From: Russ Allbery <rra@debian.org>
Date: Mon, 28 Jan 2019 20:15:30 -0800
Subject: Check command line after chroot

When a command was configured with a chroot, rssh did not check
the safety of the command line after chroot, allowing various
vectors of remote code execution inside the chroot environment.
Perform the same check after chroot as is performed before running
the command when a chroot is not configured.
---
 rssh_chroot_helper.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rssh_chroot_helper.c b/rssh_chroot_helper.c
index 8a35cdc..73d8c7b 100644
--- a/rssh_chroot_helper.c
+++ b/rssh_chroot_helper.c
@@ -218,6 +218,12 @@ int main( int argc, char **argv )
 		ch_fatal_error("build_arg_vector()", argv[2],
 				"bad expansion");
 
+	/* check the command for safety */
+	if ( !check_command_line(argvec, &opts) ){
+		fprintf(stderr, "\n");
+		exit(1);
+	}
+
 	/* 
 	 * This is the old way to figure out what program to run.  Since we're
 	 * re-parsing the config file in rssh_chroot helper, we could get rid