%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2008-2010. 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%
%%
%%
%%% Description: Reading and writing of PEM type encoded files.
%% PEM encoded files have the following structure:
%%
%% <text>
%% -----BEGIN SOMETHING-----<CR><LF>
%% <Base64 encoding line><CR><LF>
%% <Base64 encoding line><CR><LF>
%% ...
%% -----END SOMETHING-----<CR><LF>
%% <text>
%%
%% A file can contain several BEGIN/END blocks. Text lines between
%% blocks are ignored.
%%
%% The encoding is divided into lines separated by <NL>, and each line
%% is precisely 64 characters long (excluding the <NL> characters,
%% except the last line which 64 characters long or shorter. <NL> may
%% follow the last line.
-module(pubkey_pem).
-export([read_file/1, read_file/2, write_file/2, decode/2]).
-export([decode_key/2]).
-define(ENCODED_LINE_LENGTH, 64).
%%====================================================================
%% Internal application API
%%====================================================================
read_file(File) ->
read_file(File, no_passwd).
read_file(File, Passwd) ->
{ok, Bin} = file:read_file(File),
decode(Bin, Passwd).
write_file(File, Ds) ->
file:write_file(File, encode_file(Ds)).
decode_key({_Type, Bin, not_encrypted}, _) ->
Bin;
decode_key({_Type, Bin, {Chipher,Salt}}, Password) ->
decode_key(Bin, Password, Chipher, Salt).
decode(Bin, Passwd) ->
decode_file(split_bin(Bin), Passwd).
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
split_bin(Bin) ->
split_bin(0, Bin).
split_bin(N, Bin) ->
case Bin of
<<Line:N/binary, "\r\n", Rest/binary>> ->
[Line | split_bin(0, Rest)];
<<Line:N/binary, "\n", Rest/binary>> ->
[Line | split_bin(0, Rest)];
<<Line:N/binary>> ->
[Line];
_ ->
split_bin(N+1, Bin)
end.
decode_file(Bin, Passwd) ->
decode_file(Bin, [], [Passwd]).
decode_file([<<"-----BEGIN CERTIFICATE REQUEST-----", _/binary>>|Rest], Ens, Info) ->
decode_file2(Rest, [], Ens, cert_req, Info);
decode_file([<<"-----BEGIN CERTIFICATE-----", _/binary>>|Rest], Ens, Info) ->
decode_file2(Rest, [], Ens, cert, Info);
decode_file([<<"-----BEGIN RSA PRIVATE KEY-----", _/binary>>|Rest], Ens, Info) ->
decode_file2(Rest, [], Ens, rsa_private_key, Info);
decode_file([<<"-----BEGIN DSA PRIVATE KEY-----", _/binary>>|Rest], Ens, Info) ->
decode_file2(Rest, [], Ens, dsa_private_key, Info);
decode_file([<<"-----BEGIN DH PARAMETERS-----", _/binary>>|Rest], Ens, Info) ->
decode_file2(Rest, [], Ens, dh_params, Info);
decode_file([_|Rest], Ens, Info) ->
decode_file(Rest, Ens, Info);
decode_file([], Ens, _Info) ->
{ok, lists:reverse(Ens)}.
decode_file2([<<"Proc-Type: 4,ENCRYPTED", _/binary>>| Rest0], RLs, Ens, Tag, Info0) ->
[InfoLine|Rest] = Rest0,
Info = dek_info(InfoLine, Info0),
decode_file2(Rest, RLs, Ens, Tag, Info);
decode_file2([<<"-----END", _/binary>>| Rest], RLs, Ens, Tag, Info0) ->
Cs = erlang:iolist_to_binary(lists:reverse(RLs)),
Bin = base64:mime_decode(Cs),
case Info0 of
[Password, Cipher, SaltHex | Info1] ->
Salt = unhex(SaltHex),
Enc = {Cipher, Salt},
Decoded = decode_key(Bin, Password, Cipher, Salt),
decode_file(Rest, [{Tag, Decoded, Enc}| Ens], Info1);
_ ->
decode_file(Rest, [{Tag, Bin, not_encrypted}| Ens], Info0)
end;
decode_file2([L|Rest], RLs, Ens, Tag, Info0) ->
decode_file2(Rest, [L|RLs], Ens, Tag, Info0);
decode_file2([], _, Ens, _, _) ->
{ok, lists:reverse(Ens)}.
%% TODO Support same as decode_file
encode_file(Ds) ->
lists:map(
fun({cert, Bin}) ->
%% PKIX (X.509)
["-----BEGIN CERTIFICATE-----\n",
b64encode_and_split(Bin),
"-----END CERTIFICATE-----\n\n"];
({cert_req, Bin}) ->
%% PKCS#10
["-----BEGIN CERTIFICATE REQUEST-----\n",
b64encode_and_split(Bin),
"-----END CERTIFICATE REQUEST-----\n\n"];
({rsa_private_key, Bin}) ->
%% PKCS#?
["XXX Following key assumed not encrypted\n",
"-----BEGIN RSA PRIVATE KEY-----\n",
b64encode_and_split(Bin),
"-----END RSA PRIVATE KEY-----\n\n"]
end, Ds).
dek_info(Line0, Info) ->
Line = binary_to_list(Line0),
[_, DekInfo0] = string:tokens(Line, ": "),
DekInfo1 = string:tokens(DekInfo0, ",\n"),
Info ++ DekInfo1.
unhex(S) ->
unhex(S, []).
unhex("", Acc) ->
list_to_binary(lists:reverse(Acc));
unhex([D1, D2 | Rest], Acc) ->
unhex(Rest, [erlang:list_to_integer([D1, D2], 16) | Acc]).
decode_key(Data, no_passwd, _Alg, _Salt) ->
Data;
decode_key(Data, Password, "DES-CBC", Salt) ->
Key = password_to_key(Password, Salt, 8),
IV = Salt,
crypto:des_cbc_decrypt(Key, IV, Data);
decode_key(Data, Password, "DES-EDE3-CBC", Salt) ->
Key = password_to_key(Password, Salt, 24),
IV = Salt,
<<Key1:8/binary, Key2:8/binary, Key3:8/binary>> = Key,
crypto:des_ede3_cbc_decrypt(Key1, Key2, Key3, IV, Data).
password_to_key(Data, Salt, KeyLen) ->
<<Key:KeyLen/binary, _/binary>> =
password_to_key(<<>>, Data, Salt, KeyLen, <<>>),
Key.
password_to_key(_, _, _, Len, Acc) when Len =< 0 ->
Acc;
password_to_key(Prev, Data, Salt, Len, Acc) ->
M = crypto:md5([Prev, Data, Salt]),
password_to_key(M, Data, Salt, Len - size(M), <<Acc/binary, M/binary>>).
b64encode_and_split(Bin) ->
split_lines(base64:encode(Bin)).
split_lines(<<Text:?ENCODED_LINE_LENGTH/binary, Rest/binary>>) ->
[Text, $\n | split_lines(Rest)];
split_lines(Bin) ->
[Bin, $\n].
