Date: Thu, 16 Apr 2020 13:33:08 +0200
From: Natanael Copa <ncopa@alpinelinux.org>
To: Drew DeVault <sir@cmpwn.com>
Cc: ~alpine/devel@lists.alpinelinux.org
Subject: Re: [PATCH v5] Support encrypted root in setup-disk
Message-ID: <20200416133308.0f6b27b7@ncopa-desktop.copa.dup.pw>
In-Reply-To: <20200121184924.99939-1-sir@cmpwn.com>
References: <20200121184924.99939-1-sir@cmpwn.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
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Hi!

Finally having a look at this.

We also need add some help test in diskmode_help that explains what cryptsys does.

I think we should also keep in mind that we may want support encrypted
data or encrypted lvm in the future.

See also comments inline below.


-nc


On Tue, 21 Jan 2020 13:49:24 -0500
Drew DeVault <sir@cmpwn.com> wrote:

> ---
> This should be the one. It addresses Nathaniel's feedback from IRC and
> has been tested on new installs.
> 
>  setup-disk.in | 101 +++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 80 insertions(+), 21 deletions(-)
> 
> diff --git a/setup-disk.in b/setup-disk.in
> index 5eb8638..71c2602 100644
> --- a/setup-disk.in
> +++ b/setup-disk.in
> @@ -79,6 +79,26 @@ enumerate_fstab() {
>  		done
>  }
>  
> +# given an fstab on stdin, determine if any of the mountpoints are encrypted
> +crypt_required() {
> +	while read devname mountpoint fstype mntops freq passno; do
> +		if [ -z "$devname" ] || [ "${devname###}" != "$devname" ]; then
> +			continue
> +		fi
> +		uuid="${devname##UUID=}"
> +		if [ "$uuid" != "$devname" ]; then
> +			devname="$(blkid --uuid "$uuid")"
> +		fi
> +		mapname="${devname##/dev/mapper/}"
> +		if [ "$mapname" != "$devname" ]; then
> +			if cryptsetup status "$mapname" >&1 >/dev/null; then
> +				return 0
> +			fi
> +		fi
> +	done
> +	return 1
> +}
> +
>  is_vmware() {
>  	grep -q VMware /proc/scsi/scsi 2>/dev/null \
>  		|| grep -q VMware /proc/ide/hd*/model 2>/dev/null
> @@ -343,7 +363,7 @@ setup_syslinux() {
>  install_mounted_root() {
>  	local mnt="$1"
>  	shift 1
> -	local disks="${@}" mnt_boot= boot_fs= root_fs=
> +	local disks="${@}" mnt_boot= boot_fs= root_fs= use_crypt=
>  	local initfs_features="ata base ide scsi usb virtio"
>  	local pvs= dev= rootdev= bootdev= extlinux_raidopt= root= modules=
>  	local kernel_opts="quiet"
> @@ -402,7 +422,6 @@ install_mounted_root() {
>  		esac
>  	done
>  
> -
>  	if [ -n "$VERBOSE" ]; then
>  		echo "Root device:     $rootdev"
>  		echo "Root filesystem: $root_fs"
> @@ -425,6 +444,28 @@ install_mounted_root() {
>  	# we should not try start modloop on sys install
>  	rm -f "$mnt"/etc/runlevels/*/modloop
>  
> +	# generate the fstab
> +	if [ -f "$mnt"/etc/fstab ]; then
> +		mv "$mnt"/etc/fstab "$mnt"/etc/fstab.old
> +	fi
> +	enumerate_fstab "$mnt" >> "$mnt"/etc/fstab
> +	if [ -n "$SWAP_DEVICES" ]; then
> +		local swap_dev
> +		for swap_dev in $SWAP_DEVICES; do
> +			echo -e "$(uuid_or_device ${swap_dev})\tswap\tswap\tdefaults\t0 0" \
> +				>> "$mnt"/etc/fstab
> +		done
> +	fi
> +	cat >>"$mnt"/etc/fstab <<-__EOF__
> +		/dev/cdrom	/media/cdrom	iso9660	noauto,ro 0 0
> +		/dev/usbdisk	/media/usb	vfat	noauto	0 0
> +	__EOF__
> +
> +	if crypt_required <"$mnt"/etc/fstab; then

Maybe use sed to remove comments here?

  sed 's/#.*//' "$mnt"/etc/fstab | crypt_required

> +		use_crypt=1
> +		initfs_features="${initfs_features% cryptsetup} cryptsetup"

initfs_features should only be modified if the rootdev is encrypted and
not if any other mounts are.

> +	fi
> +
>  	# generate mkinitfs.conf
>  	mkdir -p "$mnt"/etc/mkinitfs/features.d
>  	echo "features=\"$initfs_features\"" > "$mnt"/etc/mkinitfs/mkinitfs.conf
> @@ -442,24 +483,14 @@ install_mounted_root() {
>  	if [ -n "$(get_bootopt nomodeset)" ]; then
>  		kernel_opts="nomodeset $kernel_opts"
>  	fi
> +	if [ "$use_crypt" ] && cryptsetup status "$rootdev" 2>&1 >/dev/null; then
> +		# Boot to encrypted root
> +		root=$(cryptsetup status "$rootdev" | awk '/device:/ { print $2 }')
> +		kernel_opts="cryptroot=$root cryptdm=root"
> +		root=/dev/mapper/root
> +	fi
>  	modules="sd-mod,usb-storage,${root_fs}${raidmod}"
>  
> -	# generate the fstab
> -	if [ -f "$mnt"/etc/fstab ]; then
> -		mv "$mnt"/etc/fstab "$mnt"/etc/fstab.old
> -	fi
> -	enumerate_fstab "$mnt" >> "$mnt"/etc/fstab
> -	if [ -n "$SWAP_DEVICES" ]; then
> -		local swap_dev
> -		for swap_dev in $SWAP_DEVICES; do
> -			echo -e "$(uuid_or_device ${swap_dev})\tswap\tswap\tdefaults\t0 0" \
> -				>> "$mnt"/etc/fstab  
> -		done
> -	fi
> -	cat >>"$mnt"/etc/fstab <<-__EOF__
> -		/dev/cdrom	/media/cdrom	iso9660	noauto,ro 0 0
> -		/dev/usbdisk	/media/usb	vfat	noauto	0 0
> -	__EOF__
>  	# remove the installed db in case its there so we force re-install
>  	rm -f "$mnt"/var/lib/apk/installed "$mnt"/lib/apk/db/installed
>  	echo "Installing system on $rootdev:"
> @@ -503,6 +534,10 @@ unmount_partitions() {
>  
>  	# unmount the partitions
>  	umount $(awk '{print $2}' /proc/mounts | egrep "^$mnt(/|\$)" | sort -r)
> +
> +	if [ "$USE_CRYPT" ]; then
> +		cryptsetup close /dev/mapper/root
> +	fi
>  }
>  
>  # figure out decent default swap size in mega bytes
> @@ -994,6 +1029,18 @@ native_disk_install_lvm() {
>  	setup_root $root_dev $BOOT_DEV
>  }
>  
> +setup_crypt() {
> +	mkdir -p /run/cryptsetup
> +	echo "Preparing root partition for encryption." >&2
> +	echo "You will be prompted for your password at boot." >&2
> +	echo "If you forget your password, your data will be lost." >&2
> +	cryptsetup luksFormat --type luks2 "$1" >&2
> +	echo "Enter password again to unlock disk for installation." >&2
> +	cryptsetup open "$1" root >&2
> +	cryptroot="$1"
> +	echo "/dev/mapper/root"
> +}

I think we should pass "root" as an argument so it can be reused for a
encrypted data partition in the future.

setup_crypt() {
	local dev="$1" local dmname="$2"
	...
	echo "Preparing your $dmname partition for encryption."
	...
	cryptsetup open "$dev" "$dmname"
}

That way we also don't need send the prompt to stderr.

> +
>  native_disk_install() {
>  	local prep_part_type=$(partition_id prep)
>  	local root_part_type=$(partition_id linux)
> @@ -1065,6 +1112,10 @@ native_disk_install() {
>  		root_dev=$(find_nth_non_boot_parts $index "$root_part_type" $@)
>  	fi
>  
> +	if [ "$USE_CRYPT" ]; then
> +		root_dev=$(setup_crypt $root_dev)
> +	fi

Maybe something like if we do the above setup_crypt adjustment:

	if [ "$USE_CRYPT" ]; then
		setup_crypt $root_dev root
		root_dev=/dev/mapper/root
	fi
	

> +
>  	[ $SWAP_SIZE -gt 0 ] && setup_swap_dev $swap_dev
>  	setup_root $root_dev $BOOT_DEV $@
>  }
> @@ -1143,7 +1194,7 @@ ask_disk() {
>  
>  usage() {
>  	cat <<-__EOF__
> -		usage: setup-disk [-hLqrv] [-k kernelflavor] [-m MODE] [-o apkovl] [-s SWAPSIZE]
> +		usage: setup-disk [-hLqrve] [-k kernelflavor] [-m MODE] [-o apkovl] [-s SWAPSIZE]
>  		                  [MOUNTPOINT | DISKDEV...]
>  
>  		Install alpine on harddisk.
> @@ -1157,6 +1208,7 @@ usage() {
>  
>  		options:
>  		 -h  Show this help
> +		 -e  Encrypt disk
>  		 -m  Use disk for MODE without asking, where MODE is either 'data' or 'sys'
>  		 -o  Restore system from given apkovl file
>  		 -k  Use kernelflavor instead of $KERNEL_FLAVOR
> @@ -1193,11 +1245,13 @@ case $kver in
>  	*) KERNEL_FLAVOR=vanilla;;
>  esac
>  
> +USE_CRYPT=
>  DISK_MODE=
>  USE_LVM=
>  # Parse args
> -while getopts "hk:Lm:o:qrs:v" opt; do
> +while getopts "hek:Lm:o:qrs:v" opt; do
>  	case $opt in
> +		e) USE_CRYPT=1;;
>  		m) DISK_MODE="$OPTARG";;
>  		k) KERNEL_FLAVOR="$OPTARG";;
>  		L) USE_LVM="_lvm";;
> @@ -1275,10 +1329,15 @@ if [ -n "$diskdevs" ] && [ -z "$DISK_MODE" ]; then
>  		echo "The following $disk_is_or_disks_are selected${USE_LVM:+ (with LVM)}:"
>  		show_disk_info $diskdevs
>  		_lvm=${USE_LVM:-", 'lvm'"}
> -		echon "How would you like to use $it_them? ('sys', 'data'${_lvm#_lvm} or '?' for help) [?] "
> +		echon "How would you like to use $it_them? ('sys', 'cryptsys', 'data'${_lvm#_lvm} or '?' for help) [?] "
>  		default_read answer '?'
>  		case "$answer" in
>  		'?') diskmode_help;;
> +		cryptsys)
> +			answer=sys
> +			USE_CRYPT=1
> +			break
> +			;;
>  		sys|data) break;;
>  		lvm) USE_LVM="_lvm" ;;
>  		nolvm) USE_LVM="";;

What happens if you enable bot encryption and lvm (setup-disk -e -L)? should we error out and say its not yet supported?

Thanks!

-nc