Here I describe some first steps for using libssh on an old setup (WinXP with Visual Studio 2008). I think steps for other platforms are more or less similar.
OpenSSL:
Win32OpenSSL-1_0_2m.exe from http://slproweb.com/products/Win32OpenSSL.html
-> Install it.
zlib123dll.zip from http://www.winimage.com/zLibDll/
zlibwapi.dll renamed to zlib1.dll
-> I placed it into my working directory.
libssh-0.7.2-msvc.zip from https://red.libssh.org/projects/libssh/files
-> files placed into c:\Programme\Microsoft Visual Studio 9.0\VC in my case
Now everything is ready for running a simple example. It is a client that executes a command on a ssh server (a Kali box here):
#include <libssh/libssh.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
int verify_knownhost(ssh_session session)
{
int state, hlen;
unsigned char *hash = NULL;
char *hexa;
char buf[10];
state = ssh_is_server_known(session);
hlen = ssh_get_pubkey_hash(session, &hash);
if (hlen < 0)
return -1;
switch (state)
{
case SSH_SERVER_KNOWN_OK:
break;
case SSH_SERVER_KNOWN_CHANGED:
fprintf(stderr, "Host key for server changed: it is now:\n");
ssh_print_hexa("Public key hash", hash, hlen);
fprintf(stderr, "For security reasons, connection will be stopped\n");
free(hash);
return -1;
case SSH_SERVER_FOUND_OTHER:
fprintf(stderr, "The host key for this server was not found but an other"
"type of key exists.\n");
fprintf(stderr, "An attacker might change the default server key to"
"confuse your client into thinking the key does not exist\n");
free(hash);
return -1;
case SSH_SERVER_FILE_NOT_FOUND:
fprintf(stderr, "Could not find known host file.\n");
fprintf(stderr, "If you accept the host key here, the file will be"
"automatically created.\n");
case SSH_SERVER_NOT_KNOWN:
hexa = ssh_get_hexa(hash, hlen);
fprintf(stderr,"The server is unknown. Do you trust the host key?\n");
fprintf(stderr, "Public key hash: %s\n", hexa);
free(hexa);
if (fgets(buf, sizeof(buf), stdin) == NULL)
{
free(hash);
return -1;
}
if (strncmp(buf, "yes", 3) != 0)
{
free(hash);
return -1;
}
if (ssh_write_knownhost(session) < 0)
{
fprintf(stderr, "Error %s\n", strerror(errno));
free(hash);
return -1;
}
break;
case SSH_SERVER_ERROR:
fprintf(stderr, "Error %s", ssh_get_error(session));
free(hash);
return -1;
}
free(hash);
return 0;
}
int show_remote_processes(ssh_session session)
{
ssh_channel channel;
int rc;
char buffer[256];
int nbytes;
channel = ssh_channel_new(session);
if (channel == NULL)
return SSH_ERROR;
rc = ssh_channel_open_session(channel);
if (rc != SSH_OK)
{
ssh_channel_free(channel);
return rc;
}
rc = ssh_channel_request_exec(channel, "ps aux");
if (rc != SSH_OK)
{
ssh_channel_close(channel);
ssh_channel_free(channel);
return rc;
}
nbytes = ssh_channel_read(channel, buffer, sizeof(buffer), 0);
while (nbytes > 0)
{
if (write(1, buffer, nbytes) != (unsigned int) nbytes)
{
ssh_channel_close(channel);
ssh_channel_free(channel);
return SSH_ERROR;
}
nbytes = ssh_channel_read(channel, buffer, sizeof(buffer), 0);
}
if (nbytes < 0)
{
ssh_channel_close(channel);
ssh_channel_free(channel);
return SSH_ERROR;
}
ssh_channel_send_eof(channel);
ssh_channel_close(channel);
ssh_channel_free(channel);
return SSH_OK;
}
int main()
{
ssh_session my_ssh_session;
int rc;
char *password;
my_ssh_session = ssh_new();
if (my_ssh_session == NULL)
exit(-1);
ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, "192.168.153.149");
ssh_options_set(my_ssh_session, SSH_OPTIONS_USER, "root");
rc = ssh_connect(my_ssh_session);
if (rc != SSH_OK)
{
fprintf(stderr, "Error connecting to localhost: %s\n",
ssh_get_error(my_ssh_session));
ssh_free(my_ssh_session);
exit(-1);
}
if (verify_knownhost(my_ssh_session) < 0)
{
ssh_disconnect(my_ssh_session);
ssh_free(my_ssh_session);
exit(-1);
}
password = "";
rc = ssh_userauth_password(my_ssh_session, NULL, password);
if (rc != SSH_AUTH_SUCCESS)
{
fprintf(stderr, "Error authenticating with password: %s\n",
ssh_get_error(my_ssh_session));
ssh_disconnect(my_ssh_session);
ssh_free(my_ssh_session);
exit(-1);
}
show_remote_processes(my_ssh_session);
ssh_disconnect(my_ssh_session);
ssh_free(my_ssh_session);
}
Compile with:
cl test.c /link ssh.lib
Output:
E:\>test
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.3 139204 6352 ? Ss Oct23 0:33 /sbin/init
root 2 0.0 0.0 0 0 ? S Oct23 0:00 [kthreadd]
root 3 0.0 0.0 0 0 ? S Oct23 0:01 [ksoftirqd/0]
root 5 0.0 0.0 0 0 ? S< Oct23 0:00 [kworker/0:0H]
root 7 0.0 0.0 0 0 ? S Oct23 0:19 [rcu_sched]
root 8 0.0 0.0 0 0 ? S Oct23 0:00 [rcu_bh]
root 9 0.0 0.0 0 0 ? S Oct23 0:01 [migration/0]
root 10 0.0 0.0 0 0 ? S< Oct23 0:00 [lru-add-drain]
...
The code comes from the tutorial:
http://api.libssh.org/master/libssh_tutorial.html
