[Notebook port 4835] Add UNIX socket support to notebook server (#525)

* [Notebook port 4835] Add UNIX socket support to notebook server

* Address some codeQL issues

Co-authored-by: Kevin Bates <kbates4@gmail.com>

.github/workflows/integration-tests.yml

@@ -0,0 +1,47 @@
+name: Jupyter Server Integration Tests [Linux]
+on:
+  push:
+    branches: 'master'
+  pull_request:
+    branches: '*'
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu]
+        python-version: [ '3.6', '3.7', '3.8', '3.9', 'pypy3' ]
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v1
+    - name: Install Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v1
+      with:
+        python-version: ${{ matrix.python-version }}
+        architecture: 'x64'
+    - name: Upgrade packaging dependencies
+      run: |
+        pip install --upgrade pip setuptools wheel --user
+    - name: Get pip cache dir
+      id: pip-cache
+      run: |
+        echo "::set-output name=dir::$(pip cache dir)"
+    - name: Cache pip
+      uses: actions/cache@v1
+      with:
+        path: ${{ steps.pip-cache.outputs.dir }}
+        key: ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ hashFiles('setup.py') }}
+        restore-keys: |
+          ${{ runner.os }}-pip-${{ matrix.python-version }}-
+          ${{ runner.os }}-pip-
+    - name: Install the Python dependencies
+      run: |
+        pip install -e ".[test]"
+    - name: List installed packages
+      run: |
+        pip freeze
+        pip check
+    - name: Run the tests
+      run: |
+        pytest -vv --integration_tests jupyter_server

jupyter_server/__init__.py

@@ -10,6 +10,8 @@
     os.path.join(os.path.dirname(__file__), 'templates'),
 ]
 
+DEFAULT_JUPYTER_SERVER_PORT = 8888
+
 del os
 
 from ._version import version_info, __version__

jupyter_server/base/handlers.py

@@ -31,7 +31,7 @@
 import jupyter_server
 from jupyter_server._tz import utcnow
 from jupyter_server.i18n import combine_translations
-from jupyter_server.utils import ensure_async, url_path_join, url_is_absolute, url_escape
+from jupyter_server.utils import ensure_async, url_path_join, url_is_absolute, url_escape, urldecode_unix_socket_path
 from jupyter_server.services.security import csp_report_uri
 
 #-----------------------------------------------------------------------------
@@ -462,13 +462,18 @@ def check_host(self):
         if host.startswith('[') and host.endswith(']'):
             host = host[1:-1]
 
-        try:
-            addr = ipaddress.ip_address(host)
-        except ValueError:
-            # Not an IP address: check against hostnames
-            allow = host in self.settings.get('local_hostnames', ['localhost'])
+        # UNIX socket handling
+        check_host = urldecode_unix_socket_path(host)
+        if check_host.startswith('/') and os.path.exists(check_host):
+            allow = True
         else:
-            allow = addr.is_loopback
+            try:
+                addr = ipaddress.ip_address(host)
+            except ValueError:
+                # Not an IP address: check against hostnames
+                allow = host in self.settings.get('local_hostnames', ['localhost'])
+            else:
+                allow = addr.is_loopback
 
         if not allow:
             self.log.warning(