1 files changed, 87 insertions, 0 deletions
diff --git a/vendor/go.mau.fi/util/random/string.go b/vendor/go.mau.fi/util/random/string.go
new file mode 100644
index 0000000..b9cb0ae
--- /dev/null
+++ b/vendor/go.mau.fi/util/random/string.go
@@ -0,0 +1,87 @@
+// Copyright (c) 2023 Tulir Asokan
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package random
+
+import (
+	"encoding/binary"
+	"hash/crc32"
+	"strings"
+	"unsafe"
+)
+
+const letters = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+// StringBytes generates a random string of the given length and returns it as a byte array.
+func StringBytes(n int) []byte {
+	if n <= 0 {
+		return []byte{}
+	}
+	input := Bytes(n * 2)
+	for i := 0; i < n; i++ {
+		// Risk of modulo bias is only 2 in 65535, values between 0 and 65533 are uniformly distributed
+		input[i] = letters[binary.BigEndian.Uint16(input[i*2:])%uint16(len(letters))]
+	}
+	input = input[:n]
+	return input
+}
+
+// String generates a random string of the given length.
+func String(n int) string {
+	if n <= 0 {
+		return ""
+	}
+	str := StringBytes(n)
+	return *(*string)(unsafe.Pointer(&str))
+}
+
+func base62Encode(val uint32, minWidth int) []byte {
+	out := make([]byte, 0, minWidth)
+	for val > 0 {
+		out = append(out, letters[val%uint32(len(letters))])
+		val /= 62
+	}
+	if len(out) < minWidth {
+		paddedOut := make([]byte, minWidth)
+		copy(paddedOut[minWidth-len(out):], out)
+		for i := 0; i < minWidth-len(out); i++ {
+			paddedOut[i] = '0'
+		}
+		out = paddedOut
+	}
+	return out
+}
+
+// Token generates a GitHub-style token with the given prefix, a random part, and a checksum at the end.
+// The format is `prefix_random_checksum`. The checksum is always 6 characters.
+func Token(namespace string, randomLength int) string {
+	token := make([]byte, len(namespace)+1+randomLength+1+6)
+	copy(token, namespace)
+	token[len(namespace)] = '_'
+	copy(token[len(namespace)+1:], StringBytes(randomLength))
+	token[len(namespace)+randomLength+1] = '_'
+	checksum := base62Encode(crc32.ChecksumIEEE(token[:len(token)-7]), 6)
+	copy(token[len(token)-6:], checksum)
+	return *(*string)(unsafe.Pointer(&token))
+}
+
+// GetTokenPrefix parses the given token generated with Token, validates the checksum and returns the prefix namespace.
+func GetTokenPrefix(token string) string {
+	parts := strings.Split(token, "_")
+	if len(parts) != 3 {
+		return ""
+	}
+	checksum := base62Encode(crc32.ChecksumIEEE([]byte(parts[0]+"_"+parts[1])), 6)
+	if string(checksum) != parts[2] {
+		return ""
+	}
+	return parts[0]
+}
+
+// IsToken checks if the given token is a valid token generated with Token with the given namespace..
+func IsToken(namespace, token string) bool {
+	return GetTokenPrefix(token) == namespace
+}