Use a custom sshj config (#878)

* Use a custom sshj config

* Get random numbers directly from SecureRandom
* Use Timber calls for logging
* Remove all algorithms that are not in the Mozilla Intermediate SSH config

* Address review comments

* Fixup slf4j's custom format string format

Co-authored-by: Harsh Shandilya <msfjarvis@gmail.com>

3 files changed, 274 insertions, 23 deletions

diff --git a/app/src/main/java/com/zeapo/pwdstore/Application.kt b/app/src/main/java/com/zeapo/pwdstore/Application.kt
index b0c4eec0..c66c6486 100644
--- a/app/src/main/java/com/zeapo/pwdstore/Application.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/Application.kt
@@ -13,8 +13,7 @@ import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_YES
 import androidx.preference.PreferenceManager
 import com.github.ajalt.timberkt.Timber.DebugTree
 import com.github.ajalt.timberkt.Timber.plant
-import org.bouncycastle.jce.provider.BouncyCastleProvider
-import java.security.Security
+import com.zeapo.pwdstore.git.config.setUpBouncyCastleForSshj
 
 @Suppress("Unused")
 class Application : android.app.Application(), SharedPreferences.OnSharedPreferenceChangeListener {
@@ -29,7 +28,7 @@ class Application : android.app.Application(), SharedPreferences.OnSharedPrefere
         }
         prefs?.registerOnSharedPreferenceChangeListener(this)
         setNightMode()
-        setUpBouncyCastle()
+        setUpBouncyCastleForSshj()
     }
 
     override fun onTerminate() {
@@ -43,25 +42,6 @@ class Application : android.app.Application(), SharedPreferences.OnSharedPrefere
         }
     }
 
-    private fun setUpBouncyCastle() {
-        // Replace the Android BC provider with the Java BouncyCastle provider since the former does
-        // not include all the required algorithms.
-        // TODO: Verify that we are indeed using the fast Android-native implementation whenever
-        //  possible.
-        // Note: This may affect crypto operations in other parts of the application.
-        val bcIndex = Security.getProviders().indexOfFirst {
-            it.name == BouncyCastleProvider.PROVIDER_NAME
-        }
-        if (bcIndex == -1) {
-            // No Android BC found, install Java BC at lowest priority.
-            Security.addProvider(BouncyCastleProvider())
-        } else {
-            // Replace Android BC with Java BC, inserted at the same position.
-            Security.removeProvider(BouncyCastleProvider.PROVIDER_NAME)
-            Security.insertProviderAt(BouncyCastleProvider(), bcIndex + 1)
-        }
-    }
-
     private fun setNightMode() {
         AppCompatDelegate.setDefaultNightMode(when (prefs?.getString("app_theme", getString(R.string.app_theme_def))) {
             "light" -> MODE_NIGHT_NO
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt
new file mode 100644
index 00000000..3e67eba7
--- /dev/null
+++ b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjConfig.kt
@@ -0,0 +1,271 @@
+/*
+ * Copyright © 2014-2020 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+package com.zeapo.pwdstore.git.config
+
+import com.github.ajalt.timberkt.Timber
+import com.github.ajalt.timberkt.d
+import com.hierynomus.sshj.signature.SignatureEdDSA
+import com.hierynomus.sshj.transport.cipher.BlockCiphers
+import com.hierynomus.sshj.transport.mac.Macs
+import com.hierynomus.sshj.userauth.keyprovider.OpenSSHKeyV1KeyFile
+import net.schmizz.keepalive.KeepAliveProvider
+import net.schmizz.sshj.ConfigImpl
+import net.schmizz.sshj.common.LoggerFactory
+import net.schmizz.sshj.signature.SignatureECDSA
+import net.schmizz.sshj.signature.SignatureRSA
+import net.schmizz.sshj.signature.SignatureRSA.FactoryCERT
+import net.schmizz.sshj.transport.compression.NoneCompression
+import net.schmizz.sshj.transport.kex.Curve25519SHA256
+import net.schmizz.sshj.transport.kex.Curve25519SHA256.FactoryLibSsh
+import net.schmizz.sshj.transport.kex.DHGexSHA256
+import net.schmizz.sshj.transport.kex.ECDHNistP
+import net.schmizz.sshj.transport.random.JCERandom
+import net.schmizz.sshj.transport.random.SingletonRandomFactory
+import net.schmizz.sshj.userauth.keyprovider.OpenSSHKeyFile
+import net.schmizz.sshj.userauth.keyprovider.PKCS5KeyFile
+import net.schmizz.sshj.userauth.keyprovider.PKCS8KeyFile
+import net.schmizz.sshj.userauth.keyprovider.PuTTYKeyFile
+import org.bouncycastle.jce.provider.BouncyCastleProvider
+import org.slf4j.Logger
+import org.slf4j.Marker
+import java.security.Security
+
+
+fun setUpBouncyCastleForSshj() {
+    // Replace the Android BC provider with the Java BouncyCastle provider since the former does
+    // not include all the required algorithms.
+    // Note: This may affect crypto operations in other parts of the application.
+    val bcIndex = Security.getProviders().indexOfFirst {
+        it.name == BouncyCastleProvider.PROVIDER_NAME
+    }
+    if (bcIndex == -1) {
+        // No Android BC found, install Java BC at lowest priority.
+        Security.addProvider(BouncyCastleProvider())
+    } else {
+        // Replace Android BC with Java BC, inserted at the same position.
+        Security.removeProvider(BouncyCastleProvider.PROVIDER_NAME)
+        // May be needed on Android Pie+ as per https://stackoverflow.com/a/57897224/297261
+        try {
+            Class.forName("sun.security.jca.Providers")
+        } catch (e: ClassNotFoundException) {
+        }
+        Security.insertProviderAt(BouncyCastleProvider(), bcIndex + 1)
+    }
+    d { "JCE providers: ${Security.getProviders().joinToString { "${it.name} (${it.version})" }}" }
+}
+
+private abstract class AbstractLogger(private val name: String) : Logger {
+
+    abstract fun t(message: String, t: Throwable? = null, vararg args: Any?)
+    abstract fun d(message: String, t: Throwable? = null, vararg args: Any?)
+    abstract fun i(message: String, t: Throwable? = null, vararg args: Any?)
+    abstract fun w(message: String, t: Throwable? = null, vararg args: Any?)
+    abstract fun e(message: String, t: Throwable? = null, vararg args: Any?)
+
+    override fun getName() = name
+
+    override fun isTraceEnabled(marker: Marker?): Boolean = isTraceEnabled
+    override fun isDebugEnabled(marker: Marker?): Boolean = isDebugEnabled
+    override fun isInfoEnabled(marker: Marker?): Boolean = isInfoEnabled
+    override fun isWarnEnabled(marker: Marker?): Boolean = isWarnEnabled
+    override fun isErrorEnabled(marker: Marker?): Boolean = isErrorEnabled
+
+    override fun trace(msg: String) = t(msg)
+    override fun trace(format: String, arg: Any?) = t(format, null, arg)
+    override fun trace(format: String, arg1: Any?, arg2: Any?) = t(format, null, arg1, arg2)
+    override fun trace(format: String, vararg arguments: Any?) = t(format, null, *arguments)
+    override fun trace(msg: String, t: Throwable?) = t(msg, t)
+    override fun trace(marker: Marker, msg: String) = trace(msg)
+    override fun trace(marker: Marker?, format: String, arg: Any?) = trace(format, arg)
+    override fun trace(marker: Marker?, format: String, arg1: Any?, arg2: Any?) =
+        trace(format, arg1, arg2)
+
+    override fun trace(marker: Marker?, format: String, vararg arguments: Any?) =
+        trace(format, *arguments)
+
+    override fun trace(marker: Marker?, msg: String, t: Throwable?) = trace(msg, t)
+
+    override fun debug(msg: String) = d(msg)
+    override fun debug(format: String, arg: Any?) = d(format, null, arg)
+    override fun debug(format: String, arg1: Any?, arg2: Any?) = d(format, null, arg1, arg2)
+    override fun debug(format: String, vararg arguments: Any?) = d(format, null, *arguments)
+    override fun debug(msg: String, t: Throwable?) = d(msg, t)
+    override fun debug(marker: Marker, msg: String) = debug(msg)
+    override fun debug(marker: Marker?, format: String, arg: Any?) = debug(format, arg)
+    override fun debug(marker: Marker?, format: String, arg1: Any?, arg2: Any?) =
+        debug(format, arg1, arg2)
+
+    override fun debug(marker: Marker?, format: String, vararg arguments: Any?) =
+        debug(format, *arguments)
+
+    override fun debug(marker: Marker?, msg: String, t: Throwable?) = debug(msg, t)
+
+    override fun info(msg: String) = i(msg)
+    override fun info(format: String, arg: Any?) = i(format, null, arg)
+    override fun info(format: String, arg1: Any?, arg2: Any?) = i(format, null, arg1, arg2)
+    override fun info(format: String, vararg arguments: Any?) = i(format, null, *arguments)
+    override fun info(msg: String, t: Throwable?) = i(msg, t)
+    override fun info(marker: Marker, msg: String) = info(msg)
+    override fun info(marker: Marker?, format: String, arg: Any?) = info(format, arg)
+    override fun info(marker: Marker?, format: String, arg1: Any?, arg2: Any?) =
+        info(format, arg1, arg2)
+
+    override fun info(marker: Marker?, format: String, vararg arguments: Any?) =
+        info(format, *arguments)
+
+    override fun info(marker: Marker?, msg: String, t: Throwable?) = info(msg, t)
+
+    override fun warn(msg: String) = w(msg)
+    override fun warn(format: String, arg: Any?) = w(format, null, arg)
+    override fun warn(format: String, arg1: Any?, arg2: Any?) = w(format, null, arg1, arg2)
+    override fun warn(format: String, vararg arguments: Any?) = w(format, null, *arguments)
+    override fun warn(msg: String, t: Throwable?) = w(msg, t)
+    override fun warn(marker: Marker, msg: String) = warn(msg)
+    override fun warn(marker: Marker?, format: String, arg: Any?) = warn(format, arg)
+    override fun warn(marker: Marker?, format: String, arg1: Any?, arg2: Any?) =
+        warn(format, arg1, arg2)
+
+    override fun warn(marker: Marker?, format: String, vararg arguments: Any?) =
+        warn(format, *arguments)
+
+    override fun warn(marker: Marker?, msg: String, t: Throwable?) = warn(msg, t)
+
+    override fun error(msg: String) = e(msg)
+    override fun error(format: String, arg: Any?) = e(format, null, arg)
+    override fun error(format: String, arg1: Any?, arg2: Any?) = e(format, null, arg1, arg2)
+    override fun error(format: String, vararg arguments: Any?) = e(format, null, *arguments)
+    override fun error(msg: String, t: Throwable?) = e(msg, t)
+    override fun error(marker: Marker, msg: String) = error(msg)
+    override fun error(marker: Marker?, format: String, arg: Any?) = error(format, arg)
+    override fun error(marker: Marker?, format: String, arg1: Any?, arg2: Any?) =
+        error(format, arg1, arg2)
+
+    override fun error(marker: Marker?, format: String, vararg arguments: Any?) =
+        error(format, *arguments)
+
+    override fun error(marker: Marker?, msg: String, t: Throwable?) = error(msg, t)
+}
+
+object TimberLoggerFactory : LoggerFactory {
+    private class TimberLogger(name: String) : AbstractLogger(name) {
+
+        // We defer the log level checks to Timber.
+        override fun isTraceEnabled() = true
+        override fun isDebugEnabled() = true
+        override fun isInfoEnabled() = true
+        override fun isWarnEnabled() = true
+        override fun isErrorEnabled() = true
+
+        // Replace slf4j's "{}" format string style with standard Java's "%s".
+        // The supposedly redundant escape on the } is not redundant.
+        @Suppress("RegExpRedundantEscape")
+        private fun String.fix() = replace("""(?!<\\)\{\}""".toRegex(), "%s")
+
+        override fun t(message: String, t: Throwable?, vararg args: Any?) {
+            Timber.tag(name).v(t, message.fix(), *args)
+        }
+
+        override fun d(message: String, t: Throwable?, vararg args: Any?) {
+            Timber.tag(name).d(t, message.fix(), *args)
+        }
+
+        override fun i(message: String, t: Throwable?, vararg args: Any?) {
+            Timber.tag(name).i(t, message.fix(), *args)
+        }
+
+        override fun w(message: String, t: Throwable?, vararg args: Any?) {
+            Timber.tag(name).w(t, message.fix(), *args)
+        }
+
+        override fun e(message: String, t: Throwable?, vararg args: Any?) {
+            Timber.tag(name).e(t, message.fix(), *args)
+        }
+    }
+
+    override fun getLogger(name: String): Logger {
+        return TimberLogger(name)
+    }
+
+    override fun getLogger(clazz: Class<*>): Logger {
+        return TimberLogger(clazz.name)
+    }
+
+}
+
+class SshjConfig : ConfigImpl() {
+
+    init {
+        loggerFactory = TimberLoggerFactory
+        keepAliveProvider = KeepAliveProvider.HEARTBEAT
+
+        initKeyExchangeFactories()
+        initSignatureFactories()
+        initRandomFactory()
+        initFileKeyProviderFactories()
+        initCipherFactories()
+        initCompressionFactories()
+        initMACFactories()
+    }
+
+    private fun initKeyExchangeFactories() {
+        keyExchangeFactories = listOf(
+            Curve25519SHA256.Factory(),
+            FactoryLibSsh(),
+            ECDHNistP.Factory521(),
+            ECDHNistP.Factory384(),
+            ECDHNistP.Factory256(),
+            DHGexSHA256.Factory()
+        )
+    }
+
+    private fun initSignatureFactories() {
+        signatureFactories = listOf(
+            SignatureEdDSA.Factory(),
+            SignatureECDSA.Factory256(),
+            SignatureECDSA.Factory384(),
+            SignatureECDSA.Factory521(),
+            SignatureRSA.Factory(),
+            FactoryCERT()
+        )
+    }
+
+    private fun initRandomFactory() {
+        randomFactory = SingletonRandomFactory(JCERandom.Factory())
+    }
+
+    private fun initFileKeyProviderFactories() {
+        fileKeyProviderFactories = listOf(
+            OpenSSHKeyV1KeyFile.Factory(),
+            PKCS8KeyFile.Factory(),
+            PKCS5KeyFile.Factory(),
+            OpenSSHKeyFile.Factory(),
+            PuTTYKeyFile.Factory()
+        )
+    }
+
+
+    private fun initCipherFactories() {
+        cipherFactories = listOf(
+            BlockCiphers.AES128CTR(),
+            BlockCiphers.AES192CTR(),
+            BlockCiphers.AES256CTR()
+        )
+    }
+
+    private fun initMACFactories() {
+        macFactories = listOf(
+            Macs.HMACSHA2256(),
+            Macs.HMACSHA2256Etm(),
+            Macs.HMACSHA2512(),
+            Macs.HMACSHA2512Etm()
+        )
+    }
+
+    private fun initCompressionFactories() {
+        compressionFactories = listOf(
+            NoneCompression.Factory()
+        )
+    }
+}
diff --git a/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt
index f643c714..61b7ec16 100644
--- a/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt
+++ b/app/src/main/java/com/zeapo/pwdstore/git/config/SshjSessionFactory.kt
@@ -128,7 +128,7 @@ private class SshjSession(private val uri: URIish, private val username: String,
     private var currentCommand: Session? = null
 
     fun connect(): SshjSession {
-        ssh = SSHClient()
+        ssh = SSHClient(SshjConfig())
         ssh.addHostKeyVerifier(makeTofuHostKeyVerifier(hostKeyFile))
         ssh.connect(uri.host, uri.port.takeUnless { it == -1 } ?: 22)
         if (!ssh.isConnected)