1=pod 2 3=head1 NAME 4 5SSL_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 6 7=head1 SYNOPSIS 8 9 #include <openssl/ssl.h> 10 11 void SSL_CTX_set_security_level(SSL_CTX *ctx, int level); 12 void SSL_set_security_level(SSL *s, int level); 13 14 int SSL_CTX_get_security_level(const SSL_CTX *ctx); 15 int SSL_get_security_level(const SSL *s); 16 17 void SSL_CTX_set_security_callback(SSL_CTX *ctx, 18 int (*cb)(SSL *s, SSL_CTX *ctx, int op, 19 int bits, int nid, 20 void *other, void *ex)); 21 22 void SSL_set_security_callback(SSL *s, int (*cb)(SSL *s, SSL_CTX *ctx, int op, 23 int bits, int nid, 24 void *other, void *ex)); 25 26 int (*SSL_CTX_get_security_callback(const SSL_CTX *ctx))(SSL *s, SSL_CTX *ctx, int op, 27 int bits, int nid, void *other, 28 void *ex); 29 int (*SSL_get_security_callback(const SSL *s))(SSL *s, SSL_CTX *ctx, int op, 30 int bits, int nid, void *other, 31 void *ex); 32 33 void SSL_CTX_set0_security_ex_data(SSL_CTX *ctx, void *ex); 34 void SSL_set0_security_ex_data(SSL *s, void *ex); 35 36 void *SSL_CTX_get0_security_ex_data(const SSL_CTX *ctx); 37 void *SSL_get0_security_ex_data(const SSL *s); 38 39=head1 DESCRIPTION 40 41The functions SSL_CTX_set_security_level() and SSL_set_security_level() set 42the security level to B<level>. If not set the library default security level 43is used. 44 45The functions SSL_CTX_get_security_level() and SSL_get_security_level() 46retrieve the current security level. 47 48SSL_CTX_set_security_callback(), SSL_set_security_callback(), 49SSL_CTX_get_security_callback() and SSL_get_security_callback() get or set 50the security callback associated with B<ctx> or B<s>. If not set a default 51security callback is used. The meaning of the parameters and the behaviour 52of the default callbacks is described below. 53 54SSL_CTX_set0_security_ex_data(), SSL_set0_security_ex_data(), 55SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() set the 56extra data pointer passed to the B<ex> parameter of the callback. This 57value is passed to the callback verbatim and can be set to any convenient 58application specific value. 59 60=head1 DEFAULT CALLBACK BEHAVIOUR 61 62If an application doesn't set its own security callback the default 63callback is used. It is intended to provide sane defaults. The meaning 64of each level is described below. 65 66=over 4 67 68=item B<Level 0> 69 70Everything is permitted. This retains compatibility with previous versions of 71OpenSSL. 72 73=item B<Level 1> 74 75The security level corresponds to a minimum of 80 bits of security. Any 76parameters offering below 80 bits of security are excluded. As a result RSA, 77DSA and DH keys shorter than 1024 bits and ECC keys shorter than 160 bits 78are prohibited. All export cipher suites are prohibited since they all offer 79less than 80 bits of security. SSL version 2 is prohibited. Any cipher suite 80using MD5 for the MAC is also prohibited. 81 82=item B<Level 2> 83 84Security level set to 112 bits of security. As a result RSA, DSA and DH keys 85shorter than 2048 bits and ECC keys shorter than 224 bits are prohibited. 86In addition to the level 1 exclusions any cipher suite using RC4 is also 87prohibited. SSL version 3 is also not allowed. Compression is disabled. 88 89=item B<Level 3> 90 91Security level set to 128 bits of security. As a result RSA, DSA and DH keys 92shorter than 3072 bits and ECC keys shorter than 256 bits are prohibited. 93In addition to the level 2 exclusions cipher suites not offering forward 94secrecy are prohibited. TLS versions below 1.1 are not permitted. Session 95tickets are disabled. 96 97=item B<Level 4> 98 99Security level set to 192 bits of security. As a result RSA, DSA and 100DH keys shorter than 7680 bits and ECC keys shorter than 384 bits are 101prohibited. Cipher suites using SHA1 for the MAC are prohibited. TLS 102versions below 1.2 are not permitted. 103 104=item B<Level 5> 105 106Security level set to 256 bits of security. As a result RSA, DSA and DH keys 107shorter than 15360 bits and ECC keys shorter than 512 bits are prohibited. 108 109=back 110 111=head1 APPLICATION DEFINED SECURITY CALLBACKS 112 113I<Documentation to be provided.> 114 115=head1 NOTES 116 117B<WARNING> at this time setting the security level higher than 1 for 118general internet use is likely to cause B<considerable> interoperability 119issues and is not recommended. This is because the B<SHA1> algorithm 120is very widely used in certificates and will be rejected at levels 121higher than 1 because it only offers 80 bits of security. 122 123The default security level can be configured when OpenSSL is compiled by 124setting B<-DOPENSSL_TLS_SECURITY_LEVEL=level>. If not set then 1 is used. 125 126The security framework disables or reject parameters inconsistent with the 127set security level. In the past this was difficult as applications had to set 128a number of distinct parameters (supported ciphers, supported curves supported 129signature algorithms) to achieve this end and some cases (DH parameter size 130for example) could not be checked at all. 131 132By setting an appropriate security level much of this complexity can be 133avoided. 134 135The bits of security limits affect all relevant parameters including 136cipher suite encryption algorithms, supported ECC curves, supported 137signature algorithms, DH parameter sizes, certificate key sizes and 138signature algorithms. This limit applies no matter what other custom 139settings an application has set: so if the cipher suite is set to B<ALL> 140then only cipher suites consistent with the security level are permissible. 141 142See SP800-57 for how the security limits are related to individual 143algorithms. 144 145Some security levels require large key sizes for non-ECC public key 146algorithms which can severely degrade performance. For example 256 bits 147of security requires the use of RSA keys of at least 15360 bits in size. 148 149Some restrictions can be gracefully handled: for example cipher suites 150offering insufficient security are not sent by the client and will not 151be selected by the server. Other restrictions such as the peer certificate 152key size or the DH parameter size will abort the handshake with a fatal 153alert. 154 155Attempts to set certificates or parameters with insufficient security are 156also blocked. For example trying to set a certificate using a 512 bit RSA 157key using SSL_CTX_use_certificate() at level 1. Applications which do not 158check the return values for errors will misbehave: for example it might 159appear that a certificate is not set at all because it had been rejected. 160 161=head1 RETURN VALUES 162 163SSL_CTX_set_security_level() and SSL_set_security_level() do not return values. 164 165SSL_CTX_get_security_level() and SSL_get_security_level() return a integer that 166represents the security level with B<SSL_CTX> or B<SSL>, respectively. 167 168SSL_CTX_set_security_callback() and SSL_set_security_callback() do not return 169values. 170 171SSL_CTX_get_security_callback() and SSL_get_security_callback() return the pointer 172to the security callback or NULL if the callback is not set. 173 174SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() return the extra 175data pointer or NULL if the ex data is not set. 176 177=head1 HISTORY 178 179These functions were first added to OpenSSL 1.1.0 180 181=head1 COPYRIGHT 182 183Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved. 184 185Licensed under the OpenSSL license (the "License"). You may not use 186this file except in compliance with the License. You can obtain a copy 187in the file LICENSE in the source distribution or at 188L<https://www.openssl.org/source/license.html>. 189 190=cut 191