From fea52d98ca7039adf287400e925ef43bfac48abf Mon Sep 17 00:00:00 2001
From: Toni Uhlig <matzeton@googlemail.com>
Date: Wed, 27 Nov 2024 11:51:53 +0100
Subject: [PATCH] Added nDPId decryption example

Signed-off-by: Toni Uhlig <matzeton@googlemail.com>
---
 CMakeLists.txt                 | 11 ++++-
 examples/c-decrypt/c-decrypt.c | 74 ++++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 examples/c-decrypt/c-decrypt.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index c6dd8ef53..1e5256418 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -15,7 +15,8 @@ if("${PROJECT_SOURCE_DIR}" STREQUAL "${PROJECT_BINARY_DIR}")
                         "Please remove ${PROJECT_SOURCE_DIR}/CMakeCache.txt\n"
                         "and\n"
                         "${PROJECT_SOURCE_DIR}/CMakeFiles\n"
-                        "Create a build directory somewhere and run CMake again.")
+                        "Create a build directory somewhere and run CMake again.\n"
+                        "Or run: 'cmake -S ${PROJECT_SOURCE_DIR} -B ./your-custom-build-dir [CMAKE-OPTIONS]'")
 endif()
 set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake)
 find_package(PkgConfig REQUIRED)
@@ -562,6 +563,14 @@ if(BUILD_EXAMPLES)
         install(TARGETS nDPIsrvd-influxd DESTINATION bin)
     endif()
 
+    if(ENABLE_CRYPTO)
+        add_executable(nDPId-decrypt examples/c-decrypt/c-decrypt.c utils.c ncrypt.c)
+        target_compile_definitions(nDPId-decrypt PRIVATE ${NDPID_DEFS} ${OSSL_DEFS})
+        target_include_directories(nDPId-decrypt PRIVATE ${NDPID_DEPS_INC})
+        target_link_libraries(nDPId-decrypt ${OSSL_LIBRARY})
+        install(TARGETS nDPId-decrypt DESTINATION bin)
+    endif()
+
     install(TARGETS nDPIsrvd-analysed nDPIsrvd-collectd nDPIsrvd-captured nDPIsrvd-simple DESTINATION bin)
     install(FILES examples/c-collectd/plugin_nDPIsrvd.conf examples/c-collectd/rrdgraph.sh DESTINATION share/nDPId/nDPIsrvd-collectd)
     install(DIRECTORY examples/c-collectd/www DESTINATION share/nDPId/nDPIsrvd-collectd)
diff --git a/examples/c-decrypt/c-decrypt.c b/examples/c-decrypt/c-decrypt.c
new file mode 100644
index 000000000..905dbf622
--- /dev/null
+++ b/examples/c-decrypt/c-decrypt.c
@@ -0,0 +1,74 @@
+#include <stdio.h>
+#include <unistd.h>
+
+#include "utils.h"
+
+static void print_usage(char const * const arg0)
+{
+    static char const usage[] =
+        "Usage: %s "
+        "[-L listen-address] [-k private-key-file] [-K public-key-file]\n"
+        "\t  \t"
+        "[-h]\n\n"
+        "\t-L\tThe address on which this example will listen for incoming\n"
+        "\t  \t(encrypted) UDP packets sent by nDPId\n"
+        "\t-k\tThe path to the local private X25519 key file (PEM format)\n"
+        "\t-K\tThe path to the remote public X25519 key file (PEM format)\n"
+        "\t-h\tthis\n";
+
+    fprintf(stderr, usage, arg0);
+}
+
+static int parse_options(int argc, char ** argv)
+{
+    int opt;
+
+    while ((opt = getopt(argc, argv, "hk:K:s:")) != -1)
+    {
+        switch (opt)
+        {
+            case 'h':
+                print_usage(argv[0]);
+                return 1;
+            case 'k':
+                break;
+            case 'K':
+                break;
+            case 's':
+                break;
+            default:
+                print_usage(argv[0]);
+                return 1;
+        }
+    }
+
+    if (optind < argc)
+    {
+        if (optind > 0) {
+            logger_early(1, "Unexpected argument(s) after %s\n\n", argv[optind]);
+        } else {
+            logger_early(1, "%s\n\n", "Unexpected argument(s)");
+        }
+        print_usage(argv[0]);
+
+        return 1;
+    }
+
+    return 0;
+}
+
+int main(int argc, char ** argv)
+{
+    if (argc == 0 || argv == NULL || stdout == NULL || stderr == NULL)
+    {
+        return 1;
+    }
+
+    init_logging("nDPId-decrypt");
+
+    if (parse_options(argc, argv) != 0)
+    {
+    }
+
+    return 0;
+}