dracut: added new module ecryptfs

This module mounts an eCryptfs filesystem from the initial ramdisk using an
encrypted key.

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Acked-by: Gianluca Ramunno <ramunno@polito.it>

dracut.kernel.7.xml

@@ -724,6 +724,12 @@ rd.znet=ctc,0.0.0600,0.0.0601,0.0.0602,protocol=bar</programlisting></para>
             <para>Set the path name of the EVM key. e.g.: <programlisting>evmkey=/etc/keys/evm-trusted.blob</programlisting></para>
           </listitem>
         </varlistentry>
+        <varlistentry>
+          <term><envar>ecryptfskey=</envar><replaceable>&lt;eCryptfs key path name&gt;</replaceable></term>
+          <listitem>
+            <para>Set the path name of the eCryptfs key. e.g.: <programlisting>ecryptfskey=/etc/keys/ecryptfs-trusted.blob</programlisting></para>
+          </listitem>
+        </varlistentry>
       </variablelist>
     </refsect2>
     <refsect2>

modules.d/98ecryptfs/README

@@ -0,0 +1,50 @@
+# Directions for creating the encrypted key that will be used to mount an
+# eCryptfs filesystem
+
+# Create the eCryptfs key (encrypted key type)
+#
+# The encrypted key type supports two formats: the 'default' format allows
+# to generate a random symmetric key of the length specified, the 'ecryptfs'
+# format generates an authentication token for the eCryptfs filesystem,
+# which contains a randomly generated key. Two requirements for the latter
+# format is that the key description must contain exactly 16 hexadecimal
+# characters and that the encrypted key length must be equal to 64.
+$ keyctl add encrypted 1000100010001000 "new ecryptfs trusted:kmk-trusted 64" @u
+782117972
+
+# Save the encrypted key
+$ su -c 'keyctl pipe `keyctl search @u encrypted 1000100010001000` > /etc/keys/ecryptfs-trusted.blob'
+
+# The eCryptfs key path name can be set in one of the following ways (specified in
+# the order in which the variable is overwritten):
+
+1) use the default value:
+--------------------------------------------------------------------------
+ECRYPTFSKEY="/etc/keys/ecryptfs-trusted.blob"
+--------------------------------------------------------------------------
+
+2) create the configuration file '/etc/sysconfig/ecryptfs' and set the ECRYPTFSKEY
+variable;
+
+3) specify the eCryptfs key path name in the 'ecryptfskey=' parameter of the kernel command
+line.
+
+# The configuration file '/etc/sysconfig/ecryptfs' is also used to specify
+# more options for mounting the eCryptfs filesystem:
+
+ECRYPTFSSRCDIR: existent directory in the lower root filesystem;
+ECRYPTFSDSTDIR: mount point directory for the eCryptfs filesystem (the directory must be
+                created in the root filesystem before rebooting the platform);
+ECRYPTFS_EXTRA_MOUNT_OPTS: extra mount options for the eCryptfs filesystem (the 'ecryptfs_sig'
+                           option is automatically added by the dracut script).
+
+# Example of the configuration file:
+----------- '/etc/sysconfig/ecryptfs' (with default values) -----------
+ECRYPTFS_KEY="/etc/keys/ecryptfs-trusted.blob"
+ECRYPTFSSRCDIR="/secret"
+ECRYPTFSDSTDIR="${ECRYPTFSSRCDIR}"
+ECRYPTFS_EXTRA_MOUNT_OPTS=""
+-----------------------------------------------------------------------
+
+# If the variable ECRYPTFSDSTDIR is not specified in the configuration file,
+# its value will be equal to that of ECRYPTFSSRCDIR.

modules.d/98ecryptfs/ecryptfs-mount.sh

@@ -0,0 +1,100 @@
+#!/bin/sh
+# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
+# ex: ts=8 sw=4 sts=4 et filetype=sh
+
+# Licensed under the GPLv2
+#
+# Copyright (C) 2011 Politecnico di Torino, Italy
+#                    TORSEC group -- http://security.polito.it
+# Roberto Sassu <roberto.sassu@polito.it>
+
+ECRYPTFSCONFIG="${NEWROOT}/etc/sysconfig/ecryptfs"
+ECRYPTFSKEYTYPE="encrypted"
+ECRYPTFSKEYDESC="1000100010001000"
+ECRYPTFSKEYID=""
+ECRYPTFSSRCDIR="/secret"
+ECRYPTFS_EXTRA_MOUNT_OPTS=""
+
+load_ecryptfs_key()
+{
+    # override the eCryptfs key path name from the 'ecryptfskey=' parameter in the kernel
+    # command line
+    ECRYPTFSKEYARG=$(getarg ecryptfskey=)
+    [ $? -eq 0 ] && \
+        ECRYPTFSKEY=${ECRYPTFSKEYARG}
+
+    # set the default value
+    [ -z "${ECRYPTFSKEY}" ] && \
+        ECRYPTFSKEY="/etc/keys/ecryptfs-trusted.blob";
+
+    # set the eCryptfs key path name
+    ECRYPTFSKEYPATH="${NEWROOT}${ECRYPTFSKEY}"
+
+    # check for eCryptfs encrypted key's existence
+    if [ ! -f "${ECRYPTFSKEYPATH}" ]; then
+        if [ "${RD_DEBUG}" = "yes" ]; then
+            info "eCryptfs: key file not found: ${ECRYPTFSKEYPATH}"
+        fi
+        return 1
+    fi
+
+    # read the eCryptfs encrypted key blob
+    KEYBLOB=$(cat ${ECRYPTFSKEYPATH})
+
+    # load the eCryptfs encrypted key blob
+    ECRYPTFSKEYID=$(keyctl add ${ECRYPTFSKEYTYPE} ${ECRYPTFSKEYDESC} "load ${KEYBLOB}" @u)
+    [ $? -eq 0 ] || {
+        info "eCryptfs: failed to load the eCryptfs key: ${ECRYPTFSKEYDESC}";
+        return 1;
+    }
+
+    return 0
+}
+
+unload_ecryptfs_key()
+{
+    # unlink the eCryptfs encrypted key
+    keyctl unlink ${ECRYPTFSKEYID} @u || {
+        info "eCryptfs: failed to unlink the eCryptfs key: ${ECRYPTFSKEYDESC}";
+        return 1;
+    }
+
+    return 0
+}
+
+mount_ecryptfs()
+{
+    # read the configuration from the config file
+    [ -f "${ECRYPTFSCONFIG}" ] && \
+        . ${ECRYPTFSCONFIG}
+
+    # load the eCryptfs encrypted key
+    load_ecryptfs_key || return 1
+
+    # set the default value for ECRYPTFSDSTDIR
+    [ -z "${ECRYPTFSDSTDIR}" ] && \
+        ECRYPTFSDSTDIR=${ECRYPTFSSRCDIR}
+
+    # set the eCryptfs filesystem mount point
+    ECRYPTFSSRCMNT="${NEWROOT}${ECRYPTFSSRCDIR}"
+    ECRYPTFSDSTMNT="${NEWROOT}${ECRYPTFSDSTDIR}"
+
+    # build the mount options variable
+    ECRYPTFS_MOUNT_OPTS="ecryptfs_sig=${ECRYPTFSKEYDESC}"
+    [ ! -z "${ECRYPTFS_EXTRA_MOUNT_OPTS}" ] && \
+        ECRYPTFS_MOUNT_OPTS="${ECRYPTFS_MOUNT_OPTS},${ECRYPTFS_EXTRA_MOUNT_OPTS}"
+
+    # mount the eCryptfs filesystem
+    info "Mounting the configured eCryptfs filesystem"
+    mount -i -t ecryptfs -o${ECRYPTFS_MOUNT_OPTS} ${ECRYPTFSSRCMNT} ${ECRYPTFSDSTMNT} >/dev/null || {
+        info "eCryptfs: mount of the eCryptfs filesystem failed";
+        return 1;
+    }
+
+    # unload the eCryptfs encrypted key
+    unload_ecryptfs_key || return 1
+
+    return 0
+}
+
+mount_ecryptfs

modules.d/98ecryptfs/module-setup.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
+# ex: ts=8 sw=4 sts=4 et filetype=sh
+
+check() {
+    return 0
+}
+
+depends() {
+    echo masterkey
+    return 0
+}
+
+installkernel() {
+    instmods ecryptfs
+}
+
+install() {
+    inst_hook pre-pivot 63 "$moddir/ecryptfs-mount.sh"
+}