init
This commit is contained in:
Zheyuan Wu
246
client.cpp
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246
client.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> // error handling
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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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#include "helper.h"
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// GCM encryption
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int gcm_encrypt(unsigned char *plaintext, int plaintext_len,
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unsigned char *aad, int aad_len,
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unsigned char *key,
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unsigned char *iv, int iv_len,
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unsigned char *ciphertext,
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unsigned char *tag)
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{
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EVP_CIPHER_CTX *ctx;
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int len, ciphertext_len;
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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 encryption operation. */
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if (!EVP_EncryptInit_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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/*
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* Set IV length if default 12 bytes (96 bits) is not appropriate
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*/
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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_EncryptInit_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_EncryptUpdate(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 encrypted, and obtain the encrypted
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output.
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* EVP_EncryptUpdate can be called multiple times if necessary
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*/
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if (!EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_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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ciphertext_len = len;
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/*
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* Finalize the encryption. Normally ciphertext bytes may be written at
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* this stage, but this does not occur in GCM mode
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*/
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if (!EVP_EncryptFinal_ex(ctx, ciphertext + len, &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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ciphertext_len += len;
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/* Get the tag */
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if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_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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/* Clean up */
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EVP_CIPHER_CTX_free(ctx);
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return ciphertext_len;
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}
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int main(void)
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{
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load_env(".env");
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// Declare variables
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const char *server_ip = std::getenv("SERVER_IP");
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const int server_port = std::atoi(std::getenv("SERVER_PORT"));
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printf("Connecting to server %s:%d\n", server_ip, server_port);
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char client_message[1024];
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char server_message[1024];
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const char *custom_message = "Zheyuan Wu: ";
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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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int client_socket = socket(AF_INET, SOCK_STREAM, 0);
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if (client_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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else
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{
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printf("Socket created successfully\n");
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}
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// Send connection request to server, be sure to set por tand IP the same as server-side
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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 (connect(client_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1)
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{
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perror("Failed to connect to server");
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close(client_socket);
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return 1;
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}
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else
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{
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printf("Connected to server successfully\n");
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}
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// Get input from the user:
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printf("Enter message sent to the server (type \\quit to exit): ");
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// clean the buffer
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memset(client_message, 0, sizeof(client_message));
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if (fgets(client_message, sizeof(client_message), stdin) == NULL)
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{
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// EOF or error reading from stdin, exit the loop
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perror("Error reading from stdin");
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return 1;
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}
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while (strcmp(client_message, "\\quit\n") != 0)
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{
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// Send the message to server:
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// add my name in the front
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char buffer[2048];
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std::snprintf(buffer, sizeof(buffer), "%s%s", custom_message, client_message);
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printf("Message sent to server: %s, length: %d \n", buffer, (int)strlen(buffer));
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unsigned char tag[16] = {0};
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unsigned char cipher_text[2048] = {0};
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int cipher_text_len = gcm_encrypt((unsigned char *)buffer,
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(int)strlen(buffer),
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(unsigned char *)add,
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(int)strlen(add),
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key_bytes,
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iv_bytes,
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iv_len,
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cipher_text,
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tag);
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printf("Ciphertext sent to server: %s\n", byte_to_hex(cipher_text, cipher_text_len));
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ssize_t sent = send(client_socket, cipher_text, cipher_text_len, 0);
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if (sent <= 0)
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{
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perror("No message sent to server");
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break;
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}
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sleep(1);
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// send tag of the message
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printf("TAG sent to server: %s\n", byte_to_hex(tag, 16));
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ssize_t sent_tag = send(client_socket, tag, 16, 0);
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if (sent_tag <= 0)
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{
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perror("No TAG sent to server");
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break;
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}
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// Receive the server's response:
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// add terminator for string
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ssize_t recvd = recv(client_socket, server_message, sizeof(server_message) - 1, 0);
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if (recvd <= 0)
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{
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perror("No message received from server");
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break;
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}
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server_message[recvd] = '\0';
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printf("Server's response: %s\n", server_message);
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printf("Enter message sent to the server (type \\quit to exit): ");
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// clean the buffer
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memset(client_message, 0, sizeof(client_message));
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memset(server_message, 0, sizeof(server_message));
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if (fgets(client_message, sizeof(client_message), stdin) == NULL)
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{
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// EOF or error reading from stdin, exit the loop
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perror("Error reading from stdin");
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break;
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}
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}
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// Close the socket
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close(client_socket);
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return 0;
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}
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