OpenSSH (GNU/Linux) chroot patch for openssh-5.3p1

To chroot a SSH session into ~/ by using /./ in homedir path

example:
    ~# useradd -d /home/sn00p/./ sn00p
    ~# cat /etc/passwd | grep sn00p
    sn00p:x:10000:10000::/home/sn00p/./:/bin/bash


download & unpack the source:
    ~# cd /usr/src
    ~# wget http://anga.funkfeuer.at/ftp/pub/OpenBSD/OpenSSH/portable/openssh-5.3p1.tar.gz
    ~# tar zxf openssh-5.3p1.tar.gz

download patch & apply to source:
    ~# cd /usr/src/openssh-5.3p1
    ~# wget http://www.cybnet.ch/misc/opensource/openssh-5.3p1-chroot.patch
    ~# patch -p0 < openssh-5.3p1-chroot.patch

configure (options for GNU/Debian) & compile:
    ~# ./configure --prefix=/usr --sysconfdir=/etc/ssh --with-pam
    ~# make 



Original patch by Ricardo Cerqueira <rmcc@clix.pt>
Updated for OpenSSH 5 by Mike Mueller <mike@cybnet.ch>

====================================================================================
diff -u session.c.orig session.c
--- session.c.orig	2009-10-03 19:54:45.000000000 +0200
+++ session.c	2009-10-03 19:57:42.000000000 +0200
@@ -1,4 +1,4 @@
-/* $OpenBSD: session.c,v 1.246 2009/04/17 19:23:06 stevesk Exp $ */
+/* $OpenBSD: session.c,v 1.246-sn0 2009/04/17 19:23:06 stevesk Exp $ */
 /*
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
  *                    All rights reserved
@@ -91,6 +91,8 @@
 #include "monitor_wrap.h"
 #include "sftp.h"
 
+#define CHROOT
+
 #if defined(KRB5) && defined(USE_AFS)
 #include <kafs.h>
 #endif
@@ -1457,6 +1459,11 @@
 {
 	char *chroot_path, *tmp;
 
+#ifdef CHROOT
+    char *user_dir;
+    char *new_root;
+#endif
+
 #ifdef WITH_SELINUX
 	/* Cache selinux status for later use */
 	(void)ssh_selinux_enabled();
@@ -1499,6 +1506,27 @@
 			exit(1);
 		}
 		endgrent();
+
+#ifdef CHROOT
+               user_dir = xstrdup(pw->pw_dir);
+               new_root = user_dir + 1;
+
+               while((new_root = strchr(new_root, '.')) != NULL) {
+                   new_root--;
+                   if (strncmp(new_root, "/./", 3) == 0) {
+                       *new_root = '\0';
+                       new_root += 2;
+
+                       if (chroot(user_dir) != 0)
+                           fatal("Couldn't chroot to user directory %s", user_dir);
+
+                       pw->pw_dir = new_root;
+                       break;
+                   }
+                   new_root += 2;
+               }
+#endif
+
 # ifdef USE_PAM
 		/*
 		 * PAM credentials may take the form of supplementary groups.