AUTH-2052: Adds tests for SSH server

.gitignore

@@ -13,3 +13,4 @@ cloudflared.exe
 !cmd/cloudflared/
 .DS_Store
 *-session.log
+ssh_server_tests/.env

Makefile

@@ -39,6 +39,10 @@ container:
 test: vet
 	go test -v -race $(VERSION_FLAGS) ./...
 
+.PHONY: test-ssh-server
+test-ssh-server:
+	docker-compose -f ssh_server_tests/docker-compose.yml up
+
 .PHONY: cloudflared-deb
 cloudflared-deb: cloudflared
 	mkdir -p $(PACKAGE_DIR)

ssh_server_tests/Dockerfile

@@ -0,0 +1,14 @@
+FROM python:3-buster
+
+RUN wget https://bin.equinox.io/c/VdrWdbjqyF/cloudflared-stable-linux-amd64.deb \
+  && dpkg -i cloudflared-stable-linux-amd64.deb
+
+RUN pip install pexpect
+
+COPY tests.py .
+COPY ssh /root/.ssh
+RUN chmod 600 /root/.ssh/id_rsa
+
+ARG SSH_HOSTNAME
+RUN bash -c 'sed -i "s/{{hostname}}/${SSH_HOSTNAME}/g" /root/.ssh/authorized_keys_config'
+RUN bash -c 'sed -i "s/{{hostname}}/${SSH_HOSTNAME}/g" /root/.ssh/short_lived_cert_config'

ssh_server_tests/README.md

@@ -0,0 +1,23 @@
+# Cloudflared SSH server smoke tests
+
+Runs several tests in a docker container against a server that is started out of band of these tests.
+Cloudflared token also needs to be retrieved out of band.
+SSH server hostname and user need to be configured in a docker environment file
+
+
+## Running tests
+
+* Build cloudflared:
+make cloudflared
+
+* Start server:
+sudo ./cloudflared tunnel --hostname HOSTNAME --ssh-server
+
+* Fetch token: 
+./cloudflared access login HOSTNAME
+
+* Create docker env file:
+echo "SSH_HOSTNAME=HOSTNAME\nSSH_USER=USERNAME\n" > ssh_server_tests/.env
+
+* Run tests:
+make test-ssh-server

ssh_server_tests/docker-compose.yml

@@ -0,0 +1,19 @@
+version: "3.1"
+
+services:
+  ssh_test:
+    build:
+      context: .
+      args:
+        - SSH_HOSTNAME=${SSH_HOSTNAME}
+    volumes:
+      - "~/.cloudflared/:/root/.cloudflared"
+    env_file:
+     - .env
+    environment:
+      - AUTHORIZED_KEYS_SSH_CONFIG=/root/.ssh/authorized_keys_config
+      - SHORT_LIVED_CERT_SSH_CONFIG=/root/.ssh/short_lived_cert_config
+      - REMOTE_SCP_FILENAME=scp_test.txt
+      - ROOT_ONLY_TEST_FILE_PATH=~/permission_test.txt
+
+    entrypoint: "python tests.py"

ssh_server_tests/ssh/authorized_keys_config

@@ -0,0 +1,5 @@
+Host *
+    AddressFamily inet
+
+Host {{hostname}}
+  ProxyCommand /usr/local/bin/cloudflared access ssh --hostname %h

ssh_server_tests/ssh/id_rsa

@@ -0,0 +1,49 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAACFwAAAAdzc2gtcn
+NhAAAAAwEAAQAAAgEAvi26NDQ8cYTTztqPe9ZgF5HR/rIo5FoDgL5NbbZKW6h0txP9Fd8s
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+/+FFvljm5nSDAAAAEW1pa2VAQzAyWTUwVEdKR0g4AQ==
+-----END OPENSSH PRIVATE KEY-----

ssh_server_tests/ssh/id_rsa.pub

@@ -0,0 +1 @@
+ssh-rsa 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 mike@C02Y50TGJGH8

ssh_server_tests/ssh/short_lived_cert_config

@@ -0,0 +1,11 @@
+Host *
+    AddressFamily inet
+
+Host {{hostname}}
+  ProxyCommand bash -c '/usr/local/bin/cloudflared access ssh-gen --hostname %h; ssh -F /root/.ssh/short_lived_cert_config -tt %r@cfpipe-{{hostname}} >&2 <&1'
+
+Host cfpipe-{{hostname}}
+  HostName {{hostname}}
+  ProxyCommand /usr/local/bin/cloudflared access ssh --hostname %h
+  IdentityFile ~/.cloudflared/{{hostname}}-cf_key
+  CertificateFile ~/.cloudflared/{{hostname}}-cf_key-cert.pub

ssh_server_tests/tests.py

@@ -0,0 +1,195 @@
+"""
+Cloudflared Integration tests
+"""
+
+import unittest
+import subprocess
+import os
+import tempfile
+from contextlib import contextmanager
+
+from pexpect import pxssh
+
+
+class TestSSHBase(unittest.TestCase):
+    """
+    SSH test base class containing constants and helper funcs
+    """
+
+    HOSTNAME = os.environ["SSH_HOSTNAME"]
+    SSH_USER = os.environ["SSH_USER"]
+    SSH_TARGET = f"{SSH_USER}@{HOSTNAME}"
+    AUTHORIZED_KEYS_SSH_CONFIG = os.environ["AUTHORIZED_KEYS_SSH_CONFIG"]
+    SHORT_LIVED_CERT_SSH_CONFIG = os.environ["SHORT_LIVED_CERT_SSH_CONFIG"]
+    SSH_OPTIONS = {"StrictHostKeyChecking": "no"}
+
+    @classmethod
+    def get_ssh_command(cls, pty=True):
+        """
+        Return ssh command arg list. If pty is true, a PTY is forced for the session.
+        """
+        cmd = [
+            "ssh",
+            "-o",
+            "StrictHostKeyChecking=no",
+            "-F",
+            cls.AUTHORIZED_KEYS_SSH_CONFIG,
+            cls.SSH_TARGET,
+        ]
+        if not pty:
+            cmd += ["-T"]
+        else:
+            cmd += ["-tt"]
+
+        return cmd
+
+    @classmethod
+    @contextmanager
+    def ssh_session_manager(cls, *args, **kwargs):
+        """
+        Context manager for interacting with a pxssh session.
+        Disables pty echo on the remote server and ensures session is terminated afterward.
+        """
+        session = pxssh.pxssh(options=cls.SSH_OPTIONS)
+
+        session.login(
+            cls.HOSTNAME,
+            username=cls.SSH_USER,
+            original_prompt=r"[#@$]",
+            ssh_config=kwargs.get("ssh_config", cls.AUTHORIZED_KEYS_SSH_CONFIG),
+            ssh_tunnels=kwargs.get("ssh_tunnels", {}),
+        )
+        try:
+            session.sendline("stty -echo")
+            session.prompt()
+            yield session
+        finally:
+            session.logout()
+
+    @staticmethod
+    def get_command_output(session, cmd):
+        """
+        Executes command on remote ssh server and waits for prompt.
+        Returns command output
+        """
+        session.sendline(cmd)
+        session.prompt()
+        return session.before.decode().strip()
+
+    def exec_command(self, cmd, shell=False):
+        """
+        Executes command locally. Raises Assertion error for non-zero return code.
+        Returns stdout and stderr
+        """
+        proc = subprocess.Popen(
+            cmd, stderr=subprocess.PIPE, stdout=subprocess.PIPE, shell=shell
+        )
+        raw_out, raw_err = proc.communicate()
+
+        out = raw_out.decode()
+        err = raw_err.decode()
+        self.assertEqual(proc.returncode, 0, msg=f"stdout: {out} stderr: {err}")
+        return out.strip(), err.strip()
+
+
+class TestSSHCommandExec(TestSSHBase):
+    """
+    Tests inline ssh command exec
+    """
+
+    # Name of file to be downloaded over SCP on remote server.
+    REMOTE_SCP_FILENAME = os.environ["REMOTE_SCP_FILENAME"]
+
+    @classmethod
+    def get_scp_base_command(cls):
+        return [
+            "scp",
+            "-o",
+            "StrictHostKeyChecking=no",
+            "-v",
+            "-F",
+            cls.AUTHORIZED_KEYS_SSH_CONFIG,
+        ]
+
+    @unittest.skip(
+        "This creates files on the remote. Should be skipped until server is dockerized."
+    )
+    def test_verbose_scp_sink_mode(self):
+        with tempfile.NamedTemporaryFile() as fl:
+            self.exec_command(
+                self.get_scp_base_command() + [fl.name, f"{self.SSH_TARGET}:"]
+            )
+
+    def test_verbose_scp_source_mode(self):
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            self.exec_command(
+                self.get_scp_base_command()
+                + [f"{self.SSH_TARGET}:{self.REMOTE_SCP_FILENAME}", tmpdirname]
+            )
+            local_filename = os.path.join(tmpdirname, self.REMOTE_SCP_FILENAME)
+
+            self.assertTrue(os.path.exists(local_filename))
+            self.assertTrue(os.path.getsize(local_filename) > 0)
+
+    def test_pty_command(self):
+        base_cmd = self.get_ssh_command()
+
+        out, _ = self.exec_command(base_cmd + ["whoami"])
+        self.assertEqual(out.strip().lower(), self.SSH_USER.lower())
+
+        out, _ = self.exec_command(base_cmd + ["tty"])
+        self.assertNotEqual(out, "not a tty")
+
+    def test_non_pty_command(self):
+        base_cmd = self.get_ssh_command(pty=False)
+
+        out, _ = self.exec_command(base_cmd + ["whoami"])
+        self.assertEqual(out.strip().lower(), self.SSH_USER.lower())
+
+        out, _ = self.exec_command(base_cmd + ["tty"])
+        self.assertEqual(out, "not a tty")
+
+
+class TestSSHShell(TestSSHBase):
+    """
+    Tests interactive SSH shell
+    """
+
+    # File path to a file on the remote server with root only read privileges.
+    ROOT_ONLY_TEST_FILE_PATH = os.environ["ROOT_ONLY_TEST_FILE_PATH"]
+
+    def test_ssh_pty(self):
+        with self.ssh_session_manager() as session:
+
+            # Test shell launched as correct user
+            username = self.get_command_output(session, "whoami")
+            self.assertEqual(username.lower(), self.SSH_USER.lower())
+
+            # Test USER env variable set
+            user_var = self.get_command_output(session, "echo $USER")
+            self.assertEqual(user_var.lower(), self.SSH_USER.lower())
+
+            # Test HOME env variable set to true user home.
+            home_env = self.get_command_output(session, "echo $HOME")
+            pwd = self.get_command_output(session, "pwd")
+            self.assertEqual(pwd, home_env)
+
+            # Test shell launched in correct user home dir.
+            self.assertIn(username, pwd)
+
+            # Ensure shell launched with correct user's permissions and privs.
+            # Cant read root owned 0700 files.
+            output = self.get_command_output(
+                session, f"cat {self.ROOT_ONLY_TEST_FILE_PATH}"
+            )
+            self.assertIn("Permission denied", output)
+
+    def test_short_lived_cert_auth(self):
+        with self.ssh_session_manager(
+            ssh_config=self.SHORT_LIVED_CERT_SSH_CONFIG
+        ) as session:
+            username = self.get_command_output(session, "whoami")
+            self.assertEqual(username.lower(), self.SSH_USER.lower())
+
+
+unittest.main()

sshserver/sshserver_unix.go

@@ -88,7 +88,7 @@ func New(logManager sshlog.Manager, logger *logrus.Logger, version, address stri
 	}
 
 	// AUTH-2050: This is a temporary workaround of a timing issue in the tunnel muxer to allow further testing.
-	// TODO: Remove this 
+	// TODO: Remove this
 	sshServer.ConnCallback = func(conn net.Conn) net.Conn {
 		time.Sleep(10 * time.Millisecond)
 		return conn
@@ -216,7 +216,16 @@ func (s *SSHServer) connectionHandler(session ssh.Session) {
 
 	// Write stdin to shell
 	go func() {
-		defer shellInput.Close()
+
+		/*
+			Only close shell stdin for non-pty sessions because they have distinct stdin, stdout, and stderr.
+			This is done to prevent commands like SCP from hanging after all data has been sent.
+			PTY sessions share one file for all three streams and the shell process closes it.
+			Closing it here also closes shellOutput and causes an error on copy().
+		*/
+		if !isPty {
+			defer shellInput.Close()
+		}
 		if _, err := io.Copy(shellInput, session); err != nil {
 			s.logger.WithError(err).Error("Failed to write incoming command to pty")
 		}