From 7c2b88b5b7fe8b4a661b3b67f6f3bc8e6bc381ce Mon Sep 17 00:00:00 2001
From: Gaurav Kashyap <quic_gaurkash@quicinc.com>
Date: Mon, 15 Jun 2020 13:58:39 -0700
Subject: VtsKernelEncryptionTest: fix wrapped key tests and test adding
 corrupted key

1. Correctly implement the derivation of raw secret when using
   wrapped keys. This is used to verify the key identifier and
   to derive the inode hash key for IV_INO_LBLK_32 (emmc_optimized)
   encryption policies.
2. Add a new test case (TestHwWrappedKeyCorruption) that fails
   when any byte of the key that is added is corrupted.

Test: VtsKernelEncryptionTest on device with HW wrapped keys
      supported.
Bug: 153730132

Change-Id: Id51f2dd514fed903783af4a442bad50280a64387
---
 encryption/utils.cpp | 50 +++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 37 insertions(+), 13 deletions(-)

(limited to 'encryption/utils.cpp')

diff --git a/encryption/utils.cpp b/encryption/utils.cpp
index 1956d0a1..03a46bfc 100644
--- a/encryption/utils.cpp
+++ b/encryption/utils.cpp
@@ -379,6 +379,27 @@ static void GetFixedInputString(uint32_t counter,
   PushBigEndian32(derived_key_len, fixed_input_string);
 }
 
+static bool AesCmacKdfHelper(const std::vector<uint8_t> &key,
+                             const std::vector<uint8_t> &label,
+                             const std::vector<uint8_t> &context,
+                             uint32_t output_key_size,
+                             std::vector<uint8_t> *output_data) {
+  output_data->resize(output_key_size);
+  for (size_t count = 0; count < (output_key_size / kAesBlockSize); count++) {
+    std::vector<uint8_t> fixed_input_string;
+    GetFixedInputString(count + 1, label, context, (output_key_size * 8),
+                        &fixed_input_string);
+    if (!AES_CMAC(output_data->data() + (kAesBlockSize * count), key.data(),
+                  key.size(), fixed_input_string.data(),
+                  fixed_input_string.size())) {
+      ADD_FAILURE()
+          << "AES_CMAC failed while deriving subkey from HW wrapped key";
+      return false;
+    }
+  }
+  return true;
+}
+
 bool DeriveHwWrappedEncryptionKey(const std::vector<uint8_t> &master_key,
                                   std::vector<uint8_t> *enc_key) {
   std::vector<uint8_t> label{0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
@@ -392,19 +413,22 @@ bool DeriveHwWrappedEncryptionKey(const std::vector<uint8_t> &master_key,
       0x00, 0x00, 0x00, 0x02, 0x43, 0x00, 0x82, 0x50,
       0x0,  0x0,  0x0,  0x0};
 
-  enc_key->resize(kAes256XtsKeySize);
-  for (size_t count = 0; count < (kAes256XtsKeySize / kAesBlockSize); count++) {
-    std::vector<uint8_t> fixed_input_string;
-    GetFixedInputString(count + 1, label, context, (kAes256XtsKeySize * 8),
-                        &fixed_input_string);
-    if (!AES_CMAC(enc_key->data() + (kAesBlockSize * count), master_key.data(),
-                  master_key.size(), fixed_input_string.data(),
-                  fixed_input_string.size())) {
-      ADD_FAILURE() << "AES_CMAC failed while deriving inline encryption key";
-      return false;
-    }
-  }
-  return true;
+  return AesCmacKdfHelper(master_key, label, context, kAes256XtsKeySize,
+                          enc_key);
+}
+
+bool DeriveHwWrappedRawSecret(const std::vector<uint8_t> &master_key,
+                              std::vector<uint8_t> *secret) {
+  std::vector<uint8_t> label{0x00, 0x00, 0x40, 0x00, 0x00, 0x00,
+                             0x00, 0x00, 0x00, 0x00, 0x20};
+  // Context in fixed input string comprises of software provided context,
+  // padding to eight bytes (if required) and the key policy.
+  std::vector<uint8_t> context = {'r',  'a',  'w',  ' ',  's',  'e',  'c',
+                                  'r',  'e',  't',  0x0,  0x0,  0x0,  0x0,
+                                  0x0,  0x0,  0x00, 0x00, 0x00, 0x02, 0x17,
+                                  0x00, 0x80, 0x50, 0x0,  0x0,  0x0,  0x0};
+
+  return AesCmacKdfHelper(master_key, label, context, kAes256KeySize, secret);
 }
 
 }  // namespace kernel
-- 
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