NAME

       SSL_CTX_set_stateless_cookie_generate_cb, SSL_CTX_set_stateless_cookie_verify_cb,
       SSL_CTX_set_cookie_generate_cb, SSL_CTX_set_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));

        void SSL_CTX_set_cookie_generate_cb(SSL_CTX *ctx,
                                            int (*app_gen_cookie_cb) (SSL *ssl,
                                                                      unsigned char
                                                                      *cookie,
                                                                      unsigned int
                                                                      *cookie_len));
        void SSL_CTX_set_cookie_verify_cb(SSL_CTX *ctx,
                                          int (*app_verify_cookie_cb) (SSL *ssl,
                                                                       const unsigned
                                                                       char *cookie,
                                                                       unsigned int
                                                                       cookie_len));

DESCRIPTION

       SSL_CTX_set_stateless_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_stateless_cookie_verify_cb() sets the callback used by SSL_stateless(3) to
       determine whether the application-controlled portion of a ClientHello cookie is valid. The
       cookie data is pointed to by cookie and is of length cookie_len. A nonzero return value
       from verify_stateless_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.

       SSL_CTX_set_cookie_generate_cb() sets the callback used by DTLSv1_listen(3) to generate
       the cookie provided to clients in the HelloVerifyRequest transmitted as a response to a
       ClientHello with a missing or invalid cookie.  app_gen_cookie_cb()  must write at most
       DTLS1_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 DTLSv1_listen(3) to determine
       whether the cookie in a ClientHello is valid. The cookie data is pointed to by cookie and
       is of length cookie_len. A nonzero return value from app_verify_cookie_cb() communicates
       that the cookie is valid. The integrity of the cookie is not verified by OpenSSL. This is
       an application responsibility.

RETURN VALUES

       Neither function returns a value.

SEE ALSO

       ssl(7), SSL_stateless(3), DTLSv1_listen(3)

HISTORY

       SSL_CTX_set_stateless_cookie_generate_cb() and SSL_CTX_set_stateless_cookie_verify_cb()
       were added in OpenSSL 1.1.1.

COPYRIGHT

       Copyright 2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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>.

3.0.5                                       2022-08SSL_CTX_SET_STATELESS_COOKIE_GENERATE_CB(3SSL)