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lipp / lua-websockets

Websockets for Lua.
http://lipp.github.com/lua-websockets/
MIT License
396 stars 113 forks source link

SHA1 message digest computation on iOS Devices. #31

Closed markbrockington closed 10 years ago

markbrockington commented 10 years ago

We've been encountering issues getting the handshake to work on iOS devices. After a lot of work, we've verified that SHA1 seems to be operating correctly, but the problem is how the pack procedure is configured.

When the variables h0-h4 are passed in to pack as unsigned integers, we see good values being generated on OSX. This includes the iOS Simulator.

Using the latest XCode and running on a device (you can't duplicate this issue using the Simulator), if the variable is > 2^31, it's treated as a negative number and is turned into a zero on iOS.

By converting the pack routine to using signed integers in src/websocket//tools.lua, We changed the final line in the sha1 function

return spack('>I>I>I>I>I',h0,h1,h2,h3,h4)

to the following:

return spack('>i>i>i>i>i',h0,h1,h2,h3,h4)

It does seem counter-intuitive, but using unsigned integers causes lpack to fall into the C++ standard (4.9) of undefined conversion behaviour, and using signed integers gives the desired behaviour in lpack.

lipp commented 10 years ago

thanks a lot for reporting! i'll integrate your patch soon!