From 73e2936fc25a0098d59205457bf48c721492f429 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Fri, 3 Mar 2023 19:39:24 +0000
Subject: [PATCH] Avoid error message when destroying key w/o secdiscardable
 file

Since commit 08f4bdfe9836 ("Don't use a secdiscardable file for keys
encrypted by SP") (https://r.android.com/2242561), some keys don't use a
secdiscardable file.  Currently if such a key is destroyed, an ERROR
message like the following is logged:

    E secdiscard: Secure discard open failed for: /data/misc/vold/user_keys/ce/14/current/secdiscardable

This case is expected, so it should not be an ERROR.  Fix this by only
passing the secdiscardable file to the secdiscard program if it exists.

Bug: 232452368
Change-Id: I490289dfdaf0db6c3f4fb507509095e0033e2f69
---
 KeyStorage.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/KeyStorage.cpp b/KeyStorage.cpp
index 55c1709..837bb1a 100644
--- a/KeyStorage.cpp
+++ b/KeyStorage.cpp
@@ -660,8 +660,11 @@ bool destroyKey(const std::string& dir) {
         kSecdiscardPath,
         "--",
         dir + "/" + kFn_encrypted_key,
-        dir + "/" + kFn_secdiscardable,
     };
+    auto secdiscardable = dir + "/" + kFn_secdiscardable;
+    if (pathExists(secdiscardable)) {
+        secdiscard_cmd.push_back(secdiscardable);
+    }
     // Try each thing, even if previous things failed.
 
     for (auto& fn : {kFn_keymaster_key_blob, kFn_keymaster_key_blob_upgraded}) {