Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel vulnerabilities (USN-4887-1)

##
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Ubuntu Security Notice USN-4887-1. The text
# itself is copyright (C) Canonical, Inc. See
# <https://ubuntu.com/security/notices>. Ubuntu(R) is a registered
# trademark of Canonical, Inc.
##

include('compat.inc');

if (description)
{
  script_id(148034);
  script_version("1.5");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/01/09");

  script_cve_id(
    "CVE-2020-27170",
    "CVE-2020-27171",
    "CVE-2021-3444",
    "CVE-2021-27363",
    "CVE-2021-27364",
    "CVE-2021-27365"
  );
  script_xref(name:"USN", value:"4887-1");

  script_name(english:"Ubuntu 18.04 LTS / 20.04 LTS : Linux kernel vulnerabilities (USN-4887-1)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Ubuntu host is missing one or more security updates.");
  script_set_attribute(attribute:"description", value:
"The remote Ubuntu 18.04 LTS / 20.04 LTS host has a package installed that is affected by multiple vulnerabilities as
referenced in the USN-4887-1 advisory.

  - An issue was discovered in the Linux kernel before 5.11.8. kernel/bpf/verifier.c performs undesirable out-
    of-bounds speculation on pointer arithmetic, leading to side-channel attacks that defeat Spectre
    mitigations and obtain sensitive information from kernel memory, aka CID-f232326f6966. This affects
    pointer types that do not define a ptr_limit. (CVE-2020-27170)

  - An issue was discovered in the Linux kernel before 5.11.8. kernel/bpf/verifier.c has an off-by-one error
    (with a resultant integer underflow) affecting out-of-bounds speculation on pointer arithmetic, leading to
    side-channel attacks that defeat Spectre mitigations and obtain sensitive information from kernel memory,
    aka CID-10d2bb2e6b1d. (CVE-2020-27171)

  - An issue was discovered in the Linux kernel through 5.11.3. A kernel pointer leak can be used to determine
    the address of the iscsi_transport structure. When an iSCSI transport is registered with the iSCSI
    subsystem, the transport's handle is available to unprivileged users via the sysfs file system, at
    /sys/class/iscsi_transport/$TRANSPORT_NAME/handle. When read, the show_transport_handle function (in
    drivers/scsi/scsi_transport_iscsi.c) is called, which leaks the handle. This handle is actually the
    pointer to an iscsi_transport struct in the kernel module's global variables. (CVE-2021-27363)

  - An issue was discovered in the Linux kernel through 5.11.3. drivers/scsi/scsi_transport_iscsi.c is
    adversely affected by the ability of an unprivileged user to craft Netlink messages. (CVE-2021-27364)

  - An issue was discovered in the Linux kernel through 5.11.3. Certain iSCSI data structures do not have
    appropriate length constraints or checks, and can exceed the PAGE_SIZE value. An unprivileged user can
    send a Netlink message that is associated with iSCSI, and has a length up to the maximum length of a
    Netlink message. (CVE-2021-27365)

  - The bpf verifier in the Linux kernel did not properly handle mod32 destination register truncation when
    the source register was known to be 0. A local attacker with the ability to load bpf programs could use
    this gain out-of-bounds reads in kernel memory leading to information disclosure (kernel memory), and
    possibly out-of-bounds writes that could potentially lead to code execution. This issue was addressed in
    the upstream kernel in commit 9b00f1b78809 (bpf: Fix truncation handling for mod32 dst reg wrt zero) and
    in Linux stable kernels 5.11.2, 5.10.19, and 5.4.101. (CVE-2021-3444)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://ubuntu.com/security/notices/USN-4887-1");
  script_set_attribute(attribute:"solution", value:
"Update the affected kernel package.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:P/I:P/A:P");
  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:U/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-2021-3444");

  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:"2021/03/07");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/03/23");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/03/24");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:18.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:canonical:ubuntu_linux:20.04:-:lts");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.10.0-1019-oem");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.3.0-1038-raspi2");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.3.0-1041-gke");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.3.0-72-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.3.0-72-lowlatency");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1012-gkeop");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1032-raspi");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1036-kvm");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1039-gke");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1040-gcp");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1041-oracle");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-1043-azure");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-70-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-70-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.4.0-70-lowlatency");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.6.0-1052-oem");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.8.0-48-generic");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.8.0-48-generic-64k");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.8.0-48-generic-lpae");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:canonical:ubuntu_linux:linux-image-5.8.0-48-lowlatency");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Ubuntu Local Security Checks");

  script_copyright(english:"Ubuntu Security Notice (C) 2021-2024 Canonical, Inc. / NASL script (C) 2021-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl", "linux_alt_patch_detect.nasl");
  script_require_keys("Host/cpu", "Host/Ubuntu", "Host/Ubuntu/release", "Host/Debian/dpkg-l");

  exit(0);
}

include('debian_package.inc');
include('ksplice.inc');

if ( ! get_kb_item('Host/local_checks_enabled') ) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
var os_release = get_kb_item('Host/Ubuntu/release');
if ( isnull(os_release) ) audit(AUDIT_OS_NOT, 'Ubuntu');
os_release = chomp(os_release);
if (! ('18.04' >< os_release || '20.04' >< os_release)) audit(AUDIT_OS_NOT, 'Ubuntu 18.04 / 20.04', 'Ubuntu ' + os_release);
if ( ! get_kb_item('Host/Debian/dpkg-l') ) audit(AUDIT_PACKAGE_LIST_MISSING);

var cpu = get_kb_item('Host/cpu');
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ('x86_64' >!< cpu && cpu !~ "^i[3-6]86$" && 's390' >!< cpu && 'aarch64' >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, 'Ubuntu', cpu);

var kernel_mappings = {
  '18.04': {
    '5.3.0': {
      'generic': '5.3.0-72',
      'lowlatency': '5.3.0-72',
      'raspi2': '5.3.0-1038',
      'gke': '5.3.0-1041'
    },
    '5.4.0': {
      'generic': '5.4.0-70',
      'generic-lpae': '5.4.0-70',
      'lowlatency': '5.4.0-70',
      'gkeop': '5.4.0-1012',
      'raspi': '5.4.0-1032',
      'gke': '5.4.0-1039',
      'gcp': '5.4.0-1040',
      'oracle': '5.4.0-1041',
      'azure': '5.4.0-1043'
    }
  },
  '20.04': {
    '5.10.0': {
      'oem': '5.10.0-1019'
    },
    '5.4.0': {
      'generic': '5.4.0-70',
      'generic-lpae': '5.4.0-70',
      'lowlatency': '5.4.0-70',
      'gkeop': '5.4.0-1012',
      'raspi': '5.4.0-1032',
      'kvm': '5.4.0-1036',
      'gcp': '5.4.0-1040',
      'oracle': '5.4.0-1041',
      'azure': '5.4.0-1043'
    },
    '5.6.0': {
      'oem': '5.6.0-1052'
    },
    '5.8.0': {
      'generic': '5.8.0-48',
      'generic-64k': '5.8.0-48',
      'generic-lpae': '5.8.0-48',
      'lowlatency': '5.8.0-48'
    }
  }
};

var host_kernel_release = get_kb_item('Host/uptrack-uname-r');
if (empty_or_null(host_kernel_release)) host_kernel_release = get_kb_item_or_exit('Host/uname-r');
var host_kernel_base_version = get_kb_item_or_exit('Host/Debian/kernel-base-version');
var host_kernel_type = get_kb_item_or_exit('Host/Debian/kernel-type');
if(empty_or_null(kernel_mappings[os_release][host_kernel_base_version][host_kernel_type])) audit(AUDIT_INST_VER_NOT_VULN, 'kernel ' + host_kernel_release);

var extra = '';
var kernel_fixed_version = kernel_mappings[os_release][host_kernel_base_version][host_kernel_type] + "-" + host_kernel_type;
if (deb_ver_cmp(ver1:host_kernel_release, ver2:kernel_fixed_version) < 0)
{
  extra = extra + 'Running Kernel level of ' + host_kernel_release + ' does not meet the minimum fixed level of ' + kernel_fixed_version + ' for this advisory.\n\n';
}
  else
{
  audit(AUDIT_PATCH_INSTALLED, 'Kernel package for USN-4887-1');
}

if (get_one_kb_item('Host/ksplice/kernel-cves'))
{
  var cve_list = make_list('CVE-2020-27170', 'CVE-2020-27171', 'CVE-2021-3444', 'CVE-2021-27363', 'CVE-2021-27364', 'CVE-2021-27365');
  if (ksplice_cves_check(cve_list))
  {
    audit(AUDIT_PATCH_INSTALLED, 'KSplice hotfix for USN-4887-1');
  }
  else
  {
    extra = extra + ksplice_reporting_text();
  }
}
if (extra) {
  security_report_v4(
    port       : 0,
    severity   : SECURITY_WARNING,
    extra      : extra
  );
  exit(0);
}