From 2564e317e34fe7f928bf6e234998b295848a5c91 Mon Sep 17 00:00:00 2001 From: Hans Nilsson Date: Thu, 20 Aug 2015 14:40:39 +0200 Subject: ssh: add extra random length padding in packets A new experimental option 'max_random_length_padding', not documented so it might change... --- lib/ssh/src/ssh.erl | 5 +++++ lib/ssh/src/ssh.hrl | 1 + lib/ssh/src/ssh_connection_handler.erl | 10 ++++++++-- lib/ssh/src/ssh_transport.erl | 15 +++++++++++---- lib/ssh/test/ssh_basic_SUITE.erl | 2 ++ 5 files changed, 27 insertions(+), 6 deletions(-) (limited to 'lib/ssh') diff --git a/lib/ssh/src/ssh.erl b/lib/ssh/src/ssh.erl index 5b2e0a988c..132de71aed 100644 --- a/lib/ssh/src/ssh.erl +++ b/lib/ssh/src/ssh.erl @@ -397,6 +397,8 @@ handle_option([{id_string, _ID} = Opt|Rest], SocketOptions, SshOptions) -> handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]); handle_option([{profile, _ID} = Opt|Rest], SocketOptions, SshOptions) -> handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]); +handle_option([{max_random_length_padding, _Bool} = Opt|Rest], SocketOptions, SshOptions) -> + handle_option(Rest, SocketOptions, [handle_ssh_option(Opt) | SshOptions]); handle_option([Opt | Rest], SocketOptions, SshOptions) -> handle_option(Rest, [handle_inet_option(Opt) | SocketOptions], SshOptions). @@ -515,6 +517,9 @@ handle_ssh_option({id_string, random}) -> {id_string, {random,2,5}}; %% 2 - 5 random characters handle_ssh_option({id_string, ID} = Opt) when is_list(ID) -> Opt; +handle_ssh_option({max_random_length_padding, Value} = Opt) when is_integer(Value), + Value =< 255 -> + Opt; handle_ssh_option({profile, Value} = Opt) when is_atom(Value) -> Opt; handle_ssh_option(Opt) -> diff --git a/lib/ssh/src/ssh.hrl b/lib/ssh/src/ssh.hrl index 8df5ee820c..462c98f503 100644 --- a/lib/ssh/src/ssh.hrl +++ b/lib/ssh/src/ssh.hrl @@ -124,6 +124,7 @@ recv_sequence = 0, keyex_key, keyex_info, + random_length_padding = 255, % From RFC 4253 section 6. %% User auth user, diff --git a/lib/ssh/src/ssh_connection_handler.erl b/lib/ssh/src/ssh_connection_handler.erl index c059834b27..180698d741 100644 --- a/lib/ssh/src/ssh_connection_handler.erl +++ b/lib/ssh/src/ssh_connection_handler.erl @@ -1187,7 +1187,10 @@ init_ssh(client = Role, Vsn, Version, Options, Socket) -> opts = Options, userauth_supported_methods = AuthMethods, peer = {PeerName, PeerAddr}, - available_host_keys = supported_host_keys(Role, KeyCb, Options) + available_host_keys = supported_host_keys(Role, KeyCb, Options), + random_length_padding = proplists:get_value(max_random_length_padding, + Options, + (#ssh{})#ssh.random_length_padding) }; init_ssh(server = Role, Vsn, Version, Options, Socket) -> @@ -1207,7 +1210,10 @@ init_ssh(server = Role, Vsn, Version, Options, Socket) -> userauth_methods = AuthMethodsAsList, kb_tries_left = 3, peer = {undefined, PeerAddr}, - available_host_keys = supported_host_keys(Role, KeyCb, Options) + available_host_keys = supported_host_keys(Role, KeyCb, Options), + random_length_padding = proplists:get_value(max_random_length_padding, + Options, + (#ssh{})#ssh.random_length_padding) }. supported_host_keys(client, _, Options) -> diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl index 38a0b7ec7c..9ed6c85ff7 100644 --- a/lib/ssh/src/ssh_transport.erl +++ b/lib/ssh/src/ssh_transport.erl @@ -745,13 +745,20 @@ ssh_packet(Msg, Ssh) -> pack(Data0, #ssh{encrypt_block_size = BlockSize, send_sequence = SeqNum, send_mac = MacAlg, - send_mac_key = MacKey} + send_mac_key = MacKey, + random_length_padding = RandomLengthPadding} = Ssh0) when is_binary(Data0) -> {Ssh1, Data} = compress(Ssh0, Data0), PL = (BlockSize - ((4 + 1 + size(Data)) rem BlockSize)) rem BlockSize, - PaddingLen = if PL < 4 -> PL + BlockSize; - true -> PL - end, + MinPaddingLen = if PL < 4 -> PL + BlockSize; + true -> PL + end, + PadBlockSize = max(BlockSize,4), + MaxExtraBlocks = (max(RandomLengthPadding,MinPaddingLen) - MinPaddingLen) div PadBlockSize, + ExtraPaddingLen = try crypto:rand_uniform(0,MaxExtraBlocks)*PadBlockSize + catch _:_ -> 0 + end, + PaddingLen = MinPaddingLen + ExtraPaddingLen, Padding = ssh_bits:random(PaddingLen), PacketLen = 1 + PaddingLen + size(Data), PacketData = < DataFile = filename:join(UserDir, "rekey.data"), {Pid, Host, Port} = ssh_test_lib:daemon([{system_dir, SystemDir}, + {max_random_length_padding, 0}, {user_dir, UserDir}, {user_passwords, [{"simon", "says"}]}]), @@ -475,6 +476,7 @@ rekey_limit(Config) -> {user, "simon"}, {password, "says"}, {rekey_limit, 2500}, + {max_random_length_padding, 0}, {user_interaction, false}, {silently_accept_hosts, true}]), -- cgit v1.2.3