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I've tried service sshd restart, I've added sshd:all:allow to my /etc/allow.hosts and the remote user tried rm ~/.ssh/known_hosts. I also checked the logs: cat /var/logs/secure | grep ssh and it says Accepted password for $user from ...

This is the first time this particular user has tried connecting but other users have successfully connected to my machine for several days.

None of this has worked or pointed me to the error. Any ideas?

Edit: I SSH-d into his machine to see if I could get an error log or something by SSH-ing back to me. If I use ssh -vvv $host I get various messages, one of which is Unspecified GSS failure. Minor code may provide more information. Here's the complete error log (hostnames and IPs left out):

OpenSSH_5.3p1 Debian-3ubuntu7, OpenSSL 0.9.8k 25 Mar 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to some_host [XX.XX.XX.XX] port 22.
debug1: Connection established.
debug1: identity file /home/ssr/.ssh/identity type -1
debug3: Not a RSA1 key file /home/ssr/.ssh/id_rsa.
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug3: key_read: missing keytype
debug2: key_type_from_name: unknown key type 'Proc-Type:'
debug3: key_read: missing keytype
debug2: key_type_from_name: unknown key type 'DEK-Info:'
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug2: key_type_from_name: unknown key type '-----END'
debug3: key_read: missing keytype
debug1: identity file /home/ssr/.ssh/id_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/ssr/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.9
debug1: match: OpenSSH_5.9 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3p1 Debian-3ubuntu7
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug3: Wrote 792 bytes for a total of 831
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-sha2-256,hmac-sha2-256-96,hmac-sha2-512,hmac-sha2-512-96,hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug3: Wrote 24 bytes for a total of 855
debug2: dh_gen_key: priv key bits set: 132/256
debug2: bits set: 509/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: Wrote 144 bytes for a total of 999
debug3: check_host_in_hostfile: filename /home/ssr/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 8
debug3: check_host_in_hostfile: filename /home/ssr/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 9
debug1: Host 'xxx' is known and matches the RSA host key.
debug1: Found key in /home/ssr/.ssh/known_hosts:8
debug2: bits set: 502/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: Wrote 16 bytes for a total of 1015
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug3: Wrote 48 bytes for a total of 1063
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /home/ssr/.ssh/identity ((nil))
debug2: key: /home/ssr/.ssh/id_rsa (0x20d2d350)
debug2: key: /home/ssr/.ssh/id_dsa ((nil))
debug3: Wrote 64 bytes for a total of 1127
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic,password
debug3: preferred gssapi-keyex,gssapi-with-mic,gssapi,publickey,keyboard-interactive,password
debug3: authmethod_lookup gssapi-keyex
debug3: remaining preferred: gssapi-with-mic,gssapi,publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-keyex
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug2: we did not send a packet, disable method
debug3: authmethod_lookup gssapi-with-mic
debug3: remaining preferred: gssapi,publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-with-mic
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_1000' not found

debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_1000' not found

debug1: Unspecified GSS failure.  Minor code may provide more information


debug2: we did not send a packet, disable method
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /home/ssr/.ssh/identity
debug3: no such identity: /home/ssr/.ssh/identity
debug1: Offering public key: /home/ssr/.ssh/id_rsa
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
debug3: Wrote 368 bytes for a total of 1495
Connection closed by $my.ip (no, don't want to share)

Another edit: other users seem to be able to connect. My version is: OpenSSH_5.9p1, OpenSSL 1.0.0j-fips 10 May 2012. His is older, as can bee seen from the error log.

New log

Improve this question
10
  • Could something in the user's .profile or .bashrc be causing premature exit?
    – killermist
    Commented Jul 8, 2012 at 16:21
  • Run ssh with -vvv switch (ssh -vvv user@host) and post output...
    – pbm
    Commented Jul 8, 2012 at 16:22
  • ~.ssh/known_hosts should only have affect on connections made FROM the machine on which they're on.
    – killermist
    Commented Jul 8, 2012 at 16:23
  • The .profile/.bashrc files are just skeleton files.
    – Haukur
    Commented Jul 8, 2012 at 16:33
  • 1
    @UlrichSchwarz That would result in a message in the server logs. Haukur: Your client did try to authenticate with a private key, and closed the connection midway, without getting around to prompting for a password. What happens if you disable this private key (move it out of the way)?
    – Gilles 'SO- stop being evil'
    Commented Jul 8, 2012 at 23:34

2 Answers 2

Reset to default
3

ssh sometimes gives misleading error-messages.

I found the best way to debug ssh-problems is from the server-side.

  1. ssh into the target server with a working connection.
  2. Stop sshd (your session will be kept running).
  3. Then start sshd in console/debug-mode $(which sshd) -d.
  4. Now retry and look closely at why sshd refuses the connection.
  5. Do not forget to start sshd again for normal operations.

If you do not see enough information with a single d increase the number - -ddd is the maximum verbosity - a single one on the server side will tell you more than the most verbose level on the client side...

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8
  • This is the output.
    – Haukur
    Commented Jul 8, 2012 at 23:47
  • @Haukur this looks as if a session is established using password authentication. After the tty is assigned the user is being logged out. It is not clear wether this is caused by pam or by a process after login.
    – Nils
    Commented Jul 9, 2012 at 21:31
  • I wrote a Python script to monitor who is logged some days ago and and strangely I could see the user that can't log in as "logged in". I did killal -u $user and tried logging back in but nothing changed. The command that showed the user as logged in was netstat -nutp | grep sshd.
    – Haukur
    Commented Jul 9, 2012 at 23:31
  • @Nils I'm at a loss. This search duckduckgo.com/?q=gssapi-with-mic+ssh shows lots of similar problems. Some have solutions, others are unanswered, but none of them seem to be consistent as to what the problem actually is.
    – killermist
    Commented Jul 9, 2012 at 23:47
  • @Haukur - this looks even more like a pam-problem. If you suspect gssapi - turn it off - or do you have cases where gssapi is needed?
    – Nils
    Commented Jul 11, 2012 at 21:12
1

I met this problem too, and after several hours of logs, tcpdump debug, found out simply UPDATE the openssh to the latest version will solve the problem.

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