Add safe random hash generators

utils.go

@@ -7,6 +7,8 @@ package headscale
 
 import (
 	"context"
+	"crypto/rand"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"net"
@@ -278,3 +280,28 @@ func containsIPPrefix(prefixes []netaddr.IPPrefix, prefix netaddr.IPPrefix) bool
 
 	return false
 }
+
+// GenerateRandomBytes returns securely generated random bytes.
+// It will return an error if the system's secure random
+// number generator fails to function correctly, in which
+// case the caller should not continue.
+func GenerateRandomBytes(n int) ([]byte, error) {
+	b := make([]byte, n)
+	_, err := rand.Read(b)
+	// Note that err == nil only if we read len(b) bytes.
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
+}
+
+// GenerateRandomStringURLSafe returns a URL-safe, base64 encoded
+// securely generated random string.
+// It will return an error if the system's secure random
+// number generator fails to function correctly, in which
+// case the caller should not continue.
+func GenerateRandomStringURLSafe(n int) (string, error) {
+	b, err := GenerateRandomBytes(n)
+	return base64.RawURLEncoding.EncodeToString(b), err
+}