Amazon Linux AMI : squid (ALAS-2020-1378)

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Amazon Linux AMI Security Advisory ALAS-2020-1378.
#

include('compat.inc');

if (description)
{
  script_id(137101);
  script_version("1.3");
  script_set_attribute(attribute:"plugin_modification_date", value:"2024/03/08");

  script_cve_id(
    "CVE-2019-12519",
    "CVE-2019-12521",
    "CVE-2019-12525",
    "CVE-2020-11945"
  );
  script_xref(name:"ALAS", value:"2020-1378");

  script_name(english:"Amazon Linux AMI : squid (ALAS-2020-1378)");

  script_set_attribute(attribute:"synopsis", value:
"The remote Amazon Linux AMI host is missing a security update.");
  script_set_attribute(attribute:"description", value:
"An issue was discovered in Squid through 4.7. When handling the tag
esi:when when ESI is enabled, Squid calls ESIExpression::Evaluate.
This function uses a fixed stack buffer to hold the expression while
it's being evaluated. When processing the expression, it could either
evaluate the top of the stack, or add a new member to the stack. When
adding a new member, there is no check to ensure that the stack won't
overflow.(CVE-2019-12519)

An issue was discovered in Squid through 4.7. When Squid is parsing
ESI, it keeps the ESI elements in ESIContext. ESIContext contains a
buffer for holding a stack of ESIElements. When a new ESIElement is
parsed, it is added via addStackElement. addStackElement has a check
for the number of elements in this buffer, but it's off by 1, leading
to a Heap Overflow of 1 element. The overflow is within the same
structure so it can't affect adjacent memory blocks, and thus just
leads to a crash while processing.(CVE-2019-12521)

An issue was discovered in Squid 3.3.9 through 3.5.28 and 4.x through
4.7. When Squid is configured to use Digest authentication, it parses
the header Proxy-Authorization. It searches for certain tokens such as
domain, uri, and qop. Squid checks if this token's value starts with a
quote and ends with one. If so, it performs a memcpy of its length
minus 2. Squid never checks whether the value is just a single quote
(which would satisfy its requirements), leading to a memcpy of its
length minus 1.(CVE-2019-12525)

An issue was discovered in Squid before 5.0.2. A remote attacker can
replay a sniffed Digest Authentication nonce to gain access to
resources that are otherwise forbidden. This occurs because the
attacker can overflow the nonce reference counter (a short integer).
Remote code execution may occur if the pooled token credentials are
freed (instead of replayed as valid credentials).(CVE-2020-11945)");
  script_set_attribute(attribute:"see_also", value:"https://alas.aws.amazon.com/ALAS-2020-1378.html");
  script_set_attribute(attribute:"solution", value:
"Run 'yum update squid' to update your system.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2020-11945");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");

  script_set_attribute(attribute:"vuln_publication_date", value:"2019/07/11");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/06/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/06/04");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:squid");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:squid-debuginfo");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:amazon:linux:squid-migration-script");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:amazon:linux");
  script_set_attribute(attribute:"generated_plugin", value:"current");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2020-2024 and is owned by Tenable, Inc. or an Affiliate thereof.");

  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:"squid-3.5.20-15.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"squid-debuginfo-3.5.20-15.39.amzn1")) flag++;
if (rpm_check(release:"ALA", reference:"squid-migration-script-3.5.20-15.39.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, "squid / squid-debuginfo / squid-migration-script");
}