cryptroot-ask.sh: use key file, if specified in crypttab and present

if a key file is specified in crypttab and present in the initramfs use
it to open the device.

https://bugzilla.redhat.com/show_bug.cgi?id=751640

modules.d/90crypt/cryptroot-ask.sh

@@ -34,7 +34,7 @@ fi
 
 # TODO: improve to support what cmdline does
 if [ -f /etc/crypttab ] && getargbool 1 rd.luks.crypttab -n rd_NO_CRYPTTAB; then
-    while read name dev rest; do
+    while read name dev luksfile rest; do
         # ignore blank lines and comments
         if [ -z "$name" -o "${name#\#}" != "$name" ]; then
             continue
@@ -64,8 +64,13 @@ fi
 # Open LUKS device
 #
 
-info "luksOpen $device $luksname"
+info "luksOpen $device $luksname $luksfile"
 
+if [ -n "$luksfile" -a "$luksfile" != "none" -a -e "$luksfile" ]; then
+    if cryptsetup --key-file "$luksfile" luksOpen "$device" "$luksname"; then
+        ask_passphrase=0
+    fi
+else
     while [ -n "$(getarg rd.luks.key)" ]; do
         if tmp=$(getkey /tmp/luks.keys $device); then
             keydev="${tmp%%:*}"
@@ -95,6 +100,8 @@ while [ -n "$(getarg rd.luks.key)" ]; do
         ask_passphrase=0
         break
     done
+fi
+
 if [ $ask_passphrase -ne 0 ]; then
     luks_open="$(command -v cryptsetup) luksOpen"
     ask_for_password --ply-tries 5 \
@@ -105,7 +112,7 @@ if [ $ask_passphrase -ne 0 ]; then
     unset luks_open
 fi
 
-unset device luksname
+unset device luksname luksfile
 
 # mark device as asked
 >> /tmp/cryptroot-asked-$2