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.
82The certificate 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_NO_FINGERPRINT>
88
89Failed to compute the internal SHA1 hash value of the certificate or CRL.
90This may be due to malloc failure or because no SHA1 implementation was found.
91
92=item B<EXFLAG_INVALID_POLICY>
93
94The NID_certificate_policies certificate extension is invalid or
95inconsistent. The certificate should be rejected.
96This bit may also be raised after an out-of-memory error while
97processing the X509 object, so it may not be related to the processed
98ASN1 object itself.
99
100=item B<EXFLAG_KUSAGE>
101
102The certificate contains a key usage extension. The value can be retrieved
103using X509_get_key_usage().
104
105=item B<EXFLAG_XKUSAGE>
106
107The certificate contains an extended key usage extension. The value can be
108retrieved using X509_get_extended_key_usage().
109
110=back
111
112X509_get_key_usage() returns the value of the key usage extension.  If key
113usage is present will return zero or more of the flags:
114B<KU_DIGITAL_SIGNATURE>, B<KU_NON_REPUDIATION>, B<KU_KEY_ENCIPHERMENT>,
115B<KU_DATA_ENCIPHERMENT>, B<KU_KEY_AGREEMENT>, B<KU_KEY_CERT_SIGN>,
116B<KU_CRL_SIGN>, B<KU_ENCIPHER_ONLY> or B<KU_DECIPHER_ONLY> corresponding to
117individual key usage bits. If key usage is absent then B<UINT32_MAX> is
118returned.
119
120X509_get_extended_key_usage() returns the value of the extended key usage
121extension. If extended key usage is present it will return zero or more of the
122flags: B<XKU_SSL_SERVER>, B<XKU_SSL_CLIENT>, B<XKU_SMIME>, B<XKU_CODE_SIGN>
123B<XKU_OCSP_SIGN>, B<XKU_TIMESTAMP>, B<XKU_DVCS> or B<XKU_ANYEKU>. These
124correspond to the OIDs B<id-kp-serverAuth>, B<id-kp-clientAuth>,
125B<id-kp-emailProtection>, B<id-kp-codeSigning>, B<id-kp-OCSPSigning>,
126B<id-kp-timeStamping>, B<id-kp-dvcs> and B<anyExtendedKeyUsage> respectively.
127Additionally B<XKU_SGC> is set if either Netscape or Microsoft SGC OIDs are
128present.
129
130X509_get0_subject_key_id() returns an internal pointer to the subject key
131identifier of B<x> as an B<ASN1_OCTET_STRING> or B<NULL> if the extension
132is not present or cannot be parsed.
133
134X509_get0_authority_key_id() returns an internal pointer to the authority key
135identifier of B<x> as an B<ASN1_OCTET_STRING> or B<NULL> if the extension
136is not present or cannot be parsed.
137
138X509_get0_authority_issuer() returns an internal pointer to the authority
139certificate issuer of B<x> as a stack of B<GENERAL_NAME> structures or
140B<NULL> if the extension is not present or cannot be parsed.
141
142X509_get0_authority_serial() returns an internal pointer to the authority
143certificate serial number of B<x> as an B<ASN1_INTEGER> or B<NULL> if the
144extension is not present or cannot be parsed.
145
146X509_set_proxy_flag() marks the certificate with the B<EXFLAG_PROXY> flag.
147This is for the users who need to mark non-RFC3820 proxy certificates as
148such, as OpenSSL only detects RFC3820 compliant ones.
149
150X509_set_proxy_pathlen() sets the proxy certificate path length for the given
151certificate B<x>.  This is for the users who need to mark non-RFC3820 proxy
152certificates as such, as OpenSSL only detects RFC3820 compliant ones.
153
154X509_get_proxy_pathlen() returns the proxy certificate path length for the
155given certificate B<x> if it is a proxy certificate.
156
157=head1 NOTES
158
159The value of the flags correspond to extension values which are cached
160in the B<X509> structure. If the flags returned do not provide sufficient
161information an application should examine extension values directly
162for example using X509_get_ext_d2i().
163
164If the key usage or extended key usage extension is absent then typically usage
165is unrestricted. For this reason X509_get_key_usage() and
166X509_get_extended_key_usage() return B<UINT32_MAX> when the corresponding
167extension is absent. Applications can additionally check the return value of
168X509_get_extension_flags() and take appropriate action is an extension is
169absent.
170
171If X509_get0_subject_key_id() returns B<NULL> then the extension may be
172absent or malformed. Applications can determine the precise reason using
173X509_get_ext_d2i().
174
175=head1 RETURN VALUES
176
177X509_get_pathlen() returns the path length value, or -1 if the extension
178is not present.
179
180X509_get_extension_flags(), X509_get_key_usage() and
181X509_get_extended_key_usage() return sets of flags corresponding to the
182certificate extension values.
183
184X509_get0_subject_key_id() returns the subject key identifier as a
185pointer to an B<ASN1_OCTET_STRING> structure or B<NULL> if the extension
186is absent or an error occurred during parsing.
187
188X509_get_proxy_pathlen() returns the path length value if the given
189certificate is a proxy one and has a path length set, and -1 otherwise.
190
191=head1 SEE ALSO
192
193L<X509_check_purpose(3)>
194
195=head1 HISTORY
196
197X509_get_pathlen(), X509_set_proxy_flag(), X509_set_proxy_pathlen() and
198X509_get_proxy_pathlen() were added in OpenSSL 1.1.0.
199
200=head1 COPYRIGHT
201
202Copyright 2015-2021 The OpenSSL Project Authors. All Rights Reserved.
203
204Licensed under the Apache License 2.0 (the "License").  You may not use
205this file except in compliance with the License.  You can obtain a copy
206in the file LICENSE in the source distribution or at
207L<https://www.openssl.org/source/license.html>.
208
209=cut
210