Kotlin conversion: Passphrase

pgpainless-core/src/main/kotlin/org/pgpainless/util/Passphrase.kt

@@ -0,0 +1,105 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.pgpainless.util
+
+import org.bouncycastle.util.Arrays
+
+/**
+ * Passphrase for keys or messages.
+ *
+ * @param chars may be null for empty passwords.
+ */
+class Passphrase(
+        chars: CharArray?
+) {
+    private val lock = Any()
+    private var valid = true
+    private val chars: CharArray?
+
+    init {
+        this.chars = trimWhitespace(chars)
+    }
+
+    /**
+     * Return a copy of the underlying char array.
+     * A return value of null represents an empty password.
+     *
+     * @return passphrase chars.
+     *
+     * @throws IllegalStateException in case the password has been cleared at this point.
+     */
+    fun getChars(): CharArray? = synchronized(lock) {
+        check(valid) { "Passphrase has been cleared." }
+        chars?.copyOf()
+    }
+
+    /**
+     * Return true if the passphrase has not yet been cleared.
+     *
+     * @return valid
+     */
+    val isValid: Boolean
+        get() = synchronized(lock) { valid }
+
+    /**
+     * Return true if the passphrase represents no password.
+     *
+     * @return empty
+     */
+    val isEmpty: Boolean
+        get() = synchronized(lock) { valid && chars == null }
+
+    /**
+     * Overwrite the char array with spaces and mark the [Passphrase] as invalidated.
+     */
+    fun clear() = synchronized(lock) {
+        chars?.fill(' ')
+        valid = false
+    }
+
+    override fun equals(other: Any?): Boolean {
+        return if (other == null)
+            false
+        else if (this === other)
+            true
+        else if (other !is Passphrase)
+            false
+        else
+            getChars() == null && other.getChars() == null || Arrays.constantTimeAreEqual(getChars(), other.getChars())
+    }
+
+    override fun hashCode(): Int = getChars()?.let { String(it) }.hashCode()
+
+    companion object {
+
+        /**
+         * Create a [Passphrase] from a [CharSequence].
+         *
+         * @param password password
+         * @return passphrase
+         */
+        @JvmStatic
+        fun fromPassword(password: CharSequence) = Passphrase(password.toString().toCharArray())
+
+        @JvmStatic
+        fun emptyPassphrase() = Passphrase(null)
+
+        /**
+         * Return a copy of the passed in char array, with leading and trailing whitespace characters removed.
+         * If the passed in char array is null, return null.
+         * If the resulting char array is empty, return null as well.
+         *
+         * @param chars char array
+         * @return copy of char array with leading and trailing whitespace characters removed
+         */
+        @JvmStatic
+        private fun trimWhitespace(chars: CharArray?): CharArray? {
+            return chars?.dropWhile { it.isWhitespace() }
+                    ?.dropLastWhile { it.isWhitespace() }
+                    ?.toCharArray()
+                    ?.let { if (it.isEmpty()) null else it }
+        }
+    }
+}