openSSL C program - c

Question

I wrote a program to send the contents of a file between a computer and a raspberry pi 4; on localhost it works but when I try it between the two hosts it does not work.
The output is "Send Success, NumBytes = 7" from the sender part and "Receive Success, NumBytes = 0" from the receiver part.
I created the certificate following this guide: https://www.simba.com/products/SEN/doc/Client-Server_user_guide/content/clientserver/configuringssl/signingca.htm
sender.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include "transfer.h"
#include <openssl/ssl.h>
void sendfile(FILE *fp, SSL *ssl);
ssize_t total = 0;
SSL_CTX *ctx;
int main(int argc, char *argv[])
{
SSL *ssl;
if (argc != 3)
{
perror("usage:send_file filepath <IPaddress>");
exit(1);
}
SSL_library_init();
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
{
perror("Can't allocate sockfd");
exit(1);
}
if ((ctx = SSL_CTX_new(SSLv23_client_method())) == NULL)
{
fprintf(stderr, "ERROR: failed to create SSL_CTX\n");
return -1;
}
SSL_CTX_set_options(ctx,SSL_OP_NO_TLSv1_3);
if (SSL_CTX_load_verify_locations(ctx, "./certs/CA-cert.pem", 0) != 1)
{
fprintf(stderr, "Error loading ./certs/cacert.pem, please check the file.\n");
exit(EXIT_FAILURE);
}
struct sockaddr_in serveraddr;
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin_family = AF_INET;
serveraddr.sin_port = htons(SERVERPORT);
if (inet_pton(AF_INET, argv[2], &serveraddr.sin_addr) < 0)
{
perror("IPaddress Convert Error");
exit(1);
}
if (connect(sockfd, (const struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0)
{
perror("Connect Error");
exit(1);
}
if ((ssl = SSL_new(ctx)) == NULL)
{
fprintf(stderr, "ERROR: failed to create SSL object\n");
return -1;
}
/* Attach SSL to the socket */
SSL_set_fd(ssl, sockfd);
/* Connect to SSL on the server side */
if (SSL_connect(ssl) < 0)
{
fprintf(stderr, "ERROR: failed to connect to SSL\n");
return -1;
}
char *filename = basename(argv[1]);
if (filename == NULL)
{
perror("Can't get filename");
exit(1);
}
char buff[BUFFSIZE] = {0};
strncpy(buff, filename, strlen(filename));
if (send(sockfd, buff, BUFFSIZE, 0) == -1)
{
perror("Can't send filename");
exit(1);
}
FILE *fp = fopen(argv[1], "rb");
if (fp == NULL)
{
perror("Can't open file");
exit(1);
}
sendfile(fp, ssl);
//puts("Send Success");
printf("Send Success, NumBytes = %d\n", total);
fclose(fp);
close(sockfd);
SSL_free(ssl);
SSL_CTX_free(ctx);
return 0;
}
void sendfile(FILE *fp, SSL *ssl)
{
int n;
char sendline[MAX_LINE] = {0};
while ((n = fread(sendline, sizeof(char), MAX_LINE, fp)) > 0)
{
total += n;
if (n != MAX_LINE && ferror(fp))
{
perror("Read File Error");
exit(1);
}
if (SSL_write(ssl, sendline, strlen(sendline)) <= 0)
{
perror("Can't send file\n");
exit(1);
}
memset(sendline, 0, MAX_LINE);
}
}
receiver.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include "transfer.h"
#include <openssl/ssl.h>
void writefile(SSL *ssl, FILE *fp);
ssize_t total = 0;
int main(int argc, char *argv[])
{
SSL_CTX *ctx;
SSL *ssl;
SSL_library_init();
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1)
{
perror("Can't allocate sockfd");
exit(1);
}
ctx = SSL_CTX_new(SSLv23_method());
SSL_CTX_set_options(ctx, SSL_OP_NO_SSLv3);
if (ctx == NULL)
{
fprintf(stderr, "ERROR: failed to create SSL_CTX\n");
return -1;
}
if (SSL_CTX_load_verify_locations(ctx, "./certs/CA-cert.pem", 0) != 1)
{
fprintf(stderr, "Error loading ./certs/ca-cert.pem, please check the file.\n");
return -1;
}
if (SSL_CTX_use_certificate_file(ctx, "./certs/server-cert.pem", SSL_FILETYPE_PEM) != 1)
{
fprintf(stderr, "Error loading ./certs/servercert.pem, please check the file.\n");
return -1;
}
if (SSL_CTX_use_PrivateKey_file(ctx, "./certs/server-key.pem", SSL_FILETYPE_PEM) != 1)
{
fprintf(stderr, "Error loading ./certs/serverkey.pem, please check the file.\n");
return -1;
}
//SSL_CTX_set_options(ctx,SSL_OP_NO_TICKET);
struct sockaddr_in clientaddr, serveraddr;
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin_family = AF_INET;
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
serveraddr.sin_port = htons(SERVERPORT);
if (bind(sockfd, (const struct sockaddr *)&serveraddr, sizeof(serveraddr)) == -1)
{
perror("Bind Error");
exit(1);
}
if (listen(sockfd, LINSTENPORT) == -1)
{
perror("Listen Error");
exit(1);
}
socklen_t addrlen = sizeof(clientaddr);
int connfd = accept(sockfd, (struct sockaddr *)&clientaddr, &addrlen);
if (connfd == -1)
{
perror("Connect Error");
exit(1);
}
close(sockfd);
if ((ssl = SSL_new(ctx)) == NULL)
{
fprintf(stderr, "ERROR: failed to create SSL object\n");
return -1;
}
SSL_set_fd(ssl, connfd);
/* Establish TLS connection */
int ret = SSL_accept(ssl);
if (ret < 0)
{
fprintf(stderr, "SSL_accept error = %d\n", SSL_get_error(ssl, ret));
return -1;
}
char filename[BUFFSIZE] = {0};
if (recv(connfd, filename, BUFFSIZE, 0) == -1)
{
perror("Can't receive filename");
exit(1);
}
FILE *fp = fopen("output.txt", "wb");
if (fp == NULL)
{
perror("Can't open file");
exit(1);
}
char addr[INET_ADDRSTRLEN];
printf("Start receive file: %s from %s\n", filename, inet_ntop(AF_INET, &clientaddr.sin_addr, addr, INET_ADDRSTRLEN));
writefile(ssl, fp);
printf("Receive Success, NumBytes = %d\n", total);
SSL_free(ssl);
SSL_CTX_free(ctx);
fclose(fp);
close(connfd);
return 0;
}
void writefile(SSL *ssl, FILE *fp)
{
ssize_t n;
char buff[MAX_LINE] = {0};
clock_t t;
t = clock();
while ((n = SSL_read(ssl, buff, sizeof(buff))) > 0)
{
total += n;
if (n == -1)
{
perror("Receive File Error");
exit(1);
}
if (fwrite(buff, sizeof(char), n, fp) != n)
{
perror("Write File Error");
exit(1);
}
memset(buff, 0, MAX_LINE);
}
t = clock() - t;
double time_taken = ((double)t)/CLOCKS_PER_SEC; // in seconds
printf("%f seconds to receive data \n", time_taken);
}
Thanks

Answer 1

The receiver calls recv() on connfd after this file descriptor has been given to the ssl connection, so there is nothing more to be read on the ssl connection.