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Update security framework docs.

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Dr. Stephen Henson 2014-04-05 13:29:41 +01:00
parent 6cc0068430
commit b7e46a9bce
1 changed files with 31 additions and 20 deletions
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51
doc/ssl/SSL_CTX_set_security_level.pod
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@ -67,31 +67,39 @@ OpenSSL.
=item B<Level 1>
The security level set to 80 bits of security. Any parameters offering
below 80 bits of security are excluded. As a result all export ciphersuites
are prohibited. SSL version 2 is prohibited. Any ciphersuite using MD5 for
the MAC is also prohibited.
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. In addition to the level 1
exclusions any ciphersuite using RC4 is also prohibited. SSL version
3 is also not allowed. Compression is disabled.
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>
Ssecurity level set to 128 bits of security. In addition to the level 2
exclusions any ciphersuite not offering forward secrecy are prohibited.
TLS versions below 1.1 are not permitted. Session tickets are disabled.
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. TLS versions below 1.2 are not
permitted.
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.
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
@ -101,6 +109,12 @@ 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.
@ -123,13 +137,9 @@ then only ciphersuites consistent with the security level are permissible.
See SP800-57 for how the security limits are related to individual
algorithms.
SHA1 is in widespread use in certificates but it only offers 80 bits
of security. This is problematic as anything above level 1 will reject
them.
Some security levels require large key sizes for none-ECC public key
algorithms. For example 256 bits of security requires the use of RSA
keys of at least 15360 bits in size.
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
@ -140,7 +150,8 @@ 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.
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