CURL_MAX_INPUT_LENGTH: largest acceptable string input size

This limits all accepted input strings passed to libcurl to be less than
CURL_MAX_INPUT_LENGTH (8000000) bytes, for these API calls:
curl_easy_setopt() and curl_url_set().

The 8000000 number is arbitrary picked and is meant to detect mistakes
or abuse, not to limit actual practical use cases. By limiting the
acceptable string lengths we also reduce the risk of integer overflows
all over.

NOTE: This does not apply to `CURLOPT_POSTFIELDS`.

Test 1559 verifies.

Closes #3805

2 files changed, 82 insertions, 2 deletions

diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 304ee821f..31467e135 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -31,8 +31,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib1534 lib1535 lib1536 lib1537 lib1538 \
  lib1540 lib1541 \
  lib1550 lib1551 lib1552 lib1553 lib1554 lib1555 lib1556 lib1557 \
- lib1558 \
- lib1560 \
+ lib1558 lib1559 lib1560 \
  lib1591 lib1592 \
  lib1900 lib1905 lib1906 \
  lib2033
@@ -525,6 +524,9 @@ lib1557_CPPFLAGS = $(AM_CPPFLAGS) -DLIB1557
 lib1558_SOURCES = lib1558.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1558_LDADD = $(TESTUTIL_LIBS)
 
+lib1559_SOURCES = lib1559.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib1559_LDADD = $(TESTUTIL_LIBS)
+
 lib1560_SOURCES = lib1560.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib1560_LDADD = $(TESTUTIL_LIBS)
 
diff --git a/tests/libtest/lib1559.c b/tests/libtest/lib1559.c
new file mode 100644
index 000000000..2aa3615e0
--- /dev/null
+++ b/tests/libtest/lib1559.c
@@ -0,0 +1,78 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2019, 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.haxx.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 "testutil.h"
+#include "warnless.h"
+#include "memdebug.h"
+
+#define EXCESSIVE 10*1000*1000
+int test(char *URL)
+{
+  CURLcode res = 0;
+  CURL *curl = NULL;
+  char *longurl = malloc(EXCESSIVE);
+  CURLU *u;
+  (void)URL;
+
+  memset(longurl, 'a', EXCESSIVE);
+  longurl[EXCESSIVE-1] = 0;
+
+  global_init(CURL_GLOBAL_ALL);
+  easy_init(curl);
+
+  res = curl_easy_setopt(curl, CURLOPT_URL, longurl);
+  printf("CURLOPT_URL %d bytes URL == %d\n",
+         EXCESSIVE, (int)res);
+
+  res = curl_easy_setopt(curl, CURLOPT_POSTFIELDS, longurl);
+  printf("CURLOPT_POSTFIELDS %d bytes data == %d\n",
+         EXCESSIVE, (int)res);
+
+  u = curl_url();
+  if(u) {
+    CURLUcode uc = curl_url_set(u, CURLUPART_URL, longurl, 0);
+    printf("CURLUPART_URL %d bytes URL == %d\n",
+           EXCESSIVE, (int)uc);
+    uc = curl_url_set(u, CURLUPART_SCHEME, longurl, CURLU_NON_SUPPORT_SCHEME);
+    printf("CURLUPART_SCHEME %d bytes scheme == %d\n",
+           EXCESSIVE, (int)uc);
+    uc = curl_url_set(u, CURLUPART_USER, longurl, 0);
+    printf("CURLUPART_USER %d bytes user == %d\n",
+           EXCESSIVE, (int)uc);
+    curl_url_cleanup(u);
+  }
+
+  free(longurl);
+
+  curl_easy_cleanup(curl);
+  curl_global_cleanup();
+
+  return 0;
+
+test_cleanup:
+
+  curl_easy_cleanup(curl);
+  curl_global_cleanup();
+
+  return res; /* return the final return code */
+}