82 lines
1.9 KiB
Go
82 lines
1.9 KiB
Go
// Package pw 提供口令散列（PBKDF2-HMAC-SHA256），仅用标准库。
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package pw
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import (
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"crypto/hmac"
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"crypto/rand"
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"crypto/sha256"
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"crypto/subtle"
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"encoding/base64"
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"fmt"
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"strconv"
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"strings"
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)
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const iterations = 120000
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// Hash 生成 `pbkdf2-sha256$迭代次数$盐$摘要` 形式的字符串。
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func Hash(password string) (string, error) {
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salt := make([]byte, 16)
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if _, err := rand.Read(salt); err != nil {
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return "", err
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}
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dk := pbkdf2Key([]byte(password), salt, iterations, 32)
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return fmt.Sprintf("pbkdf2-sha256$%d$%s$%s",
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iterations,
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base64.RawStdEncoding.EncodeToString(salt),
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base64.RawStdEncoding.EncodeToString(dk)), nil
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}
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// Verify 校验口令，常量时间比较。
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func Verify(password, encoded string) bool {
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parts := strings.Split(encoded, "$")
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if len(parts) != 4 || parts[0] != "pbkdf2-sha256" {
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return false
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}
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iter, err := strconv.Atoi(parts[1])
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if err != nil || iter <= 0 {
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return false
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}
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salt, err := base64.RawStdEncoding.DecodeString(parts[2])
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if err != nil {
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return false
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}
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want, err := base64.RawStdEncoding.DecodeString(parts[3])
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if err != nil || len(want) == 0 {
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return false
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}
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got := pbkdf2Key([]byte(password), salt, iter, len(want))
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return subtle.ConstantTimeCompare(got, want) == 1
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}
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func pbkdf2Key(password, salt []byte, iter, keyLen int) []byte {
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prf := hmac.New(sha256.New, password)
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hashLen := prf.Size()
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numBlocks := (keyLen + hashLen - 1) / hashLen
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var buf [4]byte
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dk := make([]byte, 0, numBlocks*hashLen)
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u := make([]byte, hashLen)
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for block := 1; block <= numBlocks; block++ {
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prf.Reset()
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prf.Write(salt)
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buf[0] = byte(block >> 24)
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buf[1] = byte(block >> 16)
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buf[2] = byte(block >> 8)
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buf[3] = byte(block)
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prf.Write(buf[:4])
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dk = prf.Sum(dk)
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t := dk[len(dk)-hashLen:]
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copy(u, t)
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for n := 2; n <= iter; n++ {
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prf.Reset()
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prf.Write(u)
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u = u[:0]
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u = prf.Sum(u)
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for x := range u {
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t[x] ^= u[x]
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}
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}
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}
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return dk[:keyLen]
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}
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