fix use-after-free in OpenSSL Hash copy constructor

src/Library/Hash.cpp

@@ -70,7 +70,24 @@ namespace usbguard
     _state = rhs._state;
 #endif
 #if defined(USBGUARD_USE_OPENSSL)
-    _state = rhs._state;
+  #if OPENSSL_VERSION_NUMBER >= 0x10100000L
+
+    if ((_state = EVP_MD_CTX_new()) == nullptr) {
+      throw std::runtime_error("Dynamic memory allocation of message digest context failed.");
+    }
+
+  #else
+
+    if ((_state = EVP_MD_CTX_create()) == nullptr) {
+      throw std::runtime_error("Dynamic memory allocation of message digest context failed.");
+    }
+
+  #endif
+
+    if (!EVP_MD_CTX_copy_ex(_state, rhs._state)) {
+      throw std::runtime_error("Copying of message digest context failed.");
+    }
+
 #endif
 #if defined(USBGUARD_USE_LIBGCRYPT)
     gcry_md_copy(&_state, rhs._state);

src/Tests/Makefile.am

@@ -119,6 +119,7 @@ test_unit_SOURCES=\
 	Unit/test_Rule.cpp \
 	Unit/test_RuleParser.cpp \
 	Unit/test_Base64.cpp \
+	Unit/test_Hash.cpp \
 	Unit/test_UEvent.cpp \
 	Unit/test_UEventParser.cpp \
 	Unit/test_Utility.cpp \

src/Tests/Unit/test_Hash.cpp

@@ -0,0 +1,47 @@
+//
+// Copyright (C) 2024 Red Hat, Inc.
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+// Authors: Daniel Kopecek <dkopecek@redhat.com>
+//
+#ifdef HAVE_CATCH2_V3
+  #include <catch_test_macros.hpp>
+#else
+  #include <catch.hpp>
+#endif
+#include <Hash.cpp>
+
+using namespace usbguard;
+
+TEST_CASE("Hash", "[Hash]")
+{
+  SECTION("copy does not share state with the original") {
+    std::string expected;
+    {
+      Hash reference;
+      reference.update(std::string("foo"));
+      expected = reference.getBase64();
+    }
+    Hash original;
+    original.update(std::string("foo"));
+    {
+      Hash copy(original);
+      copy.update(std::string("bar"));
+    }
+    REQUIRE(original.getBase64() == expected);
+  }
+}
+
+/* vim: set ts=2 sw=2 et */