Fix flaky corrupted padding tests
It's possible that corrupted ciphertext decrypts just fine. e.g. the
output ends with "0x01".
However, the chances of this happening are relatively low
(roughly 1/256). Corrupt the ciphertext up to 8 times, ensuring that
the likelihood of multiple successful decryptions is so miniscule that
it's effectively impossible.
Test: Ran *PaddingCorrupted tests 50000 times
Change-Id: If40ecd7817819921c020ea9b86ada18c4c77ea55
diff --git a/security/keymint/aidl/vts/functional/KeyMintTest.cpp b/security/keymint/aidl/vts/functional/KeyMintTest.cpp
index d41d270..caac346 100644
--- a/security/keymint/aidl/vts/functional/KeyMintTest.cpp
+++ b/security/keymint/aidl/vts/functional/KeyMintTest.cpp
@@ -71,6 +71,12 @@
bool check_patchLevels = false;
+// The maximum number of times we'll attempt to verify that corruption
+// of an ecrypted blob results in an error. Retries are necessary as there
+// is a small (roughly 1/256) chance that corrupting ciphertext still results
+// in valid PKCS7 padding.
+constexpr size_t kMaxPaddingCorruptionRetries = 8;
+
template <TagType tag_type, Tag tag, typename ValueT>
bool contains(const vector<KeyParameter>& set, TypedTag<tag_type, tag> ttag,
ValueT expected_value) {
@@ -4376,11 +4382,22 @@
string ciphertext = EncryptMessage(message, params);
EXPECT_EQ(16U, ciphertext.size());
EXPECT_NE(ciphertext, message);
- ++ciphertext[ciphertext.size() / 2];
- EXPECT_EQ(ErrorCode::OK, Begin(KeyPurpose::DECRYPT, params));
- string plaintext;
- EXPECT_EQ(ErrorCode::INVALID_INPUT_LENGTH, Finish(message, &plaintext));
+ for (size_t i = 0; i < kMaxPaddingCorruptionRetries; ++i) {
+ ++ciphertext[ciphertext.size() / 2];
+
+ EXPECT_EQ(ErrorCode::OK, Begin(KeyPurpose::DECRYPT, params));
+ string plaintext;
+ ErrorCode error = Finish(message, &plaintext);
+ if (error == ErrorCode::INVALID_INPUT_LENGTH) {
+ // This is the expected error, we can exit the test now.
+ return;
+ } else {
+ // Very small chance we got valid decryption, so try again.
+ ASSERT_EQ(error, ErrorCode::OK);
+ }
+ }
+ FAIL() << "Corrupt ciphertext should have failed to decrypt by now.";
}
vector<uint8_t> CopyIv(const AuthorizationSet& set) {
@@ -5343,15 +5360,27 @@
string ciphertext = EncryptMessage(message, BlockMode::ECB, PaddingMode::PKCS7);
EXPECT_EQ(8U, ciphertext.size());
EXPECT_NE(ciphertext, message);
- ++ciphertext[ciphertext.size() / 2];
AuthorizationSetBuilder begin_params;
begin_params.push_back(TAG_BLOCK_MODE, BlockMode::ECB);
begin_params.push_back(TAG_PADDING, PaddingMode::PKCS7);
- EXPECT_EQ(ErrorCode::OK, Begin(KeyPurpose::DECRYPT, begin_params));
- string plaintext;
- EXPECT_EQ(ErrorCode::OK, Update(ciphertext, &plaintext));
- EXPECT_EQ(ErrorCode::INVALID_ARGUMENT, Finish(&plaintext));
+
+ for (size_t i = 0; i < kMaxPaddingCorruptionRetries; ++i) {
+ ++ciphertext[ciphertext.size() / 2];
+
+ EXPECT_EQ(ErrorCode::OK, Begin(KeyPurpose::DECRYPT, begin_params));
+ string plaintext;
+ EXPECT_EQ(ErrorCode::OK, Update(ciphertext, &plaintext));
+ ErrorCode error = Finish(&plaintext);
+ if (error == ErrorCode::INVALID_ARGUMENT) {
+ // This is the expected error, we can exit the test now.
+ return;
+ } else {
+ // Very small chance we got valid decryption, so try again.
+ ASSERT_EQ(error, ErrorCode::OK);
+ }
+ }
+ FAIL() << "Corrupt ciphertext should have failed to decrypt by now.";
}
struct TripleDesTestVector {
@@ -5679,16 +5708,27 @@
string ciphertext = EncryptMessage(message, BlockMode::CBC, PaddingMode::PKCS7, &iv);
EXPECT_EQ(8U, ciphertext.size());
EXPECT_NE(ciphertext, message);
- ++ciphertext[ciphertext.size() / 2];
auto begin_params = AuthorizationSetBuilder()
.BlockMode(BlockMode::CBC)
.Padding(PaddingMode::PKCS7)
.Authorization(TAG_NONCE, iv);
- EXPECT_EQ(ErrorCode::OK, Begin(KeyPurpose::DECRYPT, begin_params));
- string plaintext;
- EXPECT_EQ(ErrorCode::OK, Update(ciphertext, &plaintext));
- EXPECT_EQ(ErrorCode::INVALID_ARGUMENT, Finish(&plaintext));
+
+ for (size_t i = 0; i < kMaxPaddingCorruptionRetries; ++i) {
+ ++ciphertext[ciphertext.size() / 2];
+ EXPECT_EQ(ErrorCode::OK, Begin(KeyPurpose::DECRYPT, begin_params));
+ string plaintext;
+ EXPECT_EQ(ErrorCode::OK, Update(ciphertext, &plaintext));
+ ErrorCode error = Finish(&plaintext);
+ if (error == ErrorCode::INVALID_ARGUMENT) {
+ // This is the expected error, we can exit the test now.
+ return;
+ } else {
+ // Very small chance we got valid decryption, so try again.
+ ASSERT_EQ(error, ErrorCode::OK);
+ }
+ }
+ FAIL() << "Corrupt ciphertext should have failed to decrypt by now.";
}
/*