[ECOS] Re: SNMP GETBULK leaks 50k per request -- security issue

Tad ecos_removethispart@ds3switch.com
Fri Jun 29 10:04:00 GMT 2007


If patched, snmp_api.c also needs 3 changes shown in SF tree.  2 points 
initialize ->data = 0 and snmp_free_var() free's if data != 0.

Tad wrote:
> ...when snmp_send() fails.
>
> Tad wrote:
>> A GETBULK request requiring > 8k bytes in the response 
>> (snmp_api.c:PACKET_LENGTH or sendto max)
>> forgets to free the 50k pdu malloc'ed.
>>
>> Should be able to crash any ecos snmp system with a couple:
>> bulkget -Cr50 -v 2c -c public 192.168.1.199 system system system 
>> system system icmp system icmp
>> which will eat 5 retries x50k at a time
>>
>> Basically, the snmp_agent.c we're using is POS full of memory leaks 
>> if snmp_send or other errors occur.
>>
>> I grabbed the latest v4.2 branch from SF of snmp_agent.c, 
>> snmp_agent.h, and snmp_api.h which seem to compile for ecos with 
>> virtually no changes (used the ECOS includes for snmp_agent.c)
>>
>> The latest snmp_agent.c seems to do a nice job of cleaning up memory 
>> and has a slightly faster SET operation.
>>
>> http://net-snmp.cvs.sourceforge.net/net-snmp/net-snmp/agent/snmp_agent.c?view=log&r1=1.100&pathrev=V4-2-patches 
>>
>> et. al.
>>
>

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