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crypto ahash error handling

DISCUSSION Dmitry Kasatkin 2 participants 7 messages Nov 8, 2010 – Nov 12, 2010 Crypto API

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Dmitry Kasatkin

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#0 lore raw

Hello,

When using crypto ahash API, is it necessary/mandatory to call crypto_ahash_final() if crypto_ahash_update() returns error...

Basically it might happen after several calls while calculating hash if HW error happens.
It is not possible to continue hash calculation. it is necessary to reset HW and start whole hash again..

Any comments?

Thanks,
Dmitry

maintainer
#1 lore raw
Quoted 5 lines · Dmitry Kasatkin

Hello,

When using crypto ahash API, is it necessary/mandatory to call crypto_ahash_final() if crypto_ahash_update() returns error...

Quoted 8 lines

Basically it might happen after several calls while calculating hash if HW error happens.
It is not possible to continue hash calculation. it is necessary to reset HW and start whole hash again..

Any comments?

From the driver's perspective you cannot expect that the user

will call crypto_ahash_final in this case, or for that matter in any other case as the user is always free to leave a hash in an unfinalised state.

Cheers,

Signature · 3 lines
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
author
#2 lore raw

This is not good.

Driver might allocate some resources, which needs to be released. crypto_ahash_final() should do some kind of "cleanup" task.

- Dmitry

Quoted 21 lines · ext Herbert Xu
Quoted 5 lines · Dmitry Kasatkin

Hello,

When using crypto ahash API, is it necessary/mandatory to call crypto_ahash_final() if crypto_ahash_update() returns error...

Quoted 7 lines

Basically it might happen after several calls while calculating hash if HW error happens.
It is not possible to continue hash calculation. it is necessary to reset HW and start whole hash again..

Any comments?

From the driver's perspective you cannot expect that the user will call crypto_ahash_final in this case, or for that matter in any other case as the user is always free to leave a hash in an unfinalised state.

Cheers,

maintainer
#3 lore raw
Quoted 4 lines · Dmitry Kasatkin

This is not good.

Driver might allocate some resources, which needs to be released. crypto_ahash_final() should do some kind of "cleanup" task.

Then your driver is broken. The whole hash API is designed around the fact that each update operation completely stores all output state in the memory provided, leaving no state behind in the hardware.

Is your hardware capable of producing unfinalised hashes? If not then you shouldn't even be implementing an update operation in hardware. You should instead use a software fallback.

Cheers,

Signature · 3 lines
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
author
#4 lore raw

Hi,

Yes. Our HW is capable of producing unfinalised hashes. Everything is fine.

No. It is not broken.. It cleans up if error...

- Dmitry

Quoted 18 lines · ext Herbert Xu
Quoted 5 lines · Dmitry Kasatkin

This is not good.

Driver might allocate some resources, which needs to be released. crypto_ahash_final() should do some kind of "cleanup" task.

Then your driver is broken. The whole hash API is designed around the fact that each update operation completely stores all output state in the memory provided, leaving no state behind in the hardware.

Is your hardware capable of producing unfinalised hashes? If not then you shouldn't even be implementing an update operation in hardware. You should instead use a software fallback.

Cheers,

maintainer
#5 lore raw
Quoted 4 lines · Dmitry Kasatkin

Hi,

Yes. Our HW is capable of producing unfinalised hashes. Everything is fine.

OK then you should be fine even if the user never makes the "final" call, right?

Cheers,

Signature · 3 lines
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
author
#6 lore raw

Well.. That was not the case before.
I made a new patch set.

I will send updates for SHA and AES soon after some more testing.

- Dmitry

Quoted 12 lines · ext Herbert Xu
Quoted 5 lines · Dmitry Kasatkin

Hi,

Yes. Our HW is capable of producing unfinalised hashes. Everything is fine.

OK then you should be fine even if the user never makes the "final" call, right?

Cheers,