Amazon Linux AMI : krb5 (ALAS-2015-624)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux AMI Security Advisory ALAS-2015-624.
#

include("compat.inc");

if (description)
{
  script_id(87350);
  script_version("2.4");
  script_cvs_date("Date: 2018/04/18 15:09:35");

  script_cve_id("CVE-2014-5355", "CVE-2015-2694");
  script_xref(name:"ALAS", value:"2015-624");

  script_name(english:"Amazon Linux AMI : krb5 (ALAS-2015-624)");
  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 flaw was found in the OTP kdcpreauth module of MIT Kerberos. A
remote attacker could use this flaw to bypass the requires_preauth
flag on a client principal and obtain a ciphertext encrypted in the
principal's long-term key. This ciphertext could be used to conduct an
off-line dictionary attack against the user's password.

It was found that the krb5_read_message() function of MIT Kerberos did
not correctly sanitize input, and could create invalid krb5_data
objects. A remote, unauthenticated attacker could use this flaw to
crash a Kerberos child process via a specially crafted request."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://alas.aws.amazon.com/ALAS-2015-624.html"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Run 'yum update krb5' to update your system."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:N");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-devel");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-libs");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-pkinit-openssl");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-server");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-server-ldap");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:krb5-workstation");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux");

  script_set_attribute(attribute:"patch_publication_date", value:"2015/12/14");
  script_set_attribute(attribute:"plugin_publication_date", value:"2015/12/15");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2015-2018 Tenable Network Security, Inc.");
  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:"krb5-debuginfo-1.13.2-10.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"krb5-devel-1.13.2-10.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"krb5-libs-1.13.2-10.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"krb5-pkinit-openssl-1.13.2-10.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"krb5-server-1.13.2-10.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"krb5-server-ldap-1.13.2-10.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"krb5-workstation-1.13.2-10.39.amzn1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get());
  else security_warning(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "krb5-debuginfo / krb5-devel / krb5-libs / krb5-pkinit-openssl / etc");
}