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authorHans Nilsson <[email protected]>2017-12-14 12:54:16 +0100
committerHans Nilsson <[email protected]>2017-12-14 12:54:16 +0100
commit8aeec7d6748dab5924713b58e3011dc62d331fa5 (patch)
tree8d6076cd86379165f56c8aadebae8d920c63ef1d
parent44b09e036b31b29dddc3b178e8f6b9fc96a9a874 (diff)
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ssh: Special treatment of OpenSSH clients >= 7.2 rsa-sha2-* public keys
Thoose clients signs with sha instead of sha2-*. Try first to verify with the correct one, and if that fails, retry with sha1.
-rw-r--r--lib/ssh/src/ssh_auth.erl9
-rw-r--r--lib/ssh/src/ssh_transport.erl18
2 files changed, 17 insertions, 10 deletions
diff --git a/lib/ssh/src/ssh_auth.erl b/lib/ssh/src/ssh_auth.erl
index 894877f8bf..03d264745b 100644
--- a/lib/ssh/src/ssh_auth.erl
+++ b/lib/ssh/src/ssh_auth.erl
@@ -304,11 +304,10 @@ handle_userauth_request(#ssh_msg_userauth_request{user = User,
SigWLen/binary>>
},
SessionId,
- #ssh{opts = Opts,
- userauth_supported_methods = Methods} = Ssh) ->
+ #ssh{userauth_supported_methods = Methods} = Ssh) ->
case verify_sig(SessionId, User, "ssh-connection",
- BAlg, KeyBlob, SigWLen, Opts) of
+ BAlg, KeyBlob, SigWLen, Ssh) of
true ->
{authorized, User,
ssh_transport:ssh_packet(
@@ -518,7 +517,7 @@ pre_verify_sig(User, KeyBlob, Opts) ->
false
end.
-verify_sig(SessionId, User, Service, AlgBin, KeyBlob, SigWLen, Opts) ->
+verify_sig(SessionId, User, Service, AlgBin, KeyBlob, SigWLen, #ssh{opts = Opts} = Ssh) ->
try
Alg = binary_to_list(AlgBin),
{KeyCb,KeyCbOpts} = ?GET_OPT(key_cb, Opts),
@@ -529,7 +528,7 @@ verify_sig(SessionId, User, Service, AlgBin, KeyBlob, SigWLen, Opts) ->
<<?UINT32(AlgSigLen), AlgSig:AlgSigLen/binary>> = SigWLen,
<<?UINT32(AlgLen), _Alg:AlgLen/binary,
?UINT32(SigLen), Sig:SigLen/binary>> = AlgSig,
- ssh_transport:verify(PlainText, ssh_transport:sha(Alg), Sig, Key)
+ ssh_transport:verify(PlainText, ssh_transport:sha(Alg), Sig, Key, Ssh)
catch
_:_ ->
false
diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl
index 90a94a7e86..154894cda8 100644
--- a/lib/ssh/src/ssh_transport.erl
+++ b/lib/ssh/src/ssh_transport.erl
@@ -51,7 +51,7 @@
extract_public_key/1,
ssh_packet/2, pack/2,
valid_key_sha_alg/2,
- sha/1, sign/3, verify/4]).
+ sha/1, sign/3, verify/5]).
%%% For test suites
-export([pack/3]).
@@ -825,7 +825,7 @@ extract_public_key(#{engine:=_, key_id:=_, algorithm:=Alg} = M) ->
verify_host_key(#ssh{algorithms=Alg}=SSH, PublicKey, Digest, {AlgStr,Signature}) ->
case atom_to_list(Alg#alg.hkey) of
AlgStr ->
- case verify(Digest, sha(Alg#alg.hkey), Signature, PublicKey) of
+ case verify(Digest, sha(Alg#alg.hkey), Signature, PublicKey, SSH) of
false ->
{error, bad_signature};
true ->
@@ -1288,7 +1288,7 @@ mk_dss_sig(DerSignature) ->
<<R:160/big-unsigned-integer, S:160/big-unsigned-integer>>.
-verify(PlainText, HashAlg, Sig, {_, #'Dss-Parms'{}} = Key) ->
+verify(PlainText, HashAlg, Sig, {_, #'Dss-Parms'{}} = Key, _) ->
case Sig of
<<R:160/big-unsigned-integer, S:160/big-unsigned-integer>> ->
Signature = public_key:der_encode('Dss-Sig-Value', #'Dss-Sig-Value'{r = R, s = S}),
@@ -1296,7 +1296,7 @@ verify(PlainText, HashAlg, Sig, {_, #'Dss-Parms'{}} = Key) ->
_ ->
false
end;
-verify(PlainText, HashAlg, Sig, {#'ECPoint'{},_} = Key) ->
+verify(PlainText, HashAlg, Sig, {#'ECPoint'{},_} = Key, _) ->
case Sig of
<<?UINT32(Rlen),R:Rlen/big-signed-integer-unit:8,
?UINT32(Slen),S:Slen/big-signed-integer-unit:8>> ->
@@ -1306,7 +1306,15 @@ verify(PlainText, HashAlg, Sig, {#'ECPoint'{},_} = Key) ->
_ ->
false
end;
-verify(PlainText, HashAlg, Sig, Key) ->
+
+verify(PlainText, HashAlg, Sig, #'RSAPublicKey'{}=Key, #ssh{role = server,
+ c_version = "SSH-2.0-OpenSSH_7."++_})
+ when HashAlg == sha256; HashAlg == sha512 ->
+ %% Public key signing bug in in OpenSSH >= 7.2
+ public_key:verify(PlainText, HashAlg, Sig, Key)
+ orelse public_key:verify(PlainText, sha, Sig, Key);
+
+verify(PlainText, HashAlg, Sig, Key, _) ->
public_key:verify(PlainText, HashAlg, Sig, Key).