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

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>

src/github/api/queries/github.ts

@@ -13,6 +13,8 @@ export const PR_QUERY = `
         headRefName
         headRefOid
         createdAt
+        updatedAt
+        lastEditedAt
         additions
         deletions
         state
@@ -96,6 +98,8 @@ export const ISSUE_QUERY = `
           login
         }
         createdAt
+        updatedAt
+        lastEditedAt
         state
         comments(first: 100) {
           nodes {

src/github/data/fetcher.ts

@@ -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,

src/github/types.ts

@@ -58,6 +58,8 @@ export type GitHubPullRequest = {
   headRefName: string;
   headRefOid: string;
   createdAt: string;
+  updatedAt?: string;
+  lastEditedAt?: string;
   additions: number;
   deletions: number;
   state: string;
@@ -83,6 +85,8 @@ export type GitHubIssue = {
   body: string;
   author: GitHubAuthor;
   createdAt: string;
+  updatedAt?: string;
+  lastEditedAt?: string;
   state: string;
   comments: {
     nodes: GitHubComment[];

test/data-fetcher.test.ts

@@ -4,6 +4,7 @@ import {
   fetchGitHubData,
   filterCommentsToTriggerTime,
   filterReviewsToTriggerTime,
+  isBodySafeToUse,
 } from "../src/github/data/fetcher";
 import {
   createMockContext,
@@ -371,6 +372,139 @@ describe("filterReviewsToTriggerTime", () => {
   });
 });
 
+describe("isBodySafeToUse", () => {
+  const triggerTime = "2024-01-15T12:00:00Z";
+
+  const createMockContextData = (
+    createdAt: string,
+    updatedAt?: string,
+    lastEditedAt?: string,
+  ) => ({
+    createdAt,
+    updatedAt,
+    lastEditedAt,
+  });
+
+  describe("body edit time validation", () => {
+    it("should return true when body was never edited", () => {
+      const contextData = createMockContextData("2024-01-15T10:00:00Z");
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(true);
+    });
+
+    it("should return true when body was edited before trigger time", () => {
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T11:00:00Z",
+        "2024-01-15T11:30:00Z",
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(true);
+    });
+
+    it("should return false when body was edited after trigger time (using updatedAt)", () => {
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T13:00:00Z",
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(false);
+    });
+
+    it("should return false when body was edited after trigger time (using lastEditedAt)", () => {
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        undefined,
+        "2024-01-15T13:00:00Z",
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(false);
+    });
+
+    it("should return false when body was edited exactly at trigger time", () => {
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T12:00:00Z",
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(false);
+    });
+
+    it("should prioritize lastEditedAt over updatedAt", () => {
+      // updatedAt is after trigger, but lastEditedAt is before - should be safe
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T13:00:00Z", // updatedAt after trigger
+        "2024-01-15T11:00:00Z", // lastEditedAt before trigger
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(true);
+    });
+  });
+
+  describe("edge cases", () => {
+    it("should return true when no trigger time is provided (backward compatibility)", () => {
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T13:00:00Z", // Would normally fail
+        "2024-01-15T14:00:00Z", // Would normally fail
+      );
+      expect(isBodySafeToUse(contextData, undefined)).toBe(true);
+    });
+
+    it("should handle millisecond precision correctly", () => {
+      // Edit 1ms after trigger - should be unsafe
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T12:00:00.001Z",
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(false);
+    });
+
+    it("should handle edit 1ms before trigger - should be safe", () => {
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T11:59:59.999Z",
+      );
+      expect(isBodySafeToUse(contextData, triggerTime)).toBe(true);
+    });
+
+    it("should handle various ISO timestamp formats", () => {
+      const contextData1 = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T11:00:00Z",
+      );
+      const contextData2 = createMockContextData(
+        "2024-01-15T10:00:00+00:00",
+        "2024-01-15T11:00:00+00:00",
+      );
+      const contextData3 = createMockContextData(
+        "2024-01-15T10:00:00.000Z",
+        "2024-01-15T11:00:00.000Z",
+      );
+
+      expect(isBodySafeToUse(contextData1, triggerTime)).toBe(true);
+      expect(isBodySafeToUse(contextData2, triggerTime)).toBe(true);
+      expect(isBodySafeToUse(contextData3, triggerTime)).toBe(true);
+    });
+  });
+
+  describe("security scenarios", () => {
+    it("should detect race condition attack - body edited between trigger and processing", () => {
+      // Simulates: Owner triggers @claude at 12:00, attacker edits body at 12:00:30
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z", // Issue created
+        "2024-01-15T12:00:30Z", // Body edited after trigger
+      );
+      expect(isBodySafeToUse(contextData, "2024-01-15T12:00:00Z")).toBe(false);
+    });
+
+    it("should allow body that was stable at trigger time", () => {
+      // Body was last edited well before the trigger
+      const contextData = createMockContextData(
+        "2024-01-15T10:00:00Z",
+        "2024-01-15T10:30:00Z",
+        "2024-01-15T10:30:00Z",
+      );
+      expect(isBodySafeToUse(contextData, "2024-01-15T12:00:00Z")).toBe(true);
+    });
+  });
+});
+
 describe("fetchGitHubData integration with time filtering", () => {
   it("should filter comments based on trigger time when provided", async () => {
     const mockOctokits = {
@@ -696,4 +830,119 @@ describe("fetchGitHubData integration with time filtering", () => {
     // All three comments should be included as they're all before trigger time
     expect(result.comments.length).toBe(3);
   });
+
+  it("should exclude issue body when edited after trigger time (TOCTOU protection)", async () => {
+    const mockOctokits = {
+      graphql: jest.fn().mockResolvedValue({
+        repository: {
+          issue: {
+            number: 555,
+            title: "Test Issue",
+            body: "Malicious body edited after trigger",
+            author: { login: "attacker" },
+            createdAt: "2024-01-15T10:00:00Z",
+            updatedAt: "2024-01-15T12:30:00Z", // Edited after trigger
+            lastEditedAt: "2024-01-15T12:30:00Z", // Edited after trigger
+            comments: { nodes: [] },
+          },
+        },
+        user: { login: "trigger-user" },
+      }),
+      rest: jest.fn() as any,
+    };
+
+    const result = await fetchGitHubData({
+      octokits: mockOctokits as any,
+      repository: "test-owner/test-repo",
+      prNumber: "555",
+      isPR: false,
+      triggerUsername: "trigger-user",
+      triggerTime: "2024-01-15T12:00:00Z",
+    });
+
+    // The body should be excluded from image processing due to TOCTOU protection
+    // We can verify this by checking that issue_body is NOT in the imageUrlMap keys
+    const hasIssueBodyInMap = Array.from(result.imageUrlMap.keys()).some(
+      (key) => key.includes("issue_body"),
+    );
+    expect(hasIssueBodyInMap).toBe(false);
+  });
+
+  it("should include issue body when not edited after trigger time", async () => {
+    const mockOctokits = {
+      graphql: jest.fn().mockResolvedValue({
+        repository: {
+          issue: {
+            number: 666,
+            title: "Test Issue",
+            body: "Safe body not edited after trigger",
+            author: { login: "author" },
+            createdAt: "2024-01-15T10:00:00Z",
+            updatedAt: "2024-01-15T11:00:00Z", // Edited before trigger
+            lastEditedAt: "2024-01-15T11:00:00Z", // Edited before trigger
+            comments: { nodes: [] },
+          },
+        },
+        user: { login: "trigger-user" },
+      }),
+      rest: jest.fn() as any,
+    };
+
+    const result = await fetchGitHubData({
+      octokits: mockOctokits as any,
+      repository: "test-owner/test-repo",
+      prNumber: "666",
+      isPR: false,
+      triggerUsername: "trigger-user",
+      triggerTime: "2024-01-15T12:00:00Z",
+    });
+
+    // The contextData should still contain the body
+    expect(result.contextData.body).toBe("Safe body not edited after trigger");
+  });
+
+  it("should exclude PR body when edited after trigger time (TOCTOU protection)", async () => {
+    const mockOctokits = {
+      graphql: jest.fn().mockResolvedValue({
+        repository: {
+          pullRequest: {
+            number: 777,
+            title: "Test PR",
+            body: "Malicious PR body edited after trigger",
+            author: { login: "attacker" },
+            baseRefName: "main",
+            headRefName: "feature",
+            headRefOid: "abc123",
+            createdAt: "2024-01-15T10:00:00Z",
+            updatedAt: "2024-01-15T12:30:00Z", // Edited after trigger
+            lastEditedAt: "2024-01-15T12:30:00Z", // Edited after trigger
+            additions: 10,
+            deletions: 5,
+            state: "OPEN",
+            commits: { totalCount: 1, nodes: [] },
+            files: { nodes: [] },
+            comments: { nodes: [] },
+            reviews: { nodes: [] },
+          },
+        },
+        user: { login: "trigger-user" },
+      }),
+      rest: jest.fn() as any,
+    };
+
+    const result = await fetchGitHubData({
+      octokits: mockOctokits as any,
+      repository: "test-owner/test-repo",
+      prNumber: "777",
+      isPR: true,
+      triggerUsername: "trigger-user",
+      triggerTime: "2024-01-15T12:00:00Z",
+    });
+
+    // The body should be excluded from image processing due to TOCTOU protection
+    const hasPrBodyInMap = Array.from(result.imageUrlMap.keys()).some((key) =>
+      key.includes("pr_body"),
+    );
+    expect(hasPrBodyInMap).toBe(false);
+  });
 });