问题描述
我使用服务器作为跳转主机（主机 A）以通过 ssh 连接到内部网络（主机 B）上的机器。
我使用这个 ssh 命令，它工作正常。
ssh -J user@hostA_IP.com root@hostB_IP.com
同样，我可以通过以下方式将文件 scp 到主机 B：
scp -o 'ProxyCommand ssh user@hostA_IP.com -W %h:%p' file.txt root@hostB_IP.com:~/
我正在尝试使用 libssh 编写一个 c 程序来执行相同的操作。我可以在 libssh 文档中找到的最接近的示例是端口转发。我的理解可能与跳转主机相同。我正在使用 libssh 中的 sftp 函数来传输文件。
我有下面的 c 程序，它成功连接到主机 A。而且我相信它成功打开了到主机 B 的 sftp 连接 [下面的日志]。但是当它尝试打开主机 B 上的文件时，它会出现“权限被拒绝”的错误。
我有以下问题。
-
端口转发到主机 B 是否正确完成？ [查看下面的日志 - 它有一个错误]
-
这是将端口转发到主机 B 的正确函数调用吗？参数 2 是 user@IP 地址吗？
rc = ssh_channel_open_forward(channel,"root@hostB_IP.com",22,"localhost",5555);
-
我认为端口转发是正确完成的，因为从日志看来端口转发成功后打开了 sftp 会话。
-
假设端口转发和 sftp 会话创建正常，并且由于错误是“SFTP 服务器：权限被拒绝”，我是否应该在 sftp 会话中以不同的方式打开文件。
这是代码，完整的日志在代码下方：
谢谢
代码：
#include <libssh/sftp.h>
int main(int argc,char* argv[]) {
// Create SSH session
ssh_session session;
ssh_channel channel;
int rc,port = 22;
char buffer[1024];
unsigned int nbytes;
int verbosity = SSH_LOG_PROTOCOL;
printf("Session...\n");
session = ssh_new();
if (session == NULL)
exit(-1);
ssh_options_set(session,SSH_OPTIONS_HOST,hostA_IP.com);
ssh_options_set(session,SSH_OPTIONS_LOG_VERBOSITY,&verbosity);
ssh_options_set(session,SSH_OPTIONS_PORT,&port);
ssh_options_set(session,SSH_OPTIONS_USER,"user");
printf("Connecting...\n");
rc = ssh_connect(session);
if (rc != SSH_OK)
error(session);
printf("Password Autentication...\n");
rc = ssh_userauth_password(session,"user","userpassword");
if (rc != SSH_AUTH_SUCCESS)
error(session);
printf("Channel...\n");
channel = ssh_channel_new(session);
if (channel == NULL)
exit(-1);
printf("Port forwarding to Host B...\n");
rc = ssh_channel_open_forward(channel,5555);
if (rc != SSH_OK) {
error(session);
exit(1);
}
printf("Port forwarding done...\n");
// Open SFTP session
sftp_session sftp0;
printf("Opening sftp session...\n");
sftp0 = sftp_new(session);
if (sftp0 == NULL) {
fprintf(stderr,"Error allocating SFTP session: %s\n",ssh_get_error(session));
return SSH_ERROR;
}
// Initialize the SFTP session
rc = sftp_init(sftp0);
if (rc != SSH_OK) {
fprintf(stderr,"Error initializing SFTP session: %s.\n",sftp_get_error(sftp0));
sftp_free(sftp0);
return rc;
}
printf("SFTP session opened...\n");
sftp_file file0;
printf("Openign file on Host B...\n");
file0 = sftp_open(sftp0,"/home/root/test.blob",O_WRONLY | O_CREAT | O_TRUNC,S_IRWXU);
if (file0 == NULL) {
fprintf(stderr,"Can't open test.blob for writing: %s\n",ssh_get_error(session));
return SSH_ERROR;
exit(1);
}
}
完整日志：
Session...
Connecting...
[2021/02/13 10:59:22.044331,2] ssh_connect: libssh 0.7.0 (c) 2003-2014 Aris Adamantiadis,Andreas Schneider,and libssh contributors. Distributed under the LGPL,please refer to COPYING file for information about your rights,using threading threads_noop
[2021/02/13 10:59:22.063292,2] ssh_socket_connect: Nonblocking connection socket: 3
[2021/02/13 10:59:22.063313,2] ssh_connect: Socket connecting,now waiting for the callbacks to work
[2021/02/13 10:59:22.077165,1] socket_callback_connected: Socket connection callback: 1 (0)
[2021/02/13 10:59:22.099055,1] ssh_client_connection_callback: SSH server banner: SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
[2021/02/13 10:59:22.099081,1] ssh_analyze_banner: Analyzing banner: SSH-2.0-OpenSSH_7.6p1 Ubuntu-4ubuntu0.3
[2021/02/13 10:59:22.099095,1] ssh_analyze_banner: We are talking to an OpenSSH client version: 7.6 (70600)
[2021/02/13 10:59:22.197188,2] ssh_packet_dh_reply: Received SSH_KEXDH_REPLY
[2021/02/13 10:59:22.201442,2] ssh_client_curve25519_reply: SSH_MSG_NEWKEYS sent
[2021/02/13 10:59:22.201466,2] ssh_packet_newkeys: Received SSH_MSG_NEWKEYS
[2021/02/13 10:59:22.210742,2] ssh_packet_newkeys: Signature verified and valid
Password Autentication...
Channel...
Port forwarding to Host B...
[2021/02/13 10:59:22.315060,2] channel_open: Creating a channel 43 with 64000 window and 32768 max packet
[2021/02/13 10:59:22.465235,2] ssh_packet_global_request: Received SSH_MSG_GLOBAL_REQUEST packet
[2021/02/13 10:59:22.465290,2] ssh_packet_global_request: UNKNOWN SSH_MSG_GLOBAL_REQUEST [email protected] 0
[2021/02/13 10:59:22.465305,1] ssh_packet_process: Couldn't do anything with packet type 80
[2021/02/13 10:59:22.709942,1] ssh_packet_channel_open_fail: Channel opening failure: channel 43 error (2) Name or service not known
rc is 0
Port forwarding done...
Opening sftp session...
[2021/02/13 10:59:22.710034,2] channel_open: Creating a channel 44 with 64000 window and 32768 max packet
[2021/02/13 10:59:22.725936,2] ssh_packet_channel_open_conf: Received a CHANNEL_OPEN_CONFIRMATION for channel 44:0
[2021/02/13 10:59:22.725981,2] ssh_packet_channel_open_conf: Remote window : 0,maxpacket : 32768
[2021/02/13 10:59:22.742666,2] channel_rcv_change_window: Adding 2097152 bytes to channel (44:0) (from 0 bytes)
[2021/02/13 10:59:22.742715,2] channel_request: Channel request subsystem success
[2021/02/13 10:59:22.760308,2] grow_window: growing window (channel 44:0) to 1280000 bytes
[2021/02/13 10:59:22.760368,1] sftp_init: SFTP server version 3
[2021/02/13 10:59:22.760390,1] sftp_init: SFTP server extension: [email protected],version: 1
[2021/02/13 10:59:22.760405,1] sftp_init: SFTP server extension: [email protected],version: 2
[2021/02/13 10:59:22.760419,1] sftp_init: SFTP server extension: [email protected],version: 2
[2021/02/13 10:59:22.760433,1] sftp_init: SFTP server extension: [email protected],version: 1
[2021/02/13 10:59:22.760447,1] sftp_init: SFTP server extension: [email protected],version: 1
SFTP session opened...
Openign file on Host B...
[2021/02/13 10:59:22.842023,1] sftp_open: SFTP server: Permission denied
Can't open test.blob for writing: SFTP server: Permission denied
解决方法
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