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Diffstat (limited to 'openssl-1.1.0h/doc/ssl/SSL_CTX_set_ct_validation_callback.pod')
| -rw-r--r-- | openssl-1.1.0h/doc/ssl/SSL_CTX_set_ct_validation_callback.pod | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/openssl-1.1.0h/doc/ssl/SSL_CTX_set_ct_validation_callback.pod b/openssl-1.1.0h/doc/ssl/SSL_CTX_set_ct_validation_callback.pod new file mode 100644 index 0000000..afa45dc --- /dev/null +++ b/openssl-1.1.0h/doc/ssl/SSL_CTX_set_ct_validation_callback.pod @@ -0,0 +1,145 @@ +=pod + +=head1 NAME + +ssl_ct_validation_cb, +SSL_enable_ct, SSL_CTX_enable_ct, SSL_disable_ct, SSL_CTX_disable_ct, +SSL_set_ct_validation_callback, SSL_CTX_set_ct_validation_callback, +SSL_ct_is_enabled, SSL_CTX_ct_is_enabled - +control Certificate Transparency policy + +=head1 SYNOPSIS + + #include <openssl/ssl.h> + + typedef int (*ssl_ct_validation_cb)(const CT_POLICY_EVAL_CTX *ctx, + const STACK_OF(SCT) *scts, void *arg); + + int SSL_enable_ct(SSL *s, int validation_mode); + int SSL_CTX_enable_ct(SSL_CTX *ctx, int validation_mode); + int SSL_set_ct_validation_callback(SSL *s, ssl_ct_validation_cb callback, + void *arg); + int SSL_CTX_set_ct_validation_callback(SSL_CTX *ctx, + ssl_ct_validation_cb callback, + void *arg); + void SSL_disable_ct(SSL *s); + void SSL_CTX_disable_ct(SSL_CTX *ctx); + int SSL_ct_is_enabled(const SSL *s); + int SSL_CTX_ct_is_enabled(const SSL_CTX *ctx); + +=head1 DESCRIPTION + +SSL_enable_ct() and SSL_CTX_enable_ct() enable the processing of signed +certificate timestamps (SCTs) either for a given SSL connection or for all +connections that share the given SSL context, respectively. +This is accomplished by setting a built-in CT validation callback. +The behaviour of the callback is determined by the B<validation_mode> argument, +which can be either of B<SSL_CT_VALIDATION_PERMISSIVE> or +B<SSL_CT_VALIDATION_STRICT> as described below. + +If B<validation_mode> is equal to B<SSL_CT_VALIDATION_STRICT>, then in a full +TLS handshake with the verification mode set to B<SSL_VERIFY_PEER>, if the peer +presents no valid SCTs the handshake will be aborted. +If the verification mode is B<SSL_VERIFY_NONE>, the handshake will continue +despite lack of valid SCTs. +However, in that case if the verification status before the built-in callback +was B<X509_V_OK> it will be set to B<X509_V_ERR_NO_VALID_SCTS> after the +callback. +Applications can call L<SSL_get_verify_result(3)> to check the status at +handshake completion, even after session resumption since the verification +status is part of the saved session state. +See L<SSL_set_verify(3)>, <SSL_get_verify_result(3)>, L<SSL_session_reused(3)>. + +If B<validation_mode> is equal to B<SSL_CT_VALIDATION_PERMISSIVE>, then the +handshake continues, and the verification status is not modified, regardless of +the validation status of any SCTs. +The application can still inspect the validation status of the SCTs at +handshake completion. +Note that with session resumption there will not be any SCTs presented during +the handshake. +Therefore, in applications that delay SCT policy enforcement until after +handshake completion, such delayed SCT checks should only be performed when the +session is not resumed. + +SSL_set_ct_validation_callback() and SSL_CTX_set_ct_validation_callback() +register a custom callback that may implement a different policy than either of +the above. +This callback can examine the peer's SCTs and determine whether they are +sufficient to allow the connection to continue. +The TLS handshake is aborted if the verification mode is not B<SSL_VERIFY_NONE> +and the callback returns a non-positive result. + +An arbitrary callback context argument, B<arg>, can be passed in when setting +the callback. +This will be passed to the callback whenever it is invoked. +Ownership of this context remains with the caller. + +If no callback is set, SCTs will not be requested and Certificate Transparency +validation will not occur. + +No callback will be invoked when the peer presents no certificate, e.g. by +employing an anonymous (aNULL) ciphersuite. +In that case the handshake continues as it would had no callback been +requested. +Callbacks are also not invoked when the peer certificate chain is invalid or +validated via DANE-TA(2) or DANE-EE(3) TLSA records which use a private X.509 +PKI, or no X.509 PKI at all, respectively. +Clients that require SCTs are expected to not have enabled any aNULL ciphers +nor to have specified server verification via DANE-TA(2) or DANE-EE(3) TLSA +records. + +SSL_disable_ct() and SSL_CTX_disable_ct() turn off CT processing, whether +enabled via the built-in or the custom callbacks, by setting a NULL callback. +These may be implemented as macros. + +SSL_ct_is_enabled() and SSL_CTX_ct_is_enabled() return 1 if CT processing is +enabled via either SSL_enable_ct() or a non-null custom callback, and 0 +otherwise. + +=head1 NOTES + +When SCT processing is enabled, OCSP stapling will be enabled. This is because +one possible source of SCTs is the OCSP response from a server. + +The time returned by SSL_SESSION_get_time() will be used to evaluate whether any +presented SCTs have timestamps that are in the future (and therefore invalid). + +=head1 RESTRICTIONS + +Certificate Transparency validation cannot be enabled and so a callback cannot +be set if a custom client extension handler has been registered to handle SCT +extensions (B<TLSEXT_TYPE_signed_certificate_timestamp>). + +=head1 RETURN VALUES + +SSL_enable_ct(), SSL_CTX_enable_ct(), SSL_CTX_set_ct_validation_callback() and +SSL_set_ct_validation_callback() return 1 if the B<callback> is successfully +set. +They return 0 if an error occurs, e.g. a custom client extension handler has +been setup to handle SCTs. + +SSL_disable_ct() and SSL_CTX_disable_ct() do not return a result. + +SSL_CTX_ct_is_enabled() and SSL_ct_is_enabled() return a 1 if a non-null CT +validation callback is set, or 0 if no callback (or equivalently a NULL +callback) is set. + +=head1 SEE ALSO + +L<ssl(7)>, +<SSL_get_verify_result(3)>, +L<SSL_session_reused(3)>, +L<SSL_set_verify(3)>, +L<SSL_CTX_set_verify(3)>, +L<SSL_SESSION_get_time(3)> + +=head1 COPYRIGHT + +Copyright 2016-2017 The OpenSSL Project Authors. All Rights Reserved. + +Licensed under the OpenSSL license (the "License"). You may not use +this file except in compliance with the License. You can obtain a copy +in the file LICENSE in the source distribution or at +L<https://www.openssl.org/source/license.html>. + +=cut |