ssh-keysign bug?

[Christopher Craig Penney Jr]

I use ssh in a batch environment (www.pbspro.com) and am using host based 
authentication to allow sshes between some resources.  When I converted from 
openssh 3.1 to newer versions (up to an including 3.8 where ssh-keysign was 
moved to a standalone binary) I had issues with ssh-keysign failing with the 
error "bad fd".  A little exploring showed that this was happening because 
in the batch environment the ssh command did not have a STDIN opened and the 
socket used for IPC was being created as fd 0. 

You can see the difference here from a ls -l of /proc/pid/fd right after 
buffer_get_int(&b) is called in ssh-keysign's main(): 

 --- Normal SSH:
0 -> /dev/pts/3
1 -> /dev/pts/3
2 -> /dev/pts/3
3 -> socket:[37629928]
5 -> pipe:[37629941]
6 -> pipe:[37629942]
 --- Normal SSH-KEYSIGN:
0 -> pipe:[37629941]
1 -> pipe:[37629942]
2 -> /dev/pts/3
3 -> socket:[37629928] 

 --- Batch run SSH:
0 -> socket:[16485502]
1 -> /var/spool/pbs/spool/311683.batc.OU
2 -> /var/spool/pbs/spool/311683.batc.OU
4 -> pipe:[16485513]
5 -> pipe:[16485514]
 --- Batch run SSH-KEYSIGN:
0 -> pipe:[16485513]
1 -> pipe:[16485514]
2 -> /var/spool/pbs/spool/311683.batc.OU 

The problem is resolved if, in the batch script, you redirect /dev/null into 
the ssh command so the ssh command has a valid STDIN.  I'm not sure if this 
is a bug or intended behavior. 

  Chris