使用 libssh 编写 client
1. 使用 libssh 编写客户端程序
#include <libssh/libssh.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
int verify_knownhost(ssh_session session);
char *getpass(const char *str);
int show_remote_processes(ssh_session session);
int main()
{
ssh_session my_ssh_session;
//int verbosity = SSH_LOG_PROTOCOL;
int port = 22;
int rc;
char *password;
/* Creating the session and setting options */
my_ssh_session = ssh_new();
if (my_ssh_session == NULL) {
exit(-1);
}
ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, "localhost");
//ssh_options_set(my_ssh_session, SSH_OPTIONS_LOG_VERBOSITY, &verbosity);
ssh_options_set(my_ssh_session, SSH_OPTIONS_PORT, &port);
ssh_options_set(my_ssh_session, SSH_OPTIONS_USER, "likui");
/* Connecting to the server */
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);
}
/* Authenticating the server */
if (verify_knownhost(my_ssh_session) < 0) {
ssh_disconnect(my_ssh_session);
ssh_free(my_ssh_session);
exit(-1);
}
/* Authenticate ourselves */
password = getpass("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);
}
/************************/
fprintf(stderr, "connect success!\n");
show_remote_processes(my_ssh_session);
/************************/
ssh_disconnect(my_ssh_session);
ssh_free(my_ssh_session);
exit(0);
}
char *getpass(const char *str)
{
static char password[64];
int index;
fprintf(stdout, "%s", str);
if (fgets(password, sizeof(password), stdin) == NULL) {
fprintf(stderr, "fgets error\n");
return NULL;
}
index = strlen(password) - 1;
if (password[index] == '\n') {
password[index] = '\0';
}
return password;
}
/* Authenticating the server */
int verify_knownhost(ssh_session session)
{
int state, hlen;
unsigned char *hash = NULL;
char *hexa;
char buf[10];
/* look into the known host file */
state = ssh_is_server_known(session);
/* get a binary version of the public key hash value */
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");
/* fallback to SSH_SERVER_NOT_KNOWN */
case SSH_SERVER_NOT_KNOWN:
/* Convert a buffer into a colon separated hex string */
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 (strncasecmp(buf, "yes", 3) != 0) {
free(hash);
return -1;
}
/* register it in the known hosts file */
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;
/* Allocate a new channel */
channel = ssh_channel_new(session);
if (channel == NULL) {
return SSH_ERROR;
}
/* Open session channel */
rc = ssh_channel_open_session(channel);
if (rc != SSH_OK) {
ssh_channel_free(channel);
return rc;
}
/* Run a shell command without an interactive shell */
rc = ssh_channel_request_exec(channel, "pwd");
if (rc != SSH_OK) {
ssh_channel_close(channel);
ssh_channel_free(channel);
return rc;
}
/* Reads data from a channel */
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;
}
/* Send an end of file on the channel */
ssh_channel_send_eof(channel);
/* Close a channel */
ssh_channel_close(channel);
/* Close and free a channel */
ssh_channel_free(channel);
return SSH_OK;
}
2. 编译
gcc client.c -o client -Wall -lssh
参考资料
http://api.libssh.org/master/libssh_tutorial.html
http://blog.csdn.net/vevenlcf/article/details/43273457