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>
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[-- Attachment #1 --]
On and SSD if you have erased everything ssd “garbage collection” 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=/dev/sdb tpat=nothingtoseehere
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=/dev/urandon of=garbagetxtfile.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
SSDs before giving these away to someone for reusing it.
Is the following enough to protect confidential data
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=484521 heads=16 sectors/track=63 (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=484521 heads=16 sectors/track=63 (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
=> 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=/dev/random of=/dev/ada1 bs=512 count=488397088
# gpart create -s gpt ada1
# gpart add -t freebsd-ufs ada1
# newfs -U /dev/ada1p1
[-- Attachment #2 --]
<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">On and SSD if you have erased everything ssd “garbage collection” should help you if the drive it powered on.</div><div class="">But if you want to overwrite the drive</div><div class="">A simple overwrite with a text pattern with dc3dd.</div><div class=""><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class="">dc3dd wipe=/dev/sdb tpat=nothingtoseehere</span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class="">However if you are still worried that some controller optimization is interfering</span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class="">with and actual memory location overwrite. Go old school with dd and write</span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class="">a file of random to the existing file system until it runs out of space.</span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class="">dd if=/dev/urandon of=garbagetxtfile.txt</span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class=""><br class=""></span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class=""><br class=""></span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><span style="font-kerning: none" class=""><br class=""></span></div><div style="margin: 0px 0px 0px 36px; text-indent: -36px; font-stretch: normal; font-size: 16px; line-height: normal;" class=""><br class=""></div><div class=""><div><div class="">On Mar 21, 2022, at 7:14 AM, Damian Weber <<a href="mailto:dweber@htwsaar.de" class="">dweber@htwsaar.de</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class=""><br class="">Hi all,<br class=""><br class="">I'd like to have an answer on a secure FreeBSD way to erase <br class="">SSDs before giving these away to someone for reusing it. <br class=""><br class="">Is the following enough to protect confidential data <br class="">previously stored there?<br class=""><br class="">1) dd : overwriting with random bits (complete capacity)<br class="">2) gpart create<br class="">3) gpart add<br class="">4) newfs<br class=""><br class="">Details for an example with /dev/ada1 see below.<br class=""><br class="">Thanks a lot,<br class=""><br class=""> Damian<br class=""><br class=""><br class=""># fdisk ada1<br class="">******* Working on device /dev/ada1 *******<br class="">parameters extracted from in-core disklabel are:<br class="">cylinders=484521 heads=16 sectors/track=63 (1008 blks/cyl)<br class=""><br class="">Figures below won't work with BIOS for partitions not in cyl 1<br class="">parameters to be used for BIOS calculations are:<br class="">cylinders=484521 heads=16 sectors/track=63 (1008 blks/cyl)<br class=""><br class="">Media sector size is 512<br class="">Warning: BIOS sector numbering starts with sector 1<br class="">Information from DOS bootblock is:<br class="">The data for partition 1 is:<br class="">sysid 238 (0xee),(EFI GPT)<br class=""> start 1, size 488397167 (238475 Meg), flag 0<br class=""> beg: cyl 0/ head 0/ sector 2;<br class=""> end: cyl 1023/ head 255/ sector 63<br class="">The data for partition 2 is:<br class=""><UNUSED><br class="">The data for partition 3 is:<br class=""><UNUSED><br class="">The data for partition 4 is:<br class=""><UNUSED><br class=""><br class=""># gpart show ada1<br class="">=> 40 488397088 ada1 GPT (233G)<br class=""> 40 1024 1 freebsd-boot (512K)<br class=""> 1064 480246784 2 freebsd-ufs [bootme] (229G)<br class=""> 480247848 8149280 3 freebsd-swap (3.9G)<br class=""><br class=""># dd if=/dev/random of=/dev/ada1 bs=512 count=488397088<br class=""><br class=""># gpart create -s gpt ada1<br class=""><br class=""># gpart add -t freebsd-ufs ada1<br class=""><br class=""># newfs -U /dev/ada1p1<br class=""><br class=""><br class=""></div></div></div><br class=""></div></div></body></html>
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