1SSL_CTX_SET_SECURITY_LEVEL(3) OpenSSL SSL_CTX_SET_SECURITY_LEVEL(3)
2
6 SSL_CTX_set_security_level, SSL_set_security_level,
7 SSL_CTX_get_security_level, SSL_get_security_level,
8 SSL_CTX_set_security_callback, SSL_set_security_callback,
9 SSL_CTX_get_security_callback, SSL_get_security_callback,
10 SSL_CTX_set0_security_ex_data, SSL_set0_security_ex_data,
11 SSL_CTX_get0_security_ex_data, SSL_get0_security_ex_data - SSL/TLS
12 security framework
13
15 #include <openssl/ssl.h>
16 void SSL_CTX_set_security_level(SSL_CTX *ctx, int level);
18 void SSL_set_security_level(SSL *s, int level);
19 int SSL_CTX_get_security_level(const SSL_CTX *ctx);
21 int SSL_get_security_level(const SSL *s);
22 void SSL_CTX_set_security_callback(SSL_CTX *ctx,
24 int (*cb)(SSL *s, SSL_CTX *ctx, int op,
25 int bits, int nid,
26 void *other, void *ex));
27 void SSL_set_security_callback(SSL *s, int (*cb)(SSL *s, SSL_CTX *ctx, int op,
29 int bits, int nid,
30 void *other, void *ex));
31 int (*SSL_CTX_get_security_callback(const SSL_CTX *ctx))(SSL *s, SSL_CTX *ctx, int op,
33 int bits, int nid, void *other,
34 void *ex);
35 int (*SSL_get_security_callback(const SSL *s))(SSL *s, SSL_CTX *ctx, int op,
36 int bits, int nid, void *other,
37 void *ex);
38 void SSL_CTX_set0_security_ex_data(SSL_CTX *ctx, void *ex);
40 void SSL_set0_security_ex_data(SSL *s, void *ex);
41 void *SSL_CTX_get0_security_ex_data(const SSL_CTX *ctx);
43 void *SSL_get0_security_ex_data(const SSL *s);
44
46 The functions SSL_CTX_set_security_level() and SSL_set_security_level()
47 set the security level to level. If not set the library default
48 security level is used.
49 The functions SSL_CTX_get_security_level() and SSL_get_security_level()
51 retrieve the current security level.
52 SSL_CTX_set_security_callback(), SSL_set_security_callback(),
54 SSL_CTX_get_security_callback() and SSL_get_security_callback() get or
55 set the security callback associated with ctx or s. If not set a
56 default security callback is used. The meaning of the parameters and
57 the behaviour of the default callbacks is described below.
58 SSL_CTX_set0_security_ex_data(), SSL_set0_security_ex_data(),
60 SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() set the
61 extra data pointer passed to the ex parameter of the callback. This
62 value is passed to the callback verbatim and can be set to any
63 convenient application specific value.
64
66 If an application doesn't set its own security callback the default
67 callback is used. It is intended to provide sane defaults. The meaning
68 of each level is described below.
69 Level 0
71 Everything is permitted. This retains compatibility with previous
72 versions of OpenSSL.
73 Level 1
75 The security level corresponds to a minimum of 80 bits of security.
76 Any parameters offering below 80 bits of security are excluded. As
77 a result RSA, DSA and DH keys shorter than 1024 bits and ECC keys
78 shorter than 160 bits are prohibited. All export cipher suites are
79 prohibited since they all offer less than 80 bits of security. SSL
80 version 2 is prohibited. Any cipher suite using MD5 for the MAC is
81 also prohibited.
82 Level 2
84 Security level set to 112 bits of security with the exception of
85 SHA1 allowed for signatures. As a result RSA, DSA and DH keys
86 shorter than 2048 bits and ECC keys shorter than 224 bits are
87 prohibited. In addition to the level 1 exclusions any cipher suite
88 using RC4 is also prohibited. SSL version 3 is also not allowed.
89 Compression is disabled.
90 Level 3
92 Security level set to 128 bits of security. As a result RSA, DSA
93 and DH keys shorter than 3072 bits and ECC keys shorter than 256
94 bits are prohibited. In addition to the level 2 exclusions cipher
95 suites not offering forward secrecy are prohibited. TLS versions
96 below 1.1 are not permitted. Session tickets are disabled.
97 Level 4
99 Security level set to 192 bits of security. As a result RSA, DSA
100 and DH keys shorter than 7680 bits and ECC keys shorter than 384
101 bits are prohibited. Cipher suites using SHA1 for the MAC are
102 prohibited. TLS versions below 1.2 are not permitted.
103 Level 5
105 Security level set to 256 bits of security. As a result RSA, DSA
106 and DH keys shorter than 15360 bits and ECC keys shorter than 512
107 bits are prohibited.
108
110 Documentation to be provided.
111
113 WARNING at this time setting the security level higher than 1 for
114 general internet use is likely to cause considerable interoperability
115 issues and is not recommended. This is because the SHA1 algorithm is
116 very widely used in certificates and will be rejected at levels higher
117 than 1 because it only offers 80 bits of security.
118 The default security level can be configured when OpenSSL is compiled
120 by setting -DOPENSSL_TLS_SECURITY_LEVEL=level. If not set then 1 is
121 used.
122 The security framework disables or reject parameters inconsistent with
124 the set security level. In the past this was difficult as applications
125 had to set a number of distinct parameters (supported ciphers,
126 supported curves supported signature algorithms) to achieve this end
127 and some cases (DH parameter size for example) could not be checked at
128 all.
129 By setting an appropriate security level much of this complexity can be
131 avoided.
132 The bits of security limits affect all relevant parameters including
134 cipher suite encryption algorithms, supported ECC curves, supported
135 signature algorithms, DH parameter sizes, certificate key sizes and
136 signature algorithms. This limit applies no matter what other custom
137 settings an application has set: so if the cipher suite is set to ALL
138 then only cipher suites consistent with the security level are
139 permissible.
140 See SP800-57 for how the security limits are related to individual
142 algorithms.
143 Some security levels require large key sizes for non-ECC public key
145 algorithms which can severely degrade performance. For example 256 bits
146 of security requires the use of RSA keys of at least 15360 bits in
147 size.
148 Some restrictions can be gracefully handled: for example cipher suites
150 offering insufficient security are not sent by the client and will not
151 be selected by the server. Other restrictions such as the peer
152 certificate key size or the DH parameter size will abort the handshake
153 with a fatal alert.
154 Attempts to set certificates or parameters with insufficient security
156 are also blocked. For example trying to set a certificate using a 512
157 bit RSA key using SSL_CTX_use_certificate() at level 1. Applications
158 which do not check the return values for errors will misbehave: for
159 example it might appear that a certificate is not set at all because it
160 had been rejected.
161
163 SSL_CTX_set_security_level() and SSL_set_security_level() do not return
164 values.
165 SSL_CTX_get_security_level() and SSL_get_security_level() return a
167 integer that represents the security level with SSL_CTX or SSL,
168 respectively.
169 SSL_CTX_set_security_callback() and SSL_set_security_callback() do not
171 return values.
172 SSL_CTX_get_security_callback() and SSL_get_security_callback() return
174 the pointer to the security callback or NULL if the callback is not
175 set.
176 SSL_CTX_get0_security_ex_data() and SSL_get0_security_ex_data() return
178 the extra data pointer or NULL if the ex data is not set.
179
181 These functions were first added to OpenSSL 1.1.0
182
184 Copyright 2014-2018 The OpenSSL Project Authors. All Rights Reserved.
185 Licensed under the OpenSSL license (the "License"). You may not use
187 this file except in compliance with the License. You can obtain a copy
188 in the file LICENSE in the source distribution or at
189 <https://www.openssl.org/source/license.html>.
1901.1.1 2019-05-11 SSL_CTX_SET_SECURITY_LEVEL(3)