Seed math/rand with crypto/rand #359
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rolandshoemaker
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Nice! Don't like the panic though as that is a backwards incomp. change. Can't we just default to the current setup then? I.e. seed with 1? |
rolandshoemaker
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Good point, I've also cleaned up the various integer bounding by leaving it to the compiler (it's much cleverer than me anyway). |
| if err != nil { | ||
| // Failed to read from cryptographic source, warn user and | ||
| // fallback to default initial seed (1) by returning early | ||
| log.Printf("Failed to seed math/rand with crypto/rand.Read for message ID generation: %s\n", err) |
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prolly nobody ever will read this and the random is no worse then now, so I would just drop the log - leave the comment though!
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The performance arguments given in #48 and #102 are perfectly valid reasons to not use
crypto/randfor every message ID but that doesn't mean you have to use the default seed (which is literally just1) when usingmath/rand.This patch simply reads out a random
int64usingcrypto/randon package initialization and uses it to seed the defaultmath/randsource. While there are obviously other more viable attacks this should make message ID spoofing/prediction much harder when using the defaultId.This also changes
id()to just use a randint32and bound it to the max size of auint16instead of usingtime.Nowsince it's a relatively easy to guess variable so it shouldn't actually provide that many useful bits (since someone analyzing the messages will generally know the period the messages were generated in).