<regex>: add checks for integer overflow

stl/inc/regex

@@ -1678,8 +1678,8 @@ private:
     void _Expect(_Meta_type, regex_constants::error_type);
 
     // parsing
-    int _Do_digits(int _Base, int _Count);
-    bool _DecimalDigits();
+    int _Do_digits(int _Base, int _Count, regex_constants::error_type);
+    bool _DecimalDigits(regex_constants::error_type);
     void _HexDigits(int);
     bool _OctalDigits();
     void _Do_ex_class(_Meta_type);
@@ -3899,10 +3899,14 @@ void _Parser<_FwdIt, _Elem, _RxTraits>::_Expect(_Meta_type _St, regex_constants:
 }
 
 template <class _FwdIt, class _Elem, class _RxTraits>
-int _Parser<_FwdIt, _Elem, _RxTraits>::_Do_digits(int _Base, int _Count) { // translate digits to numeric value
+int _Parser<_FwdIt, _Elem, _RxTraits>::_Do_digits(
+    int _Base, int _Count, regex_constants::error_type _ErrorType) { // translate digits to numeric value
     int _Chv;
     _Val = 0;
     while (_Count != 0 && (_Chv = _Traits.value(_Char, _Base)) != -1) { // append next digit
+        if (_Val > ((INT_MAX - _Chv) / _Base)) {
+            _Error(_ErrorType);
+        }
         --_Count;
         _Val *= _Base;
         _Val += _Chv;
@@ -3912,20 +3916,21 @@ int _Parser<_FwdIt, _Elem, _RxTraits>::_Do_digits(int _Base, int _Count) { // tr
 }
 
 template <class _FwdIt, class _Elem, class _RxTraits>
-bool _Parser<_FwdIt, _Elem, _RxTraits>::_DecimalDigits() { // check for decimal value
-    return _Do_digits(10, INT_MAX) != INT_MAX;
+bool _Parser<_FwdIt, _Elem, _RxTraits>::_DecimalDigits(
+    regex_constants::error_type _ErrorType) { // check for decimal value
+    return _Do_digits(10, INT_MAX, _ErrorType) != INT_MAX;
 }
 
 template <class _FwdIt, class _Elem, class _RxTraits>
 void _Parser<_FwdIt, _Elem, _RxTraits>::_HexDigits(int _Count) { // check for _Count hex digits
-    if (_Do_digits(16, _Count) != 0) {
+    if (_Do_digits(16, _Count, regex_constants::error_escape) != 0) {
         _Error(regex_constants::error_escape);
     }
 }
 
 template <class _FwdIt, class _Elem, class _RxTraits>
 bool _Parser<_FwdIt, _Elem, _RxTraits>::_OctalDigits() { // check for up to 3 octal digits
-    return _Do_digits(8, 3) != 3;
+    return _Do_digits(8, 3, regex_constants::error_escape) != 3;
 }
 
 template <class _FwdIt, class _Elem, class _RxTraits>
@@ -3995,7 +4000,7 @@ _Prs_ret _Parser<_FwdIt, _Elem, _RxTraits>::_ClassEscape(bool _Addit) { // check
         return _Prs_chr;
     } else if ((_L_flags & _L_esc_wsd) && _CharacterClassEscape(_Addit)) {
         return _Prs_set;
-    } else if (_DecimalDigits()) { // check for invalid value
+    } else if (_DecimalDigits(regex_constants::error_escape)) { // check for invalid value
         if (_Val != 0) {
             _Error(regex_constants::error_escape);
         }
@@ -4282,7 +4287,7 @@ bool _Parser<_FwdIt, _Elem, _RxTraits>::_CharacterEscape() { // check for valid
 
 template <class _FwdIt, class _Elem, class _RxTraits>
 void _Parser<_FwdIt, _Elem, _RxTraits>::_AtomEscape() { // check for valid atom escape
-    if ((_L_flags & _L_bckr) && _DecimalDigits()) { // check for valid back reference
+    if ((_L_flags & _L_bckr) && _DecimalDigits(regex_constants::error_backref)) { // check for valid back reference
         if (_Val == 0) { // handle \0
             if (!(_L_flags & _L_bzr_chr)) {
                 _Error(regex_constants::error_escape);
@@ -4314,7 +4319,7 @@ void _Parser<_FwdIt, _Elem, _RxTraits>::_Quantifier() { // check for quantifier
             _Max = 1;
         } else if (_Mchar == _Meta_lbr) { // check for valid bracketed value
             _Next();
-            if (!_DecimalDigits()) {
+            if (!_DecimalDigits(regex_constants::error_badbrace)) {
                 _Error(regex_constants::error_badbrace);
             }
 
@@ -4324,7 +4329,7 @@ void _Parser<_FwdIt, _Elem, _RxTraits>::_Quantifier() { // check for quantifier
             } else { // check for decimal constant following comma
                 _Next();
                 if (_Mchar != _Meta_rbr) {
-                    if (!_DecimalDigits()) {
+                    if (!_DecimalDigits(regex_constants::error_badbrace)) {
                         _Error(regex_constants::error_badbrace);
                     }
 

tests/libcxx/expected_results.txt

@@ -701,7 +701,6 @@ std/re/re.alg/re.alg.search/extended.pass.cpp FAIL
 std/re/re.alg/re.alg.search/no_update_pos.pass.cpp FAIL
 std/re/re.badexp/regex_error.pass.cpp FAIL
 std/re/re.const/re.synopt/syntax_option_type.pass.cpp FAIL
-std/re/re.grammar/excessive_brace_count.pass.cpp FAIL
 std/re/re.regex/re.regex.construct/bad_backref.pass.cpp FAIL
 std/re/re.regex/re.regex.construct/bad_escape.pass.cpp FAIL
 std/re/re.regex/re.regex.construct/bad_range.pass.cpp FAIL

tests/libcxx/skipped_tests.txt

@@ -697,7 +697,6 @@ re\re.alg\re.alg.search\extended.pass.cpp
 re\re.alg\re.alg.search\no_update_pos.pass.cpp
 re\re.badexp\regex_error.pass.cpp
 re\re.const\re.synopt\syntax_option_type.pass.cpp
-re\re.grammar\excessive_brace_count.pass.cpp
 re\re.regex\re.regex.construct\bad_backref.pass.cpp
 re\re.regex\re.regex.construct\bad_escape.pass.cpp
 re\re.regex\re.regex.construct\bad_range.pass.cpp

tests/std/test.lst

@@ -197,6 +197,7 @@ tests\GH_002039_byte_is_not_trivially_swappable
 tests\GH_002045_put_time_changes_errno
 tests\GH_002058_debug_iterator_race
 tests\GH_002120_streambuf_seekpos_and_seekoff
+tests\GH_002168_regex_overflow
 tests\GH_002299_implicit_sfinae_constraints
 tests\GH_002307_usual_scope_guard
 tests\GH_002334_branchless_clamp

tests/std/tests/GH_002168_regex_overflow/env.lst

@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\usual_matrix.lst

tests/std/tests/GH_002168_regex_overflow/test.cpp

@@ -0,0 +1,40 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <cassert>
+#include <regex>
+
+using namespace std;
+
+// GH-2168 <regex>: integer overflow on large backreference value
+int main() {
+    try {
+        // 4294967297 = 1 mod 2^32, so this will succeed if we don't check for overflow.
+        regex testRegex{R"((a)\4294967297)", regex_constants::ECMAScript};
+        assert(false);
+    } catch (const regex_error& e) {
+        assert(e.code() == regex_constants::error_backref);
+    }
+
+    try {
+        regex testRegex{"a{100000000000000000}", regex_constants::ECMAScript};
+        assert(false);
+    } catch (const regex_error& e) {
+        assert(e.code() == regex_constants::error_badbrace);
+    }
+
+    try {
+        regex testRegex{"a{100,10000000000000000}", regex_constants::ECMAScript};
+        assert(false);
+    } catch (const regex_error& e) {
+        assert(e.code() == regex_constants::error_badbrace);
+    }
+
+    try {
+        // 4294967296 = 0 mod 2^32, so this will succeed if we don't check for overflow.
+        regex testRegex{"[\\4294967296-1]", regex_constants::ECMAScript};
+        assert(false);
+    } catch (const regex_error& e) {
+        assert(e.code() == regex_constants::error_escape);
+    }
+}