Trivial TLS client

David Howells
2023-03-31T16:33:56Z

Here's a trivial TLS client program for testing this.

David
---
/*
* TLS-over-TCP send client
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <sys/stat.h>
#include <sys/sendfile.h>
#include <linux/tls.h>

#define OSERROR(X, Y) do { if ((long)(X) == -1) { perror(Y); exit(1); } } while(0)

static unsigned char buffer[4096] __attribute__((aligned(4096)));

static void set_tls(int sock)
{
struct tls12_crypto_info_aes_gcm_128 crypto_info;

crypto_info.info.version = TLS_1_2_VERSION;
crypto_info.info.cipher_type = TLS_CIPHER_AES_GCM_128;
memset(crypto_info.iv, 0, TLS_CIPHER_AES_GCM_128_IV_SIZE);
memset(crypto_info.rec_seq, 0, TLS_CIPHER_AES_GCM_128_REC_SEQ_SIZE);
memset(crypto_info.key, 0, TLS_CIPHER_AES_GCM_128_KEY_SIZE);
memset(crypto_info.salt, 0, TLS_CIPHER_AES_GCM_128_SALT_SIZE);

OSERROR(setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls")),
"TCP_ULP");
OSERROR(setsockopt(sock, SOL_TLS, TLS_TX, &crypto_info, sizeof(crypto_info)),
"TLS_TX");
OSERROR(setsockopt(sock, SOL_TLS, TLS_RX, &crypto_info, sizeof(crypto_info)),
"TLS_RX");
}

int main(int argc, char *argv[])
{
struct sockaddr_in sin = { .sin_family = AF_INET, .sin_port = htons(5556) };
struct hostent *h;
struct stat st;
ssize_t r, o;
int sf = 0;
int cfd, fd;

if (argc > 1 && strcmp(argv[1], "-s") == 0) {
sf = 1;
argc--;
argv++;
}

if (argc != 3) {
fprintf(stderr, "tcp-send [-s] <server> <file>\n");
exit(2);
}

h = gethostbyname(argv[1]);
if (!h) {
fprintf(stderr, "%s: %s\n", argv[1], hstrerror(h_errno));
exit(3);
}

if (!h->h_addr_list[0]) {
fprintf(stderr, "%s: No addresses\n", argv[1]);
exit(3);
}

memcpy(&sin.sin_addr, h->h_addr_list[0], h->h_length);

cfd = socket(AF_INET, SOCK_STREAM, 0);
OSERROR(cfd, "socket");
OSERROR(connect(cfd, (struct sockaddr *)&sin, sizeof(sin)), "connect");
set_tls(cfd);

fd = open(argv[2], O_RDONLY);
OSERROR(fd, argv[2]);
OSERROR(fstat(fd, &st), argv[2]);

if (!sf) {
for (;;) {
r = read(fd, buffer, sizeof(buffer));
OSERROR(r, argv[2]);
if (r == 0)
break;

o = 0;
do {
ssize_t w = write(cfd, buffer + o, r - o);
OSERROR(w, "write");
o += w;
} while (o < r);
}
} else {
off_t off = 0;
r = sendfile(cfd, fd, &off, st.st_size);
OSERROR(r, "sendfile");
if (r != st.st_size) {
fprintf(stderr, "Short sendfile\n");
exit(1);
}
}

OSERROR(close(cfd), "close/c");
OSERROR(close(fd), "close/f");
return 0;
}