X509_VERIFY_PARAM_set_flags.pod revision 331638 
1=pod
2
3=head1 NAME
4
5X509_VERIFY_PARAM_set_flags, X509_VERIFY_PARAM_clear_flags, X509_VERIFY_PARAM_get_flags, X509_VERIFY_PARAM_set_purpose, X509_VERIFY_PARAM_set_trust, X509_VERIFY_PARAM_set_depth, X509_VERIFY_PARAM_get_depth, X509_VERIFY_PARAM_set_time, X509_VERIFY_PARAM_add0_policy, X509_VERIFY_PARAM_set1_policies, X509_VERIFY_PARAM_set1_host, X509_VERIFY_PARAM_add1_host, X509_VERIFY_PARAM_set_hostflags, X509_VERIFY_PARAM_get0_peername, X509_VERIFY_PARAM_set1_email, X509_VERIFY_PARAM_set1_ip, X509_VERIFY_PARAM_set1_ip_asc - X509 verification parameters
6
7=head1 SYNOPSIS
8
9 #include <openssl/x509_vfy.h>
10
11 int X509_VERIFY_PARAM_set_flags(X509_VERIFY_PARAM *param, unsigned long flags);
12 int X509_VERIFY_PARAM_clear_flags(X509_VERIFY_PARAM *param,
13							unsigned long flags);
14 unsigned long X509_VERIFY_PARAM_get_flags(X509_VERIFY_PARAM *param);
15
16 int X509_VERIFY_PARAM_set_purpose(X509_VERIFY_PARAM *param, int purpose);
17 int X509_VERIFY_PARAM_set_trust(X509_VERIFY_PARAM *param, int trust);
18
19 void X509_VERIFY_PARAM_set_time(X509_VERIFY_PARAM *param, time_t t);
20
21 int X509_VERIFY_PARAM_add0_policy(X509_VERIFY_PARAM *param,
22						ASN1_OBJECT *policy);
23 int X509_VERIFY_PARAM_set1_policies(X509_VERIFY_PARAM *param, 
24					STACK_OF(ASN1_OBJECT) *policies);
25
26 void X509_VERIFY_PARAM_set_depth(X509_VERIFY_PARAM *param, int depth);
27 int X509_VERIFY_PARAM_get_depth(const X509_VERIFY_PARAM *param);
28
29 int X509_VERIFY_PARAM_set1_host(X509_VERIFY_PARAM *param,
30				 const char *name, size_t namelen);
31 int X509_VERIFY_PARAM_add1_host(X509_VERIFY_PARAM *param,
32                                 const char *name, size_t namelen);
33 void X509_VERIFY_PARAM_set_hostflags(X509_VERIFY_PARAM *param,
34				      unsigned int flags);
35 char *X509_VERIFY_PARAM_get0_peername(X509_VERIFY_PARAM *param);
36 int X509_VERIFY_PARAM_set1_email(X509_VERIFY_PARAM *param,
37				 const char *email, size_t emaillen);
38 int X509_VERIFY_PARAM_set1_ip(X509_VERIFY_PARAM *param,
39			       const unsigned char *ip, size_t iplen);
40 int X509_VERIFY_PARAM_set1_ip_asc(X509_VERIFY_PARAM *param, const char *ipasc);
41
42=head1 DESCRIPTION
43
44These functions manipulate the B<X509_VERIFY_PARAM> structure associated with
45a certificate verification operation. 
46
47The X509_VERIFY_PARAM_set_flags() function sets the flags in B<param> by oring
48it with B<flags>. See the B<VERIFICATION FLAGS> section for a complete
49description of values the B<flags> parameter can take.
50
51X509_VERIFY_PARAM_get_flags() returns the flags in B<param>.
52
53X509_VERIFY_PARAM_clear_flags() clears the flags B<flags> in B<param>.
54
55X509_VERIFY_PARAM_set_purpose() sets the verification purpose in B<param>
56to B<purpose>. This determines the acceptable purpose of the certificate
57chain, for example SSL client or SSL server.
58
59X509_VERIFY_PARAM_set_trust() sets the trust setting in B<param> to 
60B<trust>.
61
62X509_VERIFY_PARAM_set_time() sets the verification time in B<param> to
63B<t>. Normally the current time is used.
64
65X509_VERIFY_PARAM_add0_policy() enables policy checking (it is disabled
66by default) and adds B<policy> to the acceptable policy set.
67
68X509_VERIFY_PARAM_set1_policies() enables policy checking (it is disabled
69by default) and sets the acceptable policy set to B<policies>. Any existing
70policy set is cleared. The B<policies> parameter can be B<NULL> to clear
71an existing policy set.
72
73X509_VERIFY_PARAM_set_depth() sets the maximum verification depth to B<depth>.
74That is the maximum number of untrusted CA certificates that can appear in a
75chain.
76
77X509_VERIFY_PARAM_set1_host() sets the expected DNS hostname to
78B<name> clearing any previously specified host name or names.  If
79B<name> is NULL, or empty the list of hostnames is cleared, and
80name checks are not performed on the peer certificate.  If B<name>
81is NUL-terminated, B<namelen> may be zero, otherwise B<namelen>
82must be set to the length of B<name>.  When a hostname is specified,
83certificate verification automatically invokes L<X509_check_host(3)>
84with flags equal to the B<flags> argument given to
85B<X509_VERIFY_PARAM_set_hostflags()> (default zero).  Applications
86are strongly advised to use this interface in preference to explicitly
87calling L<X509_check_host(3)>, hostname checks are out of scope
88with the DANE-EE(3) certificate usage, and the internal check will
89be suppressed as appropriate when DANE support is added to OpenSSL.
90
91X509_VERIFY_PARAM_add1_host() adds B<name> as an additional reference
92identifer that can match the peer's certificate.  Any previous names
93set via X509_VERIFY_PARAM_set1_host() or X509_VERIFY_PARAM_add1_host()
94are retained, no change is made if B<name> is NULL or empty.  When
95multiple names are configured, the peer is considered verified when
96any name matches.
97
98X509_VERIFY_PARAM_get0_peername() returns the DNS hostname or subject
99CommonName from the peer certificate that matched one of the reference
100identifiers.  When wildcard matching is not disabled, or when a
101reference identifier specifies a parent domain (starts with ".")
102rather than a hostname, the peer name may be a wildcard name or a
103sub-domain of the reference identifier respectively.  The return
104string is allocated by the library and is no longer valid once the
105associated B<param> argument is freed.  Applications must not free
106the return value.
107
108X509_VERIFY_PARAM_set1_email() sets the expected RFC822 email address to
109B<email>.  If B<email> is NUL-terminated, B<emaillen> may be zero, otherwise
110B<emaillen> must be set to the length of B<email>.  When an email address
111is specified, certificate verification automatically invokes
112L<X509_check_email(3)>.
113
114X509_VERIFY_PARAM_set1_ip() sets the expected IP address to B<ip>.
115The B<ip> argument is in binary format, in network byte-order and
116B<iplen> must be set to 4 for IPv4 and 16 for IPv6.  When an IP
117address is specified, certificate verification automatically invokes
118L<X509_check_ip(3)>.
119
120X509_VERIFY_PARAM_set1_ip_asc() sets the expected IP address to
121B<ipasc>.  The B<ipasc> argument is a NUL-terminal ASCII string:
122dotted decimal quad for IPv4 and colon-separated hexadecimal for
123IPv6.  The condensed "::" notation is supported for IPv6 addresses.
124
125=head1 RETURN VALUES
126
127X509_VERIFY_PARAM_set_flags(), X509_VERIFY_PARAM_clear_flags(),
128X509_VERIFY_PARAM_set_purpose(), X509_VERIFY_PARAM_set_trust(),
129X509_VERIFY_PARAM_add0_policy() X509_VERIFY_PARAM_set1_policies(),
130X509_VERIFY_PARAM_set1_host(), X509_VERIFY_PARAM_set_hostflags(),
131X509_VERIFY_PARAM_set1_email(), X509_VERIFY_PARAM_set1_ip() and
132X509_VERIFY_PARAM_set1_ip_asc() return 1 for success and 0 for
133failure.
134
135X509_VERIFY_PARAM_get_flags() returns the current verification flags.
136
137X509_VERIFY_PARAM_set_time() and X509_VERIFY_PARAM_set_depth() do not return
138values.
139
140X509_VERIFY_PARAM_get_depth() returns the current verification depth.
141
142=head1 VERIFICATION FLAGS
143
144The verification flags consists of zero or more of the following flags
145ored together.
146
147B<X509_V_FLAG_CRL_CHECK> enables CRL checking for the certificate chain leaf
148certificate. An error occurs if a suitable CRL cannot be found. 
149
150B<X509_V_FLAG_CRL_CHECK_ALL> enables CRL checking for the entire certificate
151chain.
152
153B<X509_V_FLAG_IGNORE_CRITICAL> disabled critical extension checking. By default
154any unhandled critical extensions in certificates or (if checked) CRLs results
155in a fatal error. If this flag is set unhandled critical extensions are
156ignored. B<WARNING> setting this option for anything other than debugging
157purposes can be a security risk. Finer control over which extensions are
158supported can be performed in the verification callback.
159
160THe B<X509_V_FLAG_X509_STRICT> flag disables workarounds for some broken
161certificates and makes the verification strictly apply B<X509> rules.
162
163B<X509_V_FLAG_ALLOW_PROXY_CERTS> enables proxy certificate verification.
164
165B<X509_V_FLAG_POLICY_CHECK> enables certificate policy checking, by default
166no policy checking is peformed. Additional information is sent to the 
167verification callback relating to policy checking.
168
169B<X509_V_FLAG_EXPLICIT_POLICY>, B<X509_V_FLAG_INHIBIT_ANY> and
170B<X509_V_FLAG_INHIBIT_MAP> set the B<require explicit policy>, B<inhibit any
171policy> and B<inhibit policy mapping> flags respectively as defined in
172B<RFC3280>. Policy checking is automatically enabled if any of these flags
173are set.
174
175If B<X509_V_FLAG_NOTIFY_POLICY> is set and the policy checking is successful
176a special status code is set to the verification callback. This permits it
177to examine the valid policy tree and perform additional checks or simply
178log it for debugging purposes.
179
180By default some additional features such as indirect CRLs and CRLs signed by
181different keys are disabled. If B<X509_V_FLAG_EXTENDED_CRL_SUPPORT> is set
182they are enabled.
183
184If B<X509_V_FLAG_USE_DELTAS> ise set delta CRLs (if present) are used to
185determine certificate status. If not set deltas are ignored.
186
187B<X509_V_FLAG_CHECK_SS_SIGNATURE> enables checking of the root CA self signed
188cerificate signature. By default this check is disabled because it doesn't
189add any additional security but in some cases applications might want to
190check the signature anyway. A side effect of not checking the root CA
191signature is that disabled or unsupported message digests on the root CA
192are not treated as fatal errors.
193
194The B<X509_V_FLAG_CB_ISSUER_CHECK> flag enables debugging of certificate
195issuer checks. It is B<not> needed unless you are logging certificate
196verification. If this flag is set then additional status codes will be sent
197to the verification callback and it B<must> be prepared to handle such cases
198without assuming they are hard errors.
199
200The B<X509_V_FLAG_NO_ALT_CHAINS> flag suppresses checking for alternative
201chains. By default, when building a certificate chain, if the first certificate
202chain found is not trusted, then OpenSSL will continue to check to see if an
203alternative chain can be found that is trusted. With this flag set the behaviour
204will match that of OpenSSL versions prior to 1.0.2b.
205
206The B<X509_V_FLAG_TRUSTED_FIRST> flag causes chain construction to look for
207issuers in the trust store before looking at the untrusted certificates
208provided as part of the the peer chain.
209Though it is not on by default in OpenSSL 1.0.2, applications should generally
210set this flag.
211Local issuer certificates are often more likely to satisfy local security
212requirements and lead to a locally trusted root.
213This is especially important When some certificates in the trust store have
214explicit trust settings (see "TRUST SETTINGS" in L<x509(1)>).
215
216The B<X509_V_FLAG_PARTIAL_CHAIN> flag causes intermediate certificates in the
217trust store to be treated as trust-anchors, in the same way as the self-signed
218root CA certificates.
219This makes it possible to trust certificates issued by an intermediate CA
220without having to trust its ancestor root CA.
221With OpenSSL 1.0.2, chain construction continues as long as there are
222additional trusted issuers in the trust store, and the last trusted issuer
223becomes the trust-anchor.
224Thus, even when an intermediate certificate is found in the trust store, the
225verified chain passed to callbacks may still be anchored by a root CA.
226
227=head1 NOTES
228
229The above functions should be used to manipulate verification parameters
230instead of legacy functions which work in specific structures such as
231X509_STORE_CTX_set_flags().
232
233=head1 BUGS
234
235Delta CRL checking is currently primitive. Only a single delta can be used and
236(partly due to limitations of B<X509_STORE>) constructed CRLs are not 
237maintained.
238
239If CRLs checking is enable CRLs are expected to be available in the
240corresponding B<X509_STORE> structure. No attempt is made to download
241CRLs from the CRL distribution points extension.
242
243=head1 EXAMPLE
244
245Enable CRL checking when performing certificate verification during SSL 
246connections associated with an B<SSL_CTX> structure B<ctx>:
247
248  X509_VERIFY_PARAM *param;
249  param = X509_VERIFY_PARAM_new();
250  X509_VERIFY_PARAM_set_flags(param, X509_V_FLAG_CRL_CHECK);
251  SSL_CTX_set1_param(ctx, param);
252  X509_VERIFY_PARAM_free(param);
253
254=head1 SEE ALSO
255
256L<X509_verify_cert(3)|X509_verify_cert(3)>,
257L<X509_check_host(3)|X509_check_host(3)>,
258L<X509_check_email(3)|X509_check_email(3)>,
259L<X509_check_ip(3)|X509_check_ip(3)>,
260L<x509(1)|x509(1)>
261
262=head1 HISTORY
263
264The B<X509_V_FLAG_NO_ALT_CHAINS> flag was added in OpenSSL 1.0.2b
265
266=cut
267