Debian DSA-4965-1 : libssh - security update

#%NASL_MIN_LEVEL 70300
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Debian Security Advisory dsa-4965. The text
# itself is copyright (C) Software in the Public Interest, Inc.
#

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

if (description)
{
  script_id(152967);
  script_version("1.5");
  script_set_attribute(attribute:"plugin_modification_date", value:"2023/10/06");

  script_cve_id("CVE-2021-3634");
  script_xref(name:"IAVA", value:"2022-A-0041-S");

  script_name(english:"Debian DSA-4965-1 : libssh - security update");

  script_set_attribute(attribute:"synopsis", value:
"The remote Debian host is missing a security-related update.");
  script_set_attribute(attribute:"description", value:
"The remote Debian 11 host has packages installed that are affected by a vulnerability as referenced in the dsa-4965
advisory.

  - A flaw has been found in libssh in versions prior to 0.9.6. The SSH protocol keeps track of two shared
    secrets during the lifetime of the session. One of them is called secret_hash and the other session_id.
    Initially, both of them are the same, but after key re-exchange, previous session_id is kept and used as
    an input to new secret_hash. Historically, both of these buffers had shared length variable, which worked
    as long as these buffers were same. But the key re-exchange operation can also change the key exchange
    method, which can be based on hash of different size, eventually creating secret_hash of different size
    than the session_id has. This becomes an issue when the session_id memory is zeroed or when it is used
    again during second key re-exchange. (CVE-2021-3634)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version
number.");
  script_set_attribute(attribute:"see_also", value:"https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993046");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/source-package/libssh");
  script_set_attribute(attribute:"see_also", value:"https://www.debian.org/security/2021/dsa-4965");
  script_set_attribute(attribute:"see_also", value:"https://security-tracker.debian.org/tracker/CVE-2021-3634");
  script_set_attribute(attribute:"see_also", value:"https://packages.debian.org/source/bullseye/libssh");
  script_set_attribute(attribute:"solution", value:
"Upgrade the libssh packages.

For the stable distribution (bullseye), this problem has been fixed in version 0.9.5-1+deb11u1.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:S/C:N/I:N/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:L/UI:N/S:U/C:N/I:N/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-2021-3634");

  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:"2021/08/31");
  script_set_attribute(attribute:"patch_publication_date", value:"2021/08/31");
  script_set_attribute(attribute:"plugin_publication_date", value:"2021/09/02");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libssh-4");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libssh-dev");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libssh-doc");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libssh-gcrypt-4");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:libssh-gcrypt-dev");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:11.0");
  script_set_attribute(attribute:"stig_severity", value:"II");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2021-2023 and is owned by Tenable, Inc. or an Affiliate thereof.");

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

  exit(0);
}

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

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);

var release = get_kb_item('Host/Debian/release');
if ( isnull(release) ) audit(AUDIT_OS_NOT, 'Debian');
var release = chomp(release);
if (! preg(pattern:"^(11)\.[0-9]+", string:release)) audit(AUDIT_OS_NOT, 'Debian 11.0', 'Debian ' + release);
var 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, 'Debian', cpu);

var pkgs = [
    {'release': '11.0', 'prefix': 'libssh-4', 'reference': '0.9.5-1+deb11u1'},
    {'release': '11.0', 'prefix': 'libssh-dev', 'reference': '0.9.5-1+deb11u1'},
    {'release': '11.0', 'prefix': 'libssh-doc', 'reference': '0.9.5-1+deb11u1'},
    {'release': '11.0', 'prefix': 'libssh-gcrypt-4', 'reference': '0.9.5-1+deb11u1'},
    {'release': '11.0', 'prefix': 'libssh-gcrypt-dev', 'reference': '0.9.5-1+deb11u1'}
];

var flag = 0;
foreach package_array ( pkgs ) {
  var release = NULL;
  var prefix = NULL;
  var reference = NULL;
  if (!empty_or_null(package_array['release'])) release = package_array['release'];
  if (!empty_or_null(package_array['prefix'])) prefix = package_array['prefix'];
  if (!empty_or_null(package_array['reference'])) reference = package_array['reference'];
  if (release && prefix && reference) {
    if (deb_check(release:release, prefix:prefix, reference:reference)) flag++;
  }
}

if (flag)
{
  security_report_v4(
    port       : 0,
    severity   : SECURITY_WARNING,
    extra      : deb_report_get()
  );
  exit(0);
}
else
{
  var tested = deb_pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, 'libssh-4 / libssh-dev / libssh-doc / libssh-gcrypt-4 / etc');
}