enable-tor: No longer needs to be run as root.

When run by not root, su's to root automatically.

This commit was sponsored by Brock Spratlen on Patreon.

CHANGELOG

@@ -21,6 +21,7 @@ git-annex (6.20161211) UNRELEASED; urgency=medium
     present in the local repo even when it was not.
   * enable-tor: Put tor sockets in /var/lib/tor-annex/, rather
     than in /etc/tor/hidden_service/.
+  * enable-tor: No longer needs to be run as root.
   * Fix build with directory-1.3.
   * Debian: Suggest tor and magic-wormhole.
   * Debian: Build webapp on armel.

Command/EnableTor.hs

@@ -5,12 +5,20 @@
  - Licensed under the GNU GPL version 3 or higher.
  -}
 
+{-# LANGUAGE CPP #-}
+
 module Command.EnableTor where
 
 import Command
 import P2P.Address
 import Utility.Tor
 import Annex.UUID
+import Config.Files
+
+#ifndef mingw32_HOST_OS
+import Utility.Su
+import System.Posix.User
+#endif
 
 -- This runs as root, so avoid making any commits or initializing
 -- git-annex, or doing other things that create root-owned files.
@@ -23,9 +31,27 @@ seek :: CmdParams -> CommandSeek
 seek = withWords start
 
 start :: [String] -> CommandStart
-start ps = case readish =<< headMaybe ps of
-	Nothing -> giveup "Bad params"
-	Just userid -> do
+start os = do
+#ifndef mingw32_HOST_OS
+	curruserid <- liftIO getEffectiveUserID
+	if curruserid == 0
+		then case readish =<< headMaybe os of
+			Nothing -> giveup "Need user-id parameter."
+			Just userid -> go userid
+		else do
+			liftIO $ putStrLn "Need root access to enable tor..."
+			gitannex <- liftIO readProgramFile
+			let ps = [Param (cmdname cmd), Param (show curruserid)]
+			ifM (liftIO $ runAsRoot gitannex ps)
+				( stop
+				, giveup $ unwords $
+					[ "Failed to run as root:" , gitannex ] ++ toCommand ps
+				)
+#else
+	go 0
+#endif
+  where
+	go userid = do
 		uuid <- getUUID
 		when (uuid == NoUUID) $
 			giveup "This can only be run in a git-annex repository."

Utility/Su.hs

@@ -0,0 +1,54 @@
+{- su to root
+ -
+ - Copyright 2016 Joey Hess <id@joeyh.name>
+ -
+ - License: BSD-2-clause
+ -}
+
+module Utility.Su where
+
+import Common
+import Utility.Env
+import Utility.Path
+
+import System.Posix.Terminal
+
+-- Runs a command as root, fairly portably.
+--
+-- Does not use sudo commands if something else is available, because
+-- the user may not be in sudoers and we couldn't differentiate between
+-- that and the command failing. Although, some commands like gksu
+-- decide based on the system's configuration whether sudo should be used.
+runAsRoot :: String -> [CommandParam] -> IO Bool
+runAsRoot cmd ps = go =<< firstM (inPath . fst) =<< selectcmds
+  where
+	go Nothing = return False
+	go (Just (cmd', ps')) = boolSystem cmd' ps'
+
+	selectcmds = ifM (inx <||> (not <$> atconsole))
+		( return (graphicalcmds ++ consolecmds)
+		, return consolecmds
+		)
+	
+	inx = isJust <$> getEnv "DISPLAY"
+	atconsole = queryTerminal stdInput
+
+	-- These will only work when the user is logged into a desktop.
+	graphicalcmds =
+		[ ("gksu", [Param shellcmd])
+		, ("kdesu", [Param shellcmd])
+		-- Available in Debian's menu package; knows about lots of
+		-- ways to gain root.
+		, ("su-to-root", [Param "-X", Param "-c", Param shellcmd])
+		-- OSX native way to run a command as root, prompts in GUI
+		, ("osascript", [Param "-e", Param ("do shell script \"" ++ shellcmd ++ "\" with administrator privileges")])
+		]
+	
+	-- These will only work when run in a console.
+	consolecmds = 
+		[ ("su", [Param "-c", Param "--", Param cmd] ++ ps)
+		, ("sudo", [Param cmd] ++ ps)
+		, ("su-to-root", [Param "-c", Param shellcmd])
+		]
+	
+	shellcmd = unwords $ map shellEscape (cmd:toCommand ps)

doc/git-annex-enable-tor.mdwn

@@ -4,14 +4,18 @@ git-annex enable-tor - enable tor hidden service
 
 # SYNOPSIS
 
+git annex enable-tor
+
 sudo git annex enable-tor $(id -u)
 
 # DESCRIPTION
 
 This command enables a tor hidden service for git-annex.
 
-It has to be run by root, since it modifies `/etc/tor/torrc`.
-Pass it your user id number, as output by `id -u`
+It modifies `/etc/tor/torrc` to register the hidden service. If run as a
+normal user, it will try to use sudo/su/etc to get root access to modify
+that file. If you run it as root, pass it your non-root user id number,
+as output by `id -u`
 
 After this command is run, `git annex remotedaemon` can be run to serve the
 tor hidden service, and then `git-annex p2p --gen-address` can be run to

doc/tips/peer_to_peer_network_with_tor.mdwn

@@ -23,7 +23,7 @@ to accomplish this.
 
 In each git-annex repository, run these commands:
 
-	sudo git annex enable-tor $(id -u)
+	git annex enable-tor
 	git annex remotedaemon
 
 Now git-annex is running as a Tor hidden service, but 

git-annex.cabal

@@ -1072,6 +1072,7 @@ Executable git-annex
     Utility.Shell
     Utility.SimpleProtocol
     Utility.SshConfig
+    Utility.Su
     Utility.SystemDirectory
     Utility.TList
     Utility.Tense