. /include/boost/corosio /tls_stream.hpp
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1   // 1   //
2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com) 2   // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3   // Copyright (c) 2026 Michael Vandeberg 3   // Copyright (c) 2026 Michael Vandeberg
4   // Copyright (c) 2026 Steve Gerbino 4   // Copyright (c) 2026 Steve Gerbino
5   // 5   //
6   // Distributed under the Boost Software License, Version 1.0. (See accompanying 6   // Distributed under the Boost Software License, Version 1.0. (See accompanying
7   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 7   // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
8   // 8   //
9   // Official repository: https://github.com/cppalliance/corosio 9   // Official repository: https://github.com/cppalliance/corosio
10   // 10   //
11   11  
12   #ifndef BOOST_COROSIO_TLS_STREAM_HPP 12   #ifndef BOOST_COROSIO_TLS_STREAM_HPP
13   #define BOOST_COROSIO_TLS_STREAM_HPP 13   #define BOOST_COROSIO_TLS_STREAM_HPP
14   14  
15   #include <boost/corosio/detail/config.hpp> 15   #include <boost/corosio/detail/config.hpp>
16   #include <boost/capy/buffers.hpp> 16   #include <boost/capy/buffers.hpp>
17   #include <boost/capy/detail/buffer_array.hpp> 17   #include <boost/capy/detail/buffer_array.hpp>
18   #include <boost/capy/io/any_stream.hpp> 18   #include <boost/capy/io/any_stream.hpp>
19   #include <boost/capy/io_task.hpp> 19   #include <boost/capy/io_task.hpp>
20   20  
21   #include <cstddef> 21   #include <cstddef>
22   #include <string_view> 22   #include <string_view>
23   23  
24   namespace boost::corosio { 24   namespace boost::corosio {
25   25  
26   /** TLS handshake role. 26   /** TLS handshake role.
27   27  
28   Specifies whether to perform the TLS handshake as a client or server. 28   Specifies whether to perform the TLS handshake as a client or server.
29   29  
30   @see tls_stream::handshake 30   @see tls_stream::handshake
31   */ 31   */
32   enum class tls_role 32   enum class tls_role
33   { 33   {
34   /// Perform handshake as the connecting client. 34   /// Perform handshake as the connecting client.
35   client, 35   client,
36   36  
37   /// Perform handshake as the accepting server. 37   /// Perform handshake as the accepting server.
38   server 38   server
39   }; 39   };
40   40  
41 - /** Abstract base class for TLS streams. 41 + /** Reads, writes, and manages the handshake lifecycle of a TLS
  42 + session over an underlying stream.
42   43  
43   This class provides a runtime-polymorphic interface for TLS 44   This class provides a runtime-polymorphic interface for TLS
44 - implementations. Derived classes (openssl_stream, wolfssl_stream) 45 + implementations. Derived classes (`openssl_stream`, `wolfssl_stream`)
45   implement the virtual functions to provide backend-specific 46   implement the virtual functions to provide backend-specific
46   TLS functionality. 47   TLS functionality.
47   48  
48 - Unlike @ref io_stream which represents OS-level I/O completed 49 + An @ref io_stream represents OS-level I/O completed by the kernel.
49 - by the kernel, TLS streams are coroutine-based: their operations 50 + TLS streams are coroutine-based instead: their operations are
50 - are implemented as coroutines that orchestrate sub-operations 51 + coroutines that orchestrate sub-operations on the underlying stream.
51 - on the underlying stream.  
52   52  
53   The non-virtual template wrappers (`read_some`, `write_some`) 53   The non-virtual template wrappers (`read_some`, `write_some`)
54   satisfy the `capy::Stream` concept, enabling TLS streams to 54   satisfy the `capy::Stream` concept, enabling TLS streams to
55   be used anywhere a Stream is expected. 55   be used anywhere a Stream is expected.
56   56  
57   @par Thread Safety 57   @par Thread Safety
58   Distinct objects: Safe.@n 58   Distinct objects: Safe.@n
59   Shared objects: Unsafe, with one exception: one read operation and 59   Shared objects: Unsafe, with one exception: one read operation and
60   one write operation may be in flight simultaneously. `shutdown()` 60   one write operation may be in flight simultaneously. `shutdown()`
61 - may overlap a pending read. When the execution context runs on 61 + may overlap a pending read. On a multi-threaded execution context,
62 - multiple threads, all operations on one stream must be performed 62 + all operations on one stream must run within the same
63 - within the same `capy::strand` (or otherwise never run 63 + `capy::strand`, or must otherwise never run concurrently. A
64 - concurrently); a single-threaded context needs no strand. 64 + single-threaded context needs no strand.
65   65  
66   @see openssl_stream, wolfssl_stream 66   @see openssl_stream, wolfssl_stream
67   */ 67   */
68   class BOOST_COROSIO_DECL tls_stream 68   class BOOST_COROSIO_DECL tls_stream
69   { 69   {
70   public: 70   public:
71   /// Destroy the TLS stream. 71   /// Destroy the TLS stream.
72   virtual ~tls_stream() = default; 72   virtual ~tls_stream() = default;
73   73  
74 - tls_stream(tls_stream const&) = delete; 74 + /// Copy construction is disabled; copying a stream would slice the derived session.
  75 + tls_stream(tls_stream const&) = delete;
  76 + /// Copy assignment is disabled; copying a stream would slice the derived session.
75   tls_stream& operator=(tls_stream const&) = delete; 77   tls_stream& operator=(tls_stream const&) = delete;
76   78  
77   /** Initiate an asynchronous read operation. 79   /** Initiate an asynchronous read operation.
78   80  
79   Reads decrypted data into the provided buffer sequence. The 81   Reads decrypted data into the provided buffer sequence. The
80 - operation completes when at least one byte has been read, 82 + operation completes when it reads at least one byte,
81   or an error occurs. 83   or an error occurs.
82   84  
83   This non-virtual template wrapper satisfies the `capy::Stream` 85   This non-virtual template wrapper satisfies the `capy::Stream`
84   concept by delegating to the virtual `do_read_some`. 86   concept by delegating to the virtual `do_read_some`.
85   87  
86   @par Thread Safety 88   @par Thread Safety
87   May run concurrently with one operation in the other 89   May run concurrently with one operation in the other
88   direction, subject to the class-level threading contract. 90   direction, subject to the class-level threading contract.
89   Two concurrent operations in the same direction are 91   Two concurrent operations in the same direction are
90   undefined. 92   undefined.
91   93  
92   @param buffers The buffer sequence to read data into. 94   @param buffers The buffer sequence to read data into.
93   95  
94   @return An awaitable yielding `(error_code,std::size_t)`. 96   @return An awaitable yielding `(error_code,std::size_t)`.
95   */ 97   */
96   template<capy::MutableBufferSequence Buffers> 98   template<capy::MutableBufferSequence Buffers>
MISUBC 97   ✗ [[nodiscard]] auto read_some(Buffers const& buffers) 99   ✗ [[nodiscard]] auto read_some(Buffers const& buffers)
98   { 100   {
MISUBC 99   ✗ return do_read_some(buffers); 101   ✗ return do_read_some(buffers);
100   } 102   }
101   103  
102   /** Initiate an asynchronous write operation. 104   /** Initiate an asynchronous write operation.
103   105  
104   Encrypts and writes data from the provided buffer sequence. 106   Encrypts and writes data from the provided buffer sequence.
105 - The operation completes when at least one byte has been 107 + The operation completes when it writes at least one byte,
106 - written, or an error occurs. 108 + or an error occurs.
107   109  
108   This non-virtual template wrapper satisfies the `capy::Stream` 110   This non-virtual template wrapper satisfies the `capy::Stream`
109   concept by delegating to the virtual `do_write_some`. 111   concept by delegating to the virtual `do_write_some`.
110   112  
111   @par Thread Safety 113   @par Thread Safety
112   May run concurrently with one operation in the other 114   May run concurrently with one operation in the other
113   direction, subject to the class-level threading contract. 115   direction, subject to the class-level threading contract.
114   Two concurrent operations in the same direction are 116   Two concurrent operations in the same direction are
115   undefined. 117   undefined.
116   118  
117   @param buffers The buffer sequence containing data to write. 119   @param buffers The buffer sequence containing data to write.
118   120  
119   @return An awaitable yielding `(error_code,std::size_t)`. 121   @return An awaitable yielding `(error_code,std::size_t)`.
120   */ 122   */
121   template<capy::ConstBufferSequence Buffers> 123   template<capy::ConstBufferSequence Buffers>
MISUBC 122   ✗ [[nodiscard]] auto write_some(Buffers const& buffers) 124   ✗ [[nodiscard]] auto write_some(Buffers const& buffers)
123   { 125   {
MISUBC 124   ✗ return do_write_some(buffers); 126   ✗ return do_write_some(buffers);
125   } 127   }
126   128  
127   /** Asynchronously perform the TLS handshake. 129   /** Asynchronously perform the TLS handshake.
128   130  
129   Initiates the TLS handshake process. For client connections, 131   Initiates the TLS handshake process. For client connections,
130   this sends the ClientHello and processes the server's response. 132   this sends the ClientHello and processes the server's response.
131   For server connections, this waits for the ClientHello and 133   For server connections, this waits for the ClientHello and
132   sends the server's response. 134   sends the server's response.
133   135  
134 - A handshake attempt, successful or not, consumes the stream 136 + A handshake attempt consumes the stream state, whether it
135 - state: a subsequent call behaves as if `reset()` had been 137 + succeeds or not. A subsequent call behaves as if `reset()` ran
136 - called first and performs a fresh handshake using the 138 + first, and performs a fresh handshake using the current
137 - current configuration. 139 + configuration.
138   140  
139 - @par Preconditions 141 + @pre The underlying stream must be connected. No other TLS
140 - The underlying stream must be connected. No other TLS 142 + operation may be in progress on this stream.
141 - operation may be in progress on this stream.  
142   143  
143   @param role The handshake role, client or server. 144   @param role The handshake role, client or server.
144   145  
145   @return An awaitable yielding `(error_code)`. 146   @return An awaitable yielding `(error_code)`.
146   */ 147   */
147   [[nodiscard]] virtual capy::io_task<> handshake(tls_role role) = 0; 148   [[nodiscard]] virtual capy::io_task<> handshake(tls_role role) = 0;
148   149  
149   /** Asynchronously perform a graceful TLS shutdown. 150   /** Asynchronously perform a graceful TLS shutdown.
150   151  
151   Initiates the TLS shutdown sequence by sending a close_notify 152   Initiates the TLS shutdown sequence by sending a close_notify
152   alert and waiting for the peer's close_notify response. 153   alert and waiting for the peer's close_notify response.
153   154  
154 - @par Preconditions 155 + @pre A handshake must have completed successfully. May overlap
155 - A handshake must have completed successfully. May overlap 156 + a pending read. No concurrent write may be in progress.
156 - a pending read. No concurrent write may be in progress.  
157   157  
158   @par Postconditions 158   @par Postconditions
159 - If the transport ends before the peer's close_notify is 159 + If the transport ends before the peer's close_notify arrives,
160 - received, the result is `capy::error::stream_truncated`, not 160 + the result is `capy::error::stream_truncated`, not success. An
161 - success: an unannounced close is indistinguishable from a 161 + unannounced close is indistinguishable from a truncation attack,
162 - truncation attack and must not be reported as a clean 162 + so it must not be reported as a clean shutdown. A shutdown
163 - shutdown. A shutdown stopped mid-flight reports canceled; 163 + stopped mid-flight reports canceled. Any other transport
164 - any other transport error propagates unchanged. 164 + error propagates unchanged.
165   165  
166   @return An awaitable yielding `(error_code)`. 166   @return An awaitable yielding `(error_code)`.
167   */ 167   */
168   [[nodiscard]] virtual capy::io_task<> shutdown() = 0; 168   [[nodiscard]] virtual capy::io_task<> shutdown() = 0;
169   169  
170   /** Reset TLS session state for reuse. 170   /** Reset TLS session state for reuse.
171   171  
172   Releases TLS session state including session keys and peer 172   Releases TLS session state including session keys and peer
173   certificates, returning the stream to a state where 173   certificates, returning the stream to a state where
174   `handshake()` can be called again. Internal memory 174   `handshake()` can be called again. Internal memory
175   allocations (I/O buffers) are preserved. 175   allocations (I/O buffers) are preserved.
176   176  
177   Calling `handshake()` on a previously-used stream 177   Calling `handshake()` on a previously-used stream
178   implicitly performs a reset first, so explicit calls 178   implicitly performs a reset first, so explicit calls
179   are only needed to eagerly release session state. 179   are only needed to eagerly release session state.
180   180  
181 - @par Preconditions 181 + @pre No TLS operation (handshake, read, write, shutdown) is
182 - No TLS operation (handshake, read, write, shutdown) is 182 + in progress.
183 - in progress.  
184   183  
185   @par Thread Safety 184   @par Thread Safety
186   Not thread safe. The caller must ensure no concurrent 185   Not thread safe. The caller must ensure no concurrent
187   operations are in progress on this stream. 186   operations are in progress on this stream.
188   187  
189   @note If called mid-session before `shutdown()`, pending 188   @note If called mid-session before `shutdown()`, pending
190 - TLS data is discarded and the peer will observe a 189 + TLS data is discarded and the peer observes a
191   truncated stream. 190   truncated stream.
192   */ 191   */
193   virtual void reset() = 0; 192   virtual void reset() = 0;
194   193  
195   /** Set the peer hostname for SNI and certificate verification. 194   /** Set the peer hostname for SNI and certificate verification.
196   195  
197   Configures the hostname sent in the TLS Server Name 196   Configures the hostname sent in the TLS Server Name
198   Indication extension and matched against the peer 197   Indication extension and matched against the peer
199   certificate during verification. The value takes effect 198   certificate during verification. The value takes effect
200   at the next `handshake()`; an established session is not 199   at the next `handshake()`; an established session is not
201   affected. It persists across `reset()`, so a stream reused 200   affected. It persists across `reset()`, so a stream reused
202   to reach a different host must set the new name before 201   to reach a different host must set the new name before
203   handshaking again. 202   handshaking again.
204   203  
205   An empty hostname (the default) disables SNI and hostname 204   An empty hostname (the default) disables SNI and hostname
206   verification. 205   verification.
207   206  
208   If `hostname` is an IP literal (IPv4 or IPv6), it is matched 207   If `hostname` is an IP literal (IPv4 or IPv6), it is matched
209 - against the certificate's iPAddress entries instead of its 208 + against the certificate's iPAddress entries instead of its DNS
210 - DNS names, and no SNI is sent (RFC 6066 excludes literals). 209 + names. No SNI is sent, because RFC 6066 excludes literals.
211   A backend build that cannot match iPAddress entries fails the 210   A backend build that cannot match iPAddress entries fails the
212   handshake with `std::errc::function_not_supported` rather 211   handshake with `std::errc::function_not_supported` rather
213   than skip verification. 212   than skip verification.
214   213  
215   @par Postconditions 214   @par Postconditions
216   The next `handshake()` uses `hostname` for SNI and 215   The next `handshake()` uses `hostname` for SNI and
217   certificate verification, or neither if it is empty. 216   certificate verification, or neither if it is empty.
218   217  
219   @note The hostname is used for client handshakes only; 218   @note The hostname is used for client handshakes only;
220   it is ignored when handshaking as a server. 219   it is ignored when handshaking as a server.
221   220  
222   @param hostname The peer hostname, or empty to disable. 221   @param hostname The peer hostname, or empty to disable.
223   */ 222   */
224   virtual void set_hostname(std::string_view hostname) = 0; 223   virtual void set_hostname(std::string_view hostname) = 0;
225   224  
226   /** Return a reference to the underlying stream. 225   /** Return a reference to the underlying stream.
227   226  
228   Provides access to the type-erased underlying stream for 227   Provides access to the type-erased underlying stream for
229   operations like cancellation or accessing native handles. 228   operations like cancellation or accessing native handles.
230   229  
231   @warning Do not reseat (assign to) the returned reference. 230   @warning Do not reseat (assign to) the returned reference.
232   The TLS implementation holds internal state bound to 231   The TLS implementation holds internal state bound to
233   the original stream. Replacing it causes undefined 232   the original stream. Replacing it causes undefined
234   behavior. 233   behavior.
235   234  
236   @return Reference to the wrapped stream. 235   @return Reference to the wrapped stream.
237   */ 236   */
238   virtual capy::any_stream& next_layer() noexcept = 0; 237   virtual capy::any_stream& next_layer() noexcept = 0;
239   238  
240   /** Return a const reference to the underlying stream. 239   /** Return a const reference to the underlying stream.
241   240  
242   @return Const reference to the wrapped stream. 241   @return Const reference to the wrapped stream.
243   */ 242   */
244   virtual capy::any_stream const& next_layer() const noexcept = 0; 243   virtual capy::any_stream const& next_layer() const noexcept = 0;
245   244  
246   /** Return the name of the TLS backend. 245   /** Return the name of the TLS backend.
247   246  
248   @return A string identifying the TLS implementation, 247   @return A string identifying the TLS implementation,
249   such as "openssl" or "wolfssl". 248   such as "openssl" or "wolfssl".
250   */ 249   */
251   virtual std::string_view name() const noexcept = 0; 250   virtual std::string_view name() const noexcept = 0;
252   251  
253   /** Return the ALPN protocol negotiated during the handshake. 252   /** Return the ALPN protocol negotiated during the handshake.
254   253  
255   Application-Layer Protocol Negotiation selects a single 254   Application-Layer Protocol Negotiation selects a single
256   application protocol (for example `"h2"` or `"http/1.1"`) 255   application protocol (for example `"h2"` or `"http/1.1"`)
257   during the TLS handshake, from the list supplied via 256   during the TLS handshake, from the list supplied via
258   @ref tls_context::set_alpn. 257   @ref tls_context::set_alpn.
259   258  
260 - @return The negotiated protocol, or an empty view if no 259 + @return The negotiated protocol, or an empty view. It is empty
261 - protocol was negotiated, ALPN was not offered, the 260 + if no protocol was negotiated or ALPN was not offered. It is
262 - handshake has not completed, or the backend/build does 261 + also empty if the handshake has not completed, or if the build
263 - not support ALPN. 262 + lacks ALPN support.
264   263  
265   @par Thread Safety 264   @par Thread Safety
266   Safe to call after the handshake completes; not safe to call 265   Safe to call after the handshake completes; not safe to call
267   concurrently with a handshake or reset. 266   concurrently with a handshake or reset.
268   */ 267   */
269   virtual std::string_view alpn_protocol() const noexcept 268   virtual std::string_view alpn_protocol() const noexcept
270   { 269   {
271   return {}; 270   return {};
272   } // LCOV_EXCL_LINE every concrete stream overrides this; the base default is never called 271   } // LCOV_EXCL_LINE every concrete stream overrides this; the base default is never called
273   272  
274   protected: 273   protected:
  274 + /// Default construct; a derived class supplies the session.
275   tls_stream() = default; 275   tls_stream() = default;
276   276  
277 - /** Virtual read implementation. 277 + /** Perform the backend-specific decrypted read.
278   278  
279   Derived classes override this to perform TLS decryption 279   Derived classes override this to perform TLS decryption
280   and read operations. 280   and read operations.
281   281  
282   @param buffers Buffer sequence to read into. 282   @param buffers Buffer sequence to read into.
283   283  
284   @return An awaitable yielding `(error_code,std::size_t)`. 284   @return An awaitable yielding `(error_code,std::size_t)`.
285   */ 285   */
286   virtual capy::io_task<std::size_t> do_read_some( 286   virtual capy::io_task<std::size_t> do_read_some(
287   capy::detail::mutable_buffer_array<capy::detail::max_iovec_> 287   capy::detail::mutable_buffer_array<capy::detail::max_iovec_>
288   buffers) = 0; 288   buffers) = 0;
289   289  
290 - /** Virtual write implementation. 290 + /** Perform the backend-specific encrypted write.
291   291  
292   Derived classes override this to perform TLS encryption 292   Derived classes override this to perform TLS encryption
293   and write operations. 293   and write operations.
294   294  
295   @param buffers Buffer sequence to write from. 295   @param buffers Buffer sequence to write from.
296   296  
297   @return An awaitable yielding `(error_code,std::size_t)`. 297   @return An awaitable yielding `(error_code,std::size_t)`.
298   */ 298   */
299   virtual capy::io_task<std::size_t> do_write_some( 299   virtual capy::io_task<std::size_t> do_write_some(
300   capy::detail::const_buffer_array<capy::detail::max_iovec_> buffers) = 0; 300   capy::detail::const_buffer_array<capy::detail::max_iovec_> buffers) = 0;
301   }; 301   };
302   302  
303   } // namespace boost::corosio 303   } // namespace boost::corosio
304   304  
305   #endif 305   #endif