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SSL_CTX_SET_SECURITY_LEVEL(3)	    OpenSSL	 SSL_CTX_SET_SECURITY_LEVEL(3)

NAME
       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

SYNOPSIS
	#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);

DESCRIPTION
       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.

DEFAULT	CALLBACK BEHAVIOUR
       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.

APPLICATION DEFINED SECURITY CALLBACKS
       Documentation to	be provided.

NOTES
       WARNING at this time setting the	security level higher than 1 for
       general internet	use is likely to cause considerable interoperability
       issues and is not recommended. This is because the SHA1 algorithm is
       very widely used	in certificates	and will be rejected at	levels higher
       than 1 because it only offers 80	bits of	security.

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

       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
       all.

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

       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
       permissible.

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

       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
       size.

       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.

RETURN VALUES
       SSL_CTX_set_security_level() and	SSL_set_security_level() do not	return
       values.

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

       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
       set.

       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.

HISTORY
       These functions were first added	to OpenSSL 1.1.0

COPYRIGHT
       Copyright 2014-2018 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>.

1.1.1a				  2018-11-20	 SSL_CTX_SET_SECURITY_LEVEL(3)

NAME | SYNOPSIS | DESCRIPTION | DEFAULT CALLBACK BEHAVIOUR | APPLICATION DEFINED SECURITY CALLBACKS | NOTES | RETURN VALUES | HISTORY | COPYRIGHT

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