%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2007-2010. All Rights Reserved.
%%
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%%
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%%
%% %CopyrightEnd%
%%
%%----------------------------------------------------------------------
%% Purpose: Help funtions for handling certificat verification.
%% The path validation defined in ssl_handshake.erl that mainly
%% calls functions in this module is described in RFC 3280.
%%----------------------------------------------------------------------
-module(ssl_certificate).
-include("ssl_handshake.hrl").
-include("ssl_alert.hrl").
-include("ssl_internal.hrl").
-include("ssl_debug.hrl").
-include_lib("public_key/include/public_key.hrl").
-export([trusted_cert_and_path/2,
certificate_chain/2,
file_to_certificats/1,
validate_extension/3,
is_valid_extkey_usage/2,
is_valid_key_usage/2,
select_extension/2,
extensions_list/1,
signature_type/1
]).
%%====================================================================
%% Internal application API
%%====================================================================
%%--------------------------------------------------------------------
-spec trusted_cert_and_path([der_cert()], certdb_ref()) ->
{der_cert() | unknown_ca, [der_cert()]}.
%%
%% Description: Extracts the root cert (if not presents tries to
%% look it up, if not found {bad_cert, unknown_ca} will be added verification
%% errors. Returns {RootCert, Path, VerifyErrors}
%%--------------------------------------------------------------------
trusted_cert_and_path(CertChain, CertDbRef) ->
Path = [Cert | _] = lists:reverse(CertChain),
OtpCert = public_key:pkix_decode_cert(Cert, otp),
SignedAndIssuerID =
case public_key:pkix_is_self_signed(OtpCert) of
true ->
{ok, IssuerId} = public_key:pkix_issuer_id(OtpCert, self),
{self, IssuerId};
false ->
case public_key:pkix_issuer_id(OtpCert, other) of
{ok, IssuerId} ->
{other, IssuerId};
{error, issuer_not_found} ->
case find_issuer(OtpCert, no_candidate) of
{ok, IssuerId} ->
{other, IssuerId};
Other ->
Other
end
end
end,
case SignedAndIssuerID of
{error, issuer_not_found} ->
%% The root CA was not sent and can not be found.
{unknown_ca, Path};
{self, _} when length(Path) == 1 ->
{selfsigned_peer, Path};
{_ ,{SerialNr, Issuer}} ->
case ssl_manager:lookup_trusted_cert(CertDbRef, SerialNr, Issuer) of
{ok, {BinCert,_}} ->
{BinCert, Path};
_ ->
%% Root CA could not be verified
{unknown_ca, Path}
end
end.
%%--------------------------------------------------------------------
-spec certificate_chain(undefined | binary(), certdb_ref()) ->
{error, no_cert} | {ok, [der_cert()]}.
%%
%% Description: Return the certificate chain to send to peer.
%%--------------------------------------------------------------------
certificate_chain(undefined, _CertsDbRef) ->
{error, no_cert};
certificate_chain(OwnCert, CertsDbRef) ->
ErlCert = public_key:pkix_decode_cert(OwnCert, otp),
certificate_chain(ErlCert, OwnCert, CertsDbRef, [OwnCert]).
%%--------------------------------------------------------------------
-spec file_to_certificats(string()) -> [der_cert()].
%%
%% Description: Return list of DER encoded certificates.
%%--------------------------------------------------------------------
file_to_certificats(File) ->
{ok, List} = ssl_manager:cache_pem_file(File),
[Bin || {'Certificate', Bin, not_encrypted} <- List].
%%--------------------------------------------------------------------
-spec validate_extension(term(), #'Extension'{}, term()) -> {valid, term()} |
{fail, tuple()} |
{unknown, term()}.
%%
%% Description: Validates ssl/tls specific extensions
%%--------------------------------------------------------------------
validate_extension(_,{extension, #'Extension'{extnID = ?'id-ce-extKeyUsage',
extnValue = KeyUse}}, Role) ->
case is_valid_extkey_usage(KeyUse, Role) of
true ->
{valid, Role};
false ->
{fail, {bad_cert, invalid_ext_key_usage}}
end;
validate_extension(_, {bad_cert, _} = Reason, _) ->
{fail, Reason};
validate_extension(_, {extension, _}, Role) ->
{unknown, Role};
validate_extension(_, valid, Role) ->
{valid, Role}.
%%--------------------------------------------------------------------
-spec is_valid_key_usage(list(), term()) -> boolean().
%%
%% Description: Checks if Use is a valid key usage.
%%--------------------------------------------------------------------
is_valid_key_usage(KeyUse, Use) ->
lists:member(Use, KeyUse).
%%--------------------------------------------------------------------
-spec select_extension(term(), list()) -> undefined | #'Extension'{}.
%%
%% Description: Selects the extension identified by Id if present in
%% a list of extensions.
%%--------------------------------------------------------------------
select_extension(_, []) ->
undefined;
select_extension(Id, [#'Extension'{extnID = Id} = Extension | _]) ->
Extension;
select_extension(Id, [_ | Extensions]) ->
select_extension(Id, Extensions).
%%--------------------------------------------------------------------
-spec extensions_list(asn1_NOVALUE | list()) -> list().
%%
%% Description: Handles that
%%--------------------------------------------------------------------
extensions_list(asn1_NOVALUE) ->
[];
extensions_list(Extensions) ->
Extensions.
%%--------------------------------------------------------------------
-spec signature_type(term()) -> rsa | dsa .
%%
%% Description:
%%--------------------------------------------------------------------
signature_type(RSA) when RSA == ?sha1WithRSAEncryption;
RSA == ?md5WithRSAEncryption ->
rsa;
signature_type(?'id-dsa-with-sha1') ->
dsa.
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
certificate_chain(OtpCert, _Cert, CertsDbRef, Chain) ->
IssuerAndSelfSigned =
case public_key:pkix_is_self_signed(OtpCert) of
true ->
{public_key:pkix_issuer_id(OtpCert, self), true};
false ->
{public_key:pkix_issuer_id(OtpCert, other), false}
end,
case IssuerAndSelfSigned of
{_, true = SelfSigned} ->
certificate_chain(CertsDbRef, Chain, ignore, ignore, SelfSigned);
{{error, issuer_not_found}, SelfSigned} ->
case find_issuer(OtpCert, no_candidate) of
{ok, {SerialNr, Issuer}} ->
certificate_chain(CertsDbRef, Chain,
SerialNr, Issuer, SelfSigned);
_ ->
%% Guess the the issuer must be the root
%% certificate. The verification of the
%% cert chain will fail if guess is
%% incorrect.
{ok, lists:reverse(Chain)}
end;
{{ok, {SerialNr, Issuer}}, SelfSigned} ->
certificate_chain(CertsDbRef, Chain, SerialNr, Issuer, SelfSigned)
end.
certificate_chain(_CertsDbRef, Chain, _SerialNr, _Issuer, true) ->
{ok, lists:reverse(Chain)};
certificate_chain(CertsDbRef, Chain, SerialNr, Issuer, _SelfSigned) ->
case ssl_manager:lookup_trusted_cert(CertsDbRef,
SerialNr, Issuer) of
{ok, {IssuerCert, ErlCert}} ->
ErlCert = public_key:pkix_decode_cert(IssuerCert, otp),
certificate_chain(ErlCert, IssuerCert,
CertsDbRef, [IssuerCert | Chain]);
_ ->
%% The trusted cert may be obmitted from the chain as the
%% counter part needs to have it anyway to be able to
%% verify it. This will be the normal case for servers
%% that does not verify the clients and hence have not
%% specified the cacertfile.
{ok, lists:reverse(Chain)}
end.
find_issuer(OtpCert, PrevCandidateKey) ->
case ssl_manager:issuer_candidate(PrevCandidateKey) of
no_more_candidates ->
{error, issuer_not_found};
{Key, {_Cert, ErlCertCandidate}} ->
case public_key:pkix_is_issuer(OtpCert, ErlCertCandidate) of
true ->
public_key:pkix_issuer_id(ErlCertCandidate, self);
false ->
find_issuer(OtpCert, Key)
end
end.
is_valid_extkey_usage(KeyUse, client) ->
%% Client wants to verify server
is_valid_key_usage(KeyUse,?'id-kp-serverAuth');
is_valid_extkey_usage(KeyUse, server) ->
%% Server wants to verify client
is_valid_key_usage(KeyUse, ?'id-kp-clientAuth').
