AU: detect failure when using public key verification

delta_performer.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/delta_performer.h"
 
 #include <endian.h>
 #include <errno.h>
 
 #include <algorithm>
@@ skipping 551 matching lines @@
   signed_hash_context_ = hash_calculator_.GetContext();
   LOG_IF(WARNING, !prefs_->SetString(kPrefsUpdateStateSignedSHA256Context,
                                      signed_hash_context_))
       << "Unable to store the signed hash context.";
   LOG(INFO) << "Extracted signature data of size "
             << manifest_.signatures_size() << " at "
             << manifest_.signatures_offset();
   return true;
 }
 
+#define TEST_SET_TRUE_RET_TRUE(_var, _condition)                        \
+  do {                                                                  \
+    if (!(_condition)) {                                                \
+      LOG(ERROR) << "Non fatal public key verification: " << #_condition; \
+      (_var) = true;                                                    \
+      return true;                                                      \
+    }                                                                   \
+  } while(0)
+
 bool DeltaPerformer::VerifyPayload(
     const string& public_key_path,
     const std::string& update_check_response_hash,
-    const uint64_t update_check_response_size) {
+    const uint64_t update_check_response_size,
+    bool* signature_failed) {
   string key_path = public_key_path;
   if (key_path.empty()) {
     key_path = kUpdatePayloadPublicKeyPath;
   }
   LOG(INFO) << "Verifying delta payload. Public key path: " << key_path;
 
   // Verifies the download hash.
   const string& download_hash_data = hash_calculator_.hash();
   TEST_AND_RETURN_FALSE(!download_hash_data.empty());
   TEST_AND_RETURN_FALSE(download_hash_data == update_check_response_hash);
 
   // Verifies the download size.
   TEST_AND_RETURN_FALSE(update_check_response_size ==
                         manifest_metadata_size_ + buffer_offset_);
 
   // Verifies the signed payload hash.
   if (!utils::FileExists(key_path.c_str())) {

[petkov, 2011/03/30 22:12:39]

you could probably just do a similar check for signature_failed == NULL and
return true without doing any signature checks...

[adlr, 2011/03/30 22:30:06]

Yeah, but I want to get a log of exactly what fails when it goes wrong.

     LOG(WARNING) << "Not verifying signed delta payload -- missing public key.";
     return true;
   }
-  TEST_AND_RETURN_FALSE(!signatures_message_data_.empty());
+  TEST_SET_TRUE_RET_TRUE(*signature_failed, !signatures_message_data_.empty());

[petkov, 2011/03/30 22:10:21]

This doesn't check for signature_failed != NULL? Either fix the code or update
the docstring in the .h to account for the fact that signature_failed can't be
NULL.

[adlr, 2011/03/30 22:30:06]

Fixed to accept NULL

   vector<char> signed_hash_data;
-  TEST_AND_RETURN_FALSE(PayloadSigner::VerifySignature(signatures_message_data_,
-                                                       key_path,
-                                                       &signed_hash_data));
+  TEST_SET_TRUE_RET_TRUE(*signature_failed, PayloadSigner::VerifySignature(
+      signatures_message_data_,
+      key_path,
+      &signed_hash_data));
   OmahaHashCalculator signed_hasher;
-  TEST_AND_RETURN_FALSE(signed_hasher.SetContext(signed_hash_context_));
-  TEST_AND_RETURN_FALSE(signed_hasher.Finalize());
+  TEST_SET_TRUE_RET_TRUE(*signature_failed,
+                         signed_hasher.SetContext(signed_hash_context_));
+  TEST_SET_TRUE_RET_TRUE(*signature_failed,
+                         signed_hasher.Finalize());
   vector<char> hash_data = signed_hasher.raw_hash();
   PayloadSigner::PadRSA2048SHA256Hash(&hash_data);
-  TEST_AND_RETURN_FALSE(!hash_data.empty());
-  TEST_AND_RETURN_FALSE(hash_data == signed_hash_data);
+  TEST_SET_TRUE_RET_TRUE(*signature_failed, !hash_data.empty());
+  if (hash_data != signed_hash_data) {
+    LOG(ERROR) << "Public key verificaion failed. This is non-fatal. "
+        "Attached Signature:";
+    utils::HexDumpVector(signed_hash_data);
+    LOG(ERROR) << "Computed Signature:";
+    utils::HexDumpVector(hash_data);
+    if (signature_failed) {
+      *signature_failed = true;
+    }
+  }
   return true;
 }
 
+#undef TEST_SET_TRUE_RET_TRUE
+
 bool DeltaPerformer::GetNewPartitionInfo(uint64_t* kernel_size,
                                          vector<char>* kernel_hash,
                                          uint64_t* rootfs_size,
                                          vector<char>* rootfs_hash) {
   TEST_AND_RETURN_FALSE(manifest_valid_ &&
                         manifest_.has_new_kernel_info() &&
                         manifest_.has_new_rootfs_info());
   *kernel_size = manifest_.new_kernel_info().size();
   *rootfs_size = manifest_.new_rootfs_info().size();
   vector<char> new_kernel_hash(manifest_.new_kernel_info().hash().begin(),
@@ skipping 143 matching lines @@
   if (prefs_->GetInt64(kPrefsResumedUpdateFailures, &resumed_update_failures)) {
     resumed_update_failures++;
   } else {
     resumed_update_failures = 1;
   }
   prefs_->SetInt64(kPrefsResumedUpdateFailures, resumed_update_failures);
   return true;
 }
 
 }  // namespace chromeos_update_engine