Inconsistencies with cryptoPwhashStr across libraries

[vishnukvmd]

When I call cryptoPwhashStr, the resulting output seems to always be of length 128 and is returned padded with \u000s.

I don't see this behavior documented. All I can find is:

out must be large enough to hold crypto_pwhash_STRBYTES bytes, but the actual output string may be shorter.

Which makes me wonder if this check is necessary.

This extra padding seems to be breaking counterparts like libsodium.js which rejects calls to crypto_pwhash_str_verify for hashes that are generated from the flutter_sodium library. Everything works fine if I trim out all but the last \u000.

Apologies if I've missed something here. If I haven't, it would be great if we could have consistency across the multiple implementations of libsodium.

Thanks again for everything!

[kozw]

You are right, those padded \u000s shouldn't be there. And the verify function string length check is invalid.

The use of null-terminated strings in Dart does raise some issues, so here's a backwards incompatible design proposal.

• Sodium.cryptoPwhashStr no longer returns a Dart string, but a Uint8List which does include the null terminator if shorter than crypto_pwhash_STRBYTES
• Sodium.cryptoPwhashStrVerify no longer accepts a Dart string, but a Uint8List which must include the null terminator if shorter than crypto_pwhash_STRBYTES

The high-level PasswordHash class will not change and continue to use Dart Strings. Internally it will convert Dart strings to a null terminated Uint8List.

If you want to use the flutter_sodium hashes with other libraries, you should use the core Sodium functions. If you stick with Dart only you can use PasswordHash.

Thoughts?

[vishnukvmd]

Since I'm fairly new to libsodium, I'm not sure if other consumers would have an expectation that the data types of function arguments and the return value should resemble the ones documented.

If not, please go ahead. As someone who prefers unassuming bytes over strings, your proposal sounds great.

[kozw]

Thanks for the feedback. I'm fairly happy with replacing the string return value with bytes, this is fine for the low level Sodium functions.

flutter_sodium 0.1.8 is now available with the changes

[vishnukvmd]

Works flawlessly, thank you!