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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "chrome/browser/net/secure_dns_policy_handler.h"
#include <string>
#include <string_view>
#include "base/strings/string_number_conversions.h"
#include "base/values.h"
#include "chrome/browser/net/secure_dns_config.h"
#include "chrome/browser/prefs/session_startup_pref.h"
#include "chrome/common/pref_names.h"
#include "components/policy/core/browser/policy_error_map.h"
#include "components/policy/core/common/policy_map.h"
#include "components/policy/policy_constants.h"
#include "components/prefs/pref_value_map.h"
#include "components/strings/grit/components_strings.h"
#include "net/dns/public/dns_over_https_config.h"
#include "net/dns/public/util.h"
#if BUILDFLAG(IS_CHROMEOS)
#include "ash/constants/ash_features.h"
#endif
namespace {
#if BUILDFLAG(IS_CHROMEOS)
constexpr int kMinDohSaltSize = 8;
constexpr int kMaxDohSaltSize = 32;
// Returns true if the policy `kDnsOverHttpsSalt` is not set or if it has a
// valid value, otherwise returns false. kDnsOverHttpsSalt` is only valid if
// `kDnsOverHttpsTemplatesWithIdentifiers` is set. If an error occurs, the error
// message will be appended to `errors`.
bool CheckDnsOverHttpsSaltPolicy(const policy::PolicyMap& policies,
policy::PolicyErrorMap* errors) {
if (!policies.IsPolicySet(policy::key::kDnsOverHttpsSalt)) {
return true;
}
const base::Value* salt =
policies.GetValueUnsafe(policy::key::kDnsOverHttpsSalt);
if (!salt->is_string()) {
errors->AddError(policy::key::kDnsOverHttpsSalt,
IDS_POLICY_SECURE_DNS_SALT_INVALID_ERROR);
return false;
}
// Salt is optional.
if (salt->GetString().empty()) {
return true;
}
if (salt->GetString().size() < kMinDohSaltSize ||
salt->GetString().size() > kMaxDohSaltSize) {
errors->AddError(policy::key::kDnsOverHttpsSalt,
IDS_POLICY_SECURE_DNS_SALT_INVALID_SIZE_ERROR);
return false;
}
bool templates_set = false;
if (policies.IsPolicySet(
policy::key::kDnsOverHttpsTemplatesWithIdentifiers)) {
const base::Value* templates =
policies.GetValue(policy::key::kDnsOverHttpsTemplatesWithIdentifiers,
base::Value::Type::STRING);
templates_set = templates && !templates->GetString().empty();
}
if (!templates_set) {
errors->AddError(policy::key::kDnsOverHttpsSalt,
IDS_POLICY_DEPENDENCY_ERROR_ANY_VALUE,
policy::key::kDnsOverHttpsTemplatesWithIdentifiers);
return false;
}
return true;
}
#endif
// Returns true if the policy `policy_name` has a valid template URI value,
// otherwise returns false. If an error occurs, the error message will be
// appended to `errors`.
bool CheckDnsOverHttpsTemplatePolicy(const policy::PolicyMap& policies,
policy::PolicyErrorMap* errors,
const std::string& policy_name,
std::string_view mode) {
// It is safe to use `GetValueUnsafe()` because type checking is performed
// before the value is used.
const base::Value* templates = policies.GetValueUnsafe(policy_name);
if (!templates)
return false;
if (!templates->is_string()) {
errors->AddError(policy_name, IDS_POLICY_TYPE_ERROR,
base::Value::GetTypeName(base::Value::Type::STRING));
return false;
}
if (templates->GetString().empty())
return false;
const std::string& templates_str = templates->GetString();
if (!net::DnsOverHttpsConfig::FromString(templates_str)) {
errors->AddError(policy_name,
IDS_POLICY_SECURE_DNS_TEMPLATES_INVALID_ERROR);
}
return true;
}
} // namespace
namespace policy {
SecureDnsPolicyHandler::SecureDnsPolicyHandler() = default;
SecureDnsPolicyHandler::~SecureDnsPolicyHandler() = default;
// Verifies if the combination of policies which set the secure DNS mode and
// the templates URI is valid. The templates URIs can be set via the cross
// platform policy "DnsOverHttpsTemplates" and, on Chrome OS only, via the
// policy "DnsOverHttpsTemplatesWithIdentifiers" which will override the cross
// platform policy if both are set.
bool SecureDnsPolicyHandler::CheckPolicySettings(const PolicyMap& policies,
PolicyErrorMap* errors) {
bool mode_is_applicable = true;
bool templates_is_applicable = true;
std::string applicable_template_policy_name = key::kDnsOverHttpsTemplates;
// It is safe to use `GetValueUnsafe()` because type checking is performed
// before the value is used.
const base::Value* mode = policies.GetValueUnsafe(key::kDnsOverHttpsMode);
std::string_view mode_str;
if (!mode) {
mode_is_applicable = false;
} else if (!mode->is_string()) {
errors->AddError(key::kDnsOverHttpsMode, IDS_POLICY_TYPE_ERROR,
base::Value::GetTypeName(base::Value::Type::STRING));
mode_is_applicable = false;
} else {
// Mode is set and is a string.
mode_str = mode->GetString();
if (mode_str.size() == 0) {
errors->AddError(key::kDnsOverHttpsMode, IDS_POLICY_NOT_SPECIFIED_ERROR);
mode_is_applicable = false;
} else if (!SecureDnsConfig::ParseMode(mode_str)) {
errors->AddError(key::kDnsOverHttpsMode,
IDS_POLICY_INVALID_SECURE_DNS_MODE_ERROR);
mode_is_applicable = false;
}
}
is_templates_policy_valid_ = CheckDnsOverHttpsTemplatePolicy(
policies, errors, key::kDnsOverHttpsTemplates, mode_str);
templates_is_applicable = is_templates_policy_valid_;
#if BUILDFLAG(IS_CHROMEOS)
bool templates_valid = CheckDnsOverHttpsTemplatePolicy(
policies, errors, key::kDnsOverHttpsTemplatesWithIdentifiers, mode_str);
bool salt_valid = CheckDnsOverHttpsSaltPolicy(policies, errors);
is_templates_with_identifiers_policy_valid_ = templates_valid && salt_valid;
templates_is_applicable =
is_templates_policy_valid_ || is_templates_with_identifiers_policy_valid_;
if (is_templates_with_identifiers_policy_valid_) {
applicable_template_policy_name =
key::kDnsOverHttpsTemplatesWithIdentifiers;
}
#endif
if (IsTemplatesPolicyNotSpecified(templates_is_applicable, mode_str)) {
errors->AddError(applicable_template_policy_name,
IDS_POLICY_SECURE_DNS_TEMPLATES_NOT_SPECIFIED_ERROR);
}
if (templates_is_applicable) {
if (!mode) {
errors->AddError(applicable_template_policy_name,
IDS_POLICY_SECURE_DNS_TEMPLATES_UNSET_MODE_ERROR);
} else if (!mode_is_applicable) {
errors->AddError(applicable_template_policy_name,
IDS_POLICY_SECURE_DNS_TEMPLATES_INVALID_MODE_ERROR);
} else if (mode_str == SecureDnsConfig::kModeOff) {
errors->AddError(applicable_template_policy_name,
IDS_POLICY_SECURE_DNS_TEMPLATES_IRRELEVANT_MODE_ERROR);
}
}
return mode_is_applicable || templates_is_applicable;
}
void SecureDnsPolicyHandler::ApplyPolicySettings(const PolicyMap& policies,
PrefValueMap* prefs) {
const base::Value* mode =
policies.GetValue(key::kDnsOverHttpsMode, base::Value::Type::STRING);
std::string_view mode_str;
if (mode) {
mode_str = mode->GetString();
prefs->SetString(prefs::kDnsOverHttpsMode,
SecureDnsConfig::ParseMode(mode_str)
? std::string(mode_str)
: SecureDnsConfig::kModeOff);
}
const base::Value* templates =
policies.GetValue(key::kDnsOverHttpsTemplates, base::Value::Type::STRING);
// A templates not specified error means that the pref should be set blank.
if (IsTemplatesPolicyNotSpecified(is_templates_policy_valid_, mode_str))
prefs->SetString(prefs::kDnsOverHttpsTemplates, std::string());
else if (is_templates_policy_valid_)
prefs->SetString(prefs::kDnsOverHttpsTemplates, templates->GetString());
#if BUILDFLAG(IS_CHROMEOS)
const base::Value* templates_with_identifiers = policies.GetValue(
key::kDnsOverHttpsTemplatesWithIdentifiers, base::Value::Type::STRING);
const base::Value* salt =
policies.GetValue(key::kDnsOverHttpsSalt, base::Value::Type::STRING);
// A templates not specified error means that the pref should be set blank.
if (IsTemplatesPolicyNotSpecified(is_templates_with_identifiers_policy_valid_,
mode_str)) {
prefs->SetString(prefs::kDnsOverHttpsTemplatesWithIdentifiers,
std::string());
prefs->SetString(prefs::kDnsOverHttpsSalt, std::string());
} else if (is_templates_with_identifiers_policy_valid_) {
prefs->SetString(prefs::kDnsOverHttpsTemplatesWithIdentifiers,
templates_with_identifiers->GetString());
prefs->SetString(prefs::kDnsOverHttpsSalt,
salt ? salt->GetString() : std::string());
}
#endif
}
bool SecureDnsPolicyHandler::IsTemplatesPolicyNotSpecified(
bool is_templates_policy_valid,
std::string_view mode_str) {
if (mode_str == SecureDnsConfig::kModeSecure)
return !is_templates_policy_valid;
return false;
}
} // namespace policy
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