DOC HOME SITE MAP MAN PAGES GNU INFO SEARCH PRINT BOOK
 

X509_STORE_CTX_set_verify_cb(3)





X509_STORE_CTX_set_verify_cb(3OpenSSX509_STORE_CTX_set_verify_cb(3)



NAME

     X509_STORE_CTX_set_verify_cb - set verification callback


SYNOPSIS

      #include <openssl/x509_vfy.h>

      void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
                                     int (*verify_cb)(int ok, 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 and 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.


WARNING

     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.

1.0.2t               Last change: 2019-09-10                    1


X509_STORE_CTX_set_verify_cb(3OpenSSX509_STORE_CTX_set_verify_cb(3)



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);

1.0.2t               Last change: 2019-09-10                    2


X509_STORE_CTX_set_verify_cb(3OpenSSX509_STORE_CTX_set_verify_cb(3)


             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

     X509_STORE_CTX_set_verify_cb() is available in all versions
     of SSLeay and OpenSSL.

1.0.2t               Last change: 2019-09-10                    3


Man(1) output converted with man2html