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package main
import (
"crypto/hmac"
"crypto/sha256"
"encoding/hex"
"fmt"
"io/ioutil"
"log"
"os"
)
func main() {
user := os.Args[1]
if len(user) < 3 {
log.Fatalf("User name argument expected.")
}
encoded, err := ioutil.ReadAll(os.Stdin)
if err != nil || len(encoded) == 0 {
log.Fatalf("Expected exactly 1 secret")
}
sk, err := hex.DecodeString(string(encoded))
if err != nil || len(sk) < 32 {
log.Fatalf("hex.DecodeString() = %d, %v", len(sk), err)
return
}
mac := hmac.New(sha256.New, sk)
mac.Write([]byte(user))
fmt.Println(hex.EncodeToString(mac.Sum(nil)))
}
// ValidMAC reports whether messageMAC is a valid HMAC tag for message.
func ValidMAC(message, messageMAC, key []byte) bool {
mac := hmac.New(sha256.New, key)
mac.Write(message)
expectedMAC := mac.Sum(nil)
return hmac.Equal(messageMAC, expectedMAC)
}
var sk []byte
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