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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Some helpers for quic crypto
#include <cstddef>
#include <cstdint>
#include <string>
#include "third_party/boringssl/src/include/openssl/evp.h"
#include "net/third_party/quiche/src/quic/core/crypto/crypto_handshake.h"
#include "net/third_party/quiche/src/quic/core/crypto/crypto_handshake_message.h"
#include "net/third_party/quiche/src/quic/core/crypto/crypto_protocol.h"
#include "net/third_party/quiche/src/quic/core/crypto/quic_crypter.h"
#include "net/third_party/quiche/src/quic/core/quic_packets.h"
#include "net/third_party/quiche/src/quic/core/quic_time.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_export.h"
#include "net/third_party/quiche/src/quic/platform/api/quic_string_piece.h"
namespace quic {
class QuicRandom;
class QUIC_EXPORT_PRIVATE CryptoUtils {
CryptoUtils() = delete;
// Diversification is a utility class that's used to act like a union type.
// Values can be created by calling the functions like |NoDiversification|,
// below.
class Diversification {
enum Mode {
NEVER, // Key diversification will never be used. Forward secure
// crypters will always use this mode.
PENDING, // Key diversification will happen when a nonce is later
// received. This should only be used by clients initial
// decrypters which are waiting on the divesification nonce
// from the server.
NOW, // Key diversification will happen immediate based on the nonce.
// This should only be used by servers initial encrypters.
Diversification(const Diversification& diversification) = default;
static Diversification Never() { return Diversification(NEVER, nullptr); }
static Diversification Pending() {
return Diversification(PENDING, nullptr);
static Diversification Now(DiversificationNonce* nonce) {
return Diversification(NOW, nonce);
Mode mode() const { return mode_; }
DiversificationNonce* nonce() const {
DCHECK_EQ(mode_, NOW);
return nonce_;
Diversification(Mode mode, DiversificationNonce* nonce)
: mode_(mode), nonce_(nonce) {}
Mode mode_;
DiversificationNonce* nonce_;
// SetKeyAndIV derives the key and IV from the given packet protection secret
// |pp_secret| and sets those fields on the given QuicCrypter |*crypter|.
// This follows the derivation described in section 7.3 of RFC 8446, except
// with the label prefix in HKDF-Expand-Label changed from "tls13 " to "quic "
// as described in draft-ietf-quic-tls-14, section 5.1.
static void SetKeyAndIV(const EVP_MD* prf,
const std::vector<uint8_t>& pp_secret,
QuicCrypter* crypter);
// QUIC encrypts TLS handshake messages with a version-specific key (to
// prevent network observers that are not aware of that QUIC version from
// making decisions based on the TLS handshake). This packet protection secret
// is derived from the connection ID in the client's Initial packet.
// This function takes that |connection_id| and creates the encrypter and
// decrypter (put in |*crypters|) to use for this packet protection, as well
// as setting the key and IV on those crypters.
static void CreateTlsInitialCrypters(Perspective perspective,
QuicTransportVersion version,
QuicConnectionId connection_id,
CrypterPair* crypters);
// Generates the connection nonce. The nonce is formed as:
// <4 bytes> current time
// <8 bytes> |orbit| (or random if |orbit| is empty)
// <20 bytes> random
static void GenerateNonce(QuicWallTime now,
QuicRandom* random_generator,
QuicStringPiece orbit,
std::string* nonce);
// DeriveKeys populates |crypters->encrypter|, |crypters->decrypter|, and
// |subkey_secret| (optional -- may be null) given the contents of
// |premaster_secret|, |client_nonce|, |server_nonce| and |hkdf_input|. |aead|
// determines which cipher will be used. |perspective| controls whether the
// server's keys are assigned to |encrypter| or |decrypter|. |server_nonce| is
// optional and, if non-empty, is mixed into the key derivation.
// |subkey_secret| will have the same length as |premaster_secret|.
// If |pre_shared_key| is non-empty, it is incorporated into the key
// derivation parameters. If it is empty, the key derivation is unaltered.
// If the mode of |diversification| is NEVER, the the crypters will be
// configured to never perform key diversification. If the mode is
// NOW (which is only for servers, then the encrypter will be keyed via a
// two-step process that uses the nonce from |diversification|.
// If the mode is PENDING (which is only for servres), then the
// decrypter will only be keyed to a preliminary state: a call to
// |SetDiversificationNonce| with a diversification nonce will be needed to
// complete keying.
static bool DeriveKeys(QuicStringPiece premaster_secret,
QuicTag aead,
QuicStringPiece client_nonce,
QuicStringPiece server_nonce,
QuicStringPiece pre_shared_key,
const std::string& hkdf_input,
Perspective perspective,
Diversification diversification,
CrypterPair* crypters,
std::string* subkey_secret);
// Performs key extraction to derive a new secret of |result_len| bytes
// dependent on |subkey_secret|, |label|, and |context|. Returns false if the
// parameters are invalid (e.g. |label| contains null bytes); returns true on
// success.
static bool ExportKeyingMaterial(QuicStringPiece subkey_secret,
QuicStringPiece label,
QuicStringPiece context,
size_t result_len,
std::string* result);
// Computes the FNV-1a hash of the provided DER-encoded cert for use in the
// XLCT tag.
static uint64_t ComputeLeafCertHash(QuicStringPiece cert);
// Validates that |server_hello| is actually an SHLO message and that it is
// not part of a downgrade attack.
// Returns QUIC_NO_ERROR if this is the case or returns the appropriate error
// code and sets |error_details|.
static QuicErrorCode ValidateServerHello(
const CryptoHandshakeMessage& server_hello,
const ParsedQuicVersionVector& negotiated_versions,
std::string* error_details);
// Validates that the |server_versions| received do not indicate that the
// ServerHello is part of a downgrade attack. |negotiated_versions| must
// contain the list of versions received in the server's version negotiation
// packet (or be empty if no such packet was received).
// Returns QUIC_NO_ERROR if this is the case or returns the appropriate error
// code and sets |error_details|.
static QuicErrorCode ValidateServerHelloVersions(
const QuicVersionLabelVector& server_versions,
const ParsedQuicVersionVector& negotiated_versions,
std::string* error_details);
// Validates that |client_hello| is actually a CHLO and that this is not part
// of a downgrade attack.
// This includes verifiying versions and detecting downgrade attacks.
// Returns QUIC_NO_ERROR if this is the case or returns the appropriate error
// code and sets |error_details|.
static QuicErrorCode ValidateClientHello(
const CryptoHandshakeMessage& client_hello,
ParsedQuicVersion version,
const ParsedQuicVersionVector& supported_versions,
std::string* error_details);
// Validates that the |client_version| received does not indicate that a
// downgrade attack has occurred. |connection_version| is the version of the
// QuicConnection, and |supported_versions| is all versions that that
// QuicConnection supports.
// Returns QUIC_NO_ERROR if this is the case or returns the appropriate error
// code and sets |error_details|.
static QuicErrorCode ValidateClientHelloVersion(
QuicVersionLabel client_version,
ParsedQuicVersion connection_version,
const ParsedQuicVersionVector& supported_versions,
std::string* error_details);
// Returns the name of the HandshakeFailureReason as a char*
static const char* HandshakeFailureReasonToString(
HandshakeFailureReason reason);
// Returns a hash of the serialized |message|.
static std::string HashHandshakeMessage(const CryptoHandshakeMessage& message,
Perspective perspective);
// Implements the HKDF-Expand-Label function as defined in section 7.1 of RFC
// 8446, except that it uses "quic " as the prefix instead of "tls13 ", as
// specified by draft-ietf-quic-tls-14. The HKDF-Expand-Label function takes 4
// explicit arguments (Secret, Label, Context, and Length), as well as
// implicit PRF which is the hash function negotiated by TLS. Its use in QUIC
// (as needed by the QUIC stack, instead of as used internally by the TLS
// stack) is only for deriving initial secrets for obfuscation and for
// calculating packet protection keys and IVs from the corresponding packet
// protection secret. Neither of these uses need a Context (a zero-length
// context is provided), so this argument is omitted here.
// The implicit PRF is explicitly passed into HkdfExpandLabel as |prf|; the
// Secret, Label, and Length are passed in as |secret|, |label|, and
// |out_len|, respectively. The resulting expanded secret is returned.
static std::vector<uint8_t> HkdfExpandLabel(
const EVP_MD* prf,
const std::vector<uint8_t>& secret,
const std::string& label,
size_t out_len);
} // namespace quic