Add DER parsing support for private keys (#348)

* add EC cert test

* Implement SignaturePrivateKey::parse_der

* add missing ICU dependency

---------

Co-authored-by: Richard Barnes <rlb@ipv.sx>

Author: plq

cmd/interop/CMakeLists.txt

@@ -38,6 +38,7 @@ find_package(OpenSSL 1.1 REQUIRED)
 find_package(Protobuf REQUIRED)
 find_package(gRPC CONFIG REQUIRED)
 find_package(gflags REQUIRED)
+find_package(ICU REQUIRED COMPONENTS uc data)
 
 # mlspp
 set(CMAKE_EXPORT_PACKAGE_REGISTRY ON)
@@ -50,7 +51,7 @@ find_package(nlohmann_json 3.2 REQUIRED)
 ### Protobuf generation
 ###
 
-# Get the proto file from the interop repo 
+# Get the proto file from the interop repo
 include( ExternalProject )
 find_package( Git REQUIRED )
 set( MLS_IMPLEMENTATIONS_REPO_URL https://github.com/mlswg/mls-implementations.git )
@@ -99,7 +100,7 @@ file(GLOB_RECURSE BIN_SOURCES "${CMAKE_CURRENT_SOURCE_DIR}/src/*.cpp")
 add_executable(${APP_NAME} ${BIN_SOURCES} ${PB_SRC} ${GRPC_SRC})
 add_dependencies(${APP_NAME} mls-interop-extern)
 target_include_directories(${APP_NAME} PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
-target_link_libraries(${APP_NAME} 
-  gflags 
-  gRPC::grpc++ protobuf::libprotobuf 
+target_link_libraries(${APP_NAME}
+  gflags ICU::uc ICU::data
+  gRPC::grpc++ protobuf::libprotobuf
   MLSPP::mlspp MLSPP::mls_vectors MLSPP::tls_syntax)

include/mls/crypto.h

@@ -256,6 +256,7 @@ struct SignaturePrivateKey
 {
   static SignaturePrivateKey generate(CipherSuite suite);
   static SignaturePrivateKey parse(CipherSuite suite, const bytes& data);
+  static SignaturePrivateKey parse_der(CipherSuite suite, const bytes& data);
   static SignaturePrivateKey derive(CipherSuite suite, const bytes& secret);
   static SignaturePrivateKey from_jwk(CipherSuite suite,
                                       const std::string& json_str);

lib/hpke/include/hpke/signature.h

@@ -76,6 +76,9 @@ struct Signature
   virtual std::string export_jwk_private(const PrivateKey& env) const = 0;
   virtual std::string export_jwk(const PublicKey& env) const = 0;
 
+  virtual std::unique_ptr<PrivateKey> deserialize_private_der(
+    const bytes& der) const;
+
   virtual bytes sign(const bytes& data, const PrivateKey& sk) const = 0;
   virtual bool verify(const bytes& data,
                       const bytes& sig,

lib/hpke/src/group.cpp

@@ -10,6 +10,7 @@
 #include "openssl/ec.h"
 #include "openssl/evp.h"
 #include "openssl/obj_mac.h"
+#include "openssl/pem.h"
 #if defined(WITH_OPENSSL3)
 #include "openssl/core_names.h"
 #include "openssl/param_build.h"
@@ -761,6 +762,22 @@ struct ECKeyGroup : public EVPGroup
 #endif
   }
 
+  std::unique_ptr<Group::PrivateKey> deserialize_private_der(
+    const bytes& der) const override
+  {
+    BIO* mem = BIO_new_mem_buf(der.data(), static_cast<int>(der.size()));
+    if (!mem) {
+      throw openssl_error();
+    }
+    EVP_PKEY* pkey = d2i_PrivateKey_bio(mem, NULL);
+    BIO_free(mem);
+    if (!pkey) {
+      throw openssl_error();
+    }
+
+    return std::make_unique<EVPGroup::PrivateKey>(pkey);
+  }
+
 private:
   int curve_nid;
 
@@ -896,6 +913,22 @@ struct RawKeyGroup : public EVPGroup
     return std::make_unique<EVPGroup::PrivateKey>(pkey);
   }
 
+  std::unique_ptr<Group::PrivateKey> deserialize_private_der(
+    const bytes& der) const override
+  {
+    BIO* mem = BIO_new_mem_buf(der.data(), static_cast<int>(der.size()));
+    if (!mem) {
+      throw openssl_error();
+    }
+    EVP_PKEY* pkey = d2i_PrivateKey_bio(mem, NULL);
+    BIO_free(mem);
+    if (!pkey) {
+      throw openssl_error();
+    }
+
+    return std::make_unique<RawKeyGroup::PrivateKey>(pkey);
+  }
+
   // Raw Key
   std::tuple<bytes, bytes> coordinates(
     const Group::PublicKey& pk) const override

lib/hpke/src/group.h

@@ -61,6 +61,8 @@ struct Group
   virtual bytes serialize_private(const PrivateKey& sk) const = 0;
   virtual std::unique_ptr<PrivateKey> deserialize_private(
     const bytes& skm) const = 0;
+  virtual std::unique_ptr<PrivateKey> deserialize_private_der(
+    const bytes& der) const = 0;
 
   virtual bytes dh(const PrivateKey& sk, const PublicKey& pk) const = 0;
 

lib/hpke/src/signature.cpp

@@ -12,6 +12,7 @@
 #include <openssl/bn.h>
 #include <openssl/ec.h>
 #include <openssl/evp.h>
+#include <openssl/pem.h>
 #include <openssl/rsa.h>
 
 using nlohmann::json;
@@ -98,6 +99,13 @@ struct GroupSignature : public Signature
       group.deserialize_private(skm).release());
   }
 
+  std::unique_ptr<Signature::PrivateKey> deserialize_private_der(
+    const bytes& der) const override
+  {
+    return std::make_unique<PrivateKey>(
+      group.deserialize_private_der(der).release());
+  }
+
   bytes sign(const bytes& data, const Signature::PrivateKey& sk) const override
   {
     const auto& rsk = dynamic_cast<const PrivateKey&>(sk);
@@ -275,6 +283,12 @@ Signature::Signature(Signature::ID id_in)
 {
 }
 
+std::unique_ptr<Signature::PrivateKey>
+Signature::deserialize_private_der(const bytes&) const
+{
+  throw std::runtime_error("Not implemented");
+}
+
 std::unique_ptr<Signature::PrivateKey>
 Signature::generate_rsa(size_t bits)
 {

src/crypto.cpp

@@ -478,6 +478,16 @@ SignaturePrivateKey::parse(CipherSuite suite, const bytes& data)
   return { data, pub_data };
 }
 
+SignaturePrivateKey
+SignaturePrivateKey::parse_der(CipherSuite suite, const bytes& data)
+{
+  auto priv = suite.sig().deserialize_private_der(data);
+  auto pub = priv->public_key();
+  auto pub_data = suite.sig().serialize(*pub);
+  auto priv_data = suite.sig().serialize_private(*priv);
+  return { priv_data, pub_data };
+}
+
 SignaturePrivateKey
 SignaturePrivateKey::derive(CipherSuite suite, const bytes& secret)
 {

test/credential.cpp

@@ -143,6 +143,40 @@ TEST_CASE("X509 Credential Depth 2")
   CHECK(x509.der_chain == x509_original.der_chain);
 }
 
+TEST_CASE("X509 Credential EC certificates")
+{
+  // Chain is of depth 2
+  const auto keydata =
+    from_hex("30770201010420e32d0df2b096edadd778b3e884e84b14454d02668d3ef9f81e7"
+             "d9425ca9acf82a00a06082a8648ce3d030107a144034200049c37d6e8722c509c"
+             "c71bfda2389d4d3f6da6088b605c8bd6bd6dde6ccf77d3aa8c4f205cc273ac47b"
+             "e9e353e43debf2ad9a226fe0ea7a11b5bb06eb5d932e045");
+  const auto cert = from_hex(
+    "308201e230820187a00302010202045a49733d300a06082a8648ce3d040302307331133011"
+    "060a0992268993f22c6401191603636f6d31173015060a0992268993f22c64011916076d61"
+    "696c6f757331143012060a0992268993f22c640101130474657374312d302b060355040b13"
+    "2431313436386463622d663830342d346563362d616166362d363263623437333931333733"
+    "301e170d3233303731353136303135305a170d3233303831353136303135305a3044311330"
+    "11060a0992268993f22c6401191603636f6d31173015060a0992268993f22c64011916076d"
+    "61696c6f757331143012060a0992268993f22c6401011304746573743059301306072a8648"
+    "ce3d020106082a8648ce3d030107034200049c37d6e8722c509cc71bfda2389d4d3f6da608"
+    "8b605c8bd6bd6dde6ccf77d3aa8c4f205cc273ac47be9e353e43debf2ad9a226fe0ea7a11b"
+    "5bb06eb5d932e045a3383036300e0603551d0f0101ff0404030204f030160603551d250101"
+    "ff040c300a06082b06010505070301300c0603551d130101ff04023000300a06082a8648ce"
+    "3d0403020349003046022100d670fb29f08dd0bc5d81cd6258ade6a8e5b6a5f630b510272c"
+    "ffa8d77f79f24e022100d166a8ae636916c84e1d854def33a57549e06b5c1d2c5e4ea7a797"
+    "df74401531");
+
+  const std::vector<bytes> der_in{ cert };
+
+  auto key = SignaturePrivateKey::parse_der(
+    mls::CipherSuite::ID::P256_AES128GCM_SHA256_P256, keydata);
+
+  auto cred = Credential::x509(der_in);
+  auto x509 = cred.get<X509Credential>();
+  CHECK(x509.public_key() == key.public_key);
+}
+
 TEST_CASE("X509 Credential Depth 2 Marshal/Unmarshal")
 {
   // Chain is of depth 2