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

security/keymint/aidl/vts/functional/Android.bp

@@ -23,16 +23,11 @@ package {
     default_applicable_licenses: ["hardware_interfaces_license"],
 }
 
-cc_test {
-    name: "VtsAidlKeyMintTargetTest",
+cc_defaults {
+    name: "keymint_vts_defaults",
     defaults: [
-        "VtsHalTargetTestDefaults",
         "use_libaidlvintf_gtest_helper_static",
-    ],
-    srcs: [
-        "AttestKeyTest.cpp",
-        "DeviceUniqueAttestationTest.cpp",
-        "KeyMintTest.cpp",
+        "VtsHalTargetTestDefaults",
     ],
     shared_libs: [
         "libbinder_ndk",
@@ -43,9 +38,24 @@ cc_test {
         "android.hardware.security.secureclock-V1-ndk_platform",
         "libcppbor_external",
         "libcppcose_rkp",
+        "libjsoncpp",
         "libkeymint",
         "libkeymint_remote_prov_support",
         "libkeymint_support",
+    ],
+}
+
+cc_test {
+    name: "VtsAidlKeyMintTargetTest",
+    defaults: [
+        "keymint_vts_defaults",
+    ],
+    srcs: [
+        "AttestKeyTest.cpp",
+        "DeviceUniqueAttestationTest.cpp",
+        "KeyMintTest.cpp",
+    ],
+    static_libs: [
         "libkeymint_vts_test_utils",
     ],
     test_suites: [
@@ -57,8 +67,7 @@ cc_test {
 cc_test_library {
     name: "libkeymint_vts_test_utils",
     defaults: [
-        "VtsHalTargetTestDefaults",
-        "use_libaidlvintf_gtest_helper_static",
+        "keymint_vts_defaults",
     ],
     srcs: [
         "KeyMintAidlTestBase.cpp",
@@ -66,45 +75,22 @@ cc_test_library {
     export_include_dirs: [
         ".",
     ],
-    shared_libs: [
-        "libbinder_ndk",
-        "libcrypto",
-    ],
     static_libs: [
-        "android.hardware.security.keymint-V1-ndk_platform",
-        "android.hardware.security.secureclock-V1-ndk_platform",
-        "libcppbor_external",
-        "libcppcose_rkp",
         "libgmock_ndk",
-        "libkeymint",
-        "libkeymint_remote_prov_support",
-        "libkeymint_support",
     ],
 }
 
 cc_test {
     name: "VtsHalRemotelyProvisionedComponentTargetTest",
     defaults: [
-        "VtsHalTargetTestDefaults",
-        "use_libaidlvintf_gtest_helper_static",
+        "keymint_vts_defaults",
     ],
     srcs: [
         "VtsRemotelyProvisionedComponentTests.cpp",
     ],
-    shared_libs: [
-        "libbinder_ndk",
-        "libcrypto",
-    ],
     static_libs: [
-        "android.hardware.security.keymint-V1-ndk_platform",
-        "android.hardware.security.secureclock-V1-ndk_platform",
-        "libcppbor_external",
-        "libcppcose_rkp",
         "libgmock_ndk",
         "libkeymaster_portable",
-        "libkeymint",
-        "libkeymint_support",
-        "libkeymint_remote_prov_support",
         "libkeymint_vts_test_utils",
         "libpuresoftkeymasterdevice",
     ],

security/keymint/support/Android.bp

@@ -57,9 +57,11 @@ cc_library {
         "include",
     ],
     shared_libs: [
+        "libbase",
         "libcppbor_external",
         "libcppcose_rkp",
         "libcrypto",
+        "libjsoncpp",
     ],
 }
 
@@ -71,9 +73,11 @@ cc_test {
         "libgtest_main",
     ],
     shared_libs: [
+        "libbase",
         "libcppbor_external",
         "libcppcose_rkp",
         "libcrypto",
+        "libjsoncpp",
         "libkeymaster_portable",
         "libkeymint_remote_prov_support",
     ],

security/keymint/support/include/remote_prov/remote_prov_utils.h

@@ -87,4 +87,26 @@ struct BccEntryData {
  */
 ErrMsgOr<std::vector<BccEntryData>> validateBcc(const cppbor::Array* bcc);
 
+struct JsonOutput {
+    static JsonOutput Ok(std::string json) { return {std::move(json), ""}; }
+    static JsonOutput Error(std::string error) { return {"", std::move(error)}; }
+
+    std::string output;
+    std::string error;  // if non-empty, this describes what went wrong
+};
+
+/**
+ * Take a given certificate request and output a JSON blob containing both the
+ * build fingerprint and certificate request. This data may be serialized, then
+ * later uploaded to the remote provisioning service. The input csr is not
+ * validated, only encoded.
+ *
+ * Output format:
+ *   {
+ *     "build_fingerprint": <string>
+ *     "csr": <base64 CBOR CSR>
+ *   }
+ */
+JsonOutput jsonEncodeCsrWithBuild(const cppbor::Array& csr);
+
 }  // namespace aidl::android::hardware::security::keymint::remote_prov

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

security/keymint/support/remote_prov_utils_test.cpp

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <android-base/properties.h>
 #include <cppbor_parse.h>
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
@@ -23,6 +24,7 @@
 #include <openssl/curve25519.h>
 #include <remote_prov/remote_prov_utils.h>
 #include <cstdint>
+#include "cppbor.h"
 #include "keymaster/cppcose/cppcose.h"
 
 namespace aidl::android::hardware::security::keymint::remote_prov {
@@ -80,5 +82,20 @@ TEST(RemoteProvUtilsTest, GetProdEekChain) {
     EXPECT_THAT(eekPub, ElementsAreArray(geek->getBstrValue(CoseKey::PUBKEY_X).value_or(empty)));
 }
 
+TEST(RemoteProvUtilsTest, JsonEncodeCsr) {
+    cppbor::Array array;
+    array.add(1);
+
+    auto [json, error] = jsonEncodeCsrWithBuild(array);
+
+    ASSERT_TRUE(error.empty()) << error;
+
+    std::string expected = R"({"build_fingerprint":")" +
+                           ::android::base::GetProperty("ro.build.fingerprint", /*default=*/"") +
+                           R"(","csr":"gQE="})";
+
+    ASSERT_EQ(json, expected);
+}
+
 }  // namespace
 }  // namespace aidl::android::hardware::security::keymint::remote_prov