#!/bin/sh
#
# Core shell functions that do not require bash.  These functions are used with
# busybox ash on legacy-flash boards, and with bash on all other boards.

die() {
	if [ "$CONFIG_DEBUG_OUTPUT" = "y" ];then
		echo -e " !!! ERROR: $* !!!" | tee -a /tmp/debug.log /dev/kmsg > /dev/null;
	else
		echo -e >&2 "!!! ERROR: $* !!!";
	fi
	sleep 2;
	exit 1;
}

warn() {
	if [ "$CONFIG_DEBUG_OUTPUT" = "y" ];then
		echo -e " *** WARNING: $* ***" | tee -a /tmp/debug.log /dev/kmsg > /dev/null;
	else
		echo -e >&2 " *** WARNING: $* ***";
	fi
	sleep 1;
}

DEBUG() {
	if [ "$CONFIG_DEBUG_OUTPUT" = "y" ]; then
		# fold -s -w 960 will wrap lines at 960 characters on the last space before the limit
		echo "DEBUG: $*" | fold -s -w 960 | while read line; do
			echo "$line" | tee -a /tmp/debug.log /dev/kmsg >/dev/null
		done
	fi
}

TRACE() {
	if [ "$CONFIG_ENABLE_FUNCTION_TRACING_OUTPUT" = "y" ];then
		echo "TRACE: $*" | tee -a /tmp/debug.log /dev/kmsg > /dev/null;
	fi
}

# Write directly to the debug log (but not kmsg), never appears on console
LOG() {
	echo "LOG: $*" >>/tmp/debug.log
}

fw_version() {
	local FW_VER=$(dmesg | grep 'DMI' | grep -o 'BIOS.*' | cut -f2- -d ' ')
	# chop off date, since will always be epoch w/timeless builds
	echo "${FW_VER::-10}"
}

preserve_rom() {
	TRACE "Under /etc/ash_functions:preserve_rom"
	new_rom="$1"
	old_files=`cbfs -t 50 -l 2>/dev/null | grep "^heads/"`

	for old_file in `echo $old_files`; do
		new_file=`cbfs.sh -o $1 -l | grep -x $old_file`
		if [ -z "$new_file" ]; then
			echo "+++ Adding $old_file to $1"
			cbfs -t 50 -r $old_file >/tmp/rom.$$ \
			|| die "Failed to read cbfs file from ROM"
			cbfs.sh -o $1 -a $old_file -f /tmp/rom.$$ \
			|| die "Failed to write cbfs file to new ROM file"
		fi
	done
}

confirm_gpg_card() {
	TRACE "Under /etc/ash_functions:confirm_gpg_card"
	#Skip prompts if we are currently using a known GPG key material Thumb drive backup and keys are unlocked pinentry
	#TODO: probably export CONFIG_GPG_KEY_BACKUP_IN_USE but not under /etc/user.config?
	#Toggle to come in next PR, but currently we don't have a way to toggle it back to n if config.user flashed back in rom
	if [[ "$CONFIG_HAVE_GPG_KEY_BACKUP" == "y" && "$CONFIG_GPG_KEY_BACKUP_IN_USE" == "y" ]]; then
		DEBUG "Using known GPG key material Thumb drive backup and keys are unlocked and useable through pinentry"
		return
	fi

	if [ "$CONFIG_HAVE_GPG_KEY_BACKUP" == "y" ]; then
		message="Please confirm that your GPG card is inserted(Y/n) or your GPG key material (b)backup thumbdrive is inserted [Y/n/b]: "
	else
		# Generic message if no known key material backup
		message="Please confirm that your GPG card is inserted [Y/n]: "
	fi

	read \
		-n 1 \
		-p "$message" \
		card_confirm
	echo

	if [ "$card_confirm" != "y" \
		-a "$card_confirm" != "Y" \
		-a "$card_confirm" != "b" \
		-a -n "$card_confirm" ] \
		; then
		die "gpg card not confirmed"
	fi

	# If user has known GPG key material Thumb drive backup and asked to use it
	if [[ "$CONFIG_HAVE_GPG_KEY_BACKUP" == "y" && "$card_confirm" == "b" ]]; then
		#Only mount and import GPG key material thumb drive backup once
		if [ ! "$CONFIG_GPG_KEY_BACKUP_IN_USE" == "y" ]; then
			CR_NONCE="/tmp/secret/cr_nonce"
			CR_SIG="$CR_NONCE.sig"

			#Wipe any previous CR_NONCE and CR_SIG
			shred -n 10 -z -u "$CR_NONCE" "$CR_SIG" >/dev/null 2>&1 || true

			#Prompt user for configured GPG Admin PIN that will be passed along to mount-usb and to import gpg subkeys
			echo
			gpg_admin_pin=""
			while [ -z "$gpg_admin_pin" ]; do
				#TODO: change all passphrase prompts in codebase to include -r to prevent backslash escapes
				read -r -s -p "Please enter GPG Admin PIN needed to use the GPG backup thumb drive: " gpg_admin_pin
				echo
			done
			#prompt user to select the proper encrypted partition, which should the first one on next prompt
			warn "Please select encrypted LUKS on GPG key material backup thumb drive (not public labeled one)"
			mount-usb --pass "$gpg_admin_pin" || die "Unable to mount USB with provided GPG Admin PIN"
			echo "++++ Testing detach-sign operation and verifiying against fused public key in ROM"
			gpg --pinentry-mode=loopback --passphrase-file <(echo -n "${gpg_admin_pin}") --import /media/subkeys.sec >/dev/null 2>&1 ||
				die "Unable to import GPG private subkeys"
			#Do a detach signature to ensure gpg material is usable and cache passphrase to sign /boot from caller functions
			dd if=/dev/urandom of="$CR_NONCE" bs=20 count=1 >/dev/null 2>&1 ||
				die "Unable to create $CR_NONCE to be detach-signed with GPG private signing subkey"
			gpg --pinentry-mode=loopback --passphrase-file <(echo -n "${gpg_admin_pin}") --detach-sign "$CR_NONCE" >/dev/null 2>&1 ||
				die "Unable to detach-sign $CR_NONCE with GPG private signing subkey using GPG Admin PIN"
			#verify detached signature against public key in rom
			gpg --verify "$CR_SIG" "$CR_NONCE" > /dev/null 2>&1 && \
        			echo "++++ Local GPG keyring can be used to sign/encrypt/authenticate in this boot session ++++"  || \
			 	die "Unable to verify $CR_SIG detached signature against public key in ROM"
			#Wipe any previous CR_NONCE and CR_SIG
			shred -n 10 -z -u "$CR_NONCE" "$CR_SIG" >/dev/null 2>&1 || true
			#TODO: maybe just an export instead of setting /etc/user.config otherwise could be flashed in weird corner case situation
			set_user_config "CONFIG_GPG_KEY_BACKUP_IN_USE" "y"
			umount /media || die "Unable to unmount USB"
			return
		fi
	fi

	# setup the USB so we can reach the USB Security Dongle's smartcard
	enable_usb

	echo -e "\nVerifying presence of GPG card...\n"
	# ensure we don't exit without retrying
	errexit=$(set -o | grep errexit | awk '{print $2}')
	set +e
	gpg --card-status >/dev/null
	if [ $? -ne 0 ]; then
		# prompt for reinsertion and try a second time
		read -n1 -r -p \
			"Can't access GPG key; remove and reinsert, then press Enter to retry. " \
			ignored
		# restore prev errexit state
		if [ "$errexit" = "on" ]; then
			set -e
		fi
		# retry card status
		gpg --card-status >/dev/null ||
			die "gpg card read failed"
	fi
	# restore prev errexit state
	if [ "$errexit" = "on" ]; then
		set -e
	fi
}

gpg_auth() {
	if [[ "$CONFIG_HAVE_GPG_KEY_BACKUP" == "y" ]]; then
		TRACE "Under /etc/ash_functions:gpg_auth"
		# If we have a GPG key backup, we can use it to authenticate even if the card is lost
		echo >&2 "!!!!! Please authenticate with OpenPGP smartcard/backup media to prove you are the owner of this machine !!!!!"

		# Wipe any existing nonce and signature
		shred -n 10 -z -u "$CR_NONCE" "$CR_SIG" 2>/dev/null || true
		
		# In case of gpg_auth, we require confirmation of the card, so loop with confirm_gpg_card until we get it
		false
		while [ $? -ne 0 ]; do
			# Call confirm_gpg_card in subshell to ensure GPG key material presence
			( confirm_gpg_card )
		done

		# Perform a signing-based challenge-response,
		# to authencate that the card plugged in holding
		# the key to sign the list of boot files.
	
		CR_NONCE="/tmp/secret/cr_nonce"
		CR_SIG="$CR_NONCE.sig"

		# Generate a random nonce
		dd \
			if=/dev/urandom \
			of="$CR_NONCE" \
			count=1 \
			bs=20 \
			2>/dev/null \
			|| die "Unable to generate 20 random bytes"
	
		# Sign the nonce
		for tries in 1 2 3; do
			if gpg --digest-algo SHA256 \
				--detach-sign \
				-o "$CR_SIG" \
				"$CR_NONCE" > /dev/null 2>&1 \
				&& gpg --verify "$CR_SIG" "$CR_NONCE" > /dev/null 2>&1 \
			; then
				shred -n 10 -z -u "$CR_NONCE" "$CR_SIG" 2>/dev/null || true
				DEBUG "Under /etc/ash_functions:gpg_auth: success"
				return 0
			else
				shred -n 10 -z -u "$CR_SIG" 2>/dev/null || true
				if [ "$tries" -lt 3 ]; then
					echo >&2 "!!!!! GPG authentication failed, please try again !!!!!"
					continue
				else
					die "GPG authentication failed, please reboot and try again"
				fi
			fi
		done
		return 1		
	fi
}

recovery() {
	TRACE "Under /etc/ash_functions:recovery"
	echo >&2 "!!!!! $*"

	# Remove any temporary secret files that might be hanging around
	# but recreate the directory so that new tools can use it.

	#safe to always be true. Otherwise "set -e" would make it exit here
	shred -n 10 -z -u /tmp/secret/* 2> /dev/null || true
	rm -rf /tmp/secret
	mkdir -p /tmp/secret

	# ensure /tmp/config exists for recovery scripts that depend on it
	touch /tmp/config
	. /tmp/config

	DEBUG "Board $CONFIG_BOARD - version $(fw_version)"

	if [ "$CONFIG_TPM" = "y" ]; then
		echo "TPM: Extending PCR[4] to prevent any further secret unsealing"
		tpmr extend -ix 4 -ic recovery
	fi

	if [ "$CONFIG_RESTRICTED_BOOT" = y ]; then
		echo >&2 "Restricted Boot enabled, recovery console disabled, rebooting in 5 seconds"
		sleep 5
		/bin/reboot
	fi
	while [ true ]
	do
		#Going to recovery shell should be authenticated if supported
                gpg_auth

		echo >&2 "!!!!! Starting recovery shell"
		sleep 1
		
		if [ -x /bin/setsid ]; then
			/bin/setsid -c /bin/sh
		else
			/bin/sh
		fi
	done
}

pause_recovery() {
	TRACE "Under /etc/ash_functions:pause_recovery"
	read -p $'!!! Hit enter to proceed to recovery shell !!!\n'
	recovery $*
}

combine_configs() {
	TRACE "Under /etc/ash_functions:combine_configs"
	cat /etc/config* > /tmp/config
}

replace_config() {
        TRACE "Under /etc/functions:replace_config"
        CONFIG_FILE=$1
        CONFIG_OPTION=$2
        NEW_SETTING=$3

        touch $CONFIG_FILE
        # first pull out the existing option from the global config and place in a tmp file
        awk "gsub(\"^export ${CONFIG_OPTION}=.*\",\"export ${CONFIG_OPTION}=\\\"${NEW_SETTING}\\\"\")" /tmp/config >${CONFIG_FILE}.tmp
        awk "gsub(\"^${CONFIG_OPTION}=.*\",\"${CONFIG_OPTION}=\\\"${NEW_SETTING}\\\"\")" /tmp/config >>${CONFIG_FILE}.tmp

        # then copy any remaining settings from the existing config file, minus the option you changed
        grep -v "^export ${CONFIG_OPTION}=" ${CONFIG_FILE} | grep -v "^${CONFIG_OPTION}=" >>${CONFIG_FILE}.tmp || true
        sort ${CONFIG_FILE}.tmp | uniq >${CONFIG_FILE}
        rm -f ${CONFIG_FILE}.tmp
}

# Set a config variable in a specific file to a given value - replace it if it
# exists, or add it.  If added, the variable will be exported.
set_config() {
        CONFIG_FILE="$1"
        CONFIG_OPTION="$2"
        NEW_SETTING="$3"

        if grep -q "$CONFIG_OPTION" "$CONFIG_FILE"; then
                replace_config "$CONFIG_FILE" "$CONFIG_OPTION" "$NEW_SETTING"
        else
                echo "export $CONFIG_OPTION=\"$NEW_SETTING\"" >>"$CONFIG_FILE"
        fi
}

# Set a value in config.user, re-combine configs, and update configs in the
# environment.
set_user_config() {
        CONFIG_OPTION="$1"
        NEW_SETTING="$2"

        set_config /etc/config.user "$CONFIG_OPTION" "$NEW_SETTING"
        combine_configs
        . /tmp/config
}

# Load a config value to a variable, defaulting to empty.  Does not fail if the
# config is not set (since it would expand to empty by default).
load_config_value() {
        local config_name="$1"
        if grep -q "$config_name=" /tmp/config; then
                grep "$config_name=" /tmp/config | tail -n1 | cut -f2 -d '=' | tr -d '"'
        fi
}

enable_usb()
{
	TRACE "Under /etc/ash_functions:enable_usb"
	#insmod ehci_hcd prior of uhdc_hcd and ohci_hcd to suppress dmesg warning 
	insmod /lib/modules/ehci-hcd.ko || die "ehci_hcd: module load failed"
	
	if [ "$CONFIG_LINUX_USB_COMPANION_CONTROLLER" = y ]; then
		insmod /lib/modules/uhci-hcd.ko || die "uhci_hcd: module load failed"
		insmod /lib/modules/ohci-hcd.ko || die "ohci_hcd: module load failed"
		insmod /lib/modules/ohci-pci.ko || die "ohci_pci: module load failed"
	fi
	insmod /lib/modules/ehci-pci.ko || die "ehci_pci: module load failed"
	insmod /lib/modules/xhci-hcd.ko || die "xhci_hcd: module load failed"
	insmod /lib/modules/xhci-pci.ko || die "xhci_pci: module load failed"
	sleep 2

	# For resiliency, test CONFIG_USB_KEYBOARD_REQUIRED explicitly rather
	# than having it imply CONFIG_USER_USB_KEYBOARD at build time.
	# Otherwise, if a user got CONFIG_USER_USB_KEYBOARD=n in their
	# config.user by mistake (say, by copying config.user from a laptop to a
	# desktop/server), they could lock themselves out, only recoverable by
	# hardware flash.
	if [ "$CONFIG_USB_KEYBOARD_REQUIRED" = y ] || [ "$CONFIG_USER_USB_KEYBOARD" = y ]; then
		insmod /lib/modules/usbhid.ko || die "usbhid: module load failed"
	fi
}