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 117The default security level can be configured when OpenSSL is compiled by 118setting B<-DOPENSSL_TLS_SECURITY_LEVEL=level>. If not set then 1 is used. 119 120The security framework disables or reject parameters inconsistent with the 121set security level. In the past this was difficult as applications had to set 122a number of distinct parameters (supported ciphers, supported curves supported 123signature algorithms) to achieve this end and some cases (DH parameter size 124for example) could not be checked at all. 125 126By setting an appropriate security level much of this complexity can be 127avoided. 128 129The bits of security limits affect all relevant parameters including 130cipher suite encryption algorithms, supported ECC curves, supported 131signature algorithms, DH parameter sizes, certificate key sizes and 132signature algorithms. This limit applies no matter what other custom 133settings an application has set: so if the cipher suite is set to B<ALL> 134then only cipher suites consistent with the security level are permissible. 135 136See SP800-57 for how the security limits are related to individual 137algorithms. 138 139Some security levels require large key sizes for non-ECC public key 140algorithms which can severely degrade performance. For example 256 bits 141of security requires the use of RSA keys of at least 15360 bits in size. 142 143Some restrictions can be gracefully handled: for example cipher suites 144offering insufficient security are not sent by the client and will not 145be selected by the server. Other restrictions such as the peer certificate 146key size or the DH parameter size will abort the handshake with a fatal 147alert. 148 149Attempts to set certificates or parameters with insufficient security are 150also blocked. For example trying to set a certificate using a 512 bit RSA 151key using SSL_CTX_use_certificate() at level 1. Applications which do not 152check the return values for errors will misbehave: for example it might 153appear that a certificate is not set at all because it had been rejected. 154 155=head1 RETURN VALUES 156 157SSL_CTX_set_security_level() and SSL_set_security_level() do not return values. 158 159SSL_CTX_get_security_level() and SSL_get_security_level() return a integer that 160represents the security level with B<SSL_CTX> or B<SSL>, respectively. 161 162SSL_CTX_set_security_callback() and SSL_set_security_callback() do not return 163values. 164 165SSL_CTX_get_security_callback() and SSL_get_security_callback() return the pointer 166to the security callback or NULL if the callback is not set. 167 168SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() return the extra 169data pointer or NULL if the ex data is not set. 170 171=head1 HISTORY 172 173These functions were added in OpenSSL 1.1.0. 174 175=head1 COPYRIGHT 176 177Copyright 2014-2020 The OpenSSL Project Authors. All Rights Reserved. 178 179Licensed under the OpenSSL license (the "License"). You may not use 180this file except in compliance with the License. You can obtain a copy 181in the file LICENSE in the source distribution or at 182L<https://www.openssl.org/source/license.html>. 183 184=cut 185