TLA Line data Source code
1 : //
2 : // Copyright (c) 2025 Vinnie Falco (vinnie.falco@gmail.com)
3 : // Copyright (c) 2026 Michael Vandeberg
4 : //
5 : // Distributed under the Boost Software License, Version 1.0. (See accompanying
6 : // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 : //
8 : // Official repository: https://github.com/cppalliance/corosio
9 : //
10 :
11 : #ifndef BOOST_COROSIO_TLS_CONTEXT_HPP
12 : #define BOOST_COROSIO_TLS_CONTEXT_HPP
13 :
14 : #include <boost/corosio/detail/config.hpp>
15 :
16 : #include <cstddef>
17 : #include <functional>
18 : #include <span>
19 : #include <system_error>
20 : #include <memory>
21 : #include <string_view>
22 :
23 : namespace boost::corosio {
24 :
25 : //
26 : // Enumerations
27 : //
28 :
29 : /** TLS protocol version.
30 :
31 : Specifies the minimum or maximum TLS protocol version to use
32 : for connections. Only modern, secure versions are supported.
33 :
34 : @see tls_context::set_min_protocol_version
35 : @see tls_context::set_max_protocol_version
36 : */
37 : enum class tls_version
38 : {
39 : /// TLS 1.2 (RFC 5246).
40 : tls_1_2,
41 :
42 : /// TLS 1.3 (RFC 8446).
43 : tls_1_3
44 : };
45 :
46 : /** Certificate and key file format.
47 :
48 : Specifies the encoding format for certificate and key data.
49 :
50 : @see tls_context::use_certificate
51 : @see tls_context::use_private_key
52 : */
53 : enum class tls_file_format
54 : {
55 : /// PEM format (Base64-encoded with header/footer lines).
56 : pem,
57 :
58 : /// DER format (raw ASN.1 binary encoding).
59 : der
60 : };
61 :
62 : /** Peer certificate verification mode.
63 :
64 : Controls how the TLS implementation verifies the peer's
65 : certificate during the handshake.
66 :
67 : @see tls_context::set_verify_mode
68 : */
69 : enum class tls_verify_mode
70 : {
71 : /// Do not request or verify the peer certificate.
72 : none,
73 :
74 : /// Request and verify the peer certificate if presented.
75 : peer,
76 :
77 : /// Require and verify the peer certificate (fail if not presented).
78 : require_peer
79 : };
80 :
81 : /** Certificate revocation checking policy.
82 :
83 : Controls how certificate revocation status is checked during
84 : verification.
85 :
86 : @see tls_context::set_revocation_policy
87 : */
88 : enum class tls_revocation_policy
89 : {
90 : /// Do not check revocation status.
91 : disabled,
92 :
93 : /// Check revocation but allow connection if status is unknown.
94 : soft_fail,
95 :
96 : /// Require successful revocation check (fail if status is unknown).
97 : hard_fail
98 : };
99 :
100 : /** Purpose for password callback invocation.
101 :
102 : Indicates whether the password is needed for reading (decrypting)
103 : or writing (encrypting) key material.
104 :
105 : @see tls_context::set_password_callback
106 : */
107 : enum class tls_password_purpose
108 : {
109 : /// Password needed to decrypt/read protected key material.
110 : for_reading,
111 :
112 : /// Password needed to encrypt/write protected key material.
113 : for_writing
114 : };
115 :
116 : class tls_context;
117 :
118 : /** A non-owning view of certificate verification state.
119 :
120 : An instance is passed to the callback installed via
121 : tls_context::set_verify_callback during the TLS handshake. It
122 : exposes the backend's native verification handle so the callback
123 : can inspect the certificate and chain currently being verified.
124 :
125 : The value returned by native_handle() is, for the OpenSSL and
126 : WolfSSL backends, an `X509_STORE_CTX*`. For portable inspection that
127 : works across backends (for example certificate pinning), prefer
128 : certificate(), which returns the DER encoding of the certificate
129 : currently being verified.
130 :
131 : @par Lifetime
132 :
133 : The wrapped handle and the certificate() bytes are owned by the TLS
134 : backend and are valid only for the duration of a single callback
135 : invocation. Do not retain them beyond the call.
136 :
137 : @see tls_context::set_verify_callback
138 : */
139 : class verify_context
140 : {
141 : void* handle_;
142 : unsigned char const* der_;
143 : std::size_t der_len_;
144 :
145 : public:
146 : /** Construct from a native handle and the current certificate.
147 :
148 : @param handle The backend verification handle (for OpenSSL and
149 : WolfSSL, an `X509_STORE_CTX*`).
150 : @param der Pointer to the DER encoding of the certificate under
151 : verification, or `nullptr` if unavailable.
152 : @param der_len Length of the DER encoding in bytes.
153 : */
154 : verify_context(
155 : void* handle, unsigned char const* der, std::size_t der_len) noexcept
156 : : handle_(handle), der_(der), der_len_(der_len)
157 : {
158 : }
159 :
160 : /** Return the native verification handle.
161 :
162 : Cast the result to the backend's verification context type
163 : (e.g. `X509_STORE_CTX*`) to inspect the certificate chain using
164 : backend-specific APIs.
165 :
166 : @return The native handle, or `nullptr` if none is available.
167 : */
168 : void* native_handle() const noexcept { return handle_; }
169 :
170 : /** Return the DER encoding of the certificate being verified.
171 :
172 : This is the portable way to inspect the peer certificate from a
173 : verification callback: it works identically on every backend,
174 : without depending on backend-specific build options. A DER
175 : certificate is an ASN.1 `SEQUENCE`, so the first byte is `0x30`.
176 :
177 : @return A view of the certificate's DER bytes, valid only for the
178 : duration of the callback. Empty if the certificate is not
179 : available.
180 : */
181 : std::span<unsigned char const> certificate() const noexcept
182 : {
183 : return {der_, der_len_};
184 : }
185 : };
186 :
187 : namespace detail {
188 : struct tls_context_data;
189 : tls_context_data const& get_tls_context_data(tls_context const&) noexcept;
190 : } // namespace detail
191 :
192 : /** A portable TLS context for certificate and settings storage.
193 :
194 : The `tls_context` class provides a backend-agnostic interface for
195 : configuring TLS connections. It stores credentials (certificates and
196 : private keys), trust anchors, protocol settings, and verification
197 : options that are used when establishing TLS connections.
198 :
199 : This class is a shared handle to an opaque implementation. Copies
200 : share the same underlying state. This allows contexts to be passed
201 : by value and shared across multiple TLS streams.
202 :
203 : This class abstracts the configuration phase of TLS across multiple
204 : backend implementations (OpenSSL, WolfSSL, mbedTLS, Schannel, etc.),
205 : allowing portable code that works regardless of which TLS library
206 : is linked.
207 :
208 : @par Modification After Stream Creation
209 :
210 : Modifying a context after a TLS stream has been created from it
211 : results in undefined behavior. The context's configuration is
212 : captured when the first stream is constructed, and subsequent
213 : modifications are not reflected in existing or new streams
214 : sharing the context.
215 :
216 : If different configurations are needed, create separate context
217 : objects.
218 :
219 : @par Thread Safety
220 :
221 : Distinct objects: Safe.
222 :
223 : Shared objects: Unsafe. A context must not be modified while
224 : any thread is creating streams from it.
225 :
226 : @par Example
227 : @code
228 : // Create a client context with system trust anchors
229 : corosio::tls_context ctx;
230 : ctx.set_default_verify_paths();
231 : ctx.set_verify_mode( corosio::tls_verify_mode::peer );
232 :
233 : // Use with a TLS stream
234 : corosio::openssl_stream secure( &sock, ctx );
235 : secure.set_hostname( "example.com" );
236 : co_await secure.handshake( corosio::tls_role::client );
237 : @endcode
238 :
239 : @see tls_role
240 : */
241 : #ifdef _MSC_VER
242 : #pragma warning(push)
243 : #pragma warning(disable : 4251) // shared_ptr needs dll-interface
244 : #endif
245 : class BOOST_COROSIO_DECL tls_context
246 : {
247 : struct impl;
248 : std::shared_ptr<impl> impl_;
249 :
250 : friend detail::tls_context_data const&
251 : detail::get_tls_context_data(tls_context const&) noexcept;
252 :
253 : public:
254 : /** Construct a default TLS context.
255 :
256 : Creates a context with default settings suitable for TLS 1.2
257 : and TLS 1.3 connections. No certificates or trust anchors are
258 : loaded; call the appropriate methods to configure credentials
259 : and verification.
260 :
261 : @par Example
262 : @code
263 : corosio::tls_context ctx;
264 : @endcode
265 : */
266 : tls_context();
267 :
268 : /** Copy constructor.
269 :
270 : Creates a new handle that shares ownership of the underlying
271 : TLS context state with `other`.
272 :
273 : @param other The context to copy from.
274 : */
275 HIT 1 : tls_context(tls_context const& other) = default;
276 :
277 : /** Copy assignment operator.
278 :
279 : Releases the current context's shared ownership and acquires
280 : shared ownership of `other`'s underlying state.
281 :
282 : @param other The context to copy from.
283 :
284 : @return Reference to this context.
285 : */
286 1 : tls_context& operator=(tls_context const& other) = default;
287 :
288 : /** Move constructor.
289 :
290 : Transfers ownership of the TLS context from another instance.
291 : After the move, `other` is in a valid but empty state.
292 :
293 : @param other The context to move from.
294 : */
295 1 : tls_context(tls_context&& other) noexcept = default;
296 :
297 : /** Move assignment operator.
298 :
299 : Releases the current context's shared ownership and transfers
300 : ownership from another instance. After the move, `other` is
301 : in a valid but empty state.
302 :
303 : @param other The context to move from.
304 :
305 : @return Reference to this context.
306 : */
307 1 : tls_context& operator=(tls_context&& other) noexcept = default;
308 :
309 : /** Destructor.
310 :
311 : Releases this handle's shared ownership of the underlying
312 : context. The context state is destroyed when the last handle
313 : is released.
314 : */
315 33 : ~tls_context() = default;
316 :
317 : //
318 : // Credential Loading
319 : //
320 :
321 : /** Load the entity certificate from a memory buffer.
322 :
323 : Sets the certificate that identifies this endpoint to the peer.
324 : For servers, this is the server certificate. For clients using
325 : mutual TLS, this is the client certificate.
326 :
327 : The certificate must match the private key loaded via
328 : `use_private_key()` or `use_private_key_file()`.
329 :
330 : @param certificate The certificate data.
331 :
332 : @param format The encoding format of the certificate data.
333 :
334 : @return Success, or an error if the certificate could not be parsed
335 : or is invalid.
336 :
337 : @see use_certificate_file
338 : @see use_private_key
339 : */
340 : std::error_code
341 : use_certificate(std::string_view certificate, tls_file_format format);
342 :
343 : /** Load the entity certificate from a file.
344 :
345 : Sets the certificate that identifies this endpoint to the peer.
346 : For servers, this is the server certificate. For clients using
347 : mutual TLS, this is the client certificate.
348 :
349 : @param filename Path to the certificate file.
350 :
351 : @param format The encoding format of the file.
352 :
353 : @return Success, or an error if the file could not be read or the
354 : certificate is invalid.
355 :
356 : @par Example
357 : @code
358 : ctx.use_certificate_file( "server.crt", tls_file_format::pem );
359 : @endcode
360 :
361 : @see use_certificate
362 : @see use_private_key_file
363 : */
364 : std::error_code
365 : use_certificate_file(std::string_view filename, tls_file_format format);
366 :
367 : /** Load a certificate chain from a memory buffer.
368 :
369 : Loads the entity certificate followed by intermediate CA certificates.
370 : The chain should be ordered from leaf to root (excluding the root).
371 : This is the typical format for PEM certificate bundles.
372 :
373 : @param chain The certificate chain data in PEM format (concatenated
374 : certificates).
375 :
376 : @return Success, or an error if the chain could not be parsed.
377 :
378 : @see use_certificate_chain_file
379 : */
380 : std::error_code use_certificate_chain(std::string_view chain);
381 :
382 : /** Load a certificate chain from a file.
383 :
384 : Loads the entity certificate followed by intermediate CA certificates
385 : from a PEM file. The file should contain concatenated PEM certificates
386 : ordered from leaf to root (excluding the root).
387 :
388 : @param filename Path to the certificate chain file.
389 :
390 : @return Success, or an error if the file could not be read or parsed.
391 :
392 : @par Example
393 : @code
394 : // Load certificate chain (cert + intermediates)
395 : ctx.use_certificate_chain_file( "fullchain.pem" );
396 : @endcode
397 :
398 : @see use_certificate_chain
399 : */
400 : std::error_code use_certificate_chain_file(std::string_view filename);
401 :
402 : /** Load the private key from a memory buffer.
403 :
404 : Sets the private key corresponding to the entity certificate.
405 : The key must match the certificate loaded via `use_certificate()`
406 : or `use_certificate_chain()`.
407 :
408 : If the key is encrypted, set a password callback via
409 : `set_password_callback()` before calling this function.
410 :
411 : @param private_key The private key data.
412 :
413 : @param format The encoding format of the key data.
414 :
415 : @return Success, or an error if the key could not be parsed,
416 : is encrypted without a password callback, or doesn't match
417 : the certificate.
418 :
419 : @see use_private_key_file
420 : @see set_password_callback
421 : */
422 : std::error_code
423 : use_private_key(std::string_view private_key, tls_file_format format);
424 :
425 : /** Load the private key from a file.
426 :
427 : Sets the private key corresponding to the entity certificate.
428 : The key must match the certificate loaded via `use_certificate_file()`
429 : or `use_certificate_chain_file()`.
430 :
431 : If the key file is encrypted, set a password callback via
432 : `set_password_callback()` before calling this function.
433 :
434 : @param filename Path to the private key file.
435 :
436 : @param format The encoding format of the file.
437 :
438 : @return Success, or an error if the file could not be read,
439 : the key is invalid, or it doesn't match the certificate.
440 :
441 : @par Example
442 : @code
443 : ctx.use_private_key_file( "server.key", tls_file_format::pem );
444 : @endcode
445 :
446 : @see use_private_key
447 : @see set_password_callback
448 : */
449 : std::error_code
450 : use_private_key_file(std::string_view filename, tls_file_format format);
451 :
452 : /** Load credentials from a PKCS#12 bundle in memory.
453 :
454 : PKCS#12 (also known as PFX) is a binary format that bundles a
455 : certificate, private key, and optionally intermediate certificates
456 : into a single password-protected file.
457 :
458 : @param data The PKCS#12 bundle data.
459 :
460 : @param passphrase The password protecting the bundle.
461 :
462 : @return Success. The bundle is recorded and decoded into the
463 : certificate, private key, and chain when the native context is
464 : first built; a malformed bundle or wrong passphrase surfaces as
465 : a handshake failure.
466 :
467 : @note Intermediate certificates inside the bundle are loaded and
468 : sent during the handshake on both backends.
469 :
470 : @see use_pkcs12_file
471 : */
472 : std::error_code
473 : use_pkcs12(std::string_view data, std::string_view passphrase);
474 :
475 : /** Load credentials from a PKCS#12 file.
476 :
477 : PKCS#12 (also known as PFX) is a binary format that bundles a
478 : certificate, private key, and optionally intermediate certificates
479 : into a single password-protected file. This is common on Windows
480 : and for certificates exported from browsers.
481 :
482 : @param filename Path to the PKCS#12 file.
483 :
484 : @param passphrase The password protecting the file.
485 :
486 : @return Success, or an error if the file could not be read. The
487 : bundle is decoded when the native context is first built; a
488 : malformed bundle or wrong passphrase surfaces as a handshake
489 : failure.
490 :
491 : @note Intermediate certificates inside the bundle are loaded and
492 : sent during the handshake on both backends.
493 :
494 : @par Example
495 : @code
496 : ctx.use_pkcs12_file( "credentials.pfx", "secret" );
497 : @endcode
498 :
499 : @see use_pkcs12
500 : */
501 : std::error_code
502 : use_pkcs12_file(std::string_view filename, std::string_view passphrase);
503 :
504 : //
505 : // Trust Anchors
506 : //
507 :
508 : /** Add a certificate authority for peer verification.
509 :
510 : Adds a single CA certificate to the trust store used for verifying
511 : peer certificates. Call this multiple times to add multiple CAs,
512 : or use `load_verify_file()` for a bundle.
513 :
514 : @param ca The CA certificate data in PEM format.
515 :
516 : @return Success, or an error if the certificate could not be parsed.
517 :
518 : @see load_verify_file
519 : @see set_default_verify_paths
520 : */
521 : std::error_code add_certificate_authority(std::string_view ca);
522 :
523 : /** Load CA certificates from a file.
524 :
525 : Loads one or more CA certificates from a PEM file. The file may
526 : contain multiple concatenated PEM certificates.
527 :
528 : @param filename Path to a PEM file containing CA certificates.
529 :
530 : @return Success, or an error if the file could not be read or parsed.
531 :
532 : @par Example
533 : @code
534 : // Load a custom CA bundle
535 : ctx.load_verify_file( "/etc/ssl/certs/ca-certificates.crt" );
536 : @endcode
537 :
538 : @see add_certificate_authority
539 : @see add_verify_path
540 : */
541 : std::error_code load_verify_file(std::string_view filename);
542 :
543 : /** Add a directory of CA certificates for verification.
544 :
545 : Adds a directory of CA certificates to the trust store. The
546 : directory is applied when the native context is first built from
547 : this context.
548 :
549 : The expected directory layout depends on the backend. OpenSSL
550 : performs on-demand lookups and requires each certificate file to
551 : be named by its subject-name hash (as generated by
552 : `openssl rehash` or `c_rehash`); WolfSSL loads every certificate
553 : file in the directory.
554 :
555 : @param path Path to the directory of CA certificates.
556 :
557 : @return Success. The path is recorded and applied when the native
558 : context is built; a directory that cannot be read at that time
559 : is skipped rather than reported here.
560 :
561 : @par Example
562 : @code
563 : ctx.add_verify_path( "/etc/ssl/certs" );
564 : @endcode
565 :
566 : @see load_verify_file
567 : @see set_default_verify_paths
568 : */
569 : std::error_code add_verify_path(std::string_view path);
570 :
571 : /** Use the system default CA certificate store.
572 :
573 : Configures the context to use the operating system's default
574 : trust store for peer certificate verification. This is the
575 : recommended approach for HTTPS clients connecting to public
576 : servers.
577 :
578 : The system store is loaded when the native context is first built
579 : from this context. For a verified-safe client, combine this with
580 : `set_verify_mode( tls_verify_mode::peer )` and, when connecting by
581 : name, `tls_stream::set_hostname()`.
582 :
583 : @return Success. The request is recorded and applied when the
584 : native context is built; if the system store cannot be loaded
585 : at that time it is skipped rather than reported here, so a
586 : context that must reject unverified peers should also use
587 : `set_verify_mode( tls_verify_mode::peer )`.
588 :
589 : @note The OpenSSL backend honors the `SSL_CERT_FILE` and
590 : `SSL_CERT_DIR` environment variables. The WolfSSL backend
591 : requires a build with `WOLFSSL_SYS_CA_CERTS`; without it the
592 : system store is unavailable and this call has no effect.
593 :
594 : @par Example
595 : @code
596 : // Trust the same CAs as the system
597 : ctx.set_default_verify_paths();
598 : ctx.set_verify_mode( tls_verify_mode::peer );
599 : @endcode
600 :
601 : @see load_verify_file
602 : @see add_verify_path
603 : @see set_verify_mode
604 : */
605 : std::error_code set_default_verify_paths();
606 :
607 : //
608 : // Protocol Configuration
609 : //
610 :
611 : /** Set the minimum TLS protocol version.
612 :
613 : Connections will reject protocol versions older than this.
614 : The default allows TLS 1.2 and newer.
615 :
616 : @param v The minimum protocol version to accept.
617 :
618 : @return Success, or an error if the version is not supported
619 : by the backend.
620 :
621 : @par Example
622 : @code
623 : // Require TLS 1.3 minimum
624 : ctx.set_min_protocol_version( tls_version::tls_1_3 );
625 : @endcode
626 :
627 : @see set_max_protocol_version
628 : */
629 : std::error_code set_min_protocol_version(tls_version v);
630 :
631 : /** Set the maximum TLS protocol version.
632 :
633 : Connections will not negotiate protocol versions newer than this.
634 : The default allows the newest supported version.
635 :
636 : @param v The maximum protocol version to accept.
637 :
638 : @return Success, or an error if the version is not supported
639 : by the backend.
640 :
641 : @note On WolfSSL the ceiling is applied by selecting a
642 : version-specific method (no native set-max API exists); an
643 : invalid window where the minimum exceeds the maximum yields a
644 : context that fails the handshake.
645 :
646 : @see set_min_protocol_version
647 : */
648 : std::error_code set_max_protocol_version(tls_version v);
649 :
650 : /** Set the allowed cipher suites.
651 :
652 : Configures which cipher suites may be used for connections.
653 : The format is backend-specific but typically follows OpenSSL
654 : cipher list syntax.
655 :
656 : @param ciphers The cipher suite specification string.
657 :
658 : @return Success, or an error if the cipher string is invalid.
659 :
660 : @par Example
661 : @code
662 : // TLS 1.2 cipher suites (OpenSSL format)
663 : ctx.set_ciphersuites( "ECDHE+AESGCM:ECDHE+CHACHA20" );
664 : @endcode
665 :
666 : @note This configures cipher suites for TLS 1.2 and below. For
667 : TLS 1.3, use @ref set_ciphersuites_tls13.
668 : */
669 : std::error_code set_ciphersuites(std::string_view ciphers);
670 :
671 : /** Set the allowed TLS 1.3 cipher suites.
672 :
673 : TLS 1.3 uses a distinct, fixed set of cipher suites configured
674 : separately from earlier versions. The format is a colon-separated
675 : list of TLS 1.3 suite names.
676 :
677 : @param ciphers The TLS 1.3 cipher suite list.
678 :
679 : @return Success, or an error if the cipher string is invalid.
680 :
681 : @par Example
682 : @code
683 : ctx.set_ciphersuites_tls13(
684 : "TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256" );
685 : @endcode
686 :
687 : @note On the WolfSSL backend, TLS 1.2 and TLS 1.3 suites share a
688 : single cipher list; this call and @ref set_ciphersuites are
689 : merged into one list.
690 :
691 : @see set_ciphersuites
692 : */
693 : std::error_code set_ciphersuites_tls13(std::string_view ciphers);
694 :
695 : /** Set the ALPN protocol list.
696 :
697 : Configures Application-Layer Protocol Negotiation (ALPN) for
698 : the connection. ALPN is used to negotiate which application
699 : protocol to use over the TLS connection (e.g., "h2" for HTTP/2,
700 : "http/1.1" for HTTP/1.1).
701 :
702 : The protocols are tried in preference order (first = highest).
703 :
704 : @param protocols Ordered list of protocol identifiers.
705 :
706 : @return Success, or an error if ALPN configuration fails.
707 :
708 : @note Read the negotiated protocol after the handshake via
709 : @ref tls_stream::alpn_protocol. On WolfSSL, ALPN requires a
710 : build with `HAVE_ALPN`; without it, offering protocols fails
711 : the handshake with `std::errc::function_not_supported` rather
712 : than negotiate nothing silently.
713 :
714 : @par Example
715 : @code
716 : // Prefer HTTP/2, fall back to HTTP/1.1
717 : ctx.set_alpn( { "h2", "http/1.1" } );
718 : @endcode
719 : */
720 : std::error_code set_alpn(std::initializer_list<std::string_view> protocols);
721 :
722 : //
723 : // Certificate Verification
724 : //
725 :
726 : /** Set the peer certificate verification mode.
727 :
728 : Controls whether and how peer certificates are verified during
729 : the TLS handshake.
730 :
731 : @param mode The verification mode to use.
732 :
733 : @return Success, or an error if the mode could not be set.
734 :
735 : @par Example
736 : @code
737 : // Verify peer certificate (typical for clients)
738 : ctx.set_verify_mode( tls_verify_mode::peer );
739 :
740 : // Require client certificate (server-side mTLS)
741 : ctx.set_verify_mode( tls_verify_mode::require_peer );
742 : @endcode
743 :
744 : @see tls_verify_mode
745 : */
746 : std::error_code set_verify_mode(tls_verify_mode mode);
747 :
748 : /** Set the maximum certificate chain verification depth.
749 :
750 : Limits how many intermediate certificates can appear between
751 : the peer certificate and a trusted root. The default is
752 : typically 100, which is sufficient for most certificate chains.
753 :
754 : @param depth Maximum number of intermediate certificates allowed.
755 :
756 : @return Success, or an error if the depth is invalid.
757 : */
758 : std::error_code set_verify_depth(int depth);
759 :
760 : /** Set a custom certificate verification callback.
761 :
762 : Installs a callback that is invoked during certificate chain
763 : verification. The callback can perform additional validation
764 : beyond the standard checks and can override verification
765 : results.
766 :
767 : The callback receives the built-in verification result so far and
768 : a verify_context describing the certificate being verified. Return
769 : `true` to accept the certificate, `false` to reject. Inspect the
770 : certificate portably via `verify_context::certificate()` (its DER
771 : encoding) — for example to pin a specific certificate.
772 :
773 : @par Backend Support
774 :
775 : The exact set of certificates the callback sees differs by backend:
776 :
777 : - OpenSSL: the callback runs once per certificate in the chain,
778 : including certificates that passed the built-in checks. It can
779 : therefore both relax verification (return `true` for a
780 : certificate the library rejected) and tighten it (return `false`
781 : for a certificate the library accepted, e.g. pinning).
782 : - WolfSSL built with `WOLFSSL_ALWAYS_VERIFY_CB` (implied by
783 : `--enable-opensslextra`): same as OpenSSL.
784 : - WolfSSL without that option: the library invokes the callback
785 : only on verification *failure*, so it cannot be honored on a
786 : successful handshake. To avoid silently ignoring a
787 : verification-tightening callback (which would fail open), a
788 : context that carries a callback instead **fails the handshake**
789 : with `std::errc::function_not_supported` on such a build. Rebuild
790 : WolfSSL with `WOLFSSL_ALWAYS_VERIFY_CB`, or omit the callback.
791 :
792 : @tparam Callback A callable with signature
793 : `bool( bool preverified, verify_context& ctx )`.
794 :
795 : @param callback The verification callback.
796 :
797 : @return Success. The callback is recorded here and applied during the
798 : handshake. On a WolfSSL build that cannot honor it, the handshake
799 : fails with `std::errc::function_not_supported` (see Backend
800 : Support).
801 :
802 : @par Example
803 : @code
804 : ctx.set_verify_mode( tls_verify_mode::peer );
805 : ctx.set_verify_callback(
806 : []( bool preverified, verify_context& ctx ) -> bool
807 : {
808 : if( ! preverified )
809 : return false;
810 : // Pin: accept only a certificate whose DER matches.
811 : auto der = ctx.certificate();
812 : return der.size() == expected_pin.size() &&
813 : std::equal( der.begin(), der.end(), expected_pin.begin() );
814 : });
815 : @endcode
816 :
817 : @see verify_context
818 : @see set_verify_mode
819 : */
820 : template<typename Callback>
821 : std::error_code set_verify_callback(Callback callback);
822 :
823 : /** Set a callback for Server Name Indication (SNI).
824 :
825 : For server connections, this callback is invoked during the TLS
826 : handshake when a client sends an SNI extension. The callback
827 : receives the requested hostname and can accept or reject the
828 : connection.
829 :
830 : @tparam Callback A callable with signature
831 : `bool( std::string_view hostname )`.
832 :
833 : @param callback The SNI callback. Return `true` to accept the
834 : connection or `false` to reject it with an alert.
835 :
836 : @par Example
837 : @code
838 : // Accept connections for specific domains only
839 : ctx.set_servername_callback(
840 : []( std::string_view hostname ) -> bool
841 : {
842 : return hostname == "api.example.com" ||
843 : hostname == "www.example.com";
844 : });
845 : @endcode
846 :
847 : @note For virtual hosting with different certificates per hostname,
848 : create separate contexts and select the appropriate one before
849 : creating the TLS stream.
850 :
851 : @see tls_stream::set_hostname
852 : */
853 : template<typename Callback>
854 : void set_servername_callback(Callback callback);
855 :
856 : private:
857 : void set_servername_callback_impl(
858 : std::function<bool(std::string_view)> callback);
859 :
860 : void set_password_callback_impl(
861 : std::function<std::string(std::size_t, tls_password_purpose)> callback);
862 :
863 : void set_verify_callback_impl(
864 : std::function<bool(bool, verify_context&)> callback);
865 :
866 : public:
867 : //
868 : // Revocation Checking
869 : //
870 :
871 : /** Add a Certificate Revocation List from memory.
872 :
873 : Adds a CRL to the verification store for checking whether
874 : certificates have been revoked. CRLs are typically fetched
875 : from the URLs in a certificate's CRL Distribution Points
876 : extension.
877 :
878 : @param crl The CRL data in DER or PEM format.
879 :
880 : @return Success, or an error if the CRL could not be parsed.
881 :
882 : @note CRLs are consulted only when a revocation policy is set via
883 : @ref set_revocation_policy. On WolfSSL, CRL checking requires a
884 : build with `HAVE_CRL`; without it, supplying a CRL or a
885 : revocation policy fails the handshake with
886 : `std::errc::function_not_supported`.
887 :
888 : @see add_crl_file
889 : @see set_revocation_policy
890 : */
891 : std::error_code add_crl(std::string_view crl);
892 :
893 : /** Add a Certificate Revocation List from a file.
894 :
895 : Adds a CRL to the verification store for checking whether
896 : certificates have been revoked.
897 :
898 : @param filename Path to a CRL file (DER or PEM format).
899 :
900 : @return Success, or an error if the file could not be read
901 : or the CRL is invalid.
902 :
903 : @note CRLs are consulted only when a revocation policy is set via
904 : @ref set_revocation_policy (WolfSSL requires a `HAVE_CRL`
905 : build).
906 :
907 : @par Example
908 : @code
909 : ctx.add_crl_file( "issuer.crl" );
910 : @endcode
911 :
912 : @see add_crl
913 : @see set_revocation_policy
914 : */
915 : std::error_code add_crl_file(std::string_view filename);
916 :
917 : /** Set the certificate revocation checking policy.
918 :
919 : Controls how certificate revocation status is checked during
920 : verification via CRLs.
921 :
922 : @param policy The revocation checking policy.
923 :
924 : @par Example
925 : @code
926 : // Require successful revocation check
927 : ctx.set_revocation_policy( tls_revocation_policy::hard_fail );
928 :
929 : // Check but allow unknown status
930 : ctx.set_revocation_policy( tls_revocation_policy::soft_fail );
931 : @endcode
932 :
933 : @note Revocation is checked via CRLs supplied with @ref add_crl /
934 : @ref add_crl_file. `soft_fail` accepts a certificate whose
935 : status cannot be determined (missing/expired CRL) but rejects
936 : one that is actually revoked; `hard_fail` also rejects unknown
937 : status. OCSP-based revocation is not available (see the TLS
938 : guide). On WolfSSL a non-disabled policy requires a `HAVE_CRL`
939 : build, else the handshake fails with
940 : `std::errc::function_not_supported`.
941 :
942 : @see tls_revocation_policy
943 : @see add_crl
944 : */
945 : void set_revocation_policy(tls_revocation_policy policy);
946 :
947 : //
948 : // Password Handling
949 : //
950 :
951 : /** Set the password callback for encrypted keys.
952 :
953 : Installs a callback that provides passwords for encrypted
954 : private keys and PKCS#12 files. The callback is invoked when
955 : loading encrypted key material.
956 :
957 : @tparam Callback A callable with signature
958 : `std::string( std::size_t max_length, password_purpose purpose )`.
959 :
960 : @param callback The password callback. It receives the maximum
961 : password length and the purpose (reading or writing), and
962 : returns the password string.
963 :
964 : @par Example
965 : @code
966 : ctx.set_password_callback(
967 : []( std::size_t max_len, tls_password_purpose purpose )
968 : {
969 : // In practice, prompt user or read from secure storage
970 : return std::string( "my-key-password" );
971 : });
972 :
973 : // Now load encrypted key
974 : ctx.use_private_key_file( "encrypted.key", tls_file_format::pem );
975 : @endcode
976 :
977 : @see tls_password_purpose
978 : */
979 : template<typename Callback>
980 : void set_password_callback(Callback callback);
981 : };
982 : #ifdef _MSC_VER
983 : #pragma warning(pop)
984 : #endif
985 :
986 : template<typename Callback>
987 : void
988 1 : tls_context::set_servername_callback(Callback callback)
989 : {
990 1 : set_servername_callback_impl(std::move(callback));
991 1 : }
992 :
993 : template<typename Callback>
994 : void
995 1 : tls_context::set_password_callback(Callback callback)
996 : {
997 1 : set_password_callback_impl(std::move(callback));
998 1 : }
999 :
1000 : template<typename Callback>
1001 : std::error_code
1002 : tls_context::set_verify_callback(Callback callback)
1003 : {
1004 : set_verify_callback_impl(std::move(callback));
1005 : return {};
1006 : }
1007 :
1008 : } // namespace boost::corosio
1009 :
1010 : #endif
|
