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40 lines
1.1 KiB
Go
40 lines
1.1 KiB
Go
// Copyright (c) 2018 Shivaram Lingamneni <slingamn@cs.stanford.edu>
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// released under the MIT license
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package utils
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import (
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"crypto/rand"
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"crypto/subtle"
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"encoding/base32"
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)
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var (
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// slingamn's own private b32 alphabet, removing 1, l, o, and 0
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b32encoder = base32.NewEncoding("abcdefghijkmnpqrstuvwxyz23456789").WithPadding(base32.NoPadding)
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)
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const (
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SecretTokenLength = 26
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)
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// generate a secret token that cannot be brute-forced via online attacks
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func GenerateSecretToken() string {
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// 128 bits of entropy are enough to resist any online attack:
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var buf [16]byte
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rand.Read(buf[:])
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// 26 ASCII characters, should be fine for most purposes
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return b32encoder.EncodeToString(buf[:])
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}
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// securely check if a supplied token matches a stored token
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func SecretTokensMatch(storedToken string, suppliedToken string) bool {
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// XXX fix a potential gotcha: if the stored token is uninitialized,
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// then nothing should match it, not even supplying an empty token.
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if len(storedToken) == 0 {
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return false
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}
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return subtle.ConstantTimeCompare([]byte(storedToken), []byte(suppliedToken)) == 1
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}
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