Check signatures before invoking the container.

Also, check for new container images when starting the application.
This replaces the usage of `share/image-id.txt` to ensure the image is trusted.

dangerzone/container_utils.py

@@ -8,7 +8,8 @@ from typing import List, Optional, Tuple
 from . import errors
 from .util import get_resource_path, get_subprocess_startupinfo
 
-CONTAINER_NAME = "dangerzone.rocks/dangerzone"
+OLD_CONTAINER_NAME = "dangerzone.rocks/dangerzone"
+CONTAINER_NAME = "ghcr.io/almet/dangerzone/dangerzone"
 
 log = logging.getLogger(__name__)
 
@@ -110,12 +111,6 @@ def delete_image_tag(tag: str) -> None:
         )
 
 
-def get_expected_tag() -> str:
-    """Get the tag of the Dangerzone image tarball from the image-id.txt file."""
-    with open(get_resource_path("image-id.txt")) as f:
-        return f.read().strip()
-
-
 def load_image_tarball_in_memory() -> None:
     log.info("Installing Dangerzone container image...")
     p = subprocess.Popen(

dangerzone/isolation_provider/container.py

@@ -5,7 +5,7 @@ import shlex
 import subprocess
 from typing import List, Tuple
 
-from .. import container_utils, errors
+from .. import container_utils, errors, updater
 from ..document import Document
 from ..util import get_resource_path, get_subprocess_startupinfo
 from .base import IsolationProvider, terminate_process_group
@@ -78,40 +78,22 @@ class Container(IsolationProvider):
 
     @staticmethod
     def install() -> bool:
-        """Install the container image tarball, or verify that it's already installed.
+        """Check if an update is available and install it if necessary."""
+        # XXX Do this only if users have optted in to auto-updates
 
-        Perform the following actions:
+        # # Load the image tarball into the container runtime.
-        1. Get the tags of any locally available images that match Dangerzone's image
+        update_available, image_digest = updater.is_update_available(
-           name.
+            container_utils.CONTAINER_NAME
-        2. Get the expected image tag from the image-id.txt file.
+        )
-           - If this tag is present in the local images, then we can return.
+        if update_available:
-           - Else, prune the older container images and continue.
+            updater.upgrade_container_image(
-        3. Load the image tarball and make sure it matches the expected tag.
+                container_utils.CONTAINER_NAME,
-        """
+                image_digest,
-        old_tags = container_utils.list_image_tags()
+                updater.DEFAULT_PUBKEY_LOCATION,
-        expected_tag = container_utils.get_expected_tag()
-
-        if expected_tag not in old_tags:
-            # Prune older container images.
-            log.info(
-                f"Could not find a Dangerzone container image with tag '{expected_tag}'"
             )
-            for tag in old_tags:
-                container_utils.delete_image_tag(tag)
-        else:
-            return True
 
-        # Load the image tarball into the container runtime.
+        updater.verify_local_image(
-        container_utils.load_image_tarball_in_memory()
+            container_utils.CONTAINER_NAME, updater.DEFAULT_PUBKEY_LOCATION
-
-        # Check that the container image has the expected image tag.
-        # See https://github.com/freedomofpress/dangerzone/issues/988 for an example
-        # where this was not the case.
-        new_tags = container_utils.list_image_tags()
-        if expected_tag not in new_tags:
-            raise errors.ImageNotPresentException(
-                f"Could not find expected tag '{expected_tag}' after loading the"
-                " container image tarball"
         )
 
         return True
@@ -193,6 +175,13 @@ class Container(IsolationProvider):
         name: str,
     ) -> subprocess.Popen:
         container_runtime = container_utils.get_runtime()
+
+        image_digest = container_utils.get_local_image_digest(
+            container_utils.CONTAINER_NAME
+        )
+        updater.verify_local_image(
+            container_utils.CONTAINER_NAME, updater.DEFAULT_PUBKEY_LOCATION
+        )
         security_args = self.get_runtime_security_args()
         debug_args = []
         if self.debug:
@@ -201,9 +190,7 @@ class Container(IsolationProvider):
         enable_stdin = ["-i"]
         set_name = ["--name", name]
         prevent_leakage_args = ["--rm"]
-        image_name = [
+        image_name = [container_utils.CONTAINER_NAME + "@sha256:" + image_digest]
-            container_utils.CONTAINER_NAME + ":" + container_utils.get_expected_tag()
-        ]
         args = (
             ["run"]
             + security_args

dangerzone/updater/__init__.py

@@ -1,3 +1,10 @@
 import logging
 
 log = logging.getLogger(__name__)
+
+from .signatures import (
+    DEFAULT_PUBKEY_LOCATION,
+    is_update_available,
+    upgrade_container_image,
+    verify_local_image,
+)

dangerzone/updater/cli.py

@@ -4,13 +4,11 @@ import logging
 
 import click
 
-from ..util import get_resource_path
 from . import attestations, errors, log, registry, signatures
 
 DEFAULT_REPOSITORY = "freedomofpress/dangerzone"
 DEFAULT_BRANCH = "main"
 DEFAULT_IMAGE_NAME = "ghcr.io/freedomofpress/dangerzone/dangerzone"
-PUBKEY_DEFAULT_LOCATION = get_resource_path("freedomofpress-dangerzone-pub.key")
 
 
 @click.group()
@@ -26,7 +24,7 @@ def main(debug: bool) -> None:
 
 @main.command()
 @click.argument("image", default=DEFAULT_IMAGE_NAME)
-@click.option("--pubkey", default=PUBKEY_DEFAULT_LOCATION)
+@click.option("--pubkey", default=signatures.DEFAULT_PUBKEY_LOCATION)
 def upgrade(image: str, pubkey: str) -> None:
     """Upgrade the image to the latest signed version."""
     manifest_digest = registry.get_manifest_digest(image)

dangerzone/updater/signatures.py

@@ -11,6 +11,7 @@ from tempfile import NamedTemporaryFile, TemporaryDirectory
 from typing import Dict, List, Optional, Tuple
 
 from .. import container_utils as runtime
+from ..util import get_resource_path
 from . import cosign, errors, log, registry
 
 try:
@@ -24,6 +25,7 @@ def get_config_dir() -> Path:
 
 
 # XXX Store this somewhere else.
+DEFAULT_PUBKEY_LOCATION = get_resource_path("freedomofpress-dangerzone-pub.key")
 SIGNATURES_PATH = get_config_dir() / "signatures"
 __all__ = [
     "verify_signature",
@@ -103,12 +105,15 @@ def verify_signature(signature: dict, image_digest: str, pubkey: str) -> bool:
     return False
 
 
-def is_update_available(image: str) -> bool:
+def is_update_available(image: str) -> (bool, Optional[str]):
     remote_digest = registry.get_manifest_digest(image)
     local_digest = runtime.get_local_image_digest(image)
     log.debug("Remote digest: %s", remote_digest)
     log.debug("Local digest: %s", local_digest)
-    return remote_digest != local_digest
+    has_update = remote_digest != local_digest
+    if has_update:
+        return True, remote_digest
+    return False, None
 
 
 def verify_signatures(
@@ -124,7 +129,8 @@ def verify_signatures(
 
 def upgrade_container_image(image: str, manifest_digest: str, pubkey: str) -> bool:
     """Verify and upgrade the image to the latest, if signed."""
-    if not is_update_available(image):
+    update_available, _ = is_update_available(image)
+    if not update_available:
         raise errors.ImageAlreadyUpToDate("The image is already up to date")
 
     signatures = get_remote_signatures(image, manifest_digest)