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 : /** Exposes the certificate and error state to a verification callback.
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)
157 : , der_(der)
158 : , der_len_(der_len)
159 : {
160 : }
161 :
162 : /** Return the native verification handle.
163 :
164 : Cast the result to the backend's verification context type
165 : (e.g. `X509_STORE_CTX*`) to inspect the certificate chain using
166 : backend-specific APIs.
167 :
168 : @return The native handle, or `nullptr` if none is available.
169 : */
170 : void* native_handle() const noexcept
171 : {
172 : return handle_;
173 : }
174 :
175 : /** Return the DER encoding of the certificate being verified.
176 :
177 : This is the portable way to inspect the peer certificate from a
178 : verification callback. It works identically on every backend,
179 : without depending on backend-specific build options. A DER
180 : certificate is an ASN.1 `SEQUENCE`, so the first byte is `0x30`.
181 :
182 : @return A view of the certificate's DER bytes, valid only for the
183 : duration of the callback. Empty if the certificate is not
184 : available.
185 : */
186 MIS 0 : std::span<unsigned char const> certificate() const noexcept
187 : {
188 0 : return {der_, der_len_};
189 : }
190 : };
191 :
192 : namespace detail {
193 : struct tls_context_data;
194 : tls_context_data const& get_tls_context_data(tls_context const&) noexcept;
195 : } // namespace detail
196 :
197 : #ifdef _MSC_VER
198 : #pragma warning(push)
199 : #pragma warning(disable : 4251) // shared_ptr needs dll-interface
200 : #endif
201 :
202 : /** Configures the certificates, keys, and protocol settings a TLS stream uses.
203 :
204 : The `tls_context` class provides a backend-agnostic interface for
205 : configuring TLS connections. It stores credentials (certificates and
206 : private keys), trust anchors, protocol settings, and verification
207 : options that are used when establishing TLS connections.
208 :
209 : This class is a shared handle to an opaque implementation. Copies
210 : share the same underlying state. This allows contexts to be passed
211 : by value and shared across multiple TLS streams.
212 :
213 : This class abstracts the configuration phase of TLS across multiple
214 : backend implementations, among them OpenSSL, WolfSSL, mbedTLS and
215 : Schannel. Portable code therefore works regardless of which TLS
216 : library is linked.
217 :
218 : @par Modification After Stream Creation
219 :
220 : Modifying a context after creating a TLS stream from it
221 : results in undefined behavior. The context's configuration is
222 : captured when the first stream is constructed, and subsequent
223 : modifications are not reflected in existing or new streams
224 : sharing the context.
225 :
226 : If different configurations are needed, create separate context
227 : objects.
228 :
229 : @par Thread Safety
230 :
231 : Distinct objects: Safe.
232 :
233 : Shared objects: Unsafe. A context must not be modified while
234 : any thread is creating streams from it.
235 :
236 : @par Example
237 : @par !example tls_context
238 :
239 : @see tls_role
240 : */
241 : class BOOST_COROSIO_DECL tls_context
242 : {
243 : struct implementation;
244 : std::shared_ptr<implementation> impl_;
245 :
246 : friend detail::tls_context_data const&
247 : detail::get_tls_context_data(tls_context const&) noexcept;
248 :
249 : public:
250 : /** Construct a default TLS context.
251 :
252 : Creates a context with default settings suitable for TLS 1.2
253 : and TLS 1.3 connections. No certificates or trust anchors are
254 : loaded; call the appropriate methods to configure credentials
255 : and verification.
256 :
257 : @par Example
258 : @par !example tls_context
259 : */
260 : tls_context();
261 :
262 : /** Creates a new handle that shares ownership of the underlying
263 : TLS context state with `other`.
264 :
265 : @param other The context to copy from.
266 : */
267 HIT 2 : tls_context(tls_context const& other) = default;
268 :
269 : /** Releases the current context's shared ownership and acquires
270 : shared ownership of `other`'s underlying state.
271 :
272 : @param other The context to copy from.
273 :
274 : @return Reference to this context.
275 : */
276 1 : tls_context& operator=(tls_context const& other) = default;
277 :
278 : /** Transfers ownership of the TLS context from another instance.
279 : After the move, `other` is in a valid but empty state.
280 :
281 : @param other The context to move from.
282 : */
283 2 : tls_context(tls_context&& other) noexcept = default;
284 :
285 : /** Releases the current context's shared ownership and transfers
286 : ownership from another instance. After the move, `other` is
287 : in a valid but empty state.
288 :
289 : @param other The context to move from.
290 :
291 : @return Reference to this context.
292 : */
293 1 : tls_context& operator=(tls_context&& other) noexcept = default;
294 :
295 : /** Releases this handle's shared ownership of the underlying
296 : context. The context state is destroyed when the last handle
297 : is released.
298 : */
299 55 : ~tls_context() = default;
300 :
301 : //
302 : // Credential Loading
303 : //
304 :
305 : /** Load the entity certificate from a memory buffer.
306 :
307 : Sets the certificate that identifies this endpoint to the peer.
308 : For servers, this is the server certificate. For clients using
309 : mutual TLS, this is the client certificate.
310 :
311 : The certificate must match the private key loaded via
312 : `use_private_key()` or `use_private_key_file()`.
313 :
314 : @param certificate The certificate data.
315 :
316 : @param format The encoding format of the certificate data.
317 :
318 : @return Success. The certificate is recorded and decoded when the
319 : native context is first built; a malformed certificate surfaces
320 : as a handshake failure.
321 :
322 : @see use_certificate_file
323 : @see use_private_key
324 : */
325 : [[nodiscard]] std::error_code
326 : use_certificate(std::string_view certificate, tls_file_format format);
327 :
328 : /** Load the entity certificate from a file.
329 :
330 : Sets the certificate that identifies this endpoint to the peer.
331 : For servers, this is the server certificate. For clients using
332 : mutual TLS, this is the client certificate.
333 :
334 : @param filename Path to the certificate file.
335 :
336 : @param format The encoding format of the file.
337 :
338 : @return Success, or an error if the file could not be read. The
339 : certificate is decoded when the native context is first built;
340 : a malformed certificate surfaces as a handshake failure.
341 :
342 : @par Example
343 : @par !example use_certificate_file
344 :
345 : @see use_certificate
346 : @see use_private_key_file
347 : */
348 : [[nodiscard]] std::error_code
349 : use_certificate_file(std::string_view filename, tls_file_format format);
350 :
351 : /** Load a certificate chain from a memory buffer.
352 :
353 : Loads the entity certificate followed by intermediate CA certificates.
354 : The chain should be ordered from leaf to root (excluding the root).
355 : This is the typical format for PEM certificate bundles.
356 :
357 : @param chain The certificate chain data in PEM format (concatenated
358 : certificates).
359 :
360 : @return Success. The chain is recorded and decoded when the native
361 : context is first built; a malformed chain surfaces as a
362 : handshake failure.
363 :
364 : @see use_certificate_chain_file
365 : */
366 : [[nodiscard]] std::error_code use_certificate_chain(std::string_view chain);
367 :
368 : /** Load a certificate chain from a file.
369 :
370 : Loads the entity certificate followed by intermediate CA certificates
371 : from a PEM file. The file should contain concatenated PEM certificates
372 : ordered from leaf to root (excluding the root).
373 :
374 : @param filename Path to the certificate chain file.
375 :
376 : @return Success, or an error if the file could not be read. The
377 : chain is decoded when the native context is first built; a
378 : malformed chain surfaces as a handshake failure.
379 :
380 : @par Example
381 : @par !example use_certificate_chain_file
382 :
383 : @see use_certificate_chain
384 : */
385 : [[nodiscard]] std::error_code
386 : use_certificate_chain_file(std::string_view filename);
387 :
388 : /** Load the private key from a memory buffer.
389 :
390 : Sets the private key corresponding to the entity certificate.
391 : The key must match the certificate loaded via `use_certificate()`
392 : or `use_certificate_chain()`.
393 :
394 : If the key is encrypted, set a password callback via
395 : `set_password_callback()` before calling this function.
396 :
397 : @param private_key The private key data.
398 :
399 : @param format The encoding format of the key data.
400 :
401 : @return Success. The key is recorded and decoded when the native
402 : context is first built. Three faults surface only as a handshake
403 : failure: a malformed key, a missing password callback for an
404 : encrypted key, and a certificate mismatch.
405 :
406 : @see use_private_key_file
407 : @see set_password_callback
408 : */
409 : [[nodiscard]] std::error_code
410 : use_private_key(std::string_view private_key, tls_file_format format);
411 :
412 : /** Load the private key from a file.
413 :
414 : Sets the private key corresponding to the entity certificate.
415 : The key must match the certificate loaded via `use_certificate_file()`
416 : or `use_certificate_chain_file()`.
417 :
418 : If the key file is encrypted, set a password callback via
419 : `set_password_callback()` before calling this function.
420 :
421 : @param filename Path to the private key file.
422 :
423 : @param format The encoding format of the file.
424 :
425 : @return Success, or an error if the file could not be read. The
426 : key is decoded when the native context is first built; a
427 : malformed key or a certificate mismatch surfaces as a
428 : handshake failure.
429 :
430 : @par Example
431 : @par !example use_private_key_file
432 :
433 : @see use_private_key
434 : @see set_password_callback
435 : */
436 : [[nodiscard]] std::error_code
437 : use_private_key_file(std::string_view filename, tls_file_format format);
438 :
439 : /** Load credentials from a PKCS#12 bundle in memory.
440 :
441 : PKCS#12 (also known as PFX) is a binary format that bundles a
442 : certificate, private key, and optionally intermediate certificates
443 : into a single password-protected file.
444 :
445 : @param data The PKCS#12 bundle data.
446 :
447 : @param passphrase The password protecting the bundle.
448 :
449 : @return Success. The bundle is recorded and decoded into the
450 : certificate, private key, and chain when the native context is
451 : first built. A malformed bundle or a wrong passphrase surfaces as a
452 : handshake failure.
453 :
454 : @note Intermediate certificates inside the bundle are loaded and
455 : sent during the handshake on both backends.
456 :
457 : @see use_pkcs12_file
458 : */
459 : [[nodiscard]] std::error_code
460 : use_pkcs12(std::string_view data, std::string_view passphrase);
461 :
462 : /** Load credentials from a PKCS#12 file.
463 :
464 : PKCS#12 (also known as PFX) is a binary format that bundles a
465 : certificate, private key, and optionally intermediate certificates
466 : into a single password-protected file. This is common on Windows
467 : and for certificates exported from browsers.
468 :
469 : @param filename Path to the PKCS#12 file.
470 :
471 : @param passphrase The password protecting the file.
472 :
473 : @return Success, or an error if the file could not be read. The
474 : bundle is decoded when the native context is first built; a
475 : malformed bundle or wrong passphrase surfaces as a handshake
476 : failure.
477 :
478 : @note Intermediate certificates inside the bundle are loaded and
479 : sent during the handshake on both backends.
480 :
481 : @par Example
482 : @par !example use_pkcs12_file
483 :
484 : @see use_pkcs12
485 : */
486 : [[nodiscard]] std::error_code
487 : use_pkcs12_file(std::string_view filename, std::string_view passphrase);
488 :
489 : //
490 : // Trust Anchors
491 : //
492 :
493 : /** Add a certificate authority for peer verification.
494 :
495 : Adds a single CA certificate to the trust store used for verifying
496 : peer certificates. Call this multiple times to add multiple CAs,
497 : or use `load_verify_file()` for a bundle.
498 :
499 : @param ca The CA certificate data in PEM format.
500 :
501 : @return Success. The certificate is recorded and decoded when the
502 : native context is first built; a malformed certificate
503 : surfaces as a handshake failure.
504 :
505 : @see load_verify_file
506 : @see set_default_verify_paths
507 : */
508 : [[nodiscard]] std::error_code
509 : add_certificate_authority(std::string_view ca);
510 :
511 : /** Load CA certificates from a file.
512 :
513 : Loads one or more CA certificates from a PEM file. The file may
514 : contain multiple concatenated PEM certificates.
515 :
516 : @param filename Path to a PEM file containing CA certificates.
517 :
518 : @return Success, or an error if the file could not be read. The
519 : certificates are decoded when the native context is first
520 : built; malformed certificates surface as a handshake failure.
521 :
522 : @par Example
523 : @par !example load_verify_file
524 :
525 : @see add_certificate_authority
526 : @see add_verify_path
527 : */
528 : [[nodiscard]] std::error_code load_verify_file(std::string_view filename);
529 :
530 : /** Add a directory of CA certificates for verification.
531 :
532 : Adds a directory of CA certificates to the trust store. The
533 : directory is applied when the native context is first built from
534 : this context.
535 :
536 : The expected directory layout depends on the backend. OpenSSL
537 : performs on-demand lookups. Each certificate file must be named
538 : by its subject-name hash, as generated by `openssl rehash` or
539 : `c_rehash`. WolfSSL loads every certificate file in the
540 : directory.
541 :
542 : @param path Path to the directory of CA certificates.
543 :
544 : @return Success. The path is recorded and applied when the native
545 : context is built. A directory that cannot be read at that time is
546 : skipped rather than reported here.
547 :
548 : @par Example
549 : @par !example add_verify_path
550 :
551 : @see load_verify_file
552 : @see set_default_verify_paths
553 : */
554 : [[nodiscard]] std::error_code add_verify_path(std::string_view path);
555 :
556 : /** Use the system default CA certificate store.
557 :
558 : Configures the context to use the operating system's default
559 : trust store for peer certificate verification. This is the
560 : recommended approach for HTTPS clients connecting to public
561 : servers.
562 :
563 : The system store is loaded when the native context is first built
564 : from this context. For a verified-safe client, combine this with
565 : `set_verify_mode( tls_verify_mode::peer )` and, when connecting by
566 : name, `tls_stream::set_hostname()`.
567 :
568 : @return Success. The request is recorded and applied when the
569 : native context is built. A system store that cannot be loaded at
570 : that time is skipped rather than reported here. A context that
571 : must reject unverified peers should therefore also use
572 : `set_verify_mode( tls_verify_mode::peer )`.
573 :
574 : @note The OpenSSL backend honors the `SSL_CERT_FILE` and
575 : `SSL_CERT_DIR` environment variables. The WolfSSL backend
576 : requires a build with `WOLFSSL_SYS_CA_CERTS`; without it the
577 : system store is unavailable and this call has no effect.
578 :
579 : @par Example
580 : @par !example set_default_verify_paths
581 :
582 : @see load_verify_file
583 : @see add_verify_path
584 : @see set_verify_mode
585 : */
586 : [[nodiscard]] std::error_code set_default_verify_paths();
587 :
588 : //
589 : // Protocol Configuration
590 : //
591 :
592 : /** Set the minimum TLS protocol version.
593 :
594 : Connections reject protocol versions older than this.
595 : The default allows TLS 1.2 and newer.
596 :
597 : @param v The minimum protocol version to accept.
598 :
599 : @return Success. The version is recorded and applied when the
600 : native context is first built.
601 :
602 : @par Example
603 : @par !example set_min_protocol_version
604 :
605 : @see set_max_protocol_version
606 : */
607 : [[nodiscard]] std::error_code set_min_protocol_version(tls_version v);
608 :
609 : /** Set the maximum TLS protocol version.
610 :
611 : Connections do not negotiate protocol versions newer than this.
612 : The default allows the newest supported version.
613 :
614 : @param v The maximum protocol version to accept.
615 :
616 : @return Success. The version is recorded and applied when the
617 : native context is first built.
618 :
619 : @note On WolfSSL the ceiling is applied by selecting a
620 : version-specific method, because no native set-max API exists. An
621 : invalid window, where the minimum exceeds the maximum, yields a
622 : context that fails the handshake.
623 :
624 : @see set_min_protocol_version
625 : */
626 : [[nodiscard]] std::error_code set_max_protocol_version(tls_version v);
627 :
628 : /** Set the allowed cipher suites.
629 :
630 : Configures which cipher suites may be used for connections.
631 : The format is backend-specific but typically follows OpenSSL
632 : cipher list syntax.
633 :
634 : @param ciphers The cipher suite specification string.
635 :
636 : @return Success. The string is recorded and applied when the
637 : native context is first built; an invalid cipher string
638 : surfaces as a handshake failure.
639 :
640 : @par Example
641 : @par !example set_ciphersuites
642 :
643 : @note This configures cipher suites for TLS 1.2 and below. For
644 : TLS 1.3, use @ref set_ciphersuites_tls13.
645 : */
646 : [[nodiscard]] std::error_code set_ciphersuites(std::string_view ciphers);
647 :
648 : /** Set the allowed TLS 1.3 cipher suites.
649 :
650 : TLS 1.3 uses a distinct, fixed set of cipher suites configured
651 : separately from earlier versions. The format is a colon-separated
652 : list of TLS 1.3 suite names.
653 :
654 : @param ciphers The TLS 1.3 cipher suite list.
655 :
656 : @return Success. The string is recorded and applied when the
657 : native context is first built; an invalid cipher string
658 : surfaces as a handshake failure.
659 :
660 : @par Example
661 : @par !example set_ciphersuites_tls13
662 :
663 : @note On the WolfSSL backend, TLS 1.2 and TLS 1.3 suites share a
664 : single cipher list; this call and @ref set_ciphersuites are
665 : merged into one list.
666 :
667 : @see set_ciphersuites
668 : */
669 : [[nodiscard]] std::error_code
670 : set_ciphersuites_tls13(std::string_view ciphers);
671 :
672 : /** Set the ALPN protocol list.
673 :
674 : Configures Application-Layer Protocol Negotiation (ALPN) for
675 : the connection. ALPN is used to negotiate which application
676 : protocol to use over the TLS connection (e.g., "h2" for HTTP/2,
677 : "http/1.1" for HTTP/1.1).
678 :
679 : The protocols are tried in preference order (first = highest).
680 :
681 : @param protocols Ordered list of protocol identifiers.
682 :
683 : @return Success, or an error if ALPN configuration fails.
684 :
685 : @note Read the negotiated protocol after the handshake via
686 : @ref tls_stream::alpn_protocol. On WolfSSL, ALPN requires a
687 : build with `HAVE_ALPN`; without it, offering protocols fails
688 : the handshake with `std::errc::function_not_supported` rather
689 : than negotiate nothing silently.
690 :
691 : @par Example
692 : @par !example set_alpn
693 : */
694 : [[nodiscard]] std::error_code
695 : set_alpn(std::initializer_list<std::string_view> protocols);
696 :
697 : //
698 : // Certificate Verification
699 : //
700 :
701 : /** Set the peer certificate verification mode.
702 :
703 : Controls whether and how peer certificates are verified during
704 : the TLS handshake.
705 :
706 : @param mode The verification mode to use.
707 :
708 : @return Success. The mode is recorded and applied when the native
709 : context is first built.
710 :
711 : @par Example
712 : @par !example set_verify_mode
713 :
714 : @see tls_verify_mode
715 : */
716 : [[nodiscard]] std::error_code set_verify_mode(tls_verify_mode mode);
717 :
718 : /** Set the maximum certificate chain verification depth.
719 :
720 : Limits how many intermediate certificates can appear between
721 : the peer certificate and a trusted root. The default is
722 : typically 100, which is sufficient for most certificate chains.
723 :
724 : @param depth Maximum number of intermediate certificates allowed.
725 :
726 : @return Success. The depth is recorded and applied when the native
727 : context is first built.
728 :
729 : @par Example
730 : @par !example set_verify_depth
731 : */
732 : [[nodiscard]] std::error_code set_verify_depth(int depth);
733 :
734 : /** Set a custom certificate verification callback.
735 :
736 : Installs a callback that is invoked during certificate chain
737 : verification. The callback can perform additional validation
738 : beyond the standard checks and can override verification
739 : results.
740 :
741 : The callback receives the built-in verification result so far and
742 : a `verify_context` describing the certificate being verified. Return
743 : `true` to accept the certificate, `false` to reject. Inspect the
744 : certificate portably via `verify_context::certificate()` (its DER
745 : encoding) — for example to pin a specific certificate.
746 :
747 : @par Backend Support
748 :
749 : The exact set of certificates the callback sees differs by backend:
750 :
751 : - OpenSSL: the callback runs once per certificate in the chain,
752 : including certificates that passed the built-in checks. It can
753 : therefore relax verification by returning `true` for a
754 : certificate the library rejected. It can also tighten
755 : verification by returning `false` for a certificate the library
756 : accepted, as pinning does.
757 : - WolfSSL built with `WOLFSSL_ALWAYS_VERIFY_CB` (implied by
758 : `--enable-opensslextra`): same as OpenSSL.
759 : - WolfSSL without that option: the library invokes the callback
760 : only on verification *failure*, so it cannot be honored on a
761 : successful handshake. Silently ignoring a verification-tightening
762 : callback would fail open. On such a build, a context that carries
763 : a callback instead **fails the handshake** with
764 : `std::errc::function_not_supported`. Rebuild
765 : WolfSSL with `WOLFSSL_ALWAYS_VERIFY_CB`, or omit the callback.
766 :
767 : @tparam Callback A callable with signature
768 : `bool( bool preverified, verify_context& ctx )`.
769 :
770 : @param callback The verification callback. Recorded here and
771 : applied during the handshake; on a WolfSSL build that
772 : cannot honor it, the handshake fails with
773 : `std::errc::function_not_supported` (see Backend Support).
774 :
775 : @par Example
776 : @par !example set_verify_callback
777 :
778 : @see verify_context
779 : @see set_verify_mode
780 : */
781 : template<typename Callback>
782 : void set_verify_callback(Callback callback);
783 :
784 : /** Set a callback for Server Name Indication (SNI).
785 :
786 : For server connections, this callback is invoked during the TLS
787 : handshake when a client sends an SNI extension. The callback
788 : receives the requested hostname and can accept or reject the
789 : connection.
790 :
791 : @tparam Callback A callable with signature
792 : `bool( std::string_view hostname )`.
793 :
794 : @param callback The SNI callback. Return `true` to accept the
795 : connection or `false` to reject it with an alert.
796 :
797 : @par Example
798 : @par !example set_servername_callback
799 :
800 : @note For virtual hosting with different certificates per hostname,
801 : create separate contexts and select the appropriate one before
802 : creating the TLS stream.
803 :
804 : @see tls_stream::set_hostname
805 : */
806 : template<typename Callback>
807 : void set_servername_callback(Callback callback);
808 :
809 : private:
810 : void set_servername_callback_impl(
811 : std::function<bool(std::string_view)> callback);
812 :
813 : void set_password_callback_impl(
814 : std::function<std::string(std::size_t, tls_password_purpose)> callback);
815 :
816 : void set_verify_callback_impl(
817 : std::function<bool(bool, verify_context&)> callback);
818 :
819 : public:
820 : //
821 : // Revocation Checking
822 : //
823 :
824 : /** Add a Certificate Revocation List from memory.
825 :
826 : Adds a CRL to the verification store for checking whether
827 : certificates are revoked. CRLs are typically fetched
828 : from the URLs in a certificate's CRL Distribution Points
829 : extension.
830 :
831 : @param crl The CRL data in DER or PEM format.
832 :
833 : @return Success. The CRL is recorded and decoded when the native
834 : context is first built; a malformed CRL surfaces as a
835 : handshake failure.
836 :
837 : @note CRLs are consulted only when a revocation policy is set via
838 : @ref set_revocation_policy. On WolfSSL, CRL checking requires a
839 : build with `HAVE_CRL`; without it, supplying a CRL or a
840 : revocation policy fails the handshake with
841 : `std::errc::function_not_supported`.
842 :
843 : @see add_crl_file
844 : @see set_revocation_policy
845 : */
846 : [[nodiscard]] std::error_code add_crl(std::string_view crl);
847 :
848 : /** Add a Certificate Revocation List from a file.
849 :
850 : Adds a CRL to the verification store for checking whether
851 : certificates are revoked.
852 :
853 : @param filename Path to a CRL file (DER or PEM format).
854 :
855 : @return Success, or an error if the file could not be read. The
856 : CRL is decoded when the native context is first built; a
857 : malformed CRL surfaces as a handshake failure.
858 :
859 : @note CRLs are consulted only when a revocation policy is set via
860 : @ref set_revocation_policy (WolfSSL requires a `HAVE_CRL`
861 : build).
862 :
863 : @par Example
864 : @par !example add_crl_file
865 :
866 : @see add_crl
867 : @see set_revocation_policy
868 : */
869 : [[nodiscard]] std::error_code add_crl_file(std::string_view filename);
870 :
871 : /** Set the certificate revocation checking policy.
872 :
873 : Controls how certificate revocation status is checked during
874 : verification via CRLs.
875 :
876 : @param policy The revocation checking policy.
877 :
878 : @par Example
879 : @par !example set_revocation_policy
880 :
881 : @note Revocation is checked via CRLs supplied with @ref add_crl /
882 : @ref add_crl_file. `soft_fail` accepts a certificate whose
883 : status cannot be determined (missing/expired CRL) but rejects
884 : one that is actually revoked; `hard_fail` also rejects unknown
885 : status. OCSP-based revocation is not available (see the TLS
886 : guide). On WolfSSL a non-disabled policy requires a `HAVE_CRL`
887 : build, else the handshake fails with
888 : `std::errc::function_not_supported`.
889 :
890 : @see tls_revocation_policy
891 : @see add_crl
892 : */
893 : void set_revocation_policy(tls_revocation_policy policy);
894 :
895 : //
896 : // Password Handling
897 : //
898 :
899 : /** Set the password callback for encrypted keys.
900 :
901 : Installs a callback that provides passwords for encrypted
902 : private keys and PKCS#12 files. The callback is invoked when
903 : loading encrypted key material.
904 :
905 : @tparam Callback A callable with signature
906 : `std::string( std::size_t max_length, tls_password_purpose purpose )`.
907 :
908 : @param callback The password callback. It receives the maximum
909 : password length and the purpose (reading or writing), and
910 : returns the password string.
911 :
912 : @par Example
913 : @par !example set_password_callback
914 :
915 : @see tls_password_purpose
916 : */
917 : template<typename Callback>
918 : void set_password_callback(Callback callback);
919 : };
920 : #ifdef _MSC_VER
921 : #pragma warning(pop)
922 : #endif
923 :
924 : template<typename Callback>
925 : void
926 1 : tls_context::set_servername_callback(Callback callback)
927 : {
928 1 : set_servername_callback_impl(std::move(callback));
929 1 : }
930 :
931 : template<typename Callback>
932 : void
933 4 : tls_context::set_password_callback(Callback callback)
934 : {
935 4 : set_password_callback_impl(std::move(callback));
936 4 : }
937 :
938 : template<typename Callback>
939 : void
940 2 : tls_context::set_verify_callback(Callback callback)
941 : {
942 2 : set_verify_callback_impl(std::move(callback));
943 2 : }
944 :
945 : } // namespace boost::corosio
946 :
947 : #endif
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