XSu

#!/bin/bash
#Written by Manuel Iglesias. glesialo@gmail.com

CommandName=${0##*/}
TempDir=/tmp
HomeBasePath="/home"
TempXSessionErrorsFileName=".xsession-errors"
TempXAuthorityFileName=".Xauthority"
UserNamePlaceHolder="USERNAME"
DefaultAskForPasswordMessage="Please type $UserNamePlaceHolder password."
UserOption="--user"
UserOptionMissingMessage="Missing user's name"
MessageOption="--message"
MessageOptionMissingMessage="Missing message string"
DefaultMissingMessage="Missing string"
English_LANG=en_IE.UTF-8
English_LANGUAGE=en_IE:en
SuAuthenticationFailureMessage="su: Authentication failure"
Dialog_MessageTimedTimeout=5 # In seconds.
WrongPasswordMessage="ERROR: Incorrect password."



#Functions. BEGIN.
echoE()
{
echo -e "$@" 1>&2 # If run in a X window application: writes to XsessionErrorsFile
Dialog_MessageTimed --title "$CommandName-$$" --timeout $Dialog_MessageTimedTimeout "$(echo -e "$@")" &>/dev/null &
return 0
}

Exit() # $1: Script ExitCode
{
if [ -n "$Old_DBUS_SESSION_BUS_ADDRESS" ]
  then
    export DBUS_SESSION_BUS_ADDRESS=$Old_DBUS_SESSION_BUS_ADDRESS
fi
if [ -n "$Old_XAUTHORITY" ]
  then
    export XAUTHORITY=$Old_XAUTHORITY
fi
if [ -n "$Old_USER" ]
  then
    export USER=$Old_USER
fi
if [ -n "$Old_HOME" ]
  then
    export HOME=$Old_HOME
fi
if [ -n "$Old_LANG" ]
  then
    export LANG=$Old_LANG
fi
if [ -n "$Old_LANGUAGE" ]
  then
    export LANGUAGE=$Old_LANGUAGE
fi
if [ -f "$TempXAuthorityFile" ]
  then
    if ! rm $TempXAuthorityFile &>/dev/null
      then
        echoE "$CommandName-$$: Warning! Can't remove temporary \$XAUTHORITY file."
    fi
fi
if [ -f "$TempXSessionErrorsFile" ]
  then
    if [ -s "$TempXSessionErrorsFile" ] # If more than 0 bytes
      then
        while read Line
          do
            echo "$CommandName-$$: $Line"
          done < "$TempXSessionErrorsFile"
    fi
    if ! rm $TempXSessionErrorsFile &>/dev/null
      then
        echoE "$CommandName-$$: Warning! Can't remove '$TempXSessionErrorsFile' file."
    fi
fi
echo "$CommandName-$$: Exit code: $1."
echo "#### $CommandName-$$. END." # Mark end of output
exit $1 # This is not a mistake. Here the whole script exits.
}

Usage()
{
echoE "'$CommandName' lets user run a (graphical) Command as a different user (UserName) if the correct
password is given. If no UserName is supplied, '$CommandName' will run the given Command as 'root'.
Command will run with the same environment UserName would have after login.
Usage: '$CommandName [Options] Command [CommandParameters]'.
Options:
  [$UserOption UserName] (Command will run for UserName).
  [$MessageOption request_password_message] (will replace the default message).
Note: StdOut & StdError will be redirected to (invoking user's) '\$HOME/$TempXSessionErrorsFileName'."
return 0
}
#Functions. END.



if [ $# -lt 1 ] || [ "$1" == "-h" ] || [ "$1" == "-?" ] || [ "$1" == "--help" ] || [ "$1" == "-help" ]
  then
    Usage
    exit 64
fi

#Mark beginning of output. BEGIN.
CommandLine="$CommandName"
for Param in "$@"
  do
    Substrings=0
    for SubString in $Param
      do
        let Substrings++
      done
    if [ $Substrings -gt 1 ]
      then
        CommandLine=$CommandLine" \"$Param\""
      else
        CommandLine=$CommandLine" $Param"
    fi
  done
echo -e "#### $CommandName-$$. BEGIN.\n$CommandName-$$.CmmdLine:>$CommandLine<"
CommandLine=""
#Mark beginning of output. END.

#!! Use 'Exit' instead of 'exit' from now on to remove temporary files and mark end of output

#Temporary XSessionErrorsFile file. BEGIN.
if ! TempXSessionErrorsFile=$(mktemp ${TempDir}/${CommandName}${TempXSessionErrorsFileName}.XXXXXXXX 2>/dev/null) # Copy different for each instance of script.
 then
   echoE "$CommandName-$$: Failed to create temporary '$TempXSessionErrorsFileName' file. Aborting."
   Exit 73
fi
if ! chmod 666 $TempXSessionErrorsFile 2>/dev/null
  then
    echoE "$CommandName-$$: Can't change permissions of '$TempXSessionErrorsFile'. Aborting."
    Exit 77
fi
#Temporary XSessionErrorsFile file. END.

#Temporary $XAUTHORITY file. BEGIN.
if [ -z "$XAUTHORITY" ] || ! [ -f "$XAUTHORITY" ]
  then
    echoE "$CommandName-$$: \$XAUTHORITY file does not exist. Aborting."
    Exit 70
fi
if ! TempXAuthorityFile=$(mktemp ${TempDir}/${CommandName}${TempXAuthorityFileName}.XXXXXXXX 2>/dev/null)
 then
   echoE "$CommandName-$$: Failed to create temporary '$TempXAuthorityFileName' file. Aborting."
   Exit 73
fi
if ! cp -f $XAUTHORITY $TempXAuthorityFile 2>/dev/null #Current file in $XAUTHORITY has 600 permissions and, therefore, is only readable by its owner
 then
   echoE "$CommandName-$$: Can't copy \$XAUTHORITY file. Aborting."
   Exit 73
fi
if ! chmod 644 $TempXAuthorityFile 2>/dev/null # Read permissions to all
 then
   echoE "$CommandName-$$: Can't change permissions of temporary \$XAUTHORITY file. Aborting."
   Exit 77
fi
#Temporary $XAUTHORITY file. END.

RunWithLoginEnvironmentScript=$(which -a RunWithLoginEnvironment 2>/dev/null) # which: Path/File needed
if [ ! -f "$RunWithLoginEnvironmentScript" ]
  then
    echoE "$CommandName-$$: RunWithLoginEnvironmentScript 'RunWithLoginEnvironment' script not found. Aborting."
    Exit 127
fi

#Read strings and remove UserOption & MessageOption. BEGIN.
OptionMessageValue="";OptionUserValue="";Parameters="";VariableToRead="";WaitingForString=false
for Parameter in "$@"
  do
    if $WaitingForString
      then
        eval "$VariableToRead=\"$Parameter\""
        VariableToRead=""
        WaitingForString=false
      else
        if [ "$Parameter" == "$UserOption" ]
          then
            WaitingForString=true
            VariableToRead="OptionUserValue"
          else
            if [ "$Parameter" == "$MessageOption" ]
              then
                WaitingForString=true
                VariableToRead="OptionMessageValue"
              else
                Parameters=${Parameters}"\"$Parameter\" "
            fi
        fi
    fi
  done
if $WaitingForString && [ -n "$VariableToRead" ]
  then
    case "$VariableToRead" in
      OptionUserValue) echoE "$CommandName-$$: $UserOptionMissingMessage";;
      OptionMessageValue) echoE "$CommandName-$$: $MessageOptionMissingMessage";;
      *) echoE "$CommandName-$$: $DefaultMissingMessage";;
    esac
    Exit 64
fi
eval "set -- $Parameters" # To interpret correctly parameter values with spaces
#Read strings and remove UserOption & MessageOption. END.

Old_USER=$USER
Old_HOME=$HOME
if [ -z "$OptionUserValue" ]
  then
    OptionUserValue=root
fi
if IsRegisteredUser "$OptionUserValue"
  then
    export USER=$OptionUserValue
  else
    echoE "$CommandName-$$: '$OptionUserValue' is not a registered user. Aborting."
    Exit 67
fi
if [ "$USER" == "$Old_USER" ]
  then
    echoE "$CommandName-$$: '$OptionUserValue' is already the current user. Aborting."
    Exit 67
fi
if [ "$USER" == "root" ]
  then
    export HOME="/${USER}"
  else
    export HOME=${HomeBasePath}/${USER}
fi

if [ ! -d "$HOME" ]
  then
    echoE "$CommandName-$$: ${USER}'s \$HOME not found. Aborting."
    Exit 70
fi

if [ $# -eq 0 ]
  then
    echoE "$CommandName-$$: No Command to run. Aborting."
    Exit 127
fi

if [ -n "$OptionMessageValue" ]
  then
    AskForPasswordMessage="$OptionMessageValue"
  else
    AskForPasswordMessage=${DefaultAskForPasswordMessage/$UserNamePlaceHolder/${USER}\'s}
fi

if ! Password=$(Dialog_InputText --title "$CommandName-$$" --hide-entry-text "$AskForPasswordMessage" 2>/dev/null)
  then
    echoE "$CommandName-$$: Failed to read password. Aborting."
    Exit 90
fi

Old_XAUTHORITY=$XAUTHORITY
export XAUTHORITY=$TempXAuthorityFile
Old_LANG=$LANG
Old_LANGUAGE=$LANGUAGE
if [ -z "$Old_LANGUAGE" ]
  then
    Old_LANGUAGE=$Old_LANG
fi
Old_DBUS_SESSION_BUS_ADDRESS=$DBUS_SESSION_BUS_ADDRESS
export -n DBUS_SESSION_BUS_ADDRESS="" # Unset + export: Remove from environment. Some applications (I.E.: DefaultTerminalEmulator) refuse to start otherwise.
LANG=$English_LANG      # expect expects English su's messages
LANGUAGE=$English_LANGUAGE  # expect expects English su's messages
ExpectOut=$(expect - "$@" <<HereDoc
set force_conservative 1  ;# set to 1 to force conservative mode even if
              ;# script wasn't run conservatively originally
if {\$force_conservative} {
  set send_slow {1 .1}
  proc send {ignore arg} {
    sleep .1
    exp_send -s -- \$arg
  }
}
set timeout -1
set argsstring ""
foreach a \$argv {
  append argsstring "\"\${a}\" " ;# argsstring: "arg 1" "arg 2" ...
}
spawn \$env(SHELL)
match_max 100000
spawn -noecho su $USER -c "&>$TempXSessionErrorsFile LANG=$Old_LANG LANGUAGE=$Old_LANGUAGE $RunWithLoginEnvironmentScript \$argsstring"
expect "assword:"
send {ignore arg} "$Password\r"
expect eof
catch wait result
exit [lindex \$result 3]
HereDoc
)
ExitCode=$?
if [ "$ExpectOut" != "${ExpectOut/${SuAuthenticationFailureMessage}/}" ] # $SuAuthenticationFailureMessage found in expect output
  then
    echoE "$CommandName-$$: $WrongPasswordMessage"
    Exit 77
  else
    Exit $ExitCode # Necessary to remove temporary files.
fi