1=pod
2
3=head1 NAME
4
5X509_STORE_CTX_get_cleanup,
6X509_STORE_CTX_get_lookup_crls,
7X509_STORE_CTX_get_lookup_certs,
8X509_STORE_CTX_get_check_policy,
9X509_STORE_CTX_get_cert_crl,
10X509_STORE_CTX_get_check_crl,
11X509_STORE_CTX_get_get_crl,
12X509_STORE_CTX_set_get_crl,
13X509_STORE_CTX_get_check_revocation,
14X509_STORE_CTX_get_check_issued,
15X509_STORE_CTX_get_get_issuer,
16X509_STORE_CTX_get_verify_cb,
17X509_STORE_CTX_set_verify_cb,
18X509_STORE_CTX_verify_cb,
19X509_STORE_CTX_print_verify_cb,
20X509_STORE_CTX_set_current_reasons
21- get and set X509_STORE_CTX components such as verification callback
22
23=head1 SYNOPSIS
24
25 #include <openssl/x509_vfy.h>
26
27 typedef int (*X509_STORE_CTX_verify_cb)(int, X509_STORE_CTX *);
28 int X509_STORE_CTX_print_verify_cb(int ok, X509_STORE_CTX *ctx);
29
30 X509_STORE_CTX_verify_cb X509_STORE_CTX_get_verify_cb(X509_STORE_CTX *ctx);
31
32 void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
33                                   X509_STORE_CTX_verify_cb verify_cb);
34
35 X509_STORE_CTX_get_issuer_fn X509_STORE_CTX_get_get_issuer(X509_STORE_CTX *ctx);
36 X509_STORE_CTX_check_issued_fn X509_STORE_CTX_get_check_issued(X509_STORE_CTX *ctx);
37 X509_STORE_CTX_check_revocation_fn X509_STORE_CTX_get_check_revocation(X509_STORE_CTX *ctx);
38
39 X509_STORE_CTX_get_crl_fn X509_STORE_CTX_get_get_crl(X509_STORE_CTX *ctx);
40
41 void X509_STORE_CTX_set_get_crl(X509_STORE_CTX *ctx,
42                                 X509_STORE_CTX_get_crl_fn get_crl);
43
44 X509_STORE_CTX_check_crl_fn X509_STORE_CTX_get_check_crl(X509_STORE_CTX *ctx);
45 X509_STORE_CTX_cert_crl_fn X509_STORE_CTX_get_cert_crl(X509_STORE_CTX *ctx);
46 X509_STORE_CTX_check_policy_fn X509_STORE_CTX_get_check_policy(X509_STORE_CTX *ctx);
47 X509_STORE_CTX_lookup_certs_fn X509_STORE_CTX_get_lookup_certs(X509_STORE_CTX *ctx);
48 X509_STORE_CTX_lookup_crls_fn X509_STORE_CTX_get_lookup_crls(X509_STORE_CTX *ctx);
49 X509_STORE_CTX_cleanup_fn X509_STORE_CTX_get_cleanup(X509_STORE_CTX *ctx);
50 void X509_STORE_CTX_set_current_reasons(X509_STORE_CTX *ctx,
51                                         unsigned int current_reasons);
52
53=head1 DESCRIPTION
54
55X509_STORE_CTX_set_verify_cb() sets the verification callback of B<ctx> to
56B<verify_cb> overwriting any existing callback.
57
58The verification callback can be used to customise the operation of certificate
59verification, for instance by overriding error conditions or logging errors for
60debugging purposes.
61
62However, a verification callback is B<not> essential and the default operation
63is often sufficient.
64
65The B<ok> parameter to the callback indicates the value the callback should
66return to retain the default behaviour. If it is zero then an error condition
67is indicated. If it is 1 then no error occurred. If the flag
68B<X509_V_FLAG_NOTIFY_POLICY> is set then B<ok> is set to 2 to indicate the
69policy checking is complete.
70
71The B<ctx> parameter to the callback is the B<X509_STORE_CTX> structure that
72is performing the verification operation. A callback can examine this
73structure and receive additional information about the error, for example
74by calling X509_STORE_CTX_get_current_cert(). Additional application data can
75be passed to the callback via the B<ex_data> mechanism.
76
77X509_STORE_CTX_print_verify_cb() is a verification callback function that,
78when a certificate verification has failed, adds an entry to the error queue
79with code B<X509_R_CERTIFICATE_VERIFICATION_FAILED> and with diagnostic details,
80including the most relevant fields of the target certificate that failed to
81verify and, if appropriate, of the available untrusted and trusted certificates.
82
83X509_STORE_CTX_get_verify_cb() returns the value of the current callback
84for the specific B<ctx>.
85
86X509_STORE_CTX_get_get_issuer(),
87X509_STORE_CTX_get_check_issued(), X509_STORE_CTX_get_check_revocation(),
88X509_STORE_CTX_get_get_crl(), X509_STORE_CTX_get_check_crl(),
89X509_STORE_CTX_get_cert_crl(), X509_STORE_CTX_get_check_policy(),
90X509_STORE_CTX_get_lookup_certs(), X509_STORE_CTX_get_lookup_crls()
91and X509_STORE_CTX_get_cleanup() return the function pointers cached
92from the corresponding B<X509_STORE>, please see
93L<X509_STORE_set_verify(3)> for more information.
94
95X509_STORE_CTX_set_get_crl() sets the function to get the crl for a given
96certificate I<x>.
97When found, the crl must be assigned to I<*crl>.
98This function must return 0 on failure and 1 on success.
99I<If no function to get the issuer is provided, the internal default
100function will be used instead.>
101
102X509_STORE_CTX_set_current_reasons() is used in conjunction with
103X509_STORE_CTX_get_crl_fn. The X509_STORE_CTX_get_crl_fn callback must
104use this method to set the reason why the certificate is invalid.
105
106
107=head1 WARNINGS
108
109In general a verification callback should B<NOT> unconditionally return 1 in
110all circumstances because this will allow verification to succeed no matter
111what the error. This effectively removes all security from the application
112because B<any> certificate (including untrusted generated ones) will be
113accepted.
114
115=head1 NOTES
116
117The verification callback can be set and inherited from the parent structure
118performing the operation. In some cases (such as S/MIME verification) the
119B<X509_STORE_CTX> structure is created and destroyed internally and the
120only way to set a custom verification callback is by inheriting it from the
121associated B<X509_STORE>.
122
123=head1 RETURN VALUES
124
125X509_STORE_CTX_set_verify_cb() does not return a value.
126
127=head1 EXAMPLES
128
129Default callback operation:
130
131 int verify_callback(int ok, X509_STORE_CTX *ctx) {
132     return ok;
133 }
134
135Simple example, suppose a certificate in the chain is expired and we wish
136to continue after this error:
137
138 int verify_callback(int ok, X509_STORE_CTX *ctx) {
139     /* Tolerate certificate expiration */
140     if (X509_STORE_CTX_get_error(ctx) == X509_V_ERR_CERT_HAS_EXPIRED)
141         return 1;
142     /* Otherwise don't override */
143     return ok;
144 }
145
146More complex example, we don't wish to continue after B<any> certificate has
147expired just one specific case:
148
149 int verify_callback(int ok, X509_STORE_CTX *ctx)
150 {
151     int err = X509_STORE_CTX_get_error(ctx);
152     X509 *err_cert = X509_STORE_CTX_get_current_cert(ctx);
153
154     if (err == X509_V_ERR_CERT_HAS_EXPIRED) {
155         if (check_is_acceptable_expired_cert(err_cert)
156             return 1;
157     }
158     return ok;
159 }
160
161Full featured logging callback. In this case the B<bio_err> is assumed to be
162a global logging B<BIO>, an alternative would to store a BIO in B<ctx> using
163B<ex_data>.
164
165 int verify_callback(int ok, X509_STORE_CTX *ctx)
166 {
167     X509 *err_cert;
168     int err, depth;
169
170     err_cert = X509_STORE_CTX_get_current_cert(ctx);
171     err = X509_STORE_CTX_get_error(ctx);
172     depth = X509_STORE_CTX_get_error_depth(ctx);
173
174     BIO_printf(bio_err, "depth=%d ", depth);
175     if (err_cert) {
176         X509_NAME_print_ex(bio_err, X509_get_subject_name(err_cert),
177                            0, XN_FLAG_ONELINE);
178         BIO_puts(bio_err, "\n");
179     }
180     else
181         BIO_puts(bio_err, "<no cert>\n");
182     if (!ok)
183         BIO_printf(bio_err, "verify error:num=%d:%s\n", err,
184                    X509_verify_cert_error_string(err));
185     switch (err) {
186     case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
187         BIO_puts(bio_err, "issuer= ");
188         X509_NAME_print_ex(bio_err, X509_get_issuer_name(err_cert),
189                            0, XN_FLAG_ONELINE);
190         BIO_puts(bio_err, "\n");
191         break;
192     case X509_V_ERR_CERT_NOT_YET_VALID:
193     case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:
194         BIO_printf(bio_err, "notBefore=");
195         ASN1_TIME_print(bio_err, X509_get_notBefore(err_cert));
196         BIO_printf(bio_err, "\n");
197         break;
198     case X509_V_ERR_CERT_HAS_EXPIRED:
199     case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
200         BIO_printf(bio_err, "notAfter=");
201         ASN1_TIME_print(bio_err, X509_get_notAfter(err_cert));
202         BIO_printf(bio_err, "\n");
203         break;
204     case X509_V_ERR_NO_EXPLICIT_POLICY:
205         policies_print(bio_err, ctx);
206         break;
207     }
208     if (err == X509_V_OK && ok == 2)
209         /* print out policies */
210
211     BIO_printf(bio_err, "verify return:%d\n", ok);
212     return(ok);
213 }
214
215=head1 SEE ALSO
216
217L<X509_STORE_CTX_get_error(3)>
218L<X509_STORE_set_verify_cb_func(3)>
219L<X509_STORE_CTX_get_ex_new_index(3)>
220
221=head1 HISTORY
222
223The
224X509_STORE_CTX_get_get_issuer(),
225X509_STORE_CTX_get_check_issued(), X509_STORE_CTX_get_check_revocation(),
226X509_STORE_CTX_get_get_crl(), X509_STORE_CTX_get_check_crl(),
227X509_STORE_CTX_get_cert_crl(), X509_STORE_CTX_get_check_policy(),
228X509_STORE_CTX_get_lookup_certs(), X509_STORE_CTX_get_lookup_crls()
229and X509_STORE_CTX_get_cleanup() functions were added in OpenSSL 1.1.0.
230
231X509_STORE_CTX_print_verify_cb() was added in OpenSSL 3.0.
232
233=head1 COPYRIGHT
234
235Copyright 2009-2023 The OpenSSL Project Authors. All Rights Reserved.
236
237Licensed under the Apache License 2.0 (the "License").  You may not use
238this file except in compliance with the License.  You can obtain a copy
239in the file LICENSE in the source distribution or at
240L<https://www.openssl.org/source/license.html>.
241
242=cut
243