net/http/transport_security_state.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_HTTP_TRANSPORT_SECURITY_STATE_H_
#define NET_HTTP_TRANSPORT_SECURITY_STATE_H_

#include <stdint.h>

#include <array>
#include <map>
#include <optional>
#include <set>
#include <string>
#include <string_view>

#include "base/feature_list.h"
#include "base/functional/callback.h"
#include "base/gtest_prod_util.h"
#include "base/memory/raw_ptr.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
#include "base/values.h"
#include "crypto/sha2.h"
#include "net/base/expiring_cache.h"
#include "net/base/hash_value.h"
#include "net/base/net_export.h"
#include "net/base/network_anonymization_key.h"
#include "net/cert/signed_certificate_timestamp_and_status.h"
#include "net/http/transport_security_state_source.h"
#include "net/log/net_log_with_source.h"
#include "url/gurl.h"

namespace net {

namespace ct {
enum class CTPolicyCompliance;
}

class HostPortPair;
class X509Certificate;

void NET_EXPORT_PRIVATE SetTransportSecurityStateSourceForTesting(
    const TransportSecurityStateSource* source);

// Whether an insecure connection should be upgraded to use SSL. For metrics
// this includes whether the decision came from static or dynamic state.
enum class SSLUpgradeDecision {
  // No state indicated an upgrade.
  kNoUpgrade,
  // Dynamic state indicated an upgrade.
  kDynamicUpgrade,
  // Static state indicated an upgrade. If dynamic state existed, it gave the
  // same result as the static state.
  kStaticUpgrade,
};

// Tracks which hosts have enabled strict transport security and/or public
// key pins.
//
// This object manages the in-memory store. Register a Delegate with
// |SetDelegate| to persist the state to disk.
//
// HTTP strict transport security (HSTS) is defined in
// http://tools.ietf.org/html/ietf-websec-strict-transport-sec.
class NET_EXPORT TransportSecurityState {
 public:
  using HashedHost = std::array<uint8_t, crypto::kSHA256Length>;

  class NET_EXPORT Delegate {
   public:
    // This function may not block and may be called with internal locks held.
    // Thus it must not reenter the TransportSecurityState object.
    virtual void StateIsDirty(TransportSecurityState* state) = 0;
    // Same as StateIsDirty but instructs the Delegate to persist the data
    // immediately and call |callback| when done.
    virtual void WriteNow(TransportSecurityState* state,
                          base::OnceClosure callback) = 0;

   protected:
    virtual ~Delegate() = default;
  };

  class NET_EXPORT RequireCTDelegate {
   public:
    // Provides a capability for altering the default handling of Certificate
    // Transparency information, allowing it to be always required for some
    // hosts, for some hosts to be opted out of the default policy, or
    // allowing the TransportSecurityState to apply the default security
    // policies.
    enum class CTRequirementLevel {
      // The host is required to always supply Certificate Transparency
      // information that complies with the CT policy.
      REQUIRED,

      // The host is explicitly not required to supply Certificate
      // Transparency information that complies with the CT policy.
      NOT_REQUIRED,
    };

    // Called by the TransportSecurityState, allows the Delegate to override
    // the default handling of Certificate Transparency requirements, if
    // desired.
    // |hostname| contains the host being contacted, serving the certificate
    // |chain|, with the set of hashesh |hashes|. Note that |hashes| and
    // |chain| are not guaranteed to be in the same order - that is, the first
    // hash in |hashes| is NOT guaranteed to be for the leaf cert in |chain|.
    virtual CTRequirementLevel IsCTRequiredForHost(
        std::string_view hostname,
        const X509Certificate* chain,
        const HashValueVector& hashes) = 0;

   protected:
    virtual ~RequireCTDelegate() = default;
  };

  // A STSState describes the strict transport security state (required
  // upgrade to HTTPS).
  class NET_EXPORT STSState {
   public:
    enum UpgradeMode {
      // These numbers must match those in hsts_view.js, function modeToString.
      MODE_FORCE_HTTPS = 0,
      MODE_DEFAULT = 1,
    };

    STSState();
    ~STSState();

    // The absolute time (UTC) when the |upgrade_mode| (and other state) was
    // observed.
    base::Time last_observed;

    // The absolute time (UTC) when |upgrade_mode| (and other state)
    // expires.
    base::Time expiry;

    UpgradeMode upgrade_mode = MODE_DEFAULT;

    // Are subdomains subject to this policy state?
    bool include_subdomains = false;

    // The domain which matched during a search for this STSState entry.
    // Updated by |GetDynamicSTSState| and |GetStaticDomainState|.
    std::string domain;

    // ShouldUpgradeToSSL returns true iff HTTP requests should be internally
    // redirected to HTTPS (also if WS should be upgraded to WSS).
    bool ShouldUpgradeToSSL() const;
  };

  class NET_EXPORT STSStateIterator {
   public:
    explicit STSStateIterator(const TransportSecurityState& state);
    ~STSStateIterator();

    bool HasNext() const { return iterator_ != end_; }
    void Advance() { ++iterator_; }
    const HashedHost& hostname() const { return iterator_->first; }
    const STSState& domain_state() const { return iterator_->second; }

   private:
    std::map<HashedHost, STSState>::const_iterator iterator_;
    std::map<HashedHost, STSState>::const_iterator end_;
  };

  // PKPStatus describes the result of a pinning check.
  enum class PKPStatus {
    // Pinning was enabled and the necessary pins were not present.
    VIOLATED,

    // Pinning was not enabled, or pinning was enabled and the certificate
    // satisfied the pins.
    OK,

    // Pinning was enabled and the certificate did not satisfy the pins, but the
    // violation was ignored due to local policy, such as a local trust anchor.
    BYPASSED,
  };

  // A PKPState describes the public key pinning state.
  class NET_EXPORT PKPState {
   public:
    PKPState();
    PKPState(const PKPState& other);
    ~PKPState();

    // The absolute time (UTC) when the |spki_hashes| (and other state) were
    // observed.
    base::Time last_observed;

    // The absolute time (UTC) when the |spki_hashes| expire.
    base::Time expiry;

    // Optional; hashes of pinned SubjectPublicKeyInfos.
    HashValueVector spki_hashes;

    // Optional; hashes of static known-bad SubjectPublicKeyInfos which MUST
    // NOT intersect with the set of SPKIs in the TLS server's certificate
    // chain.
    HashValueVector bad_spki_hashes;

    // Are subdomains subject to this policy state?
    bool include_subdomains = false;

    // The domain which matched during a search for this DomainState entry.
    // Updated by |GetDynamicPKPState| and |GetStaticDomainState|.
    std::string domain;

    // Takes a set of SubjectPublicKeyInfo |hashes| and returns true if:
    //   1) |bad_static_spki_hashes| does not intersect |hashes|; AND
    //   2) Both |static_spki_hashes| and |dynamic_spki_hashes| are empty
    //      or at least one of them intersects |hashes|.
    //
    // |{dynamic,static}_spki_hashes| contain trustworthy public key hashes,
    // any one of which is sufficient to validate the certificate chain in
    // question. The public keys could be of a root CA, intermediate CA, or
    // leaf certificate, depending on the security vs. disaster recovery
    // tradeoff selected. (Pinning only to leaf certifiates increases
    // security because you no longer trust any CAs, but it hampers disaster
    // recovery because you can't just get a new certificate signed by the
    // CA.)
    //
    // |bad_static_spki_hashes| contains public keys that we don't want to
    // trust.
    bool CheckPublicKeyPins(const HashValueVector& hashes) const;

    // Returns true if any of the HashValueVectors |static_spki_hashes|,
    // |bad_static_spki_hashes|, or |dynamic_spki_hashes| contains any
    // items.
    bool HasPublicKeyPins() const;
  };

  class NET_EXPORT PinSet {
   public:
    PinSet(std::string name,
           std::vector<std::vector<uint8_t>> static_spki_hashes,
           std::vector<std::vector<uint8_t>> bad_static_spki_hashes);
    PinSet(const PinSet& other);
    ~PinSet();

    const std::string& name() const { return name_; }
    const std::vector<std::vector<uint8_t>>& static_spki_hashes() const {
      return static_spki_hashes_;
    }
    const std::vector<std::vector<uint8_t>>& bad_static_spki_hashes() const {
      return bad_static_spki_hashes_;
    }

   private:
    std::string name_;
    std::vector<std::vector<uint8_t>> static_spki_hashes_;
    std::vector<std::vector<uint8_t>> bad_static_spki_hashes_;
  };

  struct NET_EXPORT PinSetInfo {
    std::string hostname_;
    std::string pinset_name_;
    bool include_subdomains_;

    PinSetInfo(std::string hostname,
               std::string pinset_name,
               bool include_subdomains);
  };

  // Indicates whether a connection met CT requirements.
  enum CTRequirementsStatus {
    // CT was not required for the connection.
    CT_NOT_REQUIRED,
    // CT was required for the connection and valid Certificate Transparency
    // information was provided.
    CT_REQUIREMENTS_MET,
    // CT was required for the connection but valid CT info was not provided.
    CT_REQUIREMENTS_NOT_MET,
  };

  TransportSecurityState();

  // Creates a TransportSecurityState object that will skip the check to force
  // HTTPS from static entries for the given set of hosts. All hostnames in the
  // bypass list must consist of a single label, i.e. they must be a TLD.
  explicit TransportSecurityState(
      std::vector<std::string> hsts_host_bypass_list);

  TransportSecurityState(const TransportSecurityState&) = delete;
  TransportSecurityState& operator=(const TransportSecurityState&) = delete;

  ~TransportSecurityState();

  // As ShouldUpgradeToSSL(), but also returns whether the decision came from
  // static or dynamic state, for metrics.
  SSLUpgradeDecision GetSSLUpgradeDecision(
      const std::string& host,
      const NetLogWithSource& net_log = NetLogWithSource());

  // These functions search for static and dynamic STS and PKP states, and
  // invoke the functions of the same name on them. These functions are the
  // primary public interface; direct access to STS and PKP states is best
  // left to tests. The caller needs to handle the optional pinning override
  // when is_issued_by_known_root is false.
  bool ShouldSSLErrorsBeFatal(const std::string& host);
  bool ShouldUpgradeToSSL(const std::string& host,
                          const NetLogWithSource& net_log = NetLogWithSource());
  PKPStatus CheckPublicKeyPins(const HostPortPair& host_port_pair,
                               bool is_issued_by_known_root,
                               const HashValueVector& hashes);
  bool HasPublicKeyPins(const std::string& host);

  // Returns CT_REQUIREMENTS_NOT_MET if a connection violates CT policy
  // requirements: that is, if a connection to |host|, using the validated
  // certificate |validated_certificate_chain|, is expected to be accompanied
  // with valid Certificate Transparency information that complies with the
  // connection's CTPolicyEnforcer and |policy_compliance| indicates that
  // the connection does not comply.
  //
  // The behavior may be further be altered by setting a RequireCTDelegate
  // via |SetRequireCTDelegate()|.
  CTRequirementsStatus CheckCTRequirements(
      const HostPortPair& host_port_pair,
      bool is_issued_by_known_root,
      const HashValueVector& public_key_hashes,
      const X509Certificate* validated_certificate_chain,
      ct::CTPolicyCompliance policy_compliance);

  // Assign a |Delegate| for persisting the transport security state. If
  // |NULL|, state will not be persisted. The caller retains
  // ownership of |delegate|.
  // Note: This is only used for serializing/deserializing the
  // TransportSecurityState.
  void SetDelegate(Delegate* delegate);

  // Assigns a delegate responsible for determining whether or not a
  // connection to a given host should require Certificate Transparency
  // information that complies with the CT policy provided by a
  // CTPolicyEnforcer.
  // If nullptr, no delegate will be consulted.
  // The caller retains ownership of the |delegate|, and must persist for
  // the lifetime of this object or until called with nullptr, whichever
  // occurs first.
  void SetRequireCTDelegate(RequireCTDelegate* delegate);

  // If |emergency_disable| is set to true, will stop requiring CT
  // compliance on any further requests regardless of host or certificate
  // status.
  void SetCTEmergencyDisabled(bool emergency_disable) {
    ct_emergency_disable_ = emergency_disable;
  }

  bool is_ct_emergency_disabled_for_testing() const {
    return ct_emergency_disable_;
  }

  // |pinsets| should include all known pinsets, |host_pins| the information
  // related to each hostname's pin, and |update_time| the time at which this
  // list was known to be up to date.
  void UpdatePinList(const std::vector<PinSet>& pinsets,
                     const std::vector<PinSetInfo>& host_pins,
                     base::Time update_time);

  // Clears all dynamic data (e.g. HSTS and HPKP data).
  //
  // Does NOT persist changes using the Delegate, as this function is only
  // used to clear any dynamic data prior to re-loading it from a file.
  // Note: This is only used for serializing/deserializing the
  // TransportSecurityState.
  void ClearDynamicData();

  // Inserts |state| into |enabled_sts_hosts_| under the key |hashed_host|.
  // |hashed_host| is already in the internal representation.
  // Note: This is only used for serializing/deserializing the
  // TransportSecurityState.
  void AddOrUpdateEnabledSTSHosts(const HashedHost& hashed_host,
                                  const STSState& state);

  // Deletes all dynamic data (e.g. HSTS or HPKP data) created between a time
  // period  [|start_time|, |end_time|).
  //
  // If any entries are deleted, the new state will be persisted through
  // the Delegate (if any). Calls |callback| when data is persisted to disk.
  void DeleteAllDynamicDataBetween(base::Time start_time,
                                   base::Time end_time,
                                   base::OnceClosure callback);

  // Deletes any dynamic data stored for |host| (e.g. HSTS or HPKP data).
  // If |host| doesn't have an exact entry then no action is taken. Does
  // not delete static (i.e. preloaded) data.  Returns true iff an entry
  // was deleted.
  //
  // If an entry is deleted, the new state will be persisted through
  // the Delegate (if any).
  bool DeleteDynamicDataForHost(const std::string& host);

  // Returns true and updates |*result| if |host| has dynamic or static
  // HSTS/HPKP (respectively) state. If multiple entries match |host|, dynamic
  // state is preferred over static state and other than that the most specific
  // match determines the return value (both is in deviation of RFC6797, cf.
  // https://crbug.com/821811).
  //
  // Note that these methods are not const because they opportunistically remove
  // entries that have expired.
  bool GetSTSState(const std::string& host, STSState* sts_result);
  bool GetPKPState(const std::string& host, PKPState* pkp_result);

  // Returns true and updates |*result| iff |host| has static HSTS/HPKP
  // (respectively) state. If multiple entries match |host|, the most specific
  // match determines the return value.
  bool GetStaticSTSState(const std::string& host, STSState* sts_result) const;
  bool GetStaticPKPState(const std::string& host, PKPState* pkp_result) const;

  // Returns true and updates |*result| iff |host| has dynamic
  // HSTS/HPKP (respectively) state. If multiple entries match |host|,
  // the most specific match determines the return value.
  //
  // Note that these methods are not const because they opportunistically remove
  // entries that have expired.
  bool GetDynamicSTSState(const std::string& host, STSState* result);
  bool GetDynamicPKPState(const std::string& host, PKPState* result);

  // Processes an HSTS header value from the host, adding entries to
  // dynamic state if necessary.
  bool AddHSTSHeader(std::string_view host, std::string_view value);

  // Adds explicitly-specified data as if it was processed from an
  // HSTS header (used for net-internals and unit tests).
  void AddHSTS(std::string_view host,
               const base::Time& expiry,
               bool include_subdomains);

  // Adds explicitly-specified data as if it was processed from an HPKP header.
  // Note: dynamic PKP data is not persisted.
  void AddHPKP(std::string_view host,
               const base::Time& expiry,
               bool include_subdomains,
               const HashValueVector& hashes);

  // Enables or disables public key pinning bypass for local trust anchors.
  // Disabling the bypass for local trust anchors is highly discouraged.
  // This method is used by Cronet only and *** MUST NOT *** be used by any
  // other consumer. For more information see "How does key pinning interact
  // with local proxies and filters?" at
  // https://www.chromium.org/Home/chromium-security/security-faq
  void SetEnablePublicKeyPinningBypassForLocalTrustAnchors(bool value);

  void AssertCalledOnValidThread() const {
    DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
  }

  // For unit tests only.
  void EnableStaticPinsForTesting() { enable_static_pins_ = true; }
  bool has_dynamic_pkp_state() const { return !enabled_pkp_hosts_.empty(); }

  // Sets whether pinning list timestamp freshness should be ignored for
  // testing.
  void SetPinningListAlwaysTimelyForTesting(bool always_timely) {
    pins_list_always_timely_for_testing_ = always_timely;
  }

  // The number of cached STSState entries.
  size_t num_sts_entries() const;

 private:
  friend class TransportSecurityStateTest;
  friend class TransportSecurityStateStaticFuzzer;
  FRIEND_TEST_ALL_PREFIXES(HttpSecurityHeadersTest, NoClobberPins);

  typedef std::map<HashedHost, STSState> STSStateMap;
  typedef std::map<HashedHost, PKPState> PKPStateMap;

  base::Value::Dict NetLogUpgradeToSSLParam(const std::string& host);

  // IsBuildTimely returns true if the current build is new enough ensure that
  // built in security information (i.e. HSTS preloading and pinning
  // information) is timely.
  static bool IsBuildTimely();

  // Helper method for actually checking pins.
  PKPStatus CheckPublicKeyPinsImpl(const HostPortPair& host_port_pair,
                                   bool is_issued_by_known_root,
                                   const HashValueVector& hashes);

  // If a Delegate is present, notify it that the internal state has
  // changed.
  void DirtyNotify();

  // Adds HSTS and HPKP state for |host|. The new state supercedes
  // any previous state for the |host|, including static entries.
  //
  // The new state for |host| is persisted using the Delegate (if any).
  void AddHSTSInternal(std::string_view host,
                       STSState::UpgradeMode upgrade_mode,
                       const base::Time& expiry,
                       bool include_subdomains);
  void AddHPKPInternal(std::string_view host,
                       const base::Time& last_observed,
                       const base::Time& expiry,
                       bool include_subdomains,
                       const HashValueVector& hashes);

  // Returns true if a request to |host_port_pair| with the given
  // SubjectPublicKeyInfo |hashes| satisfies the pins in |pkp_state|,
  // and false otherwise.
  PKPStatus CheckPins(const HostPortPair& host_port_pair,
                      bool is_issued_by_known_root,
                      const TransportSecurityState::PKPState& pkp_state,
                      const HashValueVector& hashes);

  // Returns true if the static key pinning list has been updated in the last 10
  // weeks.
  bool IsStaticPKPListTimely() const;

  // The sets of hosts that have enabled TransportSecurity. |domain| will always
  // be empty for a STSState or PKPState in these maps; the domain comes from
  // the map keys instead. In addition, |upgrade_mode| in the STSState is never
  // MODE_DEFAULT and |HasPublicKeyPins| in the PKPState always returns true.
  STSStateMap enabled_sts_hosts_;
  PKPStateMap enabled_pkp_hosts_;

  raw_ptr<Delegate> delegate_ = nullptr;

  // True if static pins should be used.
  bool enable_static_pins_ = true;

  // True if public key pinning bypass is enabled for local trust anchors.
  bool enable_pkp_bypass_for_local_trust_anchors_ = true;

  raw_ptr<RequireCTDelegate> require_ct_delegate_ = nullptr;

  std::set<std::string> hsts_host_bypass_list_;

  bool ct_emergency_disable_ = false;

  // The values in host_pins_ maps are references to PinSet objects in the
  // pinsets_ vector.
  std::optional<
      std::map<std::string, std::pair<const PinSet*, bool>, std::less<>>>
      host_pins_;
  base::Time key_pins_list_last_update_time_;
  std::vector<PinSet> pinsets_;

  bool pins_list_always_timely_for_testing_ = false;

  THREAD_CHECKER(thread_checker_);
};

}  // namespace net

#endif  // NET_HTTP_TRANSPORT_SECURITY_STATE_H_