From 00b8cbaa31d48326b36928228269ac14276fd5ee Mon Sep 17 00:00:00 2001
From: Ivan Alejandro <ivanalejandro0@gmail.com>
Date: Thu, 19 Feb 2015 14:12:15 -0300
Subject: Fall back to plain ZMQ if Curve is not available.

Use global flag for ZMQ_HAS_CURVE.
Closes #6646
---
 src/leap/bitmask/backend/utils.py | 54 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 2 deletions(-)

(limited to 'src/leap/bitmask/backend/utils.py')

diff --git a/src/leap/bitmask/backend/utils.py b/src/leap/bitmask/backend/utils.py
index 18e70743..b2674330 100644
--- a/src/leap/bitmask/backend/utils.py
+++ b/src/leap/bitmask/backend/utils.py
@@ -22,20 +22,63 @@ import os
 import shutil
 import stat
 
-import zmq.auth
+import zmq
 
+try:
+    import zmq.auth
+except ImportError:
+    pass
+
+from leap.bitmask.config import flags
 from leap.bitmask.util import get_path_prefix
 from leap.common.files import mkdir_p
+from leap.common.check import leap_assert
 
 logger = logging.getLogger(__name__)
 
 KEYS_DIR = os.path.join(get_path_prefix(), 'leap', 'zmq_certificates')
 
 
+def _zmq_has_curve():
+    """
+    Return whether the current ZMQ has support for auth and CurveZMQ security.
+
+    :rtype: bool
+
+     Version notes:
+       `zmq.curve_keypair()` is new in version 14.0, new in version libzmq-4.0.
+            Requires libzmq (>= 4.0) to have been linked with libsodium.
+       `zmq.auth` module is new in version 14.1
+       `zmq.has()` is new in version 14.1, new in version libzmq-4.1.
+    """
+    zmq_version = zmq.zmq_version_info()
+    pyzmq_version = zmq.pyzmq_version_info()
+
+    if pyzmq_version >= (14, 1, 0) and zmq_version >= (4, 1):
+        return zmq.has('curve')
+
+    if pyzmq_version < (14, 1, 0):
+        return False
+
+    if zmq_version < (4, 0):
+        # security is new in libzmq 4.0
+        return False
+
+    try:
+        zmq.curve_keypair()
+    except zmq.error.ZMQError:
+        # security requires libzmq to be linked against libsodium
+        return False
+
+    return True
+
+
 def generate_zmq_certificates():
     """
     Generate client and server CURVE certificate files.
     """
+    leap_assert(flags.ZMQ_HAS_CURVE, "CurveZMQ not supported!")
+
     # Create directory for certificates, remove old content if necessary
     if os.path.exists(KEYS_DIR):
         shutil.rmtree(KEYS_DIR)
@@ -53,6 +96,8 @@ def get_frontend_certificates():
     """
     Return the frontend's public and secret certificates.
     """
+    leap_assert(flags.ZMQ_HAS_CURVE, "CurveZMQ not supported!")
+
     frontend_secret_file = os.path.join(KEYS_DIR, "frontend.key_secret")
     public, secret = zmq.auth.load_certificate(frontend_secret_file)
     return public, secret
@@ -62,6 +107,8 @@ def get_backend_certificates(base_dir='.'):
     """
     Return the backend's public and secret certificates.
     """
+    leap_assert(flags.ZMQ_HAS_CURVE, "CurveZMQ not supported!")
+
     backend_secret_file = os.path.join(KEYS_DIR, "backend.key_secret")
     public, secret = zmq.auth.load_certificate(backend_secret_file)
     return public, secret
@@ -84,5 +131,8 @@ def generate_zmq_certificates_if_needed():
     Generate the needed ZMQ certificates for backend/frontend communication if
     needed.
     """
-    if not _certificates_exist():
+    if flags.ZMQ_HAS_CURVE and not _certificates_exist():
         generate_zmq_certificates()
+
+
+flags.ZMQ_HAS_CURVE = _zmq_has_curve()
-- 
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