Xen Hypervisor Infinite Loop Guest-to-Host DoS (XSA-246)

#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(104898);
  script_version("1.7");
  script_set_attribute(attribute:"plugin_modification_date", value:"2021/06/03");

  script_cve_id("CVE-2017-17044");
  script_xref(name:"IAVB", value:"2017-B-0165-S");

  script_name(english:"Xen Hypervisor Infinite Loop Guest-to-Host DoS (XSA-246)");
  script_summary(english:"Checks 'xl info' output for the Xen hypervisor version.");

  script_set_attribute(attribute:"synopsis", value:
"The remote Xen hypervisor installation is missing a security update.");
  script_set_attribute(attribute:"description", value:
"According to its self-reported version number, the Xen hypervisor
installed on the remote host is affected by an infinite loop
guest-to-host denial of service vulnerability.

This issue only affects x86  systems that have 2MiB or 1GiB HAP pages
enabled. ARM systems are not affected. x86 PV VMs can not trigger
this vulnerability.

Note that Nessus has checked the changeset versions based on the
xen.git change log. Nessus did not check guest hardware configurations
or if patches were applied manually to the source code before a
recompile and reinstall.");
  script_set_attribute(attribute:"see_also", value:"https://xenbits.xen.org/xsa/advisory-246.html");
  script_set_attribute(attribute:"see_also", value:"https://xenbits.xen.org/gitweb/?p=xen.git;a=summary");
  script_set_attribute(attribute:"solution", value:
"Apply the appropriate patch according to the vendor advisory.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:N/I:N/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2017-17044");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/11/28");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/11/28");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/11/30");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:xen:xen");
  script_set_attribute(attribute:"stig_severity", value:"I");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2017-2021 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("xen_server_detect.nbin");
  script_require_keys("installed_sw/Xen Hypervisor", "Settings/ParanoidReport");

  exit(0);
}

include("audit.inc");
include("global_settings.inc");
include("install_func.inc");
include("misc_func.inc");

app_name = "Xen Hypervisor";
install  = get_single_install(app_name:app_name);
if (report_paranoia < 2) audit(AUDIT_PARANOID);

version         = install['version'];
display_version = install['display_version'];
path            = install['path'];
managed_status  = install['Managed status'];
changeset       = install['Changeset'];

if (!empty_or_null(changeset))
  display_version += " (changeset " + changeset + ")";

# Installations that are vendor-managed are handled by OS-specific local package checks
if (managed_status == "managed")
  audit(AUDIT_INST_PATH_NOT_VULN, app_name, display_version, path);

# XSA-246
fixes['4.5']['fixed_ver']           = '4.5.5';
fixes['4.5']['fixed_ver_display']   = '4.5.5 (changeset d144bda)';
fixes['4.5']['affected_ver_regex']  = '^4\\.5\\.';
fixes['4.5']['affected_changesets'] = make_list("41f6dd0", "b0be3c2",
  "42ea1dc", "08aa260", "03b06d3", "77666b6", "bbeb763", "5fdf16f",
  "0e9967d", "da4f24d", "b7582ac", "196371c", "7afc8ad", "72c107b",
  "5659aa5", "a224de6", "6442fa9", "db487a6", "709230f", "83724d9",
  "04b8c4c", "0b2ceae", "e3f0768", "d5a5231", "c5b0fe5", "136ff4e",
  "42c8ba5", "d38489d", "df59014", "3217129", "4964e86", "c079597",
  "6ec173b", "a373456", "0780e81", "e5ef76d", "25eaa86", "ae02360",
  "5597df9", "c5de05e", "773094e", "e39a248", "7b3712a", "be35327",
  "8825df1", "d7e3725", "6eb61e4", "b1fcfed", "5779d6a", "afdd77e",
  "c18367a", "7b7fd80", "b30e165", "62ef9b2", "8071724", "235b5d5",
  "a28b99d", "ff294fc", "bc01e2d", "da50922", "386cc94", "139960f",
  "ec3ddd6", "988929a", "1c48dff", "20d4248", "9610422", "cd76cd3",
  "455fd66", "b820c31", "ac3d8bc", "cde86fc", "1678521", "83cb2db",
  "43d06ef", "2b17bf4", "1a2bda5", "0bd7faf", "e3426e2", "37281bc",
  "27be856", "bdf3ef1", "cc325c0", "8e7b84d", "387b8ae", "34fbae7",
  "1530da2", "274a1f6", "b679cfa", "877b760", "cfe165d", "84e4e56", "e4ae4b0");

fixes['4.7']['fixed_ver']           = '4.7.5';
fixes['4.7']['fixed_ver_display']   = '4.7.5-pre (changeset 67966a9)';
fixes['4.7']['affected_ver_regex']  = '^4\\.7\\.';
fixes['4.7']['affected_changesets'] = make_list("af3f585");

fixes['4.9']['fixed_ver']           = '4.9.2';
fixes['4.9']['fixed_ver_display']   = '4.9.2-pre (changeset 61c13ed)';
fixes['4.9']['affected_ver_regex']  = '^4\\.9\\.';
fixes['4.9']['affected_changesets'] = make_list("52ad651");

fix = NULL;
foreach ver_branch (keys(fixes))
{
  if (version =~ fixes[ver_branch]['affected_ver_regex'])
  {
    ret = ver_compare(ver:version, fix:fixes[ver_branch]['fixed_ver']);
    if (ret < 0)
      fix = fixes[ver_branch]['fixed_ver_display'];
    else if (ret == 0)
    {
      if (empty_or_null(changeset))
        fix = fixes[ver_branch]['fixed_ver_display'];
      else
        foreach affected_changeset (fixes[ver_branch]['affected_changesets'])
          if (changeset == affected_changeset)
            fix = fixes[ver_branch]['fixed_ver_display'];

    }

  }

}

if (empty_or_null(fix))
  audit(AUDIT_INST_PATH_NOT_VULN, app_name, display_version, path);

items  = make_array("Installed version", display_version,
                    "Fixed version", fix,
                    "Path", path);
order  = make_list("Path", "Installed version", "Fixed version");
report = report_items_str(report_items:items, ordered_fields:order) + '\n';

security_report_v4(port:0, extra:report, severity:SECURITY_WARNING);