From 84adefa331c4159d432d22840663c38f155cd4c1 Mon Sep 17 00:00:00 2001
From: Erlang/OTP <otp@erlang.org>
Date: Fri, 20 Nov 2009 14:54:40 +0000
Subject: The R13B03 release.

---
 lib/ssh/src/ssh_dsa.erl | 95 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100755 lib/ssh/src/ssh_dsa.erl

(limited to 'lib/ssh/src/ssh_dsa.erl')

diff --git a/lib/ssh/src/ssh_dsa.erl b/lib/ssh/src/ssh_dsa.erl
new file mode 100755
index 0000000000..ec24fbcd01
--- /dev/null
+++ b/lib/ssh/src/ssh_dsa.erl
@@ -0,0 +1,95 @@
+%%
+%% %CopyrightBegin%
+%% 
+%% Copyright Ericsson AB 2005-2009. 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: dsa public-key sign and verify
+
+-module(ssh_dsa).
+
+-export([verify/3]).
+-export([sign/2]).
+-export([alg_name/0]).
+
+-include("ssh.hrl").
+
+%% start() ->
+%%     crypto:start().
+
+%% sign_file(File, Opts) ->
+%%     start(),
+%%     {ok,Bin} = file:read_file(File),
+%%     {ok,Key} = ssh_file:private_host_dsa_key(user, Opts),
+%%     sign(Key, Bin).
+
+%% verify_file(File, Sig) ->
+%%     start(),
+%%     {ok,Bin} = file:read_file(File),
+%%     {ok,Key} = ssh_file:public_host_key(user, dsa),
+%%     verify(Key, Bin, Sig).
+
+sign(_Private=#ssh_key { private={P,Q,G,X} },Mb) ->
+    K = ssh_bits:irandom(160) rem Q,
+    R = ssh_math:ipow(G, K, P) rem Q,
+    Ki = ssh_math:invert(K, Q),
+    <<M:160/big-unsigned-integer>> = crypto:sha(Mb),
+    S = (Ki * (M + X*R)) rem Q,
+    <<R:160/big-unsigned-integer, S:160/big-unsigned-integer>>.
+
+
+%% the paramiko client sends a bad sig sometimes, 
+%% instead of crashing, we nicely return error, the
+%% typcally manifests itself as Sb being 39 bytes
+%% instead of 40.
+
+verify(Public, Mb, Sb) ->
+    case catch xverify(Public, Mb, Sb) of
+	{'EXIT', _Reason} ->
+            %store({Public, Mb, Sb, _Reason}),
+	    {error, inconsistent_key};
+	ok ->
+  	    %store({Public, Mb, Sb, ok})
+	    ok
+    end.
+
+%% store(Term) ->
+%%     {ok, Fd} = file:open("/tmp/dsa", [append]),
+%%     io:format(Fd, "~p~n~n~n", [Term]),
+%%     file:close(Fd).
+
+
+xverify(_Public=#ssh_key { public={P,Q,G,Y} },Mb,Sb) ->
+    <<R0:160/big-unsigned-integer, S0:160/big-unsigned-integer>> = Sb,
+    ?ssh_assert(R0 >= 0 andalso R0 < Q andalso
+		S0 >= 0 andalso S0 < Q, out_of_range),
+    W = ssh_math:invert(S0,Q),
+    <<M0:160/big-unsigned-integer>> = crypto:sha(Mb),
+    U1 = (M0*W) rem Q,
+    U2 = (R0*W) rem Q,
+    T1 = ssh_math:ipow(G,U1,P),
+    T2 = ssh_math:ipow(Y,U2,P),
+    V = ((T1*T2) rem P) rem Q,
+    if V == R0 ->
+	    ok;
+       true ->
+	    {error, inconsistent_key}
+    end.
+
+alg_name() ->
+    "ssh-dss".
-- 
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