NAME

       SSL_CTX_set_stateless_cookie_generate_cb, SSL_CTX_set_stateless_cookie_verify_cb -
       Callback functions for stateless TLS1.3 cookies

SYNOPSIS

        #include <openssl/ssl.h>

        void SSL_CTX_set_stateless_cookie_generate_cb(
            SSL_CTX *ctx,
            int (*gen_stateless_cookie_cb) (SSL *ssl,
                                            unsigned char *cookie,
                                            size_t *cookie_len));
        void SSL_CTX_set_stateless_cookie_verify_cb(
            SSL_CTX *ctx,
            int (*verify_stateless_cookie_cb) (SSL *ssl,
                                               const unsigned char *cookie,
                                               size_t cookie_len));

DESCRIPTION

       SSL_CTX_set_cookie_generate_cb() sets the callback used by SSL_stateless(3) to generate
       the application-controlled portion of the cookie provided to clients in the
       HelloRetryRequest transmitted as a response to a ClientHello with a missing or invalid
       cookie. gen_stateless_cookie_cb() must write at most SSL_COOKIE_LENGTH bytes into cookie,
       and must write the number of bytes written to cookie_len. If a cookie cannot be generated,
       a zero return value can be used to abort the handshake.

       SSL_CTX_set_cookie_verify_cb() sets the callback used by SSL_stateless(3) to determine
       whether the application-controlled portion of a ClientHello cookie is valid. A nonzero
       return value from app_verify_cookie_cb() communicates that the cookie is valid. The
       integrity of the entire cookie, including the application-controlled portion, is
       automatically verified by HMAC before verify_stateless_cookie_cb() is called.

RETURN VALUES

       Neither function returns a value.

SEE ALSO

       SSL_stateless(3)

COPYRIGHT

       Copyright 2018 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 <https://www.openssl.org/source/license.html>.

1.1.1                                       2023-05SSL_CTX_SET_STATELESS_COOKIE_GENERATE_CB(3SSL)