From d61bafdb8514a3e4b37793f3f08df72d4de4638c Mon Sep 17 00:00:00 2001
From: Sascha Tommasone <sascha@tommasone.me>
Date: Sat, 6 Jul 2024 15:59:40 +0200
Subject: [PATCH] [Assignment-7] embedded device prototype

---
 7-SGX_Hands-on/src/app/embedded_device.c | 126 +++++++++++++++++++++++
 7-SGX_Hands-on/src/app/embedded_device.h |   6 ++
 2 files changed, 132 insertions(+)
 create mode 100644 7-SGX_Hands-on/src/app/embedded_device.c
 create mode 100644 7-SGX_Hands-on/src/app/embedded_device.h

diff --git a/7-SGX_Hands-on/src/app/embedded_device.c b/7-SGX_Hands-on/src/app/embedded_device.c
new file mode 100644
index 0000000..f6fcce0
--- /dev/null
+++ b/7-SGX_Hands-on/src/app/embedded_device.c
@@ -0,0 +1,126 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/sha.h>
+#include <openssl/ec.h>
+#include <openssl/bn.h>
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/pem.h>
+#include <openssl/core_names.h>
+
+#include "embedded_device.h"
+
+#define BUFSIZE 16384
+
+typedef struct {
+    uint8_t *firmware_path;
+    uint8_t *public_key_path;
+} embedded_device_args;
+
+static void syntax_exit() {
+    fprintf(stderr, "syntax error!\n");
+    exit(EXIT_FAILURE);
+}
+
+static EVP_PKEY *read_public_key(uint8_t *public_key_file, EVP_PKEY **key) {
+    if(public_key_file == NULL) {
+        fprintf(stderr, "public_key_file is a null pointer!\n");
+    }
+
+    FILE *fd = fopen(public_key_file, "rb");
+    if(fd == NULL) {
+        fprintf(stderr, "failed to open public key file!\n");
+        return NULL;
+    }
+
+    *key = PEM_read_PUBKEY(fd, key, NULL, NULL);
+    fclose(fd);
+
+    return *key;
+}
+
+static void hash_firmware(uint8_t *firmware_path, EVP_MD_CTX **ctx) {
+    if(firmware_path == NULL) {
+        fprintf(stderr, "firmware_path is a null pointer!\n");
+    }
+
+    FILE *fd = fopen(firmware_path, "rb");
+    if(fd == NULL) {
+        fprintf(stderr, "failed to open firmware!\n");
+    }
+
+    size_t size;
+    uint8_t buf[BUFSIZE];
+    while((size = fread(buf, 1, BUFSIZE, fd)) != 0) {
+        EVP_DigestVerifyUpdate(*ctx, buf, size);
+    }
+
+    fclose(fd);
+}
+
+static void read_signature(uint8_t *signature, size_t *signature_size) {
+    FILE *fd = stdin;
+    if(fd == NULL) {
+        fprintf(stderr, "failed to stdin!\n");
+    }
+
+    // TODO: ersmal ne pause :)
+
+}
+
+int main(int argc, char **argv) {
+    embedded_device_args args = {
+        .firmware_path = NULL,
+        .public_key_path = NULL
+    };
+
+    if(argc == 1) {
+        syntax_exit();
+    }
+
+    for(int i = 1; i < argc; i += 2) {
+        if((strcmp(argv[i], "-pub") == 0) && (argc - i >= 2)) {
+            args.public_key_path = argv[i+1];
+        } else if((strcmp(argv[i], "-firm") == 0) && (argc - i >= 2)) {
+            args.firmware_path = argv[i+1];
+        } else {
+            syntax_exit();
+        }
+    }
+
+    if((args.firmware_path == NULL) || (args.public_key_path == NULL)) {
+        fprintf(stderr, "failed to parse arguments");
+        exit(EXIT_FAILURE);
+    }
+
+    EVP_PKEY *key = NULL;
+    if(read_public_key(args.public_key_path, &key) == NULL) {
+        fprintf(stderr, "failed to import public key");
+        goto clean;
+    }
+
+    EVP_MD_CTX *ctx = EVP_MD_CTX_new();
+    if (EVP_DigestVerifyInit(ctx, NULL, EVP_sha256(), NULL, key) != 1) {
+        fprintf(stderr, "failed to initialize context\n");
+        goto clean;
+    }
+
+    read_signature(NULL, NULL);
+    goto clean;
+
+    hash_firmware(args.firmware_path, &ctx);
+    if (EVP_DigestVerifyFinal(ctx, NULL, 0) != 1) {
+        printf("failed to verify firmware signature\n");
+        goto clean;
+    }    
+
+    clean: ;
+    if(key != NULL)
+        EVP_PKEY_free(key);
+    if(ctx != NULL)
+        EVP_MD_CTX_free(ctx);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/7-SGX_Hands-on/src/app/embedded_device.h b/7-SGX_Hands-on/src/app/embedded_device.h
new file mode 100644
index 0000000..59d699c
--- /dev/null
+++ b/7-SGX_Hands-on/src/app/embedded_device.h
@@ -0,0 +1,6 @@
+#ifndef EMBEDDED_DEVICE_H
+#define EMBEDDED_DEVICE_H
+
+#include <stdint.h>
+
+#endif
\ No newline at end of file