求：用libssh2，登录免密码服务器的代码

[songxuanting]

刚接触ssh2, 用secureCRT工具登录server时,只需要输入用户名，不用密码。

现在，调试网上window7 下的ssh2客户端小程序，试试libssh2动态库(已经有了)的使用。
但遇到了问题，就是无法登录免密码的server。如果换需要用户名和密码的ssh2 server,则可以登录。

请大家看看下面的代码有什么问题，或者给个简单的学习样例，多谢多谢。

#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>

#pragma comment(lib,"libssh2.lib")
#pragma comment(lib,"WS2_32.lib")
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 = "192.168.1.1";
const char *commandline = "ls";
const char *username = "admin";
const char *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;
}