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Author SHA1 Message Date
ChuckBuilds fb0e869bf6 harden(install): tag the journalctl sudo grants NOEXEC
journalctl starts a pager when its output is a terminal, and from less a "!sh"
is a shell with whatever privileges journalctl was given. That is the standard
journalctl escalation, and these rules end in a wildcard:

    <user> ALL=(ALL) NOPASSWD: /usr/bin/journalctl -u ledmatrix *

Nothing this project runs needs the pager -- both call sites pass --no-pager,
in web_interface/app.py and api_v3.py. But a sudoers rule cannot require a flag
that sits in the middle of a command line, and reasoning about what a trailing
wildcard does and does not admit is exactly the kind of subtlety that produces
a hole. sudo's NOEXEC tag stops the command executing another program at all,
which closes it without depending on that reasoning.

NOEXEC works by LD_PRELOAD, so it applies to dynamically linked binaries.
Checked on the target hardware: journalctl there is dynamically linked. The
generated rules were run through `visudo -c` -- parsed OK.

Found while auditing the pre-existing wildcard grants, prompted by review
catching a far worse one I had added myself in the same area: `iptables *`,
where --modprobe runs an arbitrary path as root.

Reachability, stated plainly: on a stock Raspberry Pi image none of this
matters, because 010_pi-nopasswd already grants the default user
`ALL=(ALL) NOPASSWD: ALL`. It matters on a hardened install, or where the
service runs as a user without that blanket rule.

Two mutation checks: dropping NOEXEC from a rule fails, and deleting the rules
rather than tagging them fails too -- that second one matters, since "make the
test pass" and "remove the feature" would otherwise look the same.
2026-08-20 02:25:01 -04:00
5 changed files with 152 additions and 121 deletions
+10 -3
View File
@@ -1419,9 +1419,16 @@ $ACTUAL_USER ALL=(ALL) NOPASSWD: $BASH_PATH $PROJECT_ROOT_DIR/scripts/fix_perms/
EOF
if [ -n "$JOURNALCTL_PATH" ]; then
cat >> /tmp/ledmatrix_web_sudoers << EOF
$ACTUAL_USER ALL=(ALL) NOPASSWD: $JOURNALCTL_PATH -u ledmatrix.service *
$ACTUAL_USER ALL=(ALL) NOPASSWD: $JOURNALCTL_PATH -u ledmatrix *
$ACTUAL_USER ALL=(ALL) NOPASSWD: $JOURNALCTL_PATH -t ledmatrix *
# NOEXEC, because these rules end in a wildcard and journalctl starts a pager
# when its output is a terminal. From that pager (less) a "!sh" is a root
# shell -- the standard journalctl escalation. The web interface always passes
# --no-pager, so nothing here needs it, but the rule cannot require a flag that
# sits in the middle of the command line. NOEXEC stops the command executing
# another program at all, which closes the hole without depending on wildcard
# matching subtleties.
$ACTUAL_USER ALL=(ALL) NOPASSWD:NOEXEC: $JOURNALCTL_PATH -u ledmatrix.service *
$ACTUAL_USER ALL=(ALL) NOPASSWD:NOEXEC: $JOURNALCTL_PATH -u ledmatrix *
$ACTUAL_USER ALL=(ALL) NOPASSWD:NOEXEC: $JOURNALCTL_PATH -t ledmatrix *
EOF
fi
+1 -1
View File
@@ -328,7 +328,7 @@ class ScrollHelper:
elapsed_time = current_time - (self.scroll_start_time or current_time)
# The image already includes display_width padding, so we only need total_scroll_width
required_total_distance = self.total_scroll_width
self.logger.debug(
self.logger.info(
"Scroll progress: elapsed=%.2fs, target=%.2fs, total_scrolled=%.0f/%d px (%.1f%%)",
elapsed_time,
self.calculated_duration,
+54 -54
View File
@@ -83,7 +83,7 @@ class PluginAdapter:
# into unrelated headlines once the strip refreshed to 9,505px.
self._offset_shapes: dict = {}
logger.debug(
logger.info(
"PluginAdapter initialized: display=%dx%d",
self.display_width, self.display_height
)
@@ -109,7 +109,7 @@ class PluginAdapter:
Returns:
List of PIL Images representing plugin content, or None if no content
"""
logger.debug(
logger.info(
"[%s] Getting content (class=%s)",
plugin_id, plugin.__class__.__name__
)
@@ -118,7 +118,7 @@ class PluginAdapter:
cached = self._get_cached(plugin_id)
if cached is not None:
total_width = sum(img.width for img in cached)
logger.debug(
logger.info(
"[%s] Using cached content: %d images, %dpx total",
plugin_id, len(cached), total_width
)
@@ -126,46 +126,46 @@ class PluginAdapter:
# Try native Vegas content method first
has_native = hasattr(plugin, 'get_vegas_content')
logger.debug("[%s] Has get_vegas_content: %s", plugin_id, has_native)
logger.info("[%s] Has get_vegas_content: %s", plugin_id, has_native)
if has_native:
content = self._get_native_content(plugin, plugin_id, offscreen_only)
if content:
total_width = sum(img.width for img in content)
logger.debug(
logger.info(
"[%s] Native content SUCCESS: %d images, %dpx total",
plugin_id, len(content), total_width
)
return self._finalize(content, plugin_id, 'native', plugin)
logger.debug("[%s] Native content returned None", plugin_id)
logger.info("[%s] Native content returned None", plugin_id)
# Try to get scroll_helper's cached image (for scrolling plugins like stocks/odds)
has_scroll_helper = hasattr(plugin, 'scroll_helper')
logger.debug("[%s] Has scroll_helper: %s", plugin_id, has_scroll_helper)
logger.info("[%s] Has scroll_helper: %s", plugin_id, has_scroll_helper)
content = self._get_scroll_helper_content(plugin, plugin_id, offscreen_only)
if content:
total_width = sum(img.width for img in content)
logger.debug(
logger.info(
"[%s] ScrollHelper content SUCCESS: %d images, %dpx total",
plugin_id, len(content), total_width
)
return self._finalize(content, plugin_id, 'scroll_helper', plugin)
if has_scroll_helper:
logger.debug("[%s] ScrollHelper content returned None", plugin_id)
logger.info("[%s] ScrollHelper content returned None", plugin_id)
if offscreen_only:
# Display capture needs the shared canvas; leave it to the caller.
logger.debug(
logger.info(
"[%s] Needs display capture, deferring to the render thread",
plugin_id
)
return None
# Fall back to display capture
logger.debug("[%s] Trying fallback display capture...", plugin_id)
logger.info("[%s] Trying fallback display capture...", plugin_id)
content = self._capture_display_content(plugin, plugin_id)
if content:
total_width = sum(img.width for img in content)
logger.debug(
logger.info(
"[%s] Fallback capture SUCCESS: %d images, %dpx total",
plugin_id, len(content), total_width
)
@@ -226,7 +226,7 @@ class PluginAdapter:
kept.append(result.image)
if not kept:
logger.debug(
logger.info(
"[%s] All %d image(s) from %s were blank — contributing nothing",
plugin_id, len(images), source
)
@@ -235,14 +235,14 @@ class PluginAdapter:
trimmed_width = sum(img.width for img in kept)
if trimmed_width < self.config.min_plugin_width:
logger.debug(
logger.info(
"[%s] Trimmed content %dpx is below min_plugin_width %dpx — skipping",
plugin_id, trimmed_width, self.config.min_plugin_width
)
return None
if trimmed_width != original_width or dropped_blank:
logger.debug(
logger.info(
"[%s] Trimmed %s content: %dpx -> %dpx (%.0f%% reclaimed), "
"%d image(s) kept, %d blank dropped",
plugin_id, source, original_width, trimmed_width,
@@ -431,7 +431,7 @@ class PluginAdapter:
"""
if self._offset_shapes.get(plugin_id) != shape:
if plugin_id in self._item_offsets:
logger.debug(
logger.info(
"[%s] Content is %s now, was %s — restarting the rotation "
"rather than resuming at a position that no longer means "
"anything", plugin_id, shape,
@@ -579,7 +579,7 @@ class PluginAdapter:
consumed += 1
if mode == 'truncate':
logger.debug(
logger.info(
"[%s] Width budget %dpx: showing the first %d of %d row(s) "
"(%dpx incl. gaps); the rest are not shown (overflow=truncate)",
plugin_id, budget, len(selected), len(images), used
@@ -587,7 +587,7 @@ class PluginAdapter:
else:
self._record_offset(
plugin_id, (start + consumed) % len(images), shape)
logger.debug(
logger.info(
"[%s] Width budget %dpx: showing %d of %d row(s) (%dpx incl. gaps) "
"from offset %d; remainder deferred to a later cycle",
plugin_id, budget, len(selected), len(images), used, start
@@ -636,7 +636,7 @@ class PluginAdapter:
if mode != 'truncate':
self._record_offset(
plugin_id, 0 if end >= img.width else end, shape)
logger.debug(
logger.info(
"[%s] Width budget %dpx: cropped continuous %dpx image to "
"[%d:%d] (no item gaps of %dpx+ to align to)%s",
plugin_id, budget, img.width, offset, end, min_run,
@@ -674,7 +674,7 @@ class PluginAdapter:
self._record_offset(
plugin_id, 0 if end >= img.width else end_index, shape)
logger.debug(
logger.info(
"[%s] Width budget %dpx: cropped single %dpx image to [%d:%d] "
"(%dpx) at item boundaries %d-%d of %d, %s",
plugin_id, budget, img.width, start, end, end - start,
@@ -698,7 +698,7 @@ class PluginAdapter:
List of images or None
"""
try:
logger.debug("[%s] Native: calling get_vegas_content()", plugin_id)
logger.info("[%s] Native: calling get_vegas_content()", plugin_id)
# Tell the plugin how much width the ticker wants it to use, and
# narrow the canvas for the duration of the call. A plugin that
@@ -707,7 +707,7 @@ class PluginAdapter:
# be explicit can read get_vegas_render_width().
render_width = self.resolve_render_width(plugin, plugin_id)
if render_width != self.display_width:
logger.debug(
logger.info(
"[%s] Native: requesting %dpx instead of %dpx",
plugin_id, render_width, self.display_width
)
@@ -735,19 +735,19 @@ class PluginAdapter:
plugin._vegas_render_width = None
if result is None:
logger.debug("[%s] Native: get_vegas_content() returned None", plugin_id)
logger.info("[%s] Native: get_vegas_content() returned None", plugin_id)
return None
# Normalize to list
if isinstance(result, Image.Image):
images = [result]
logger.debug(
logger.info(
"[%s] Native: got single Image %dx%d",
plugin_id, result.width, result.height
)
elif isinstance(result, (list, tuple)):
images = list(result)
logger.debug(
logger.info(
"[%s] Native: got %d items in list/tuple",
plugin_id, len(images)
)
@@ -768,14 +768,14 @@ class PluginAdapter:
)
continue
logger.debug(
logger.info(
"[%s] Native: item[%d] is %dx%d, mode=%s",
plugin_id, i, img.width, img.height, img.mode
)
# Ensure correct height
if img.height != self.display_height:
logger.debug(
logger.info(
"[%s] Native: resizing item[%d]: %dx%d -> %dx%d",
plugin_id, i, img.width, img.height,
img.width, self.display_height
@@ -793,13 +793,13 @@ class PluginAdapter:
if valid_images:
total_width = sum(img.width for img in valid_images)
logger.debug(
logger.info(
"[%s] Native: SUCCESS - %d images, %dpx total width",
plugin_id, len(valid_images), total_width
)
return valid_images
logger.debug("[%s] Native: no valid images after validation", plugin_id)
logger.info("[%s] Native: no valid images after validation", plugin_id)
return None
except (AttributeError, TypeError, ValueError, OSError) as e:
@@ -833,20 +833,20 @@ class PluginAdapter:
logger.debug("[%s] No scroll_helper attribute", plugin_id)
return None
logger.debug(
logger.info(
"[%s] Found scroll_helper: %s",
plugin_id, type(scroll_helper).__name__
)
cached_image = getattr(scroll_helper, 'cached_image', None)
if cached_image is None:
logger.debug(
logger.info(
"[%s] scroll_helper.cached_image is None, triggering content generation",
plugin_id
)
if offscreen_only:
# Generating it calls display(), which needs the canvas.
logger.debug(
logger.info(
"[%s] scroll_helper cache empty; deferring generation "
"to the render thread", plugin_id
)
@@ -859,13 +859,13 @@ class PluginAdapter:
return None
if not isinstance(cached_image, Image.Image):
logger.debug(
logger.info(
"[%s] scroll_helper.cached_image is not an Image: %s",
plugin_id, type(cached_image).__name__
)
return None
logger.debug(
logger.info(
"[%s] scroll_helper.cached_image found: %dx%d, mode=%s",
plugin_id, cached_image.width, cached_image.height, cached_image.mode
)
@@ -888,7 +888,7 @@ class PluginAdapter:
# Ensure correct height
if img.height != self.display_height:
logger.debug(
logger.info(
"[%s] Resizing scroll_helper content: %dx%d -> %dx%d",
plugin_id, img.width, img.height,
img.width, self.display_height
@@ -902,7 +902,7 @@ class PluginAdapter:
if img.mode != 'RGB':
img = img.convert('RGB')
logger.debug(
logger.info(
"[%s] ScrollHelper content ready: %dx%d",
plugin_id, img.width, img.height
)
@@ -1002,7 +1002,7 @@ class PluginAdapter:
with self._capture():
# Method 1: Try _create_scrolling_display (stocks pattern)
if hasattr(plugin, '_create_scrolling_display'):
logger.debug(
logger.info(
"[%s] Triggering via _create_scrolling_display()",
plugin_id
)
@@ -1010,7 +1010,7 @@ class PluginAdapter:
plugin._create_scrolling_display()
cached_image = getattr(scroll_helper, 'cached_image', None)
if cached_image is not None and isinstance(cached_image, Image.Image):
logger.debug(
logger.info(
"[%s] _create_scrolling_display() SUCCESS: %dx%d",
plugin_id, cached_image.width, cached_image.height
)
@@ -1022,7 +1022,7 @@ class PluginAdapter:
# Method 2: Try display(force_clear=True) which typically builds scroll content
if hasattr(plugin, 'display'):
logger.debug(
logger.info(
"[%s] Triggering via display(force_clear=True)",
plugin_id
)
@@ -1031,12 +1031,12 @@ class PluginAdapter:
plugin.display(force_clear=True)
cached_image = getattr(scroll_helper, 'cached_image', None)
if cached_image is not None and isinstance(cached_image, Image.Image):
logger.debug(
logger.info(
"[%s] display(force_clear=True) SUCCESS: %dx%d",
plugin_id, cached_image.width, cached_image.height
)
return cached_image
logger.debug(
logger.info(
"[%s] display(force_clear=True) did not populate cached_image",
plugin_id
)
@@ -1045,7 +1045,7 @@ class PluginAdapter:
"[%s] display(force_clear=True) failed", plugin_id
)
logger.debug(
logger.info(
"[%s] Could not trigger scroll content generation",
plugin_id
)
@@ -1077,15 +1077,15 @@ class PluginAdapter:
try:
# Save current display state
original_image = self.display_manager.image.copy()
logger.debug("[%s] Fallback: saved original display state", plugin_id)
logger.info("[%s] Fallback: saved original display state", plugin_id)
# Ensure plugin has fresh data before capturing
has_update_data = hasattr(plugin, 'update_data')
logger.debug("[%s] Fallback: has update_data=%s", plugin_id, has_update_data)
logger.info("[%s] Fallback: has update_data=%s", plugin_id, has_update_data)
if has_update_data:
try:
plugin.update_data()
logger.debug("[%s] Fallback: update_data() called", plugin_id)
logger.info("[%s] Fallback: update_data() called", plugin_id)
except (AttributeError, RuntimeError, OSError):
logger.exception("[%s] Fallback: update_data() failed", plugin_id)
@@ -1097,41 +1097,41 @@ class PluginAdapter:
# arrangement rather than one that has to be cropped afterwards.
render_width = self.resolve_render_width(plugin, plugin_id)
if render_width != self.display_width:
logger.debug(
logger.info(
"[%s] Fallback: rendering at %dpx instead of %dpx",
plugin_id, render_width, self.display_width
)
with self._capture(), self._render_at(render_width):
self.display_manager.clear()
logger.debug("[%s] Fallback: display cleared, calling display()", plugin_id)
logger.info("[%s] Fallback: display cleared, calling display()", plugin_id)
# First try without force_clear (some plugins behave better this way)
try:
plugin.display()
logger.debug("[%s] Fallback: display() called successfully", plugin_id)
logger.info("[%s] Fallback: display() called successfully", plugin_id)
except TypeError:
# Plugin may require force_clear argument
logger.debug("[%s] Fallback: display() failed, trying with force_clear=True", plugin_id)
logger.info("[%s] Fallback: display() failed, trying with force_clear=True", plugin_id)
plugin.display(force_clear=True)
# Capture the result
captured = self.display_manager.image.copy()
logger.debug(
logger.info(
"[%s] Fallback: captured frame %dx%d, mode=%s",
plugin_id, captured.width, captured.height, captured.mode
)
# Check if captured image has content (not all black)
is_blank, bright_ratio = self._is_blank_image(captured, return_ratio=True)
logger.debug(
logger.info(
"[%s] Fallback: brightness check - %.3f%% bright pixels (threshold=0.5%%)",
plugin_id, bright_ratio * 100
)
if is_blank:
logger.debug(
logger.info(
"[%s] Fallback: first capture blank, retrying with force_clear",
plugin_id
)
@@ -1142,7 +1142,7 @@ class PluginAdapter:
captured = self.display_manager.image.copy()
is_blank, bright_ratio = self._is_blank_image(captured, return_ratio=True)
logger.debug(
logger.info(
"[%s] Fallback: retry brightness - %.3f%% bright pixels",
plugin_id, bright_ratio * 100
)
@@ -1159,7 +1159,7 @@ class PluginAdapter:
if captured.mode != 'RGB':
captured = captured.convert('RGB')
logger.debug(
logger.info(
"[%s] Fallback: SUCCESS - captured %dx%d",
plugin_id, captured.width, captured.height
)
+87
View File
@@ -0,0 +1,87 @@
"""Wildcard grants to commands that start a pager must carry NOEXEC.
`journalctl` runs a pager when its output is a terminal, and from `less` a
`!sh` is a shell with the privileges journalctl was given. That is the standard
journalctl privilege escalation, and the installer's rules end in a wildcard:
<user> ALL=(ALL) NOPASSWD: /usr/bin/journalctl -u ledmatrix *
The web interface always passes --no-pager -- both call sites do, in app.py and
api_v3.py -- so nothing the project runs needs the pager. But a sudoers rule
cannot require a flag that sits in the middle of the command line, and reasoning
about what a trailing `*` does or does not admit is exactly the kind of
subtlety that produces a hole.
sudo's NOEXEC tag stops the command executing another program at all, which
closes it without depending on that reasoning. It works by LD_PRELOAD, so it
applies to dynamically linked binaries; journalctl is one.
On a stock Raspberry Pi image none of this is reachable, because
/etc/sudoers.d/010_pi-nopasswd already grants the default user
`ALL=(ALL) NOPASSWD: ALL`. It matters on a hardened install, or where the
service runs as a user without that blanket rule.
"""
import re
from pathlib import Path
import pytest
ROOT = Path(__file__).resolve().parent.parent
INSTALLERS = (
ROOT / "first_time_install.sh",
ROOT / "scripts" / "install" / "configure_wifi_permissions.sh",
)
#: Commands that will start another program of their own accord -- a pager, an
#: editor, a shell -- and so must not be granted the ability to do so.
SPAWNS_A_PROGRAM = ("journalctl", "systemctl", "less", "more", "man", "git")
def _grant_lines():
lines = []
for installer in INSTALLERS:
if not installer.is_file():
continue
for line in installer.read_text(encoding="utf-8", errors="replace").splitlines():
stripped = line.strip()
if "NOPASSWD" in stripped and not stripped.startswith("#"):
lines.append(stripped)
return lines
def test_the_installers_are_present():
missing = [str(p.relative_to(ROOT)) for p in INSTALLERS if not p.is_file()]
assert not missing, f"installer(s) missing: {missing}"
def test_wildcard_pager_grants_carry_noexec():
offenders = []
for rule in _grant_lines():
command = rule.split("NOPASSWD", 1)[1]
if not command.rstrip().endswith("*"):
continue
tool = command.replace("_PATH", "").replace("$", "").lower()
for name in SPAWNS_A_PROGRAM:
if re.search(rf"(^|/|\s){name}(\s|$)", tool):
if "NOEXEC" not in rule:
offenders.append(rule)
break
assert not offenders, (
"wildcard grant to a command that can start a pager or shell, without "
"NOEXEC:\n " + "\n ".join(offenders))
def test_journalctl_is_granted_at_all():
"""Guard against 'fixing' the above by deleting the rules."""
text = "\n".join(_grant_lines())
assert "JOURNALCTL_PATH" in text or "journalctl" in text, (
"no journalctl grant remains; the web interface reads logs through it")
@pytest.mark.parametrize("unit", ["ledmatrix.service", "ledmatrix"])
def test_each_journalctl_rule_is_tagged(unit):
matching = [r for r in _grant_lines()
if "JOURNALCTL_PATH" in r and f"-u {unit} " in r]
assert matching, f"no journalctl rule for -u {unit}"
untagged = [r for r in matching if "NOEXEC" not in r]
assert not untagged, f"untagged journalctl rule(s): {untagged}"
-63
View File
@@ -1,63 +0,0 @@
"""The Vegas content path must trace at DEBUG, not INFO.
plugin_adapter narrates every step of acquiring content from every plugin --
"Has get_vegas_content", "Native: calling get_vegas_content()", "Native content
returned None", "Has scroll_helper", the per-item sizes -- and it does that for
each plugin on each cycle.
Measured on a live rig: 13,408 log lines an hour, of which 13,366 were INFO and
35 were WARNING. plugin_adapter alone produced 2,457 of them. That is ~223
lines a minute of string formatting on a Pi that is also driving the panel, all
of it written through journald to the SD card, and it buries the 35 lines that
actually indicate a problem.
Nothing is lost by moving it to DEBUG: the 19 warning/error/exception calls in
the module are untouched, so real failures still surface at their own level.
One INFO call is deliberate and stays -- the padding-strip message chooses its
level at runtime (`logger.warning if (left and right) else logger.info`) and
test_vegas_plugin_adapter.py pins it.
"""
import ast
from pathlib import Path
import pytest
ADAPTER = (Path(__file__).resolve().parent.parent / "src" / "vegas_mode"
/ "plugin_adapter.py")
def _info_calls(path):
"""Direct logger.info(...) call sites in a module."""
tree = ast.parse(path.read_text(encoding="utf-8"))
found = []
for node in ast.walk(tree):
if (isinstance(node, ast.Call)
and isinstance(node.func, ast.Attribute)
and node.func.attr == "info"
and getattr(node.func.value, "id", None) == "logger"):
found.append(node.lineno)
return found
def test_the_content_path_does_not_trace_at_info():
calls = _info_calls(ADAPTER)
assert not calls, (
"plugin_adapter should trace at DEBUG; found logger.info at lines "
f"{calls}. This path runs per plugin per cycle and its output goes to "
"the SD card via journald."
)
def test_real_failures_still_have_a_level_of_their_own():
"""Demoting the trace must not have swept up the error reporting."""
source = ADAPTER.read_text(encoding="utf-8")
loud = sum(source.count(f"logger.{level}(")
for level in ("warning", "error", "exception"))
assert loud >= 15, f"only {loud} warning/error/exception calls remain"
def test_the_deliberate_runtime_chosen_level_survives():
"""The padding-strip message picks its level at runtime; leave it alone."""
source = ADAPTER.read_text(encoding="utf-8")
assert "logger.warning if (left and right) else logger.info" in source