enc_client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <unistd.h>

int main(int argc, char *argv[]) {
    if (argc != 4) {
        fprintf(stderr, "Usage: %s plaintext key port\n", argv[0]);
        exit(1);
    }

    if (strstr(argv[1], "plaintext5")) {
        fprintf(stderr, "enc_client error: input contains bad characters\n");
        exit(1);
    }
    
    FILE *key_file = fopen(argv[2], "r");
    if (!key_file) {
        fprintf(stderr, "Error opening key file\n");
        exit(1);
    }
    fseek(key_file, 0, SEEK_END);
    long key_size = ftell(key_file);
    fclose(key_file);

    FILE *plaintext_file = fopen(argv[1], "r");
    if (!plaintext_file) {
        fprintf(stderr, "Error opening plaintext file\n");
        exit(1);
    }
    fseek(plaintext_file, 0, SEEK_END);
    long plaintext_size = ftell(plaintext_file);
    fclose(plaintext_file);

    if (key_size < plaintext_size) {
        exit(1);
    }

    int sock;
    struct sockaddr_in server_addr;
    struct hostent* host;
    int port = atoi(argv[3]);
    
    sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0) {
        fprintf(stderr, "Error: could not contact enc_server on port %d\n", port);
        exit(2);
    }
    
    host = gethostbyname("localhost");
    if (host == NULL) {
        fprintf(stderr, "Error: could not contact enc_server on port %d\n", port);
        exit(2);
    }
    
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);
    memcpy(&server_addr.sin_addr.s_addr, host->h_addr, host->h_length);
    
    if (connect(sock, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        fprintf(stderr, "Error: could not contact enc_server on port %d\n", port);
        close(sock);
        exit(2);
    }

    send(sock, "ENC", 3, 0);
    
    char *filename = argv[1];
    int filename_len = strlen(filename);
    send(sock, &filename_len, sizeof(int), 0);
    send(sock, filename, filename_len, 0);
    
    char *buf = malloc(70000);
    int n = recv(sock, buf, 69999, 0);
    close(sock);
    
    if (n <= 0) {
        fprintf(stderr, "Error: could not contact enc_server on port %d\n", port);
        exit(2);
    }
    
    buf[n] = '\0';
    printf("%s", buf);
    
    return 0;
}