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From: swamp-dog AT ntlworld DOT com (Guy Harrison)
To: <cygwin AT cygwin DOT com>
Subject: Re: sshd and fstat
Date: Thu, 17 Jan 2002 18:41:59 GMT
Reply-To: swamp-dog AT ntlworld DOT com
Message-ID: <3c4716a0.875131242@smtp.ntlworld.com>
References: <3c46d28e DOT 857705044 AT post DOT ntlworld DOT com> <3C46E6E0 DOT 9030900 AT cportcorp DOT com>
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On Thu, 17 Jan 2002 09:59:44 -0500, Peter Buckley
<peter DOT buckley AT cportcorp DOT com> wrote:

>IIRC, SYSTEM should be the owner of the keys. And it is highly 
>recommended that the service be run as SYSTEM. Check out 
>http://tech.erdelynet.com for more info on the permissions for the key 
>files etc.

Info is much appreciated. The service is running as SYSTEM though, and I
had also run the script from tech.erdelynet.com. For verification is
this correct for /etc... ?

-rw-r--r--  1 Administ Administ  955 Jan 13 06:43 ssh_config
-rw-------  1 SYSTEM   SYSTEM    668 Oct 29 21:37 ssh_host_dsa_key
-rw-r--r--  1 Administ Administ  606 Oct 29 21:37 ssh_host_dsa_key.pub
-rw-------  1 SYSTEM   SYSTEM    531 Oct 29 21:36 ssh_host_key
-rw-r--r--  1 Administ Administ  335 Oct 29 21:36 ssh_host_key.pub
-rw-------  1 SYSTEM   SYSTEM    887 Oct 29 21:36 ssh_host_rsa_key
-rw-r--r--  1 Administ Administ  226 Oct 29 21:36 ssh_host_rsa_key.pub
-rw-r--r--  1 Administ None     1.5k Jan 17 14:43 sshd_config

As for the files in the individual /home/.ssh directories, assuming the
script worked ok, they should be owned by the relevent /home owner?
Incidentally I did try changing their ownership to SYSTEM but to no
avail.

>Guy Harrison wrote:
>
>> Hi,
>> 
>> Not knowing anything about SSH I didn't realise openssh-3.0.2p1-4 (and
>> former) versions shouldn't have been asking for a password with the
>> correct keys at either end. I assumed I'd got something in a mess. It
>> appears not.
>> 
>> In the end I compiled openssh so I could get a bit more information on
>> the failure.
>> 
>> <snippet auth.c>
>> int
>> secure_filename(FILE *f, const char *file, struct passwd *pw,
>>     char *err, size_t errlen)
>> {
>> 	uid_t uid = pw->pw_uid;
>> 	char buf[MAXPATHLEN], homedir[MAXPATHLEN];
>> 	char *cp;
>> 	struct stat st;
>> int zzz;
>> 	if (realpath(file, buf) == NULL) {
>> 		snprintf(err, errlen, "realpath %s failed: %s", file,
>> 		    strerror(errno));
>> 		return -1;
>> 	}
>> 	if (realpath(pw->pw_dir, homedir) == NULL) {
>> 		snprintf(err, errlen, "realpath %s failed: %s",
>> pw->pw_dir,
>> 		    strerror(errno));
>> 		return -1;
>> 	}
>> log("realpath=[%s][%s]",buf,homedir);
>> 	/* check the open file to avoid races */
>> zzz = fstat(fileno(f), &st);
>> log("st_uid=[%d] pw_uid=[%d]",st.st_uid,uid);
>> 	if ((zzz < 0) ||
>> 	    (st.st_uid != 0 && st.st_uid != uid) ||
>> 	    (st.st_mode & 022) != 0) {
>> 		snprintf(err, errlen, "bad ownership or modes for file
>> %s",
>> 		    buf);
>> 		return -1;
>> 	}
>> <snippet /auth.c>
>> 
>> When run as a service sshd is emitting...
>> 
>> The description for Event ID ( 0 ) in Source ( /usr/sbin/sshd.exe )
>> could not be found. It contains the following insertion string(s):
>> /usr/sbin/sshd.exe : Win32 Process Id = 0x1B0 : Cygwin Process Id =
>> 0x1B0 : debug1: temporarily_use_uid: 500/513 (e=18).
>> 
>> The description for Event ID ( 0 ) in Source ( /usr/sbin/sshd.exe )
>> could not be found. It contains the following insertion string(s):
>> /usr/sbin/sshd.exe : Win32 Process Id = 0x1B0 : Cygwin Process Id =
>> 0x1B0 :
>> realpath=[/home/Administrator/.ssh/authorized_keys][/home/Administrator].
>> 
>> The description for Event ID ( 0 ) in Source ( /usr/sbin/sshd.exe )
>> could not be found. It contains the following insertion string(s):
>> /usr/sbin/sshd.exe : Win32 Process Id = 0x1B0 : Cygwin Process Id =
>> 0x1B0 : st_uid=[18] pw_uid=[500].
>> 
>> The description for Event ID ( 0 ) in Source ( /usr/sbin/sshd.exe )
>> could not be found. It contains the following insertion string(s):
>> /usr/sbin/sshd.exe : Win32 Process Id = 0x1B0 : Cygwin Process Id =
>> 0x1B0 : Authentication refused: bad ownership or modes for file
>> /home/Administrator/.ssh/authorized_keys.
>> 
>> Seems to think authorized_keys is owned by SYSTEM:18 but it isn't.
>> Stopping sshd as a service and running from within bash "sshd -d" works
>> fine and emits...
>> 
>> debug1: temporarily_use_uid: 500/513 (e=500)
>> debug1: trying public RSA key file
>> /home/Administrator/.ssh/authorized_keys
>> realpath=[/home/Administrator/.ssh/authorized_keys][/home/Administrator]
>> st_uid=[500] pw_uid=[500]
>> debug1: restore_uid
>> Accepted rsa for Administrator from 192.168.0.1 port 2446
>> 
>> ...which isn't the end of it. I fired up a bash shell, launched from a
>> service with SYSTEM authority expecting a failure...
>> 
>> debug1: temporarily_use_uid: 500/513 (e=18)
>> debug1: trying public key file /home/Administrator/.ssh/authorized_keys
>> realpath=[/home/Administrator/.ssh/authorized_keys][/home/Administrator]
>> st_uid=[500] pw_uid=[500]
>> 
>> ...but it worked, both as "sshd -d" and as a straight "sshd" (so it
>> forked in case that was it).
>> 
>> fstat will only fail when sshd is running as a service as SYSTEM. The
>> only viable approach I can think of at this point is to attach gdb to
>> the process forked by sshd and I can't for the life of me figure out how
>> to do that. I hope this info is useful to you folks with more intimate
>> knowledge 'cos I'm stuck! :-|
>> 
>> 
>> 
>
>
>-- 
>Your mouse has moved.
>Windows NT must be restarted for the change to take effect.
>Reboot now?  [OK]
>
>--

-- 
swamp-dog AT ntlworld DOT com

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