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SSL_CTX_set_security_level(3)       OpenSSL      SSL_CTX_set_security_level(3)

       SSL_CTX_set_security_level, SSL_set_security_level,
       SSL_CTX_get_security_level, SSL_get_security_level,
       SSL_CTX_set_security_callback, SSL_set_security_callback,
       SSL_CTX_get_security_callback, SSL_get_security_callback,
       SSL_CTX_set0_security_ex_data, SSL_set0_security_ex_data,
       SSL_CTX_get0_security_ex_data, SSL_get0_security_ex_data - SSL/TLS
       security framework

       libcrypto, -lcrypto

        #include <openssl/ssl.h>

        void SSL_CTX_set_security_level(SSL_CTX *ctx, int level);
        void SSL_set_security_level(SSL *s, int level);

        int SSL_CTX_get_security_level(const SSL_CTX *ctx);
        int SSL_get_security_level(const SSL *s);

        void SSL_CTX_set_security_callback(SSL_CTX *ctx,
                                           int (*cb)(SSL *s, SSL_CTX *ctx, int op,
                                                     int bits, int nid,
                                                     void *other, void *ex));

        void SSL_set_security_callback(SSL *s, int (*cb)(SSL *s, SSL_CTX *ctx, int op,
                                                         int bits, int nid,
                                                         void *other, void *ex));

        int (*SSL_CTX_get_security_callback(const SSL_CTX *ctx))(SSL *s, SSL_CTX *ctx, int op,
                                                                 int bits, int nid, void *other,
                                                                 void *ex);
        int (*SSL_get_security_callback(const SSL *s))(SSL *s, SSL_CTX *ctx, int op,
                                                       int bits, int nid, void *other,
                                                       void *ex);

        void SSL_CTX_set0_security_ex_data(SSL_CTX *ctx, void *ex);
        void SSL_set0_security_ex_data(SSL *s, void *ex);

        void *SSL_CTX_get0_security_ex_data(const SSL_CTX *ctx);
        void *SSL_get0_security_ex_data(const SSL *s);

       The functions SSL_CTX_set_security_level() and SSL_set_security_level()
       set the security level to level. If not set the library default
       security level is used.

       The functions SSL_CTX_get_security_level() and SSL_get_security_level()
       retrieve the current security level.

       SSL_CTX_set_security_callback(), SSL_set_security_callback(),
       SSL_CTX_get_security_callback() and SSL_get_security_callback() get or
       set the security callback associated with ctx or s. If not set a
       default security callback is used. The meaning of the parameters and
       the behaviour of the default callbacks is described below.

       SSL_CTX_set0_security_ex_data(), SSL_set0_security_ex_data(),
       SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() set the
       extra data pointer passed to the ex parameter of the callback. This
       value is passed to the callback verbatim and can be set to any
       convenient application specific value.

       If an application doesn't set its own security callback the default
       callback is used. It is intended to provide sane defaults. The meaning
       of each level is described below.

       Level 0
           Everything is permitted. This retains compatibility with previous
           versions of OpenSSL.

       Level 1
           The security level corresponds to a minimum of 80 bits of security.
           Any parameters offering below 80 bits of security are excluded. As
           a result RSA, DSA and DH keys shorter than 1024 bits and ECC keys
           shorter than 160 bits are prohibited. All export cipher suites are
           prohibited since they all offer less than 80 bits of security. SSL
           version 2 is prohibited. Any cipher suite using MD5 for the MAC is
           also prohibited.

       Level 2
           Security level set to 112 bits of security. As a result RSA, DSA
           and DH keys shorter than 2048 bits and ECC keys shorter than 224
           bits are prohibited.  In addition to the level 1 exclusions any
           cipher suite using RC4 is also prohibited. SSL version 3 is also
           not allowed. Compression is disabled.

       Level 3
           Security level set to 128 bits of security. As a result RSA, DSA
           and DH keys shorter than 3072 bits and ECC keys shorter than 256
           bits are prohibited.  In addition to the level 2 exclusions cipher
           suites not offering forward secrecy are prohibited. TLS versions
           below 1.1 are not permitted. Session tickets are disabled.

       Level 4
           Security level set to 192 bits of security. As a result RSA, DSA
           and DH keys shorter than 7680 bits and ECC keys shorter than 384
           bits are prohibited.  Cipher suites using SHA1 for the MAC are
           prohibited. TLS versions below 1.2 are not permitted.

       Level 5
           Security level set to 256 bits of security. As a result RSA, DSA
           and DH keys shorter than 15360 bits and ECC keys shorter than 512
           bits are prohibited.

       Documentation to be provided.

       The default security level can be configured when OpenSSL is compiled
       by setting -DOPENSSL_TLS_SECURITY_LEVEL=level. If not set then 1 is

       The security framework disables or reject parameters inconsistent with
       the set security level. In the past this was difficult as applications
       had to set a number of distinct parameters (supported ciphers,
       supported curves supported signature algorithms) to achieve this end
       and some cases (DH parameter size for example) could not be checked at

       By setting an appropriate security level much of this complexity can be

       The bits of security limits affect all relevant parameters including
       cipher suite encryption algorithms, supported ECC curves, supported
       signature algorithms, DH parameter sizes, certificate key sizes and
       signature algorithms. This limit applies no matter what other custom
       settings an application has set: so if the cipher suite is set to ALL
       then only cipher suites consistent with the security level are

       See SP800-57 for how the security limits are related to individual

       Some security levels require large key sizes for non-ECC public key
       algorithms which can severely degrade performance. For example 256 bits
       of security requires the use of RSA keys of at least 15360 bits in

       Some restrictions can be gracefully handled: for example cipher suites
       offering insufficient security are not sent by the client and will not
       be selected by the server. Other restrictions such as the peer
       certificate key size or the DH parameter size will abort the handshake
       with a fatal alert.

       Attempts to set certificates or parameters with insufficient security
       are also blocked. For example trying to set a certificate using a 512
       bit RSA key using SSL_CTX_use_certificate() at level 1. Applications
       which do not check the return values for errors will misbehave: for
       example it might appear that a certificate is not set at all because it
       had been rejected.

       SSL_CTX_set_security_level() and SSL_set_security_level() do not return

       SSL_CTX_get_security_level() and SSL_get_security_level() return a
       integer that represents the security level with SSL_CTX or SSL,

       SSL_CTX_set_security_callback() and SSL_set_security_callback() do not
       return values.

       SSL_CTX_get_security_callback() and SSL_get_security_callback() return
       the pointer to the security callback or NULL if the callback is not

       SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() return
       the extra data pointer or NULL if the ex data is not set.

       These functions were added in OpenSSL 1.1.0.

       Copyright 2014-2020 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

1.1.1i                            2020-12-10     SSL_CTX_set_security_level(3)