linux libssh2 实例

谁践踏了优雅 2021-08-26 15:32 390阅读 0赞

以下是包含必备头文件

#include "libssh2_config.h"
    #include<libssh2.h>
    #include<libssh2_sftp.h>

以下为定义的静态子串常量

const char *keyfile1 = "~/.ssh/id_rsa.pub";
    const char *keyfile2 = "~/.ssh/id_rsa";
    const char *username = "username";
    const char *password = "password";
    
    unsigned long hostaddr;
    int rc, sock, i, auth_pw = 0;
    struct sockaddr_in_sin;
    const char *fingerprint;
    char * userauthlist;
    LIBSSH2_SESSION *session;
    LIBSSH2_CHANNEL *channel;

连接到SSH2步骤：

（1）建立socket并连接到远程主机SSH2服务（22端口）；

（2）创建一个LIBSSH2\_SESSION 实例并启动它。启动动作包括设置欢迎横幅、交换密钥并且设置加密、压缩和MAC层。

session = libssh2_session_init();   //创建一个会话实例
    if(libssh2_session_handshake(session, sock))
    {
      fprintf(stderr, "Failure establishing SSH session");
      return -1;
    }

（3）认证：检查主机密钥指纹并检查可用的认证方式。

fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
    userauthlist = libssh2_userauth_list(session, username, strlen(username));
    if(strstr(userauthlist, "password") != NULL)
    {
      auth_pw |= 1;
    }
    if(strstr(userauthlist, "keyboad-interactive") != NULL)
    {
      auth_pw |= 2;
    }
    if(strstr(userauthlist, "publickey") != NULL)
    {
      auth_pw |= 4;
    }

（4）如果在参数列表中设置了认证方式，则将认证方式设为命令中的方式（前提是该方式是通过上个步骤检测可用的）。

if(argc > 4)
    {
      if((auth_pw & 1) && !strcasecmp(argv[4], "-p"))
      {
        auth_pw = 1;
      }
      if((auth_pw & 2) && !strcasecmp(argv[4], "-i"))
      {
        auth_pw = 2;
      }
      if((auth_pw && 4) && !strcasecmp(argv[4], "-k"))
      {
        auth_pw = 4;
      }
    }

（5）根据上一步选定的认证方式开始认证。

if (auth_pw & 1) {
            /* We could authenticate via password */ 
            if (libssh2_userauth_password(session, username, password)) {
    
                fprintf(stderr, "\tAuthentication by password failed!\n");
                goto shutdown;
            } else {
                fprintf(stderr, "\tAuthentication by password succeeded.\n");
            }
        } else if (auth_pw & 2) {
            /* Or via keyboard-interactive */ 
            if (libssh2_userauth_keyboard_interactive(session, username,
    
                                                      &kbd_callback) ) {
                fprintf(stderr,
                    "\tAuthentication by keyboard-interactive failed!\n");
                goto shutdown;
            } else {
                fprintf(stderr,
                    "\tAuthentication by keyboard-interactive succeeded.\n");
            }
        } else if (auth_pw & 4) {
            /* Or by public key */ 
            if (libssh2_userauth_publickey_fromfile(session, username, keyfile1,
    
                                                    keyfile2, password)) {
                fprintf(stderr, "\tAuthentication by public key failed!\n");
                goto shutdown;
            } else {
                fprintf(stderr, "\tAuthentication by public key succeeded.\n");
            }
        } else {
            fprintf(stderr, "No supported authentication methods found!\n");
            goto shutdown;
        }

（6）请求一个shell

if(!(channel = libssh2_channel_open_session(session)))

（7）设置一些环境变量，并上传给服务器

libssh2_channel_setenv(channel, "F00", "bar");

（8）请求一个vanilla的终端模拟。

libssh2_channel_request_pty(channel, "vanilla")

（9）在上一步请求的pty上开启SHELL。

libssh2_channel_shell(channel)

（10）至此，可以交互使用shell了

libssh2_channel_read();
    libssh2_channel_read_stderr();
    libssh2_channel_write();
    
    libssh2_channel_write_stderr();
    
    
    /* 打开或关闭阻塞模式 */
    
    libssh2_channel_set_blocking();
    
    /* 如果服务器发送EOF */
    
    libssh2_channel_eof()返回非0；
    
    /* 关闭channel */
    
    libssh2_channel_close();
    
    /* 释放一个channel */
    
    libssh2_channel_free();

（11）ssh交互完成后，关闭会话并释放会话

libssh2_session_disconnect(session, "Normal Shutdown");
    libssh2_session_free(session);

（12）关闭sock并退出libssh2

close(sock);
    libssh2_exit();

官网实例以作参考：

[https://github.com/libssh2/libssh2/blob/master/example/ssh2.c][https_github.com_libssh2_libssh2_blob_master_example_ssh2.c]

/*
     * Sample showing how to do SSH2 connect.
     *
     * The sample code has default values for host name, user name, password
     * and path to copy, but you can specify them on the command line like:
     *
     * "ssh2 host user password [-p|-i|-k]"
     */
    
    #include "libssh2_config.h"
    #include <libssh2.h>
    #include <libssh2_sftp.h>
    
    #ifdef HAVE_WINDOWS_H
    # include <windows.h>
    #endif
    #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_UNISTD_H
    #include <unistd.h>
    #endif
    # ifdef HAVE_ARPA_INET_H
    #include <arpa/inet.h>
    #endif
    
    #include <sys/types.h>
    #include <fcntl.h>
    #include <errno.h>
    #include <stdio.h>
    #include <ctype.h>
    
    
    const char *keyfile1 = "~/.ssh/id_rsa.pub";
    const char *keyfile2 = "~/.ssh/id_rsa";
    const char *username = "username";
    const char *password = "password";
    
    
    static void kbd_callback(const char *name, int name_len,
                             const char *instruction, int instruction_len,
                             int num_prompts,
                             const LIBSSH2_USERAUTH_KBDINT_PROMPT *prompts,
                             LIBSSH2_USERAUTH_KBDINT_RESPONSE *responses,
                             void **abstract)
    {
        (void)name;
        (void)name_len;
        (void)instruction;
        (void)instruction_len;
        if(num_prompts == 1) {
            responses[0].text = strdup(password);
            responses[0].length = strlen(password);
        }
        (void)prompts;
        (void)abstract;
    } /* kbd_callback */
    
    
    int main(int argc, char *argv[])
    {
        unsigned long hostaddr;
        int rc, sock, i, auth_pw = 0;
        struct sockaddr_in sin;
        const char *fingerprint;
        char *userauthlist;
        LIBSSH2_SESSION *session;
        LIBSSH2_CHANNEL *channel;
    
    #ifdef WIN32
        WSADATA wsadata;
        int err;
    
        err = WSAStartup(MAKEWORD(2, 0), &wsadata);
        if(err != 0) {
            fprintf(stderr, "WSAStartup failed with error: %d\n", err);
            return 1;
        }
    #endif
    
        if(argc > 1) {
            hostaddr = inet_addr(argv[1]);
        }
        else {
            hostaddr = htonl(0x7F000001);
        }
    
        if(argc > 2) {
            username = argv[2];
        }
        if(argc > 3) {
            password = argv[3];
        }
    
        rc = libssh2_init(0);
        if(rc != 0) {
            fprintf(stderr, "libssh2 initialization failed (%d)\n", rc);
            return 1;
        }
    
        /* 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 and start it up. This will trade welcome
         * banners, exchange keys, and setup crypto, compression, and MAC layers
         */
        session = libssh2_session_init();
        if(libssh2_session_handshake(session, sock)) {
            fprintf(stderr, "Failure establishing SSH session\n");
            return -1;
        }
    
        /* At this point we havn't authenticated. The first thing to do is check
         * the hostkey's fingerprint against our known hosts Your app may have it
         * hard coded, may go to a file, may present it to the user, that's your
         * call
         */
        fingerprint = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
        fprintf(stderr, "Fingerprint: ");
        for(i = 0; i < 20; i++) {
            fprintf(stderr, "%02X ", (unsigned char)fingerprint[i]);
        }
        fprintf(stderr, "\n");
    
        /* check what authentication methods are available */
        userauthlist = libssh2_userauth_list(session, username, strlen(username));
        fprintf(stderr, "Authentication methods: %s\n", userauthlist);
        if(strstr(userauthlist, "password") != NULL) {
            auth_pw |= 1;
        }
        if(strstr(userauthlist, "keyboard-interactive") != NULL) {
            auth_pw |= 2;
        }
        if(strstr(userauthlist, "publickey") != NULL) {
            auth_pw |= 4;
        }
    
        /* if we got an 4. argument we set this option if supported */
        if(argc > 4) {
            if((auth_pw & 1) && !strcasecmp(argv[4], "-p")) {
                auth_pw = 1;
            }
            if((auth_pw & 2) && !strcasecmp(argv[4], "-i")) {
                auth_pw = 2;
            }
            if((auth_pw & 4) && !strcasecmp(argv[4], "-k")) {
                auth_pw = 4;
            }
        }
    
        if(auth_pw & 1) {
            /* We could authenticate via password */
            if(libssh2_userauth_password(session, username, password)) {
                fprintf(stderr, "\tAuthentication by password failed!\n");
                goto shutdown;
            }
            else {
                fprintf(stderr, "\tAuthentication by password succeeded.\n");
            }
        }
        else if(auth_pw & 2) {
            /* Or via keyboard-interactive */
            if(libssh2_userauth_keyboard_interactive(session, username,
                                                     &kbd_callback) ) {
                fprintf(stderr,
                        "\tAuthentication by keyboard-interactive failed!\n");
                goto shutdown;
            }
            else {
                fprintf(stderr,
                        "\tAuthentication by keyboard-interactive succeeded.\n");
            }
        }
        else if(auth_pw & 4) {
            /* Or by public key */
            if(libssh2_userauth_publickey_fromfile(session, username, keyfile1,
                                                   keyfile2, password)) {
                fprintf(stderr, "\tAuthentication by public key failed!\n");
                goto shutdown;
            }
            else {
                fprintf(stderr, "\tAuthentication by public key succeeded.\n");
            }
        }
        else {
            fprintf(stderr, "No supported authentication methods found!\n");
            goto shutdown;
        }
    
        /* Request a shell */
        channel = libssh2_channel_open_session(session);
        if(!channel) {
            fprintf(stderr, "Unable to open a session\n");
            goto shutdown;
        }
    
        /* Some environment variables may be set,
         * It's up to the server which ones it'll allow though
         */
        libssh2_channel_setenv(channel, "FOO", "bar");
    
        /* Request a terminal with 'vanilla' terminal emulation
         * See /etc/termcap for more options
         */
        if(libssh2_channel_request_pty(channel, "vanilla")) {
            fprintf(stderr, "Failed requesting pty\n");
            goto skip_shell;
        }
    
        /* Open a SHELL on that pty */
        if(libssh2_channel_shell(channel)) {
            fprintf(stderr, "Unable to request shell on allocated pty\n");
            goto shutdown;
        }
    
        /* At this point the shell can be interacted with using
         * libssh2_channel_read()
         * libssh2_channel_read_stderr()
         * libssh2_channel_write()
         * libssh2_channel_write_stderr()
         *
         * Blocking mode may be (en|dis)abled with: libssh2_channel_set_blocking()
         * If the server send EOF, libssh2_channel_eof() will return non-0
         * To send EOF to the server use: libssh2_channel_send_eof()
         * A channel can be closed with: libssh2_channel_close()
         * A channel can be freed with: libssh2_channel_free()
         */
    
      skip_shell:
        if(channel) {
            libssh2_channel_free(channel);
            channel = NULL;
        }
    
        /* Other channel types are supported via:
         * libssh2_scp_send()
         * libssh2_scp_recv2()
         * libssh2_channel_direct_tcpip()
         */
    
      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;
    }

[https_github.com_libssh2_libssh2_blob_master_example_ssh2.c]: https://github.com/libssh2/libssh2/blob/master/example/ssh2.c