SSL/TLS: Certificate - Subject Common Name Does Not Match Server FQDN

# SPDX-FileCopyrightText: 2011 Greenbone AG
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.103141");
  script_version("2026-03-13T05:54:58+0000");
  script_tag(name:"last_modification", value:"2026-03-13 05:54:58 +0000 (Fri, 13 Mar 2026)");
  script_tag(name:"creation_date", value:"2011-04-27 15:13:59 +0200 (Wed, 27 Apr 2011)");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:N");
  script_tag(name:"cvss_base", value:"0.0");
  script_name("SSL/TLS: Certificate - Subject Common Name Does Not Match Server FQDN");
  script_category(ACT_GATHER_INFO);
  script_family("SSL and TLS");
  script_copyright("Copyright (C) 2011 Greenbone AG");
  script_dependencies("gb_ssl_tls_cert_details.nasl");
  script_mandatory_keys("ssl/cert/avail");

  script_tag(name:"summary", value:"The SSL/TLS certificate contains a common name (CN) that does not match the hostname.");

  script_tag(name:"qod_type", value:"remote_app");

  exit(0);
}

include("ssl_funcs.inc");
include("misc_func.inc");
include("list_array_func.inc");
include("byte_func.inc");
include("global_settings.inc");
include("host_details.inc");

# List of keys where the CN doesn't match the FQDN
problematic_keys = make_array();

hostname = get_host_name();
ip = get_host_ip();

if( hostname == ip ) exit( 0 );

# It makes no sense to report a wrong CN for localhost/127.0.0.1
if( hostname == "localhost" || ip == "127.0.0.1" ) exit( 0 );

sni_ctx = tls_get_sni_context_key();
ssls = get_kb_list( "HostDetails/SSLInfo/*/" + sni_ctx );
if( isnull( ssls ) )
  ssls = get_kb_list( "HostDetails/SSLInfo/*" );

if( ! isnull( ssls ) ) {

  foreach key( keys( ssls ) ) {

    tmp = split( key, sep:"/", keep:FALSE );
    port = tmp[2];
    vhost = tmp[3];

    fprlist = get_kb_item( key );
    if( ! fprlist ) continue;

    tmpfpr = split( fprlist, sep:",", keep:FALSE );
    fpr = tmpfpr[0];

    if( fpr[0] == "[" ) {
      debug_print( "A SSL/TLS certificate on port ", port, " (" + vhost + ")",
                   " is erroneous.", level:0 );
      continue;
    }

    key = "HostDetails/Cert/" + fpr + "/";

    hostnames = get_kb_item( key + "hostnames" );
    if( isnull( hostnames ) ) continue;

    hostnamelist = split( hostnames, sep:",", keep:FALSE );
    if( isnull( hostnamelist ) ) continue; # No hostname identified in cert

    if( ! in_array( search:hostname, array:hostnamelist ) ) {

      notVuln = FALSE;

      foreach tmphostname( hostnamelist ) {

        comname = tmphostname;

        if( comname[0] == "*" ) {
          hn = stridx( hostname, "." );
          in = stridx( tmphostname, "." );
          if( ( hn > 0 && in > 0 ) && substr( hostname, hn ) == substr( tmphostname, in ) ) {
            notVuln = TRUE;
            continue;
          }

          hn = comname - '*.';
          if( hn == hostname ) {
            notVuln = TRUE;
            continue;
          }
        }
      }
      if( ! notVuln ) problematic_keys[port] = key;
    }
  }

  foreach port( keys( problematic_keys ) ) {

    # nb:
    # - Store the reference from this one to gb_ssl_tls_cert_details.nasl to show a cross-reference
    #   within the reports
    # - We don't want to use get_app_* functions as we're only interested in the cross-reference here
    register_host_detail( name:"detected_by", value:"1.3.6.1.4.1.25623.1.0.103692" ); # gb_ssl_tls_cert_details.nasl
    register_host_detail( name:"detected_at", value:port + "/tcp" );

    report = 'The certificate of the remote service contains a common name (CN) that does not match the hostname "' + hostname + '".\n';
    report += cert_summary( key:problematic_keys[port] );
    log_message( data:report, port:port );
  }

  exit( 0 );
}

exit( 99 );