refactor: switch to temporary file for key verification

plugins/ssh-keys/functions

@@ -14,9 +14,14 @@ verify_ssh_key_file() {
   declare desc="Test that public key is valid"
   [[ -s ${DOKKU_ROOT}/.ssh/authorized_keys ]] || dokku_log_fail "No public keys found."
   local key line=0
+  local TMP_KEY_FILE
+  TMP_KEY_FILE=$(mktemp "/tmp/${FUNCNAME[0]}.XXXX")
+  trap 'rm -rf "$TMP_KEY_FILE" >/dev/null' RETURN INT TERM EXIT
+
   while read -r key; do
     line=$((line + 1))
-    ssh-keygen -l -f /dev/stdin <<<"$key" &>/dev/null || dokku_log_fail "${DOKKU_ROOT}/.ssh/authorized_keys line $line failed ssh-keygen check."
+    echo "$key" >"$TMP_KEY_FILE"
+    ssh-keygen -lf "$TMP_KEY_FILE" &>/dev/null || dokku_log_fail "${DOKKU_ROOT}/.ssh/authorized_keys line $line failed ssh-keygen check."
   done <"${DOKKU_ROOT}/.ssh/authorized_keys"
 }