fix: prevent appconfig path traversal to RCE via public_/remote_ keys (OC10-146) - #41803
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fix: prevent appconfig path traversal to RCE via public_/remote_ keys (OC10-146)#41803oc-tmueller wants to merge 1 commit into
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… (OC10-146) An authenticated admin could set the core appconfig key `public_webdav` (or any `public_`/`remote_` key) to a path-traversal value and have it `require_once`'d by public.php on the next `GET /public.php/webdav`, achieving remote code execution. Two independent defects made this possible: 1. Sink: public.php included the stored handler path relative to the app directory with no traversal check, unlike remote.php which already rejects `../`. This is the essential, DB-independent gate: add the same guard so a traversal path can never be included. 2. Guard bypass: AppConfigController used a strict `$app === 'core'` compare to block admins from setting `public_`/`remote_` keys on core. A mangled app id such as `"core "` (trailing space) is not equal to `"core"` in PHP yet the database folds it back to the core row, defeating the guard. This is the same defeat mechanism as OC10-5 (`core%81` truncation). Normalize the app id (cleanAppId + trim + strtolower) before the check, in both the controller (getValue/setValue/deleteKey) and the legacy core/ajax/appconfig.php endpoint, and block deleting the whole core appconfig via deleteApp. Adds regression tests covering the mangled `core` spellings and the allowed near-misses. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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| app-id guard can no longer be bypassed by mangled spellings such as a trailing | ||
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| https://github.com/owncloud/core/pull/41802 |
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The PR number is off-by-one. The master PR #41804 has the correct numbers.
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@oc-tmueller you can decide if you update the PR number in the changelog entry.
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Summary
An authenticated admin could set the
coreappconfig keypublic_webdav(or anypublic_/remote_key) to a path-traversal value and have itrequire_once'd bypublic.phpon the nextGET /public.php/webdav, achieving remote code execution.Two independent defects made this possible; both are fixed here (defense in depth).
1. Sink —
public.phphad no traversal check (essential fix)public.phpincluded the stored handler path relative to the app directory with no traversal guard, unlikeremote.phpwhich already rejects../. Added the same guard so a traversal path can never be included — this is the DB- and endpoint-independent gate.2. Guard bypass — strict
$app === 'core'compareAppConfigControllerblocked admins from settingpublic_/remote_keys oncorewith a strict$app === 'core'compare. A mangled app id such as"core "(trailing space) is not equal to"core"in PHP, yet the database folds it back to thecorerow — defeating the guard. This is the same defeat mechanism as the earliercore%81truncation bypass. The app id is now normalized (cleanAppId+trim+strtolower) before the check, in:AppConfigController::getValue/setValue/deleteKeycore/ajax/appconfig.phpendpointdeleteAppnow refuses to wipe the wholecoreappconfig.Tests
Adds regression tests covering the mangled
corespellings ("core "," core","CORE","core/","core..") and allowed near-misses (encore, non-service keys oncore).Verified in the ownCloud CI toolchain (PHP 7.4, PHPUnit 9.6, sqlite): OK — 40 tests, 105 assertions. Reverting the guard to the strict compare makes 13 of the new cases fail, confirming they catch the bypass.
Resubmission of #41802, re-authored and SSH-signed under @oc-tmueller.