infof: clearly indicate truncation

The internal buffer in infof() is limited to 2048 bytes of payload plus
an additional byte for NULL termination. Servers with very long error
messages can however cause truncation of the string, which currently
isn't very clear, and leads to badly formatted output.

This appends a "...\n" (or just "..." in case the format didn't with a
newline char) marker to the end of the string to clearly show
that it has been truncated.

Also include a unittest covering infof() to try and catch any bugs
introduced in this quite important function.

Closes #3216
Reviewed-by: Daniel Stenberg <daniel@haxx.se>
Reviewed-by: Marcel Raad <Marcel.Raad@teamviewer.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/tests/unit/unit1652.c b/tests/unit/unit1652.c
new file mode 100644
index 000000000..923c870f0
--- /dev/null
+++ b/tests/unit/unit1652.c
@@ -0,0 +1,133 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2018, 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 "curlcheck.h"
+
+#include "urldata.h"
+#include "sendf.h"
+
+/*
+ * This test hardcodes the knowledge of the buffer size which is internal to
+ * Curl_infof(). If that buffer is changed in size, this tests needs to be
+ * updated to still be valid.
+ */
+
+static struct Curl_easy *data;
+
+static char input[4096];
+static char result[4096];
+
+int debugf_cb(CURL *handle, curl_infotype type, char *buf, size_t size,
+              void *userptr);
+
+/*
+ * This debugf callback is simply dumping the string into the static buffer
+ * for the unit test to inspect. Since we know that we're only dealing with
+ * text we can afford the luxury of skipping the type check here.
+ */
+int
+debugf_cb(CURL *handle, curl_infotype type, char *buf, size_t size,
+                void *userptr)
+{
+  (void)handle;
+  (void)type;
+  (void)userptr;
+
+  memset(result, '\0', sizeof(result));
+  memcpy(result, buf, size);
+  return 0;
+}
+
+static CURLcode
+unit_setup(void)
+{
+  int res = 0;
+
+  global_init(CURL_GLOBAL_ALL);
+  data = curl_easy_init();
+  if(!data)
+    return CURLE_OUT_OF_MEMORY;
+  curl_easy_setopt(data, CURLOPT_DEBUGFUNCTION, debugf_cb);
+  curl_easy_setopt(data, CURLOPT_VERBOSE, 1L);
+  return CURLE_OK;
+}
+
+static void
+unit_stop(void)
+{
+  curl_easy_cleanup(data);
+  curl_global_cleanup();
+}
+
+UNITTEST_START
+
+/* Injecting a simple short string via a format */
+snprintf(input, sizeof(input), "Simple Test");
+Curl_infof(data, "%s", input);
+fail_unless(strcmp(result, input) == 0, "Simple string test");
+
+/* Injecting a few different variables with a format */
+Curl_infof(data, "%s %u testing %.1f\n", input, 42, 43.0123324);
+fail_unless(strcmp(result, "Simple Test 42 testing 43.0\n") == 0,
+            "Format string");
+
+/* Variations of empty strings */
+Curl_infof(data, "");
+fail_unless(strlen(result) == 0, "Empty string");
+Curl_infof(data, "%s", NULL);
+fail_unless(strcmp(result, "(nil)") == 0, "Passing NULL as string");
+
+/* A string just long enough to not be truncated */
+memset(input, '\0', sizeof(input));
+memset(input, 'A', 2048);
+Curl_infof(data, "%s", input);
+fail_unless(strlen(result) == 2048, "No truncation of infof input");
+fail_unless(strcmp(result, input) == 0, "No truncation of infof input");
+fail_unless(result[sizeof(result) - 1] == '\0',
+            "No truncation of infof input");
+
+/* Just over the limit for truncation without newline */
+memset(input + 2047, 'A', 4);
+Curl_infof(data, "%s", input);
+fail_unless(strlen(result) == 2048, "Truncation of infof input 1");
+fail_unless(result[sizeof(result) - 1] == '\0', "Truncation of infof input 1");
+fail_unless(strncmp(result + 2045, "...", 3) == 0,
+            "Truncation of infof input 1");
+
+/* Just over the limit for truncation with newline */
+memset(input + 2047, 'A', 4);
+memset(input + 2047 + 4, '\n', 1);
+Curl_infof(data, "%s\n", input);
+fail_unless(strlen(result) == 2048, "Truncation of infof input 2");
+fail_unless(result[sizeof(result) - 1] == '\0', "Truncation of infof input 2");
+fail_unless(strncmp(result + 2044, "...", 3) == 0,
+            "Truncation of infof input 2");
+
+/* Way over the limit for truncation with newline */
+memset(input, '\0', sizeof(input));
+memset(input, 'A', sizeof(input) - 1);
+Curl_infof(data, "%s\n", input);
+fail_unless(strlen(result) == 2048, "Truncation of infof input 3");
+fail_unless(result[sizeof(result) - 1] == '\0', "Truncation of infof input 3");
+fail_unless(strncmp(result + 2044, "...", 3) == 0,
+            "Truncation of infof input 3");
+
+UNITTEST_STOP