Check all signatures regardless of the version.
The update_engine daemon had a fixed version number for the public key
used to verify both the metadata and whole payload signatures. The
public key itself is installed by the signer, implying that the source
code and the signer need to be in sync if we ever need to roll the
payload key.
This situation becomes more of a problem if we don't control when the
version number included in the source code is updated in the built
image sent for payload generation and signing.
This patch makes update_engine ignore the version number associated
with a signature and instead tries to verify all the signatures
included in the payload against the public key found in the code. This
effectively deprecates the key version number. To be compatible with
old versions, the version number 1 is included in all signatures.
Bug: 23601118
Test: Added unittests.
Change-Id: I4f96cc207ad6b9c011def5ce586d0e0e85af28ab
diff --git a/payload_verifier.cc b/payload_verifier.cc
index c3dc134..f713fb1 100644
--- a/payload_verifier.cc
+++ b/payload_verifier.cc
@@ -28,9 +28,6 @@
namespace chromeos_update_engine {
-const uint32_t kSignatureMessageOriginalVersion = 1;
-const uint32_t kSignatureMessageCurrentVersion = 1;
-
namespace {
// The following is a standard PKCS1-v1_5 padding for SHA256 signatures, as
@@ -111,38 +108,43 @@
bool PayloadVerifier::VerifySignature(const chromeos::Blob& signature_blob,
const string& public_key_path,
- chromeos::Blob* out_hash_data) {
- return VerifySignatureBlob(signature_blob, public_key_path,
- kSignatureMessageCurrentVersion, out_hash_data);
-}
-
-bool PayloadVerifier::VerifySignatureBlob(
- const chromeos::Blob& signature_blob,
- const string& public_key_path,
- uint32_t client_version,
- chromeos::Blob* out_hash_data) {
+ const chromeos::Blob& hash_data) {
TEST_AND_RETURN_FALSE(!public_key_path.empty());
Signatures signatures;
- LOG(INFO) << "signature size = " << signature_blob.size();
+ LOG(INFO) << "signature blob size = " << signature_blob.size();
TEST_AND_RETURN_FALSE(signatures.ParseFromArray(signature_blob.data(),
signature_blob.size()));
- // Finds a signature that matches the current version.
- int sig_index = 0;
- for (; sig_index < signatures.signatures_size(); sig_index++) {
- const Signatures_Signature& signature = signatures.signatures(sig_index);
- if (signature.has_version() &&
- signature.version() == client_version) {
- break;
- }
+ if (!signatures.signatures_size()) {
+ LOG(ERROR) << "No signatures stored in the blob.";
+ return false;
}
- TEST_AND_RETURN_FALSE(sig_index < signatures.signatures_size());
- const Signatures_Signature& signature = signatures.signatures(sig_index);
- chromeos::Blob sig_data(signature.data().begin(), signature.data().end());
+ std::vector<chromeos::Blob> tested_hashes;
+ // Tries every signature in the signature blob.
+ for (int i = 0; i < signatures.signatures_size(); i++) {
+ const Signatures_Signature& signature = signatures.signatures(i);
+ chromeos::Blob sig_data(signature.data().begin(), signature.data().end());
+ chromeos::Blob sig_hash_data;
+ if (!GetRawHashFromSignature(sig_data, public_key_path, &sig_hash_data))
+ continue;
- return GetRawHashFromSignature(sig_data, public_key_path, out_hash_data);
+ if (hash_data == sig_hash_data) {
+ LOG(INFO) << "Verified correct signature " << i + 1 << " out of "
+ << signatures.signatures_size() << " signatures.";
+ return true;
+ }
+ tested_hashes.push_back(sig_hash_data);
+ }
+ LOG(ERROR) << "None of the " << signatures.signatures_size()
+ << " signatures is correct. Expected:";
+ utils::HexDumpVector(hash_data);
+ LOG(ERROR) << "But found decrypted hashes:";
+ for (const auto& sig_hash_data : tested_hashes) {
+ utils::HexDumpVector(sig_hash_data);
+ }
+ return false;
}
@@ -191,8 +193,7 @@
}
bool PayloadVerifier::VerifySignedPayload(const string& payload_path,
- const string& public_key_path,
- uint32_t client_key_check_version) {
+ const string& public_key_path) {
chromeos::Blob payload;
DeltaArchiveManifest manifest;
uint64_t metadata_size;
@@ -206,15 +207,12 @@
chromeos::Blob signature_blob(
payload.begin() + metadata_size + manifest.signatures_offset(),
payload.end());
- chromeos::Blob signed_hash;
- TEST_AND_RETURN_FALSE(VerifySignatureBlob(
- signature_blob, public_key_path, client_key_check_version, &signed_hash));
- TEST_AND_RETURN_FALSE(!signed_hash.empty());
chromeos::Blob hash;
TEST_AND_RETURN_FALSE(OmahaHashCalculator::RawHashOfBytes(
payload.data(), metadata_size + manifest.signatures_offset(), &hash));
- PadRSA2048SHA256Hash(&hash);
- TEST_AND_RETURN_FALSE(hash == signed_hash);
+ TEST_AND_RETURN_FALSE(PadRSA2048SHA256Hash(&hash));
+ TEST_AND_RETURN_FALSE(VerifySignature(
+ signature_blob, public_key_path, hash));
return true;
}
