fix a fuzzing issue from a string as a bracket (#1110)

fix fuzzing issue

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: phlptp

Diff for: book/chapters/config.md

@@ -259,6 +259,26 @@ The config parser has a modifier
 This modification will insert the separator between each line even if not
 sequential. This allows an input option to be configured with multiple lines.
 
+```toml
+# Examples of vector of vector inputs in config
+
+# this example is how config_to_str writes it out
+vector1 = [a,v,"[]"]
+```
+
+The field insertion has a special processing for duplicate characters starting
+with "[[" in which case the `"[]"` gets translated to `[[]]` before getting
+passed into the option which converts it back into the correct string. This can
+also be used on the command line to handle unusual parsing situation with
+brackets.
+
+### Argument With Brackets
+
+There is an edge case with actual strings that are surrounded by brackets. For
+example if the string "[]" needed to be passed. this would normally trigger the
+bracket processing and result in an empty vector. In this case it can be
+enclosed in quotes and should be handled correctly.
+
 ## Multiple configuration files
 
 If it is desired that multiple configuration be allowed. Use

Diff for: include/CLI/impl/Config_inl.hpp

@@ -561,16 +561,6 @@ ConfigBase::to_config(const App *app, bool default_also, bool write_description,
                 }
 
                 if(!value.empty()) {
-                    if(opt->get_expected_max() > 1 && detail::is_binary_escaped_string(value) && results.size() == 1 &&
-                       !results[0].empty()) {
-                        if(results[0].front() == '[' && results[0].back() == ']') {
-                            // this is a condition which could be misinterpreted
-                            results[0].insert(0, 1, results[0].front());
-                            results[0].push_back(results[0].back());
-                            value = detail::ini_join(
-                                results, arraySeparator, arrayStart, arrayEnd, stringQuote, literalQuote);
-                        }
-                    }
                     if(!opt->get_fnames().empty()) {
                         try {
                             value = opt->get_flag_value(single_name, value);

Diff for: include/CLI/impl/Option_inl.hpp

@@ -662,16 +662,37 @@ CLI11_INLINE std::string Option::_validate(std::string &result, int index) const
 
 CLI11_INLINE int Option::_add_result(std::string &&result, std::vector<std::string> &res) const {
     int result_count = 0;
+
+    // Handle the vector escape possibility all characters duplicated and starting with [[ ending with ]]
+    // this is always a single result
+    if(result.size() >= 4 && result[0] == '[' && result[1] == '[' && result.back() == ']' &&
+       (*(result.end() - 2) == ']')) {
+        // this is an escape clause for odd strings
+        std::string nstrs{'['};
+        bool duplicated{true};
+        for(std::size_t ii = 2; ii < result.size() - 2; ii += 2) {
+            if(result[ii] == result[ii + 1]) {
+                nstrs.push_back(result[ii]);
+            } else {
+                duplicated = false;
+                break;
+            }
+        }
+        if(duplicated) {
+            nstrs.push_back(']');
+            res.push_back(std::move(nstrs));
+            ++result_count;
+            return result_count;
+        }
+    }
+
     if((allow_extra_args_ || get_expected_max() > 1) && !result.empty() && result.front() == '[' &&
        result.back() == ']') {  // this is now a vector string likely from the default or user entry
+
         result.pop_back();
         result.erase(result.begin());
         bool skipSection{false};
         for(auto &var : CLI::detail::split_up(result, ',')) {
-            if(var == result) {
-                skipSection = true;
-                break;
-            }
             if(!var.empty()) {
                 result_count += _add_result(std::move(var), res);
             }

Diff for: include/CLI/impl/StringTools_inl.hpp

@@ -519,23 +519,38 @@ CLI11_INLINE void remove_quotes(std::vector<std::string> &args) {
     }
 }
 
+CLI11_INLINE void handle_secondary_array(std::string &str) {
+    if(str.size() >= 2 && str.front() == '[' && str.back() == ']') {
+        // handle some special array processing for arguments if it might be interpreted as a secondary array
+        std::string tstr{"[["};
+        for(std::size_t ii = 1; ii < str.size(); ++ii) {
+            tstr.push_back(str[ii]);
+            tstr.push_back(str[ii]);
+        }
+        str = std::move(tstr);
+    }
+}
+
 CLI11_INLINE bool process_quoted_string(std::string &str, char string_char, char literal_char) {
     if(str.size() <= 1) {
         return false;
     }
     if(detail::is_binary_escaped_string(str)) {
         str = detail::extract_binary_string(str);
+        handle_secondary_array(str);
         return true;
     }
     if(str.front() == string_char && str.back() == string_char) {
         detail::remove_outer(str, string_char);
         if(str.find_first_of('\\') != std::string::npos) {
             str = detail::remove_escaped_characters(str);
         }
+        handle_secondary_array(str);
         return true;
     }
     if((str.front() == literal_char || str.front() == '`') && str.back() == str.front()) {
         detail::remove_outer(str, str.front());
+        handle_secondary_array(str);
         return true;
     }
     return false;

Diff for: tests/FuzzFailTest.cpp

@@ -267,7 +267,7 @@ TEST_CASE("app_roundtrip_custom") {
     CLI::FuzzApp fuzzdata2;
     auto app = fuzzdata.generateApp();
     auto app2 = fuzzdata2.generateApp();
-    int index = GENERATE(range(1, 3));
+    int index = GENERATE(range(1, 4));
     std::string optionString, flagString;
     auto parseData = loadFailureFile("round_trip_custom", index);
     std::size_t pstring_start{0};

Diff for: tests/OptionTypeTest.cpp

@@ -1225,6 +1225,21 @@ TEST_CASE_METHOD(TApp, "vectorSingleArg", "[optiontype]") {
     CHECK("4" == extra);
 }
 
+TEST_CASE_METHOD(TApp, "vectorEmptyArg", "[optiontype]") {
+
+    std::vector<std::string> cv{"test"};
+    app.add_option("-c", cv);
+    args = {"-c", "test1", "[]"};
+
+    run();
+    CHECK(cv.size() == 1);
+    args = {"-c", "test1", "[[]]"};
+
+    run();
+    CHECK(cv.size() == 2);
+    CHECK(cv[1] == "[]");
+}
+
 TEST_CASE_METHOD(TApp, "vectorDoubleArg", "[optiontype]") {
 
     std::vector<std::pair<int, std::string>> cv;
@@ -1249,6 +1264,18 @@ TEST_CASE_METHOD(TApp, "vectorEmpty", "[optiontype]") {
     CHECK(cv.empty());
 }
 
+TEST_CASE_METHOD(TApp, "vectorVectorArg", "[optiontype]") {
+
+    std::vector<std::vector<std::string>> cv{};
+    app.add_option("-c", cv);
+    args = {"-c", "[[a,b]]"};
+
+    run();
+    CHECK(cv.size() == 1);
+    CHECK(cv[0].size() == 2);
+    CHECK(cv[0][0] == "a");
+}
+
 TEST_CASE_METHOD(TApp, "OnParseCall", "[optiontype]") {
 
     int cnt{0};