docs/development/test-vectors.rst

Test vectors
============

Testing the correctness of the primitives implemented in each ``cryptography``
backend requires trusted test vectors. Where possible these vectors are
obtained from official sources such as `NIST`_ or `IETF`_ RFCs. When this is
not possible ``cryptography`` has chosen to create a set of custom vectors
using an official vector file as input to verify consistency between
implemented backends.

Vectors are kept in the `cryptography_vectors` package rather than within our
main test suite.

Sources
-------

Asymmetric ciphers
~~~~~~~~~~~~~~~~~~

* RSA PKCS #1 from the RSA FTP site (ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/
  and ftp://ftp.rsa.com/pub/rsalabs/tmp/).
* RSA FIPS 186-2 and PKCS1 v1.5 vulnerability test vectors from `NIST CAVP`_.
* FIPS 186-2 and FIPS 186-3 DSA test vectors from `NIST CAVP`_.
* FIPS 186-2 and FIPS 186-3 ECDSA test vectors from `NIST CAVP`_.
* DH and ECDH and ECDH+KDF(17.4) test vectors from `NIST CAVP`_.
* Ed25519 test vectors from the `Ed25519 website_`.
* OpenSSL PEM RSA serialization vectors from the `OpenSSL example key`_ and
  `GnuTLS key parsing tests`_.
* OpenSSL PEM DSA serialization vectors from the `GnuTLS example keys`_.
* PKCS #8 PEM serialization vectors from

  * GnuTLS: `enc-rsa-pkcs8.pem`_, `enc2-rsa-pkcs8.pem`_,
    `unenc-rsa-pkcs8.pem`_, `pkcs12_s2k_pem.c`_. The contents of
    `enc2-rsa-pkcs8.pem`_ was re-encrypted using a stronger PKCS#8 cipher.
  * `Botan's ECC private keys`_.
* `asymmetric/public/PKCS1/dsa.pub.pem`_ is a PKCS1 DSA public key from the
  Ruby test suite.


Custom asymmetric vectors
~~~~~~~~~~~~~~~~~~~~~~~~~

.. toctree::
    :maxdepth: 1

    custom-vectors/secp256k1

* ``asymmetric/PEM_Serialization/ec_private_key.pem`` and
  ``asymmetric/DER_Serialization/ec_private_key.der`` - Contains an Elliptic
  Curve key generated by OpenSSL from the curve ``secp256r1``.
* ``asymmetric/PEM_Serialization/ec_private_key_encrypted.pem`` and
  ``asymmetric/DER_Serialization/ec_private_key_encrypted.der``- Contains the
  same Elliptic Curve key as ``ec_private_key.pem``, except that it is
  encrypted with AES-128 with the password "123456".
* ``asymmetric/PEM_Serialization/ec_public_key.pem`` and
  ``asymmetric/DER_Serialization/ec_public_key.der``- Contains the public key
  corresponding to ``ec_private_key.pem``, generated using OpenSSL.
* ``asymmetric/PEM_Serialization/rsa_private_key.pem`` - Contains an RSA 2048
  bit key generated using OpenSSL, protected by the secret "123456" with DES3
  encryption.
* ``asymmetric/PEM_Serialization/rsa_public_key.pem`` and
  ``asymmetric/DER_Serialization/rsa_public_key.der``- Contains an RSA 2048
  bit public generated using OpenSSL from ``rsa_private_key.pem``.
* ``asymmetric/PEM_Serialization/dsaparam.pem`` - Contains 2048-bit DSA
  parameters generated using OpenSSL; contains no keys.
* ``asymmetric/PEM_Serialization/dsa_private_key.pem`` - Contains a DSA 2048
  bit key generated using OpenSSL from the parameters in ``dsaparam.pem``,
  protected by the secret "123456" with DES3 encryption.
* ``asymmetric/PEM_Serialization/dsa_public_key.pem`` and
  ``asymmetric/DER_Serialization/dsa_public_key.der`` - Contains a DSA 2048 bit
  key generated using OpenSSL from ``dsa_private_key.pem``.
* ``asymmetric/PKCS8/unenc-dsa-pkcs8.pem`` and
  ``asymmetric/DER_Serialization/unenc-dsa-pkcs8.der`` - Contains a DSA 1024
  bit key generated using OpenSSL.
* ``asymmetric/PKCS8/unenc-dsa-pkcs8.pub.pem`` and
  ``asymmetric/DER_Serialization/unenc-dsa-pkcs8.pub.der`` - Contains a DSA
  2048 bit public key generated using OpenSSL from ``unenc-dsa-pkcs8.pem``.
* DER conversions of the `GnuTLS example keys`_ for DSA as well as the
  `OpenSSL example key`_ for RSA.
* DER conversions of `enc-rsa-pkcs8.pem`_, `enc2-rsa-pkcs8.pem`_, and
  `unenc-rsa-pkcs8.pem`_.
* ``asymmetric/public/PKCS1/rsa.pub.pem`` and
  ``asymmetric/public/PKCS1/rsa.pub.der`` are PKCS1 conversions of the public
  key from ``asymmetric/PKCS8/unenc-rsa-pkcs8.pem`` using PEM and DER encoding.


Key exchange
~~~~~~~~~~~~

* ``vectors/cryptography_vectors/asymmetric/DH/RFC5114.txt`` contains
  Diffie-Hellman examples from appendix A.1, A.2 and A.3 of :rfc:`5114`.

X.509
~~~~~

* PKITS test suite from `NIST PKI Testing`_.
* ``v1_cert.pem`` from the OpenSSL source tree (`testx509.pem`_).
* ``ecdsa_root.pem`` - `DigiCert Global Root G3`_, a ``secp384r1`` ECDSA root
  certificate.
* ``verisign-md2-root.pem`` - A legacy Verisign public root signed using the
  MD2 algorithm. This is a PEM conversion of the `root data`_ in the NSS source
  tree.
* ``cryptography.io.pem`` - A leaf certificate issued by RapidSSL for the
  cryptography website.
* ``rapidssl_sha256_ca_g3.pem`` - The intermediate CA that issued the
  ``cryptography.io.pem`` certificate.
* ``wildcard_san.pem`` - A leaf certificate issued by a public CA for
  ``langui.sh`` that contains wildcard entries in the SAN extension.
* ``san_edipartyname.der`` - A DSA certificate from a `Mozilla bug`_
  containing a SAN extension with an ``ediPartyName`` general name.
* ``san_x400address.der`` - A DSA certificate from a `Mozilla bug`_ containing
  a SAN extension with an ``x400Address`` general name.

Custom X.509 Vectors
~~~~~~~~~~~~~~~~~~~~

* ``invalid_version.pem`` - Contains an RSA 2048 bit certificate with the
  X.509 version field set to ``0x7``.
* ``post2000utctime.pem`` - Contains an RSA 2048 bit certificate with the
  ``notBefore`` and ``notAfter`` fields encoded as post-2000 ``UTCTime``.
* ``dsa_selfsigned_ca.pem`` - Contains a DSA self-signed CA certificate
  generated using OpenSSL.
* ``ec_no_named_curve.pem`` - Contains an ECDSA certificate that does not have
  an embedded OID defining the curve.
* ``all_supported_names.pem`` - An RSA 2048 bit certificate generated using
  OpenSSL that contains a subject and issuer that have two of each supported
  attribute type from :rfc:`5280`.
* ``unsupported_subject_name.pem`` - An RSA 2048 bit self-signed CA certificate
  generated using OpenSSL that contains the unsupported "initials" name.
* ``utf8_common_name.pem`` - An RSA 2048 bit self-signed CA certificate
  generated using OpenSSL that contains a UTF8String common name with the value
  "We heart UTF8!™".
* ``two_basic_constraints.pem`` - An RSA 2048 bit self-signed certificate
  containing two basic constraints extensions.
* ``basic_constraints_not_critical.pem`` - An RSA 2048 bit self-signed
  certificate containing a basic constraints extension that is not marked as
  critical.
* ``bc_path_length_zero.pem`` - An RSA 2048 bit self-signed
  certificate containing a basic constraints extension with a path length of
  zero.
* ``unsupported_extension.pem`` - An RSA 2048 bit self-signed certificate
  containing an unsupported extension type. The OID was encoded as
  "1.2.3.4" with an ``extnValue`` of "value".
* ``unsupported_extension_critical.pem`` - An RSA 2048 bit self-signed
  certificate containing an unsupported extension type marked critical. The OID
  was encoded as "1.2.3.4" with an ``extnValue`` of "value".
* ``san_email_dns_ip_dirname_uri.pem`` - An RSA 2048 bit self-signed
  certificate containing a subject alternative name extension with the
  following general names: ``rfc822Name``, ``dNSName``, ``iPAddress``,
  ``directoryName``, and ``uniformResourceIdentifier``.
* ``san_other_name.pem`` - An RSA 2048 bit self-signed certificate containing
  a subject alternative name extension with the ``otherName`` general name.
* ``san_registered_id.pem`` - An RSA 1024 bit certificate containing a
  subject alternative name extension with the ``registeredID`` general name.
* ``all_key_usages.pem`` - An RSA 2048 bit self-signed certificate containing
  a key usage extension with all nine purposes set to true.
* ``extended_key_usage.pem`` - An RSA 2048 bit self-signed certificate
  containing an extended key usage extension with eight usages.
* ``san_idna_names.pem`` - An RSA 2048 bit self-signed certificate containing
  a subject alternative name extension with ``rfc822Name``, ``dNSName``, and
  ``uniformResourceIdentifier`` general names with IDNA (:rfc:`5895`) encoding.
* ``san_wildcard_idna.pem`` - An RSA 2048 bit self-signed certificate
  containing a subject alternative name extension with a ``dNSName`` general
  name with a wildcard IDNA (:rfc:`5895`) domain.
* ``san_idna2003_dnsname.pem`` - An RSA 2048 bit self-signed certificate
  containing a subject alternative name extension with an IDNA 2003
  (:rfc:`3490`) ``dNSName``.
* ``san_rfc822_names.pem`` - An RSA 2048 bit self-signed certificate containing
  a subject alternative name extension with various ``rfc822Name`` values.
* ``san_rfc822_idna.pem`` - An RSA 2048 bit self-signed certificate containing
  a subject alternative name extension with an IDNA ``rfc822Name``.
* ``san_uri_with_port.pem`` - An RSA 2048 bit self-signed certificate
  containing a subject alternative name extension with various
  ``uniformResourceIdentifier`` values.
* ``san_ipaddr.pem`` - An RSA 2048 bit self-signed certificate containing a
  subject alternative name extension with an ``iPAddress`` value.
* ``san_dirname.pem`` - An RSA 2048 bit self-signed certificate containing a
  subject alternative name extension with a ``directoryName`` value.
* ``inhibit_any_policy_5.pem`` - An RSA 2048 bit self-signed certificate
  containing an inhibit any policy extension with the value 5.
* ``inhibit_any_policy_negative.pem`` - An RSA 2048 bit self-signed certificate
  containing an inhibit any policy extension with the value -1.
* ``authority_key_identifier.pem`` - An RSA 2048 bit self-signed certificate
  containing an authority key identifier extension with key identifier,
  authority certificate issuer, and authority certificate serial number fields.
* ``authority_key_identifier_no_keyid.pem`` - An RSA 2048 bit self-signed
  certificate containing an authority key identifier extension with authority
  certificate issuer and authority certificate serial number fields.
* ``aia_ocsp_ca_issuers.pem`` - An RSA 2048 bit self-signed certificate
  containing an authority information access extension with two OCSP and one
  CA issuers entry.
* ``aia_ocsp.pem`` - An RSA 2048 bit self-signed certificate
  containing an authority information access extension with an OCSP entry.
* ``aia_ca_issuers.pem`` - An RSA 2048 bit self-signed certificate
  containing an authority information access extension with a CA issuers entry.
* ``cdp_fullname_reasons_crl_issuer.pem`` - An RSA 1024 bit certificate
  containing a CRL distribution points extension with ``fullName``,
  ``cRLIssuer``, and ``reasons`` data.
* ``cdp_crl_issuer.pem`` - An RSA 1024 bit certificate containing a CRL
  distribution points extension with ``cRLIssuer`` data.
* ``cdp_all_reasons.pem`` - An RSA 1024 bit certificate containing a CRL
  distribution points extension with all ``reasons`` bits set.
* ``cdp_reason_aa_compromise.pem`` - An RSA 1024 bit certificate containing a
  CRL distribution points extension with the ``AACompromise`` ``reasons`` bit
  set.
* ``nc_permitted_excluded.pem`` - An RSA 2048 bit self-signed certificate
  containing a name constraints extension with both permitted and excluded
  elements. Contains ``IPv4`` and ``IPv6`` addresses with network mask as well
  as ``dNSName`` with a leading period.
* ``nc_permitted_excluded_2.pem`` - An RSA 2048 bit self-signed certificate
  containing a name constraints extension with both permitted and excluded
  elements. Unlike ``nc_permitted_excluded.pem``, the general names do not
  contain any name constraints specific values.
* ``nc_permitted.pem`` - An RSA 2048 bit self-signed certificate containing a
  name constraints extension with permitted elements.
* ``nc_permitted_2.pem`` - An RSA 2048 bit self-signed certificate containing a
  name constraints extension with permitted elements that do not contain any
  name constraints specific values.
* ``nc_excluded.pem`` - An RSA 2048 bit self-signed certificate containing a
  name constraints extension with excluded elements.
* ``nc_invalid_ip_netmask.pem`` - An RSA 2048 bit self-signed certificate
  containing a name constraints extension with a permitted element that has an
  ``IPv6`` IP and an invalid network mask.
* ``nc_single_ip_netmask.pem`` - An RSA 2048 bit self-signed certificate
  containing a name constraints extension with a permitted element that has two
  IPs with ``/32`` and ``/128`` network masks.
* ``cp_user_notice_with_notice_reference.pem`` - An RSA 2048 bit self-signed
  certificate containing a certificate policies extension with a
  notice reference in the user notice.
* ``cp_user_notice_with_explicit_text.pem`` - An RSA 2048 bit self-signed
  certificate containing a certificate policies extension with explicit
  text and no notice reference.
* ``cp_cps_uri.pem`` - An RSA 2048 bit self-signed certificate containing a
  certificate policies extension with a CPS URI and no user notice.
* ``cp_user_notice_no_explicit_text.pem`` - An RSA 2048 bit self-signed
  certificate containing a certificate policies extension with a user notice
  with no explicit text.
* ``cp_invalid.pem`` - An RSA 2048 bit self-signed certificate containing a
  certificate policies extension with invalid data.
* ``ian_uri.pem`` - An RSA 2048 bit certificate containing an issuer
  alternative name extension with a ``URI`` general name.
* ``ocsp_nocheck.pem`` - An RSA 2048 bit self-signed certificate containing
  an ``OCSPNoCheck`` extension.
* ``pc_inhibit_require.pem`` - An RSA 2048 bit self-signed certificate
  containing a policy constraints extension with both inhibit policy mapping
  and require explicit policy elements.
* ``pc_inhibit.pem`` - An RSA 2048 bit self-signed certificate containing a
  policy constraints extension with an inhibit policy mapping element.
* ``pc_require.pem`` - An RSA 2048 bit self-signed certificate containing a
  policy constraints extension with a require explicit policy element.

Custom X.509 Request Vectors
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ``dsa_sha1.pem`` and ``dsa_sha1.der`` - Contain a certificate request using
  1024-bit DSA parameters and SHA1 generated using OpenSSL.
* ``rsa_md4.pem`` and ``rsa_md4.der`` - Contain a certificate request using
  2048 bit RSA and MD4 generated using OpenSSL.
* ``rsa_sha1.pem`` and ``rsa_sha1.der`` - Contain a certificate request using
  2048 bit RSA and SHA1 generated using OpenSSL.
* ``rsa_sha256.pem`` and ``rsa_sha256.der`` - Contain a certificate request
  using 2048 bit RSA and SHA256 generated using OpenSSL.
* ``ec_sha256.pem`` and ``ec_sha256.der`` - Contain a certificate request
  using EC (``secp384r1``) and SHA256 generated using OpenSSL.
* ``san_rsa_sha1.pem`` and ``san_rsa_sha1.der`` - Contain a certificate
  request using RSA and SHA1 with a subject alternative name extension
  generated using OpenSSL.
* ``two_basic_constraints.pem`` - A certificate signing request
  for a RSA 2048 bit key containing two basic constraints extensions.
* ``unsupported_extension.pem`` - A certificate signing request
  for an RSA 2048 bit key containing containing an unsupported
  extension type. The OID was encoded as "1.2.3.4" with an
  ``extnValue`` of "value".
* ``unsupported_extension_critical.pem`` - A certificate signing
  request for an RSA 2048 bit key containing containing an unsupported
  extension type marked critical. The OID was encoded as "1.2.3.4"
  with an ``extnValue`` of "value".
* ``basic_constraints.pem`` - A certificate signing request for a RSA
  2048 bit key containing a basic constraints extension marked as
  critical.

Custom X.509 Certificate Revocation List Vectors
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* ``crl_all_reasons.pem`` - Contains a CRL with 12 revoked certificates, whose
  serials match their list position. It includes one revocation without
  any entry extensions, 10 revocations with every supported reason code and one
  revocation with an unsupported, non-critical entry extension with the OID
  value set to "1.2.3.4".
* ``crl_dup_entry_ext.pem`` - Contains a CRL with one revocation which has a
  duplicate entry extension.
* ``crl_md2_unknown_crit_entry_ext.pem`` - Contains a CRL with one revocation
  which contains an unsupported critical entry extension with the OID value set
  to "1.2.3.4". The CRL uses an unsupported MD2 signature algorithm.
* ``crl_unsupported_reason.pem`` - Contains a CRL with one revocation which has
  an unsupported reason code.

Hashes
~~~~~~

* MD5 from :rfc:`1321`.
* RIPEMD160 from the `RIPEMD website`_.
* SHA1 from `NIST CAVP`_.
* SHA2 (224, 256, 384, 512) from `NIST CAVP`_.
* Whirlpool from the `Whirlpool website`_.

HMAC
~~~~

* HMAC-MD5 from :rfc:`2202`.
* HMAC-SHA1 from :rfc:`2202`.
* HMAC-RIPEMD160 from :rfc:`2286`.
* HMAC-SHA2 (224, 256, 384, 512) from :rfc:`4231`.

Key derivation functions
~~~~~~~~~~~~~~~~~~~~~~~~

* HKDF (SHA1, SHA256) from :rfc:`5869`.
* PBKDF2 (HMAC-SHA1) from :rfc:`6070`.
* scrypt from the `draft RFC`_.

Key wrapping
~~~~~~~~~~~~

* AES key wrap (AESKW) and 3DES key wrap test vectors from `NIST CAVP`_.

Recipes
~~~~~~~

* Fernet from its `specification repository`_.

Symmetric ciphers
~~~~~~~~~~~~~~~~~

* AES (CBC, CFB, ECB, GCM, OFB) from `NIST CAVP`_.
* AES CTR from :rfc:`3686`.
* 3DES (CBC, CFB, ECB, OFB) from `NIST CAVP`_.
* ARC4 from :rfc:`6229`.
* Blowfish (CBC, CFB, ECB, OFB) from `Bruce Schneier's vectors`_.
* Camellia (ECB) from NTT's `Camellia page`_ as linked by `CRYPTREC`_.
* Camellia (CBC, CFB, OFB) from `OpenSSL's test vectors`_.
* CAST5 (ECB) from :rfc:`2144`.
* CAST5 (CBC, CFB, OFB) generated by this project.
  See: :doc:`/development/custom-vectors/cast5`
* IDEA (ECB) from the `NESSIE IDEA vectors`_ created by `NESSIE`_.
* IDEA (CBC, CFB, OFB) generated by this project.
  See: :doc:`/development/custom-vectors/idea`
* SEED (ECB) from :rfc:`4269`.
* SEED (CBC) from :rfc:`4196`.
* SEED (CFB, OFB) generated by this project.
  See: :doc:`/development/custom-vectors/seed`

Two factor authentication
~~~~~~~~~~~~~~~~~~~~~~~~~

* HOTP from :rfc:`4226`
* TOTP from :rfc:`6238` (Note that an `errata`_ for the test vectors in RFC
  6238 exists)

CMAC
~~~~

* AES-128, AES-192, AES-256, 3DES from `NIST SP-800-38B`_

Creating test vectors
---------------------

When official vectors are unavailable ``cryptography`` may choose to build
its own using existing vectors as source material.

Custom Symmetric Vectors
~~~~~~~~~~~~~~~~~~~~~~~~

.. toctree::
    :maxdepth: 1

    custom-vectors/cast5
    custom-vectors/idea
    custom-vectors/seed

If official test vectors appear in the future the custom generated vectors
should be discarded.

Any vectors generated by this method must also be prefixed with the following
header format (substituting the correct information):

.. code-block:: python

    # CAST5 CBC vectors built for https://github.com/pyca/cryptography
    # Derived from the AESVS MMT test data for CBC
    # Verified against the CommonCrypto and Go crypto packages
    # Key Length : 128

.. _`NIST`: http://www.nist.gov/
.. _`IETF`: https://www.ietf.org/
.. _`NIST CAVP`: http://csrc.nist.gov/groups/STM/cavp/
.. _`Bruce Schneier's vectors`: https://www.schneier.com/code/vectors.txt
.. _`Camellia page`: http://info.isl.ntt.co.jp/crypt/eng/camellia/
.. _`CRYPTREC`: http://www.cryptrec.go.jp
.. _`OpenSSL's test vectors`: https://github.com/openssl/openssl/blob/97cf1f6c2854a3a955fd7dd3a1f113deba00c9ef/crypto/evp/evptests.txt#L232
.. _`RIPEMD website`: http://homes.esat.kuleuven.be/~bosselae/ripemd160.html
.. _`Whirlpool website`: http://www.larc.usp.br/~pbarreto/WhirlpoolPage.html
.. _`draft RFC`: https://tools.ietf.org/html/draft-josefsson-scrypt-kdf-01
.. _`Specification repository`: https://github.com/fernet/spec
.. _`errata`: http://www.rfc-editor.org/errata_search.php?rfc=6238
.. _`OpenSSL example key`: https://github.com/openssl/openssl/blob/d02b48c63a58ea4367a0e905979f140b7d090f86/test/testrsa.pem
.. _`GnuTLS key parsing tests`: https://gitlab.com/gnutls/gnutls/commit/f16ef39ef0303b02d7fa590a37820440c466ce8d
.. _`enc-rsa-pkcs8.pem`: https://gitlab.com/gnutls/gnutls/blob/f8d943b38bf74eaaa11d396112daf43cb8aa82ae/tests/pkcs8-decode/encpkcs8.pem
.. _`enc2-rsa-pkcs8.pem`: https://gitlab.com/gnutls/gnutls/blob/f8d943b38bf74eaaa11d396112daf43cb8aa82ae/tests/pkcs8-decode/enc2pkcs8.pem
.. _`unenc-rsa-pkcs8.pem`: https://gitlab.com/gnutls/gnutls/blob/f8d943b38bf74eaaa11d396112daf43cb8aa82ae/tests/pkcs8-decode/unencpkcs8.pem
.. _`pkcs12_s2k_pem.c`: https://gitlab.com/gnutls/gnutls/blob/f8d943b38bf74eaaa11d396112daf43cb8aa82ae/tests/pkcs12_s2k_pem.c
.. _`Botan's ECC private keys`: https://github.com/randombit/botan/tree/4917f26a2b154e841cd27c1bcecdd41d2bdeb6ce/src/tests/data/ecc
.. _`GnuTLS example keys`: https://gitlab.com/gnutls/gnutls/commit/ad2061deafdd7db78fd405f9d143b0a7c579da7b
.. _`NESSIE IDEA vectors`: https://www.cosic.esat.kuleuven.be/nessie/testvectors/bc/idea/Idea-128-64.verified.test-vectors
.. _`NESSIE`: https://en.wikipedia.org/wiki/NESSIE
.. _`Ed25519 website`: http://ed25519.cr.yp.to/software.html
.. _`NIST SP-800-38B`: http://csrc.nist.gov/publications/nistpubs/800-38B/Updated_CMAC_Examples.pdf
.. _`NIST PKI Testing`: http://csrc.nist.gov/groups/ST/crypto_apps_infra/pki/pkitesting.html
.. _`testx509.pem`: https://github.com/openssl/openssl/blob/master/test/testx509.pem
.. _`DigiCert Global Root G3`: http://cacerts.digicert.com/DigiCertGlobalRootG3.crt
.. _`root data`: https://hg.mozilla.org/projects/nss/file/25b2922cc564/security/nss/lib/ckfw/builtins/certdata.txt#l2053
.. _`asymmetric/public/PKCS1/dsa.pub.pem`: https://github.com/ruby/ruby/blob/4ccb387f3bc436a08fc6d72c4931994f5de95110/test/openssl/test_pkey_dsa.rb#L53
.. _`Mozilla bug`: https://bugzilla.mozilla.org/show_bug.cgi?id=233586