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Daniel Khan

2005-Mar-15 10:23 UTC

Segmentation fault on public key authentification

Hello list,

after some weeks of operation and updates one server of mine needed a 
reboot.
Now authentification with public key causes a segfault.

System information:

2.6.8-gentoo-r4 x86_64 AMD Dual Opteron(tm) Processor 242 AuthenticAMD

Debugging information:

// ssh fom node2 to node1

# ssh -vvv node1
OpenSSH_3.9p1, OpenSSL 0.9.7d 17 Mar 2004
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: ssh_connect: needpriv 0
debug1: Connecting to node1 [192.168.0.100] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug3: Not a RSA1 key file /root/.ssh/identity.
debug2: key_type_from_name: unknown key type '-----BEGIN'
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
debug2: key_type_from_name: unknown key type '-----END'
debug3: key_read: missing keytype
debug1: identity file /root/.ssh/identity type 2
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_3.9p1
debug1: match: OpenSSH_3.9p1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_3.9p1
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: 
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-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc
at lysator.liu.se,aes128-ctr,aes192-ctr,aes25
debug2: kex_parse_kexinit: 
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc
at lysator.liu.se,aes128-ctr,aes192-ctr,aes25
debug2: kex_parse_kexinit: 
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160 at
openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: 
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160 at
openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: none,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-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: 
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc
at lysator.liu.se,aes128-ctr,aes192-ctr,aes25
debug2: kex_parse_kexinit: 
aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour,aes192-cbc,aes256-cbc,rijndael-cbc
at lysator.liu.se,aes128-ctr,aes192-ctr,aes25
debug2: kex_parse_kexinit: 
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160 at
openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: 
hmac-md5,hmac-sha1,hmac-ripemd160,hmac-ripemd160 at
openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit: none,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_init: found hmac-md5
debug1: kex: server->client aes128-cbc hmac-md5 none
debug2: mac_init: found hmac-md5
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug2: dh_gen_key: priv key bits set: 134/256
debug2: bits set: 518/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: check_host_in_hostfile: filename /root/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 2
debug3: check_host_in_hostfile: filename /root/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 2
debug1: Host 'node1' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:2
debug2: bits set: 524/1024
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
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /root/.ssh/identity (0x556370)
debug2: key: /root/.ssh/id_rsa ((nil))
debug2: key: /root/.ssh/id_dsa ((nil))
debug1: Authentications that can continue: publickey,keyboard-interactive
debug3: start over, passed a different list publickey,keyboard-interactive
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /root/.ssh/identity
debug3: send_pubkey_test
debug2: we sent a publickey packet, wait for reply
Connection closed by 192.168.0.100


// SSH Logfile on node1:
Mar 15 11:21:14 [sshd] debug1: rexec start in 4 out 4 newsock 4 pipe 6 
sock 7
Mar 15 11:21:14 [sshd] debug1: Forked child 1817.
Mar 15 11:21:14 [sshd] debug1: inetd sockets after dupping: 3, 3
Mar 15 11:21:14 [sshd] Connection from 192.168.0.200 port 37281
Mar 15 11:21:14 [sshd] debug1: Client protocol version 2.0; client 
software version OpenSSH_3.9p1
Mar 15 11:21:14 [sshd] debug1: match: OpenSSH_3.9p1 pat OpenSSH*
Mar 15 11:21:14 [sshd] debug1: Enabling compatibility mode for protocol 2.0
Mar 15 11:21:14 [sshd] debug1: Local version string SSH-2.0-OpenSSH_3.9p1
Mar 15 11:21:14 [sshd] debug1: PAM: initializing for "root"
Mar 15 11:21:14 [sshd] debug1: PAM: setting PAM_RHOST to "node2"
Mar 15 11:21:14 [sshd] debug1: PAM: setting PAM_TTY to "ssh"
Mar 15 11:21:14 [sshd] debug1: temporarily_use_uid: 0/0 (e=0/0)
Mar 15 11:21:14 [sshd] debug1: trying public key file 
/root/.ssh/authorized_keys
Mar 15 11:21:14 [sshd] debug1: restore_uid: 0/0
Mar 15 11:21:14 [sshd] debug1: temporarily_use_uid: 0/0 (e=0/0)
Mar 15 11:21:14 [sshd] debug1: trying public key file 
/root/.ssh/authorized_keys2


// Messagelog on node1:
Mar 15 11:21:14 [sshd] Connection from 192.168.0.200 port 37281
Mar 15 11:21:14 [kernel] sshd[1817]: segfault at 0000000000000003 rip 
0000002a9615274d rsp 0000007fbfffc290 error 6


// Public key file:
-rw-------  1 root root 2.4K Mar 15 11:02 /root/.ssh/authorized_keys2

Any ideas?

Thanks for your help.

greetings

-- 
Daniel Khan
Technische Leitung
Gesch?ftsf?hrender Gesellschafter

Ventigo
Werbung . IT . Marketing GmbH

Kornstrasse 10 4060 Leonding
T. +43 (0) 732 37 09 60 | F. +43 (0) 732 37 09 60 10
http://www.ventigo.com | office at ventigo.com

Darren Tucker

2005-Mar-15 11:21 UTC

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Segmentation fault on public key authentification

Daniel Khan wrote:> after some weeks of operation and updates one server of mine needed a 
> reboot.
> Now authentification with public key causes a segfault.
One of those updates didn't happen to be an openssl one, did it?  Since 
it's while reading keys that's a good place to start looking.

I vaguely recall a problem on amd64 (in the asm?), although it should 
not be in the current openssl.  (Found it in the list archives, it was a 
SIGFPE not SEGV so it's probably not related.
> // Messagelog on node1:
> Mar 15 11:21:14 [sshd] Connection from 192.168.0.200 port 37281
> Mar 15 11:21:14 [kernel] sshd[1817]: segfault at 0000000000000003 rip 
> 0000002a9615274d rsp 0000007fbfffc290 error 6[...]

Your best bet is to get a stack trace of sshd using gdb.  To do this, as 
root (I'm using port 2022 for this example):

# gdb /path/to/sshd
(gdb) set args -ddd -p 2022 -o useprivilegeseparation=no
(gdb) run
[now connect and wait for the failure]
(gdb) backtrace
> // Public key file:
> -rw-------  1 root root 2.4K Mar 15 11:02 /root/.ssh/authorized_keys2
That looks to have changed recently, does the problem persist if you 
remove the recent entries?
> Any ideas?
4.0p1 is out, you could try that.

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
     Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

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