done

client.cpp

@@ -34,6 +34,25 @@ void load_env(const std::string& path) {
     }
 }
 
+// hex to byte helper function
+int hex_to_bytes_upper(const char* hex, unsigned char* out, size_t out_size)
+{
+    size_t i = 0;
+    while (hex[0] && hex[1]) {
+        if (i >= out_size) return -1;
+        unsigned char h = hex[0];
+        unsigned char l = hex[1];
+        int hi = (h <= '9') ? (h - '0') : (h - 'A' + 10);
+        int lo = (l <= '9') ? (l - '0') : (l - 'A' + 10);
+        // minimal sanity check
+        if (hi < 0 || hi > 15 || lo < 0 || lo > 15)
+            return -1;
+        out[i++] = (unsigned char)((hi << 4) | lo);
+        hex += 2;
+    }
+    return (int)i;
+}
+
 // steam cipher encryption function
 int stream_encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *key, unsigned char *iv, unsigned char *ciphertext) {
     /* Declare cipher context */
@@ -43,6 +62,9 @@ int stream_encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *k
 
     /* Create and initialise the context */
     ctx = EVP_CIPHER_CTX_new();
+    if (!ctx) {
+        ERR_print_errors_fp(stderr);
+    }
 
     /* Initialise the encryption operation. */
     // choice for aes_256 ref: https://stackoverflow.com/questions/1220751/how-to-choose-an-aes-encryption-mode-cbc-ecb-ctr-ocb-cfb
@@ -63,7 +85,7 @@ int stream_encrypt(unsigned char *plaintext, int plaintext_len, unsigned char *k
     /* Clean up */
     EVP_CIPHER_CTX_free(ctx);
 
-    return ciphertext_len;
+    return len + ciphertext_len;
 }
 
 int main(void){
@@ -80,7 +102,16 @@ int main(void){
     // encryption parameters
     const char *inital_vector = std::getenv("INITIAL_VECTOR");
     const char *secret_key = std::getenv("SECRET_KEY");
+    unsigned char key_bytes[32], iv_bytes[16];
     
+    int key_len = hex_to_bytes_upper(secret_key, key_bytes, sizeof(key_bytes));
+    int iv_len  = hex_to_bytes_upper(inital_vector, iv_bytes, sizeof(iv_bytes));
+
+    if (key_len != 32 || iv_len != 16) {
+        fprintf(stderr, "Invalid key/IV size for AES-256\n");
+        return 1;
+    }
+
     // Create socket:
     int client_socket = socket(AF_INET, SOCK_STREAM, 0);
     if (client_socket == -1) {
@@ -121,14 +152,23 @@ int main(void){
         char buffer[2048];
         std::snprintf(buffer, sizeof(buffer), "%s%s", custom_message, client_message);
 
-        // encrypt message
-        char ciphertext[2048];
-        int ciphertext_len = stream_encrypt((unsigned char*)buffer, sizeof(buffer), (unsigned char*)secret_key, (unsigned char*)inital_vector, (unsigned char*)ciphertext);
+        unsigned char ciphertext[2048];
 
-        send(client_socket, ciphertext, ciphertext_len, 0);
+        int plaintext_len = (int)strlen(buffer);
+        int ciphertext_len = stream_encrypt((unsigned char*)buffer, plaintext_len, key_bytes, iv_bytes, ciphertext);
+        if (ciphertext_len <= 0) {
+            printf("encrypt failed or produced empty ciphertext_len=%d\n", ciphertext_len);
+            break;
+        }
+
+        ssize_t sent = send(client_socket, ciphertext, (size_t)ciphertext_len, 0);
+        if (sent <= 0) { perror("No message sent to server"); break; }
 
         // Receive the server's response:
-        recv(client_socket, server_message, sizeof(server_message), 0);
+        // add terminator for string
+        ssize_t recvd = recv(client_socket, server_message, sizeof(server_message) - 1, 0);
+        if (recvd <= 0) { perror("No message received from server"); break; }
+        server_message[recvd] = '\0';
 
         printf("Server's response: %s\n", server_message);