Botan 3.9.0
Crypto and TLS for C&
Botan::TLS::Server_Hello_13 Class Reference

#include <tls_messages.h>

Inheritance diagram for Botan::TLS::Server_Hello_13:
Botan::TLS::Server_Hello Botan::TLS::Handshake_Message Botan::TLS::Hello_Retry_Request

Classes

struct  Hello_Retry_Request_Creation_Tag
struct  Hello_Retry_Request_Tag
struct  Server_Hello_Tag

Public Member Functions

uint16_t ciphersuite () const
const Extensionsextensions () const
std::optional< Protocol_Versionrandom_signals_downgrade () const
Protocol_Version selected_version () const final
std::vector< uint8_t > serialize () const override
const Session_IDsession_id () const
Handshake_Type type () const override
std::string type_string () const
virtual Handshake_Type wire_type () const

Static Public Member Functions

static std::variant< Hello_Retry_Request, Server_Hello_13create (const Client_Hello_13 &ch, bool hello_retry_request_allowed, Session_Manager &session_mgr, Credentials_Manager &credentials_mgr, RandomNumberGenerator &rng, const Policy &policy, Callbacks &cb)
static std::variant< Hello_Retry_Request, Server_Hello_13, Server_Hello_12parse (const std::vector< uint8_t > &buf)

Protected Member Functions

void basic_validation () const
uint8_t compression_method () const
std::set< Extension_Codeextension_types () const
Protocol_Version legacy_version () const
const std::vector< uint8_t > & random () const
 Server_Hello_13 (const Client_Hello_13 &ch, std::optional< Named_Group > key_exchange_group, Session_Manager &session_mgr, Credentials_Manager &credentials_mgr, RandomNumberGenerator &rng, Callbacks &cb, const Policy &policy)
 Server_Hello_13 (std::unique_ptr< Server_Hello_Internal > data, Hello_Retry_Request_Creation_Tag tag)
 Server_Hello_13 (std::unique_ptr< Server_Hello_Internal > data, Hello_Retry_Request_Tag tag)
 Server_Hello_13 (std::unique_ptr< Server_Hello_Internal > data, Server_Hello_Tag tag=as_server_hello)

Protected Attributes

std::unique_ptr< Server_Hello_Internal > m_data

Static Protected Attributes

static const struct Botan::TLS::Server_Hello_13::Hello_Retry_Request_Tag as_hello_retry_request
static const struct Botan::TLS::Server_Hello_13::Hello_Retry_Request_Creation_Tag as_new_hello_retry_request
static const struct Botan::TLS::Server_Hello_13::Server_Hello_Tag as_server_hello

Detailed Description

Definition at line 400 of file tls_messages.h.

Constructor & Destructor Documentation

◆ Server_Hello_13() [1/4]

Botan::TLS::Server_Hello_13::Server_Hello_13 ( std::unique_ptr< Server_Hello_Internal > data,
Server_Hello_13::Server_Hello_Tag tag = as_server_hello )
explicitprotected

Definition at line 588 of file msg_server_hello.cpp.

589 :
590 Server_Hello(std::move(data)) {
591 BOTAN_ASSERT_NOMSG(!m_data->is_hello_retry_request());
593
594 const auto& exts = extensions();
595
596 // RFC 8446 4.1.3
597 // The ServerHello MUST only include extensions which are required to
598 // establish the cryptographic context and negotiate the protocol version.
599 // [...]
600 // Other extensions (see Section 4.2) are sent separately in the
601 // EncryptedExtensions message.
602 //
603 // Note that further validation dependent on the client hello is done in the
604 // TLS client implementation.
605 const std::set<Extension_Code> allowed = {
609 };
610
611 // As the ServerHello shall only contain essential extensions, we don't give
612 // any slack for extensions not implemented by Botan here.
613 if(exts.contains_other_than(allowed)) {
614 throw TLS_Exception(Alert::UnsupportedExtension, "Server Hello contained an extension that is not allowed");
615 }
616
617 // RFC 8446 4.1.3
618 // Current ServerHello messages additionally contain
619 // either the "pre_shared_key" extension or the "key_share"
620 // extension, or both [...].
621 if(!exts.has<Key_Share>() && !exts.has<PSK_Key_Exchange_Modes>()) {
622 throw TLS_Exception(Alert::MissingExtension, "server hello must contain key exchange information");
623 }
624}
#define BOTAN_ASSERT_NOMSG(expr)
Definition assert.h:75
Server_Hello(const Server_Hello &)=delete
std::unique_ptr< Server_Hello_Internal > m_data
const Extensions & extensions() const

References basic_validation(), BOTAN_ASSERT_NOMSG, Botan::TLS::Server_Hello::extensions(), Botan::TLS::KeyShare, Botan::TLS::Server_Hello::m_data, Botan::TLS::PresharedKey, Botan::TLS::Server_Hello::Server_Hello(), and Botan::TLS::SupportedVersions.

Referenced by create(), and parse().

◆ Server_Hello_13() [2/4]

Botan::TLS::Server_Hello_13::Server_Hello_13 ( std::unique_ptr< Server_Hello_Internal > data,
Server_Hello_13::Hello_Retry_Request_Tag tag )
explicitprotected

Definition at line 626 of file msg_server_hello.cpp.

627 :
628 Server_Hello(std::move(data)) {
629 BOTAN_ASSERT_NOMSG(m_data->is_hello_retry_request());
631
632 const auto& exts = extensions();
633
634 // RFC 8446 4.1.4
635 // The HelloRetryRequest extensions defined in this specification are:
636 // - supported_versions (see Section 4.2.1)
637 // - cookie (see Section 4.2.2)
638 // - key_share (see Section 4.2.8)
639 const std::set<Extension_Code> allowed = {
643 };
644
645 // As the Hello Retry Request shall only contain essential extensions, we
646 // don't give any slack for extensions not implemented by Botan here.
647 if(exts.contains_other_than(allowed)) {
648 throw TLS_Exception(Alert::UnsupportedExtension,
649 "Hello Retry Request contained an extension that is not allowed");
650 }
651
652 // RFC 8446 4.1.4
653 // Clients MUST abort the handshake with an "illegal_parameter" alert if
654 // the HelloRetryRequest would not result in any change in the ClientHello.
655 if(!exts.has<Key_Share>() && !exts.has<Cookie>()) {
656 throw TLS_Exception(Alert::IllegalParameter, "Hello Retry Request does not request any changes to Client Hello");
657 }
658}

References basic_validation(), BOTAN_ASSERT_NOMSG, Botan::TLS::Cookie, Botan::TLS::Server_Hello::extensions(), Botan::TLS::KeyShare, Botan::TLS::Server_Hello::m_data, Botan::TLS::Server_Hello::Server_Hello(), and Botan::TLS::SupportedVersions.

◆ Server_Hello_13() [3/4]

Botan::TLS::Server_Hello_13::Server_Hello_13 ( const Client_Hello_13 & ch,
std::optional< Named_Group > key_exchange_group,
Session_Manager & session_mgr,
Credentials_Manager & credentials_mgr,
RandomNumberGenerator & rng,
Callbacks & cb,
const Policy & policy )
protected

Definition at line 710 of file msg_server_hello.cpp.

716 :
717 Server_Hello(std::make_unique<Server_Hello_Internal>(
718 Protocol_Version::TLS_V12,
719 ch.session_id(),
720 make_server_hello_random(rng, Protocol_Version::TLS_V13, cb, policy),
721 choose_ciphersuite(ch, policy),
722 uint8_t(0) /* compression method */
723 )) {
724 // RFC 8446 4.2.1
725 // A server which negotiates TLS 1.3 MUST respond by sending a
726 // "supported_versions" extension containing the selected version
727 // value (0x0304). It MUST set the ServerHello.legacy_version field to
728 // 0x0303 (TLS 1.2).
729 //
730 // Note that the legacy version (TLS 1.2) is set in this constructor's
731 // initializer list, accordingly.
732 m_data->extensions().add(new Supported_Versions(Protocol_Version::TLS_V13)); // NOLINT(*-owning-memory)
733
734 if(key_exchange_group.has_value()) {
735 BOTAN_ASSERT_NOMSG(ch.extensions().has<Key_Share>());
737 key_exchange_group.value(), *ch.extensions().get<Key_Share>(), policy, cb, rng));
738 }
739
740 const auto& ch_exts = ch.extensions();
741
742 if(ch_exts.has<PSK>()) {
743 const auto cs = Ciphersuite::by_id(m_data->ciphersuite());
745
746 // RFC 8446 4.2.9
747 // A client MUST provide a "psk_key_exchange_modes" extension if it
748 // offers a "pre_shared_key" extension.
749 //
750 // Note: Client_Hello_13 constructor already performed a graceful check.
751 auto* const psk_modes = ch_exts.get<PSK_Key_Exchange_Modes>();
752 BOTAN_ASSERT_NONNULL(psk_modes);
753
754 // TODO: also support PSK_Key_Exchange_Mode::PSK_KE
755 // (PSK-based handshake without an additional ephemeral key exchange)
756 if(value_exists(psk_modes->modes(), PSK_Key_Exchange_Mode::PSK_DHE_KE)) {
757 if(auto server_psk = ch_exts.get<PSK>()->select_offered_psk(
758 ch.sni_hostname(), cs.value(), session_mgr, credentials_mgr, cb, policy)) {
759 // RFC 8446 4.2.11
760 // In order to accept PSK key establishment, the server sends a
761 // "pre_shared_key" extension indicating the selected identity.
762 m_data->extensions().add(std::move(server_psk));
763 }
764 }
765 }
766
767 cb.tls_modify_extensions(m_data->extensions(), Connection_Side::Server, type());
768}
#define BOTAN_ASSERT_NONNULL(ptr)
Definition assert.h:114
static std::optional< Ciphersuite > by_id(uint16_t suite)
virtual Handshake_Type type() const =0
static std::unique_ptr< Key_Share > create_as_encapsulation(Group_Params selected_group, const Key_Share &client_keyshare, const Policy &policy, Callbacks &cb, RandomNumberGenerator &rng)
bool value_exists(const std::vector< T > &vec, const OT &val)
Definition stl_util.h:52

References Botan::TLS::Client_Hello::extensions(), Botan::TLS::Server_Hello::m_data, Botan::TLS::Server_Hello::Server_Hello(), Botan::TLS::Server_Hello::session_id(), Botan::TLS::TLS_V12, and Botan::TLS::TLS_V13.

◆ Server_Hello_13() [4/4]

Botan::TLS::Server_Hello_13::Server_Hello_13 ( std::unique_ptr< Server_Hello_Internal > data,
Hello_Retry_Request_Creation_Tag tag )
explicitprotected

Definition at line 660 of file msg_server_hello.cpp.

661 :
662 Server_Hello(std::move(data)) {}

References Botan::TLS::Server_Hello::Server_Hello().

Member Function Documentation

◆ basic_validation()

void Botan::TLS::Server_Hello_13::basic_validation ( ) const
protected

Validation that applies to both Server Hello and Hello Retry Request

Definition at line 543 of file msg_server_hello.cpp.

543 {
544 BOTAN_ASSERT_NOMSG(m_data->version() == Protocol_Version::TLS_V13);
545
546 // Note: checks that cannot be performed without contextual information
547 // are done in the specific TLS client implementation.
548 // Note: The Supported_Version extension makes sure internally that
549 // exactly one entry is provided.
550
551 // Note: Hello Retry Request basic validation is equivalent with the
552 // basic validations required for Server Hello
553 //
554 // RFC 8446 4.1.4
555 // Upon receipt of a HelloRetryRequest, the client MUST check the
556 // legacy_version, [...], and legacy_compression_method as specified in
557 // Section 4.1.3 and then process the extensions, starting with determining
558 // the version using "supported_versions".
559
560 // RFC 8446 4.1.3
561 // In TLS 1.3, [...] the legacy_version field MUST be set to 0x0303
562 if(legacy_version() != Protocol_Version::TLS_V12) {
563 throw TLS_Exception(Alert::ProtocolVersion,
564 "legacy_version '" + legacy_version().to_string() + "' is not allowed");
565 }
566
567 // RFC 8446 4.1.3
568 // legacy_compression_method: A single byte which MUST have the value 0.
569 if(compression_method() != 0x00) {
570 throw TLS_Exception(Alert::DecodeError, "compression is not supported in TLS 1.3");
571 }
572
573 // RFC 8446 4.1.3
574 // All TLS 1.3 ServerHello messages MUST contain the "supported_versions" extension.
575 if(!extensions().has<Supported_Versions>()) {
576 throw TLS_Exception(Alert::MissingExtension, "server hello did not contain 'supported version' extension");
577 }
578
579 // RFC 8446 4.2.1
580 // A server which negotiates TLS 1.3 MUST respond by sending
581 // a "supported_versions" extension containing the selected version
582 // value (0x0304).
583 if(selected_version() != Protocol_Version::TLS_V13) {
584 throw TLS_Exception(Alert::IllegalParameter, "TLS 1.3 Server Hello selected a different version");
585 }
586}
Protocol_Version selected_version() const final
Protocol_Version legacy_version() const
std::string to_string(ErrorType type)
Convert an ErrorType to string.
Definition exceptn.cpp:13

References BOTAN_ASSERT_NOMSG, Botan::TLS::Server_Hello::compression_method(), Botan::TLS::Server_Hello::extensions(), Botan::TLS::Server_Hello::legacy_version(), Botan::TLS::Server_Hello::m_data, selected_version(), and Botan::to_string().

Referenced by Server_Hello_13(), and Server_Hello_13().

◆ ciphersuite()

uint16_t Botan::TLS::Server_Hello::ciphersuite ( ) const
inherited

Definition at line 217 of file msg_server_hello.cpp.

217 {
218 return m_data->ciphersuite();
219}

References m_data.

Referenced by Botan::TLS::Client_Hello_13::retry(), Botan::TLS::Server_Hello_12::Server_Hello_12(), and ~Server_Hello().

◆ compression_method()

uint8_t Botan::TLS::Server_Hello::compression_method ( ) const
protectedinherited

Definition at line 209 of file msg_server_hello.cpp.

209 {
210 return m_data->comp_method();
211}

References m_data.

Referenced by Botan::TLS::Server_Hello_13::basic_validation(), selected_version(), and Botan::TLS::Server_Hello_12::Server_Hello_13.

◆ create()

std::variant< Hello_Retry_Request, Server_Hello_13 > Botan::TLS::Server_Hello_13::create ( const Client_Hello_13 & ch,
bool hello_retry_request_allowed,
Session_Manager & session_mgr,
Credentials_Manager & credentials_mgr,
RandomNumberGenerator & rng,
const Policy & policy,
Callbacks & cb )
static

Definition at line 462 of file msg_server_hello.cpp.

468 {
469 const auto& exts = ch.extensions();
470
471 // RFC 8446 4.2.9
472 // [With PSK with (EC)DHE key establishment], the client and server MUST
473 // supply "key_share" values [...].
474 //
475 // Note: We currently do not support PSK without (EC)DHE, hence, we can
476 // assume that those extensions are available.
477 BOTAN_ASSERT_NOMSG(exts.has<Supported_Groups>() && exts.has<Key_Share>());
478 const auto& supported_by_client = exts.get<Supported_Groups>()->groups();
479 const auto& offered_by_client = exts.get<Key_Share>()->offered_groups();
480 const auto selected_group = policy.choose_key_exchange_group(supported_by_client, offered_by_client);
481
482 // RFC 8446 4.1.1
483 // If there is no overlap between the received "supported_groups" and the
484 // groups supported by the server, then the server MUST abort the
485 // handshake with a "handshake_failure" or an "insufficient_security" alert.
486 if(selected_group == Named_Group::NONE) {
487 throw TLS_Exception(Alert::HandshakeFailure, "Client did not offer any acceptable group");
488 }
489
490 // RFC 8446 4.2.8:
491 // Servers MUST NOT send a KeyShareEntry for any group not indicated in the
492 // client's "supported_groups" extension [...]
493 if(!value_exists(supported_by_client, selected_group)) {
494 throw TLS_Exception(Alert::InternalError, "Application selected a group that is not supported by the client");
495 }
496
497 // RFC 8446 4.1.4
498 // The server will send this message in response to a ClientHello
499 // message if it is able to find an acceptable set of parameters but the
500 // ClientHello does not contain sufficient information to proceed with
501 // the handshake.
502 //
503 // In this case, the Client Hello did not contain a key share offer for
504 // the group selected by the application.
505 if(!value_exists(offered_by_client, selected_group)) {
506 // RFC 8446 4.1.4
507 // If a client receives a second HelloRetryRequest in the same
508 // connection (i.e., where the ClientHello was itself in response to a
509 // HelloRetryRequest), it MUST abort the handshake with an
510 // "unexpected_message" alert.
511 BOTAN_STATE_CHECK(hello_retry_request_allowed);
512 return Hello_Retry_Request(ch, selected_group, policy, cb);
513 } else {
514 return Server_Hello_13(ch, selected_group, session_mgr, credentials_mgr, rng, cb, policy);
515 }
516}
#define BOTAN_STATE_CHECK(expr)
Definition assert.h:49
Server_Hello_13(std::unique_ptr< Server_Hello_Internal > data, Server_Hello_Tag tag=as_server_hello)

References BOTAN_ASSERT_NOMSG, BOTAN_STATE_CHECK, Botan::TLS::Policy::choose_key_exchange_group(), Botan::TLS::Client_Hello::extensions(), Server_Hello_13(), and Botan::value_exists().

◆ extension_types()

std::set< Extension_Code > Botan::TLS::Server_Hello::extension_types ( ) const
protectedinherited

Definition at line 221 of file msg_server_hello.cpp.

221 {
222 return m_data->extensions().extension_types();
223}

References m_data.

Referenced by selected_version(), and Botan::TLS::Server_Hello_12::Server_Hello_13.

◆ extensions()

const Extensions & Botan::TLS::Server_Hello::extensions ( ) const
inherited

◆ legacy_version()

Protocol_Version Botan::TLS::Server_Hello::legacy_version ( ) const
protectedinherited

Definition at line 201 of file msg_server_hello.cpp.

201 {
202 return m_data->legacy_version();
203}

References m_data.

Referenced by Botan::TLS::Server_Hello_13::basic_validation(), selected_version(), and Botan::TLS::Server_Hello_12::Server_Hello_13.

◆ parse()

std::variant< Hello_Retry_Request, Server_Hello_13, Server_Hello_12 > Botan::TLS::Server_Hello_13::parse ( const std::vector< uint8_t > & buf)
static

Definition at line 518 of file msg_server_hello.cpp.

519 {
520 auto data = std::make_unique<Server_Hello_Internal>(buf);
521 const auto version = data->version();
522
523 // server hello that appears to be pre-TLS 1.3, takes precedence over...
524 if(version.is_pre_tls_13()) {
525 return Server_Hello_12(std::move(data));
526 }
527
528 // ... the TLS 1.3 "special case" aka. Hello_Retry_Request
529 if(version == Protocol_Version::TLS_V13) {
530 if(data->is_hello_retry_request()) {
531 return Hello_Retry_Request(std::move(data));
532 }
533
534 return Server_Hello_13(std::move(data));
535 }
536
537 throw TLS_Exception(Alert::ProtocolVersion, "unexpected server hello version: " + version.to_string());
538}

References Server_Hello_13().

◆ random()

const std::vector< uint8_t > & Botan::TLS::Server_Hello::random ( ) const
protectedinherited

Definition at line 205 of file msg_server_hello.cpp.

205 {
206 return m_data->random();
207}

References m_data.

Referenced by selected_version(), and Botan::TLS::Server_Hello_12::Server_Hello_13.

◆ random_signals_downgrade()

std::optional< Protocol_Version > Botan::TLS::Server_Hello_13::random_signals_downgrade ( ) const

Return desired downgrade version indicated by hello random, if any.

Definition at line 770 of file msg_server_hello.cpp.

770 {
771 const uint64_t last8 = load_be<uint64_t>(m_data->random().data(), 3);
772 if(last8 == DOWNGRADE_TLS11) {
773 return Protocol_Version::TLS_V11;
774 }
775 if(last8 == DOWNGRADE_TLS12) {
776 return Protocol_Version::TLS_V12;
777 }
778
779 return std::nullopt;
780}
constexpr auto load_be(ParamTs &&... params)
Definition loadstor.h:504

References Botan::load_be(), and Botan::TLS::Server_Hello::m_data.

◆ selected_version()

Protocol_Version Botan::TLS::Server_Hello_13::selected_version ( ) const
finalvirtual
Returns
the selected version as indicated by the supported_versions extension

Implements Botan::TLS::Server_Hello.

Definition at line 782 of file msg_server_hello.cpp.

782 {
783 auto* const versions_ext = m_data->extensions().get<Supported_Versions>();
784 BOTAN_ASSERT_NOMSG(versions_ext);
785 const auto& versions = versions_ext->versions();
786 BOTAN_ASSERT_NOMSG(versions.size() == 1);
787 return versions.front();
788}

References BOTAN_ASSERT_NOMSG, and Botan::TLS::Server_Hello::m_data.

Referenced by basic_validation().

◆ serialize()

std::vector< uint8_t > Botan::TLS::Server_Hello::serialize ( ) const
overridevirtualinherited
Returns
DER representation of this message

Implements Botan::TLS::Handshake_Message.

Definition at line 177 of file msg_server_hello.cpp.

177 {
178 std::vector<uint8_t> buf;
179 buf.reserve(1024); // working around GCC warning
180
181 buf.push_back(m_data->legacy_version().major_version());
182 buf.push_back(m_data->legacy_version().minor_version());
183 buf += m_data->random();
184
185 append_tls_length_value(buf, m_data->session_id().get(), 1);
186
187 buf.push_back(get_byte<0>(m_data->ciphersuite()));
188 buf.push_back(get_byte<1>(m_data->ciphersuite()));
189
190 buf.push_back(m_data->comp_method());
191
192 buf += m_data->extensions().serialize(Connection_Side::Server);
193
194 return buf;
195}
void append_tls_length_value(std::vector< uint8_t, Alloc > &buf, const T *vals, size_t vals_size, size_t tag_size)
Definition tls_reader.h:184
constexpr uint8_t get_byte(T input)
Definition loadstor.h:79

References Botan::TLS::append_tls_length_value(), Botan::get_byte(), m_data, serialize(), Botan::TLS::Server, and Server_Hello().

Referenced by serialize(), and ~Server_Hello().

◆ session_id()

const Session_ID & Botan::TLS::Server_Hello::session_id ( ) const
inherited

◆ type()

Handshake_Type Botan::TLS::Server_Hello::type ( ) const
overridevirtualinherited
Returns
the message type

Implements Botan::TLS::Handshake_Message.

Definition at line 197 of file msg_server_hello.cpp.

References Botan::TLS::ServerHello.

Referenced by Botan::TLS::Server_Hello_12::random(), and ~Server_Hello().

◆ type_string()

std::string Botan::TLS::Handshake_Message::type_string ( ) const
inherited
Returns
string representation of this message type

Definition at line 19 of file tls_handshake_state.cpp.

19 {
21}
const char * handshake_type_to_string(Handshake_Type type)

References Botan::TLS::handshake_type_to_string(), and type().

◆ wire_type()

virtual Handshake_Type Botan::TLS::Handshake_Message::wire_type ( ) const
inlinevirtualinherited
Returns
the wire representation of the message's type

Reimplemented in Botan::TLS::Hello_Retry_Request.

Definition at line 39 of file tls_handshake_msg.h.

39 {
40 // Usually equal to the Handshake_Type enum value,
41 // with the exception of TLS 1.3 Hello Retry Request.
42 return type();
43 }

References type().

Referenced by Botan::TLS::Stream_Handshake_IO::send().

Member Data Documentation

◆ as_hello_retry_request

const Server_Hello_13::Hello_Retry_Request_Tag Botan::TLS::Server_Hello_13::as_hello_retry_request
staticprotected

◆ as_new_hello_retry_request

const Server_Hello_13::Hello_Retry_Request_Creation_Tag Botan::TLS::Server_Hello_13::as_new_hello_retry_request
staticprotected

◆ as_server_hello

const Server_Hello_13::Server_Hello_Tag Botan::TLS::Server_Hello_13::as_server_hello
staticprotected

Definition at line 458 of file msg_server_hello.cpp.

◆ m_data


The documentation for this class was generated from the following files: