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degob

degob is a reversing tool for gobs. If you have the binary form of a gob, but you don't have to struct to decode it into, this library still allows you to get a more readable representation of the data.

cmds/degob

The easiest way to use all of this is to just build the binary in cmds/degob and send gobs to it either through stdin or from files and then get the output to stdout or to a file. See its README for more info.

Setting environmental variable DEGOB_NORAND=1 will stop the anonymous structs from having that hex suffix. The number stays because that is the type ID defined in the gob. DEGOB_SEED sets a specific seed value.

Usage

Create a new Decoder over your reader using NewDecoder and then decode that into a slice of Gobs with Decode or stream Gobs with DecodeStream. DecodeStream seems fairly stable, but it was difficult to test how it handles all error cases, so be wary of errors. Once you have Gobs you can either play with the types directly or just print them out to a writer using the WriteTypes and WriteValues methods.

The output from the Write methods on Gob should be close to valid Go source.

The provided degob command provides a straightforward sample usage.

Limitations

There are a few limitations that I can't really get around.

  • gobs don't include information about the bit size of the type so all types are their largest possible (int64, uint64, complex128, float64) so as to be able to accept anything. This means that the representations you get aren't exactly the representations that the source was using with respect to bitsizes.
  • bytes are received as uint64, but []byte is correct. There is no type id for a single byte in the gob format.
  • There is no way to differentiate between a type and a pointer to that type.
  • There is an included JSON output format, but, since a gob can be any valid Go type, there are plenty of valid gobs that cannot be accurately represented as JSON. Simple types will not print valid JSON. Bad map types will return an error JSON that contains the SingleLine format of the map under val.
  • GobEncoder, TextEncoder, and BinaryMarshaler are all displayed as []byte since the format is opaque without the actual type definition.

TODO

  • Printing stylized output
  • Some more testing (I'm around ~80%)
  • Include more "bad gob" tests, but to be honest this tool shouldn't be seeing very many bad gobs. It isn't really meant to be doing much validating, so this is pretty low priority, and part of the reason I'm OK with some of the panics and lack of testing around bad gobs.