Finger Redirection Remote Denial of Service Vulnerability

# 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("1.3.6.1.4.1.25623.1.0.802231");
  script_version("2023-07-28T05:05:23+0000");
  script_tag(name:"last_modification", value:"2023-07-28 05:05:23 +0000 (Fri, 28 Jul 2023)");
  script_tag(name:"creation_date", value:"2011-08-10 13:49:51 +0200 (Wed, 10 Aug 2011)");
  script_cve_id("CVE-1999-0106");
  script_tag(name:"cvss_base", value:"2.1");
  script_tag(name:"cvss_base_vector", value:"AV:L/AC:L/Au:N/C:N/I:N/A:P");
  script_name("Finger Redirection Remote Denial of Service Vulnerability");
  script_category(ACT_ATTACK);
  script_copyright("Copyright (C) 2011 Greenbone AG");
  script_family("Denial of Service");
  script_dependencies("find_service.nasl", "find_service1.nasl", "find_service2.nasl");
  script_require_ports("Services/finger", 79);

  script_xref(name:"URL", value:"http://xforce.iss.net/xforce/xfdb/47");
  script_xref(name:"URL", value:"http://www.securityspace.com/smysecure/catid.html?id=10073");
  script_xref(name:"URL", value:"http://www.iss.net/security_center/reference/vuln/finger-bomb.htm");

  script_tag(name:"summary", value:"The finger service on the remote host is prone to a Denial of Service (DoS)
  vulnerability.");

  script_tag(name:"impact", value:"Successful exploitation will let the attacker to use this computer as a relay
  to gather information on a third-party network or cause a denial of service.");

  script_tag(name:"affected", value:"GNU finger is known to be affected. Other finger implementations might be
  affected as well.");

  script_tag(name:"insight", value:"The flaw exists because the finger daemon allows redirecting a finger request
  to remote sites using the form finger 'username@hostname1@hostname2'.");

  script_tag(name:"solution", value:"Update to GNU finger 1.37 or later.");

  script_tag(name:"solution_type", value:"VendorFix");
  script_tag(name:"qod_type", value:"remote_analysis");

  exit(0);
}

include("misc_func.inc");
include("port_service_func.inc");

port = service_get_port(default:79, proto:"finger");

host = get_host_name();

soc = open_sock_tcp(port);
if(!soc)
  exit(0);

banner = recv(socket:soc, length:2048, timeout:5);
if(banner) {
  close(soc);
  exit(0);
}

req = "root@" + host + "\r\n";

send(socket:soc, data:req);
res = recv(socket:soc, length:65535);
close(soc);
if(!res)
  exit(0);

res = tolower(res);
if(res && "such user" >!< res && "doesn't exist" >!< res &&
   "???" >!< res && "invalid" >!< res && "forward" >!< res) {
  security_message(port:port);
  exit(0);
}

exit(99);