Updated: 2021/Apr/14


X509_STORE_CTX_set_verify_cb(3)     OpenSSL    X509_STORE_CTX_set_verify_cb(3)



NAME
       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

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #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);

DESCRIPTION
       X509_STORE_CTX_set_verify_cb() sets the verification callback of ctx to
       verify_cb overwriting any existing callback.

       The verification callback can be used to customise the operation of
       certificate verification, either by overriding error conditions or
       logging errors for debugging purposes.

       However, a verification callback is not essential and the default
       operation is often sufficient.

       The ok 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 X509_V_FLAG_NOTIFY_POLICY is set then ok is set to 2 to indicate
       the policy checking is complete.

       The ctx parameter to the callback is the X509_STORE_CTX 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 ex_data
       mechanism.

       X509_STORE_CTX_get_verify_cb() returns the value of the current
       callback for the specific ctx.

       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 X509_STORE,
       please see X509_STORE_set_verify(3) for more information.

WARNINGS
       In general a verification callback should NOT 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 any certificate (including untrusted generated
       ones) will be accepted.

NOTES
       The verification callback can be set and inherited from the parent
       structure performing the operation. In some cases (such as S/MIME
       verification) the X509_STORE_CTX structure is created and destroyed
       internally and the only way to set a custom verification callback is by
       inheriting it from the associated X509_STORE.

RETURN VALUES
       X509_STORE_CTX_set_verify_cb() does not return a value.

EXAMPLES
       Default callback operation:

        int verify_callback(int ok, X509_STORE_CTX *ctx) {
            return ok;
        }

       Simple example, suppose a certificate in the chain is expired and we
       wish to continue after this error:

        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;
        }

       More complex example, we don't wish to continue after any certificate
       has expired just one specific case:

        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;
        }

       Full featured logging callback. In this case the bio_err is assumed to
       be a global logging BIO, an alternative would to store a BIO in ctx
       using ex_data.

        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);
        }

SEE ALSO
       X509_STORE_CTX_get_error(3) X509_STORE_set_verify_cb_func(3)
       X509_STORE_CTX_get_ex_new_index(3)

HISTORY
       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.

COPYRIGHT
       Copyright 2009-2020 The OpenSSL Project Authors. All Rights Reserved.

       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
       <https://www.openssl.org/source/license.html>.



1.1.1i                            2020-12-10   X509_STORE_CTX_set_verify_cb(3)