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fix: prevent TOCTOU race condition on issue/PR body edits (#710)

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Add trigger-time validation for issue/PR body content to prevent attackers
from exploiting a race condition where they edit the body between when an
authorized user triggers @claude and when Claude processes the request.

The existing filterCommentsToTriggerTime() already protected comments -
this extends the same pattern to the main issue/PR body via isBodySafeToUse().

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>
This commit is contained in:
Ashwin Bhat
2025-12-01 10:59:39 -05:00
committed by GitHub
parent 6d79044f1d
commit 6337623ebb
4 changed files with 304 additions and 5 deletions
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52
src/github/data/fetcher.ts
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@@ -107,6 +107,38 @@ export function filterReviewsToTriggerTime<
});
}
/**
* Checks if the issue/PR body was edited after the trigger time.
* This prevents a race condition where an attacker could edit the issue/PR body
* between when an authorized user triggered Claude and when Claude processes the request.
*
* @param contextData - The PR or issue data containing body and edit timestamps
* @param triggerTime - ISO timestamp of when the trigger event occurred
* @returns true if the body is safe to use, false if it was edited after trigger
*/
export function isBodySafeToUse(
contextData: { createdAt: string; updatedAt?: string; lastEditedAt?: string },
triggerTime: string | undefined,
): boolean {
// If no trigger time is available, we can't validate - allow the body
// This maintains backwards compatibility for triggers that don't have timestamps
if (!triggerTime) return true;
const triggerTimestamp = new Date(triggerTime).getTime();
// Check if the body was edited after the trigger
// Use lastEditedAt if available (more accurate for body edits), otherwise fall back to updatedAt
const lastEditTime = contextData.lastEditedAt || contextData.updatedAt;
if (lastEditTime) {
const lastEditTimestamp = new Date(lastEditTime).getTime();
if (lastEditTimestamp >= triggerTimestamp) {
return false;
}
}
return true;
}
type FetchDataParams = {
octokits: Octokits;
repository: string;
@@ -273,9 +305,13 @@ export async function fetchGitHubData({
body: c.body,
}));
// Add the main issue/PR body if it has content
const mainBody: CommentWithImages[] = contextData.body
? [
// Add the main issue/PR body if it has content and wasn't edited after trigger
// This prevents a TOCTOU race condition where an attacker could edit the body
// between when an authorized user triggered Claude and when Claude processes the request
let mainBody: CommentWithImages[] = [];
if (contextData.body) {
if (isBodySafeToUse(contextData, triggerTime)) {
mainBody = [
{
...(isPR
? {
@@ -289,8 +325,14 @@ export async function fetchGitHubData({
body: contextData.body,
}),
},
]
: [];
];
} else {
console.warn(
`Security: ${isPR ? "PR" : "Issue"} #${prNumber} body was edited after the trigger event. ` +
`Excluding body content to prevent potential injection attacks.`,
);
}
}
const allComments = [
...mainBody,