Linux ssh can log in sftp can't login solution

My server has been normal use, peacetime use of SECURECRT for management, using Securefx file upload download, and suddenly one day Securefx connection when the problem, Securefx log as follows:

I Securefx version 6.6.1.289 (official Release-november 4, 2010)
I session 00002 successfully established (for) sessions mydomain_218.245.0.54_cd.mydomain.com
I ssh2core version 6.6.0.289
I am connecting to cd.mydomain.com:22 ...
I am changing from state state_not_connected to State_expect_kex_init
I Using protocol SSH2
I recv:remote Identifier = ' ssh-2.0-openssh_5.3 '
I cap:remote can Re-key
I cap:remote sends language in Password change requests
I cap:remote sends algorithm name in PK_OK packets
I cap:remote sends algorithm name in public key packets
I cap:remote sends algorithm name in signatures
I cap:remote sends error text in open failure packets
I cap:remote sends name in service accept packets
I cap:remote includes port number in X11 open packets
I cap:remote uses 160 bit keys for SHA1 MAC
I cap:remote supports new Diffie-hellman group exchange messages
I cap:remote correctly handles unknown SFTP extensions
I cap:remote correctly encodes OID for GSSAPI
I cap:remote correctly uses connected addresses in FORWARDED-TCPIP requests
I the following key exchange method has been filtered to the key Exchange method list because it are not supported:gss-g ex-sha1-towm5slw5ew8mqkay+al2g==
I Send:kexinit
I recv:read Kexinit
I Available Remote kex Methods = DIFFIE-HELLMAN-GROUP-EXCHANGE-SHA256,DIFFIE-HELLMAN-GROUP-EXCHANGE-SHA1, Diffie-hellman-group14-sha1,diffie-hellman-group1-sha1

I Channel Closed.

Very puzzled, Google for a half-day also did not solve the problem.

First of all, to ensure that other bizarre problems arise, I will iptables and SELinux are closed, or not.
Check to see if the subsystem sftp/usr/libexec/openssh/sftp-server in the/etc/ssh/sshd_config file has been commented, is not commented, and the file system also has
[ROOT@CD ~]# Ll/usr/libexec/openssh/sftp-server
----------. 1 root 63544 February 2013/usr/libexec/openssh/sftp-server
The explanation should be right.

Then open the SSH dubug mode, edit the/etc/ssh/sshd_config file, the loglevel info to loglevel DEBUG, restart the sshd service
#/etc/init.d/sshd Restart

Use Securefx to view log information when you log on.

There is no log output when viewing # Tail-f/var/log/messages.
View # tail-f/var/log/secure log output as follows, no obvious error message output:

Aug 18:21:59 CD sshd[1307]: Debug1:forked child 1870.
Aug 18:21:59 CD sshd[1870]: Set/proc/self/oom_score_adj to 0
Aug 18:21:59 CD sshd[1870]: Debug1:rexec start in 5 out 5 Newsock 5 Pipe 7 sock 8
Aug 18:21:59 CD sshd[1870]: debug1:inetd sockets after Dupping:3, 3
Aug 18:21:59 CD sshd[1870]: Connection from 171.214.177.214 Port 52174
Aug 18:21:59 CD sshd[1870]: Debug1:client protocol version 2.0; Client software version securefx_6_6_1_289 Securefx
Aug 18:21:59 CD sshd[1870]: Debug1:no match:securefx_6_6_1_289 Securefx
Aug 18:21:59 CD sshd[1870]: debug1:enabling compatibility mode for Protocol 2.0
Aug 18:21:59 CD sshd[1870]: Debug1:local version string ssh-2.0-openssh_5.3
Aug 18:21:59 CD sshd[1871]: debug1:permanently_set_uid:74/74
Aug 18:21:59 CD sshd[1871]: DEBUG1:LIST_HOSTKEY_TYPES:SSH-RSA,SSH-DSS
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_kexinit sent
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_kexinit received
Aug 18:21:59 CD sshd[1871]: Debug1:kex:client->server aes256-ctr hmac-sha1 None
Aug 18:21:59 CD sshd[1871]: debug1:kex:server->client aes256-ctr hmac-sha1 None
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_kex_dh_gex_request received
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_kex_dh_gex_group sent
Aug 18:21:59 CD sshd[1871]: debug1:expecting ssh2_msg_kex_dh_gex_init
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_kex_dh_gex_reply sent
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_newkeys sent
Aug 18:21:59 CD sshd[1871]: debug1:expecting Ssh2_msg_newkeys
Aug 18:21:59 CD sshd[1871]: Debug1:ssh2_msg_newkeys received
Aug 18:21:59 CD sshd[1871]: Debug1:kex Done
Aug 18:21:59 CD sshd[1871]: debug1:userauth-request for user root service Ssh-connection method None
Aug 18:21:59 CD sshd[1871]: Debug1:attempt 0 Failures 0
Aug 18:21:59 CD sshd[1870]: debug1:PAM:initializing for "root"
Aug 18:21:59 CD sshd[1870]: debug1:PAM:setting pam_rhost to "171.214.177.214"
Aug 18:21:59 CD sshd[1870]: debug1:PAM:setting pam_tty to "ssh"
Aug 18:21:59 CD sshd[1871]: debug1:userauth-request for user root service ssh-connection

No solution, continue Google solution Https://www.linuxquestions.org/questions/linux-server-73/can ' t-get-sftp-logging-to-work-931609/ Receive inspiration, will/etc/ssh/sshd_config in the

subsystem Sftp/usr/libexec/openssh/sftp-server
To
subsystem SFTP INTERNAL-SFTP

After restarting the sshd, SFTP is working properly.

But the reason still somehow, looking back, found that/usr/libexec/openssh/sftp-server did not have any permissions:
# Ll/usr/libexec/openssh/sftp-server
----------. 1 root 63544 February 2013/usr/libexec/openssh/sftp-server

The normal situation should be this:
# Ll/usr/libexec/openssh/sftp-server
-rwxr-xr-x. 1 root root 63544 Nov 2013/usr/libexec/openssh/sftp-server

Consulting Master said Stop OpenSSH service RM sftp-server file Normal SCP in the past restart OpenSSH
But I am remote operation, production system, dare not stop openssh service, if not even on the melon, the master suggested that the first such use.

Note:/usr/libexec/openssh/sftp-server does not have any permissions, root users can not delete changes.