164 lines
6.5 KiB
Text
164 lines
6.5 KiB
Text
=pod
|
|
|
|
=head1 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
|
|
|
|
=head1 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);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
The functions SSL_CTX_set_security_level() and SSL_set_security_level() set
|
|
the security level to B<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 B<ctx> or B<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 B<ex> parameter of the callback. This
|
|
value is passed to the callback verbatim and can be set to any convenient
|
|
application specific value.
|
|
|
|
=head1 DEFAULT CALLBACK BEHAVIOUR
|
|
|
|
If an application doesn't set it's own security callback the default
|
|
callback is used. It is intended to provide sane defaults. The meaning
|
|
of each level is described below.
|
|
|
|
=over 4
|
|
|
|
=item B<Level 0>
|
|
|
|
Everything is permitted. This retains compatibility with previous versions of
|
|
OpenSSL.
|
|
|
|
=item B<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 ciphersuites are prohibited since they all offer
|
|
less than 80 bits of security. SSL version 2 is prohibited. Any ciphersuite
|
|
using MD5 for the MAC is also prohibited.
|
|
|
|
=item B<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 ciphersuite using RC4 is also
|
|
prohibited. SSL version 3 is also not allowed. Compression is disabled.
|
|
|
|
=item B<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 ciphersuites not offering forward
|
|
secrecy are prohibited. TLS versions below 1.1 are not permitted. Session
|
|
tickets are disabled.
|
|
|
|
=item B<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.
|
|
Ciphersuites using SHA1 for the MAC are prohibited. TLS versions below 1.2 are
|
|
not permitted.
|
|
|
|
=item B<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.
|
|
|
|
=back
|
|
|
|
=head1 APPLICATION DEFINED SECURITY CALLBACKS
|
|
|
|
TBA
|
|
|
|
=head1 NOTES
|
|
|
|
B<WARNING> at this time setting the security level higher than 1 for
|
|
general internet use is likely to cause B<considerable> interoperability
|
|
issues and is not recommended. This is because the B<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 B<-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
|
|
ciphersuite 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 ciphersuite is set to B<ALL>
|
|
then only ciphersuites 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 ciphersuites
|
|
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.
|
|
|
|
=head1 SEE ALSO
|
|
|
|
TBA
|
|
|
|
=head1 HISTORY
|
|
|
|
These functions were first added to OpenSSL 1.1.0
|
|
|
|
=cut
|