init
This commit is contained in:
Zheyuan Wu
271
server.cpp
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271
server.cpp
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#include <stdio.h>
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#include <string.h>
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#include <sys/socket.h>
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#include <arpa/inet.h>
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// open ssl
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#include <openssl/conf.h>
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#include <openssl/evp.h>
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#include <openssl/err.h>
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#include <errno.h> // for perror()
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#include <unistd.h> // for close()
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#include <string>
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#include <cstring>
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#include <cstdlib> // for atoi()
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#include <vector>
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// load environment variables from .env file, and additional helper functions
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#include "helper.h"
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using std::string;
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using std::vector;
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int gcm_decrypt(unsigned char *ciphertext, int ciphertext_len,
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unsigned char *aad, int aad_len,
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unsigned char *tag,
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unsigned char *key,
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unsigned char *iv, int iv_len,
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unsigned char *plaintext)
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{
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EVP_CIPHER_CTX *ctx;
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int len, plaintext_len, ret;
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/* Create and initialize the context */
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ctx = EVP_CIPHER_CTX_new();
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if (!ctx)
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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/* Initialize the decryption operation. */
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if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, key, iv))
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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/* Set IV length. Not necessary if this is 12 bytes (96 bits) */
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if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, iv_len, NULL))
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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/* Initialize key and IV */
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if (!EVP_DecryptInit_ex(ctx, NULL, NULL, key, iv))
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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/*
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* Provide any AAD data. This can be called zero or more times as
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* required
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*/
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if (!EVP_DecryptUpdate(ctx, NULL, &len, aad, aad_len))
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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/*
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* Provide the message to be decrypted, and obtain the plaintext
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output.
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* EVP_DecryptUpdate can be called multiple times if necessary
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*/
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if (!EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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plaintext_len = len;
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/* Set expected tag value. Works in OpenSSL 1.0.1d and later */
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if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, 16, tag))
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{
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ERR_print_errors_fp(stderr);
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EVP_CIPHER_CTX_free(ctx);
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return 0;
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}
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/*
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* Finalize the decryption. A positive return value indicates success,
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* and anything else is a failure - the plaintext is not trustworthy.
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*/
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ret = EVP_DecryptFinal_ex(ctx, plaintext + len, &len);
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/* Clean up */
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EVP_CIPHER_CTX_free(ctx);
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if (ret > 0)
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{
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/* Success */
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plaintext_len += len;
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return plaintext_len;
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}
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else
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{
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/* Verify failed */
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return 0;
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}
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}
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int main(void)
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{
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printf("Server starting...\n");
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load_env(".env");
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// Declare variables
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const char *server_ip = getenv("SERVER_IP");
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const int server_port = atoi(getenv("SERVER_PORT"));
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char client_message[2048];
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char server_message[2048];
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const char *custom_message_success = "Server: Hello from server, message authenticated!\n";
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const char *custom_message_failed = "Server: Hello from server, message failed authentication!\n";
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// debug
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printf("Server starting at IP: %s, Port: %d\n", server_ip, server_port);
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// encryption parameters
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const char *inital_vector = std::getenv("INITIAL_VECTOR");
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const char *secret_key = std::getenv("SECRET_KEY");
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const char *add = std::getenv("ADD");
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unsigned char key_bytes[32], iv_bytes[16];
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int key_len = hex_to_bytes_upper(secret_key, key_bytes, sizeof(key_bytes));
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int iv_len = hex_to_bytes_upper(inital_vector, iv_bytes, sizeof(iv_bytes));
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if (key_len != 32 || iv_len != 16)
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{
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fprintf(stderr, "Invalid key/IV size for AES-256-GCM\n");
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return 1;
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}
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// Create socket
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const int server_socket = socket(AF_INET, SOCK_STREAM, 0);
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if (server_socket == -1)
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{
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perror("Failed to create socket");
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return 1;
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}
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// Bind to the set port and IP
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struct sockaddr_in server_addr;
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server_addr.sin_family = AF_INET;
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server_addr.sin_port = htons(server_port);
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inet_pton(AF_INET, server_ip, &server_addr.sin_addr);
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if (bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1)
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{
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perror("Failed to bind socket");
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close(server_socket);
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return 1;
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}
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printf("Done with binding with IP: %s, Port: %d\n", server_ip, server_port);
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// Listen for clients:
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const char *client_ip = getenv("CLIENT_IP");
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if (listen(server_socket, 1) == -1)
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{
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perror("Failed to listen on socket");
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close(server_socket);
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return 1;
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}
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printf("Listening for incoming connections...\n");
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// Accept an incoming connection
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struct sockaddr_in client_addr;
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socklen_t client_addr_len = sizeof(client_addr);
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int client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &client_addr_len);
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if (client_socket == -1)
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{
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perror("Failed to accept connection");
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close(server_socket);
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return 1;
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}
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printf("Client connected at IP: %s \n", client_ip);
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// clean exising buffer
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memset(client_message, 0, sizeof(client_message));
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// store message history, for TAG calculation
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// msg on odd is msg, and on even is corresponding TAG
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vector<string> message_history;
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// Receive client's message
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while (1)
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{
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// clean exising buffer
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memset(client_message, 0, sizeof(client_message));
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ssize_t n = recv(client_socket, client_message, sizeof(client_message), 0);
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if (n == 0)
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break;
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if (n < 0)
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{
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perror("recv");
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break;
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}
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if (strcmp((char *)client_message, "\\exit\n") == 0)
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break;
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printf("Msg from client: %s \n", byte_to_hex((unsigned char *)client_message, n));
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// store message history for TAG calculation
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message_history.push_back(string((char *)client_message, n));
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// only respond after receiving both msg and TAG
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if (message_history.size() % 2 == 1)
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continue;
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// check TAG
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const string tag_str = message_history.back();
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unsigned char tag[16];
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memcpy(tag, tag_str.c_str(), 16);
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const string ciphertext_str = message_history[message_history.size() - 2];
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char ciphertext_cstr[2048];
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strcpy(ciphertext_cstr, ciphertext_str.c_str());
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unsigned char plaintext[2048];
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memset(plaintext, 0, sizeof(plaintext));
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int plaintext_len = gcm_decrypt((unsigned char *)ciphertext_cstr,
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strlen(ciphertext_cstr),
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(unsigned char *)add,
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strlen(add),
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tag,
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key_bytes,
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iv_bytes,
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16,
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plaintext);
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if (plaintext_len == 0)
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{
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fprintf(stderr, "TAG mismatch or invalid message\n");
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memcpy(server_message, custom_message_failed, strlen(custom_message_failed));
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;
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}
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else
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{
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fprintf(stderr, "Decryption success\n, decrypted message: %s\n", plaintext);
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memcpy(server_message, custom_message_success, strlen(custom_message_success));
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;
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}
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// Respond to client
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// prepare server message
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size_t reply_len = strlen(server_message);
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if (send(client_socket, server_message, reply_len, 0) == -1)
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{
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perror("Send failed");
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break;
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}
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printf("Response sent to client: %s\n", server_message);
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}
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// Close the socket
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close(client_socket);
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close(server_socket);
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return 0;
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}
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