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:39f5737626ca644f41fda890c12518ce51875835)
Merged-In: Iaaa6fe2a627a265c4d1d7b843a033a132e1fe2ce
Change-Id: Iaaa6fe2a627a265c4d1d7b843a033a132e1fe2ce
diff --git a/services/print/java/com/android/server/print/PrintManagerService.java b/services/print/java/com/android/server/print/PrintManagerService.java
index 66524edf..1386bbf 100644
--- a/services/print/java/com/android/server/print/PrintManagerService.java
+++ b/services/print/java/com/android/server/print/PrintManagerService.java
@@ -254,12 +254,45 @@
}
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
+ || icon.getType() == Icon.TYPE_URI_ADAPTIVE_BITMAP)) {
+ 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) {