EulerOS 2.0 SP3 : bash (EulerOS-SA-2020-2081)

2020-09-28T00:00:00
ID EULEROS_SA-2020-2081.NASL
Type nessus
Reporter This script is Copyright (C) 2020-2021 and is owned by Tenable, Inc. or an Affiliate thereof.
Modified 2020-09-28T00:00:00

Description

According to the version of the bash package installed, the EulerOS installation on the remote host is affected by the following vulnerability :

  • An issue was discovered in disable_priv_mode in shell.c in GNU Bash through 5.0 patch 11. By default, if Bash is run with its effective UID not equal to its real UID, it will drop privileges by setting its effective UID to its real UID. However, it does so incorrectly. On Linux and other systems that support 'saved UID' functionality, the saved UID is not dropped. An attacker with command execution in the shell can use 'enable -f' for runtime loading of a new builtin, which can be a shared object that calls setuid() and therefore regains privileges. However, binaries running with an effective UID of 0 are unaffected.(CVE-2019-18276)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

                                        
                                            #%NASL_MIN_LEVEL 70300
#
# (C) Tenable Network Security, Inc.
#

include('deprecated_nasl_level.inc');
include('compat.inc');

if (description)
{
  script_id(140848);
  script_version("1.4");
  script_set_attribute(attribute:"plugin_modification_date", value:"2021/01/06");

  script_cve_id(
    "CVE-2019-18276"
  );

  script_name(english:"EulerOS 2.0 SP3 : bash (EulerOS-SA-2020-2081)");
  script_summary(english:"Checks the rpm output for the updated package.");

  script_set_attribute(attribute:"synopsis", value:
"The remote EulerOS host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"According to the version of the bash package installed, the EulerOS
installation on the remote host is affected by the following
vulnerability :

  - An issue was discovered in disable_priv_mode in shell.c
    in GNU Bash through 5.0 patch 11. By default, if Bash
    is run with its effective UID not equal to its real
    UID, it will drop privileges by setting its effective
    UID to its real UID. However, it does so incorrectly.
    On Linux and other systems that support 'saved UID'
    functionality, the saved UID is not dropped. An
    attacker with command execution in the shell can use
    'enable -f' for runtime loading of a new builtin, which
    can be a shared object that calls setuid() and
    therefore regains privileges. However, binaries running
    with an effective UID of 0 are
    unaffected.(CVE-2019-18276)

Note that Tenable Network Security has extracted the preceding
description block directly from the EulerOS security advisory. Tenable
has attempted to automatically clean and format it as much as possible
without introducing additional issues.");
  # https://developer.huaweicloud.com/ict/en/site-euleros/euleros/security-advisories/EulerOS-SA-2020-2081
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?c957874e");
  script_set_attribute(attribute:"solution", value:
"Update the affected bash package.");
  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: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:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");

  script_set_attribute(attribute:"patch_publication_date", value:"2020/09/28");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/09/28");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:huawei:euleros:bash");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:huawei:euleros:2.0");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2020-2021 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/EulerOS/release", "Host/EulerOS/rpm-list", "Host/EulerOS/sp");
  script_exclude_keys("Host/EulerOS/uvp_version");

  exit(0);
}

include("audit.inc");
include("global_settings.inc");
include("rpm.inc");

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);

release = get_kb_item("Host/EulerOS/release");
if (isnull(release) || release !~ "^EulerOS") audit(AUDIT_OS_NOT, "EulerOS");
if (release !~ "^EulerOS release 2\.0(\D|$)") audit(AUDIT_OS_NOT, "EulerOS 2.0");

sp = get_kb_item("Host/EulerOS/sp");
if (isnull(sp) || sp !~ "^(3)$") audit(AUDIT_OS_NOT, "EulerOS 2.0 SP3");

uvp = get_kb_item("Host/EulerOS/uvp_version");
if (!empty_or_null(uvp)) audit(AUDIT_OS_NOT, "EulerOS 2.0 SP3", "EulerOS UVP " + uvp);

if (!get_kb_item("Host/EulerOS/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);

cpu = get_kb_item("Host/cpu");
if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$" && "aarch64" >!< cpu) audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "EulerOS", cpu);
if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_ARCH_NOT, "i686 / x86_64", cpu);

flag = 0;

pkgs = ["bash-4.2.46-28.h7"];

foreach (pkg in pkgs)
  if (rpm_check(release:"EulerOS-2.0", sp:"3", reference:pkg)) flag++;

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_HOLE,
    extra      : rpm_report_get()
  );
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "bash");
}