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%%% Copyright (c) 2014, NORDUnet A/S.
%%% See LICENSE for licensing information.
-module(x509).
-export([valid_chain_p/3, detox_precert/1]).
-include_lib("public_key/include/public_key.hrl").
-type der_encoded() :: public_key:der_encoded().
%%%%%%%%%%%%%%%%%%%%
%% @doc Verify that the leaf cert or precert has a valid chain back to
%% an acceptable root cert. Order of certificates in second argument
%% is: leaf cert in head, chain in tail. Order of first argument is
%% irrelevant.
-spec valid_chain_p([der_encoded()], [der_encoded()], integer()) -> boolean().
valid_chain_p(_, _, MaxChainLength) when MaxChainLength =< 0 ->
false;
valid_chain_p(AcceptableRootCerts, [TopCert], MaxChainLength) ->
case lists:member(TopCert, AcceptableRootCerts) of
true -> % Top cert is part of chain.
true;
false -> % Top cert might be signed by cert in truststore.
(MaxChainLength > 1) and
lists:any(fun(X) ->
signed_by_p(TopCert, X) end,
AcceptableRootCerts)
end;
valid_chain_p(AcceptableRootCerts, [BottomCert|Rest], MaxChainLength) ->
case signed_by_p(BottomCert, hd(Rest)) of
false -> false;
true -> valid_chain_p(AcceptableRootCerts, Rest, MaxChainLength - 1)
end.
-spec signed_by_p(der_encoded(), der_encoded()) -> boolean().
signed_by_p(Cert, IssuerCert) ->
%% FIXME: Validate presence and contents (against constraints) of
%% names (subject, subjectAltName, emailAddress) too?
case public_key:pkix_is_issuer(Cert, IssuerCert) of
true -> % Cert.issuer does match IssuerCert.subject.
public_key:pkix_verify(Cert, public_key(IssuerCert));
false ->
false
end.
-spec public_key(der_encoded() | #'OTPCertificate'{}) -> public_key:public_key().
public_key(CertDer) when is_binary(CertDer) ->
public_key(public_key:pkix_decode_cert(CertDer, otp));
public_key(#'OTPCertificate'{
tbsCertificate =
#'OTPTBSCertificate'{subjectPublicKeyInfo =
#'OTPSubjectPublicKeyInfo'{
subjectPublicKey = Key}}}) ->
Key.
%%%%%%%%%%%%%%%%%%%%
%% Precertificates according to draft-ietf-trans-rfc6962-bis-04.
%% Submitted precerts have a special critical poison extension -- OID
%% 1.3.6.1.4.1.11129.2.4.3, whose extnValue OCTET STRING contains
%% ASN.1 NULL data (0x05 0x00).
%% They are signed with either the CA cert that will sign the final
%% cert or Precertificate Signing Certificate directly signed by the
%% CA cert that will sign the final cert. A Precertificate Signing
%% Certificate has CA:true and Extended Key Usage: Certificate
%% Transparency, OID 1.3.6.1.4.1.11129.2.4.4.
%% A PreCert in a SignedCertificateTimestamp does _not_ contain the
%% poison extension, nor a Precertificate Signing Certificate. This
%% means that we might have to 1) remove poison extensions in leaf
%% certs, 2) remove "poisoned signatures", 3) change issuer and
%% Authority Key Identifier of leaf certs.
-spec detox_precert([#'Certificate'{}]) -> [#'Certificate'{}].
detox_precert(CertChain) ->
CertChain. % NYI
|
