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a528d4f0a9
If something was "present in all versions" of SSLeay, or if it was added to a version of SSLeay (and therefore predates OpenSSL), remove mention of it. Documentation history now starts with OpenSSL. Remove mention of all history before OpenSSL 0.9.8, inclusive. Remove all AUTHOR sections. Reviewed-by: Tim Hudson <tjh@openssl.org>
157 lines
4.5 KiB
Plaintext
157 lines
4.5 KiB
Plaintext
=pod
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=head1 NAME
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X509_STORE_CTX_set_verify_cb - set verification callback
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=head1 SYNOPSIS
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#include <openssl/x509_vfy.h>
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void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
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int (*verify_cb)(int ok, X509_STORE_CTX *ctx));
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=head1 DESCRIPTION
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X509_STORE_CTX_set_verify_cb() sets the verification callback of B<ctx> to
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B<verify_cb> overwriting any existing callback.
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The verification callback can be used to customise the operation of certificate
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verification, either by overriding error conditions or logging errors for
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debugging purposes.
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However a verification callback is B<not> essential and the default operation
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is often sufficient.
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The B<ok> parameter to the callback indicates the value the callback should
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return to retain the default behaviour. If it is zero then and error condition
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is indicated. If it is 1 then no error occurred. If the flag
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B<X509_V_FLAG_NOTIFY_POLICY> is set then B<ok> is set to 2 to indicate the
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policy checking is complete.
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The B<ctx> parameter to the callback is the B<X509_STORE_CTX> structure that
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is performing the verification operation. A callback can examine this
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structure and receive additional information about the error, for example
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by calling X509_STORE_CTX_get_current_cert(). Additional application data can
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be passed to the callback via the B<ex_data> mechanism.
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=head1 WARNING
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In general a verification callback should B<NOT> unconditionally return 1 in
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all circumstances because this will allow verification to succeed no matter
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what the error. This effectively removes all security from the application
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because B<any> certificate (including untrusted generated ones) will be
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accepted.
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=head1 NOTES
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The verification callback can be set and inherited from the parent structure
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performing the operation. In some cases (such as S/MIME verification) the
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B<X509_STORE_CTX> structure is created and destroyed internally and the
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only way to set a custom verification callback is by inheriting it from the
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associated B<X509_STORE>.
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=head1 RETURN VALUES
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X509_STORE_CTX_set_verify_cb() does not return a value.
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=head1 EXAMPLES
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Default callback operation:
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int verify_callback(int ok, X509_STORE_CTX *ctx)
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{
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return ok;
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}
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Simple example, suppose a certificate in the chain is expired and we wish
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to continue after this error:
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int verify_callback(int ok, X509_STORE_CTX *ctx)
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{
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/* Tolerate certificate expiration */
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if (X509_STORE_CTX_get_error(ctx) == X509_V_ERR_CERT_HAS_EXPIRED)
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return 1;
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/* Otherwise don't override */
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return ok;
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}
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More complex example, we don't wish to continue after B<any> certificate has
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expired just one specific case:
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int verify_callback(int ok, X509_STORE_CTX *ctx)
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{
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int err = X509_STORE_CTX_get_error(ctx);
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X509 *err_cert = X509_STORE_CTX_get_current_cert(ctx);
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if (err == X509_V_ERR_CERT_HAS_EXPIRED)
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{
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if (check_is_acceptable_expired_cert(err_cert)
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return 1;
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}
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return ok;
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}
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Full featured logging callback. In this case the B<bio_err> is assumed to be
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a global logging B<BIO>, an alternative would to store a BIO in B<ctx> using
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B<ex_data>.
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int verify_callback(int ok, X509_STORE_CTX *ctx)
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{
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X509 *err_cert;
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int err,depth;
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err_cert = X509_STORE_CTX_get_current_cert(ctx);
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err = X509_STORE_CTX_get_error(ctx);
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depth = X509_STORE_CTX_get_error_depth(ctx);
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BIO_printf(bio_err,"depth=%d ",depth);
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if (err_cert)
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{
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X509_NAME_print_ex(bio_err, X509_get_subject_name(err_cert),
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0, XN_FLAG_ONELINE);
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BIO_puts(bio_err, "\n");
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}
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else
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BIO_puts(bio_err, "<no cert>\n");
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if (!ok)
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BIO_printf(bio_err,"verify error:num=%d:%s\n",err,
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X509_verify_cert_error_string(err));
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switch (err)
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{
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case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
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BIO_puts(bio_err,"issuer= ");
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X509_NAME_print_ex(bio_err, X509_get_issuer_name(err_cert),
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0, XN_FLAG_ONELINE);
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BIO_puts(bio_err, "\n");
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break;
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case X509_V_ERR_CERT_NOT_YET_VALID:
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case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:
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BIO_printf(bio_err,"notBefore=");
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ASN1_TIME_print(bio_err,X509_get_notBefore(err_cert));
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BIO_printf(bio_err,"\n");
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break;
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case X509_V_ERR_CERT_HAS_EXPIRED:
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case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
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BIO_printf(bio_err,"notAfter=");
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ASN1_TIME_print(bio_err,X509_get_notAfter(err_cert));
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BIO_printf(bio_err,"\n");
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break;
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case X509_V_ERR_NO_EXPLICIT_POLICY:
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policies_print(bio_err, ctx);
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break;
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}
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if (err == X509_V_OK && ok == 2)
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/* print out policies */
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BIO_printf(bio_err,"verify return:%d\n",ok);
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return(ok);
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}
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=head1 SEE ALSO
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L<X509_STORE_CTX_get_error(3)>
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L<X509_STORE_set_verify_cb_func(3)>
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L<X509_STORE_CTX_get_ex_new_index(3)>
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=cut
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