Add a utility to JSON-format a CSR with build info

We need both the build fingerprint as well as the CSR when uploading
data to the APFE provisioning server. Add a utility function to format
the output as a JSON blob so that it may be easily collected in the
factory in a serialized data format, then later uploaded.

Test: libkeymint_remote_prov_support_test
Test: VtsAidlKeyMintTargetTest
Test: VtsHalRemotelyProvisionedComponentTargetTest
Bug: 191301285
Change-Id: I751c5461876d83251869539f1a395ba13cb5cf84

1 files changed, 38 insertions, 4 deletions

diff --git a/security/keymint/support/remote_prov_utils.cpp b/security/keymint/support/remote_prov_utils.cpp
index 982a1eb7b1..0cbee51044 100644
--- a/security/keymint/support/remote_prov_utils.cpp
+++ b/security/keymint/support/remote_prov_utils.cpp
@@ -14,13 +14,15 @@
  * limitations under the License.
  */
 
+#include <iterator>
 #include <tuple>
 
-#include <remote_prov/remote_prov_utils.h>
-
-#include <openssl/rand.h>
-
+#include <android-base/properties.h>
 #include <cppbor.h>
+#include <json/json.h>
+#include <openssl/base64.h>
+#include <openssl/rand.h>
+#include <remote_prov/remote_prov_utils.h>
 
 namespace aidl::android::hardware::security::keymint::remote_prov {
 
@@ -180,4 +182,36 @@ ErrMsgOr<std::vector<BccEntryData>> validateBcc(const cppbor::Array* bcc) {
     return result;
 }
 
+JsonOutput jsonEncodeCsrWithBuild(const cppbor::Array& csr) {
+    const std::string kFingerprintProp = "ro.build.fingerprint";
+
+    if (!::android::base::WaitForPropertyCreation(kFingerprintProp)) {
+        return JsonOutput::Error("Unable to read build fingerprint");
+    }
+
+    bytevec csrCbor = csr.encode();
+    size_t base64Length;
+    int rc = EVP_EncodedLength(&base64Length, csrCbor.size());
+    if (!rc) {
+        return JsonOutput::Error("Error getting base64 length. Size overflow?");
+    }
+
+    std::vector<char> base64(base64Length);
+    rc = EVP_EncodeBlock(reinterpret_cast<uint8_t*>(base64.data()), csrCbor.data(), csrCbor.size());
+    ++rc;  // Account for NUL, which BoringSSL does not for some reason.
+    if (rc != base64Length) {
+        return JsonOutput::Error("Error writing base64. Expected " + std::to_string(base64Length) +
+                                 " bytes to be written, but " + std::to_string(rc) +
+                                 " bytes were actually written.");
+    }
+
+    Json::Value json(Json::objectValue);
+    json["build_fingerprint"] = ::android::base::GetProperty(kFingerprintProp, /*default=*/"");
+    json["csr"] = base64.data();  // Boring writes a NUL-terminated c-string
+
+    Json::StreamWriterBuilder factory;
+    factory["indentation"] = "";  // disable pretty formatting
+    return JsonOutput::Ok(Json::writeString(factory, json));
+}
+
 }  // namespace aidl::android::hardware::security::keymint::remote_prov