Amazon Linux AMI : openssh (ALAS-2017-898)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux AMI Security Advisory ALAS-2017-898.
#

include("compat.inc");

if (description)
{
  script_id(103650);
  script_version("3.3");
  script_cvs_date("Date: 2019/04/10 16:10:16");

  script_cve_id("CVE-2016-10009", "CVE-2016-10011", "CVE-2016-10012", "CVE-2016-6210", "CVE-2016-6515");
  script_xref(name:"ALAS", value:"2017-898");

  script_name(english:"Amazon Linux AMI : openssh (ALAS-2017-898)");
  script_summary(english:"Checks rpm output for the updated packages");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Amazon Linux AMI host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"A covert timing channel flaw was found in the way OpenSSH handled
authentication of non-existent users. A remote unauthenticated
attacker could possibly use this flaw to determine valid user names by
measuring the timing of server responses. (CVE-2016-6210)

It was found that OpenSSH did not limit password lengths for password
authentication. A remote unauthenticated attacker could use this flaw
to temporarily trigger high CPU consumption in sshd by sending long
passwords. (CVE-2016-6515)

It was found that ssh-agent could load PKCS#11 modules from arbitrary
paths. An attacker having control of the forwarded agent-socket on the
server, and the ability to write to the filesystem of the client host,
could use this flaw to execute arbitrary code with the privileges of
the user running ssh-agent. (CVE-2016-10009)

It was found that the host private key material could possibly leak to
the privilege-separated child processes via re-allocated memory. An
attacker able to compromise the privilege-separated process could
therefore obtain the leaked key information. (CVE-2016-10011)

It was found that the boundary checks in the code implementing support
for pre-authentication compression could have been optimized out by
certain compilers. An attacker able to compromise the
privilege-separated process could possibly use this flaw for further
attacks against the privileged monitor process. (CVE-2016-10012)"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://alas.aws.amazon.com/ALAS-2017-898.html"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Run 'yum update openssh' to update your system."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:N/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:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh-cavs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh-clients");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh-keycat");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh-ldap");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:openssh-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:pam_ssh_agent_auth");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux");

  script_set_attribute(attribute:"patch_publication_date", value:"2017/10/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2017/10/04");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");
  script_family(english:"Amazon Linux Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/AmazonLinux/release", "Host/AmazonLinux/rpm-list");

  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/AmazonLinux/release");
if (isnull(release) || !strlen(release)) audit(AUDIT_OS_NOT, "Amazon Linux");
os_ver = pregmatch(pattern: "^AL(A|\d)", string:release);
if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Amazon Linux");
os_ver = os_ver[1];
if (os_ver != "A")
{
  if (os_ver == 'A') os_ver = 'AMI';
  audit(AUDIT_OS_NOT, "Amazon Linux AMI", "Amazon Linux " + os_ver);
}

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


flag = 0;
if (rpm_check(release:"ALA", reference:"openssh-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssh-cavs-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssh-clients-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssh-debuginfo-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssh-keycat-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssh-ldap-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"openssh-server-7.4p1-11.68.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"pam_ssh_agent_auth-0.10.3-1.11.68.amzn1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_hole(port:0, extra:rpm_report_get());
  else security_hole(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "openssh / openssh-cavs / openssh-clients / openssh-debuginfo / etc");
}