From b4ad3a9eb7a1b375d2dbbf93069ea9ae038d121f Mon Sep 17 00:00:00 2001
From: Hans Nilsson <hans@erlang.org>
Date: Wed, 14 Nov 2018 12:57:46 +0100
Subject: ssh: Make host and user key pre-checking better

This will prevent crashes in ssh_file for public key types which have no passphrase option although being supported.
Also centralize host key checking to avoid code duplication. This was already done for user keys.
---
 lib/ssh/src/ssh_connection_handler.erl | 50 +++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 25 deletions(-)

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

diff --git a/lib/ssh/src/ssh_connection_handler.erl b/lib/ssh/src/ssh_connection_handler.erl
index e23df6ceca..7c87591cf2 100644
--- a/lib/ssh/src/ssh_connection_handler.erl
+++ b/lib/ssh/src/ssh_connection_handler.erl
@@ -1685,18 +1685,19 @@ peer_role(client) -> server;
 peer_role(server) -> client.
 
 %%--------------------------------------------------------------------
-available_hkey_algorithms(Role, Options) ->
-    KeyCb = ?GET_OPT(key_cb, Options),
-    case [A || A <- available_hkey_algos(Options),
-               (Role==client) orelse available_host_key(KeyCb, A, Options)
-         ] of
-        
-        [] when Role==client ->
-	    error({shutdown, "No public key algs"});
-
-        [] when Role==server ->
-	    error({shutdown, "No host key available"});
+available_hkey_algorithms(client, Options) ->
+    case available_hkey_algos(Options) of
+        [] ->
+            error({shutdown, "No public key algs"});
+        Algs ->
+	    [atom_to_list(A) || A<-Algs]
+    end;
 
+available_hkey_algorithms(server, Options) ->
+    case [A || A <- available_hkey_algos(Options),
+               is_usable_host_key(A, Options)] of
+        [] ->
+            error({shutdown, "No host key available"});
 	Algs ->
 	    [atom_to_list(A) || A<-Algs]
     end.
@@ -1712,18 +1713,6 @@ available_hkey_algos(Options) ->
     AvailableAndSupported.
 
 
-%% Alg :: atom()
-available_host_key({KeyCb,KeyCbOpts}, Alg, Opts) ->
-    UserOpts = ?GET_OPT(user_options, Opts),
-    case KeyCb:host_key(Alg, [{key_cb_private,KeyCbOpts}|UserOpts]) of
-        {ok,Key} ->
-            %% Check the key - the KeyCb may be a buggy plugin
-            ssh_transport:valid_key_sha_alg(Key, Alg);
-        _ ->
-            false
-    end.
-
-
 send_msg(Msg, State=#data{ssh_params=Ssh0}) when is_tuple(Msg) ->
     {Bytes, Ssh} = ssh_transport:ssh_packet(Msg, Ssh0),
     send_bytes(Bytes, State),
@@ -1843,10 +1832,21 @@ ext_info(_, D0) ->
     D0.
 
 %%%----------------------------------------------------------------
-is_usable_user_pubkey(A, Ssh) ->
-    case ssh_auth:get_public_key(A, Ssh) of
+is_usable_user_pubkey(Alg, Ssh) ->
+    try ssh_auth:get_public_key(Alg, Ssh) of
         {ok,_} -> true;
         _ -> false
+    catch
+        _:_ -> false
+    end.
+
+%%%----------------------------------------------------------------
+is_usable_host_key(Alg, Opts) ->
+    try ssh_transport:get_host_key(Alg, Opts)
+    of
+        _PrivHostKey -> true
+    catch
+        _:_ -> false
     end.
 
 %%%----------------------------------------------------------------
-- 
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