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<title>X509_STORE_CTX_set_verify_cb</title>
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<ul id="index">
<li><a href="#NAME">NAME</a></li>
<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
<li><a href="#WARNINGS">WARNINGS</a></li>
<li><a href="#NOTES">NOTES</a></li>
<li><a href="#RETURN-VALUES">RETURN VALUES</a></li>
<li><a href="#EXAMPLES">EXAMPLES</a></li>
<li><a href="#SEE-ALSO">SEE ALSO</a></li>
<li><a href="#HISTORY">HISTORY</a></li>
<li><a href="#COPYRIGHT">COPYRIGHT</a></li>
</ul>
<h1 id="NAME">NAME</h1>
<p>X509_STORE_CTX_get_cleanup, X509_STORE_CTX_get_lookup_crls, X509_STORE_CTX_get_lookup_certs, X509_STORE_CTX_get_check_policy, X509_STORE_CTX_get_cert_crl, X509_STORE_CTX_get_check_crl, X509_STORE_CTX_get_get_crl, X509_STORE_CTX_get_check_revocation, X509_STORE_CTX_get_check_issued, X509_STORE_CTX_get_get_issuer, X509_STORE_CTX_get_verify_cb, X509_STORE_CTX_set_verify_cb, X509_STORE_CTX_verify_cb - get and set verification callback</p>
<h1 id="SYNOPSIS">SYNOPSIS</h1>
<pre><code> #include <openssl/x509_vfy.h>
typedef int (*X509_STORE_CTX_verify_cb)(int, X509_STORE_CTX *);
X509_STORE_CTX_verify_cb X509_STORE_CTX_get_verify_cb(X509_STORE_CTX *ctx);
void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
X509_STORE_CTX_verify_cb verify_cb);
X509_STORE_CTX_get_issuer_fn X509_STORE_CTX_get_get_issuer(X509_STORE_CTX *ctx);
X509_STORE_CTX_check_issued_fn X509_STORE_CTX_get_check_issued(X509_STORE_CTX *ctx);
X509_STORE_CTX_check_revocation_fn X509_STORE_CTX_get_check_revocation(X509_STORE_CTX *ctx);
X509_STORE_CTX_get_crl_fn X509_STORE_CTX_get_get_crl(X509_STORE_CTX *ctx);
X509_STORE_CTX_check_crl_fn X509_STORE_CTX_get_check_crl(X509_STORE_CTX *ctx);
X509_STORE_CTX_cert_crl_fn X509_STORE_CTX_get_cert_crl(X509_STORE_CTX *ctx);
X509_STORE_CTX_check_policy_fn X509_STORE_CTX_get_check_policy(X509_STORE_CTX *ctx);
X509_STORE_CTX_lookup_certs_fn X509_STORE_CTX_get_lookup_certs(X509_STORE_CTX *ctx);
X509_STORE_CTX_lookup_crls_fn X509_STORE_CTX_get_lookup_crls(X509_STORE_CTX *ctx);
X509_STORE_CTX_cleanup_fn X509_STORE_CTX_get_cleanup(X509_STORE_CTX *ctx);</code></pre>
<h1 id="DESCRIPTION">DESCRIPTION</h1>
<p>X509_STORE_CTX_set_verify_cb() sets the verification callback of <b>ctx</b> to <b>verify_cb</b> overwriting any existing callback.</p>
<p>The verification callback can be used to customise the operation of certificate verification, either by overriding error conditions or logging errors for debugging purposes.</p>
<p>However, a verification callback is <b>not</b> essential and the default operation is often sufficient.</p>
<p>The <b>ok</b> parameter to the callback indicates the value the callback should return to retain the default behaviour. If it is zero then an error condition is indicated. If it is 1 then no error occurred. If the flag <b>X509_V_FLAG_NOTIFY_POLICY</b> is set then <b>ok</b> is set to 2 to indicate the policy checking is complete.</p>
<p>The <b>ctx</b> parameter to the callback is the <b>X509_STORE_CTX</b> structure that is performing the verification operation. A callback can examine this structure and receive additional information about the error, for example by calling X509_STORE_CTX_get_current_cert(). Additional application data can be passed to the callback via the <b>ex_data</b> mechanism.</p>
<p>X509_STORE_CTX_get_verify_cb() returns the value of the current callback for the specific <b>ctx</b>.</p>
<p>X509_STORE_CTX_get_get_issuer(), X509_STORE_CTX_get_check_issued(), X509_STORE_CTX_get_check_revocation(), X509_STORE_CTX_get_get_crl(), X509_STORE_CTX_get_check_crl(), X509_STORE_CTX_get_cert_crl(), X509_STORE_CTX_get_check_policy(), X509_STORE_CTX_get_lookup_certs(), X509_STORE_CTX_get_lookup_crls() and X509_STORE_CTX_get_cleanup() return the function pointers cached from the corresponding <b>X509_STORE</b>, please see <a href="../man3/X509_STORE_set_verify.html">X509_STORE_set_verify(3)</a> for more information.</p>
<h1 id="WARNINGS">WARNINGS</h1>
<p>In general a verification callback should <b>NOT</b> unconditionally return 1 in all circumstances because this will allow verification to succeed no matter what the error. This effectively removes all security from the application because <b>any</b> certificate (including untrusted generated ones) will be accepted.</p>
<h1 id="NOTES">NOTES</h1>
<p>The verification callback can be set and inherited from the parent structure performing the operation. In some cases (such as S/MIME verification) the <b>X509_STORE_CTX</b> structure is created and destroyed internally and the only way to set a custom verification callback is by inheriting it from the associated <b>X509_STORE</b>.</p>
<h1 id="RETURN-VALUES">RETURN VALUES</h1>
<p>X509_STORE_CTX_set_verify_cb() does not return a value.</p>
<h1 id="EXAMPLES">EXAMPLES</h1>
<p>Default callback operation:</p>
<pre><code> int verify_callback(int ok, X509_STORE_CTX *ctx) {
return ok;
}</code></pre>
<p>Simple example, suppose a certificate in the chain is expired and we wish to continue after this error:</p>
<pre><code> int verify_callback(int ok, X509_STORE_CTX *ctx) {
/* Tolerate certificate expiration */
if (X509_STORE_CTX_get_error(ctx) == X509_V_ERR_CERT_HAS_EXPIRED)
return 1;
/* Otherwise don't override */
return ok;
}</code></pre>
<p>More complex example, we don't wish to continue after <b>any</b> certificate has expired just one specific case:</p>
<pre><code> int verify_callback(int ok, X509_STORE_CTX *ctx)
{
int err = X509_STORE_CTX_get_error(ctx);
X509 *err_cert = X509_STORE_CTX_get_current_cert(ctx);
if (err == X509_V_ERR_CERT_HAS_EXPIRED) {
if (check_is_acceptable_expired_cert(err_cert)
return 1;
}
return ok;
}</code></pre>
<p>Full featured logging callback. In this case the <b>bio_err</b> is assumed to be a global logging <b>BIO</b>, an alternative would to store a BIO in <b>ctx</b> using <b>ex_data</b>.</p>
<pre><code> int verify_callback(int ok, X509_STORE_CTX *ctx)
{
X509 *err_cert;
int err, depth;
err_cert = X509_STORE_CTX_get_current_cert(ctx);
err = X509_STORE_CTX_get_error(ctx);
depth = X509_STORE_CTX_get_error_depth(ctx);
BIO_printf(bio_err, "depth=%d ", depth);
if (err_cert) {
X509_NAME_print_ex(bio_err, X509_get_subject_name(err_cert),
0, XN_FLAG_ONELINE);
BIO_puts(bio_err, "\n");
}
else
BIO_puts(bio_err, "<no cert>\n");
if (!ok)
BIO_printf(bio_err, "verify error:num=%d:%s\n", err,
X509_verify_cert_error_string(err));
switch (err) {
case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
BIO_puts(bio_err, "issuer= ");
X509_NAME_print_ex(bio_err, X509_get_issuer_name(err_cert),
0, XN_FLAG_ONELINE);
BIO_puts(bio_err, "\n");
break;
case X509_V_ERR_CERT_NOT_YET_VALID:
case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:
BIO_printf(bio_err, "notBefore=");
ASN1_TIME_print(bio_err, X509_get_notBefore(err_cert));
BIO_printf(bio_err, "\n");
break;
case X509_V_ERR_CERT_HAS_EXPIRED:
case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
BIO_printf(bio_err, "notAfter=");
ASN1_TIME_print(bio_err, X509_get_notAfter(err_cert));
BIO_printf(bio_err, "\n");
break;
case X509_V_ERR_NO_EXPLICIT_POLICY:
policies_print(bio_err, ctx);
break;
}
if (err == X509_V_OK && ok == 2)
/* print out policies */
BIO_printf(bio_err, "verify return:%d\n", ok);
return(ok);
}</code></pre>
<h1 id="SEE-ALSO">SEE ALSO</h1>
<p><a href="../man3/X509_STORE_CTX_get_error.html">X509_STORE_CTX_get_error(3)</a> <a href="../man3/X509_STORE_set_verify_cb_func.html">X509_STORE_set_verify_cb_func(3)</a> <a href="../man3/X509_STORE_CTX_get_ex_new_index.html">X509_STORE_CTX_get_ex_new_index(3)</a></p>
<h1 id="HISTORY">HISTORY</h1>
<p>The X509_STORE_CTX_get_get_issuer(), X509_STORE_CTX_get_check_issued(), X509_STORE_CTX_get_check_revocation(), X509_STORE_CTX_get_get_crl(), X509_STORE_CTX_get_check_crl(), X509_STORE_CTX_get_cert_crl(), X509_STORE_CTX_get_check_policy(), X509_STORE_CTX_get_lookup_certs(), X509_STORE_CTX_get_lookup_crls() and X509_STORE_CTX_get_cleanup() functions were added in OpenSSL 1.1.0.</p>
<h1 id="COPYRIGHT">COPYRIGHT</h1>
<p>Copyright 2009-2020 The OpenSSL Project Authors. All Rights Reserved.</p>
<p>Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <a href="https://www.openssl.org/source/license.html">https://www.openssl.org/source/license.html</a>.</p>
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