From 55975ecbcfd0b4d3d9251d094ad8ba25ebac065a Mon Sep 17 00:00:00 2001
From: David Zeuthen <zeuthen@google.com>
Date: Thu, 27 Feb 2020 14:28:18 -0500
Subject: [PATCH] credstore: signingKeyBlob was moved from finishRetrieval() to
 startRetrieval().

The implementation of the Identity Credential TA in constrained
environments may need to incrementally update the HMAC-SHA256 of
DeviceAuthencation CBOR to avoid keeping the entire CBOR structure in
memory. To do this they need to calculate the derived key before
starting to build the CBOR so they need access to the signingKey
earlier on. Update credstore to pass the signingKey earlier.

Bug: 150390415
Test: atest android.security.identity.cts
Test: VtsHalIdentityTargetTest
Change-Id: If2479a10f80fba748591c30aa7b8662e1063787e
---
 identity/Credential.cpp | 45 +++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/identity/Credential.cpp b/identity/Credential.cpp
index 604d2621..05c31d3d 100644
--- a/identity/Credential.cpp
+++ b/identity/Credential.cpp
@@ -242,8 +242,28 @@ Status Credential::getEntries(const vector<uint8_t>& requestMessage,
         }
     }
 
-    Status status = halBinder_->startRetrieval(selectedProfiles, aidlAuthToken, requestMessage,
-                                               sessionTranscript, readerSignature, requestCounts);
+    // Note that the selectAuthKey() method is only called if a CryptoObject is involved at
+    // the Java layer. So we could end up with no previously selected auth key and we may
+    // need one.
+    const AuthKeyData* authKey = selectedAuthKey_;
+    if (sessionTranscript.size() > 0) {
+        if (authKey == nullptr) {
+            authKey = data_->selectAuthKey(allowUsingExhaustedKeys);
+            if (authKey == nullptr) {
+                return Status::fromServiceSpecificError(
+                    ICredentialStore::ERROR_NO_AUTHENTICATION_KEY_AVAILABLE,
+                    "No suitable authentication key available");
+            }
+        }
+    }
+    vector<uint8_t> signingKeyBlob;
+    if (authKey != nullptr) {
+        signingKeyBlob = authKey->keyBlob;
+    }
+
+    Status status =
+        halBinder_->startRetrieval(selectedProfiles, aidlAuthToken, requestMessage, signingKeyBlob,
+                                   sessionTranscript, readerSignature, requestCounts);
     if (!status.isOk() && status.exceptionCode() == binder::Status::EX_SERVICE_SPECIFIC) {
         int code = status.serviceSpecificErrorCode();
         if (code == IIdentityCredentialStore::STATUS_EPHEMERAL_PUBLIC_KEY_NOT_FOUND) {
@@ -319,26 +339,7 @@ Status Credential::getEntries(const vector<uint8_t>& requestMessage,
         ret.resultNamespaces.push_back(resultNamespaceParcel);
     }
 
-    // Note that the selectAuthKey() method is only called if a CryptoObject is involved at
-    // the Java layer. So we could end up with no previously selected auth key and we may
-    // need one.
-    const AuthKeyData* authKey = selectedAuthKey_;
-    if (sessionTranscript.size() > 0) {
-        if (authKey == nullptr) {
-            authKey = data_->selectAuthKey(allowUsingExhaustedKeys);
-            if (authKey == nullptr) {
-                return Status::fromServiceSpecificError(
-                    ICredentialStore::ERROR_NO_AUTHENTICATION_KEY_AVAILABLE,
-                    "No suitable authentication key available");
-            }
-        }
-    }
-
-    vector<uint8_t> signingKeyBlob;
-    if (authKey != nullptr) {
-        signingKeyBlob = authKey->keyBlob;
-    }
-    status = halBinder_->finishRetrieval(signingKeyBlob, &ret.mac, &ret.deviceNameSpaces);
+    status = halBinder_->finishRetrieval(&ret.mac, &ret.deviceNameSpaces);
     if (!status.isOk()) {
         return halStatusToGenericError(status);
     }