Index: openssl/doc/crypto/X509_STORE_CTX_set_verify_cb.pod |
=================================================================== |
--- openssl/doc/crypto/X509_STORE_CTX_set_verify_cb.pod (revision 0) |
+++ openssl/doc/crypto/X509_STORE_CTX_set_verify_cb.pod (revision 0) |
@@ -0,0 +1,161 @@ |
+=pod |
+ |
+=head1 NAME |
+ |
+X509_STORE_CTX_set_verify_cb - set verification callback |
+ |
+=head1 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)); |
+ |
+=head1 DESCRIPTION |
+ |
+X509_STORE_CTX_set_verify_cb() sets the verification callback of B<ctx> to |
+B<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 B<not> essential and the default operation |
+is often sufficient. |
+ |
+The B<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 |
+B<X509_V_FLAG_NOTIFY_POLICY> is set then B<ok> is set to 2 to indicate the |
+policy checking is complete. |
+ |
+The B<ctx> parameter to the callback is the B<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 B<ex_data> mechanism. |
+ |
+=head1 WARNING |
+ |
+In general a verification callback should B<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 B<any> certificate (including untrusted generated ones) will be |
+accepted. |
+ |
+=head1 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 |
+B<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 B<X509_STORE>. |
+ |
+=head1 RETURN VALUES |
+ |
+X509_STORE_CTX_set_verify_cb() does not return a value. |
+ |
+=head1 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 B<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 B<bio_err> is assumed to be |
+a global logging B<BIO>, an alternative would to store a BIO in B<ctx> using |
+B<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); |
+ } |
+ |
+=head1 SEE ALSO |
+ |
+L<X509_STORE_CTX_get_error(3)|X509_STORE_CTX_get_error(3)> |
+L<X509_STORE_set_verify_cb_func(3)|X509_STORE_set_verify_cb_func(3)> |
+L<X509_STORE_CTX_get_ex_new_index(3)|X509_STORE_CTX_get_ex_new_index(3)> |
+ |
+=head1 HISTORY |
+ |
+X509_STORE_CTX_set_verify_cb() is available in all versions of SSLeay and |
+OpenSSL. |
+ |
+=cut |