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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/optimization_guide/core/model_execution/redactor.h"
#include <algorithm>
#include "base/containers/heap_array.h"
#include "base/debug/dump_without_crashing.h"
#include "base/memory/ptr_util.h"
#include "base/strings/strcat.h"
#include "base/strings/string_number_conversions.h"
#include "components/optimization_guide/proto/redaction.pb.h"
#include "third_party/re2/src/re2/re2.h"
namespace optimization_guide {
Redactor::Rule::Rule(std::unique_ptr<re2::RE2> re,
Redactor::Behavior behavior,
std::string replacement_string,
int matching_group,
size_t min_pattern_length,
size_t max_pattern_length)
: re_(std::move(re)),
behavior_(behavior),
replacement_string_(replacement_string),
matching_group_(matching_group),
min_pattern_length_(min_pattern_length),
max_pattern_length_(max_pattern_length) {}
Redactor::Rule::Rule(Rule&& r) = default;
Redactor::Rule::~Rule() = default;
Redactor::Redactor(std::vector<Rule>&& rules) {
rules_.swap(rules);
}
Redactor::~Redactor() = default;
// static
Redactor Redactor::FromProto(const proto::RedactRules& proto_rules) {
std::vector<Redactor::Rule> rules;
for (const auto& proto_rule : proto_rules.rules()) {
if (proto_rule.regex().empty() ||
proto_rule.group_index() < 0 || proto_rule.min_pattern_length() < 0 ||
proto_rule.max_pattern_length() < 0) {
base::debug::DumpWithoutCrashing();
continue;
}
Behavior behavior = Redactor::Behavior::kReject;
switch (proto_rule.behavior()) {
case proto::RedactBehavior::REJECT:
behavior = Redactor::Behavior::kReject;
break;
case proto::RedactBehavior::REDACT_IF_ONLY_IN_OUTPUT:
behavior = Redactor::Behavior::kRedactIfOnlyInOutput;
break;
case proto::RedactBehavior::REDACT_ALWAYS:
behavior = Redactor::Behavior::kRedactAlways;
break;
default:
base::debug::DumpWithoutCrashing();
continue;
}
auto re = std::make_unique<re2::RE2>(proto_rule.regex());
if (!re->ok() || re->NumberOfCapturingGroups() < proto_rule.group_index()) {
base::debug::DumpWithoutCrashing();
continue;
}
rules.emplace_back(std::move(re), behavior, proto_rule.replacement_string(),
proto_rule.group_index(),
proto_rule.min_pattern_length(),
proto_rule.max_pattern_length());
}
return Redactor(std::move(rules));
}
RedactResult Redactor::Redact(const std::string& input,
std::string& output) const {
for (auto& rule : rules_) {
if (rule.Process(input, output) == RedactResult::kReject) {
return RedactResult::kReject;
}
}
return RedactResult::kContinue;
}
RedactResult Redactor::Rule::Process(const std::string& input,
std::string& output) const {
std::string_view output_view(output);
const int group = matching_group_;
// The first match gives the whole region.
auto matches = base::HeapArray<std::string_view>::WithSize(group + 1);
size_t last_match_start = 0;
std::string new_output;
size_t next_start_offset = 0;
while (next_start_offset < output_view.length() &&
re_->Match(output_view, next_start_offset, output_view.length(),
re2::RE2::UNANCHORED, matches.data(), group + 1)) {
const std::string_view& match(matches[group]);
if (IsValidMatch(match)) {
if (behavior_ == Redactor::Behavior::kReject) {
return RedactResult::kReject;
}
if (behavior_ == Redactor::Behavior::kRedactAlways ||
input.find(match) == std::string::npos) {
const size_t match_start_offset_in_output =
match.data() - output_view.data();
new_output +=
base::StrCat({std::string_view(output).substr(
last_match_start,
match_start_offset_in_output - last_match_start),
GetReplacementString(match)});
last_match_start = match_start_offset_in_output + match.length();
}
}
// Always skip the match even if not valid. If this only skipped the first
// character on an invalid match, then the shortening might trigger a match.
// It's possible for a regex to match, but the length is zero. Ensure we
// skip at least 1 character, otherwise this code could loop infinitely.
next_start_offset = match.data() - output_view.data() +
std::max(static_cast<size_t>(1), match.length());
}
if (last_match_start == 0) {
// No replacement happened, nothing to do.
return RedactResult::kContinue;
}
if (last_match_start != output.length()) {
new_output += output.substr(last_match_start);
}
std::swap(output, new_output);
return RedactResult::kContinue;
}
std::string Redactor::Rule::GetReplacementString(std::string_view match) const {
if (!replacement_string_.empty()) {
return replacement_string_;
}
std::string replacement(match.length() + 2, '#');
replacement[0] = '[';
replacement.back() = ']';
return replacement;
}
bool Redactor::Rule::IsValidMatch(const std::string_view& match) const {
if (match.empty()) {
return false;
}
if (match.length() < min_pattern_length_) {
return false;
}
if (max_pattern_length_ && match.length() > max_pattern_length_) {
return false;
}
return true;
}
} // namespace optimization_guide
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