---
name: "gnutls_x509_crt_check_hostname2"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_x509_crt_check_hostname2"
---

# gnutls\_x509\_crt\_check\_hostname2(3)

API function

## NAME

gnutls\_x509\_crt\_check\_hostname2 - API function

## SYNOPSIS

**#include \<gnutls/x509.h\>**

**unsigned gnutls\_x509\_crt\_check\_hostname2(gnutls\_x509\_crt\_t** *cert***, const char \*** *hostname***, unsigned int** *flags***);**

## ARGUMENTS

- gnutls\_x509\_crt\_t cert

  should contain an gnutls\_x509\_crt\_t type

- const char \* hostname

  A null terminated string that contains a DNS name

- unsigned int flags

  gnutls\_certificate\_verify\_flags

## DESCRIPTION

This function will check if the given certificate's subject matches the given hostname.  This is a basic implementation of the matching described in RFC6125, and takes into account wildcards, and the DNSName/IPAddress subject alternative name PKIX extension.

IPv4 addresses are accepted by this function in the dotted-decimal format (e.g, ddd.ddd.ddd.ddd), and IPv6 addresses in the hexadecimal x:x:x:x:x:x:x:x format. For them the IPAddress subject alternative name extension is consulted. Previous versions to 3.6.0 of GnuTLS in case of a non-match would consult (in a non-standard extension) the DNSname and CN fields. This is no longer the case.

When the flag **GNUTLS\_VERIFY\_DO\_NOT\_ALLOW\_WILDCARDS** is specified no wildcards are considered. Otherwise they are only considered if the domain name consists of three components or more, and the wildcard starts at the leftmost position. When the flag **GNUTLS\_VERIFY\_DO\_NOT\_ALLOW\_IP\_MATCHES** is specified, the input will be treated as a DNS name, and matching of textual IP addresses against the IPAddress part of the alternative name will not be allowed.

The function **gnutls\_x509\_crt\_check\_ip()** is available for matching IP addresses.

## RETURNS

non-zero for a successful match, and zero on failure.

## SINCE

3\.3.0

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 Free Software Foundation, Inc., and others.\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- https://www.gnutls.org/manual/