Debian: Security Advisory (DLA-2500-1)

# SPDX-FileCopyrightText: 2020 Greenbone AG
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.892500");
  script_cve_id("CVE-2020-8284", "CVE-2020-8285", "CVE-2020-8286");
  script_tag(name:"creation_date", value:"2020-12-19 04:00:25 +0000 (Sat, 19 Dec 2020)");
  script_version("2024-02-02T05:06:07+0000");
  script_tag(name:"last_modification", value:"2024-02-02 05:06:07 +0000 (Fri, 02 Feb 2024)");
  script_tag(name:"cvss_base", value:"5.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:P/A:N");
  script_tag(name:"severity_vector", value:"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2020-12-15 02:18:29 +0000 (Tue, 15 Dec 2020)");

  script_name("Debian: Security Advisory (DLA-2500-1)");
  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2020 Greenbone AG");
  script_family("Debian Local Security Checks");
  script_dependencies("gather-package-list.nasl");
  script_mandatory_keys("ssh/login/debian_linux", "ssh/login/packages", re:"ssh/login/release=DEB9");

  script_xref(name:"Advisory-ID", value:"DLA-2500-1");
  script_xref(name:"URL", value:"https://www.debian.org/lts/security/2020/DLA-2500-1");
  script_xref(name:"URL", value:"https://security-tracker.debian.org/tracker/curl");
  script_xref(name:"URL", value:"https://wiki.debian.org/LTS");

  script_tag(name:"summary", value:"The remote host is missing an update for the Debian 'curl' package(s) announced via the DLA-2500-1 advisory.");

  script_tag(name:"vuldetect", value:"Checks if a vulnerable package version is present on the target host.");

  script_tag(name:"insight", value:"Several vulnerabilities were discovered in curl, a command line tool for transferring data with URL syntax and an easy-to-use client-side URL transfer library.

CVE-2020-8284

When curl performs a passive FTP transfer, it first tries the EPSV command and if that is not supported, it falls back to using PASV. Passive mode is what curl uses by default. A server response to a PASV command includes the (IPv4) address and port number for the client to connect back to in order to perform the actual data transfer. This is how the FTP protocol is designed to work. A malicious server can use the PASV response to trick curl into connecting back to a given IP address and port, and this way potentially make curl extract information about services that are otherwise private and not disclosed, for example doing port scanning and service banner extractions.

The IP address part of the response is now ignored by default, by making CURLOPT_FTP_SKIP_PASV_IP default to 1L instead of previously being 0L. This has the minor drawback that a small fraction of use cases might break, when a server truly needs the client to connect back to a different IP address than what the control connection uses and for those CURLOPT_FTP_SKIP_PASV_IP can be set to 0L. The same goes for the command line tool, which then might need --no-ftp-skip-pasv-ip set to prevent curl from ignoring the address in the server response.

CVE-2020-8285

libcurl offers a wildcard matching functionality, which allows a callback (set with CURLOPT_CHUNK_BGN_FUNCTION) to return information back to libcurl on how to handle a specific entry in a directory when libcurl iterates over a list of all available entries. When this callback returns CURL_CHUNK_BGN_FUNC_SKIP, to tell libcurl to not deal with that file, the internal function in libcurl then calls itself recursively to handle the next directory entry. If there's a sufficient amount of file entries and if the callback returns skip enough number of times, libcurl runs out of stack space. The exact amount will of course vary with platforms, compilers and other environmental factors. The content of the remote directory is not kept on the stack, so it seems hard for the attacker to control exactly what data that overwrites the stack - however it remains a Denial-Of-Service vector as a malicious user who controls a server that a libcurl-using application works with under these premises can trigger a crash.

The internal function is rewritten to instead and more appropriately use an ordinary loop instead of the recursive approach. This way, the stack use will remain the same no matter how many files that are skipped.

CVE-2020-8286

libcurl offers OCSP stapling via the CURLOPT_SSL_VERIFYSTATUS option. When set, libcurl verifies the OCSP response that a server responds with as part of the TLS handshake. It then aborts the TLS negotiation if something is wrong with the response. The same ... [Please see the references for more information on the vulnerabilities]");

  script_tag(name:"affected", value:"'curl' package(s) on Debian 9.");

  script_tag(name:"solution", value:"Please install the updated package(s).");

  script_tag(name:"solution_type", value:"VendorFix");
  script_tag(name:"qod_type", value:"package");

  exit(0);
}

include("revisions-lib.inc");
include("pkg-lib-deb.inc");

release = dpkg_get_ssh_release();
if(!release)
  exit(0);

res = "";
report = "";

if(release == "DEB9") {

  if(!isnull(res = isdpkgvuln(pkg:"curl", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl3", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl3-dbg", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl3-gnutls", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl3-nss", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl4-doc", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl4-gnutls-dev", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl4-nss-dev", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(!isnull(res = isdpkgvuln(pkg:"libcurl4-openssl-dev", ver:"7.52.1-5+deb9u13", rls:"DEB9"))) {
    report += res;
  }

  if(report != "") {
    security_message(data:report);
  } else if(__pkg_match) {
    exit(99);
  }
  exit(0);
}

exit(0);