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https://github.com/1f349/twofactor.git
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72a472700b
The counter needs to be represented in bigendian format. Unfortunately with commit #00045cb I made the unfortunate choice to swap the endiannes from big-endian to little-endian. This broke the functionality for certain counters. - [x] Added Go vendoring - [x] Bumped version of golang in travis yml file - [x] Removed conversion files and instead used import of convert sec51 external library
34 lines
877 B
Go
34 lines
877 B
Go
package cryptoengine
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import (
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"crypto/sha256"
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"errors"
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"golang.org/x/crypto/hkdf"
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"io"
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)
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// IMPORTANT !!!
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// If someone changes the hash function, then the salt needs to have the exactly same lenght!
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// So be careful when touching this.
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func deriveNonce(masterKey [keySize]byte, salt [keySize]byte, context string, counterValue string) ([nonceSize]byte, error) {
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var data24 [nonceSize]byte
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// Underlying hash function to use
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hash := sha256.New
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// Create the key derivation function
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hkdf := hkdf.New(hash, masterKey[:], salt[:], []byte(context+counterValue))
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// Generate the required keys
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key := make([]byte, nonceSize)
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n, err := io.ReadFull(hkdf, key)
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if n != len(key) || err != nil {
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return data24, err
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}
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total := copy(data24[:], key[:nonceSize])
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if total != nonceSize {
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return data24, errors.New("Could not derive a nonce.")
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}
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return data24, nil
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}
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