ssh-key: support for undersized ECDSA/P-521 keys #351
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zaczkows
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Apr 15, 2025
zaczkows
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- fixes Failed to process python's paramiko ecdsa key #350
- I still need to investigate key encoding to ensure code is even remotely correct
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April 15, 2025 13:39
tarcieri
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Apr 15, 2025
ssh-key/src/private/ecdsa.rs
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| if len < SIZE { | ||
| reader.read(&mut bytes[0..len])?; | ||
| } else { | ||
| reader.read(&mut bytes)?; | ||
| } |
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Seems like this could just be:
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| if len < SIZE { | |
| reader.read(&mut bytes[0..len])?; | |
| } else { | |
| reader.read(&mut bytes)?; | |
| } | |
| reader.read(&mut bytes[..len])?; |
...but also it would be good to also check that len <= SIZE? (unless that check is happening elsewhere)
It would also be good to enforce a minimum size.
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This is what I'm trying to check and how much smaller the key can be.
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| // https://stackoverflow.com/questions/50002149/why-p-521-public-key-x-y-some-time-is-65-bytes-some-time-is-66-bytes | ||
| // although lower keys than 64 are vanishingly possible, but lets stop here | ||
| if len > 63 { | ||
| reader.read(&mut bytes[..core::cmp::min(len, SIZE)])?; |
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Hmm, upon further reflection this seems wrong: the key is supposed to be big endian, so the array should contain leading zeros, not trailing zeros, in the event the input document's key is too short.
It would also be good to add a test that the key is decoded correctly.
I'll try to take care of this in #356
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Followup to #351 Also includes a fix and test to ensure that short keys zero-pad MSB rather than LSB, since they're encoded as big endian.
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Followup to #351 Also includes a fix and test to ensure that short keys zero-pad MSB rather than LSB, since they're encoded as big endian.
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Followup to #351 Also includes a fix and test to ensure that short keys zero-pad MSB rather than LSB, since they're encoded as big endian.
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