLOPT_COOKIEFILE to NULL again
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/we/want/%TESTNUMBER
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<protocol>
+GET /we/want/%TESTNUMBER HTTP/1.1

+Host: %HOSTIP:%HTTPPORT

+User-Agent: the-moo agent next generation

+Accept: */*

+Cookie: proven=yes

+

+GET /we/want/%TESTNUMBER HTTP/1.1

+Host: %HOSTIP:%HTTPPORT

+User-Agent: the-moo agent next generation

+Accept: */*

+

+</protocol>
+</verify>
+</testcase>
diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 9f2ba8a91..ff39de377 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -48,7 +48,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib599 \
  lib643 lib644 lib645 lib650 lib651 lib652 lib653 lib654 lib655 lib658   \
  lib659 lib661 lib666 lib667 lib668 \
- lib670 lib671 lib672 lib673 lib674 \
+ lib670 lib671 lib672 lib673 lib674 lib676 \
  lib1156 \
  lib1500 lib1501 lib1502 lib1503 lib1504 lib1505 lib1506 lib1507 lib1508 \
  lib1509 lib1510 lib1511 lib1512 lib1513 lib1514 lib1515         lib1517 \
@@ -405,6 +405,10 @@ lib674_SOURCES = lib674.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib674_LDADD = $(TESTUTIL_LIBS)
 lib674_CPPFLAGS = $(AM_CPPFLAGS)
 
+lib676_SOURCES = lib676.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib676_LDADD = $(TESTUTIL_LIBS)
+lib676_CPPFLAGS = $(AM_CPPFLAGS)
+
 lib1500_SOURCES = lib1500.c $(SUPPORTFILES) $(TESTUTIL)
 lib1500_LDADD = $(TESTUTIL_LIBS)
 lib1500_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/libtest/lib676.c b/tests/libtest/lib676.c
new file mode 100644
index 000000000..2d0b31c5c
--- /dev/null
+++ b/tests/libtest/lib676.c
@@ -0,0 +1,68 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+#include "test.h"
+
+#include "memdebug.h"
+
+int test(char *URL)
+{
+  CURLcode res;
+  CURL *curl;
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  curl = curl_easy_init();
+  if(!curl) {
+    fprintf(stderr, "curl_easy_init() failed\n");
+    curl_global_cleanup();
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  test_setopt(curl, CURLOPT_URL, URL);
+  test_setopt(curl, CURLOPT_HEADER, 1L);
+  test_setopt(curl, CURLOPT_USERAGENT, "the-moo agent next generation");
+  test_setopt(curl, CURLOPT_COOKIEFILE, "log/cookies676");
+  test_setopt(curl, CURLOPT_VERBOSE, 1L);
+
+  res = curl_easy_perform(curl);
+  if(res) {
+    fprintf(stderr, "retrieve 1 failed\n");
+    goto test_cleanup;
+  }
+
+  /* now clear the cookies */
+  test_setopt(curl, CURLOPT_COOKIEFILE, NULL);
+
+  res = curl_easy_perform(curl);
+  if(res)
+    fprintf(stderr, "retrieve 2 failed\n");
+
+test_cleanup:
+
+  curl_easy_cleanup(curl);
+  curl_global_cleanup();
+
+  return (int)res;
+}