24648292556

Committed 19 Apr 2026 10:53PM UTC coverage: 89.474% (+0.03%) from 89.442%

Build # 24648292556

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github

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web-flow

Commit Message

Merge pull request #5536 from randombit/jack/x509-misc

Various PKIX optimizations and bug fixes

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106453 of 118977 relevant lines covered (89.47%)

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94.74

/src/lib/tls/tls13/msg_encrypted_extensions.cpp

/*
* TLS Hello Request and Client Hello Messages
* (C) 2022 Jack Lloyd
*     2022 René Meusel, Hannes Rantzsch - neXenio GmbH
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/tls_messages_13.h>

#include <botan/tls_callbacks.h>
#include <botan/tls_exceptn.h>
#include <botan/tls_policy.h>
#include <botan/internal/tls_reader.h>

namespace Botan::TLS {

Encrypted_Extensions::Encrypted_Extensions(const Client_Hello_13& client_hello,
                                           const Policy& policy,
                                           Callbacks& cb,
                                           bool is_resumption) {
   const auto& exts = client_hello.extensions();

   // NOLINTBEGIN(*-owning-memory)

   // RFC 8446 4.2.7
   //    As of TLS 1.3, servers are permitted to send the "supported_groups"
   //    extension to the client.  Clients [...] MAY use the information
   //    learned from a successfully completed handshake to change what groups
   //    they use in their "key_share" extension in subsequent connections.
   if(exts.has<Supported_Groups>()) {
      m_extensions.add(new Supported_Groups(policy.key_exchange_groups()));
   }

   const auto record_size_limit = policy.record_size_limit();
   const auto max_record_size = MAX_PLAINTEXT_SIZE + 1 /* encrypted content type byte */;
   if(exts.has<Record_Size_Limit>()) {
      // RFC 8449 4
      //    Endpoints SHOULD advertise the "record_size_limit" extension, even
      //    if they have no need to limit the size of records. [...]  For
      //    servers, this allows clients to know that their limit will be
      //    respected.
      m_extensions.add(new Record_Size_Limit(record_size_limit.value_or(max_record_size)));
   } else if(record_size_limit.has_value() && record_size_limit.value() < max_record_size) {
      // RFC 8449 4
      //    Endpoints SHOULD advertise the "record_size_limit" extension, even if
      //    they have no need to limit the size of records. For clients, this
      //    allows servers to advertise a limit at their discretion.
      throw TLS_Exception(Alert::MissingExtension,
                          "Server cannot enforce record size limit without the client supporting it");
   }

   // RFC 7250 4.2
   //    If the TLS server wants to request a certificate from the client
   //    (via the certificate_request message), it MUST include the
   //    client_certificate_type extension in the server hello.
   //    [...]
   //    If the server does not send a certificate_request payload [...],
   //    then the client_certificate_type payload in the server hello MUST be
   //    omitted.
   if(auto* ch_client_cert_types = exts.get<Client_Certificate_Type>();
      ch_client_cert_types != nullptr && policy.request_client_certificate_authentication()) {
      m_extensions.add(new Client_Certificate_Type(*ch_client_cert_types, policy));
   }

   // RFC 7250 4.2
   //    The server_certificate_type extension in the client hello indicates the
   //    types of certificates the client is able to process when provided by
   //    the server in a subsequent certificate payload. [...] With the
   //    server_certificate_type extension in the server hello, the TLS server
   //    indicates the certificate type carried in the Certificate payload.
   if(auto* ch_server_cert_types = exts.get<Server_Certificate_Type>()) {
      m_extensions.add(new Server_Certificate_Type(*ch_server_cert_types, policy));
   }

   // RFC 6066 3
   //    A server that receives a client hello containing the "server_name"
   //    extension [...] SHALL include an extension of type "server_name" in the
   //    (extended) server hello. The "extension_data" field of this extension
   //    SHALL be empty.
   //
   //    When resuming a session, the server MUST NOT include a server_name
   //    extension in the server hello.
   if(exts.has<Server_Name_Indicator>() && !is_resumption) {
      m_extensions.add(new Server_Name_Indicator(""));
   }

   if(auto* alpn_ext = exts.get<Application_Layer_Protocol_Notification>()) {
      const auto next_protocol = cb.tls_server_choose_app_protocol(alpn_ext->protocols());
      if(!next_protocol.empty()) {
         m_extensions.add(new Application_Layer_Protocol_Notification(next_protocol));
      }
   }

   // NOLINTEND(*-owning-memory)

   // TODO: Implement handling for (at least)
   //       * SRTP

   cb.tls_modify_extensions(m_extensions, Connection_Side::Server, type());
}

Encrypted_Extensions::Encrypted_Extensions(const std::vector<uint8_t>& buf) {
   TLS_Data_Reader reader("encrypted extensions reader", buf);

   // Encrypted Extensions contains a list of extensions. This list may legally
   // be empty. However, in that case we should at least see a two-byte length
   // field that reads 0x00 0x00.
   if(buf.size() < 2) {
      throw TLS_Exception(Alert::DecodeError, "Server sent an empty Encrypted Extensions message");
   }

   m_extensions.deserialize(reader, Connection_Side::Server, type());

   // RFC 8446 4.2
   //    If an implementation receives an extension which it recognizes and
   //    which is not specified for the message in which it appears, it MUST
   //    abort the handshake with an "illegal_parameter" alert.
   //
   // Note that we cannot encounter any extensions that we don't recognize here,
   // since only extensions we previously offered are allowed in EE.
   const auto allowed_exts = std::set<Extension_Code>{
      // Allowed extensions listed in RFC 8446 and implemented in Botan
      Extension_Code::ServerNameIndication,
      // MAX_FRAGMENT_LENGTH
      Extension_Code::SupportedGroups,
      Extension_Code::UseSrtp,
      // HEARTBEAT
      Extension_Code::ApplicationLayerProtocolNegotiation,
      // RFC 7250
      Extension_Code::ClientCertificateType,
      Extension_Code::ServerCertificateType,
      // EARLY_DATA

      // Allowed extensions not listed in RFC 8446 but acceptable as Botan implements them
      Extension_Code::RecordSizeLimit,
   };
   if(m_extensions.contains_implemented_extensions_other_than(allowed_exts)) {
      throw TLS_Exception(Alert::IllegalParameter, "Encrypted Extensions contained an extension that is not allowed");
   }
}

std::vector<uint8_t> Encrypted_Extensions::serialize() const {
   return m_extensions.serialize(Connection_Side::Server);
}

}  // namespace Botan::TLS

1	/*
2	* TLS Hello Request and Client Hello Messages
3	* (C) 2022 Jack Lloyd
4	* 2022 René Meusel, Hannes Rantzsch - neXenio GmbH
5	*
6	* Botan is released under the Simplified BSD License (see license.txt)
7	*/
8
9	#include <botan/tls_messages_13.h>
10
11	#include <botan/tls_callbacks.h>
12	#include <botan/tls_exceptn.h>
13	#include <botan/tls_policy.h>
14	#include <botan/internal/tls_reader.h>
15
16	namespace Botan::TLS {
17
18	Encrypted_Extensions::Encrypted_Extensions(const Client_Hello_13& client_hello,	390✔
19	const Policy& policy,
20	Callbacks& cb,
21	bool is_resumption) {	390✔
22	const auto& exts = client_hello.extensions();	390✔
23
24	// NOLINTBEGIN(*-owning-memory)
25
26	// RFC 8446 4.2.7
27	// As of TLS 1.3, servers are permitted to send the "supported_groups"
28	// extension to the client. Clients [...] MAY use the information
29	// learned from a successfully completed handshake to change what groups
30	// they use in their "key_share" extension in subsequent connections.
31	if(exts.has<Supported_Groups>()) {	390✔
32	m_extensions.add(new Supported_Groups(policy.key_exchange_groups()));	780✔
33	}
34
35	const auto record_size_limit = policy.record_size_limit();	390✔
36	const auto max_record_size = MAX_PLAINTEXT_SIZE + 1 /* encrypted content type byte */;	390✔
37	if(exts.has<Record_Size_Limit>()) {	390✔
38	// RFC 8449 4
39	// Endpoints SHOULD advertise the "record_size_limit" extension, even
40	// if they have no need to limit the size of records. [...] For
41	// servers, this allows clients to know that their limit will be
42	// respected.
43	m_extensions.add(new Record_Size_Limit(record_size_limit.value_or(max_record_size)));	15✔
44	} else if(record_size_limit.has_value() && record_size_limit.value() < max_record_size) {	382✔
45	// RFC 8449 4
46	// Endpoints SHOULD advertise the "record_size_limit" extension, even if
47	// they have no need to limit the size of records. For clients, this
48	// allows servers to advertise a limit at their discretion.
49	throw TLS_Exception(Alert::MissingExtension,	×
50	"Server cannot enforce record size limit without the client supporting it");	×
51	}
52
53	// RFC 7250 4.2
54	// If the TLS server wants to request a certificate from the client
55	// (via the certificate_request message), it MUST include the
56	// client_certificate_type extension in the server hello.
57	// [...]
58	// If the server does not send a certificate_request payload [...],
59	// then the client_certificate_type payload in the server hello MUST be
60	// omitted.
61	if(auto* ch_client_cert_types = exts.get<Client_Certificate_Type>();	390✔
62	ch_client_cert_types != nullptr && policy.request_client_certificate_authentication()) {	390✔
63	m_extensions.add(new Client_Certificate_Type(*ch_client_cert_types, policy));	9✔
64	}
65
66	// RFC 7250 4.2
67	// The server_certificate_type extension in the client hello indicates the
68	// types of certificates the client is able to process when provided by
69	// the server in a subsequent certificate payload. [...] With the
70	// server_certificate_type extension in the server hello, the TLS server
71	// indicates the certificate type carried in the Certificate payload.
72	if(auto* ch_server_cert_types = exts.get<Server_Certificate_Type>()) {	390✔
73	m_extensions.add(new Server_Certificate_Type(*ch_server_cert_types, policy));	1✔
74	}
75
76	// RFC 6066 3
77	// A server that receives a client hello containing the "server_name"
78	// extension [...] SHALL include an extension of type "server_name" in the
79	// (extended) server hello. The "extension_data" field of this extension
80	// SHALL be empty.
81	//
82	// When resuming a session, the server MUST NOT include a server_name
83	// extension in the server hello.
84	if(exts.has<Server_Name_Indicator>() && !is_resumption) {	390✔
85	m_extensions.add(new Server_Name_Indicator(""));	289✔
86	}
87
88	if(auto* alpn_ext = exts.get<Application_Layer_Protocol_Notification>()) {	390✔
89	const auto next_protocol = cb.tls_server_choose_app_protocol(alpn_ext->protocols());	7✔
90	if(!next_protocol.empty()) {	6✔
91	m_extensions.add(new Application_Layer_Protocol_Notification(next_protocol));	4✔
92	}
93	}	6✔
94
95	// NOLINTEND(*-owning-memory)
96
97	// TODO: Implement handling for (at least)
98	// * SRTP
99
100	cb.tls_modify_extensions(m_extensions, Connection_Side::Server, type());	389✔
101	}	390✔
102
103	Encrypted_Extensions::Encrypted_Extensions(const std::vector<uint8_t>& buf) {	486✔
104	TLS_Data_Reader reader("encrypted extensions reader", buf);	486✔
105
106	// Encrypted Extensions contains a list of extensions. This list may legally
107	// be empty. However, in that case we should at least see a two-byte length
108	// field that reads 0x00 0x00.
109	if(buf.size() < 2) {	486✔
110	throw TLS_Exception(Alert::DecodeError, "Server sent an empty Encrypted Extensions message");	1✔
111	}
112
113	m_extensions.deserialize(reader, Connection_Side::Server, type());	485✔
114
115	// RFC 8446 4.2
116	// If an implementation receives an extension which it recognizes and
117	// which is not specified for the message in which it appears, it MUST
118	// abort the handshake with an "illegal_parameter" alert.
119	//
120	// Note that we cannot encounter any extensions that we don't recognize here,
121	// since only extensions we previously offered are allowed in EE.
122	const auto allowed_exts = std::set<Extension_Code>{	481✔
123	// Allowed extensions listed in RFC 8446 and implemented in Botan
124	Extension_Code::ServerNameIndication,
125	// MAX_FRAGMENT_LENGTH
126	Extension_Code::SupportedGroups,
127	Extension_Code::UseSrtp,
128	// HEARTBEAT
129	Extension_Code::ApplicationLayerProtocolNegotiation,
130	// RFC 7250
131	Extension_Code::ClientCertificateType,
132	Extension_Code::ServerCertificateType,
133	// EARLY_DATA
134
135	// Allowed extensions not listed in RFC 8446 but acceptable as Botan implements them
136	Extension_Code::RecordSizeLimit,
137	};	481✔
138	if(m_extensions.contains_implemented_extensions_other_than(allowed_exts)) {	481✔
139	throw TLS_Exception(Alert::IllegalParameter, "Encrypted Extensions contained an extension that is not allowed");	5✔
140	}
141	}	486✔
142
143	std::vector<uint8_t> Encrypted_Extensions::serialize() const {	402✔
144	return m_extensions.serialize(Connection_Side::Server);	402✔
145	}
146
147	} // namespace Botan::TLS

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