From d7b63d2c5c3dcd278adb798c983f47f398b322e6 Mon Sep 17 00:00:00 2001
From: Martijn Coenen <maco@google.com>
Date: Thu, 22 Jul 2021 03:24:28 +0200
Subject: [PATCH] Fix makeUniqueWithTrailingData.

And do some additional checking on the generated verity digest size.

Bug: 194334498
Test: TH
Change-Id: If2ae3edc5427b4315d4be63663ab3ac4006f91e8
---
 ondevice-signing/VerityUtils.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ondevice-signing/VerityUtils.cpp b/ondevice-signing/VerityUtils.cpp
index e58de686..2beb7ebb 100644
--- a/ondevice-signing/VerityUtils.cpp
+++ b/ondevice-signing/VerityUtils.cpp
@@ -83,7 +83,12 @@ Result<std::vector<uint8_t>> createDigest(int fd) {
     if (ret < 0) {
         return ErrnoError() << "Failed to compute fs-verity digest";
     }
-    std::vector<uint8_t> digestVector(&digest->digest[0], &digest->digest[32]);
+    int expected_digest_size = libfsverity_get_digest_size(FS_VERITY_HASH_ALG_SHA256);
+    if (digest->digest_size != expected_digest_size) {
+        return Error() << "Digest does not have expected size: " << expected_digest_size
+                       << " actual: " << digest->digest_size;
+    }
+    std::vector<uint8_t> digestVector(&digest->digest[0], &digest->digest[expected_digest_size]);
     free(digest);
     return digestVector;
 }
@@ -111,7 +116,7 @@ template <typename T> using trailing_unique_ptr = std::unique_ptr<T, DeleteAsPOD
 
 template <typename T>
 static trailing_unique_ptr<T> makeUniqueWithTrailingData(size_t trailing_data_size) {
-    uint8_t* memory = new uint8_t[sizeof(T*) + trailing_data_size];
+    uint8_t* memory = new uint8_t[sizeof(T) + trailing_data_size];
     T* ptr = new (memory) T;
     return trailing_unique_ptr<T>{ptr};
 }