From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: kumarashishg Date: Mon, 17 Jul 2023 12:01:18 +0000 Subject: [PATCH] Resolve custom printer icon boundary exploit. Because Settings grants the INTERACT_ACROSS_USERS_FULL permission, an exploit is possible where the third party print plugin service can pass other's User Icon URI. This CL provides a lightweight solution for parsing the image URI to detect profile exploitation. Bug: 281525042 Test: Build and flash the code. Try to reproduce the issue with mentioned steps in the bug (cherry picked from https://googleplex-android-review.googlesource.com/q/commit:0e0693ca9cb408d0dc82f6c6b3feb453fc8ddd83) Merged-In: Iaaa6fe2a627a265c4d1d7b843a033a132e1fe2ce Change-Id: Iaaa6fe2a627a265c4d1d7b843a033a132e1fe2ce --- .../server/print/PrintManagerService.java | 34 ++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/services/print/java/com/android/server/print/PrintManagerService.java b/services/print/java/com/android/server/print/PrintManagerService.java index dc55179bdc9e..101a2b41addb 100644 --- a/services/print/java/com/android/server/print/PrintManagerService.java +++ b/services/print/java/com/android/server/print/PrintManagerService.java @@ -251,12 +251,44 @@ public final class PrintManagerService extends SystemService { } final long identity = Binder.clearCallingIdentity(); try { - return userState.getCustomPrinterIcon(printerId); + Icon icon = userState.getCustomPrinterIcon(printerId); + return validateIconUserBoundary(icon); } finally { Binder.restoreCallingIdentity(identity); } } + /** + * Validates the custom printer icon to see if it's not in the calling user space. + * If the condition is not met, return null. Otherwise, return the original icon. + * + * @param icon + * @return icon (validated) + */ + private Icon validateIconUserBoundary(Icon icon) { + // Refer to Icon#getUriString for context. The URI string is invalid for icons of + // incompatible types. + if (icon != null && (icon.getType() == Icon.TYPE_URI)) { + String encodedUser = icon.getUri().getEncodedUserInfo(); + + // If there is no encoded user, the URI is calling into the calling user space + if (encodedUser != null) { + int userId = Integer.parseInt(encodedUser); + // resolve encoded user + final int resolvedUserId = resolveCallingUserEnforcingPermissions(userId); + + synchronized (mLock) { + // Only the current group members can get the printer icons. + if (resolveCallingProfileParentLocked(resolvedUserId) + != getCurrentUserId()) { + return null; + } + } + } + } + return icon; + } + @Override public void cancelPrintJob(PrintJobId printJobId, int appId, int userId) { if (printJobId == null) {