From 8215ea28fa2f699499b64d6f2c712e068b199390 Mon Sep 17 00:00:00 2001
From: Hans Nilsson <hans@erlang.org>
Date: Fri, 11 Nov 2016 16:59:08 +0100
Subject: ssh: Add fun and fingerprint to option 'silently_accept_host'

---
 lib/ssh/doc/src/ssh.xml       | 14 ++++++++++++--
 lib/ssh/src/ssh.erl           |  9 +++++++++
 lib/ssh/src/ssh_transport.erl | 16 ++++++++++------
 3 files changed, 31 insertions(+), 8 deletions(-)

(limited to 'lib/ssh')

diff --git a/lib/ssh/doc/src/ssh.xml b/lib/ssh/doc/src/ssh.xml
index ef9f7cbd9b..6b49f89449 100644
--- a/lib/ssh/doc/src/ssh.xml
+++ b/lib/ssh/doc/src/ssh.xml
@@ -175,11 +175,21 @@
 	    supplied with this option.
 	    </p>
 	  </item>
-          <tag><c><![CDATA[{silently_accept_hosts, boolean()}]]></c></tag>
+          <tag><c><![CDATA[{silently_accept_hosts, boolean() | accept_fun() | {crypto:digest_type(), accept_fun()} }]]></c>
+	  <br/>
+	  <c><![CDATA[accept_fun() :: fun(PeerName::string(), FingerPrint::string()) -> boolean()]]></c>
+	  </tag>
 	  <item>
 	    <p>When <c>true</c>, hosts are added to the
 	    file <c><![CDATA[known_hosts]]></c> without asking the user.
-	    Defaults to <c>false</c>.
+	    Defaults to <c>false</c> which will give a user question on stdio of whether to accept or reject a previously
+	    unseen host.</p>
+	    <p>If the option value is has an <c>accept_fun()</c>, that fun will called with the arguments
+	    <c>(PeerName, PeerHostKeyFingerPrint)</c>.  The fingerprint is calculated on the Peer's Host Key with
+	    <seealso marker="public_key:public_key#ssh_hostkey_fingerprint-1">public_key:ssh_hostkey_fingerprint/1</seealso>.
+	    </p>
+	    <p>If the <c>crypto:digest_type()</c> is present, the fingerprint is calculated with that digest type by the function
+	    <seealso marker="public_key:public_key#ssh_hostkey_fingerprint-2">public_key:ssh_hostkey_fingerprint/2</seealso>.
 	    </p>
 	  </item>
 	  <tag><c><![CDATA[{user_interaction, boolean()}]]></c></tag>
diff --git a/lib/ssh/src/ssh.erl b/lib/ssh/src/ssh.erl
index 1d7be3547b..31e343e81b 100644
--- a/lib/ssh/src/ssh.erl
+++ b/lib/ssh/src/ssh.erl
@@ -617,6 +617,15 @@ handle_ssh_option({user_dir_fun, Value} = Opt) when is_function(Value) ->
     Opt;
 handle_ssh_option({silently_accept_hosts, Value} = Opt) when is_boolean(Value) ->
     Opt;
+handle_ssh_option({silently_accept_hosts, Value} = Opt) when is_function(Value,2) ->
+    Opt;
+handle_ssh_option({silently_accept_hosts, {DigestAlg,Value}} = Opt) when is_function(Value,2) ->
+    case lists:member(DigestAlg, [md5, sha, sha224, sha256, sha384, sha512]) of
+	true ->
+	    Opt;
+	false ->
+	    throw({error, {eoptions, Opt}})
+    end;
 handle_ssh_option({user_interaction, Value} = Opt) when is_boolean(Value) ->
     Opt;
 handle_ssh_option({preferred_algorithms,[_|_]} = Opt) ->
diff --git a/lib/ssh/src/ssh_transport.erl b/lib/ssh/src/ssh_transport.erl
index 15b80de30a..21ba34506a 100644
--- a/lib/ssh/src/ssh_transport.erl
+++ b/lib/ssh/src/ssh_transport.erl
@@ -734,12 +734,16 @@ public_algo({#'ECPoint'{},{namedCurve,OID}}) ->
     list_to_atom("ecdsa-sha2-" ++ binary_to_list(Curve)).
 
 
-accepted_host(Ssh, PeerName, Opts) ->
+accepted_host(Ssh, PeerName, Public, Opts) ->
     case proplists:get_value(silently_accept_hosts, Opts, false) of
+	F when is_function(F,2) ->
+	    true == (catch F(PeerName, public_key:ssh_hostkey_fingerprint(Public)));
+	{DigestAlg,F} when is_function(F,2) ->
+	    true == (catch F(PeerName, public_key:ssh_hostkey_fingerprint(DigestAlg,Public)));
 	true ->
-	    yes;
+	    true;
 	false ->
-	    yes_no(Ssh, "New host " ++ PeerName ++ " accept")
+	    yes == yes_no(Ssh, "New host " ++ PeerName ++ " accept")
     end.
 
 known_host_key(#ssh{opts = Opts, key_cb = Mod, peer = Peer} = Ssh, 
@@ -749,10 +753,10 @@ known_host_key(#ssh{opts = Opts, key_cb = Mod, peer = Peer} = Ssh,
 	true ->
 	    ok;
 	false ->
-	    case accepted_host(Ssh, PeerName, Opts) of
-		yes ->
+	    case accepted_host(Ssh, PeerName, Public, Opts) of
+		true ->
 		    Mod:add_host_key(PeerName, Public, Opts);
-		no ->
+		false ->
 		    {error, rejected}
 	    end
     end.
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