SSL Certificate Signed Using Weak Hashing Algorithm (Known CA)

#
# (C) Tenable Network Security, Inc.
#



if ( NASL_LEVEL < 3208 ) exit(0);



include('compat.inc');

if (description)
{
  script_id(95631);
  script_version("1.15");
  script_set_attribute(attribute:"plugin_modification_date", value:"2022/10/12");
  
  script_bugtraq_id(11849, 33065);

  script_name(english:"SSL Certificate Signed Using Weak Hashing Algorithm (Known CA)");

  script_set_attribute(attribute:"synopsis", value:
"A known CA SSL certificate in the certificate chain has been signed
using a weak hashing algorithm.");
  script_set_attribute(attribute:"description", value:
"The remote service uses a known CA certificate in the SSL certificate chain that has been signed using a 
cryptographically weak hashing algorithm (e.g., MD2, MD4, MD5, or SHA1). These signature algorithms are known to be 
vulnerable to collision attacks (CVE-2004-2761, for example). An attacker can exploit this to generate another 
certificate with the same digital signature, allowing the attacker to masquerade as the affected service.

Note that this plugin reports all SSL certificate chains signed with SHA-1 that expire after January 1, 2017 as 
vulnerable. This is in accordance with Google's gradual sunsetting of the SHA-1 cryptographic hash algorithm.

Note that this plugin will only fire on root certificates that are known certificate authorities as listed in Tenable 
Community Knowledge Article 000001752. That is what differentiates this plugin from plugin 35291, which will fire on any
certificate, not just known certificate authority root certificates.

Known certificate authority root certificates are inherently trusted and so any potential issues with the signature, 
including it being signed using a weak hashing algorithm, are not considered security issues.");
  # https://community.tenable.com/s/article/What-certificates-are-trusted-by-Tenable-io-and-Nessus-scans-by-default
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?ae636e78");
  script_set_attribute(attribute:"see_also", value:"https://tools.ietf.org/html/rfc3279");
  # https://docs.microsoft.com/en-us/security-updates/SecurityAdvisories/2008/961509
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?9bb87bf2");
  script_set_attribute(attribute:"solution", value:
"Contact the Certificate Authority to have the certificate reissued.");
  script_set_attribute(attribute:"risk_factor", value:"None");
  script_set_attribute(attribute:"cvss_score_source", value:"manual");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_cwe_id(310);

  script_set_attribute(attribute:"vuln_publication_date", value:"2004/08/18");
  script_set_attribute(attribute:"plugin_publication_date", value:"2016/12/08");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:ietf:md5");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:ietf:x.509_certificate");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"General");

  script_copyright(english:"This script is Copyright (C) 2016-2022 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssl_certificate_chain.nasl");
  script_require_keys("SSL/Chain/KnownCA/WeakHash");

  exit(0);
}

include('ssl_funcs.inc');

# Get the port that has a weak hash algorithm from the KB.
key = "SSL/Chain/KnownCA/WeakHash";
port = get_kb_item_or_exit(key);
key += "/" + port;

# If the user doesn't want the details, let's stop right here.
if (report_verbosity == 0)
{
  security_report_v4(port:port, severity:SECURITY_NOTE);
  exit(0);
}

# Get the list of certificates with weak hash algorithms.
certs = get_kb_list_or_exit(key);

# Add the certificates to the report.
attrs = make_list();
foreach attr (certs)
{
  attrs = make_list(attrs, attr);
}

# Report our findings.
report =
  '\nThe following known CA certificates were part of the certificate' +
  '\nchain sent by the remote host, but contain hashes that are considered' +
  '\nto be weak.' +
  '\n' +
  '\n' + cert_report(attrs, chain:FALSE, bar:'');

security_report_v4(port:port, extra:report, severity:SECURITY_NOTE);