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recognize zram as swap
Check if unencrypted swap is zram. If it is zram check whether a writeback to disk is configured. Unencrypted zramswap not written to disk is accepted. ToDo (as for other unencrypted swap): check if the writeback happens on an already encrypted disk/partition.
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tomb
95
tomb
@ -293,6 +293,84 @@ _tmp_create() {
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}
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# Check if a *block* device is encrypted
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# Check if a *block* device is a zram device
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# Synopsis: _is_zramswap /path/to/block/device
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# Return 0 if it is a zramswap
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# Return 1 if it is not a zramswap
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_is_zramswap() {
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local b=$1 # Path to a block device
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# check if device b is a zram block device
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zramctl --raw -o NAME | grep "^$b" >/dev/null
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return $?
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}
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# Check if a zram device uses the writeback feature that writes data onto a disk
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# Synopsis: _zramswap_uses_writeback /path/to/block/device
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# Return 0 if the zram device writes to disk
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# Return 1 if the zram device does not write to disk
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_zramswap_uses_writeback() {
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local b=$1 # Path to a block device
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local m="" # major device number
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local n="" # minor device number
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read n m < <(stat -c '%T %t' $b) # get major and minor device number in hex
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printf -v m %d $((16#$m)) # get major device number in decimal
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printf -v n %d $((16#$n)) # get minor device number in decimal
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if grep '^none$' "/sys/dev/block/$m:$n/backing_dev" > /dev/null; then
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return 1
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fi
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return 0
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}
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# Check if a *block* device is a zram device
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# Synopsis: _is_zramswap /path/to/block/device
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# Return 0 if it is a zramswap
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# Return 1 if it is not a zramswap
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_is_zramswap() {
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local b=$1 # Path to a block device
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zramctl --raw -o NAME | grep "^$b" >/dev/null
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# @todo How to do this without zramctl?
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# - device node major is dynamically allocated to zram0
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# - in /sys/ there seems to be no file identifying a zram device
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return $?
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}
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# Check if a zram device uses the writeback feature that writes data onto a disk
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# Synopsis: _zramswap_uses_writeback /path/to/block/device
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# Return 0 if the zram device writes to disk
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# Return 1 if the zram device does not write to disk
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elif _is_zramswap $s; then
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if _zramswap_uses_writeback $s; then
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# We're dealing with unencrypted stuff written to disk.
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# Maybe it lives on an encrypted filesystem anyway.
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# @todo verify it's actually written to an encrypted FS
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# Well, no: bail out.
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r=1; break;
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else
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r=2;
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fi
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_zramswap_uses_writeback() {
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local b=$1 # Path to a block device
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local m="" # major device number
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local n="" # minor device number
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read n m < <(stat -c '%T %t' $b) # get major and minor device number in hex
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printf -v m %d $((16#$m)) # get major device number in decimal
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printf -v n %d $((16#$n)) # get minor device number in decimal
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if grep '^none$' "/sys/dev/block/$m:$n/backing_dev" > /dev/null; then
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return 1
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fi
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return 0
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}
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# Synopsis: _is_encrypted_block /path/to/block/device
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# Return 0 if it is an encrypted block device
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_is_encrypted_block() {
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@ -314,7 +392,7 @@ _is_encrypted_block() {
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# Check if swap is activated
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# Return 0 if NO swap is used, 1 if swap is used.
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# Return 1 if any of the swaps is not encrypted.
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# Return 2 if swap(s) is(are) used, but ALL encrypted.
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# Return 2 if swap(s) is(are) used, but ALL encrypted or zramswap without writeback to disk.
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# Use _check_swap in functions. It will call this function and
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# exit if unsafe swap is present.
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_ensure_safe_swap() {
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@ -330,8 +408,18 @@ _ensure_safe_swap() {
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for s in $=swaps; do
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if _is_encrypted_block $s; then
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r=2;
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elif _is_zramswap $s; then
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if _zramswap_uses_writeback $s; then
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# We're dealing with unencrypted stuff written to disk.
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# Maybe it lives on an encrypted filesystem anyway.
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# @todo verify it's actually written to an encrypted FS
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# Well, no: bail out.
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r=1; break;
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else
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r=2;
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fi
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else
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# We're dealing with unencrypted stuff.
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# We're dealing with unencrypted stuff written to disk.
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# Maybe it lives on an encrypted filesystem anyway.
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# @todo: verify it's actually on an encrypted FS (see #163 and !189)
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# Well, no: bail out.
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@ -340,7 +428,8 @@ _ensure_safe_swap() {
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done
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if [[ $r -eq 2 ]]; then
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_success "The undertaker found that all swap partitions are encrypted. Good."
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_success "The undertaker found that all swap partitions are encrypted"
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_success "or zramswap without writeback to disk. Good."
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else
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_warning "This poses a security risk."
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_warning "You can deactivate all swap partitions using the command:"
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