Update files for OpenSSL-1.0.0f import.
[dragonfly.git] / secure / lib / libcrypto / man / X509_STORE_CTX_set_verify_cb.3
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124.\" ========================================================================
125.\"
126.IX Title "X509_STORE_CTX_set_verify_cb 3"
e3261593 127.TH X509_STORE_CTX_set_verify_cb 3 "2012-01-04" "1.0.0f" "OpenSSL"
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128.\" For nroff, turn off justification. Always turn off hyphenation; it makes
129.\" way too many mistakes in technical documents.
130.if n .ad l
131.nh
132.SH "NAME"
133X509_STORE_CTX_set_verify_cb \- set verification callback
134.SH "SYNOPSIS"
135.IX Header "SYNOPSIS"
136.Vb 1
137\& #include <openssl/x509_vfy.h>
138\&
139\& void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
140\& int (*verify_cb)(int ok, X509_STORE_CTX *ctx));
141.Ve
142.SH "DESCRIPTION"
143.IX Header "DESCRIPTION"
144\&\fIX509_STORE_CTX_set_verify_cb()\fR sets the verification callback of \fBctx\fR to
145\&\fBverify_cb\fR overwriting any existing callback.
146.PP
147The verification callback can be used to customise the operation of certificate
148verification, either by overriding error conditions or logging errors for
149debugging purposes.
150.PP
151However a verification callback is \fBnot\fR essential and the default operation
152is often sufficient.
153.PP
154The \fBok\fR parameter to the callback indicates the value the callback should
155return to retain the default behaviour. If it is zero then and error condition
156is indicated. If it is 1 then no error occurred. If the flag
157\&\fBX509_V_FLAG_NOTIFY_POLICY\fR is set then \fBok\fR is set to 2 to indicate the
158policy checking is complete.
159.PP
160The \fBctx\fR parameter to the callback is the \fBX509_STORE_CTX\fR structure that
161is performing the verification operation. A callback can examine this
162structure and receive additional information about the error, for example
163by calling \fIX509_STORE_CTX_get_current_cert()\fR. Additional application data can
164be passed to the callback via the \fBex_data\fR mechanism.
165.SH "WARNING"
166.IX Header "WARNING"
167In general a verification callback should \fB\s-1NOT\s0\fR unconditionally return 1 in
168all circumstances because this will allow verification to succeed no matter
169what the error. This effectively removes all security from the application
170because \fBany\fR certificate (including untrusted generated ones) will be
171accepted.
172.SH "NOTES"
173.IX Header "NOTES"
174The verification callback can be set and inherited from the parent structure
175performing the operation. In some cases (such as S/MIME verification) the
176\&\fBX509_STORE_CTX\fR structure is created and destroyed internally and the
177only way to set a custom verification callback is by inheriting it from the
178associated \fBX509_STORE\fR.
179.SH "RETURN VALUES"
180.IX Header "RETURN VALUES"
181\&\fIX509_STORE_CTX_set_verify_cb()\fR does not return a value.
182.SH "EXAMPLES"
183.IX Header "EXAMPLES"
184Default callback operation:
185.PP
186.Vb 4
187\& int verify_callback(int ok, X509_STORE_CTX *ctx)
188\& {
189\& return ok;
190\& }
191.Ve
192.PP
193Simple example, suppose a certificate in the chain is expired and we wish
194to continue after this error:
195.PP
196.Vb 8
197\& int verify_callback(int ok, X509_STORE_CTX *ctx)
198\& {
199\& /* Tolerate certificate expiration */
200\& if (X509_STORE_CTX_get_error(ctx) == X509_V_ERR_CERT_HAS_EXPIRED)
201\& return 1;
202\& /* Otherwise don\*(Aqt override */
203\& return ok;
204\& }
205.Ve
206.PP
207More complex example, we don't wish to continue after \fBany\fR certificate has
208expired just one specific case:
209.PP
210.Vb 11
211\& int verify_callback(int ok, X509_STORE_CTX *ctx)
212\& {
213\& int err = X509_STORE_CTX_get_error(ctx);
214\& X509 *err_cert = X509_STORE_CTX_get_current_cert(ctx);
215\& if (err == X509_V_ERR_CERT_HAS_EXPIRED)
216\& {
217\& if (check_is_acceptable_expired_cert(err_cert)
218\& return 1;
219\& }
220\& return ok;
221\& }
222.Ve
223.PP
224Full featured logging callback. In this case the \fBbio_err\fR is assumed to be
225a global logging \fB\s-1BIO\s0\fR, an alternative would to store a \s-1BIO\s0 in \fBctx\fR using
226\&\fBex_data\fR.
227.PP
228.Vb 4
229\& int verify_callback(int ok, X509_STORE_CTX *ctx)
230\& {
231\& X509 *err_cert;
232\& int err,depth;
233\&
234\& err_cert = X509_STORE_CTX_get_current_cert(ctx);
235\& err = X509_STORE_CTX_get_error(ctx);
236\& depth = X509_STORE_CTX_get_error_depth(ctx);
237\&
238\& BIO_printf(bio_err,"depth=%d ",depth);
239\& if (err_cert)
240\& {
241\& X509_NAME_print_ex(bio_err, X509_get_subject_name(err_cert),
242\& 0, XN_FLAG_ONELINE);
243\& BIO_puts(bio_err, "\en");
244\& }
245\& else
246\& BIO_puts(bio_err, "<no cert>\en");
247\& if (!ok)
248\& BIO_printf(bio_err,"verify error:num=%d:%s\en",err,
249\& X509_verify_cert_error_string(err));
250\& switch (err)
251\& {
252\& case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
253\& BIO_puts(bio_err,"issuer= ");
254\& X509_NAME_print_ex(bio_err, X509_get_issuer_name(err_cert),
255\& 0, XN_FLAG_ONELINE);
256\& BIO_puts(bio_err, "\en");
257\& break;
258\& case X509_V_ERR_CERT_NOT_YET_VALID:
259\& case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:
260\& BIO_printf(bio_err,"notBefore=");
261\& ASN1_TIME_print(bio_err,X509_get_notBefore(err_cert));
262\& BIO_printf(bio_err,"\en");
263\& break;
264\& case X509_V_ERR_CERT_HAS_EXPIRED:
265\& case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
266\& BIO_printf(bio_err,"notAfter=");
267\& ASN1_TIME_print(bio_err,X509_get_notAfter(err_cert));
268\& BIO_printf(bio_err,"\en");
269\& break;
270\& case X509_V_ERR_NO_EXPLICIT_POLICY:
271\& policies_print(bio_err, ctx);
272\& break;
273\& }
274\& if (err == X509_V_OK && ok == 2)
275\& /* print out policies */
276\&
277\& BIO_printf(bio_err,"verify return:%d\en",ok);
278\& return(ok);
279\& }
280.Ve
281.SH "SEE ALSO"
282.IX Header "SEE ALSO"
283\&\fIX509_STORE_CTX_get_error\fR\|(3)
284\&\fIX509_STORE_set_verify_cb_func\fR\|(3)
285\&\fIX509_STORE_CTX_get_ex_new_index\fR\|(3)
286.SH "HISTORY"
287.IX Header "HISTORY"
288\&\fIX509_STORE_CTX_set_verify_cb()\fR is available in all versions of SSLeay and
289OpenSSL.