stand/lua: Add optional GELI passphrase prompt

Prompt for GELI passphrase when geom_eli_passphrase_prompt has been set to
"YES" in loader.conf(5).

This entailed breaking out the password prompt into its own function that
can be reused between the password compare bits and this prompt that simply
takes the entered password and passes it along in the environment as
kern.geom.eli.passphrase.

I've also added a TODO to re-evaluate later if we want the "password
masking" -- it is currently not functional, so one still can't observe the
length of the password typed at the prompt.

1 files changed, 21 insertions, 7 deletions

diff --git a/stand/lua/password.lua b/stand/lua/password.lua
index bac3a27a11e8..7257e1ee9ee3 100644
--- a/stand/lua/password.lua
+++ b/stand/lua/password.lua
@@ -40,7 +40,8 @@ function password.read()
 		if ch == core.KEY_ENTER then
 			break;
 		end
-
+		-- XXX TODO: Evaluate if we really want this or not, as a
+		-- security consideration of sorts
 		if (ch == core.KEY_BACKSPACE) or (ch == core.KEY_DELETE) then
 			if n > 0 then
 				n = n - 1;
@@ -58,23 +59,36 @@ end
 
 function password.check()
 	screen.defcursor();
-	local function compare(prompt, pwd)
-		if (pwd == nil) then
-			return;
-		end
+	-- pwd is optionally supplied if we want to check it
+	local function do_prompt(prompt, pwd)
 		while true do
 			loader.printc(prompt);
-			if (pwd == password.read()) then
-				break;
+			local read_pwd = password.read();
+			if (not pwd) or (pwd == read_pwd) then
+				return read_pwd;
 			end
 			print("\n\nloader: incorrect password!\n");
 			loader.delay(3*1000*1000);
 		end
+		-- Throw an extra newline out after the password prompt
+		print("")
+	end
+	local function compare(prompt, pwd)
+		if (pwd == nil) then
+			return;
+		end
+		do_prompt(prompt, pwd);
 	end
 
 	local boot_pwd = loader.getenv("bootlock_password");
 	compare("Boot password: ", boot_pwd);
 
+	local geli_pass_prompt = loader.getenv("geom_eli_passphrase_prompt");
+	if (geli_pass_prompt:lower() == "yes") then
+		local passphrase = do_prompt("GELI Passphrase: ");
+		loader.setenv("kern.geom.eli.passphrase", passphrase)
+	end
+
 	local pwd = loader.getenv("password");
 	if (pwd ~=nil) then
 		core.autoboot();