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[Nagios-devel] Re: Major Secuirty Hole in Netsaint/Nagios.

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[Nagios-devel] Re: Major Secuirty Hole in Netsaint/Nagios.

Postby Guest » Thu Jun 27, 2002 9:04 pm

Tyler -

Thanks for the note. I'm forwarding this to the nagios-devel and
nagiosplug-devel lists, as I think this should be discussed there
with others before making changes.

As far as patches are concerned, I won't be able to make any until at
least next week. My cable provider just did an "upgrade" which now
puts me 18 hops away from the DHCP server - this caused the ISC DHCP
client on my LRP box to croak (TTL is hardcoded to16 in the
DHCPDISCOVER packet), so I've been fighting with trying to recompile
a hacked version of the client that will actually run properly on my
firewall. To top that off, I just discovered that the power supply
in my development box died sometime in the past few days and my case
is a nice toasty 110 degrees.... So I have to wait until it cools
down before trying to build a new box tomorrow or this weekend. I
love the timing of problems... :-)

--

Anyway, on to the issue at hand. I had been thinking about stripping
all single and double quotes out of the plugin output, so this might
was well be the time to do it all. This of course will break any
plugin that returns a hyperlink in the output.

I would like to keep the following characters, available for output,
as they are more benign without the help of others, especially is
quoted properly in notification commands, etc:

(,),!,?

It was not mentioned, but % is also a potentially nasty character,
but I still think it should stay (e.g. for packet loss percentages in
check_ping, check_disk, etc). It all comes down to a tradeoff
between security and flexibility. I believe that the five characters
I mention should be okay, as long as notification commands, etc.
contain quotes to prevent the shell from interpreting them. That's
more of a user education issue than anything else.

BTW, although the message only mentioned stripping these chars from
plugin output (and acknowledgements), I should probably also strip
these from names of hosts, services, etc. Anyone see a good reason
not to strip these characters?



On 27 Jun 2002 at 17:31, Tyler Lund wrote:

> Hello,
>
> I have found what I think to be a major security flaw in the current
> stable 0.0.7 release of Netsaint. From what I can tell, this flaw
> also exists in the current 1.0 beta 3 release of Nagios.
>
> Basically the macro_output string does not get checked for shell
> interpreted characters prior to being executed by popen() in my_sysem().
>
> This was discovered when attempting to insert an apostrophie character
> into an ack command and noting that the character was interpreted by
> the shell. Further investigation revealed that ANY special shell
> character will be interpreted, including a backtick ` character. This
> will allow anyone acking an alarm to execute arbitrary commands on the
> server as the netsaint user.
>
> Extapolating, this macro is also used to store output from service
> checks, including strings passed to it from NRPE and other agents.
> Using this method, an attacker would be able to execute commands on the
> central netsaint server by modifying output from a monitored host. It
> would be pretty trivial to gain access to the central server depending
> on the permissions of the user under which netsaint is running.
>
> Has this issue been addressd before? I've searched mailing lists and
> Changelogs to no avail. I'm sure this can be implimented
> in a cleaner fashion, but I've patched my 0.0.7 source files
> to sterilize macros for shell execution:
>
> char *sanitize_shell_string(char *str)
> /* takes string and escapes all metacharacters. should be used before
> including string in system() or similar call. */
> {
> int i,j = 0;
> char *new = malloc(sizeof(char) * (strlen(str) * 2 + 1));
> for (i = 0; i < strlen(str); i++) {
> switch (str[i]) {
> case '|': case '&': case ';': case '(': case ')': case '<':
> case '>': case '\'': case '"': case '*': case '?': case '\\':
> case '[': case ']': case '$': case '!': case '#': case '`':
> case '{': case '}':
> new[j] = '\\';
> j++;
> break;
> d

...[email truncated]...


This post was automatically imported from historical nagios-devel mailing list archives
Original poster: nagios@nagios.org
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