5 ms·

I don't need self-destructing USB drive, but a USB flash stick with a hard write-protect switch (that can't be overridden by the USB host) would be great for pu

by neilv 3y ago

I don't need self-destructing USB drive, but a USB flash stick with a hard write-protect switch (that can't be overridden by the USB host) would be great for purposes like immutable installation and boot media. (Also, like any USB device should, but even more here, you have to ensure that the device controller can't be modified by the USB host.)

oconnore 3y ago
That would be very useful. We sadly stopped innovating on optical media, but haven't really made the alternatives usable as a replacement. You used to have CDs / DVDs that were: 1. Completely immutable 2. Could not be maliciously altered by the reader 3. Could not masquerade as a keyboard or a mouse
- ace2358 3y ago
  I miss physical media, optical or magnetic. Or something new!! Flash drivers are just computers these days.
  - simbolit 3y ago
    In what sense is a nand chip, a memory controller, and a usb plug, a "computer these days"?
    - toast0 3y ago
      The flash memory controller is most likely a embedded stored program computer. Likely an arm, maybe dual core. A modern computer is really a distributed system, but not a lot of people frame the discussion that way.
    - yencabulator 3y ago
      https://www.bunniestudios.com/blog/?page_id=3592 https://www.bunniestudios.com/blog/?page_id=3592 > The embedded microcontroller is typically a heavily modified 8051 or ARM CPU. In modern implementations, the microcontroller will approach 100 MHz performance levels, and also have several hardware accelerators on-die.
- Syonyk 3y ago
  You still do. I can't be the only person who burns install DVDs, finalized, verifies the hash on a few different systems, and then keeps them in a safe place for possible future use... I've got some external USB readers/burners that excel for exactly this sort of thing, and just about anything that will run a modern OS will boot from them.
  - JohnFen 3y ago
    You're not the only one. I still do this, and use CDs/DVDs for all sorts of other longer-term storage as well. I'm unaware of any other media that works well for those sorts of use cases.
    - superb_dev 3y ago
      What is the shelf life of a modern CD/DVD? I might consider using them more
      - JohnFen 3y ago
        At room temperature, about 25 years -- but there are a lot of variables that can affect this in both directions. https://www.clir.org/pubs/reports/pub121/sec4/ https://www.clir.org/pubs/reports/pub121/sec4/
        dml2135 3y ago
        Maybe for commercial-grade optical media, but last time I burned a lot of consumer media , I found a decent amount of failures even just a few years out. Admittedly this was almost 20 years ago at this point so maybe some things have improved since then but my understanding is that consumer media uses a different, ink-based technology to write data to disk, and that ink can degrade pretty quickly. This is in contrast to commercial optical media in which the data is stamped into the disk in a manner more akin to a vinyl record.
        JohnFen 3y ago
- mike_hock 3y ago
  > Completely immutable Wouldn't the laser of a CD/DVD writer be powerful enough to alter the data after the fact? Not to overwrite it with completely arbitrary data, but flipping a few well-chosen bits should in principle be able to create a backdoor that wasn't there before (if it's a live or install disk, for example).
  - JohnFen 3y ago
    You can change things, yes, but not in a way that keeps the disc usable. The issue here is that you can't "unburn" a bit that has been burned. Since you burn 0s, not 1s, all you can do is make more bits 0 -- which would then be corrected by the error correction mechanism. You could alter the EC codes, but that would render them useless and eliminate the ability to correct errors, causing the data to be unreadable by a normal drive due to EC failure. So, in practice, they're pretty safe. The worst thing that an attacker could do is to render the media unusable.
    - calamari4065 3y ago
      That's not completely true either. I used to use some sketchy utility back in the day that could mark one recording session as inaccessible and let you add data to any remaining space on the disc. You would only see the new session. Hypothetically you can also manipulate the file table to make it look exactly like the real thing. I don't remember if it required the disc to be un-finalized or not. It probably did. But this is really an edge case
      - JohnFen 3y ago
        True, I was assuming the disc wasn't written as a multi-session one (most people never use multi-session). Multi-session discs are a bit different. But, afaik, if the disc has been finalized then the result is as "immutable" as a non-multisession one. I'm not completely certain about that, though.
    - mike_hock 3y ago
      Are the EC codes such that any alteration from 1 to 0 in the message results in at least one flip from 0 to 1 in the (correct) EC code? If not, then you "just" have to find the right spots where such a simultaneous alteration of the payload and the EC code is possible, and which also happens to result in a desirable behavior change.
1970-01-01 3y ago
Have it, love it: https://www.kanguru.com/products/kanguru-flashblu30-usb3-flash-drive https://www.kanguru.com/products/kanguru-flashblu30-usb3-fla...
- neilv 3y ago
  Cool. Any idea how well-secured that one is, for use with USB hosts that potentially have adversary tech active on them? (Threats to modify data on the drive or the code of its controller; not concerned with threats that fry the device with power.)
  - 1970-01-01 3y ago
    It will work just fine for this. You can superglue the switch if you need to keep it read only.
    - Luc 3y ago
      But is the switch just an input that is read by the software on the device, or does it actually interrupt e.g. a data line, making it impossible for even hacked software on the USB device to write to memory? I can't really find a conclusive answer.
      - 1970-01-01 3y ago
        It physically switches some circuit to disable the ability for data to be written onto the device. Why not contact them and get the details?
        Luc 3y ago
        I was just attempting to restate neilv's question in a different way. If you don't know that's fine.
        neilv 3y ago
sowbug 3y ago
Not exactly what you describe, but for the installation and boot use cases you're describing, have you tried Ventoy? It's still all software, but it's an extra layer of protection against the disk images being modified.
- mike_hock 3y ago
  It's exactly zero protection against anything being modified, including the chainloader itself.
deleted 3y ago
[deleted]
wolpoli 3y ago
SD Cards do have a write protect switch. Does anyone know if that's enforced on the card itself?
- anonymousiam 3y ago
  It's not enforced by the card. It's just a plastic tab that slides so as to tell the reader that the card should not be written. There is nothing to stop a malicious reader from writing to a write-protected card.
  - IAmLiterallyAB 3y ago
    Wow really? That's annoying. Why go to all the trouble to add the switch if they won't implement it correctly
    - AussieWog93 3y ago
      Because engineering consumer media to be robust to a Stuxnet-level attack vector is ridiculous? The switch as-is prevents the file system from becoming corrupt when you don't "safely remove" the device, and that's plenty enough for the average photographer.
    - JohnFen 3y ago
      I think the purpose of the switch is the same as the write-protect notches on old floppy disks: it's not really a security measure, it's meant to prevent the owner from accidentally formatting/erasing/overwriting things.
      - userbinator 3y ago
        Or to go even further, the write-protect tabs on cassette tapes.
  - calamari4065 3y ago
    No, it is electrically connected, but only to the connector. That's why one of the edge contacts is split in two. It's still up to the host to enforce.
kevin_thibedeau 3y ago
Use an SD card adapter.
RalfWausE 3y ago
"Why not simply" use an USB DVD / Blueray drive? I mean... more security / write protection is not possible as far as i know...
ravenstine 3y ago
I would even want that for a non-stick full size USB drive like one of those Sandisk 2 TB drives. I know that an FS can be made read-only, but it would be great if it were possible to protect from writes at the hardware level without making it too easy for someone (could be a family member or whomever) to turn off the protection.
sonicanatidae 3y ago
I have 2 of them. An ancient 2 GB Sandisk and more recent and available Kanguru SS3 with Write Protect. Great little tool.

by neilv 3y ago

oconnore 3y ago

That would be very useful. We sadly stopped innovating on optical media, but haven't really made the alternatives usable as a replacement. You used to have CDs / DVDs that were: 1. Completely immutable 2. Could not be maliciously altered by the reader 3. Could not masquerade as a keyboard or a mouse

ace2358 3y ago
I miss physical media, optical or magnetic. Or something new!! Flash drivers are just computers these days.
- simbolit 3y ago
  In what sense is a nand chip, a memory controller, and a usb plug, a "computer these days"?
  - toast0 3y ago
    The flash memory controller is most likely a embedded stored program computer. Likely an arm, maybe dual core. A modern computer is really a distributed system, but not a lot of people frame the discussion that way.
  - yencabulator 3y ago
    https://www.bunniestudios.com/blog/?page_id=3592 https://www.bunniestudios.com/blog/?page_id=3592 > The embedded microcontroller is typically a heavily modified 8051 or ARM CPU. In modern implementations, the microcontroller will approach 100 MHz performance levels, and also have several hardware accelerators on-die.
Syonyk 3y ago
You still do. I can't be the only person who burns install DVDs, finalized, verifies the hash on a few different systems, and then keeps them in a safe place for possible future use... I've got some external USB readers/burners that excel for exactly this sort of thing, and just about anything that will run a modern OS will boot from them.
- JohnFen 3y ago
  You're not the only one. I still do this, and use CDs/DVDs for all sorts of other longer-term storage as well. I'm unaware of any other media that works well for those sorts of use cases.
  - superb_dev 3y ago
    What is the shelf life of a modern CD/DVD? I might consider using them more
    - JohnFen 3y ago
      At room temperature, about 25 years -- but there are a lot of variables that can affect this in both directions. https://www.clir.org/pubs/reports/pub121/sec4/ https://www.clir.org/pubs/reports/pub121/sec4/
      - dml2135 3y ago
        Maybe for commercial-grade optical media, but last time I burned a lot of consumer media , I found a decent amount of failures even just a few years out. Admittedly this was almost 20 years ago at this point so maybe some things have improved since then but my understanding is that consumer media uses a different, ink-based technology to write data to disk, and that ink can degrade pretty quickly. This is in contrast to commercial optical media in which the data is stamped into the disk in a manner more akin to a vinyl record.
        JohnFen 3y ago
mike_hock 3y ago
> Completely immutable Wouldn't the laser of a CD/DVD writer be powerful enough to alter the data after the fact? Not to overwrite it with completely arbitrary data, but flipping a few well-chosen bits should in principle be able to create a backdoor that wasn't there before (if it's a live or install disk, for example).
- JohnFen 3y ago
  You can change things, yes, but not in a way that keeps the disc usable. The issue here is that you can't "unburn" a bit that has been burned. Since you burn 0s, not 1s, all you can do is make more bits 0 -- which would then be corrected by the error correction mechanism. You could alter the EC codes, but that would render them useless and eliminate the ability to correct errors, causing the data to be unreadable by a normal drive due to EC failure. So, in practice, they're pretty safe. The worst thing that an attacker could do is to render the media unusable.
  - calamari4065 3y ago
    That's not completely true either. I used to use some sketchy utility back in the day that could mark one recording session as inaccessible and let you add data to any remaining space on the disc. You would only see the new session. Hypothetically you can also manipulate the file table to make it look exactly like the real thing. I don't remember if it required the disc to be un-finalized or not. It probably did. But this is really an edge case
    - JohnFen 3y ago
      True, I was assuming the disc wasn't written as a multi-session one (most people never use multi-session). Multi-session discs are a bit different. But, afaik, if the disc has been finalized then the result is as "immutable" as a non-multisession one. I'm not completely certain about that, though.
  - mike_hock 3y ago
    Are the EC codes such that any alteration from 1 to 0 in the message results in at least one flip from 0 to 1 in the (correct) EC code? If not, then you "just" have to find the right spots where such a simultaneous alteration of the payload and the EC code is possible, and which also happens to result in a desirable behavior change.

1970-01-01 3y ago

Have it, love it: https://www.kanguru.com/products/kanguru-flashblu30-usb3-flash-drive https://www.kanguru.com/products/kanguru-flashblu30-usb3-fla...

neilv 3y ago
Cool. Any idea how well-secured that one is, for use with USB hosts that potentially have adversary tech active on them? (Threats to modify data on the drive or the code of its controller; not concerned with threats that fry the device with power.)
- 1970-01-01 3y ago
  It will work just fine for this. You can superglue the switch if you need to keep it read only.
  - Luc 3y ago
    But is the switch just an input that is read by the software on the device, or does it actually interrupt e.g. a data line, making it impossible for even hacked software on the USB device to write to memory? I can't really find a conclusive answer.
    - 1970-01-01 3y ago
      It physically switches some circuit to disable the ability for data to be written onto the device. Why not contact them and get the details?
      - Luc 3y ago
        I was just attempting to restate neilv's question in a different way. If you don't know that's fine.
        neilv 3y ago

sowbug 3y ago

Not exactly what you describe, but for the installation and boot use cases you're describing, have you tried Ventoy? It's still all software, but it's an extra layer of protection against the disk images being modified.

mike_hock 3y ago
It's exactly zero protection against anything being modified, including the chainloader itself.

deleted 3y ago

[deleted]

wolpoli 3y ago

SD Cards do have a write protect switch. Does anyone know if that's enforced on the card itself?

anonymousiam 3y ago
It's not enforced by the card. It's just a plastic tab that slides so as to tell the reader that the card should not be written. There is nothing to stop a malicious reader from writing to a write-protected card.
- IAmLiterallyAB 3y ago
  Wow really? That's annoying. Why go to all the trouble to add the switch if they won't implement it correctly
  - AussieWog93 3y ago
    Because engineering consumer media to be robust to a Stuxnet-level attack vector is ridiculous? The switch as-is prevents the file system from becoming corrupt when you don't "safely remove" the device, and that's plenty enough for the average photographer.
  - JohnFen 3y ago
    I think the purpose of the switch is the same as the write-protect notches on old floppy disks: it's not really a security measure, it's meant to prevent the owner from accidentally formatting/erasing/overwriting things.
    - userbinator 3y ago
      Or to go even further, the write-protect tabs on cassette tapes.
- calamari4065 3y ago
  No, it is electrically connected, but only to the connector. That's why one of the edge contacts is split in two. It's still up to the host to enforce.

kevin_thibedeau 3y ago

Use an SD card adapter.

RalfWausE 3y ago

"Why not simply" use an USB DVD / Blueray drive? I mean... more security / write protection is not possible as far as i know...

ravenstine 3y ago

I would even want that for a non-stick full size USB drive like one of those Sandisk 2 TB drives. I know that an FS can be made read-only, but it would be great if it were possible to protect from writes at the hardware level without making it too easy for someone (could be a family member or whomever) to turn off the protection.

sonicanatidae 3y ago

I have 2 of them. An ancient 2 GB Sandisk and more recent and available Kanguru SS3 with Write Protect. Great little tool.