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ssl-server-tier1.c
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ssl-server-tier1.c
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/******************************************************************************
PROGRAM: ssl-server-tier1.c
AUTHOR: Omar Castorena
COURSE: CS469 - Distributed Systems (Regis University)
SYNOPSIS: This program is a small server application that receives incoming TCP
connections from clients, then establishes an SSL/TLS encrypted
connection to a tier 2 server. It receives a message from the other
server and passes it back to the client. The secure SSL/TLS
connection is created using certificates generated with the
openssl application. The purpose is to demonstrate how to establish
secure communication between a client and server using public key
cryptography in a multi-tier server architecture.
Some of the code and descriptions can be found in "Network Security
with OpenSSL", O'Reilly Media, 2002.
******************************************************************************/
#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <arpa/inet.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include "server-tools.h"
#include "client-tools.h"
#define BUFFER_SIZE 256
int main(int argc, char **argv) {
struct sockaddr_in addr;
char client_addr[INET_ADDRSTRLEN];
char buffer[BUFFER_SIZE];
char remote_server[MAX_HOSTNAME_LENGTH];
char c;
unsigned int len = sizeof(addr);
unsigned int sockfd;
unsigned int port = DEFAULT_PORT;
unsigned int remote_server_port = DEFAULT_PORT;
SSL* clientssl;
SSL* server2ssl;
int clientsd;
int server2sd;
pid_t pid;
// Do not create zombie processes
signal(SIGCHLD, SIG_IGN);
init_openssl();
// Port can be specified on the command line. If it's not, use the default port
while((c = getopt(argc, argv, "o:p:s:")) != -1)
switch(c)
{
case 'p':
port = atoi(optarg);
break;
case 's':
strcpy(remote_server, optarg);
break;
case 'o':
remote_server_port = atoi(optarg);
break;
default:
fprintf(stderr, "Usage: ssl-server-tier1 -p <port> (optional) -s <remote server name/IP address> -o <remote server port>\n");
return EXIT_FAILURE;
}
// This will create a network socket and return a socket descriptor, which is
// and works just like a file descriptor, but for network communcations. Note
// we have to specify which TCP/UDP port on which we are communicating as an
// argument to our user-defined create_socket() function.
sockfd = create_socket(port);
// Wait for incoming connections and handle them as the arrive
while(true) {
// Once an incoming connection arrives, accept it. If this is successful,
// we now have a connection between client and server and can communicate
// using the socket descriptor
clientsd = accept(sockfd, (struct sockaddr*)&addr, &len);
if (clientsd < 0) {
fprintf(stderr, "Server: Unable to accept connection: %s\n", strerror(errno));
return EXIT_FAILURE;
}
// This will be a concurrent, rather than an iterative, server
pid = fork();
if (pid == 0) {
// Display the IPv4 network address of the connected client
inet_ntop(AF_INET, (struct in_addr*)&addr.sin_addr, client_addr, INET_ADDRSTRLEN);
fprintf(stdout, "Server: Established TCP connection with client (%s) on port %u\n", client_addr, port);
// Create a new SSL object to bind to the socket descriptor
clientssl = create_ssl_socket(clientsd);
// SSL_accept() executes the SSL/TLS handshake. Because network sockets
// are blocking by default, this function will block as well until the
// handshake is complete.
if (SSL_accept(clientssl) <= 0) {
fprintf(stderr, "Server: Could not establish secure connection:\n");
ERR_print_errors_fp(stderr);
}
else
fprintf(stdout, "Server: Established SSL/TLS connection with client (%s)\n", client_addr);
// This is where the server establishes a connection with another server
server2sd = create_client_socket(remote_server, remote_server_port);
server2ssl = create_client_ssl_socket(server2sd);
if (SSL_connect(server2ssl) == 1) {
printf("Server: Established SSL/TLS session to '%s' on port %u\n",
"localhost", remote_server_port);
} else {
fprintf(stderr, "Server: Could not establish SSL session to '%s' on port %u\n", remote_server, remote_server_port);
exit(EXIT_FAILURE);
}
//**************************************************************************
char delim[] = "/";
char eq[] = "=";
char movie[20], location[20], date[20], time[20], type[20];
int count = 1;
char query[BUFFER_SIZE] = "SELECT * FROM movie_times";
char where[BUFFER_SIZE] = " WHERE ";
int where_count = 0;
int nbytes_read;
bzero(buffer, BUFFER_SIZE);
SSL_read(clientssl, buffer, BUFFER_SIZE);
printf("Message from client: %s\n", buffer);
char *ptr = strtok(buffer, delim);
while(ptr != NULL){
if (count == 1) {
strcpy(movie, ptr);
}
if (count == 2) {
strcpy(location, ptr);
}
if (count == 3) {
strcpy(date, ptr);
}
if (count == 4) {
strcpy(time, ptr);
}
ptr = strtok(NULL, delim);
count = count + 1;
}
bzero(buffer, BUFFER_SIZE);
if (strcmp(movie, "name = ''") != 0) {
strcat(where, movie);
where_count = where_count + 1;
}
if (strcmp(location, "location = ''") != 0) {
if (where_count >= 1) {
strcat(where, " AND ");
}
strcat(where, location);
where_count = where_count + 1;
}
if (strcmp(date, "date = ''") != 0) {
if (where_count >= 1) {
strcat(where, " AND ");
}
strcat(where, date);
where_count = where_count + 1;
}
if (strcmp(time, "time = ''") != 0) {
if (where_count >= 1) {
strcat(where, " AND ");
}
strcat(where, time);
where_count = where_count + 1;
}
if (where_count != 0) {
strcat(query, where);
}
printf("Server: Sending query to database:\n%s\n", query);
SSL_write(server2ssl, query, strlen(query)+1);
bzero(buffer, BUFFER_SIZE);
//**************************************************************************
// Receive response back from other server that it will pass to the client
while (1) {
nbytes_read = SSL_read(server2ssl, buffer, BUFFER_SIZE);
if (nbytes_read < 0) {
fprintf(stderr, "Server: Error reading from socket: %s\n", strerror(errno));
break;
}
if (strcmp(buffer, "NO RESULTS") == 0)
{
fprintf(stderr, "Server: No results\n");
break;
}
if (strcmp(buffer, "DONE") == 0)
{
fprintf(stderr, "Server: The query has been recieved successfully\n");
break;
}
printf("Server: Received message from database:\n%s\n", buffer);
SSL_write(clientssl, buffer, strlen(buffer)+1);
bzero(buffer, BUFFER_SIZE);
}
printf("Server: Sending result to client (%s)\n", client_addr);
// Server sends the message to the client
SSL_write(clientssl, buffer, strlen(buffer)+1);
// Terminate the SSL session, close the TCP connection, and clean up
fprintf(stdout, "Server: Terminating SSL session and TCP connection with client (%s)\n", client_addr);
SSL_free(clientssl);
close(clientsd);
} // Child process code ends here. Parent just resumes listening
}
// Tear down and clean up server data structures before terminating
close(sockfd);
return EXIT_SUCCESS;
}