Set a maximum packet size of 32768 bytes for version and cleartext packets #49
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…ckets - including those wrapping encrypted packets
Yes, I think so.
2^17 seems reasonable. |
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@Lukasa how do you suggest passing the customisability down to the parser? |
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Ideally the keys should know how to parse their own wire format, so that part isn’t too rough. The bigger issue is ensuring that we can dispatch to the right key type. We’ll likely need a place that users can register custom keys such that they can register their key identifiers. The bigger wrinkle is that some keys will trigger completely different user authentication flows. That needs some more consideration: we may need to allow users to plug in entirely separate user auth state machines, which is gonna be a bit of a tricky ask. |
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@Lukasa I forgot about this branch, but just checked up on Swift-NIO-SSH in general and noticed them open. Can we merge this without customisability? And if not, how do we plan to tackle that? |
Lukasa
requested changes
Nov 11, 2021
Sources/NIOSSH/SSHPacketParser.swift
Outdated
| // Prevent the consumed bytes for a version from exceeding the maximum packet size | ||
| // In practice, if SSH version packets come anywhere near this it's already likely an attack | ||
| // More data cannot be blindly regarded as malicious though, since these might be multiple packets | ||
| let maximumVersionSize = min(slice.endIndex, self.maximumPacketSize) |
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ByteBufferView is not necessarily zero-indexed, so self.maximumPacketSize has to be translated into index-space first. I think this should be let maxIndex = slice.index(slice.startIndex, offsetBy: min(slice.count, self.maximumPacketSize)).
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@Lukasa while allowing users to configure the maximum packet size, shouldn't we still manually restrict the version size? |
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Yup, I think so. |
Lukasa
reviewed
Nov 23, 2021
added 2 commits
November 23, 2021 17:36
# Conflicts: # Tests/NIOSSHTests/EndToEndTests.swift
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@Lukasa any idea what's failing? I can't see the build output |
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I think the packet size should be a bit larger than the minimum requirement of 2^15 specified by SSH's RFC. I'd like to add some tests to this, and admittedly didn't test this at all. Before continuing I want to discuss a few questions first: