[Nagiosplug-devel] [ nagiosplug-Bugs-741296 ] check_dns.c segfault with -a and NXDOMAIN

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Bugs item #741296, was opened at 2003-05-21 14:28
Message generated for change (Comment added) made by kdebisschop
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Category: None
Group: CVS
Status: Open
Resolution: None
Priority: 5
Submitted By: David Maynard (dpmaynard)
Assigned to: Nobody/Anonymous (nobody)
Summary: check_dns.c segfault with -a and NXDOMAIN

Initial Comment:
check_dns.c 1.13 from CVS compiled and run under 
Red Hat 7.1 and testing against bind-8.2.3+patches on 
a Cobalt generates a segmentation fault if the requested 
domain does not exist and the "-a" flag is specified.

The "address" variable is NULL when the code reaches 
line 183 and attempts a strcmp.  The null pointer to 
strcmp generates a segfault.

Arguably, this is a bug in the parsing of the "address" 
variable since it probably shouldn't be a NULL at this 
point in the code.  However, the code for "-a" is 
predicated on STATE_OK, so if something earlier in the 
code indicates STATE_WARNING (e.g., because it 
detects a NXDOMAIN return), then the "-a" check will 
not be performed and Nagios will "miss" the CRITICAL 
error.  (If I tell it to match an expected address, it is 
critical if it doesn't exist.)

As a result, my "fix" (to achieve the results I need), was 
to change the code for the "-a" test to include a check 
for a null address pointer.  My patch attached.

-dpm


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>Comment By: Karl DeBisschop (kdebisschop)
Date: 2003-05-31 10:00

Message:
Logged In: YES 
user_id=1671

IMO, your thoughts about where the true bug lies are correct.

And we know form experince that other implementations will
segfault on your patch because you try to print a null string.

I take you point about failing to note that the address is
null and move the check up to that point in the code.

This is the patch I have applied.

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