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// SPDX-License-Identifier: BSD-2-Clause
// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
package main
import (
"crypto/hmac"
"crypto/sha256"
"encoding/binary"
"net/http"
"time"
)
func makeIdentifierMAC(request *http.Request) (identifier []byte, mac []byte) {
identifier = make([]byte, 0, sha256.Size)
mac = make([]byte, 0, sha256.Size)
timeBuf := make([]byte, binary.MaxVarintLen64)
binary.PutVarint(timeBuf, time.Now().Unix()/604800)
remoteIP := getRemoteIP(request)
h := sha256.New()
h.Write(timeBuf)
h.Write(stringToBytes(remoteIP))
h.Write(stringToBytes(request.Header.Get("User-Agent")))
h.Write(stringToBytes(request.Header.Get("Accept-Encoding")))
h.Write(stringToBytes(request.Header.Get("Accept-Language")))
h.Write(privkeyHash)
identifier = h.Sum(identifier)
if len(identifier) != sha256.Size {
panic("unexpected buffer length after hashing contents")
}
m := hmac.New(sha256.New, privkey)
m.Write(identifier)
mac = m.Sum(mac)
if len(mac) != sha256.Size {
panic("unexpected buffer length after hmac")
}
return
}
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