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   Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 21:24:22 JST Wolf480pl

   Imagine SD card but the FORCE ERASE command also resets PERM_WRITE_PROTECT

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     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 21:24:19 JST Wolf480pl

     in reply to

     or I could just buy a bunch of those cards and use the permanent write-protect....

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     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Saturday, 04-Jan-2025 21:24:19 JST 翠星石

     in reply to
     @wolf480pl >resets PERM_WRITE_PROTECT
     That's implemented by the reader, not the card, so you can just ignore than flag.
     
     >the ability to write-protect it in such a way, that un-write-protecting requires a password.
     SD cards contain a microprocessor running proprietary software, thus an attacker can really just reprogram the SD card and ask it to dump out all blocks.
     
     You could write free software for a SD card that implements such functionality, but an attacker could still reprogram it.
     
     
     You're better of encrypting the cards with LUKS2, as that would mean that any attacker that doesn't know the password isn't able to make specific edits to files (there are still some attacks against AES-XTS where you can overwrite a block and LUKS can't tell, although there is a optional journaling feature that can detect such modifications).
   • Embed this notice
     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 21:24:20 JST Wolf480pl

     in reply to

     Imagine SD card but with the ability to write-protect it in such a way, that un-write-protecting requires a password.

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     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 21:24:21 JST Wolf480pl

     in reply to

     Wait no, that's useless, since a rogue host can read the whole card before erasing it, and then write modified content back.

     Damn.

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     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 21:53:06 JST Wolf480pl

     in reply to

     • 翠星石

     @Suiseiseki
     > an attacker can [...] dump out all blocks.

     not a concnern

     > You're better of encrypting the cards with LUKS2

     that misses the point.

     I need an untrusted computer to be able to read the content of the card, without being able to modify it.

     Also, can you stop being patronizing?
     Not everyone has the same threat model as you, not everyone is trying to solve the same problem as you, and if LUKS was the answer I would've figured that out myself.

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     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Saturday, 04-Jan-2025 21:53:06 JST 翠星石

     in reply to
     @wolf480pl >Citation needed.
     It came to me in a dream.
     
     >I need an untrusted computer to be able to read the content of the card, without being able to modify it.
     You need a storage medium that is physically impossible to modify.
     
     I suggest a filled up DVD-R (can be plugged in via a USB DVD reader).
     
     >Not everyone has the same threat model as you
     Everyone deserves freedom, no matter who they are.
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     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 21:53:07 JST Wolf480pl

     in reply to

     • 翠星石

     @Suiseiseki
     > [PERM_WRITE_PROTECT] is implemented by the reader, not the card, so you can just ignore than flag.

     Citation needed.

     The SD spec says the physical write-protect switch on the side of the card is only implemented by the reader, but that's a separate thing from the PERM_WRITE_PROTECT bit in the CSD register.

     1/

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     Taylan (Now 18% More Deranged) (taylan@fedi.feministwiki.org)'s status on Saturday, 04-Jan-2025 21:57:33 JST Taylan (Now 18% More Deranged)

     in reply to
     @wolf480pl
     
     Out of curiosity, what's the exact use case that leads to this requirement? Sounds interesting.
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     Taylan (Now 18% More Deranged) (taylan@fedi.feministwiki.org)'s status on Saturday, 04-Jan-2025 21:58:42 JST Taylan (Now 18% More Deranged)

     in reply to

     • Taylan (Now 18% More Deranged)
     @wolf480pl oh you just posted it in response to someone else :blobcat-thumbsup:
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     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 22:05:57 JST Wolf480pl

     in reply to

     • 翠星石

     @Suiseiseki did you know that USB DVD readers have microcontrollers in them, running proprietary software?

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     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Saturday, 04-Jan-2025 22:05:57 JST 翠星石

     in reply to
     @wolf480pl Yes, but they cannot write to a DVD-R due to how they lack a burning laser and also how you can't really write to a fully-written DVD-R.
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     翠星石 (suiseiseki@freesoftwareextremist.com)'s status on Saturday, 04-Jan-2025 22:15:25 JST 翠星石

     in reply to
     @wolf480pl Sure, but there is extremely limited amounts of storage available, thus any of such attacks would be very limited.
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     Wolf480pl (wolf480pl@mstdn.io)'s status on Saturday, 04-Jan-2025 22:15:26 JST Wolf480pl

     in reply to

     • 翠星石

     @Suiseiseki but the attacker can reprogram the drive to return bytes different than the ones actually on the disc