Use Google RE2 as underlying regex engine

This introduces guaranteed upper bounds for memory usage and
CPU time during regex evaluation. Most importantly, it removes
the danger of catastrophic backtracking that is currrently
present in GCC's std::regex implementation.

With this commit, RE2 will be used instead of std::regex for:
* Document selection regex/glob operators
* Attribute regex search
* Evaluation of mTLS authorization rules

6 files changed, 14 insertions, 17 deletions

diff --git a/searchlib/src/vespa/searchlib/attribute/attribute_blueprint_factory.cpp b/searchlib/src/vespa/searchlib/attribute/attribute_blueprint_factory.cpp
index 9af05059bef..14d33914d05 100644
--- a/searchlib/src/vespa/searchlib/attribute/attribute_blueprint_factory.cpp
+++ b/searchlib/src/vespa/searchlib/attribute/attribute_blueprint_factory.cpp
@@ -519,12 +519,12 @@ public:
 
     void visit(StringTerm & n) override { visitTerm(n, true); }
     void visit(SubstringTerm & n) override {
-        query::SimpleRegExpTerm re(vespalib::Regexp::make_from_substring(n.getTerm()),
+        query::SimpleRegExpTerm re(vespalib::RegexpUtil::make_from_substring(n.getTerm()),
                                    n.getView(), n.getId(), n.getWeight());
         visitTerm(re);
     }
     void visit(SuffixTerm & n) override {
-        query::SimpleRegExpTerm re(vespalib::Regexp::make_from_suffix(n.getTerm()),
+        query::SimpleRegExpTerm re(vespalib::RegexpUtil::make_from_suffix(n.getTerm()),
                                    n.getView(), n.getId(), n.getWeight());
         visitTerm(re);
     }
diff --git a/searchlib/src/vespa/searchlib/attribute/multistringattribute.hpp b/searchlib/src/vespa/searchlib/attribute/multistringattribute.hpp
index 6cefc03dd70..eafa5bf0e1f 100644
--- a/searchlib/src/vespa/searchlib/attribute/multistringattribute.hpp
+++ b/searchlib/src/vespa/searchlib/attribute/multistringattribute.hpp
@@ -123,7 +123,7 @@ StringTemplSearchContext(QueryTermSimpleUP qTerm, const AttrType & toBeSearched)
             auto comp = enumStore.make_folded_comparator(queryTerm()->getTerm(), true);
             lookupRange(comp, comp);
         } else if (this->isRegex()) {
-            vespalib::string prefix(vespalib::Regexp::get_prefix(this->queryTerm()->getTerm()));
+            vespalib::string prefix(vespalib::RegexpUtil::get_prefix(this->queryTerm()->getTerm()));
             auto comp = enumStore.make_folded_comparator(prefix.c_str(), true);
             lookupRange(comp, comp);
         } else {
diff --git a/searchlib/src/vespa/searchlib/attribute/postinglistsearchcontext.h b/searchlib/src/vespa/searchlib/attribute/postinglistsearchcontext.h
index 43d8b7ce9d2..e94de44e45b 100644
--- a/searchlib/src/vespa/searchlib/attribute/postinglistsearchcontext.h
+++ b/searchlib/src/vespa/searchlib/attribute/postinglistsearchcontext.h
@@ -183,14 +183,14 @@ private:
     using PostingList = typename AggregationTraits::PostingList;
     using Parent = PostingSearchContext<BaseSC, PostingListFoldedSearchContextT<DataT>, AttrT>;
     using FoldedComparatorType = typename Parent::EnumStore::FoldedComparatorType;
-    using Regexp = vespalib::Regexp;
+    using RegexpUtil = vespalib::RegexpUtil;
     using QueryTermSimpleUP = typename Parent::QueryTermSimpleUP;
     using Parent::_toBeSearched;
     using Parent::_enumStore;
     using Parent::isRegex;
     using Parent::getRegex;
     bool useThis(const PostingListSearchContext::DictionaryConstIterator & it) const override {
-        return isRegex() ? (getRegex() ? std::regex_search(_enumStore.get_value(it.getKey()), *getRegex()) : false ) : true;
+        return isRegex() ? (getRegex() ? getRegex()->partial_match(_enumStore.get_value(it.getKey())) : false ) : true;
     }
 public:
     StringPostingSearchContext(QueryTermSimpleUP qTerm, bool useBitVector, const AttrT &toBeSearched);
@@ -288,7 +288,7 @@ StringPostingSearchContext(QueryTermSimpleUP qTerm, bool useBitVector, const Att
             auto comp = _enumStore.make_folded_comparator(this->queryTerm()->getTerm(), true);
             this->lookupRange(comp, comp);
         } else if (this->isRegex()) {
-            vespalib::string prefix(Regexp::get_prefix(this->queryTerm()->getTerm()));
+            vespalib::string prefix(RegexpUtil::get_prefix(this->queryTerm()->getTerm()));
             auto comp = _enumStore.make_folded_comparator(prefix.c_str(), true);
             this->lookupRange(comp, comp);
         } else {
diff --git a/searchlib/src/vespa/searchlib/attribute/singlestringattribute.hpp b/searchlib/src/vespa/searchlib/attribute/singlestringattribute.hpp
index 214da6bf230..406cbbbe447 100644
--- a/searchlib/src/vespa/searchlib/attribute/singlestringattribute.hpp
+++ b/searchlib/src/vespa/searchlib/attribute/singlestringattribute.hpp
@@ -59,7 +59,7 @@ SingleValueStringAttributeT<B>::StringTemplSearchContext::StringTemplSearchConte
             auto comp = enumStore.make_folded_comparator(queryTerm()->getTerm(), true);
             lookupRange(comp, comp);
         } else if (this->isRegex()) {
-            vespalib::string prefix(vespalib::Regexp::get_prefix(this->queryTerm()->getTerm()));
+            vespalib::string prefix(vespalib::RegexpUtil::get_prefix(this->queryTerm()->getTerm()));
             auto comp = enumStore.make_folded_comparator(prefix.c_str(), true);
             lookupRange(comp, comp);
         } else {
diff --git a/searchlib/src/vespa/searchlib/attribute/stringbase.cpp b/searchlib/src/vespa/searchlib/attribute/stringbase.cpp
index d7523c86e29..32b5b3ca373 100644
--- a/searchlib/src/vespa/searchlib/attribute/stringbase.cpp
+++ b/searchlib/src/vespa/searchlib/attribute/stringbase.cpp
@@ -231,10 +231,7 @@ StringAttribute::StringSearchContext::StringSearchContext(QueryTermSimple::UP qT
     _regex()
 {
     if (isRegex()) {
-        try {
-            _regex = std::regex(_queryTerm->getTerm(), std::regex::icase);
-        } catch (std::regex_error &) {
-        }
+        _regex = vespalib::Regex::from_pattern(_queryTerm->getTerm(), vespalib::Regex::Options::IgnoreCase);
     }
 }
 
diff --git a/searchlib/src/vespa/searchlib/attribute/stringbase.h b/searchlib/src/vespa/searchlib/attribute/stringbase.h
index cf0a92253de..3518544cbdc 100644
--- a/searchlib/src/vespa/searchlib/attribute/stringbase.h
+++ b/searchlib/src/vespa/searchlib/attribute/stringbase.h
@@ -9,10 +9,10 @@
 #include <vespa/searchlib/attribute/i_enum_store.h>
 #include <vespa/searchlib/attribute/loadedenumvalue.h>
 #include <vespa/searchlib/util/foldedstringcompare.h>
+#include <vespa/vespalib/regex/regex.h>
 #include <vespa/vespalib/text/lowercase.h>
 #include <vespa/vespalib/text/utf8.h>
 #include <optional>
-#include <regex>
 
 namespace search {
 
@@ -103,7 +103,7 @@ protected:
         const QueryTermUCS4 * queryTerm() const override;
         bool isMatch(const char *src) const {
             if (__builtin_expect(isRegex(), false)) {
-                return _regex ? std::regex_search(src, *_regex) : false;
+                return _regex ? _regex->partial_match(std::string_view(src)) : false;
             }
             vespalib::Utf8ReaderForZTS u8reader(src);
             uint32_t j = 0;
@@ -162,7 +162,7 @@ protected:
         bool  isRegex() const { return _isRegex; }
         QueryTermSimpleUP         _queryTerm;
         std::vector<ucs4_t>       _termUCS4;
-        const std::optional<std::regex>& getRegex() const { return _regex; }
+        const std::optional<vespalib::Regex>& getRegex() const { return _regex; }
     private:
         WeightedConstChar * getBuffer() const {
             if (_buffer == nullptr) {
@@ -170,9 +170,9 @@ protected:
             }
             return _buffer;
         }
-        unsigned                    _bufferLen;
-        mutable WeightedConstChar * _buffer;
-        std::optional<std::regex>   _regex;
+        unsigned                       _bufferLen;
+        mutable WeightedConstChar *    _buffer;
+        std::optional<vespalib::Regex> _regex;
     };
 private:
     SearchContext::UP getSearch(QueryTermSimpleUP term, const attribute::SearchContextParams & params) const override;