%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2005-2010. 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: rsa public-key sign and verify
-module(ssh_rsa).
-export([verify/3, sign/2]).
-export([alg_name/0]).
-include("ssh.hrl").
-include("PKCS-1.hrl").
-define(MGF(Seed,Len), mgf1((Seed),(Len))).
-define(HASH(X), crypto:sha((X))).
-define(HLen, 20).
%% start() ->
%% crypto:start().
%% sign_file(File) ->
%% start(),
%% {ok,Bin} = file:read_file(File),
%% {ok,Key} = ssh_file:private_host_rsa_key(user),
%% sign(Key, Bin).
%% verify_file(File, Sig) ->
%% start(),
%% {ok,Bin} = file:read_file(File),
%% {ok,Key} = ssh_file:public_host_rsa_key(user),
%% verify(Key, Bin, Sig).
sign(Private,Mb) ->
rsassa_pkcs1_v1_5_sign(Private,Mb).
verify(Public,Mb,Sb) ->
rsassa_pkcs1_v1_5_verify(Public,Mb,Sb).
%% Integer to octet string
i2osp(X, XLen) ->
ssh_bits:i2bin(X, XLen).
%% Octet string to Integer
os2ip(X) ->
ssh_bits:bin2i(X).
%% decrypt1, M = message representative
%% rsaep(#ssh_key { public={N,E}}, M) ->
%% ?ssh_assert(M >= 0 andalso M =< N-1, out_of_range),
%% ssh_math:ipow(M, E, N).
%% encrypt1, C = cipher representative
%% rsadp(#ssh_key { public={N,_}, private={_,D}}, C) ->
%% ?ssh_assert(C >= 0 andalso C =< N-1, out_of_range),
%% ssh_math:ipow(C, D, N).
%% sign1, M = message representative
rsasp1(#ssh_key { public={N,_}, private={_,D}}, M) ->
?ssh_assert((M >= 0 andalso M =< N-1), out_of_range),
ssh_math:ipow(M, D, N).
%% verify1, S =signature representative
rsavp1(#ssh_key { public={N,E}}, S) ->
?ssh_assert(S >= 0 andalso S =< N-1, out_of_range),
ssh_math:ipow(S, E, N).
%% M messaage
%% rsaes_oaep_encrypt(Public, M) ->
%% rsaes_oaep_encrypt(Public, M, <<>>).
%% rsaes_oaep_encrypt(Public=#ssh_key { public={N,_E}}, M, L) ->
%% ?ssh_assert(size(L) =< 16#ffffffffffffffff, label_to_long),
%% K = (ssh_bits:isize(N)+7) div 8,
%% MLen = size(M),
%% %% LLen = size(L),
%% ?ssh_assert(MLen =< K - 2*?HLen - 2, message_to_long),
%% LHash = ?HASH(L),
%% PS = ssh_bits:fill_bits(K - MLen - 2*?HLen - 2, 0),
%% DB = <<LHash/binary, PS/binary, 16#01, M/binary>>,
%% Seed = ssh_bits:random(?HLen),
%% DbMask = ?MGF(Seed, K - ?HLen - 1),
%% MaskedDB = ssh_bits:xor_bits(DB, DbMask),
%% SeedMask = ?MGF(MaskedDB, ?HLen),
%% MaskedSeed = ssh_bits:xor_bits(Seed, SeedMask),
%% EM = <<16#00, MaskedSeed/binary, MaskedDB/binary>>,
%% Mc = os2ip(EM),
%% C = rsaep(Public, Mc),
%% i2osp(C, K).
%% rsaes_oaep_decrypt(Key, C) ->
%% rsaes_oaep_decrypt(Key, C, <<>>).
%% rsaes_oaep_decrypt(Private=#ssh_key { public={N,_},private={_,_}},Cb,L) ->
%% ?ssh_assert(size(L) =< 16#ffffffffffffffff, label_to_long),
%% K = (ssh_bits:isize(N)+7) div 8,
%% ?ssh_assert(K == 2*?HLen + 2, decryption_error),
%% C = os2ip(Cb),
%% M = rsadp(Private, C),
%% EM = i2osp(M, K),
%% LHash = ?HASH(L),
%% MLen = K - ?HLen -1,
%% case EM of
%% <<16#00, MaskedSeed:?HLen/binary, MaskedDB:MLen>> ->
%% SeedMask = ?MGF(MaskedDB, ?HLen),
%% Seed = ssh_bits:xor_bits(MaskedSeed, SeedMask),
%% DbMask = ?MGF(Seed, K - ?HLen - 1),
%% DB = ssh_bits:xor_bits(MaskedDB, DbMask),
%% PSLen = K - MLen - 2*?HLen - 2,
%% case DB of
%% <<LHash:?HLen, _PS:PSLen/binary, 16#01, M/binary>> ->
%% M;
%% _ ->
%% exit(decryption_error)
%% end;
%% _ ->
%% exit(decryption_error)
%% end.
%% rsaes_pkcs1_v1_5_encrypt(Public=#ssh_key { public={N,_}}, M) ->
%% K = (ssh_bits:isize(N)+7) div 8,
%% MLen = size(M),
%% ?ssh_assert(MLen =< K - 11, message_to_long),
%% PS = ssh_bits:random(K - MLen - 3),
%% EM = <<16#00,16#02,PS/binary,16#00,M/binary>>,
%% Mc = os2ip(EM),
%% C = rsaep(Public, Mc),
%% i2osp(C, K).
%% rsaes_pkcs1_v1_5_decrypt(Private=#ssh_key { public={N,_},private={_,_}},
%% Cb) ->
%% K = (ssh_bits:isize(N)+7) div 8,
%% CLen = size(Cb),
%% ?ssh_assert(CLen == K andalso K >= 11, decryption_error),
%% C = os2ip(Cb),
%% M = rsadp(Private, C),
%% EM = i2osp(M, K),
%% PSLen = K - CLen - 3,
%% case EM of
%% <<16#00, 16#02, _PS:PSLen/binary, 16#00, M>> ->
%% M;
%% _ ->
%% exit(decryption_error)
%% end.
%% rsassa_pss_sign(Private=#ssh_key { public={N,_},private={_,_}},Mb) ->
%% ModBits = ssh_bits:isize(N),
%% K = (ModBits+7) div 8,
%% EM = emsa_pss_encode(Mb, ModBits - 1),
%% M = os2ip(EM),
%% S = rsasp1(Private, M),
%% i2osp(S, K).
%% rsassa_pss_verify(Public=#ssh_key { public={N,_E}},Mb,Sb) ->
%% ModBits = ssh_bits:isize(N),
%% K = (ModBits+7) div 8,
%% ?ssh_assert(size(Sb) == K, invalid_signature),
%% S = os2ip(Sb),
%% M = rsavp1(Public,S),
%% EMLen = (ModBits-1+7) div 8,
%% EM = i2osp(M, EMLen),
%% emsa_pss_verify(Mb, EM, ModBits-1).
rsassa_pkcs1_v1_5_sign(Private=#ssh_key { public={N,_},private={_,_D}},Mb) ->
K = (ssh_bits:isize(N)+7) div 8,
EM = emsa_pkcs1_v1_5_encode(Mb, K),
M = os2ip(EM),
S = rsasp1(Private, M),
i2osp(S, K).
rsassa_pkcs1_v1_5_verify(Public=#ssh_key { public={N,_E}}, Mb, Sb) ->
K = (ssh_bits:isize(N)+7) div 8,
?ssh_assert(size(Sb) == K, invalid_signature),
S = os2ip(Sb),
M = rsavp1(Public, S),
EM = i2osp(M, K),
%?dbg(true, "verify K=~p S=~w ~n#M=~w~n#EM=~w~n", [K, S, M, EM]),
case emsa_pkcs1_v1_5_encode(Mb, K) of
EM -> ok;
_S ->
{error, invalid_signature}
end.
emsa_pkcs1_v1_5_encode(M, EMLen) ->
H = ?HASH(M),
%% Must use speical xxNull types here!
Alg = #'AlgorithmNull' { algorithm = ?'id-sha1',
parameters = <<>> },
{ok,TCode} = 'PKCS-1':encode('DigestInfoNull',
#'DigestInfoNull'{ digestAlgorithm = Alg,
digest = H }),
T = list_to_binary(TCode),
TLen = size(T),
?ssh_assert(EMLen >= TLen + 11, message_to_short),
PS = ssh_bits:fill_bits(EMLen - TLen - 3, 16#ff),
<<16#00, 16#01, PS/binary, 16#00, T/binary>>.
%% emsa_pss_encode(M, EMBits) ->
%% emsa_pss_encode(M, EMBits, 0).
%% emsa_pss_encode(M, EMBits, SLen) ->
%% ?ssh_assert(size(M) =< 16#ffffffffffffffff, message_to_long),
%% EMLen = (EMBits + 7) div 8,
%% MHash = ?HASH(M),
%% ?ssh_assert(EMLen >= ?HLen + SLen + 2, encoding_error),
%% Salt = ssh_bits:random(SLen),
%% M1 = [16#00,16#00,16#00,16#00,16#00,16#00,16#00,16#00,
%% MHash, Salt],
%% H = ?HASH(M1),
%% PS = ssh_bits:fill_bits(EMLen-SLen-?HLen-2, 0),
%% DB = <<PS/binary, 16#01, Salt/binary>>,
%% DbMask = ?MGF(H, EMLen - ?HLen -1),
%% MaskedDB = ssh_bits:xor_bits(DB, DbMask),
%% ZLen = 8*EMLen - EMBits,
%% NZLen = (8 - (ZLen rem 8)) rem 8,
%% <<_:ZLen, NZ:NZLen, MaskedDB1/binary>> = MaskedDB,
%% MaskedDB2 = <<0:ZLen, NZ:NZLen, MaskedDB1/binary>>,
%% <<MaskedDB2/binary, H/binary, 16#BC>>.
%% emsa_pss_verify(M, EM, EMBits) ->
%% emsa_pss_verify(M, EM, EMBits, 0).
%% emsa_pss_verify(M, EM, EMBits, SLen) ->
%% ?ssh_assert(size(M) =< 16#ffffffffffffffff, message_to_long),
%% EMLen = (EMBits + 7) div 8,
%% MHash = ?HASH(M),
%% ?ssh_assert(EMLen >= ?HLen + SLen + 2, inconsistent),
%% MaskLen = (EMLen - ?HLen - 1)-1,
%% ZLen = 8*EMLen - EMBits,
%% NZLen = (8 - (ZLen rem 8)) rem 8,
%% case EM of
%% <<0:ZLen,Nz:NZLen,MaskedDB1:MaskLen/binary, H:?HLen/binary, 16#BC>> ->
%% MaskedDB = <<0:ZLen,Nz:NZLen,MaskedDB1/binary>>,
%% DbMask = ?MGF(H, EMLen - ?HLen - 1),
%% DB = ssh_bits:xor_bits(MaskedDB, DbMask),
%% PSLen1 = (EMLen - SLen - ?HLen - 2) - 1,
%% PS = ssh_bits:fill_bits(PSLen1, 0),
%% case DB of
%% <<_:ZLen,0:NZLen,PS:PSLen1/binary,16#01,Salt:SLen/binary>> ->
%% M1 = [16#00,16#00,16#00,16#00,16#00,16#00,16#00,16#00,
%% MHash, Salt],
%% case ?HASH(M1) of
%% H -> ok;
%% _ -> exit(inconsistent)
%% end;
%% _ ->
%% exit(inconsistent)
%% end;
%% _ ->
%% exit(inconsistent)
%% end.
%% Mask generating function MGF1
%% mgf1(MGFSeed, MaskLen) ->
%% T = mgf1_loop(0, ((MaskLen + ?HLen -1) div ?HLen) - 1, MGFSeed, ""),
%% <<R:MaskLen/binary, _/binary>> = T,
%% R.
%% mgf1_loop(Counter, N, _, T) when Counter > N ->
%% list_to_binary(T);
%% mgf1_loop(Counter, N, MGFSeed, T) ->
%% C = i2osp(Counter, 4),
%% mgf1_loop(Counter+1, N, MGFSeed, [T, ?HASH([MGFSeed, C])]).
alg_name() ->
"ssh-rsa".
