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Remove unsafe Swift code from OTP code generation #105

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Remove unsafe Swift code from OTP code generation #105

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17183c2
Do not use unsafe code
emiliopavia Dec 19, 2022
8b745be
Fix code
emiliopavia Dec 19, 2022
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7 changes: 4 additions & 3 deletions Guardian/Generators/OneTimePasswordGenerator.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -83,9 +83,10 @@ struct OneTimePasswordGenerator: TOTP, HOTP {
let buffer = Data(bytes: &c, count: MemoryLayout<UInt64>.size);
let digestData = hmac.sign(buffer)
let length = MemoryLayout<UInt32>.size
// digestData.count - 1 will always be >0, because digestData depends on algorythm and can be only 20, 32, or 64.
let offset = Int(digestData[digestData.count - 1] & 0x0f)
// offset is always <=15, length is always 4, so prefix will always be within digestData count.
guard let offset = digestData.last.map({ Int($0 & 0x0f) }),
(offset + length) < digestData.count else {
return 0
}
var hash = digestData.dropFirst(offset).prefix(length).reduce(0, { $0 << 8 | UInt32($1) })
hash &= 0x7fffffff
hash = hash % UInt32(pow(10, Float(self.parameters.digits)))
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