libssh2的简单应用
来源:互联网 发布:网络禁书40本 编辑:程序博客网 时间:2024/05/29 03:15
libssh2的官网:www.libssh2.org; 这里面提供了很多例子,比如FTP的,shell命令的等等,我在这里介绍一下shell命令的发送和接收返回数据。
example里有个文件名叫exec.c 这个文件是实现shell命令的一个例子
- <span style="font-size:12px;">/*
- * Sample showing how to use libssh2 to execute a command remotely.
- *
- * The sample code has fixed values for host name, user name, password
- * and command to run.
- *
- * Run it like this:
- *
- * $ ./ssh2_exec 127.0.0.1 user password "uptime"
- *
- */
- #include "libssh2_config.h"
- #include <libssh2.h>
- #ifdef HAVE_WINSOCK2_H
- #include <winsock2.h>
- #endif
- #ifdef HAVE_SYS_SOCKET_H
- #include <sys/socket.h>
- #endif
- #ifdef HAVE_NETINET_IN_H
- #include <netinet/in.h>
- #endif
- #ifdef HAVE_SYS_SELECT_H
- #include <sys/select.h>
- #endif
- #ifdef HAVE_UNISTD_H
- #include <unistd.h>
- #endif
- #ifdef HAVE_ARPA_INET_H
- #include <arpa/inet.h>
- #endif
- #include <sys/time.h>
- #include <sys/types.h>
- #include <stdlib.h>
- #include <fcntl.h>
- #include <errno.h>
- #include <stdio.h>
- #include <ctype.h>
- static int waitsocket(int socket_fd, LIBSSH2_SESSION *session)
- {
- struct timeval timeout;
- int rc;
- fd_set fd;
- fd_set *writefd = NULL;
- fd_set *readfd = NULL;
- int dir;
- timeout.tv_sec = 10;
- timeout.tv_usec = 0;
- FD_ZERO(&fd);
- FD_SET(socket_fd, &fd);
- /* now make sure we wait in the correct direction */
- dir = libssh2_session_block_directions(session);
- if(dir & LIBSSH2_SESSION_BLOCK_INBOUND)
- readfd = &fd;
- if(dir & LIBSSH2_SESSION_BLOCK_OUTBOUND)
- writefd = &fd;
- rc = select(socket_fd + 1, readfd, writefd, NULL, &timeout);
- return rc;
- }
- int main(int argc, char *argv[])
- {
- const char *hostname = "127.0.0.1";
- const char *commandline = "uptime";
- const char *username = "user";
- const char *password = "password";
- unsigned long hostaddr;
- int sock;
- struct sockaddr_in sin;
- const char *fingerprint;
- LIBSSH2_SESSION *session;
- LIBSSH2_CHANNEL *channel;
- int rc;
- int exitcode;
- char *exitsignal=(char *)"none";
- int bytecount = 0;
- size_t len;
- LIBSSH2_KNOWNHOSTS *nh;
- int type;
- #ifdef WIN32
- WSADATA wsadata;
- WSAStartup(MAKEWORD(2,0), &wsadata);
- #endif
- if (argc > 1)
- /* must be ip address only */
- hostname = argv[1];
- if (argc > 2) {
- username = argv[2];
- }
- if (argc > 3) {
- password = argv[3];
- }
- if (argc > 4) {
- commandline = argv[4];
- }
- rc = libssh2_init (0);
- if (rc != 0) {
- fprintf (stderr, "libssh2 initialization failed (%d)\n", rc);
- return 1;
- }
- hostaddr = inet_addr(hostname);
- /* Ultra basic "connect to port 22 on localhost"
- * Your code is responsible for creating the socket establishing the
- * connection
- */
- sock = socket(AF_INET, SOCK_STREAM, 0);
- sin.sin_family = AF_INET;
- sin.sin_port = htons(22);
- sin.sin_addr.s_addr = hostaddr;
- if (connect(sock, (struct sockaddr*)(&sin),
- sizeof(struct sockaddr_in)) != 0) {
- fprintf(stderr, "failed to connect!\n");
- return -1;
- }
- /* Create a session instance */
- session = libssh2_session_init();
- if (!session)
- return -1;
- /* tell libssh2 we want it all done non-blocking */
- libssh2_session_set_blocking(session, 0);
- /* ... start it up. This will trade welcome banners, exchange keys,
- * and setup crypto, compression, and MAC layers
- */
- while ((rc = libssh2_session_handshake(session, sock)) ==
- LIBSSH2_ERROR_EAGAIN);
- if (rc) {
- fprintf(stderr, "Failure establishing SSH session: %d\n", rc);
- return -1;
- }
- nh = libssh2_knownhost_init(session);
- if(!nh) {
- /* eeek, do cleanup here */
- return 2;
- }
- /* read all hosts from here */
- libssh2_knownhost_readfile(nh, "known_hosts",
- LIBSSH2_KNOWNHOST_FILE_OPENSSH);
- /* store all known hosts to here */
- libssh2_knownhost_writefile(nh, "dumpfile",
- LIBSSH2_KNOWNHOST_FILE_OPENSSH);
- fingerprint = libssh2_session_hostkey(session, &len, &type);
- if(fingerprint) {
- struct libssh2_knownhost *host;
- #if LIBSSH2_VERSION_NUM >= 0x010206
- /* introduced in 1.2.6 */
- int check = libssh2_knownhost_checkp(nh, hostname, 22,
- fingerprint, len,
- LIBSSH2_KNOWNHOST_TYPE_PLAIN|
- LIBSSH2_KNOWNHOST_KEYENC_RAW,
- &host);
- #else
- /* 1.2.5 or older */
- int check = libssh2_knownhost_check(nh, hostname,
- fingerprint, len,
- LIBSSH2_KNOWNHOST_TYPE_PLAIN|
- LIBSSH2_KNOWNHOST_KEYENC_RAW,
- &host);
- #endif
- fprintf(stderr, "Host check: %d, key: %s\n", check,
- (check <= LIBSSH2_KNOWNHOST_CHECK_MISMATCH)?
- host->key:"<none>");
- /*****
- * At this point, we could verify that 'check' tells us the key is
- * fine or bail out.
- *****/
- }
- else {
- /* eeek, do cleanup here */
- return 3;
- }
- libssh2_knownhost_free(nh);
- if ( strlen(password) != 0 ) {
- /* We could authenticate via password */
- while ((rc = libssh2_userauth_password(session, username, password)) ==
- LIBSSH2_ERROR_EAGAIN);
- if (rc) {
- fprintf(stderr, "Authentication by password failed.\n");
- goto shutdown;
- }
- }
- else {
- /* Or by public key */
- while ((rc = libssh2_userauth_publickey_fromfile(session, username,
- "/home/user/"
- ".ssh/id_rsa.pub",
- "/home/user/"
- ".ssh/id_rsa",
- password)) ==
- LIBSSH2_ERROR_EAGAIN);
- if (rc) {
- fprintf(stderr, "\tAuthentication by public key failed\n");
- goto shutdown;
- }
- }
- #if 0
- libssh2_trace(session, ~0 );
- #endif
- /* Exec non-blocking on the remove host */
- while( (channel = libssh2_channel_open_session(session)) == NULL &&
- libssh2_session_last_error(session,NULL,NULL,0) ==
- LIBSSH2_ERROR_EAGAIN )
- {
- waitsocket(sock, session);
- }
- if( channel == NULL )
- {
- fprintf(stderr,"Error\n");
- exit( 1 );
- }
- while( (rc = libssh2_channel_exec(channel, commandline)) ==
- LIBSSH2_ERROR_EAGAIN )
- {
- waitsocket(sock, session);
- }
- if( rc != 0 )
- {
- fprintf(stderr,"Error\n");
- exit( 1 );
- }
- for( ;; )
- {
- /* loop until we block */
- int rc;
- do
- {
- char buffer[0x4000];
- rc = libssh2_channel_read( channel, buffer, sizeof(buffer) );
- if( rc > 0 )
- {
- int i;
- bytecount += rc;
- fprintf(stderr, "We read:\n");
- for( i=0; i < rc; ++i )
- fputc( buffer[i], stderr);
- fprintf(stderr, "\n");
- }
- else {
- if( rc != LIBSSH2_ERROR_EAGAIN )
- /* no need to output this for the EAGAIN case */
- fprintf(stderr, "libssh2_channel_read returned %d\n", rc);
- }
- }
- while( rc > 0 );
- /* this is due to blocking that would occur otherwise so we loop on
- this condition */
- if( rc == LIBSSH2_ERROR_EAGAIN )
- {
- waitsocket(sock, session);
- }
- else
- break;
- }
- exitcode = 127;
- while( (rc = libssh2_channel_close(channel)) == LIBSSH2_ERROR_EAGAIN )
- waitsocket(sock, session);
- if( rc == 0 )
- {
- exitcode = libssh2_channel_get_exit_status( channel );
- libssh2_channel_get_exit_signal(channel, &exitsignal,
- NULL, NULL, NULL, NULL, NULL);
- }
- if (exitsignal)
- fprintf(stderr, "\nGot signal: %s\n", exitsignal);
- else
- fprintf(stderr, "\nEXIT: %d bytecount: %d\n", exitcode, bytecount);
- libssh2_channel_free(channel);
- channel = NULL;
- shutdown:
- libssh2_session_disconnect(session,
- "Normal Shutdown, Thank you for playing");
- libssh2_session_free(session);
- #ifdef WIN32
- closesocket(sock);
- #else
- close(sock);
- #endif
- fprintf(stderr, "all done\n");
- libssh2_exit();
- return 0;
- }</span>
1.WSAStartup(),打开socket链接库
2.socket(),初始化一个socket套接字
3.connect(),连接到ssh服务器
4.libssh2_session_init(),初始化一个ssh连接
5.libssh2_session_handshake(),将socket和session握手通信
6.libssh2_userauth_password(),验证登陆
7.libssh2_channel_open_session(),打开通道
8.libssh2_channel_exec(),发送shell命令
9.libssh2_channel_read(),读取命令处理结果
这里的8.libssh2_channel_exec(),发送shell命令和心目中想象的不太一样,不能循环发送命令,发送第一次命令时,该命令执行,但是第二次再发送时会返回一个
名字叫LIBSSH2_ERROR_CHANNEL_REQUEST_DENIED的ERROR,也就是说这个函数只能发送一次shell命令就不能再用了,太麻烦了。
在这里这种需求怎么解决:
当调用完libssh2_channel_exec()时,将通道释放掉libssh2_channel_close(),然后再重新打开libssh2_channel_open(),再使用这个libssh2_channel_exec()发送shell命令。
但是在这里可能会出现一个问题,在libssh2_channel_open()的时候并没有把通道打开,调用libssh2_session_last_error()发现这个错误代码是LIBSSH2_ERROR_EAGAIN,在官方网站的解释是这不是一个错误,是一个阻塞的过程,也就是现在这个链接已经阻塞了,需要等等再打开。这也就是最上面那个waitsocket()的作用了。
总结:如果不能理解,简洁直白的方式就是类似于在SSH终端敲打命令的方式
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