使用libssh链接远程ssh服务器并执行command

看到段牛牛和大湿聊了一下批量ssh的东西，然后看到有个ssh的程序，

挺有意思，学习一下，然后实现了一下，记录下来了

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <libssh/libssh.h>


int show_remote_processes(ssh_session session, unsigned char *command)
{
    ssh_channel channel;
    int rc;
    char buffer[256];
    unsigned 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, command);
    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) != 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 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; /* ok */

        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 behavior */

        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 (strncasecmp(buf, "yes", 3) != 0)
            {
                free(hash);
                return -1;
            }
            if (ssh_write_knownhost(session) < 0)
            {
                fprintf(stderr, "Error %s\n", "error");
                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;
}


static int ssh_connect_test(unsigned char *ipaddr, unsigned char *command)
{
    int rc = 0;
    char *password;
    ssh_session my_ssh_session = ssh_new();

    if (!my_ssh_session) {
        fprintf(stderr, "cannot alloc new ssh\r\n");
        return -1;
    }
    ssh_options_set(my_ssh_session, SSH_OPTIONS_HOST, ipaddr);

    rc = ssh_connect(my_ssh_session);
    if (rc != SSH_OK)
    {
        fprintf(stderr, "Error connecting to localhost: %s\n", ssh_get_error(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 = "passwordsamples";
    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, command);

    fprintf(stderr, "alloc success\r\n");
    ssh_free(my_ssh_session);
    return 0;
}

int main(int argc, char *argv[])
{
    int ret = 0;
    ret = ssh_connect_test(argv[1], argv[2]);
    if (ret < 0) {
        fprintf(stderr, "connect error \r\n");
        return -1;
    }
    return 0;
}

Makefile如下

CFLAGS    += -Werror -I/usr/local/include -L/usr/local/lib

CC        =gcc
LIBS    = -lssh

OBJS    += \
           1.o
TARGET    = target
all:$(OBJS)
    gcc $(CFLAGS) -o $(TARGET) $(OBJS) $(LIBS)

clean:
    rm -rf $(OBJS) $(TARGET)

然后直接make即可生成可执行文件target

然后执行效果如下

[liuqi@btg example_libssh]$ ./target 192.168.0.118 date
2011年 06月 13日 星期一 14:07:04 CST
alloc success
[liuqi@btg example_libssh]$ ./target 192.168.0.118 who
liuqi    tty1         2011-06-13 10:28 (:0)
liuqi    pts/0        2011-06-13 10:29 (:0.0)
liuqi    pts/1        2011-06-13 10:29 (:0.0)
liuqi    pts/2        2011-06-13 13:54 (:0.0)
liuqi    pts/3        2011-06-13 14:02 (:0.0)
alloc success
[liuqi@btg example_libssh]$