63 lines
1.8 KiB
Go
63 lines
1.8 KiB
Go
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package util
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import (
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"io"
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"math/big"
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)
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// AssertAvailablePRNG Assert that a cryptographically secure PRNG is available. Panic otherwise.
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func AssertAvailablePRNG() {
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buf := make([]byte, 1)
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_, err := io.ReadFull(rand.Reader, buf)
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if err != nil {
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panic(fmt.Sprintf("crypto/rand is unavailable: Read() failed with %#v", err))
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}
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}
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// GenerateRandomBytes returns securely generated random bytes.
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// It will return an error if the system's secure random
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// number generator fails to function correctly, in which
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// case the caller should not continue.
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func GenerateRandomBytes(n int) ([]byte, error) {
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b := make([]byte, n)
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_, err := rand.Read(b)
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// Note that err == nil only if we read len(b) bytes.
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if err != nil {
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return nil, err
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}
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return b, nil
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}
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// GenerateSecureRandomString returns a securely generated random string.
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// It will return an error if the system's secure random
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// number generator fails to function correctly, in which
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// case the caller should not continue.
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func GenerateSecureRandomString(n int) (string, error) {
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const letters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"
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ret := make([]byte, n)
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for i := 0; i < n; i++ {
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num, err := rand.Int(rand.Reader, big.NewInt(int64(len(letters))))
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if err != nil {
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return "", err
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}
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ret[i] = letters[num.Int64()]
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}
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return string(ret), nil
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}
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// GenerateSecureRandomStringURLSafe returns a URL-safe, base64 encoded
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// securely generated random string.
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// It will return an error if the system's secure random
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// number generator fails to function correctly, in which
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// case the caller should not continue.
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func GenerateSecureRandomStringURLSafe(n int) (string, error) {
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b, err := GenerateRandomBytes(n)
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return base64.URLEncoding.EncodeToString(b), err
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}
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