[OpenWrt-Devel] [PATCH v6] ppp: add new protocol PPPoSSH.

[Yousong Zhou]

This patch adds protocol support for PPP over SSH.  The protocol name is
'pppossh' with the following options.

 - server, SSH server name.  Required
 - port, SSH server port.  Defaults to 22.
 - sshuser, SSH login username.  Required.
 - identity, list of client private key files.  ~/.ssh/id_{rsa,dsa} will
   be used if no identity file was specified and at least one of them must
   be valid for the public key authentication to proceed.
 - ipaddr, local ip address to be assigned.
 - peeraddr, peer ip address to be assigned.
 - ssh_options, extra ssh client options.

Because the protocol script file ppp.sh will be called with $HOME set to
'/', we need to explicitly set it to the right value so that dropbear
client can read '~/known_hosts' correctly.

Signed-off-by: Yousong Zhou <yszhou4tech at gmail.com>
---
I can make this a standalone package (maybe in packages feeds) if that is more
preferable.

v5 -> v6

    - Specify 'localip:peerip' directly without `ippair' variable.

v4 -> v5

    - Remove `acceptunknown' option.  For dropbear client `-y' option can be
      used, and for OpenSSH client it's '-o StrictHostKeyChecking xx'.  Both of
      them can be specified through the `ssh_options'.
    - Make variable `pty' local.

v3 -> v4

    - Use default identity files only when no explicit key files were
      specified.
    - Added a new option `ssh_options' which will be added as part of ssh
      client options.
    - Change the type of `port' option to int.
    - Change the type of `identity` option to array type.

v2 -> v3

    - Change type of acceptunknown to boolean.
    - Squeeze multiple calls to proto_config_add_string to one.

v1 -> v2

    - Use common option names as suggested by jow and nbd.
    - Default to using ~/.ssh/id_{rsa,dsa} as the identity file.
    - Set $HOME to correct value for the current user instead of unset it.

 package/network/services/ppp/files/ppp.sh |   54 +++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/package/network/services/ppp/files/ppp.sh b/package/network/services/ppp/files/ppp.sh
index f07b11f..6266cc4 100755
--- a/package/network/services/ppp/files/ppp.sh
+++ b/package/network/services/ppp/files/ppp.sh
@@ -212,10 +212,64 @@ proto_pptp_teardown() {
 	ppp_generic_teardown "$@"
 }
 
+proto_pppossh_init_config() {
+	ppp_generic_init_config
+	proto_config_add_string server sshuser ipaddr peeraddr ssh_options
+	proto_config_add_string 'identity:list(string)'
+	proto_config_add_int port
+	available=1
+	no_device=1
+}
+
+proto_pppossh_setup() {
+	local config="$1"
+	local iface="$2"
+	local user="$(id -nu)"
+	local home=$(sh -c "echo ~$user")
+	local ip serv_addr errmsg
+	local opts pty
+
+	json_get_vars port sshuser identity ipaddr peeraddr ssh_options
+	json_get_var server server && {
+		for ip in $(resolveip -t 5 "$server"); do
+			( proto_add_host_dependency "$config" "$ip" )
+			serv_addr=1
+		done
+	}
+	[ -n "$serv_addr" ] || errmsg="${errmsg}Could not resolve $server.\n"
+	[ -n "$sshuser" ] || errmsg="${errmsg}Missing sshuser option.\n"
+	[ -z "$identity" ] && identity="'$home/.ssh/id_rsa' '$home/.ssh/id_dsa'"
+	{
+		local fn
+		for fn in $identity; do
+			[ -f "$fn" ] && opts="$opts -i $fn"
+		done
+		[ -n "$opts" ] || errmsg="${errmsg}Cannot find valid identity file.\n"
+	}
+	[ -n "$errmsg" ] && {
+		echo -ne "$errmsg"
+		sleep 5
+		proto_setup_failed "$config"
+		exit 1
+	}
+	opts="$opts ${port:+-p $port}"
+	opts="$opts ${ssh_options}"
+	opts="$opts $sshuser@$server"
+	pty="env 'HOME=$home' /usr/bin/ssh $opts pppd nodetach notty noauth"
+
+	ppp_generic_setup "$config" \
+		noauth pty "$pty" "$ipaddr:$peeraddr"
+}
+
+proto_pppossh_teardown() {
+	ppp_generic_teardown "$@"
+}
+
 [ -n "$INCLUDE_ONLY" ] || {
 	add_protocol ppp
 	[ -f /usr/lib/pppd/*/rp-pppoe.so ] && add_protocol pppoe
 	[ -f /usr/lib/pppd/*/pppoatm.so ] && add_protocol pppoa
 	[ -f /usr/lib/pppd/*/pptp.so ] && add_protocol pptp
+	[ -x /usr/bin/ssh ] && add_protocol pppossh
 }
 
-- 
1.7.10.4
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