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Jan 12, 2021
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intrigeri
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more_efficient_memory_wipe.md
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[[!tag archived]]
After following the steps for "[[contribute/release_process/test/erase_memory_on_shutdown]]"
After following the steps for "
[
erase memory on shutdown
](
https://tails.boum.org/contribute/release_process/test/erase_memory_on_shutdown
)
"
it turns out some patterns may survive the wipe which indicates that
it turns out some patterns may survive the wipe which indicates that
not all memory was wiped. One theory for this is that the new kernel
not all memory was wiped. One theory for this is that the new kernel
loaded by kexec may allocate some buffer, which then is filled with
loaded by kexec may allocate some buffer, which then is filled with
...
@@ -11,12 +11,14 @@ This was supposedly not a problem for some testers prior to Tails 0.8
...
@@ -11,12 +11,14 @@ This was supposedly not a problem for some testers prior to Tails 0.8
but I can reliably reproduce this problem on a machine (with 4 GB or
but I can reliably reproduce this problem on a machine (with 4 GB or
RAM if that matters) with both Tails 0.8 and 0.7.2.
RAM if that matters) with both Tails 0.8 and 0.7.2.
[[!toc levels=2]]
[[
_TOC_
]]
Roadmap
Roadmap
=======
=======
*
wait for [
[
todo/hugetlb_mem_wipe
]]
to be fine
*
wait for
[
hugetlb mem wipe
](
https://tails.boum.org/
todo/hugetlb_mem_wipe
)
to be fine
tuned and finished.
tuned and finished.
Implementation ideas
Implementation ideas
...
@@ -41,8 +43,8 @@ initramfs + sdmem
...
@@ -41,8 +43,8 @@ initramfs + sdmem
> the 3 GiB limit has anything to do with the unwiped patterns you
> the 3 GiB limit has anything to do with the unwiped patterns you
> have seen thus far, retry on a system with less than 3 GiB RAM. --MK
> have seen thus far, retry on a system with less than 3 GiB RAM. --MK
>> Right. Updated the
[
[testing
>> Right. Updated the [testing
>> documentation
|
contribute/release_process/test/erase_memory_on_shutdown
]]
>> documentation
](https://tails.boum.org/
contribute/release_process/test/erase_memory_on_shutdown
)
>> accordingly. Thanks for pointing this out. --intrigeri
>> accordingly. Thanks for pointing this out. --intrigeri
Possible fixes (180f058 + 0f1f476d) now waiting to be tested in devel branch.
Possible fixes (180f058 + 0f1f476d) now waiting to be tested in devel branch.
...
@@ -72,10 +74,10 @@ using the Linux kernel's `memtest=2` feature, which is simpler, more
...
@@ -72,10 +74,10 @@ using the Linux kernel's `memtest=2` feature, which is simpler, more
robust, and allows wiping more RAM. This option will be
robust, and allows wiping more RAM. This option will be
enabled in the next (> 3.1.4-1) Debian kernel.
enabled in the next (> 3.1.4-1) Debian kernel.
=> registered as a
[
[TODO page
|
todo/move_from_sdmem_to_memtest
]]
with
=> registered as a
[
TODO page
](
https://tails.boum.org/
todo/move_from_sdmem_to_memtest
)
with
actual action plans.
actual action plans.
This needs to kexec a specific [
[
todo/amd64_kernel
]]
when possible to
This needs to kexec a specific
[
amd64 kernel
](
https://tails.boum.org/
todo/amd64_kernel
)
when possible to
be of any use on systems with more than 1 GB of memory.
be of any use on systems with more than 1 GB of memory.
Testing results:
Testing results:
...
@@ -99,10 +101,10 @@ of a regular Linux kernel + ramdisk + userspace memory erasure
...
@@ -99,10 +101,10 @@ of a regular Linux kernel + ramdisk + userspace memory erasure
program. This is probably the only way to overwrite
**all**
memory
program. This is probably the only way to overwrite
**all**
memory
that was used in Tails.
that was used in Tails.
An experiment has been done on
[
[patching memtest86+
|
memtest86plus
]]
An experiment has been done on
[
patching memtest86+
](
more_efficient_memory_wipe/
memtest86plus
)
to do this job.
to do this job.
Another experiment with
[
[GRUB
|
grub
]]
is in progress.
Another experiment with
[
GRUB
](
more_efficient_memory_wipe/
grub
)
is in progress.
Other ideas
Other ideas
-----------
-----------
...
@@ -114,3 +116,4 @@ Other ideas
...
@@ -114,3 +116,4 @@ Other ideas
process. This makes it harder to implement a nice progress bar...
process. This makes it harder to implement a nice progress bar...
But yeah, combination of dd, pv and a tmpfs should also be able to
But yeah, combination of dd, pv and a tmpfs should also be able to
do a faire amount of wiping.
do a faire amount of wiping.