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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.
*/
#include <boost/optional.hpp>
#include "mongo/crypto/fle_crypto.h"
#include "mongo/crypto/fle_tags.h"
#include "mongo/db/query/query_knobs_gen.h"
namespace mongo::fle {
using DerivedToken = FLEDerivedFromDataTokenAndContentionFactorTokenGenerator;
using TwiceDerived = FLETwiceDerivedTokenGenerator;
size_t sizeArrayElementsMemory(size_t tagCount);
namespace {
inline constexpr size_t arrayElementSize(int digits) {
constexpr size_t sizeOfType = 1;
constexpr size_t sizeOfBinDataLength = 4;
constexpr size_t sizeOfNullMarker = 1;
constexpr size_t sizeOfSubType = 1;
constexpr size_t sizeOfData = sizeof(PrfBlock);
return sizeOfType + sizeOfBinDataLength + sizeOfNullMarker + digits + sizeOfSubType +
sizeOfData;
}
void verifyTagsWillFit(size_t tagCount, size_t memoryLimit) {
constexpr size_t largestElementSize = arrayElementSize(std::numeric_limits<size_t>::digits10);
constexpr size_t ridiculousNumberOfTags =
std::numeric_limits<size_t>::max() / largestElementSize;
uassert(6653300, "Encrypted rewrite too many tags", tagCount < ridiculousNumberOfTags);
uassert(6401800,
"Encrypted rewrite memory limit exceeded",
sizeArrayElementsMemory(tagCount) <= memoryLimit);
}
} // namespace
size_t sizeArrayElementsMemory(size_t tagCount) {
size_t size = 0;
size_t power = 1;
size_t digits = 1;
size_t accountedTags = 0;
while (tagCount >= power) {
power *= 10;
size_t count = std::min(tagCount, power) - accountedTags;
size += arrayElementSize(digits) * count;
accountedTags += count;
digits++;
}
return size;
}
// The algorithm for constructing a list of tags matching an equality predicate on an encrypted
// field is as follows:
//
// (1) Query ESC to obtain the counter value (n) after the most recent insert.
// (2) Query ECC for a null document.
// (a) A null document means there has been at least one compaction of ECC.
// (b) No null document means there has not been a compaction. Therefore we have to check all
// the tags from 1..n to see if they have been deleted.
// (3) Return the surviving set of tags from 1..n (encrypted).
//
// Given:
// s: ESCDerivedFromDataToken
// c: ECCDerivedFromDataToken
// d: EDCDerivedFromDataToken
// Do:
// n = ESC::emuBinary(s)
// deletedTags = []
// pos = ECC::nullDocument(c) ? ECC::nullDocument(c).position : 1
// while true {
// if (doc = ECC::getDocument(c, pos); doc != null) {
// deletedTags = [doc | deletedTags]
// } else {
// break
// }
// pos++
// }
// return [EDC::encrypt(i) | i in [1..n] where i not in deletedTags]
std::vector<PrfBlock> readTagsWithContention(const FLEStateCollectionReader& esc,
const FLEStateCollectionReader& ecc,
ESCDerivedFromDataToken s,
ECCDerivedFromDataToken c,
EDCDerivedFromDataToken d,
uint64_t cf,
size_t memoryLimit,
std::vector<PrfBlock>&& binaryTags) {
auto escTok = DerivedToken::generateESCDerivedFromDataTokenAndContentionFactorToken(s, cf);
auto escTag = TwiceDerived::generateESCTwiceDerivedTagToken(escTok);
auto escVal = TwiceDerived::generateESCTwiceDerivedValueToken(escTok);
auto eccTok = DerivedToken::generateECCDerivedFromDataTokenAndContentionFactorToken(c, cf);
auto eccTag = TwiceDerived::generateECCTwiceDerivedTagToken(eccTok);
auto eccVal = TwiceDerived::generateECCTwiceDerivedValueToken(eccTok);
auto edcTok = DerivedToken::generateEDCDerivedFromDataTokenAndContentionFactorToken(d, cf);
auto edcTag = TwiceDerived::generateEDCTwiceDerivedToken(edcTok);
// (1) Query ESC for the counter value after the most recent insert.
// 0 => 0 inserts for this field value pair.
// n => n inserts for this field value pair.
// none => compaction => query ESC for null document to find # of inserts.
auto insertCounter = ESCCollection::emuBinary(esc, escTag, escVal);
if (insertCounter && insertCounter.get() == 0) {
return std::move(binaryTags);
}
auto numInserts = insertCounter
? uassertStatusOK(
ESCCollection::decryptDocument(
escVal, esc.getById(ESCCollection::generateId(escTag, insertCounter))))
.count
: uassertStatusOK(ESCCollection::decryptNullDocument(
escVal, esc.getById(ESCCollection::generateId(escTag, boost::none))))
.count;
// (2) Query ECC for a null document.
auto eccNullDoc = ecc.getById(ECCCollection::generateId(eccTag, boost::none));
auto pos = eccNullDoc.isEmpty()
? 1
: uassertStatusOK(ECCCollection::decryptNullDocument(eccVal, eccNullDoc)).position + 2;
std::vector<ECCDocument> deletes;
// (2) Search ECC for deleted tag(counter) values.
while (true) {
auto eccObj = ecc.getById(ECCCollection::generateId(eccTag, pos));
if (eccObj.isEmpty()) {
break;
}
auto eccDoc = uassertStatusOK(ECCCollection::decryptDocument(eccVal, eccObj));
// Compaction placeholders only present for positive contention factors (cm).
if (eccDoc.valueType == ECCValueType::kCompactionPlaceholder) {
break;
}
// Note, in the worst case where no compactions have occurred, the deletes vector will grow
// proportionally to the number of deletes. This is not likely to present a significant
// problem but we should still track the memory we consume here.
deletes.emplace_back(eccDoc);
pos++;
}
std::sort(deletes.begin(), deletes.end());
auto numDeletes = std::accumulate(deletes.begin(), deletes.end(), 0, [](auto acc, auto eccDoc) {
return acc + eccDoc.end - eccDoc.start + 1;
});
auto cumTagCount = binaryTags.size() + numInserts - numDeletes;
verifyTagsWillFit(cumTagCount, memoryLimit);
for (uint64_t i = 1; i <= numInserts; i++) {
if (auto it = std::lower_bound(
deletes.begin(),
deletes.end(),
i,
[](ECCDocument& eccDoc, uint64_t tag) { return eccDoc.end < tag; });
it != deletes.end() && it->start <= i && i <= it->end) {
continue;
}
// (3) Return the surviving set of tags from 1..n (encrypted).
binaryTags.emplace_back(EDCServerCollection::generateTag(edcTag, i));
}
return std::move(binaryTags);
}
// A positive contention factor (cm) means we must run the above algorithm (cm) times.
std::vector<PrfBlock> readTags(const FLEStateCollectionReader& esc,
const FLEStateCollectionReader& ecc,
ESCDerivedFromDataToken s,
ECCDerivedFromDataToken c,
EDCDerivedFromDataToken d,
boost::optional<int64_t> cm) {
// The output of readTags will be used as the argument to a $in expression, so make sure we
// don't exceed the configured memory limit.
auto limit = static_cast<size_t>(internalQueryFLERewriteMemoryLimit.load());
if (!cm || cm.get() == 0) {
auto binaryTags = readTagsWithContention(esc, ecc, s, c, d, 0, limit, {});
}
std::vector<PrfBlock> binaryTags;
for (auto i = 0; i <= cm.get(); i++) {
binaryTags = readTagsWithContention(esc, ecc, s, c, d, i, limit, std::move(binaryTags));
}
return binaryTags;
}
} // namespace mongo::fle
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