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/**
* Copyright (C) 2022-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/bson/bsonobj.h"
#include "mongo/crypto/fle_crypto.h"
#include "mongo/db/fle_crud.h"
#include "mongo/db/pipeline/expression_context.h"
#include "mongo/db/query/fle/encrypted_predicate.h"
#include "mongo/db/query/fle/query_rewriter_interface.h"
namespace mongo::fle {
/**
* Class which handles traversing expressions and rewriting predicates for FLE2.
*
* The QueryRewriter is responsible for traversing Agg Expressions and MatchExpression trees and
* calling individual rewrites (subclasses of EncryptedPredicate) that have been registered for each
* encrypted index type.
*
* The actual rewrites performed are stored in references to maps in the class. In non-test
* environments, these are global maps that register encrypted predicate rewrites that live in their
* own files.
*/
class QueryRewriter : public QueryRewriterInterface {
public:
/**
* Takes in references to collection readers for the ESC that are used during tag
* computation.
*/
QueryRewriter(boost::intrusive_ptr<ExpressionContext> expCtx,
FLETagQueryInterface* tagQueryInterface,
const NamespaceString& nssEsc,
EncryptedCollScanModeAllowed mode = EncryptedCollScanModeAllowed::kAllow)
: _expCtx(expCtx),
_exprRewrites(aggPredicateRewriteMap),
_matchRewrites(matchPredicateRewriteMap),
_nssEsc(nssEsc),
_tagQueryInterface(tagQueryInterface) {
if (internalQueryFLEAlwaysUseEncryptedCollScanMode.load()) {
_mode = EncryptedCollScanMode::kForceAlways;
}
if (mode == EncryptedCollScanModeAllowed::kDisallow) {
_mode = EncryptedCollScanMode::kDisallow;
}
// This isn't the "real" query so we don't want to increment Expression
// counters here.
_expCtx->stopExpressionCounters();
}
/**
* Accepts a BSONObj holding a MatchExpression, and returns BSON representing the rewritten
* expression. Returns boost::none if no rewriting was done.
*
* Rewrites the match expression with FLE find payloads into a disjunction on the
* __safeContent__ array of tags.
*
* Will rewrite top-level $eq and $in expressions, as well as recursing through $and, $or, $not
* and $nor. Also handles similarly limited rewriting under $expr. All other MatchExpressions,
* notably $elemMatch, are ignored.
*/
boost::optional<BSONObj> rewriteMatchExpression(const BSONObj& filter);
/**
* Accepts an expression to be re-written. Will rewrite top-level expressions including $eq and
* $in, as well as recursing through other expressions. Returns a new pointer if the top-level
* expression must be changed. A nullptr indicates that the modifications happened in-place.
*/
std::unique_ptr<Expression> rewriteExpression(Expression* expression);
bool isForceEncryptedCollScan() const {
return _mode == EncryptedCollScanMode::kForceAlways;
}
void setForceEncryptedCollScanForTest() {
_mode = EncryptedCollScanMode::kForceAlways;
}
EncryptedCollScanMode getEncryptedCollScanMode() const override {
return _mode;
}
ExpressionContext* getExpressionContext() const override {
return _expCtx.get();
}
FLETagQueryInterface* getTagQueryInterface() const override {
return _tagQueryInterface;
}
const NamespaceString& getESCNss() const override {
return _nssEsc;
}
protected:
// This constructor should only be used for mocks in testing.
QueryRewriter(boost::intrusive_ptr<ExpressionContext> expCtx,
const NamespaceString& nssEsc,
const ExpressionToRewriteMap& exprRewrites,
const MatchTypeToRewriteMap& matchRewrites)
: _expCtx(expCtx),
_exprRewrites(exprRewrites),
_matchRewrites(matchRewrites),
_nssEsc(nssEsc),
_tagQueryInterface(nullptr) {}
private:
/**
* A single rewrite step, called recursively on child expressions.
*/
std::unique_ptr<MatchExpression> _rewrite(MatchExpression* me);
boost::intrusive_ptr<ExpressionContext> _expCtx;
// True if the last Expression or MatchExpression processed by this rewriter was rewritten.
bool _rewroteLastExpression = false;
// Controls how query rewriter rewrites the query
EncryptedCollScanMode _mode{EncryptedCollScanMode::kUseIfNeeded};
const ExpressionToRewriteMap& _exprRewrites;
const MatchTypeToRewriteMap& _matchRewrites;
const NamespaceString& _nssEsc;
FLETagQueryInterface* _tagQueryInterface;
};
} // namespace mongo::fle
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