ssh_channel_read_nonblocking( ) just echoback the given command? - c

Question

I am trying to implement an ssh client using libssh but output seems to just be an echo of whatever been sent main part of program is :
do {
printf("Enter Command or q to exit: ");
fgets(command, 100, stdin);
command[strlen(command)-1] = 0;
if (ssh_channel_write(channel, command, strlen(command)) != strlen(command)) {
fprintf(stderr, "Unable to execute command\n");
exit(1);
}
printf("Data Sent: %s\n", command);
sleep(1);
while ((bytes_recieved = ssh_channel_read_nonblocking(channel, output, 2024, 0))) {
if (bytes_recieved < 1) {
fprintf(stderr, "Error Reading Output or End Of Data\n");
break;
}
printf("Data Recieved(%d): %.*s\n", bytes_recieved, bytes_recieved, output);
}
}while (strcmp(command, "q")!=0 ||strcmp(command, "Q")!=0 );
first command result in what I guess the banner to be sent althought I guess the banner is supposed to be sent before connection , this is output for only the first command after that anything i type is just echod back.
Welcome to Ubuntu 20.04 LTS (GNU/Linux 5.4.0-40-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
* "If you've been waiting for the perfect Kubernetes dev solution for
macOS, the wait is over. Learn how to install Microk8s on macOS."
https://www.techrepublic.com/article/how-to-install-microk8s-on-macos/
65 updates can be installed immediately.
0 of these updates are security updates.
To see these additional updates run: apt list --upgradable
Your Hardware Enablement Stack (HWE) is supported until April 2025.
sshd_config files (server side) have been edited to include this as highlights:
AllowTcpForwarding no
PasswordAuthentication yes
PermitRootLogin prohibit-password
AllowUsers user_name
Whole code is here for anyone if he want's to use or test on it just change your username in ssh_options_set( ) part of the code.
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <libssh/libssh.h>
int main(int argc, char* argv[])
{
printf("libssh version: %s\n", ssh_version(0));
if (argc < 2){
fprintf(stderr, "USAGE command hostname\n");
exit(1);
}
char* hostname = argv[1];
int port = 22;
ssh_session ssh = ssh_new();
ssh_options_set(ssh, SSH_OPTIONS_HOST, hostname);
ssh_options_set(ssh, SSH_OPTIONS_PORT, &port);
// TODO: Enable it in the future
int verbosity = SSH_LOG_PROTOCOL;
ssh_options_set(ssh, SSH_OPTIONS_LOG_VERBOSITY, &verbosity);
int error_code = ssh_connect(ssh);
if (error_code != SSH_OK){
fprintf(stderr, "Error creating connection with error %d", error_code);
exit(1);
}
printf("Connected to %s on port %d.\n", hostname, port);
printf("banner %s\n", ssh_get_serverbanner(ssh));
ssh_key key;
if(ssh_get_server_publickey(ssh, &key) != SSH_OK) {
fprintf(stderr,"Couldnt get server key\n");
exit(1);
}
unsigned char* hash;
size_t hash_len;
if(ssh_get_publickey_hash(key, SSH_PUBLICKEY_HASH_SHA1, &hash, &hash_len)!=SSH_OK){
fprintf(stderr, "Error Calculating Hash\n");
exit(1);
}
printf("Host public key hash:\n");
ssh_print_hash(SSH_PUBLICKEY_HASH_SHA1, hash, hash_len);
ssh_key_free(key);
ssh_clean_pubkey_hash(&hash);
enum ssh_known_hosts_e known = ssh_session_is_known_server(ssh);
switch (known) {
case SSH_KNOWN_HOSTS_OK:printf("known Host\n");break;
case SSH_KNOWN_HOSTS_NOT_FOUND:printf("no host file\n");break;
case SSH_KNOWN_HOSTS_CHANGED:printf("Host Changed\n");break;
case SSH_KNOWN_HOSTS_ERROR:
printf("Host error. %s\n", ssh_get_error(ssh)); return 1;
case SSH_KNOWN_HOSTS_UNKNOWN: printf("Unknown Host verify please\n");break;
}
if(known == SSH_KNOWN_HOSTS_CHANGED){
printf("Server key changed Exiting\n");
exit(1);
}
if (
known == SSH_KNOWN_HOSTS_OTHER ||
known == SSH_KNOWN_HOSTS_UNKNOWN ||
known == SSH_KNOWN_HOSTS_NOT_FOUND)
{
printf("Do you want to trust this host\n");
char answer[10];
fgets(answer, 10, stdin);
if(answer[0] == 'y' || answer[0] == 'Y'){
ssh_session_update_known_hosts(ssh);
}else{
printf("Not trusting it\n");
exit(1);
}
}
ssh_options_set(ssh, SSH_OPTIONS_USER, "my_user");
printf("Enter password: ");
char pass[20];
fgets(pass, 20, stdin);
pass[strlen(pass)-1] = 0 ;
if(ssh_userauth_password(ssh, 0, pass) != SSH_AUTH_SUCCESS){
fprintf(stderr, "Unable to Authentication\n");
exit(1);
}else {
printf("Authentication successful!\n");
}
int err = ssh_userauth_publickey_auto(ssh, NULL, NULL);
if (err == SSH_AUTH_ERROR){
fprintf(stderr, "Unable to Authunticate\n");
exit(1);
}
ssh_channel channel = ssh_channel_new(ssh);
if(!channel){
fprintf(stderr, "Couldnt create a channel\n");
exit(1);
}
if(ssh_channel_open_session(channel) != SSH_OK){
fprintf(stderr, "Error Openning Session\n");
exit(1);
}
if (ssh_channel_request_pty(channel) != SSH_OK){
fprintf(stderr, "Can't initiate terminal\n");
exit(1);
}
if(ssh_channel_change_pty_size(channel, 80, 400) != SSH_OK){
fprintf(stderr, "Error Changing size of terminal\n");
exit(1);
}
if(ssh_channel_request_shell(channel) != SSH_OK){
fprintf(stderr, "Couldn't request a shell\n");
exit(1);
}
char command[100];
char output[2024];
int bytes_recieved;
do {
printf("Enter Command or q to exit: ");
fgets(command, 100, stdin);
command[strlen(command)-1] = 0;
if (ssh_channel_write(channel, command, strlen(command)) != strlen(command)) {
fprintf(stderr, "Unable to execute command\n");
exit(1);
}
printf("Data Sent: %s\n", command);
sleep(1);
while ((bytes_recieved = ssh_channel_read_nonblocking(channel, output, 2024, 0))) {
if (bytes_recieved < 1) {
fprintf(stderr, "Error Reading Output or End Of Data\n");
break;
}
printf("Data Recieved(%d): %.*s\n", bytes_recieved, bytes_recieved, output);
}
}while (strcmp(command, "q")!=0 ||strcmp(command, "Q")!=0 );
ssh_channel_send_eof(channel);
ssh_channel_close(channel);
ssh_channel_free(channel);
ssh_disconnect(ssh);
ssh_free(ssh);
return 0;
}