#!/bin/bash

# Compile server manager for systemtap
#
# Copyright (C) 2008-2010 Red Hat Inc.
#
# This file is part of systemtap, and is free software.  You can
# redistribute it and/or modify it under the terms of the GNU General
# Public License (GPL); either version 2, or (at your option) any
# later version.

# This script publishes its presence on the network and then listens for
# incoming connections. When a connection is detected, the stap-server script
# is run to handle the request.

# Catch ctrl-c and other termination signals
trap 'terminate' SIGTERM SIGINT

# Initialize the environment
. ${PKGLIBEXECDIR}stap-env

# PR11197: security prophylactics
set_ulimits=0
if [ -z "$STAP_PR11197_OVERRIDE" ]; then
    # 1) reject use as root, except via a special environment variable
    if [ `id -u` -eq 0 ]; then
        echo "For security reasons, invocation of stap-server as root is not supported." 1>&2
        exit 1
    fi 
    # 2) resource limits should be set if the user is the 'stap-server' daemon
    test `id -un` = "stap-server" && set_ulimits=1
fi


#-----------------------------------------------------------------------------
# Helper functions.
#-----------------------------------------------------------------------------
# function: initialization PORT
function initialization {
    # Initial values
    port=
    ssl_db=
    stap_options=
    uname_r="`uname -r`"
    arch="`stap_get_arch`"
    logfile=/dev/null
    B_options=
    I_options=
    R_option=

    # Parse the arguments
    parse_options "$@"

    echo ===== compile server pid $$ started >> $logfile

    # What port will we listen on?
    test "X$port" = "X" && port=$((1024+$RANDOM%64000))
    while netstat -atn | awk '{print $4}' | cut -f2 -d: | egrep -q "^$port\$";
    do
        # Whoops, the port is busy; try another one.
	echo "$0: Port $port is busy" >> $logfile
        port=$((1024+($port + $RANDOM)%64000))
    done

    # Where is the ssl certificate/key database?
    if test "X$ssl_db" = "X"; then
	ssl_db=$stap_ssl_db/server
    fi

    nss_pw=$ssl_db/pw
    nss_cert=stap-server
}

# function: parse_options [ STAP-OPTIONS ]
#
# Examine the command line. We need not do much checking, but we do need to
# parse all options in order to discover the ones we're interested in.
function parse_options {
    while test $# != 0
    do
	advance_p=0
	dash_seen=0

        # Start of a new token.
	first_token=$1

	# Process the option.
	until test $advance_p != 0
	do
            # Identify the next option
	    first_char=`expr "$first_token" : '\(.\).*'`
	    if test $dash_seen = 0; then
		if test "$first_char" = "-"; then
		    if test "$first_token" != "-"; then
	                # It's not a lone dash, so it's an option.
			# Is it a long option (i.e. --option)?
			second_char=`expr "$first_token" : '.\(.\).*'`
			if test "X$second_char" = "X-"; then
			    case `expr "$first_token" : '--\([^=]*\)'` in
				port)
				    get_long_arg $first_token $2
				    port=$stap_arg
				    ;;
				ssl)
				    get_long_arg $first_token $2
				    ssl_db=$stap_arg
				    ;;
				log)
				    get_long_arg $first_token $2
				    logfile=$stap_arg
				    ;;
				*)
				    warning "Option '$first_token' ignored"
				    advance_p=$(($advance_p + 1))
				    break
				    ;;
			    esac
			fi
	                # It's not a lone dash, or a long option, so it's a short option string.
			# Remove the dash.
			first_token=`expr "$first_token" : '-\(.*\)'`
			dash_seen=1
			first_char=`expr "$first_token" : '\(.\).*'`
		    fi
		fi
		if test $dash_seen = 0; then
	            # The dash has not been seen. This is not an option at all.
		    warning "Option '$first_token' ignored"
		    advance_p=$(($advance_p + 1))
		    break
		fi
	    fi
	    
            # We are at the start of an option. Look at the first character.
	    case $first_char in
		a)
		    get_arg $first_token $2
		    process_a $stap_arg
		    ;;
		B)
		    get_arg $first_token $2
		    B_options="$B_options $stap_arg"
		    stap_options="$stap_options -$first_char $stap_arg"
		    ;;
		c)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		d)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		D)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		e)
		    get_arg $first_token "$2"
		    warning "Option '-$first_char '$stap_arg' ignored'"
		    ;;
		I)
		    get_arg $first_token $2
		    I_options="$I_options $stap_arg"
		    stap_options="$stap_options -$first_char $stap_arg"
		    ;;	
		l)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		L)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		m)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		o)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		p)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		r)
		    get_arg $first_token $2
		    process_r $stap_arg
		    ;;	
		R)
		    get_arg $first_token $2
		    R_option="$stap_arg"
		    stap_options="$stap_options -$first_char $stap_arg"
		    ;;	
		s)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;	
		S)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;	
		x)
		    get_arg $first_token $2
		    warning "Option '-$first_char $stap_arg' ignored"
		    ;;
		*)
		    # An unknown flag. Ignore it.
		    ;;
	    esac

	    if test $advance_p = 0; then
	        # Just another flag character. Consume it.
		warning "Option '-$first_char' ignored"
		first_token=`expr "$first_token" : '.\(.*\)'`
		if test "X$first_token" = "X"; then
		    advance_p=$(($advance_p + 1))
		fi
	    fi
	done

        # Consume the arguments we just processed.
	while test $advance_p != 0
	do
	    shift
	    advance_p=$(($advance_p - 1))
	done
    done
}

# function: get_arg FIRSTWORD SECONDWORD
#
# Collect an argument to the given short option
function get_arg {
    # Remove first character. Advance to the next token, if the first one
    # is exhausted.
    local first=`expr "$1" : '.\(.*\)'`
    if test "X$first" = "X"; then
	shift
	advance_p=$(($advance_p + 1))
	first=$1
    fi
    stap_arg="$first"
    advance_p=$(($advance_p + 1))
}

# function: get_arg FIRSTWORD SECONDWORD
#
# Collect an argument to the given long option
function get_long_arg {
    # Remove first character. Advance to the next token, if the first one
    # is exhausted.
    local first=`expr "$1" : '.*\=\(.*\)'`
    if test "X$first" = "X"; then
	shift
	advance_p=$(($advance_p + 1))
	first=$1
    fi
    stap_arg="$first"
    advance_p=$(($advance_p + 1))
}

# function: process_a ARGUMENT
#
# Process the -a flag.
function process_a {
    if test "X$1" != "X$arch"; then
	arch=$1
	stap_options="$stap_options -a $1"
    fi
}

# function: process_r ARGUMENT
#
# Process the -r flag.
function process_r {
    local first_char=`expr "$1" : '\(.\).*'`

    if test "$first_char" = "/"; then # fully specified path
        kernel_build_tree=$1
        version_file_name="$kernel_build_tree/include/config/kernel.release"
        # The file include/config/kernel.release within the kernel
        # build tree is used to pull out the version information
	release=`cat $version_file_name 2>/dev/null`
	if test "X$release" = "X"; then
	    fatal "Missing $version_file_name"
	    return
	fi
    else
	# kernel release specified directly
	release=$1
    fi

    if test "X$release" != "X$uname_r"; then
	uname_r=$release
	stap_options="$stap_options -r $release"
    fi
}

# function: check_cert
#
# Ensure that our certificate exists and is valid.
# Generate a new one if not.
function check_cert {
    # If our certificate exists, log some information about it.
    if test -f $ssl_db/cert8.db; then
	echo "Certificate found in database $ssl_db" >> $logfile
	certutil -L -d "$ssl_db" -n $nss_cert | \
	    awk '/Validity|Not After|Not Before/ { print $0 }' | \
	    sed 's/^ */  /' >> $logfile
    fi

    # If the certificate does not exist or the certificate
    # is not valid, then generate a new one.
    if test ! -d $ssl_db -o ! -f $ssl_db/$stap_certfile -o ! -f $ssl_db/cert8.db || \
       ! certutil -V -n $nss_cert -u V -d $ssl_db -e -f $nss_pw \
                     -b `date +%g%m%d%H%M%S`+0005 >> $logfile 2>&1; then
	# Our certificate does not exist or is not valid.
	# Generate a new certificate database.
	${stap_pkglibexecdir}stap-gen-cert $ssl_db >> $logfile 2>&1 || exit 1

        # Now add the new certificate to the client's database,
        # making it a trusted peer for this user.
	# Do this only if the client has been installed.
	if test -f `which ${stap_exec_prefix}stap-client 2>/dev/null` -a \
	        -x `which ${stap_exec_prefix}stap-client 2>/dev/null`; then
	    ${stap_exec_prefix}stap-authorize-server-cert $ssl_db/$stap_certfile >> $logfile 2>&1
	fi
    elif ! test -f $stap_ssl_db/client/cert8.db; then
	# Our certificate exists and is valid.
	# If the client's database does not exist, then initialize it with our certificate.
	# Do this only if the client has been installed.
	if test -f `which ${stap_exec_prefix}stap-client 2>/dev/null` -a \
	    -x `which ${stap_exec_prefix}stap-client 2>/dev/null`; then
	    ${stap_exec_prefix}stap-authorize-server-cert $ssl_db/$stap_certfile >> $logfile 2>&1
	fi
    fi
}

# function: advertise_presence
#
# Advertise the availability of the server on the network.
function advertise_presence {
    # Build up a strings representing our server's properties.
    # The service name must differ for each server, so put the port number
    # in it.
    service_name="Systemtap Compile Server on port $port"

    local sysinfo="sysinfo=$uname_r $arch"
    local optinfo="optinfo="
    test -n "$R_option" && optinfo="${optinfo}-R '$R_option'"
    for opt in $B_options; do
	optinfo="$optinfo -B '$opt'"
    done
    for opt in $I_options; do
	optinfo="$optinfo -I '$opt'"
    done
    optinfo=`echo $optinfo | sed 's/optinfo= /optinfo=/'`

    # Call avahi-publish-service to advertise our presence.
    avahi-publish-service "$service_name" \
	$stap_avahi_service_tag $port "$sysinfo" "$optinfo" >> $logfile 2>&1 &
}

# function: listen
#
# Listen for and handle requests to the server.
function listen {
    # The stap-server-connect program will listen forever
    # accepting requests.
    # CVE-2009-4273 ... or at least, until resource limits fire
    while true; do # NB: loop to avoid DoS by deliberate rlimit-induced halt
	# Ensure that our certificate is valid. Generate a new one if
	# not.
	check_cert

        # NB: impose resource limits in case of mischevious data inducing
        # too much / long computation
        (test $set_ulimits = 1 && ulimit -f 50000 -s 1000 -t 60 -u 20 -v 500000;
         exec ${stap_pkglibexecdir}stap-server-connect \
	   -p $port -n $nss_cert -d $ssl_db -w $nss_pw \
	   -s "$stap_options") &
        stap_server_connect_pid=$!
	echo "$service_name ready"
        wait $stap_server_connect_pid

        # NB: avoid superfast spinning in case of a ulimit or other failure
        sleep 1
    done >> $logfile 2>&1
}

# function: warning [ MESSAGE ]
#
# Warning error
# Prints its arguments to stderr
function warning {
    echo "$0: WARNING:" "$@" >> $logfile
}

# function: fatal [ MESSAGE ]
#
# Fatal error
# Prints its arguments to stderr and exits
function fatal {
    echo "$0: ERROR:" "$@" >> $logfile
    terminate
    exit 1
}

# function: terminate
#
# Terminate gracefully.
function terminate {
    echo "$0: Exiting" >> $logfile

    # Kill the running 'avahi-publish-service' job
    kill -s SIGTERM '%avahi-publish-service' >> $logfile 2>&1
    wait '%avahi-publish-service' >> $logfile 2>&1

    # Kill any running 'stap-server-connect' job.
    kill -s SIGTERM $stap_server_connect_pid >> $logfile 2>&1
    wait $stap_server_connect_pid >> $logfile 2>&1

    exit
}

#-----------------------------------------------------------------------------
# Beginning of main line execution.
#-----------------------------------------------------------------------------
initialization "$@"
advertise_presence
listen