🛡️ Sentinel: [HIGH] Fix Local File Inclusion vulnerability#201
🛡️ Sentinel: [HIGH] Fix Local File Inclusion vulnerability#201sheepdestroyer wants to merge 2 commits intomasterfrom
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* Set setAllowFileAccess(false) in CacheableWebView to stop global LFI. * Safely proxy necessary offline `.mht` cache files using WebResourceResponse in AdBlockWebViewClient. * Add path traversal protections checking `..` and canonical paths bounded by the CacheDir. * Switch mLoadedUrls HashMap to ConcurrentHashMap to prevent crashes on background WebView intercept threads. Co-authored-by: sheepdestroyer <1377479+sheepdestroyer@users.noreply.github.com>
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Reviewer's GuideLocks down WebView file access to eliminate an LFI vector while preserving offline cache loading, and hardens WebView request interception against concurrency issues and documents the security fix. Sequence diagram for secure WebView file request handling and cache proxysequenceDiagram
actor UserContent
participant WebView
participant AdBlockWebViewClient
participant handleFileRequest
participant FileSystem
UserContent->>WebView: Load URL (may include file URL)
WebView->>AdBlockWebViewClient: shouldInterceptRequest(view, url)
AdBlockWebViewClient->>handleFileRequest: handleFileRequest(context, url)
alt Not file URL or disallowed path
handleFileRequest-->>AdBlockWebViewClient: null
alt AdBlock disabled
AdBlockWebViewClient->>WebView: super.shouldInterceptRequest(...)
WebView-->>UserContent: Network response
else AdBlock enabled
AdBlockWebViewClient->>AdBlockWebViewClient: Check mLoadedUrls (ConcurrentHashMap)
AdBlockWebViewClient->>WebView: Filtered WebResourceResponse or super
WebView-->>UserContent: Filtered response
end
else Valid cache .mht file URL
handleFileRequest->>FileSystem: Validate canonicalPath under cacheDir
FileSystem-->>handleFileRequest: FileInputStream for .mht
handleFileRequest-->>AdBlockWebViewClient: WebResourceResponse(application/x-mimearchive)
AdBlockWebViewClient-->>WebView: WebResourceResponse (offline cache)
WebView-->>UserContent: Offline cached content
end
Updated class diagram for AdBlockWebViewClient and CacheableWebViewclassDiagram
class AdBlockWebViewClient {
- boolean mAdBlockEnabled
- Map~String,Boolean~ mLoadedUrls
+ AdBlockWebViewClient(boolean adBlockEnabled)
- WebResourceResponse handleFileRequest(Context context, String url)
+ WebResourceResponse shouldInterceptRequest(WebView view, String url)
+ WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request)
}
class ConcurrentHashMap {
}
class CacheableWebView {
+ CacheableWebView(Context context)
- void init()
- void enableCache()
}
class WebSettings {
+ void setAllowFileAccess(boolean allow)
}
class WebView {
+ WebSettings getSettings()
}
AdBlockWebViewClient ..> ConcurrentHashMap : uses for mLoadedUrls
CacheableWebView ..> WebView : extends
CacheableWebView ..> WebSettings : uses
WebView ..> WebSettings : returns
Flow diagram for secure file URL handling in AdBlockWebViewClientflowchart TD
A[Incoming WebView request URL] --> B{URL starts with file://?}
B -- No --> Z[Return null and continue normal flow]
B -- Yes --> C{Starts with file:///android_asset/ or file:///android_res/?}
C -- Yes --> Z
C -- No --> D[Parse URL to path via Uri.getPath]
D --> E{Path is null or contains ..?}
E -- Yes --> Z
E -- No --> F[Create File from path]
F --> G[Get cacheDir from context]
G --> H{file.canonicalPath startsWith cacheDir.canonicalPath + separator?}
H -- No --> Z
H -- Yes --> I{file exists and name endsWith .mht?}
I -- No --> Z
I -- Yes --> J[Create FileInputStream for file]
J --> K["Return WebResourceResponse(application/x-mimearchive, UTF-8, stream)"]
Z[Return null so AdBlock or default handling runs]-->L[AdBlock logic or super.shouldInterceptRequest]
File-Level Changes
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Security Reliability Complexity Hygiene |
Code Review Summary
| Analyzer | Status | Updated (UTC) | Details |
|---|---|---|---|
| Kotlin |  |
Apr 30, 2026 3:40p.m. | Review ↗ |
| Java | |
Apr 30, 2026 3:40p.m. | Review ↗ |
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Hey - I've found 1 issue, and left some high level feedback:
- In
handleFileRequest, the empty catch block silently swallows all exceptions; consider at least logging or narrowing the exception type so unexpected failures are visible during debugging. - The canonical path check
startsWith(cacheDir.getCanonicalPath() + File.separator)will fail if the file is exactly the cache directory; consider using a more robust directory containment check (e.g., appending a separator to both paths or using a dedicated helper) to avoid edge-case bypasses or false negatives. - To reduce work in
handleFileRequest, you can avoid creating multiple strings and parsing twice by checking the scheme viaUri.parse(url).getScheme()before callingtoLowerCaseor other more expensive operations.
Prompt for AI Agents
Please address the comments from this code review:
## Overall Comments
- In `handleFileRequest`, the empty catch block silently swallows all exceptions; consider at least logging or narrowing the exception type so unexpected failures are visible during debugging.
- The canonical path check `startsWith(cacheDir.getCanonicalPath() + File.separator)` will fail if the file is exactly the cache directory; consider using a more robust directory containment check (e.g., appending a separator to both paths or using a dedicated helper) to avoid edge-case bypasses or false negatives.
- To reduce work in `handleFileRequest`, you can avoid creating multiple strings and parsing twice by checking the scheme via `Uri.parse(url).getScheme()` before calling `toLowerCase` or other more expensive operations.
## Individual Comments
### Comment 1
<location path="app/src/main/java/io/github/sheepdestroyer/materialisheep/widget/AdBlockWebViewClient.java" line_range="66" />
<code_context>
+ if (file.exists() && file.getName().endsWith(".mht")) {
+ return new WebResourceResponse("application/x-mimearchive", "UTF-8", new FileInputStream(file));
+ }
+ } catch (Exception e) {}
+ return null;
+ }
</code_context>
<issue_to_address>
**issue (bug_risk):** Avoid silently swallowing all Exceptions in handleFileRequest.
Catching and ignoring a broad Exception here makes failures in file handling invisible and hard to diagnose, and can hide issues like I/O or security-related path errors. Please either log the exception (or specific ones like IOException/SecurityException) or narrow the catch to only the expected exception types and let others propagate.
</issue_to_address>Help me be more useful! Please click 👍 or 👎 on each comment and I'll use the feedback to improve your reviews.
| if (file.exists() && file.getName().endsWith(".mht")) { | ||
| return new WebResourceResponse("application/x-mimearchive", "UTF-8", new FileInputStream(file)); | ||
| } | ||
| } catch (Exception e) {} |
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issue (bug_risk): Avoid silently swallowing all Exceptions in handleFileRequest.
Catching and ignoring a broad Exception here makes failures in file handling invisible and hard to diagnose, and can hide issues like I/O or security-related path errors. Please either log the exception (or specific ones like IOException/SecurityException) or narrow the catch to only the expected exception types and let others propagate.
![gemini-code-assist[bot]](https://avatars.githubusercontent.com/in/956858?s=60&v=4){kind=small}
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Code Review
This pull request addresses a Local File Inclusion (LFI) vulnerability by disabling broad file access in CacheableWebView and implementing a secure proxy for local cache access within AdBlockWebViewClient. It also updates the URL tracking map to a ConcurrentHashMap to handle background thread access. The review identifies that disabling file access might break default offline functionality because the proxy logic is not integrated into the default WebViewClient. Furthermore, feedback suggests resolving a race condition in the URL cache map, optimizing handleFileRequest to accept Uri objects directly, and eliminating redundant URI parsing.
| webSettings.setAllowFileAccess(false); | ||
| setCacheModeInternal(); | ||
| } | ||
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Disabling file access here correctly mitigates the LFI vulnerability but breaks the core offline functionality of CacheableWebView. This class generates file:// URLs for cached content (line 121), which will now be blocked by the WebView. While interception logic was added to AdBlockWebViewClient, CacheableWebView initializes itself with a default WebViewClient in its init() method (line 89), which does not perform this interception. This means CacheableWebView will fail to load offline archives by default unless the user manually configures it with AdBlockWebViewClient. The proxy logic should be integrated into CacheableWebView or its default client to maintain self-encapsulation.
| public AdBlockWebViewClient(boolean adBlockEnabled) { | ||
| mAdBlockEnabled = adBlockEnabled; | ||
| } | ||
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While switching to ConcurrentHashMap prevents ConcurrentModificationException crashes, the logic that accesses this map in shouldInterceptRequest (lines 78-83 and 97-102) still contains a race condition due to the "check-then-act" pattern. Multiple threads could simultaneously find a URL missing and perform redundant AdBlocker.isAd(url) checks. Consider using computeIfAbsent for an atomic operation if the project targets API 24+, or at least use get() followed by a null check to reduce lookups.
| || lowerUrl.startsWith("file:///android_res/")) return null; | ||
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| try { | ||
| String decodedPath = Uri.parse(url).getPath(); | ||
| if (decodedPath == null || decodedPath.contains("..")) return null; | ||
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| File file = new File(decodedPath); | ||
| File cacheDir = context.getApplicationContext().getCacheDir(); | ||
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| if (!file.getCanonicalPath().startsWith(cacheDir.getCanonicalPath() + File.separator)) { | ||
| return null; | ||
| } | ||
| if (file.exists() && file.getName().endsWith(".mht")) { | ||
| return new WebResourceResponse( | ||
| "application/x-mimearchive", "UTF-8", new FileInputStream(file)); | ||
| } | ||
| } catch (Exception e) { | ||
| } | ||
| return null; | ||
| } | ||
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| @Override | ||
| public final WebResourceResponse shouldInterceptRequest(WebView view, String url) { | ||
| if (!mAdBlockEnabled) { | ||
| return super.shouldInterceptRequest(view, url); | ||
| } | ||
| boolean ad; | ||
| if (!mLoadedUrls.containsKey(url)) { | ||
| ad = AdBlocker.isAd(url); | ||
| mLoadedUrls.put(url, ad); | ||
| } else { | ||
| ad = mLoadedUrls.get(url); | ||
| } | ||
| return ad ? AdBlocker.createEmptyResource() : super.shouldInterceptRequest(view, url); | ||
| @Override |
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The handleFileRequest method can be optimized by accepting a Uri instead of a String. This avoids redundant parsing in shouldInterceptRequest(WebView, WebResourceRequest) where a Uri is already available. Additionally, using uri.getScheme() and uri.getPath() is more efficient than string-based prefix checks.
private WebResourceResponse handleFileRequest(Context context, Uri uri) {
if (uri == null || !"file".equalsIgnoreCase(uri.getScheme())) return null;
try {
String path = uri.getPath();
if (path == null || path.contains("..")) return null;
if (path.startsWith("/android_asset/") || path.startsWith("/android_res/")) return null;
File file = new File(path);
File cacheDir = context.getApplicationContext().getCacheDir();
if (!file.getCanonicalPath().startsWith(cacheDir.getCanonicalPath() + File.separator)) {
return null;
}
if (file.exists() && file.getName().endsWith(".mht")) {
return new WebResourceResponse("application/x-mimearchive", "UTF-8", new FileInputStream(file));
}
} catch (Exception e) {}
return null;
}| public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) { | ||
| WebResourceResponse fileRes = handleFileRequest(view.getContext(), request.getUrl().toString()); | ||
| if (fileRes != null) return fileRes; | ||
| if (!mAdBlockEnabled) { |
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Redundant URI parsing. request.getUrl() already returns a Uri object. Converting it to a String only for handleFileRequest to parse it back is inefficient.
| if (!mAdBlockEnabled) { | |
| WebResourceResponse fileRes = handleFileRequest(view.getContext(), request.getUrl()); |
Up to standards ✅🟢 Issues
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| Metric | Results |
|---|---|
| Complexity | 13 |
| Duplication | 0 |
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Code Review
This pull request mitigates a Local File Inclusion (LFI) vulnerability by disabling setAllowFileAccess and introducing a secure file request handler in AdBlockWebViewClient. It also improves thread safety by using ConcurrentHashMap. Review feedback points out a regression where CacheableWebView instances using the default client will fail to load cached content, and suggests using more specific exception handling instead of a broad catch block.
| webSettings.setAllowFileAccess(false); | ||
| setCacheModeInternal(); | ||
| } | ||
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Disabling setAllowFileAccess is the correct security fix for the LFI vulnerability. However, this change introduces a regression in the offline caching functionality of this class. When the device is offline, getCacheableUrl (line 121) returns a file:// URL, which will now be blocked by the WebView. While this PR adds a secure proxy in AdBlockWebViewClient, CacheableWebView initializes itself with a standard WebViewClient in its init() method (line 89), which lacks this proxying logic. This means any instance of CacheableWebView that does not have an AdBlockWebViewClient explicitly set will fail to load cached content. Consider ensuring that CacheableWebView uses a client that implements the handleFileRequest logic by default.
| } catch (Exception e) { | ||
| } | ||
| return null; | ||
| } |
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Swallowing all exceptions with a broad catch (Exception e) block is generally discouraged. While returning null is a safe fallback here to allow the WebView to proceed with its default behavior, it is better to catch specific expected exceptions (e.g., IOException, SecurityException) to avoid masking unexpected programming errors or runtime issues.
1 participant
🚨 Severity: HIGH
💡 Vulnerability: A Local File Inclusion (LFI) vulnerability existed because
CacheableWebViewexplicitly enabledsetAllowFileAccess(true). This setting allowed potentially malicious web content loaded into the WebView to read arbitrary files from the user's local filesystem. Furthermore, intercepting requests using standard HashMaps on background threads exposed the app toConcurrentModificationExceptioncrashes.🎯 Impact: Attackers serving malicious JavaScript could read local files (shared prefs, tokens, databases) on the Android device. Concurrently, the thread-safety issue could cause the app to crash during rapid resource loads.
🔧 Fix:
getSettings().setAllowFileAccess(false)inCacheableWebView..mhtfiles from the cache directory) withinAdBlockWebViewClient.shouldInterceptRequest. The proxy uses explicit path boundary checks (getCanonicalPath()against the cache directory) and prevents path traversal (..) to safely serve only specific files viaWebResourceResponse.HashMapwithConcurrentHashMapinAdBlockWebViewClientto prevent concurrent modification exceptions.✅ Verification: Verified that tests (
./gradlew clean lint testDebugUnitTest --no-daemon) pass. Offline caching remains functional without exposing the wider filesystem.PR created automatically by Jules for task 8017503403696783685 started by @sheepdestroyer
Summary by Sourcery
Harden WebView file access and offline caching to prevent local file inclusion and concurrency issues.
Bug Fixes:
Documentation: