Xen Hypervisor New CPU Interrupt Descriptor Table (IDT) Copy Handling Guest-to-Host Privilege Escalation (XSA-244)

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

include("compat.inc");

if (description)
{
  script_id(103979);
  script_version("1.7");
  script_set_attribute(attribute:"plugin_modification_date", value:"2021/06/03");

  script_cve_id(
    "CVE-2017-15588",
    "CVE-2017-15589",
    "CVE-2017-15590",
    "CVE-2017-15591",
    "CVE-2017-15592",
    "CVE-2017-15593",
    "CVE-2017-15594",
    "CVE-2017-15595",
    "CVE-2017-15596"
  );
  script_bugtraq_id(101490, 101496, 101500);
  script_xref(name:"IAVB", value:"2017-B-0142-S");

  script_name(english:"Xen Hypervisor New CPU Interrupt Descriptor Table (IDT) Copy Handling Guest-to-Host Privilege Escalation (XSA-244)");
  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 unspecified flaw that
is triggered when, as a new CPU is brought online, it copies certain
selector fields from CPU0's Interrupt Descriptor Table (IDT) while
CPU0 is in HVM context. This may result in incorrect values being
copied, allowing an attacker on the guest to cause a denial of
service or gain elevated privileges on the host.

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:"http://xenbits.xen.org/xsa/advisory-244.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:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2017-15595");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2017/10/12");
  script_set_attribute(attribute:"patch_publication_date", value:"2017/10/12");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/10/19");

  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-244
fixes['4.5']['fixed_ver']           = '4.5.5';
fixes['4.5']['fixed_ver_display']   = '4.5.5 (changeset 77666b6)';
fixes['4.5']['affected_ver_regex']  = '^4\\.5\\.';
fixes['4.5']['affected_changesets'] = make_list("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['4.6']['fixed_ver']           = '4.6.6';
fixes['4.6']['fixed_ver_display']   = '4.6.6 (changeset aad5a67)';
fixes['4.6']['affected_ver_regex']  = '^4\\.6\\.';
fixes['4.6']['affected_changesets'] = make_list("d8b0ebf", "f0208a4",
  "42b2c82", "57318e1", "9f22d72", "e0353b4", "76f1549", "9bac910",
  "c7a43e3", "913d4f8", "c5881c5", "b0239cd", "78fd0c3", "9079e0d",
  "1658a87", "22b6dfa", "a8cd231", "629eddd", "64c03bb", "b4660b4",
  "1ac8162", "747df3c", "5ae011e", "f974d32", "3300ad3", "d708b69");

fixes['4.7']['fixed_ver']           = '4.7.4';
fixes['4.7']['fixed_ver_display']   = '4.7.4-pre (changeset c10dc54)';
fixes['4.7']['affected_ver_regex']  = '^4\\.7\\.';
fixes['4.7']['affected_changesets'] = make_list("8cd1258", "1d01ddc",
  "5ca7d11", "ebd47d4", "6a6a339", "e61be54", "e3f7a64", "957ad23",
  "b1ae705", "3add76f", "314a8fc", "d6aad63", "7c99633", "145c18d",
  "c3fa5cd", "487f8f9", "ffcfc40", "c7783d9", "3331050", "83966a3",
  "a67b223", "68dbba2", "2728470", "dea68ed", "9d12253", "73d7bc5",
  "b704b1a", "ca4ef7b", "ece330a", "3d63ebc", "30d50f8", "2dc3cdb",
  "5151257", "c9f3ca0", "e873251", "8aebf85", "c362cde", "fece08a");

fixes['4.8']['fixed_ver']           = '4.8.3';
fixes['4.8']['fixed_ver_display']   = '4.8.3-pre (changeset bdc2ae6)';
fixes['4.8']['affected_ver_regex']  = '^4\\.8\\.';
fixes['4.8']['affected_changesets'] = make_list("96e6364", "1a8ad09",
  "df89197", "c4f969d", "b1f3f1d", "7251c06", "1960ca8", "866cfa1",
  "ddd6e41", "370cc9a", "39e3024", "9f092f5", "667f70e", "2116fec",
  "1a535c3", "ee3fc24", "d623d82", "dda458c", "c642b12", "80d7ef3",
  "ff4f60a", "36898eb", "4d7ccae", "e574046", "90dafa4", "c020cf2");

fixes['4.9']['fixed_ver']           = '4.9.1';
fixes['4.9']['fixed_ver_display']   = '4.9.1-pre (changeset de38e28)';
fixes['4.9']['affected_ver_regex']  = '^4\\.9\\.';
fixes['4.9']['affected_changesets'] = make_list("7fe0a24", "a2af47d",
  "61a2d31", "c2b0a92", "d842630", "ef61bcf", "44ceb19", "ae45442",
  "784afd9", "22032b2", "58da67f", "d1b64cc", "9cde7a8", "1cdcb36",
  "84c039e", "b244ac9", "612044a", "e8fd372", "a568e25", "8fef83e",
  "478e40c", "22ea731", "e7703a2", "91ded3b", "2cc3d32", "79775f5",
  "43cb0c4", "4821228", "d23bcc5", "308654c", "6fd84b3", "89b36cc",
  "a9ecd60", "798f6c9", "6508278", "5587d9a", "527fc5c", "5ff1de3",
  "692ed82", "9bf14bb", "c57b1f9", "6b147fd", "0e186e3", "afc5ebf",
  "266fc0e", "4698106", "f4f02f1", "0fada05", "ab4eb6c", "b29ecc7",
  "a11d14b", "107401e", "1b7834a");

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_HOLE);