strange wasm

[Alessio Mochi]

I download from the browser an a file .wasm of an web application where inside

is present a unique string like:

YAJ/fwF/YAF/AX5gBX9/f39/AGAAAGADf39/AGAHf39/f39/fwBgBH9/f38Bf2AAAX9gAX8Bf2AEf39/fwBgBn9/f39/fwF/YAd/f39/f39/AX9gAAACVQIHLi9pbmRleCJfX3diZ19sb2FkUmVzdWx0c19hNzlhNDg1ODc0MmIxNDkyAAUHLi9pbmRleBxfX3diZ19lcnJvcl...

that is very strange. I usually see some code in file wasm. 

Is it possible for the code to be decrypted and executed on the fly in the browser?

[Floh]

Despite the name, WASM files are binary data. If you want to see the disassembly, either look at the WASM files in browser devtools under the "Sources" tab, or use the wasm2wat tool from the WABT toolkit: https://github.com/WebAssembly/wabt

[Alessio Mochi]

I was not referring to the name of the file but to its content.

I tried to run the command on the file but it says it's invalid

$ wasm2wat file.module.wasm
0000004: error: bad magic value

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[Jorge Prendes]

If that's the begining of the file, then it's not a valid wasm file.

I any case, that seems to be base64 encoded, decoding to:

` ` ~` `` ` ` ` ` ` ` ` ` U ./index"__wbg_loadResults_a79a4858742b1492 ./index __wbg_error

This is not a valid wasm file start either, but might help you move forward.

Answering your question, it's entirely possible for the application to manipulate the bytes before attempting to execute it as a wasm binary.

Cheers,

Jorge

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[Alessio Mochi]

Hello Jorge,

the file content begin with:

AGFzbQEAAAABZxBgAn9/AGABfwBgA39/fwF/YAJ/fwF/YAF/AX5gBX9/f39/AGAAAGADf39/AGAHf39/f39/fwBgBH9/f38Bf2AAAX9gAX8Bf2AEf39/fwBgBn9/f39

can you explain how this process of decoding and executing the wasm file can be done on the browser?

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