security(media): anchor sanitizeMimeType regex to reject malformed input

bluesky6868 · bluesky6868 · commit a6cba758561c · 2026-04-18T00:32:16.000-07:00
diff --git a/src/media-understanding/apply.test.ts b/src/media-understanding/apply.test.ts
@@ -6,6 +6,7 @@ import type { MsgContext } from "../auto-reply/templating.js";
 import type { OpenClawConfig } from "../config/types.js";
 import { resolvePreferredOpenClawTmpDir } from "../infra/tmp-openclaw-dir.js";
 import { withEnvAsync } from "../test-utils/env.js";
+import { sanitizeMimeType } from "./apply.js";
 import { createSafeAudioFixtureBuffer } from "./runner.test-utils.js";
 import type { MediaUnderstandingProvider } from "./types.js";
 
@@ -1419,3 +1420,41 @@ describe("applyMediaUnderstanding", () => {
     expect(ctx.Body).toContain("vendor-json");
   });
 });
+
+describe("sanitizeMimeType", () => {
+  it("accepts a plain MIME type", () => {
+    expect(sanitizeMimeType("image/png")).toBe("image/png");
+    expect(sanitizeMimeType("application/vnd.api+json")).toBe("application/vnd.api+json");
+  });
+
+  it("strips standard parameters", () => {
+    expect(sanitizeMimeType("text/plain; charset=utf-8")).toBe("text/plain");
+    expect(sanitizeMimeType("text/csv;charset=UTF-8")).toBe("text/csv");
+  });
+
+  it("lowercases mixed-case input", () => {
+    expect(sanitizeMimeType("Image/PNG")).toBe("image/png");
+  });
+
+  it("returns undefined for empty or missing input", () => {
+    expect(sanitizeMimeType(undefined)).toBeUndefined();
+    expect(sanitizeMimeType("")).toBeUndefined();
+    expect(sanitizeMimeType("   ")).toBeUndefined();
+  });
+
+  it("rejects malformed input with trailing junk instead of truncating", () => {
+    expect(sanitizeMimeType("image/png junk")).toBeUndefined();
+    expect(sanitizeMimeType("image/png\nextra")).toBeUndefined();
+  });
+
+  it("rejects path-like inputs that previously captured an allowlisted prefix", () => {
+    expect(sanitizeMimeType("image/png/../etc/passwd")).toBeUndefined();
+    expect(sanitizeMimeType("image/png/evil")).toBeUndefined();
+  });
+
+  it("rejects inputs without a type/subtype separator", () => {
+    expect(sanitizeMimeType("imagepng")).toBeUndefined();
+    expect(sanitizeMimeType("/png")).toBeUndefined();
+    expect(sanitizeMimeType("image/")).toBeUndefined();
+  });
+});
diff --git a/src/media-understanding/apply.ts b/src/media-understanding/apply.ts
@@ -74,12 +74,15 @@ const TEXT_EXT_MIME = new Map<string, string>([
   [".xml", "application/xml"],
 ]);
 
-function sanitizeMimeType(value?: string): string | undefined {
+// End-anchored so malformed input ("image/png junk", "image/png..etc")
+// returns undefined instead of silently truncating to a prefix that could
+// then pass the downstream allowlist check.
+export function sanitizeMimeType(value?: string): string | undefined {
   const trimmed = normalizeOptionalLowercaseString(value);
   if (!trimmed) {
     return undefined;
   }
-  const match = trimmed.match(/^([a-z0-9!#$&^_.+-]+\/[a-z0-9!#$&^_.+-]+)/);
+  const match = trimmed.match(/^([a-z0-9!#$&^_.+-]+\/[a-z0-9!#$&^_.+-]+)(?:;.*)?$/);
   return match?.[1];
 }
 
