diff -r f2c8f6b11dcf -r a967b5a07f92 src/Pure/General/ssh.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/General/ssh.scala	Sun Oct 09 23:08:40 2016 +0200
@@ -0,0 +1,107 @@
+/*  Title:      Pure/General/ssh.scala
+    Author:     Makarius
+
+Support for Secure Shell.
+*/
+
+package isabelle
+
+
+import com.jcraft.jsch.{JSch, Logger => JSch_Logger, Session => JSch_Session,
+  OpenSSHConfig, UserInfo, ChannelExec, ChannelSftp}
+
+
+object SSH
+{
+  /* init */
+
+  def apply(config_dir: Path = Path.explode("~/.ssh"),
+    config_file: Path = Path.explode("~/.ssh/config"),
+    identity_files: List[Path] =
+      List("~/.ssh/id_dsa", "~/.ssh/id_ecdsa", "~/.ssh/id_rsa").map(Path.explode(_))): SSH =
+  {
+    if (!config_dir.is_dir) error("Bad ssh config directory: " + config_dir)
+
+    val jsch = new JSch
+
+    if (config_file.is_file)
+      jsch.setConfigRepository(OpenSSHConfig.parseFile(File.platform_path(config_file)))
+
+    val known_hosts = config_dir + Path.explode("known_hosts")
+    if (!known_hosts.is_file) known_hosts.file.createNewFile
+    jsch.setKnownHosts(File.platform_path(known_hosts))
+
+    for (identity_file <- identity_files if identity_file.is_file)
+      jsch.addIdentity(File.platform_path(identity_file))
+
+    new SSH(jsch)
+  }
+
+
+  /* logging */
+
+  def logging(verbose: Boolean = true, debug: Boolean = false)
+  {
+    JSch.setLogger(if (verbose) new Logger(debug) else null)
+  }
+
+  private class Logger(debug: Boolean) extends JSch_Logger
+  {
+    def isEnabled(level: Int): Boolean = level != JSch_Logger.DEBUG || debug
+
+    def log(level: Int, msg: String)
+    {
+      level match {
+        case JSch_Logger.ERROR | JSch_Logger.FATAL => Output.error_message(msg)
+        case JSch_Logger.WARN => Output.warning(msg)
+        case _ => Output.writeln(msg)
+      }
+    }
+  }
+
+
+  /* session */
+
+  class Session private[SSH](val jsch: JSch, val session: JSch_Session)
+  {
+    override def toString: String =
+      (if (session.getUserName == null) "" else session.getUserName + "@") +
+      (if (session.getHost == null) "" else session.getHost) +
+      (if (session.getPort == 22) "" else ":" + session.getPort)
+
+    def open: Session = { session.connect; this }
+    def close: Session = { session.disconnect; this }
+
+    def channel_exec: ChannelExec =
+      session.openChannel("exec").asInstanceOf[ChannelExec]
+
+    def channel_sftp: ChannelSftp =
+      session.openChannel("sftp").asInstanceOf[ChannelSftp]
+  }
+
+  object No_User_Info extends UserInfo
+  {
+    def getPassphrase: String = null
+    def getPassword: String = null
+    def promptPassword(msg: String): Boolean = false
+    def promptPassphrase(msg: String): Boolean = false
+    def promptYesNo(msg: String): Boolean = false
+    def showMessage(msg: String): Unit = Output.writeln(msg)
+  }
+}
+
+class SSH private(val jsch: JSch)
+{
+  def session(host: String, port: Int = 22, user: String = null,
+      compression: Boolean = true): SSH.Session =
+  {
+    val session = jsch.getSession(user, host, port)
+    if (compression) {
+      session.setConfig("compression.s2c", "zlib@openssh.com,zlib,none")
+      session.setConfig("compression.c2s", "zlib@openssh.com,zlib,none")
+      session.setConfig("compression_level", "9")
+    }
+    session.setUserInfo(SSH.No_User_Info)
+    new SSH.Session(jsch, session)
+  }
+}