How not to securely erase a NVME drive (2022)

How not to securely erase a NVME drive (2022)(peterbabic.dev)

59 points by transpute 106 days ago | 54 comments

digiown 102 days ago |

And this is why you always encrypt the drive with software. All of these methods seem to put a lot of faith into the drive controller doing what it claim it does, which you can never be all that sure about. Even Microsoft-backed Bitlocker would help here.

fulafel 102 days ago | |

Bitlocker can rely on the SSD encryption, so careful there too.

wongogue 102 days ago | | |

It has been software encryption for a many years now.

Joel_Mckay 102 days ago | |

Indeed, LUKS + F2FS for /home with an external key file imported into initrd solves a lot of issues.

Primarily, when an SSD slowly fails the sector replacement allotment has already bled data into read-only areas of the drive. As a user, there is no way to reliably scrub that data.

If the drive suddenly bricks, the warranty service will often not return the original hardware... and just the password protection on an embedded LUKS key is not great.

There are effective disposal methods:

1. shred the chips

2. incinerate the chips

Wiping/Trim sometimes doesn't even work if the Flash chips are malfunctioning. =3

bruce343434 102 days ago | | |

What's wrong with the LUKS password protection?

tokyobreakfast 102 days ago | | |

> an external key file imported into initrd

This is exceptionally poor advice. This is why TPM exists. Unfortunately adoption is low with the Linux crowd because they still believe the misinformation from 20 years ago.

SoftTalker 102 days ago | |

For SATA SSDs i've used the hdparm secure erase and then verified that dd | hexdump is all zeros. That was good enough for me.

aidenn0 102 days ago | | |

Depending on your threat model, your check is insufficient, since dd |hexdump will be all zeros even if you just trim all the blocks for a drive that is trim-to-zero.

Securely erasing flash drives with a threat model of "someone will dump the raw data of the chips" is only fully solvable for self-encrypting drives where you can replace the key. Even if you can issue a block-erase for every single block of the device, block erase doesn't always succeed on NAND.

Joel_Mckay 102 days ago | | |

For Sata HDD shingled writes and SSD sector replacement it can't be cleaned that way.

Tools like dban stopped working once firmware sector re-mapping chips on modern storage became common. If you see the reported spare replacement count drop on your older s.m.a.r.t reports, than partial sectors may no longer be accessed from the OS without vendor specific forensic software. =3

https://sourceforge.net/projects/dban/

yearolinuxdsktp 102 days ago | |

100%. If you’re not encrypting your drive, along with a strong password, you’re fucking around.

Physical destruction as the only sure way? When your hardware is stolen, good luck physically destroying it.

yrro 102 days ago |

> So I connected it to the computer with the USB to NVME M.2 converter

> blkdiscard: /dev/nvme0n1: BLKSECDISCARD ioctl failed: Operation not supported

I've got a USB-to-NVME adapter that exposes the NVME namespaces as SCSI disks. `blkdiscard` did not work with these by default, however it worked fine after I changed the `provisioning_mode` attribute of the disk.

This can be done by identifying the SCSI device ID of the disk (lsscsi) and then changing it with:

    # echo unmap > /sys/class/scsi_disk/a:b:c:d/provisioning_mode

`lsblk -D` will show which block devices support the discard operation; run it before and after changing provisioning_mode to see the difference.

This is absolutely not to be used as an alternative to a real 'sanitize' operation directly sent to the NVME controller. If you actually need to securely erase your data, and the drive dosesn't support the sanitize operation, then you should physically shred the drive and demand a refund from the retailed (goods as sold are not fit for purpose).

Overall, I've found dealing with nvme a frustrating experience. In theory it's nice to have NVME controller firmware be responsible for executing commands from the host (sanitize! change LBA size! underprovision by 30%!) but in practice, it's complete hit or miss whether controllers support a command or will reject it, or maybe they claim to support it but it doesn't work because the controller firmware is buggy shit.

I would like to have raw NAND devices and have the kernel be in charge of everything, but sadly that wouldn't work for Windows so we're stuck in proprietary firmware hell.

SoftTalker 102 days ago |

Smash it with a hammer and move on. I'd never buy a used storage device anyway, no telling what malware it might contain.

yearolinuxdsktp 102 days ago | |

Do you mean malware in the firmware that sticks around after you format the drive?

wtallis 102 days ago |

It's very common for both NVMe and SATA drives that they'll be locked/frozen during boot and thus will not honor a secure erase command until the drive has been power-cycled, which can usually be accomplished with the system-level sleep/wake cycle. I'm not sure what useful purpose this is meant to serve other than possibly making it hard for malware to instantly and irretrievably wipe your storage.

IAmLiterallyAB 102 days ago |

To maximize device performance when wiping a drive to use for something else, I use nvme format with --ses=1.

Which in theory should free all of the blocks on the flash.

Really hard to find good documentation on this stuff. Doesn't help that 95% of internet articles just say "overwrite with zeroes" which is useless advice

yrro 102 days ago | |

What's the difference between this and sanitize? Should we be doing both?

[edit] sanitize runs on the controller level while format works on the namespace level. So I suppose formatting won't touch any pages not allocated to a namespace.

I wish there was _any_ way to find out which NVME controllers supported which operation before you buy them!

jeffbee 102 days ago | |

Anything that works at the logical block interface will not usefully wipe the device. SES 1 will physically hit every erase block on the device with 20V to blow it away. This happens suspiciously quickly (< 60 seconds typically) but that's just because flash is great.

wolvoleo 102 days ago | | |

Doesn't that harm the flash? The OP seems to use this before using it again but such a high voltage seems rather destructive

tokyobreakfast 102 days ago |

None of these methods are reliable nor should they be trusted.

Every organization with good security hygiene requires physical destruction of SSDs. Full stop, end of negotiation, into the shredder it goes.

Not that it matters much, with the prices of SSDs skyrocketing people are moving back to mechanical disks.

yearolinuxdsktp 102 days ago | |

Every organization with good security hygiene requires strong-password-protected disk encryption, because when your stuff is stolen from your Tesla at lunch time in broad daylight, no shredder policy will save you, full stop.

tokyobreakfast 102 days ago | | |

Who said the data wasn't encrypted?

IAmLiterallyAB 102 days ago |

As far as I know, there is NO way to securely erase a USB flash drive (barring some undocumented vendor specific commands that may exist).

jeffbee 102 days ago | |

This is broadly true of cheap thumb drives, but not true of all USB flash drives. The larger ones generally do support secure erase. E.g. the Crucial X6. I don't know if these use secret vendor commands, or if they use the standard SCSI "sanitize" command.

rationalist 102 days ago | |

Overwrite every single bit with innocuous files?

IAmLiterallyAB 102 days ago | | |

That doesn't work on any* NAND flash device, be it a flash drive, NVME, SATA, whatever.

The block device you see is an abstraction provided by the SSD controller. In reality, the flash capacity is larger. Pages are swapped out for wear leveling. If a block goes bad, it'll be taken out of commission, and your data may hide in there.

All of this happens on the SSD controller. The kernel doesn't know. You have no way to directly erase or modify specific blocks.

*Okay, there are raw NAND flash chips without controllers, but that is not you're working with when you have a SSD or flash drive. If you do have a raw flash chip, you can more directly control flash contents.

Gigachad 102 days ago | | |

This is what `shred` and other secure wipes do. There is some concern over data stored in sections which the firmware has swapped out and made inaccessible. But if this is a concern to you, then you should be using full disk encryption anyway which makes all of this a non issue.

NegativeK 102 days ago |

I had a drawn out conversation with a friend about erasing NVME drives in a way that met compliance needs. The procedure they were given was to install Windows, with Bitlocker, twice with no effort to retain the key.

But that doesn't even overwrite the visible drive space; you can do a simple PoC to demonstrate that Windows won't get to all the mapped blocks. And that still hasn't gotten to the overprovisioned blocks and wear leveling issues that the article references.

You could use the BIOS or whatever CLI tool to tell the drive to chuck its encryption key, but are you sure that tool meets whatever compliance requirements you're beholden to? Are you sure the drive firmware does?

So they went with paying a company to shred the drives. All of them. It's disgustingly wasteful.

protocolture 102 days ago | |

Used to do recycling. Before secure erase was widespread there used to be cheapish 16 and 32GB SSDs for embedded devices, but a few of them made it into the thin/zero client space and a few white labelled low end pc's. they were actually twice the size. Basically 2 16s in a single 16 chassis. And what you would get is that the 2 drives were sort of in sync, I think it was a failover mechanism to deal with shitty drive quality. If drive A failed it would just connect to drive B instead and the user might not know about the failure. But the second drive would not wipe necessarily depending on how you wiped the first one. A few people retrieved data from the second disk under lab conditions, after wiping the first, so we had a report come through that we couldnt certify these disks as erased until they demonstrated compliance with secure erase. So we shredded probably a few thousand of them.

I heard of similar issues with early nvme drives.

wtallis 102 days ago | |

If compliance is the goal, just use FIPS certified self-encrypting drives and trust them to wipe their encryption keys when instructed to do so. At that point, any failure is clearly the vendor's fault, not your own.

NegativeK 101 days ago | | |

That 100% sounds like the right thing to do that can't be done due to budget constraints. The shredding company (who accepts the liability, I think) is just too cheap in comparison.

Neywiny 102 days ago |

Gotta love breaking EFI changes. I don't know how many times my work laptop would do that and I couldn't boot anymore, only to remember some stressful time later that Linux would only boot with some of the settings flipped from their defaults. At least I never had to reinstall anything.

e40 106 days ago |

That was way longer than I expected. Wow.

russfink 102 days ago |

sedutil-cli —yesIwantToEraseALLmydata $PSID /dev/sda1 or something like that.

theandrewbailey 102 days ago | |

Tip: Get a barcode scanner. The PSID is usually encoded in a bar/matrix code on the drive's label, next to the plaintext PSID.

Luker88 102 days ago |

best practice is always to encrypt with luks, and then just shred the header before selling.

blkdiscard is just a TRIM command, the data remains there.

A few years ago (2020?) I also learned that ssd firmware can be buggy when I bricked multiple really expensive enterprise ssd (samsung?)....by running trim. lol.

dist-epoch 102 days ago | |

But how do you shred the header? The drive could have written the new shredded one to a new physical location (wear-leveling).

unnouinceput 102 days ago |

WTF is wrong with just copy/paste the same big unimportant file (like a movie) until you run out of space and then just delete them all? So much unnecessary hurdle with different utilities and commands that made my head spin. What do you think those utilities do in the background anyway if not filling the free space with junk, just like what a copy/paste does?

yrro 102 days ago | |

That won't overwrite pages not allocated to a namespace (which can happen due to wear levelling/underprovisioning, or because the controller has decided to stop using that page because it's unhealthy).

Flash looks like a simple array of blocks, but under the hood there is a controller that allocates writes to different pages. You need to tell the controller to erase all pages if you want to guarantee data destruction.

M95D 101 days ago |

I never used ATA Security commands with NVME or SSDs, but I did use them with spinning rust ATA and SATA drives. I even had a BIOS module added into the firmware of the motherboard to manage ATA Security [0].

I have a few comments to make:

Erase operation is in fact a succession of two commands: ATA Security Erase Pepare and ATA Security Erase Execute. No other command can be sent between these two, so any disk access by the OS after the first command would cause the second to fail.

ATA Security commands are usually blocked ("frozen") after boot if the drive has no password or was password-unlocked. That means the drive will not accept commands to set/change password or erase until power-cycled. That is a full power cut, not just a reset-drive command.

This feature prevents a virus from passwording or erasing your drive. Yes, it can still crypto-lock or erase your drive via ordinary disk writes, but that takes hours for the whole drive, while ATA Security Erase or setting a password takes a millisecond or so.

The ATA Security Freeze command is sent to the drive either by the BIOS/UEFI (my BIOS didn't do this, but probably all laptops have it as part of their BIOS/UEFI Security features), by a BIOS module (my desktop BIOS didn't have it), by the operating system as part of drive encryption features, or by an antivirus. Also, the drive firmware may have a timer to automatically freeze ATA Security commands after a timeout if it doesn't receive the explicit command from the host.

Power cycling by putting the system to sleep and then wake up will NOT work, because if the drive is locked with a password, it needs to be unlocked BEFORE the firmware/ACPI gives control back to the operating system. Otherwise, the OS would no longer be able to access the disk after wake up. So, the BIOS/UEFI/ACPI, if it supports ATA Security at all, will automatically freeze ATA Security commands again during wake-up, just as it did during cold boot.

In conclusion, the dive must be physically unplugged from power and then hot-plugged. Or start the computer without it, and hot-plug it after boot.

Many (most?) USB adapters don't support ATA commands at all. They'll just emulate a USB mass storage with no direct access to the drive. What you need is an adapter that supports UAS (USB Attached SCSI). And even then, I'm not sure ATA Security commands have a SCSI equivalent so they can be translated.

The best option here is to hot-plug into a real SATA port on the motherboard or PCI/PCIe controller. NOT via USB.

[0] https://www.fitzenreiter.de/ata/ata_eng.htm

buckle8017 102 days ago |

Smash it with a hammer.

If you insist on erasing the data, overwrite the entire contents of the drive twice with random data.

Doing it twice will blow away any cached as well (probably).