1=pod
2
3=head1 NAME
4
5X509_get0_subject_key_id,
6X509_get0_authority_key_id,
7X509_get0_authority_issuer,
8X509_get0_authority_serial,
9X509_get_pathlen,
10X509_get_extension_flags,
11X509_get_key_usage,
12X509_get_extended_key_usage,
13X509_set_proxy_flag,
14X509_set_proxy_pathlen,
15X509_get_proxy_pathlen - retrieve certificate extension data
16
17=head1 SYNOPSIS
18
19 #include <openssl/x509v3.h>
20
21 long X509_get_pathlen(X509 *x);
22 uint32_t X509_get_extension_flags(X509 *x);
23 uint32_t X509_get_key_usage(X509 *x);
24 uint32_t X509_get_extended_key_usage(X509 *x);
25 const ASN1_OCTET_STRING *X509_get0_subject_key_id(X509 *x);
26 const ASN1_OCTET_STRING *X509_get0_authority_key_id(X509 *x);
27 const GENERAL_NAMES *X509_get0_authority_issuer(X509 *x);
28 const ASN1_INTEGER *X509_get0_authority_serial(X509 *x);
29 void X509_set_proxy_flag(X509 *x);
30 void X509_set_proxy_pathlen(int l);
31 long X509_get_proxy_pathlen(X509 *x);
32
33=head1 DESCRIPTION
34
35These functions retrieve information related to commonly used certificate extensions.
36
37X509_get_pathlen() retrieves the path length extension from a certificate.
38This extension is used to limit the length of a cert chain that may be
39issued from that CA.
40
41X509_get_extension_flags() retrieves general information about a certificate,
42it will return one or more of the following flags ored together.
43
44=over 4
45
46=item B<EXFLAG_V1>
47
48The certificate is an obsolete version 1 certificate.
49
50=item B<EXFLAG_BCONS>
51
52The certificate contains a basic constraints extension.
53
54=item B<EXFLAG_CA>
55
56The certificate contains basic constraints and asserts the CA flag.
57
58=item B<EXFLAG_PROXY>
59
60The certificate is a valid proxy certificate.
61
62=item B<EXFLAG_SI>
63
64The certificate is self issued (that is subject and issuer names match).
65
66=item B<EXFLAG_SS>
67
68The subject and issuer names match and extension values imply it is self
69signed.
70
71=item B<EXFLAG_FRESHEST>
72
73The freshest CRL extension is present in the certificate.
74
75=item B<EXFLAG_CRITICAL>
76
77The certificate contains an unhandled critical extension.
78
79=item B<EXFLAG_INVALID>
80
81Some certificate extension values are invalid or inconsistent. The
82certificate should be rejected.
83This bit may also be raised after an out-of-memory error while
84processing the X509 object, so it may not be related to the processed
85ASN1 object itself.
86
87=item B<EXFLAG_INVALID_POLICY>
88
89The NID_certificate_policies certificate extension is invalid or
90inconsistent. The certificate should be rejected.
91This bit may also be raised after an out-of-memory error while
92processing the X509 object, so it may not be related to the processed
93ASN1 object itself.
94
95=item B<EXFLAG_KUSAGE>
96
97The certificate contains a key usage extension. The value can be retrieved
98using X509_get_key_usage().
99
100=item B<EXFLAG_XKUSAGE>
101
102The certificate contains an extended key usage extension. The value can be
103retrieved using X509_get_extended_key_usage().
104
105=back
106
107X509_get_key_usage() returns the value of the key usage extension.  If key
108usage is present will return zero or more of the flags:
109B<KU_DIGITAL_SIGNATURE>, B<KU_NON_REPUDIATION>, B<KU_KEY_ENCIPHERMENT>,
110B<KU_DATA_ENCIPHERMENT>, B<KU_KEY_AGREEMENT>, B<KU_KEY_CERT_SIGN>,
111B<KU_CRL_SIGN>, B<KU_ENCIPHER_ONLY> or B<KU_DECIPHER_ONLY> corresponding to
112individual key usage bits. If key usage is absent then B<UINT32_MAX> is
113returned.
114
115X509_get_extended_key_usage() returns the value of the extended key usage
116extension. If extended key usage is present it will return zero or more of the
117flags: B<XKU_SSL_SERVER>, B<XKU_SSL_CLIENT>, B<XKU_SMIME>, B<XKU_CODE_SIGN>
118B<XKU_OCSP_SIGN>, B<XKU_TIMESTAMP>, B<XKU_DVCS> or B<XKU_ANYEKU>. These
119correspond to the OIDs B<id-kp-serverAuth>, B<id-kp-clientAuth>,
120B<id-kp-emailProtection>, B<id-kp-codeSigning>, B<id-kp-OCSPSigning>,
121B<id-kp-timeStamping>, B<id-kp-dvcs> and B<anyExtendedKeyUsage> respectively.
122Additionally B<XKU_SGC> is set if either Netscape or Microsoft SGC OIDs are
123present.
124
125X509_get0_subject_key_id() returns an internal pointer to the subject key
126identifier of B<x> as an B<ASN1_OCTET_STRING> or B<NULL> if the extension
127is not present or cannot be parsed.
128
129X509_get0_authority_key_id() returns an internal pointer to the authority key
130identifier of B<x> as an B<ASN1_OCTET_STRING> or B<NULL> if the extension
131is not present or cannot be parsed.
132
133X509_get0_authority_issuer() returns an internal pointer to the authority
134certificate issuer of B<x> as a stack of B<GENERAL_NAME> structures or
135B<NULL> if the extension is not present or cannot be parsed.
136
137X509_get0_authority_serial() returns an internal pointer to the authority
138certificate serial number of B<x> as an B<ASN1_INTEGER> or B<NULL> if the
139extension is not present or cannot be parsed.
140
141X509_set_proxy_flag() marks the certificate with the B<EXFLAG_PROXY> flag.
142This is for the users who need to mark non-RFC3820 proxy certificates as
143such, as OpenSSL only detects RFC3820 compliant ones.
144
145X509_set_proxy_pathlen() sets the proxy certificate path length for the given
146certificate B<x>.  This is for the users who need to mark non-RFC3820 proxy
147certificates as such, as OpenSSL only detects RFC3820 compliant ones.
148
149X509_get_proxy_pathlen() returns the proxy certificate path length for the
150given certificate B<x> if it is a proxy certificate.
151
152=head1 NOTES
153
154The value of the flags correspond to extension values which are cached
155in the B<X509> structure. If the flags returned do not provide sufficient
156information an application should examine extension values directly
157for example using X509_get_ext_d2i().
158
159If the key usage or extended key usage extension is absent then typically usage
160is unrestricted. For this reason X509_get_key_usage() and
161X509_get_extended_key_usage() return B<UINT32_MAX> when the corresponding
162extension is absent. Applications can additionally check the return value of
163X509_get_extension_flags() and take appropriate action is an extension is
164absent.
165
166If X509_get0_subject_key_id() returns B<NULL> then the extension may be
167absent or malformed. Applications can determine the precise reason using
168X509_get_ext_d2i().
169
170=head1 RETURN VALUES
171
172X509_get_pathlen() returns the path length value, or -1 if the extension
173is not present.
174
175X509_get_extension_flags(), X509_get_key_usage() and
176X509_get_extended_key_usage() return sets of flags corresponding to the
177certificate extension values.
178
179X509_get0_subject_key_id() returns the subject key identifier as a
180pointer to an B<ASN1_OCTET_STRING> structure or B<NULL> if the extension
181is absent or an error occurred during parsing.
182
183X509_get_proxy_pathlen() returns the path length value if the given
184certificate is a proxy one and has a path length set, and -1 otherwise.
185
186=head1 SEE ALSO
187
188L<X509_check_purpose(3)>
189
190=head1 HISTORY
191
192X509_get_pathlen(), X509_set_proxy_flag(), X509_set_proxy_pathlen() and
193X509_get_proxy_pathlen() were added in OpenSSL 1.1.0.
194
195=head1 COPYRIGHT
196
197Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
198
199Licensed under the OpenSSL license (the "License").  You may not use
200this file except in compliance with the License.  You can obtain a copy
201in the file LICENSE in the source distribution or at
202L<https://www.openssl.org/source/license.html>.
203
204=cut
205