#! /usr/bin/env bash


[[ $(basename -- "$0") == "gs_funcs" ]] && { echo "Use gsocket, gs-netcat, gs-sftp, gs-mount or blitz instead."; exit 1; }

# Find a sftp-server binary
find_binary()
{
	bin=$1
	command -v "${bin}" && { echo "${bin}"; return; }
	shift 1
	for dir in "$@"; do
		file="${dir}/${bin}"
		if [[ -f "$file" ]]; then
			echo "${file}"
			return
		fi
	done
	echo ""
	return
}

read_password()
{
	echo -n >&2 "${GS_PRFX}Enter Secret (or press Enter to generate): "
	read -r password
	if [[ -z "${password}" ]]; then
		password=$(${GS_NETCAT_BIN} -g)
	fi
	echo "${password}" | tr -d "[:space:]"
}

# haystack1 haystack2 needle
ucheck_fail()
{
	[[ "$1" =~ $3 ]] || { echo >&2 "Symbol $3 not found in sftp-server."; exit 255; }
	[[ "$2" =~ $3 ]] || { echo >&2 "Symbol $3 not found (2)."; exit 255; }
}

test_sftp()
{
	echo "${1}" | ./gs-sftp -k id_sec.txt -wq 2>&1 | grep -c "Permission denied"
}

first_symbol()
{
	for func in "$@"; do
		if [[ "$sym_sftp" =~ $func ]]; then
			echo "$func "
			return
		fi
	done
	echo ">>>$*-NOT-FOUND<<< "
}

uchroot_check_sym()
{
	command -v nm >/dev/null 2>&1 || { echo >&2 "chroot failed (nm not found. apt-get install binutils?). Try -U to disable."; exit 255; }

	# Extract symbols from .so and sftp-server binary
	if [[ "$OSTYPE" == "darwin"* ]]; then
		# on OSX remove the starting "_" from symboles
		sym_sftp="$(nm -pu "${SFTP_SERVER_BIN}" | sed 's/^_//g')"
		sym_uchr="$(nm -p "${UCHROOT_BIN}" | grep " T " | sed 's/^_//g')"
	elif [[ "$OSTYPE" == "solaris"* ]]; then
		sym_sftp="$(nm -Du "${SFTP_SERVER_BIN}")"
		sym_uchr="$(nm -p "${UCHROOT_BIN}" | grep " T ")"
	else
		sym_sftp="$(nm -Du "${SFTP_SERVER_BIN}")"
		sym_uchr="$(nm -D "${UCHROOT_BIN}" | grep " T ")"
	fi

	[[ -n "$sym_uchr" ]] || { echo >&2 "chroot self-test failed (nm bad1). Try -U to disable."; exit 255; }
	[[ -n "$sym_sftp" ]] || { echo >&2 "chroot self-test failed (nm bad2). Try -U to disable."; exit 255; }
	funclist+=$(first_symbol lstat\$INODE64 __lxstat64 __lxstat lstat64 lstat)
	funclist+=$(first_symbol stat\$INODE64 __xstat64 __xstat stat64 stat)
	funclist+=$(first_symbol opendir\$INODE64 opendir64 opendir)
	funclist+=$(first_symbol open64 open)
	if [[ ! "$OSTYPE" == "solaris2.10"* ]]; then
		# On solaris 10 the stock OpenSSH install does not use statvfs64 (older version)
		funclist+=$(first_symbol statvfs64 statvfs)
	fi
	[[ "${funclist}" =~ "NOT-FOUND"* ]] && { echo >&2 "Missing symbol...${funclist}"; exit 255; }

	funclist+="chmod link mkdir rename rmdir symlink unlink"
	# echo "funclist = $funclist"	# DEBUG
	for func in ${funclist}; do
		ucheck_fail "${sym_sftp}" "${sym_uchr}" "${func}"
	done
}

failed()
{
	echo >&2 "ERROR: Self test failed: $1. Try -U to disable."

	exit 255
}
# Verify that all symboles will get hijacked. exit on failure.
# 			linux      osx		solaris
# sftp		-Du			-pu		-Du
# .so		-D|T		-p|T	-p|T
uchroot_check()
{
	local VALID_CMD
	local FAIL_CMD

	# skip nm-style symbol check on cygwin
	# (sftp-server does not like nm on cygwin?!)
	if [[ x"$OSTYPE" != "xcygwin"* ]]; then
		# NOT cygwin
		uchroot_check_sym
	fi

	# Run a self test (sftp -D sftp-server)
	command -v sftp >/dev/null 2>&1 || { failed "sftp not found"; }
	mkdir -p "${ROOTDIR}/ok"
	mkdir -p "${ROOTDIR}/denied"
	# echo "ROOTDIR=${ROOTDIR}"		# DEBUG
	echo hello exist-allowed.txt >"${ROOTDIR}/ok/exist-allowed.txt"
	echo hello exist-denied.txt >"${ROOTDIR}/denied/exist-denied.txt"
	dd if=/dev/urandom bs=1k count=1 2>/dev/null >"${ROOTDIR}/ok/test1k.dat"
	echo "\
#! /bin/bash
cd \"${ROOTDIR}\"/ok
${PRELOAD} ${SFTP_SERVER_BIN} ${SFTP_ARGS[*]}" >"${ROOTDIR}/sftp-server.sh"
	chmod 755 "${ROOTDIR}/sftp-server.sh"

	# Run GOOD commands that should work
	VALID_CMD="
mkdir dir1
cd dir1
cd ..
cd dir1
cd ../
ls ${ROOTDIR}/ok
ls ${ROOTDIR}/ok/exist-allowed.txt
put test1k.dat dir1
mkdir ./dir2/
"
	[[ $(cd "${ROOTDIR}/ok"; echo "$VALID_CMD" | sftp -D "${ROOTDIR}/sftp-server.sh" 2>&1 | grep -c "Permission denied") -eq 0 ]] || { failed "valid cmd 0"; }
	[[ -d "${ROOTDIR}/ok/dir1" ]] || { failed "valid-cmd 1"; }
	[[ -d "${ROOTDIR}/ok/dir2" ]] || { failed "valid-cmd 2"; }
	[[ -f "${ROOTDIR}/ok/dir1/test1k.dat" ]] || { failed "valid-cmd 3"; }


	FAIL_CMD="
rename exist-allowed.txt ../denied/0wned.txt
mkdir ./dir1/../../denied/0wned
cd dir1/../../denied
cd ./../denied
ls ${ROOTDIR}
cd ${ROOTDIR}
cd ${ROOTDIR}/denied
cd ${ROOTDIR}/ok/../denied
rm ./../denied/exist-denied.txt
put test1k.dat ../denied/0wned.dat
put test1k.dat ../denied/exist-denied.txt
rename exist-allowed.txt ../denied/0wned.txt
rename exist-allowed.txt /0wned.txt
"
	[[ $(cd "${ROOTDIR}/ok"; echo "$FAIL_CMD" | sftp -D "${ROOTDIR}/sftp-server.sh" 2>&1 | grep -c "Permission denied") -eq 13 ]] || { failed "fail cmd (2)"; }

	FAIL_CMD="
ls dir1/../../denied
ls ./../denied/exist-denied.txt"
	[[ $(cd "${ROOTDIR}/ok"; echo "$FAIL_CMD" | sftp -D "${ROOTDIR}/sftp-server.sh" 2>&1 | grep -c "not found") -eq 2 ]] || { failed "fail cmd (3)"; }
	rm -rf "${ROOTDIR}/ok" &>/dev/null
	rm -rf "${ROOTDIR}/denied" &>/dev/null
	rm -rf "${ROOTDIR}/sftp-server.sh" &>/dev/null
}


gs_find_so_single()
{
	[[ -e "${1}/${2}" ]] && { echo "$(cd "${1}" || exit; pwd)""/${2}"; }
}

arrayContains()
{
	local e match="$1"
	shift
	for e; do [[ "$e" == "$match" ]] && return 0; done
	return 1
}

# Search for the dynamic shared object file.
# 1. Try $basedir
# 2. Try ${basedir}/../lib
# 3. Try /usr/lib
# 4. Try /usr/local/lib
# Return absolute path to DSO. 
gs_find_so()
{
	local DL=("${BASEDIR}")
	# Debian packaging requires libs in /usr/lib/x86_64-linux-gnu  :/
	if command -v dpkg-architecture &>/dev/null; then
		DL+=("/usr/lib/$(dpkg-architecture -qDEB_HOST_MULTIARCH)")
	fi

	DL+=("${1}/lib") # This is either GS_PREFIX/lib or BASEDIR/../lib
	arrayContains "/usr/lib" "${DL[@]}" || DL+=("/usr/lib")
	arrayContains "/usr/local/lib" "${DL[@]}" || DL+=("/usr/local/lib")

	for dir in "${DL[@]}"; do
		res=$(gs_find_so_single "${dir}" "${2}")
		[[ -z "$res" ]] || { echo "$res"; return; }
	done
}

gs_init()
{
	GS_NETCAT_BIN="gs-netcat"
	BIN="${BASEDIR}/${GS_NETCAT_BIN}"
	[[ -f "${BIN}" ]] && GS_NETCAT_BIN="${BIN}"
	# shellcheck disable=SC2034 # appears unused. Verify use (or export if used externally).
	GS_SFTP_BIN="${BASEDIR}/gs-sftp"
	EXE=""
	if [[ "$OSTYPE" == "cygwin"* ]]; then
		EXE=".exe"
	fi

	# To find sftp-server and DSO's in PREFIX/lib
	PREFIX="$GS_PREFIX"
	[[ -z "$PREFIX" ]] && PREFIX="$(cd "$(dirname "${0}")/../" || exit; pwd)"

	# on OSX the dl-files are called .bundle (not .dylib) but it is generally
	# accepted to call them .so. OSX keep those is /System/Library/gsocket
	# but automake insists on ${PREFIX}/lib
	UCHROOT_BIN=$(gs_find_so "$PREFIX" "gsocket_uchroot_dso.so.0${EXE}")
	[[ -z "$UCHROOT_BIN" ]] && { echo >&2 "gsocket: gsocket_uchroot_dso.so.0${EXE} not found. Try 'apt install dpkg-dev'."; exit 5; }
	# shellcheck disable=SC2034 # appears unused. Verify use (or export if used externally).
	GS_SO_BIN=$(gs_find_so "$PREFIX" "gsocket_dso.so.0${EXE}")
	[[ -z "$GS_SO_BIN" ]] && { echo >&2 "gsocket: gsocket_dso.so.0${EXE} not found."; exit 5; }

	# shellcheck disable=SC2034 # appears unused. Verify use (or export if used externally).
	BIN_NAME="$(basename "${0}")"

	command -v "${GS_NETCAT_BIN}" >/dev/null 2>&1 || { echo >&2 "${GS_NETCAT_BIN} not found. Check PATH=?"; exit 1; }
}

usage()
{
	echo "
   -l           Server Mode.
   -R           Server in read-only mode.
   -s <secret>  Secret (e.g. password).
   -k <file>    Read Secret from file.
 
Example:
    $ ${1} -s MySecret -l             # Server
    $ ${1} -s MySecret                # Client

See 'gs-netcat -h' for more options."

}

do_getopt()
{
	OPTERR=0
	FL_NEED_PASSWORD=1
	IS_UCHROOT=1
	# Check if -s or -k is already supplied in environment and dont ask again.
	[[ "$GSOCKET_ARGS" =~ ^'-s' ]] && unset FL_NEED_PASSWORD
	[[ "$GSOCKET_ARGS" =~ ' -s' ]] && unset FL_NEED_PASSWORD
	[[ "$GSOCKET_ARGS" =~ ^'-k' ]] && unset FL_NEED_PASSWORD
	[[ "$GSOCKET_ARGS" =~ ' -k' ]] && unset FL_NEED_PASSWORD
	# shellcheck disable=SC2220 # Invalid flags are not handled. Add a *) case.
	while getopts ":qhURgls:k:L:" opt; do
		case ${opt} in
			s )
				GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]="-s"	# Add to end of array
				GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]="$OPTARG"	# Add to end of array
				unset FL_NEED_PASSWORD
				;;
			k )
				GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]="-k"	# Add to end of array
				KFILE=$(cd "$(dirname "$OPTARG")" && pwd)/$(basename "$OPTARG")
				[[ -f "${KFILE}" ]] || { echo >&2 "File not found: ${KFILE}"; exit 255; }
				GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]="${KFILE}"	# Add to end of array
				# KFILE=$(eval echo "$OPTARG")	# Add to end of array
				# GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]=$(eval echo "$OPTARG")	# Add to end of array
				unset FL_NEED_PASSWORD
				;;
			g )
				"${GS_NETCAT_BIN}" -g
				exit
				;;
			h )
				my_usage
				;;
			q )
				IS_QUIET=1
				ARGS_NEW[${#ARGS_NEW[@]}]="-q"
				;;
			l )
				# shellcheck disable=SC2034 # appears unused. Verify use (or export if used externally).
				IS_SERVER=1
				ARGS_NEW[${#ARGS_NEW[@]}]="-l"	# Add to end of array			
				;;
			R )
				# shellcheck disable=SC2034 # appears unused. Verify use (or export if used externally).
				IS_READONLY=1
				SFTP_ARGS[${#SFTP_ARGS[@]}]="-R"
				;;
			U )
				unset IS_UCHROOT
				;;
			\? )
				# UNKNOWN option. Handle before '*' (e.g. -l)
				ARGS_NEW[${#ARGS_NEW[@]}]="-${OPTARG}"	# Add to end of array			
				;;
			* )
				# Other (known opts from opstring) w parameters (e.g. -L <file>)
				ARGS_NEW[${#ARGS_NEW[@]}]="-${opt}"		# Add to end of array			
				ARGS_NEW[${#ARGS_NEW[@]}]="${OPTARG}"	# Add to end of array			
				;;
		esac
	done
	# Solaris 10 problems:
	# - stock sftp-server does not allow -p <whitelist> -> Acceptable risk
	# - LD_PRELOAD does not seem to work. Does anyone still use solaris10?
	if [[ "$OSTYPE" == "solaris2.10"* ]]; then
		echo -e >&2 "\033[1;31mWARNING\033[0m: uchroot not (yet) supported on solaris 10."
		unset IS_UCHROOT
	fi
}

env_arg_init()
{
	# Prepare existing GSOCKET_ARGS to take more arguments if there are any
	[[ -n "$GSOCKET_ARGS" ]] && GSOCKET_ARGS+=" "
	if [[ -n "$FL_NEED_PASSWORD" ]]; then
		password=$(read_password)
		# shellcheck disable=SC2034 # GSOCKET_SECRET appears unused => It's used in 'gs'
		GSOCKET_SECRET="${password}"
		echo "${GS_PRFX}=Secret         : ${password}"
		GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]="-s"		# Add to end of array			
		GSNC_ENV_ARGS[${#GSNC_ENV_ARGS[@]}]="$password"	# Add to end of array			
	fi
	# Have to output it here because gs-netcat might be started from withing
	# sshfs or sftpd where stderr is no longer available to gs-netcat
	[[ -n "$IS_QUIET" ]] || echo >&2 "${GS_PRFX}=Encryption     : SRP-AES-256-CBC-SHA-End2End (Prime: 4096 bits)"
	ENV_ARGS="${GSOCKET_ARGS}${GSNC_ENV_ARGS[*]}"
}

sftp_server_start()
{
	# SERVER
	if [[ "$OSTYPE" == "darwin"* ]]; then
		# OSX does not allow LD_PRELOAD of binaries in /usr/. Copy to tmp...
		ROOTDIR=$(mktemp -d -t thc-gs-sftp)
		# FIXME: temp file only cleaned on reboot. Hmm...
		cp /usr/libexec/sftp-server "${ROOTDIR}/sftp-server" &>/dev/null
		SFTP_SERVER_BIN="${ROOTDIR}/sftp-server"
		PRELOAD="DYLD_INSERT_LIBRARIES=${UCHROOT_BIN} DYLD_FORCE_FLAT_NAMESPACE=1"
	else
		if [[ -n "${IS_UCHROOT}" ]]; then
			ROOTDIR=$(mktemp -d -t thc-gs-sftp-XXXXXXXXXXXXXXX) 
		fi
		SFTP_SERVER_BIN=$(find_binary "sftp-server${EXE}" "${PREFIX}/lib" /opt/csw/libexec /usr/lib /usr/local/lib /usr/libexec /usr/libexec/openssh /usr/lib/ssh /usr/sbin)
		PRELOAD="LD_PRELOAD=${UCHROOT_BIN}"
	fi
	[[ -z "${SFTP_SERVER_BIN}" ]] && { echo >&2 "sftp-server binary not found."; exit 1; }

	# SFTP_ARGS[${#SFTP_ARGS[@]}]="-l"
	# SFTP_ARGS[${#SFTP_ARGS[@]}]="DEBUG3"	# tail /var/log/auth.log | grep 'Refusing non-whitelisted'

	# Whitelist of commands sftp-server should allow (most are not needed
	# by sftp but for sshfs)
	# *** WARNING ***: If you add a string here you also must make sure that
	# gsocket_uchroot_dso checks the command for uchroot-escape.
	SFTP_ARGS[${#SFTP_ARGS[@]}]="-p"
	SFTP_ARGS[${#SFTP_ARGS[@]}]="open,opendir,mkdir,remove,rmdir,symlink,hardlink,stat,posix-rename,statvfs,setstat,fsetstat,fstat,lstat,readdir,realpath,write,read,close"

	ENV_ARGS="${GSOCKET_ARGS}${GSNC_ENV_ARGS[*]}"

	if [[ -n "${IS_UCHROOT}" ]]; then
		[[ -z "${ROOTDIR}" ]] && { failed "(mktemp)"; }
		uchroot_check
		# Try to delete temporary directory. OSX still has sftp-server bin in there and must be deleted
		rmdir "${ROOTDIR}" &>/dev/null
	else
		echo -e >&2 "\033[1;31mWARNING\033[0m: uchroot disabled. Allowing access to *ALL* files on this host."
		unset PRELOAD
	fi
	GSOCKET_NO_GREETINGS="1" GSOCKET_ARGS="${ENV_ARGS}" exec "${GS_NETCAT_BIN}" "${ARGS_NEW[@]}" -e "${PRELOAD} ${SFTP_SERVER_BIN} ${SFTP_ARGS[*]} 2>/dev/null"
}