Description: Refuse to connect to ssh hostnames starting with a dash. Fixes LP:1710979
Author: Jelmer Vernooij <jelmer@jelmer.uk>
Origin: commit, Revision ID: jelmer@jelmer.uk-20170819145828-qk2p7qlg5j2fbsiz

* Security fix: hostnames starting with a dash in bzr+ssh URLs
  are now filtered out when using a subprocess SSH client.
  .
  Thanks to Augie Fackler for reporting.
  (Jelmer Vernooij, #1710979)


=== modified file 'bzrlib/tests/test_ssh_transport.py'
---
 bzrlib/tests/test_ssh_transport.py |   38 ++++++++++++++++++++++++++++++++++++-
 bzrlib/transport/ssh.py            |   16 +++++++++++++--
 2 files changed, 51 insertions(+), 3 deletions(-)

Index: b/bzrlib/tests/test_ssh_transport.py
===================================================================
--- a/bzrlib/tests/test_ssh_transport.py
+++ b/bzrlib/tests/test_ssh_transport.py
@@ -22,6 +22,7 @@ from bzrlib.transport.ssh import (
     SSHCorpSubprocessVendor,
     LSHSubprocessVendor,
     SSHVendorManager,
+    StrangeHostname,
     )
 
 
@@ -161,6 +162,19 @@ class SSHVendorManagerTests(TestCase):
 
 class SubprocessVendorsTests(TestCase):
 
+    def test_openssh_command_tricked(self):
+        vendor = OpenSSHSubprocessVendor()
+        self.assertEqual(
+            vendor._get_vendor_specific_argv(
+                "user", "-oProxyCommand=blah", 100, command=["bzr"]),
+            ["ssh", "-oForwardX11=no", "-oForwardAgent=no",
+                "-oClearAllForwardings=yes",
+                "-oNoHostAuthenticationForLocalhost=yes",
+                "-p", "100",
+                "-l", "user",
+                "--",
+                "-oProxyCommand=blah", "bzr"])
+
     def test_openssh_command_arguments(self):
         vendor = OpenSSHSubprocessVendor()
         self.assertEqual(
@@ -171,6 +185,7 @@ class SubprocessVendorsTests(TestCase):
                 "-oNoHostAuthenticationForLocalhost=yes",
                 "-p", "100",
                 "-l", "user",
+                "--",
                 "host", "bzr"]
             )
 
@@ -184,9 +199,16 @@ class SubprocessVendorsTests(TestCase):
                 "-oNoHostAuthenticationForLocalhost=yes",
                 "-p", "100",
                 "-l", "user",
-                "-s", "host", "sftp"]
+                "-s", "--", "host", "sftp"]
             )
 
+    def test_openssh_command_tricked(self):
+        vendor = SSHCorpSubprocessVendor()
+        self.assertRaises(
+            StrangeHostname,
+            vendor._get_vendor_specific_argv,
+                "user", "-oProxyCommand=host", 100, command=["bzr"])
+
     def test_sshcorp_command_arguments(self):
         vendor = SSHCorpSubprocessVendor()
         self.assertEqual(
@@ -209,6 +231,13 @@ class SubprocessVendorsTests(TestCase):
                 "-s", "sftp", "host"]
             )
 
+    def test_lsh_command_tricked(self):
+        vendor = LSHSubprocessVendor()
+        self.assertRaises(
+            StrangeHostname,
+            vendor._get_vendor_specific_argv,
+                "user", "-oProxyCommand=host", 100, command=["bzr"])
+
     def test_lsh_command_arguments(self):
         vendor = LSHSubprocessVendor()
         self.assertEqual(
@@ -231,6 +260,13 @@ class SubprocessVendorsTests(TestCase):
                 "--subsystem", "sftp", "host"]
             )
 
+    def test_plink_command_tricked(self):
+        vendor = PLinkSubprocessVendor()
+        self.assertRaises(
+            StrangeHostname,
+            vendor._get_vendor_specific_argv,
+                "user", "-oProxyCommand=host", 100, command=["bzr"])
+
     def test_plink_command_arguments(self):
         vendor = PLinkSubprocessVendor()
         self.assertEqual(
Index: b/bzrlib/transport/ssh.py
===================================================================
--- a/bzrlib/transport/ssh.py
+++ b/bzrlib/transport/ssh.py
@@ -46,6 +46,10 @@ else:
     from paramiko.sftp_client import SFTPClient
 
 
+class StrangeHostname(errors.BzrError):
+    _fmt = "Refusing to connect to strange SSH hostname %(hostname)s"
+
+
 SYSTEM_HOSTKEYS = {}
 BZR_HOSTKEYS = {}
 
@@ -360,6 +364,11 @@ class SubprocessVendor(SSHVendor):
     # tests, but beware of using PIPE which may hang due to not being read.
     _stderr_target = None
 
+    @staticmethod
+    def _check_hostname(arg):
+        if arg.startswith('-'):
+            raise StrangeHostname(hostname=arg)
+
     def _connect(self, argv):
         # Attempt to make a socketpair to use as stdin/stdout for the SSH
         # subprocess.  We prefer sockets to pipes because they support
@@ -424,9 +433,9 @@ class OpenSSHSubprocessVendor(Subprocess
         if username is not None:
             args.extend(['-l', username])
         if subsystem is not None:
-            args.extend(['-s', host, subsystem])
+            args.extend(['-s', '--', host, subsystem])
         else:
-            args.extend([host] + command)
+            args.extend(['--', host] + command)
         return args
 
 register_ssh_vendor('openssh', OpenSSHSubprocessVendor())
@@ -439,6 +448,7 @@ class SSHCorpSubprocessVendor(Subprocess
 
     def _get_vendor_specific_argv(self, username, host, port, subsystem=None,
                                   command=None):
+        self._check_hostname(host)
         args = [self.executable_path, '-x']
         if port is not None:
             args.extend(['-p', str(port)])
@@ -460,6 +470,7 @@ class LSHSubprocessVendor(SubprocessVend
 
     def _get_vendor_specific_argv(self, username, host, port, subsystem=None,
                                   command=None):
+        self._check_hostname(host)
         args = [self.executable_path]
         if port is not None:
             args.extend(['-p', str(port)])
@@ -481,6 +492,7 @@ class PLinkSubprocessVendor(SubprocessVe
 
     def _get_vendor_specific_argv(self, username, host, port, subsystem=None,
                                   command=None):
+        self._check_hostname(host)
         args = [self.executable_path, '-x', '-a', '-ssh', '-2', '-batch']
         if port is not None:
             args.extend(['-P', str(port)])