Date: Mon, 21 Mar 2022 10:17:33 -0500 From: Sam Ricchio <sam.ricchio@gmail.com> To: Damian Weber <dweber@htwsaar.de>, freebsd-security@freebsd.org Subject: Re: SSD erase question Message-ID: <1ACC7A67-BDBA-4CD3-87EC-822C38CD7CE7@gmail.com> In-Reply-To: <274c8cca-80b0-9460-6754-6bb77efbb4dd@htwsaar.de> References: <274c8cca-80b0-9460-6754-6bb77efbb4dd@htwsaar.de>
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On and SSD if you have erased everything ssd =E2=80=9Cgarbage =
collection=E2=80=9D should help you if the drive it powered on.
But if you want to overwrite the drive
A simple overwrite with a text pattern with dc3dd.
dc3dd wipe=3D/dev/sdb tpat=3Dnothingtoseehere
However if you are still worried that some controller optimization is =
interfering
with and actual memory location overwrite. Go old school with dd and =
write
a file of random to the existing file system until it runs out of space.
dd if=3D/dev/urandon of=3Dgarbagetxtfile.txt
On Mar 21, 2022, at 7:14 AM, Damian Weber <dweber@htwsaar.de> wrote:
Hi all,
I'd like to have an answer on a secure FreeBSD way to erase=20
SSDs before giving these away to someone for reusing it.=20
Is the following enough to protect confidential data=20
previously stored there?
1) dd : overwriting with random bits (complete capacity)
2) gpart create
3) gpart add
4) newfs
Details for an example with /dev/ada1 see below.
Thanks a lot,
Damian
# fdisk ada1
******* Working on device /dev/ada1 *******
parameters extracted from in-core disklabel are:
cylinders=3D484521 heads=3D16 sectors/track=3D63 (1008 blks/cyl)
Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=3D484521 heads=3D16 sectors/track=3D63 (1008 blks/cyl)
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 238 (0xee),(EFI GPT)
start 1, size 488397167 (238475 Meg), flag 0
beg: cyl 0/ head 0/ sector 2;
end: cyl 1023/ head 255/ sector 63
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>
# gpart show ada1
=3D> 40 488397088 ada1 GPT (233G)
40 1024 1 freebsd-boot (512K)
1064 480246784 2 freebsd-ufs [bootme] (229G)
480247848 8149280 3 freebsd-swap (3.9G)
# dd if=3D/dev/random of=3D/dev/ada1 bs=3D512 count=3D488397088
# gpart create -s gpt ada1
# gpart add -t freebsd-ufs ada1
# newfs -U /dev/ada1p1
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<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; =
charset=3Dutf-8"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; line-break: after-white-space;" class=3D""><div =
class=3D"">On and SSD if you have erased everything ssd =E2=80=9Cgarbage =
collection=E2=80=9D should help you if the drive it powered =
on.</div><div class=3D"">But if you want to overwrite the =
drive</div><div class=3D"">A simple overwrite with a text pattern with =
dc3dd.</div><div class=3D""><div style=3D"margin: 0px 0px 0px 36px; =
text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: =
normal;" class=3D""><span style=3D"font-kerning: none" class=3D"">dc3dd =
wipe=3D/dev/sdb tpat=3Dnothingtoseehere</span></div><div style=3D"margin: =
0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: =
16px; line-height: normal;" class=3D""><span style=3D"font-kerning: =
none" class=3D"">However if you are still worried that some controller =
optimization is interfering</span></div><div style=3D"margin: 0px 0px =
0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; =
line-height: normal;" class=3D""><span style=3D"font-kerning: none" =
class=3D"">with and actual memory location overwrite. Go old =
school with dd and write</span></div><div style=3D"margin: 0px 0px 0px =
36px; text-indent: -36px; font-stretch: normal; font-size: 16px; =
line-height: normal;" class=3D""><span style=3D"font-kerning: none" =
class=3D"">a file of random to the existing file system until it runs =
out of space.</span></div><div style=3D"margin: 0px 0px 0px 36px; =
text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: =
normal;" class=3D""><span style=3D"font-kerning: none" class=3D"">dd =
if=3D/dev/urandon of=3Dgarbagetxtfile.txt</span></div><div =
style=3D"margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: =
normal; font-size: 16px; line-height: normal;" class=3D""><span =
style=3D"font-kerning: none" class=3D""><br class=3D""></span></div><div =
style=3D"margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: =
normal; font-size: 16px; line-height: normal;" class=3D""><span =
style=3D"font-kerning: none" class=3D""><br class=3D""></span></div><div =
style=3D"margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: =
normal; font-size: 16px; line-height: normal;" class=3D""><span =
style=3D"font-kerning: none" class=3D""><br class=3D""></span></div><div =
style=3D"margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: =
normal; font-size: 16px; line-height: normal;" class=3D""><br =
class=3D""></div><div class=3D""><div><div class=3D"">On Mar 21, 2022, =
at 7:14 AM, Damian Weber <<a href=3D"mailto:dweber@htwsaar.de" =
class=3D"">dweber@htwsaar.de</a>> wrote:</div><br =
class=3D"Apple-interchange-newline"><div class=3D""><div class=3D""><br =
class=3D"">Hi all,<br class=3D""><br class=3D"">I'd like to have an =
answer on a secure FreeBSD way to erase <br class=3D"">SSDs before =
giving these away to someone for reusing it. <br class=3D""><br =
class=3D"">Is the following enough to protect confidential data <br =
class=3D"">previously stored there?<br class=3D""><br class=3D"">1) =
dd : overwriting with random bits (complete capacity)<br =
class=3D"">2) gpart create<br class=3D"">3) gpart add<br =
class=3D"">4) newfs<br class=3D""><br class=3D"">Details for an =
example with /dev/ada1 see below.<br class=3D""><br class=3D"">Thanks a =
lot,<br class=3D""><br class=3D""> Damian<br class=3D""><br =
class=3D""><br class=3D""># fdisk ada1<br class=3D"">******* Working on =
device /dev/ada1 *******<br class=3D"">parameters extracted from in-core =
disklabel are:<br class=3D"">cylinders=3D484521 heads=3D16 =
sectors/track=3D63 (1008 blks/cyl)<br class=3D""><br class=3D"">Figures =
below won't work with BIOS for partitions not in cyl 1<br =
class=3D"">parameters to be used for BIOS calculations are:<br =
class=3D"">cylinders=3D484521 heads=3D16 sectors/track=3D63 (1008 =
blks/cyl)<br class=3D""><br class=3D"">Media sector size is 512<br =
class=3D"">Warning: BIOS sector numbering starts with sector 1<br =
class=3D"">Information from DOS bootblock is:<br class=3D"">The data for =
partition 1 is:<br class=3D"">sysid 238 (0xee),(EFI GPT)<br class=3D""> =
start 1, size 488397167 (238475 Meg), flag 0<br =
class=3D""> beg: cyl 0/ head =
0/ sector 2;<br class=3D""> =
end: cyl 1023/ head 255/ =
sector 63<br class=3D"">The data for partition 2 is:<br =
class=3D""><UNUSED><br class=3D"">The data for partition 3 is:<br =
class=3D""><UNUSED><br class=3D"">The data for partition 4 is:<br =
class=3D""><UNUSED><br class=3D""><br class=3D""># gpart show =
ada1<br class=3D"">=3D> 40 =
488397088 ada1 GPT (233G)<br class=3D""> =
40 =
1024 1 =
freebsd-boot (512K)<br class=3D""> =
1064 480246784 =
2 freebsd-ufs [bootme] =
(229G)<br class=3D""> 480247848 8149280 =
3 freebsd-swap (3.9G)<br =
class=3D""><br class=3D""># dd if=3D/dev/random of=3D/dev/ada1 bs=3D512 =
count=3D488397088<br class=3D""><br class=3D""># gpart create -s gpt =
ada1<br class=3D""><br class=3D""># gpart add -t freebsd-ufs ada1<br =
class=3D""><br class=3D""># newfs -U /dev/ada1p1<br class=3D""><br =
class=3D""><br class=3D""></div></div></div><br =
class=3D""></div></div></body></html>=
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