Try to inherit key (encryptionroot) in duplicate_snapshot

A raw send (necessary to preserve properties and avoid a decryption pass
on encrypted filesystems) will cause the target to be its own encryption
root, which is surprising and probably undesirable. If the source is not
its own encryption root, make the target inherit its key from a (common)
parent.

Closes #225.

Author: ahesford

90zfsbootmenu/zfsbootmenu-lib.sh

@@ -792,7 +792,7 @@ kexec_kernel() {
 
 duplicate_snapshot() {
   local selected target target_parent pool recv_args
-  local encroot keylocation
+  local fs encroot keylocation
 
   selected="${1}"
   if [ -z "$selected" ]; then
@@ -825,15 +825,19 @@ duplicate_snapshot() {
     CLEAR_SCREEN=0 load_key "${target_parent}"
   fi
 
-  recv_args=( "-u" "-o" "canmount=noauto" "-o" "mountpoint=/" "${target}" )
+  recv_args=( "-u" "-o" "canmount=noauto" "-o" "mountpoint=/" )
 
-  if encroot="$( be_has_encroot "${selected}" )" ; then
+  if encroot="$( be_has_encroot "${selected}" )"; then
     keylocation="$( zfs get -H -o value keylocation "${encroot}" 2>/dev/null )"
     if [ -n "${keylocation}" ] && [ "${keylocation}" != "-" ]; then
       recv_args+=( "-o" "keylocation=${keylocation}" )
     fi
   fi
 
+  recv_args+=( "${target}" )
+
+  echo ""
+
   (
     trap 'exit 0' SIGINT
     if command -v mbuffer >/dev/null 2>&1; then
@@ -842,7 +846,26 @@ duplicate_snapshot() {
     else
       zfs send -p -w "${selected}" | zfs recv "${recv_args[@]}"
     fi
-  )
+  ) || return
+
+  echo ""
+
+  # If the source was encrypted, the raw send will have created a new
+  # encryption root at the target. Move the encryption root to the parent if
+  # the source was not its own encryption root.
+
+  fs="${selected%@*}"
+  if [ -z "${encroot}" ] || [ "${encroot}" = "${fs}" ]; then
+    return 0
+  fi
+
+  if encroot="$( be_has_encroot "${target}" )"; then
+    if [ "${encroot}" = "${target}" ]; then
+      # Key must be loaded before changing
+      CLEAR_SCREEN=0 load_key "${target}"
+      zfs change-key -i "${target}"
+    fi
+  fi
 }
 
 # arg1: snapshot name
@@ -2013,14 +2036,14 @@ set_ro_pool() {
 }
 
 
-# arg1: ZFS filesystem
+# arg1: ZFS filesystem or snapshot
 # prints: name of encryption root, if present
 # returns: 0 if system has an encryption root, 1 otherwise
 
 be_has_encroot() {
   local fs pool encroot
 
-  fs="${1}"
+  fs="${1%@*}"
   if [ -z "${fs}" ]; then
     zerror "fs is undefined"
     return 1