40 lines
907 B
Go
40 lines
907 B
Go
package rfc4757
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import (
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"bytes"
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"encoding/hex"
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"errors"
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"fmt"
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"io"
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"golang.org/x/crypto/md4"
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)
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// StringToKey returns a key derived from the string provided according to the definition in RFC 4757.
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func StringToKey(secret string) ([]byte, error) {
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b := make([]byte, len(secret)*2, len(secret)*2)
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for i, r := range secret {
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u := fmt.Sprintf("%04x", r)
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c, err := hex.DecodeString(u)
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if err != nil {
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return []byte{}, errors.New("character could not be encoded")
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}
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// Swap round the two bytes to make little endian as we put into byte slice
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b[2*i] = c[1]
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b[2*i+1] = c[0]
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}
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r := bytes.NewReader(b)
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h := md4.New()
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_, err := io.Copy(h, r)
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if err != nil {
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return []byte{}, err
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}
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return h.Sum(nil), nil
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}
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func deriveKeys(key, checksum []byte, usage uint32, export bool) (k1, k2, k3 []byte) {
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k1 = key
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k2 = HMAC(k1, UsageToMSMsgType(usage))
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k3 = HMAC(k2, checksum)
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return
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}
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