Block file:// navigation to executables in preview pane#356
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Addresses CVE-2019-12138 (directory traversal to arbitrary program execution) and CVE-2019-12173 (RCE via file:// URI to .app bundles, auto-clicked via JavaScript). Adds MPURLSecurityPolicy utility class with two guards: - isExecutableOrAppBundleAtURL: detects executables/bundles via UTI conformance (CoreServices) with POSIX executable bit fallback - url:isWithinScopeOfBaseURL: checks if a target URL is within the document's directory tree after resolving symlinks and path traversal Guards applied at two call sites in MPDocument.m: - decidePolicyForNavigationAction: blocks JS-triggered file:// navigations outside document scope or to executables - openOrCreateFileForUrl: blocks user-clicked links to executables with a warning alert Related to #351
URLByResolvingSymlinksInPath uses realpath() internally, which fails when the final path component doesn't exist — leaving intermediate symlinks unresolved. Resolve the parent directory separately so that symlink escapes like docs/evil-link/payload (where evil-link points outside scope) are caught even when payload doesn't exist on disk. Related to #351
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Code Coverage ReportCurrent Coverage: 57.52% Coverage Details (Summary) |
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Summary
MPURLSecurityPolicyutility class with UTI-based detection of executables/bundles and symlink-aware scope checkingdecidePolicyForNavigationAction:to block JS-triggeredfile://navigations outside document scope or to executablesopenOrCreateFileForUrl:to block user-clicked links to executables with a warning alertRelated Issue
Related to #351
Manual Testing Plan
<a href="file:///Applications/Calculator.app">click</a>— clicking should show a "Blocked: Link target is an executable" alert<script>window.location='file:///Applications/Calculator.app'</script>— no app should launch, blocked silently with NSLogfile://links to.mdfiles in the same directory should continue to workhttps://links should continue to open in the default browserDesign Notes
NSWorkspace typeOfFile:+UTTypeConformsTo()against six dangerous UTI types, with POSIX executable bit fallback for scripts without registered UTIsrealpath()(used byURLByResolvingSymlinksInPath) fails when the final component doesn't existfile://links intentionally skip the scope check — only executables are blocked. Opening local documents from Markdown links is a legitimate use case.