Bump minSdk to 21 (#466)

* Bump minSdk to 21

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

* PasswordGenerator: Constify things

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

* Deprecate PRNG fixes

The problem being fixed doesn't exist on SDK 21 and above.

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

* treewide: Switch to lambdas

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

* treewide: Formatting fixes

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

* treewide: Remove useless casts and add missing annotations

Signed-off-by: Harsh Shandilya <msfjarvis@gmail.com>

2 files changed, 12 insertions, 323 deletions

diff --git a/app/src/main/java/com/zeapo/pwdstore/pwgen/PRNGFixes.kt b/app/src/main/java/com/zeapo/pwdstore/pwgen/PRNGFixes.kt
deleted file mode 100644
index 98c3735f..00000000
--- a/app/src/main/java/com/zeapo/pwdstore/pwgen/PRNGFixes.kt
+++ /dev/null
@@ -1,310 +0,0 @@
-package com.zeapo.pwdstore.pwgen
-
-/*
- * This software is provided 'as-is', without any express or implied
- * warranty.  In no event will Google be held liable for any damages
- * arising from the use of this software.
- *
- * Permission is granted to anyone to use this software for any purpose,
- * including commercial applications, and to alter it and redistribute it
- * freely, as long as the origin is not misrepresented.
- */
-
-import android.os.Build
-import android.os.Process
-import android.util.Log
-
-import java.io.ByteArrayOutputStream
-import java.io.DataInputStream
-import java.io.DataOutputStream
-import java.io.File
-import java.io.FileInputStream
-import java.io.FileOutputStream
-import java.io.IOException
-import java.io.OutputStream
-import java.io.UnsupportedEncodingException
-import java.security.NoSuchAlgorithmException
-import java.security.Provider
-import java.security.SecureRandom
-import java.security.SecureRandomSpi
-import java.security.Security
-
-/**
- * Fixes for the output of the default PRNG having low entropy.
- *
- * The fixes need to be applied via [.apply] before any use of Java
- * Cryptography Architecture primitives. A good place to invoke them is in the
- * application's `onCreate`.
- */
-object PRNGFixes {
-
-    private const val VERSION_CODE_JELLY_BEAN_MR2 = 18
-    private val BUILD_FINGERPRINT_AND_DEVICE_SERIAL = buildFingerprintAndDeviceSerial
-
-    private val buildFingerprintAndDeviceSerial: ByteArray
-        get() {
-            val result = StringBuilder()
-            val fingerprint = Build.FINGERPRINT
-            if (fingerprint != null) {
-                result.append(fingerprint)
-            }
-            // TODO: Build#SERIAL is deprecated and should be removed or replaced
-            val serial = Build.SERIAL
-            if (serial != null) {
-                result.append(serial)
-            }
-            try {
-                return result.toString().toByteArray(charset("UTF-8"))
-            } catch (e: UnsupportedEncodingException) {
-                throw RuntimeException("UTF-8 encoding not supported")
-            }
-        }
-
-    /**
-     * Applies all fixes.
-     *
-     * @throws SecurityException if a fix is needed but could not be applied.
-     */
-    fun apply() {
-        applyOpenSSLFix()
-        installLinuxPRNGSecureRandom()
-    }
-
-    /**
-     * Applies the fix for OpenSSL PRNG having low entropy. Does nothing if the
-     * fix is not needed.
-     *
-     * @throws SecurityException if the fix is needed but could not be applied.
-     */
-    @Throws(SecurityException::class)
-    private fun applyOpenSSLFix() {
-        if (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2) {
-            // No need to apply the fix
-            return
-        }
-
-        try {
-            // Mix in the device- and invocation-specific seed.
-            Class.forName("org.apache.harmony.xnet.provider.jsse.NativeCrypto")
-                .getMethod("RAND_seed", ByteArray::class.java)
-                .invoke(null, generateSeed())
-
-            // Mix output of Linux PRNG into OpenSSL's PRNG
-            val bytesRead = Class.forName(
-                "org.apache.harmony.xnet.provider.jsse.NativeCrypto"
-            )
-                .getMethod("RAND_load_file", String::class.java, Long::class.javaPrimitiveType)
-                .invoke(null, "/dev/urandom", 1024) as Int
-            if (bytesRead != 1024) {
-                throw IOException(
-                    "Unexpected number of bytes read from Linux PRNG: $bytesRead"
-                )
-            }
-        } catch (e: Exception) {
-            throw SecurityException("Failed to seed OpenSSL PRNG", e)
-        }
-    }
-
-    /**
-     * Installs a Linux PRNG-backed `SecureRandom` implementation as the
-     * default. Does nothing if the implementation is already the default or if
-     * there is not need to install the implementation.
-     *
-     * @throws SecurityException if the fix is needed but could not be applied.
-     */
-    @Throws(SecurityException::class)
-    private fun installLinuxPRNGSecureRandom() {
-        if (Build.VERSION.SDK_INT > VERSION_CODE_JELLY_BEAN_MR2) {
-            // No need to apply the fix
-            return
-        }
-
-        // Install a Linux PRNG-based SecureRandom implementation as the
-        // default, if not yet installed.
-        val secureRandomProviders = Security.getProviders("SecureRandom.SHA1PRNG")
-        if (secureRandomProviders == null
-            || secureRandomProviders.isEmpty()
-            || LinuxPRNGSecureRandomProvider::class.java != secureRandomProviders[0].javaClass
-        ) {
-            Security.insertProviderAt(LinuxPRNGSecureRandomProvider(), 1)
-        }
-
-        // Assert that new SecureRandom() and
-        // SecureRandom.getInstance("SHA1PRNG") return a SecureRandom backed
-        // by the Linux PRNG-based SecureRandom implementation.
-        val rng1 = SecureRandom()
-        if (LinuxPRNGSecureRandomProvider::class.java != rng1.provider.javaClass) {
-            throw SecurityException(
-                "new SecureRandom() backed by wrong Provider: " + rng1.provider.javaClass
-            )
-        }
-
-        val rng2: SecureRandom
-        try {
-            rng2 = SecureRandom.getInstance("SHA1PRNG")
-        } catch (e: NoSuchAlgorithmException) {
-            throw SecurityException("SHA1PRNG not available", e)
-        }
-
-        if (LinuxPRNGSecureRandomProvider::class.java != rng2.provider.javaClass) {
-            throw SecurityException(
-                "SecureRandom.getInstance(\"SHA1PRNG\") backed by wrong"
-                    + " Provider: " + rng2.provider.javaClass
-            )
-        }
-    }
-
-    /**
-     * `Provider` of `SecureRandom` engines which pass through
-     * all requests to the Linux PRNG.
-     */
-    private class LinuxPRNGSecureRandomProvider :
-        Provider("LinuxPRNG", 1.0, "A Linux-specific random number provider that uses" + " /dev/urandom") {
-        init {
-            // Although /dev/urandom is not a SHA-1 PRNG, some apps
-            // explicitly request a SHA1PRNG SecureRandom and we thus need to
-            // prevent them from getting the default implementation whose output
-            // may have low entropy.
-            put("SecureRandom.SHA1PRNG", LinuxPRNGSecureRandom::class.java.name)
-            put("SecureRandom.SHA1PRNG ImplementedIn", "Software")
-        }
-    }
-
-    /**
-     * [SecureRandomSpi] which passes all requests to the Linux PRNG
-     * (`/dev/urandom`).
-     */
-    class LinuxPRNGSecureRandom : SecureRandomSpi() {
-
-        /**
-         * Whether this engine instance has been seeded. This is needed because
-         * each instance needs to seed itself if the client does not explicitly
-         * seed it.
-         */
-        private var mSeeded: Boolean = false
-
-        private// NOTE: Consider inserting a BufferedInputStream between
-        // DataInputStream and FileInputStream if you need higher
-        // PRNG output performance and can live with future PRNG
-        // output being pulled into this process prematurely.
-        val urandomInputStream: DataInputStream
-            get() = synchronized(sLock) {
-                if (sUrandomIn == null) {
-                    try {
-                        sUrandomIn = DataInputStream(
-                            FileInputStream(URANDOM_FILE)
-                        )
-                    } catch (e: IOException) {
-                        throw SecurityException(
-                            "Failed to open "
-                                + URANDOM_FILE + " for reading", e
-                        )
-                    }
-                }
-                return sUrandomIn as DataInputStream
-            }
-
-        private val urandomOutputStream: OutputStream
-            @Throws(IOException::class)
-            get() = synchronized(sLock) {
-                if (sUrandomOut == null) {
-                    sUrandomOut = FileOutputStream(URANDOM_FILE)
-                }
-                return sUrandomOut as OutputStream
-            }
-
-        @Synchronized
-        override fun engineSetSeed(bytes: ByteArray) {
-            try {
-                val out: OutputStream = urandomOutputStream
-                out.write(bytes)
-                out.flush()
-            } catch (e: IOException) {
-                // On a small fraction of devices /dev/urandom is not writable.
-                // Log and ignore.
-                Log.w(
-                    PRNGFixes::class.java.simpleName,
-                    "Failed to mix seed into $URANDOM_FILE"
-                )
-            } finally {
-                mSeeded = true
-            }
-        }
-
-        @Synchronized
-        override fun engineNextBytes(bytes: ByteArray) {
-            if (!mSeeded) {
-                // Mix in the device- and invocation-specific seed.
-                engineSetSeed(generateSeed())
-            }
-
-            try {
-                val `in`: DataInputStream = urandomInputStream
-                synchronized(`in`) {
-                    `in`.readFully(bytes)
-                }
-            } catch (e: IOException) {
-                throw SecurityException(
-                    "Failed to read from $URANDOM_FILE", e
-                )
-            }
-        }
-
-        override fun engineGenerateSeed(size: Int): ByteArray {
-            val seed = ByteArray(size)
-            engineNextBytes(seed)
-            return seed
-        }
-
-        companion object {
-
-            /*
-         * IMPLEMENTATION NOTE: Requests to generate bytes and to mix in a seed
-         * are passed through to the Linux PRNG (/dev/urandom). Instances of
-         * this class seed themselves by mixing in the current time, PID, UID,
-         * build fingerprint, and hardware serial number (where available) into
-         * Linux PRNG.
-         *
-         * Concurrency: Read requests to the underlying Linux PRNG are
-         * serialized (on sLock) to ensure that multiple threads do not get
-         * duplicated PRNG output.
-         */
-
-            private val URANDOM_FILE = File("/dev/urandom")
-
-            private val sLock = Any()
-
-            /**
-             * Input stream for reading from Linux PRNG or `null` if not yet
-             * opened.
-             */
-            private var sUrandomIn: DataInputStream? = null
-
-            /**
-             * Output stream for writing to Linux PRNG or `null` if not yet
-             * opened.
-             */
-            private var sUrandomOut: OutputStream? = null
-        }
-    }
-
-    /**
-     * Generates a device- and invocation-specific seed to be mixed into the
-     * Linux PRNG.
-     */
-    private fun generateSeed(): ByteArray {
-        try {
-            val seedBuffer = ByteArrayOutputStream()
-            val seedBufferOut = DataOutputStream(seedBuffer)
-            seedBufferOut.writeLong(System.currentTimeMillis())
-            seedBufferOut.writeLong(System.nanoTime())
-            seedBufferOut.writeInt(Process.myPid())
-            seedBufferOut.writeInt(Process.myUid())
-            seedBufferOut.write(BUILD_FINGERPRINT_AND_DEVICE_SERIAL)
-            seedBufferOut.close()
-            return seedBuffer.toByteArray()
-        } catch (e: IOException) {
-            throw SecurityException("Failed to generate seed", e)
-        }
-    }
-}
diff --git a/app/src/main/java/com/zeapo/pwdstore/pwgen/PasswordGenerator.kt b/app/src/main/java/com/zeapo/pwdstore/pwgen/PasswordGenerator.kt
index 0374236c..3a7dcc27 100644
--- a/app/src/main/java/com/zeapo/pwdstore/pwgen/PasswordGenerator.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/pwgen/PasswordGenerator.kt
@@ -1,26 +1,25 @@
 package com.zeapo.pwdstore.pwgen
 
 import android.content.Context
-import android.content.SharedPreferences
 
 import java.util.ArrayList
 
 object PasswordGenerator {
-    internal val DIGITS = 0x0001
-    internal val UPPERS = 0x0002
-    internal val SYMBOLS = 0x0004
-    internal val AMBIGUOUS = 0x0008
-    internal val NO_VOWELS = 0x0010
+    internal const val DIGITS = 0x0001
+    internal const val UPPERS = 0x0002
+    internal const val SYMBOLS = 0x0004
+    internal const val AMBIGUOUS = 0x0008
+    internal const val NO_VOWELS = 0x0010
 
-    internal val DIGITS_STR = "0123456789"
-    internal val UPPERS_STR = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-    internal val LOWERS_STR = "abcdefghijklmnopqrstuvwxyz"
-    internal val SYMBOLS_STR = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
-    internal val AMBIGUOUS_STR = "B8G6I1l0OQDS5Z2"
-    internal val VOWELS_STR = "01aeiouyAEIOUY"
+    internal const val DIGITS_STR = "0123456789"
+    internal const val UPPERS_STR = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+    internal const val LOWERS_STR = "abcdefghijklmnopqrstuvwxyz"
+    internal const val SYMBOLS_STR = "!\"#$%&'()*+,-./:;<=>?@[\\]^_`{|}~"
+    internal const val AMBIGUOUS_STR = "B8G6I1l0OQDS5Z2"
+    internal const val VOWELS_STR = "01aeiouyAEIOUY"
 
     // No a, c, n, h, H, C, 1, N
-    private val pwOptions = "0ABsvy"
+    private const val pwOptions = "0ABsvy"
 
     /**
      * Sets password generation preferences.