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 with the exception of
SHA1 allowed for signatures. 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
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 added in OpenSSL 1.1.0.
COPYRIGHT
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
<https://www.openssl.org/source/license.html>;.
1.1.1k 2024-10-09 SSL_CTX_SET_SECURITY_LEVEL(3)
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