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// Copyright 2024 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/url_request/referrer_policy.h"
#include <string>
#include "base/containers/adapters.h"
#include "base/containers/fixed_flat_map.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"
namespace net {
std::optional<ReferrerPolicy> ReferrerPolicyFromHeader(
std::string_view referrer_policy_header_value) {
using enum ReferrerPolicy;
const auto policy_tokens =
base::SplitStringPiece(referrer_policy_header_value, ",",
base::TRIM_WHITESPACE, base::SPLIT_WANT_NONEMPTY);
// Map from lower-cased token to ReferrerPolicy. It's good for compile speed
// to keep this sorted.
static constexpr auto kTokenToReferrerPolicy =
base::MakeFixedFlatMap<std::string_view, ReferrerPolicy>(
{{"no-referrer", NO_REFERRER},
{"no-referrer-when-downgrade",
CLEAR_ON_TRANSITION_FROM_SECURE_TO_INSECURE},
{"origin", ORIGIN},
{"origin-when-cross-origin", ORIGIN_ONLY_ON_TRANSITION_CROSS_ORIGIN},
{"same-origin", CLEAR_ON_TRANSITION_CROSS_ORIGIN},
{"strict-origin",
ORIGIN_CLEAR_ON_TRANSITION_FROM_SECURE_TO_INSECURE},
{"strict-origin-when-cross-origin",
REDUCE_GRANULARITY_ON_TRANSITION_CROSS_ORIGIN},
{"unsafe-url", NEVER_CLEAR}});
// Per https://w3c.github.io/webappsec-referrer-policy/#unknown-policy-values,
// use the last recognized policy value, and ignore unknown policies.
for (const auto& token : base::Reversed(policy_tokens)) {
const std::string lowered_token = base::ToLowerASCII(token);
const auto it = kTokenToReferrerPolicy.find(lowered_token);
if (it != kTokenToReferrerPolicy.end()) {
return it->second;
}
}
return std::nullopt;
}
} // namespace net
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