tomac/yersiniaFramework de ataque de rede de Camada 2 para explorar protocolos STP e CDP, permitindo ataques de DoS, sequestro de função raiz e exaustão de memória em switches Cisco.
Vamos enviar algumas conf BPDUs afirmando ser a raiz!!! Ao enviar continuamente conf BPDU com root pathcost 0,
bridge id gerado aleatoriamente (e, portanto, o mesmo root id), e alguns valores padrão para outros campos,
tentamos irritar os switches próximos a nós, causando um DoS ao tentarem analisar e recalcular seus motores STP.
Source MAC: gerado aleatoriamente.
Destination MAC: 01:80:c2:00:00:00
Bridge ID: 8000:source_mac
Root ID: 8000:source_mac
Hello time: 2
Forward delay: 15
Max age: 20
Root pathcost: 0
<output do log do cisco>
01:20:26: STP: VLAN0001 heard root 32768-d1bf.6d60.097b on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-9ac6.0f72.7118 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-85a3.3662.43dc on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-3d84.bc1c.918e on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-b2e2.1a12.dbb4 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-4ba6.2d45.5844 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-deb0.4f14.7288 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-4879.8036.0e24 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-2776.e340.9222 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-299e.de76.c07d on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-d38b.bc5b.e90d on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-78ee.0205.afdb on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-b32b.e969.81b1 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-b16b.c428.88a3 on Fa0/8
01:20:26: STP: VLAN0001 heard root 32768-dd01.1436.9044 on Fa0/8
</output>
Este ataque envia continuamente tcn BPDUs, fazendo com que o switch raiz envie conf BPDUs reconhecendo a mudança.
Além disso, o switch raiz enviará notificações de mudança de topologia para os membros da árvore, e eles terão
que recalcular seu motor STP para aprender a nova mudança.
Source MAC: gerado aleatoriamente.
Destination MAC: 01:80:c2:00:00:00
<output do log do cisco>
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
01:35:39: STP: VLAN0001 Topology Change rcvd on Fa0/8
</output>
Agora nosso objetivo é obter a função de raiz da árvore. Como podemos realizar isso? Basta ouvir a rede
para descobrir qual é a função de raiz e começar a enviar conf BPDU com prioridade mais baixa para se tornar raiz.
Source MAC: o mesmo do BPDU farejado.
Destination MAC: o mesmo do BPDU farejado.
Bridge ID: o farejado ligeiramente modificado para ter uma prioridade mais baixa
Root ID: 8000: mesmo que bridge id.
Hello time: o mesmo do BPDU farejado.
Forward delay: o mesmo do BPDU farejado.
Max age: o mesmo do BPDU farejado.
Root pathcost: o mesmo do BPDU farejado.
<output do log do cisco>
01:58:48: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/8
01:58:48: supersedes 32769-000e.84d5.2280
01:58:48: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/8, cost 19
</output>
Pretendemos ser outro switch estranho brincando com STP e anunciando nosso root id :)
Ao enviar config BPDUs com prioridade decrescente automaticamente, podemos causar eleições infinitas de raiz na árvore STP.
Seria algo parecido com recontar os votos da eleição para determinar o vencedor (lembra-se da Flórida?)
<output do log do cisco>
00:20:21: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
00:20:21: supersedes 32769-000e.84d5.2280
00:20:21: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
00:20:23: STP: VLAN0001 heard root 32769-000e.84d3.2280 on Fa0/9
00:20:23: supersedes 32769-000e.84d4.2280
00:20:23: STP: VLAN0001 new root is 32769, 000e.84d3.2280 on port Fa0/9, cost 19
00:20:25: STP: VLAN0001 heard root 32769-000e.84d2.2280 on Fa0/9
00:20:25: supersedes 32769-000e.84d3.2280
00:20:25: STP: VLAN0001 new root is 32769, 000e.84d2.2280 on port Fa0/9, cost 19
00:20:27: STP: VLAN0001 heard root 32769-000e.84d1.2280 on Fa0/9
00:20:27: supersedes 32769-000e.84d2.2280
00:20:27: STP: VLAN0001 new root is 32769, 000e.84d1.2280 on port Fa0/9, cost 19
00:20:29: STP: VLAN0001 heard root 32769-000e.84d0.2280 on Fa0/9
00:20:29: supersedes 32769-000e.84d1.2280
00:20:29: STP: VLAN0001 new root is 32769, 000e.84d0.2280 on port Fa0/9, cost 19
00:20:31: STP: VLAN0001 heard root 32769-000e.84cf.2280 on Fa0/9
00:20:31: supersedes 32769-000e.84d0.2280
00:20:31: STP: VLAN0001 new root is 32769, 000e.84cf.2280 on port Fa0/9, cost 19
00:20:33: STP: VLAN0001 heard root 32769-000e.84ce.2280 on Fa0/9
00:20:33: supersedes 32769-000e.84cf.2280
00:20:33: STP: VLAN0001 new root is 32769, 000e.84ce.2280 on port Fa0/9, cost 19
00:20:35: STP: VLAN0001 heard root 32769-000e.84cd.2280 on Fa0/9
00:20:35: supersedes 32769-000e.84ce.2280
00:20:35: STP: VLAN0001 new root is 32769, 000e.84cd.2280 on port Fa0/9, cost 19
00:20:37: STP: VLAN0001 heard root 32769-000e.84cc.2280 on Fa0/9
00:20:37: supersedes 32769-000e.84cd.2280
00:20:37: STP: VLAN0001 new root is 32769, 000e.84cc.2280 on port Fa0/9, cost 19
00:20:39: STP: VLAN0001 heard root 32769-000e.84cb.2280 on Fa0/9
00:20:39: supersedes 32769-000e.84cc.2280
00:20:39: STP: VLAN0001 new root is 32769, 000e.84cb.2280 on port Fa0/9, cost 19
</output>
Desta vez tentamos exaurir o processo de eleição da raiz. Conseguimos nos tornar raiz na árvore STP,
mas paramos de enviar config BPDUs até que atinja max_age segundos (geralmente 20), forçando um novo
processo de eleição.
<output do log do cisco>
02:02:43: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
02:02:43: supersedes 32769-000e.84d5.2280
02:02:43: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
02:03:03: STP: VLAN0001 we are the spanning tree root
02:03:04: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
02:03:04: supersedes 32769-000e.84d5.2280
02:03:04: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
02:03:04: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:06: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:08: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:10: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:12: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:14: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:16: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:18: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:20: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:22: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:24: STP: VLAN0001 we are the spanning tree root
02:03:24: STP: VLAN0001 heard root 32769-000e.84d4.2280 on Fa0/9
02:03:24: supersedes 32769-000e.84d5.2280
02:03:24: STP: VLAN0001 new root is 32769, 000e.84d4.2280 on port Fa0/9, cost 19
02:03:24: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:26: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:28: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:30: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:32: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:34: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:36: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:38: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:40: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:42: STP: VLAN0001 sent Topology Change Notice on Fa0/9
02:03:44: STP: VLAN0001 we are the spanning tree root
</output>
Use segurança de porta e desabilite STP nas portas que não requerem STP. Para informações sobre segurança de porta, consulte o seguinte url: http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter09186a0080150bcd.html
Se você está usando o recurso portfast na sua configuração STP, habilite também o guardião BPDU (BPDU guard) para evitar esses ataques quando a porta entra automaticamente no estado de encaminhamento: http://www.cisco.com/warp/public/473/65.html
Use o recurso root guard para evitar que dispositivos maliciosos se tornem raiz: http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800ae96b.shtml
Interessante Tese de Mestrado de Guillermo Marro: http://seclab.cs.ucdavis.edu/papers/Marro_masters_thesis.pdf
Oleg K. Artemjev, Vladislav V. Myasnyankin. Fun with the Spanning Tree Protocol http://phrack.org/issues/61/12.html
Dispositivos Cisco sempre falaram uma linguagem diferente para se comunicar entre si, para dizer a todos que estão vivos e quais recursos interessantes possuem. CDP significa Cisco Discovery Protocol. Por meio dessa linguagem particular, os dispositivos Cisco criam um mundo virtual onde todos são felizes e não há crime algum. Ou pelo menos parece ser assim, já que muitos administradores de rede não se preocupam com o CDP ainda. Embora algumas informações que podem ser enviadas em um pacote CDP ainda não sejam documentadas (CDP é um protocolo proprietário e parece que a Cisco não quer fornecer detalhes sobre ele), pelo menos um ataque antigo (ainda válido) é conhecido, e há uma implementação pública (FX fez isso!).
Este ataque é um DoS que tenta esgotar a memória do dispositivo para que ele não possa alocar mais memória para qualquer processo do dispositivo. Como podemos fazer isso? Simplesmente enviando pacotes CDP com dados falsos simulando dispositivos Cisco reais. O dispositivo alvo começará a alocar memória em sua tabela CDP para salvar as informações do novo vizinho, mas sem saber que terá milhares ou milhões de novos amigos.
Outro ataque implementado no código atual é a capacidade de configurar um novo dispositivo Cisco virtual designado apenas para fazer uma pequena bagunça, tentando confundir os administradores de rede.
Captura de tela do ataque em execução:
Saída de um roteador Cisco 2503:
athens#sh mem
Head Total(b) Used(b) Free(b) Lowest(b) Largest(b)
Processor 4873C 3893444 3893444 0 0 0
I/O 400000 2097152 2097088 64 64 64
<log>
%SCHED-3-THRASHING: Process thrashing on watched queue 'CDP packets' (count 57).
-Process= "CDP Protocol", ipl= 6, pid= 9
-Traceback= 3159232 31594DE 3201660
%LANCE-5-COLL: Unit 0, excessive collisions. TDR=7
%SCHED-3-THRASHING: Process thrashing on watched queue 'CDP packets' (count 57).
-Process= "CDP Protocol", ipl= 6, pid= 9
-Traceback= 3159232 31594DE 3201660
%SYS-2-MALLOCFAIL: Memory allocation of 100 bytes failed from 0x3201B3E, pool Processor, alignment 0
-Process= "CDP Protocol", ipl= 0, pid= 9
-Traceback= 314E8A4 314FA06 3201B46 32016C8
%SCHED-3-THRASHING: Process thrashing on watched queue 'CDP packets' (count 57).
-Process= "CDP Protocol", ipl= 6, pid= 9
-Traceback= 3159232 31594DE 3201660
%SYS-2-MALLOCFAIL: Memory allocation of 100 bytes failed from 0x3201B3E, pool Processor, alignment 0
-Process= "CDP Protocol", ipl= 0, pid= 9
-Traceback= 314E8A4 314FA06 3201B46 32016C8
%SYS-2-MALLOCFAIL: Memory allocation of 100 bytes failed from 0x3201B3E, pool Processor, alignment 0
-Process= "CDP Protocol", ipl= 0, pid= 9
-Traceback= 314E8A4 314FA06 3201B46 32016C8
</log>
E alguns minutos depois de interromper o ataque, o roteador surpreendentemente trava por vários segundos, e depois o expulsa do terminal :)
<log>
%SYS-3-CPUHOG: Task ran for 16884 msec (69/69), Process = Exec, PC = 3158D42
-Traceback= 3158CEE 3158D4A 30F7330 30F742A 30FF3A4 30FEF76 30FEF1C 3116860
</log>
Saída de um switch Cisco 2950:
00:06:08: %SYS-2-MALLOCFAIL: Memory allocation of 224 bytes failed from 0x800118D0, alignment 0
Pool: Processor Free: 0 Cause: Not enough free memory
Alternate Pool: I/O Free: 32 Cause: Not enough free memory
-Process= "CDP Protocol", ipl= 0, pid= 26
-Traceback= 801DFC30 801E1DD8 800118D8 80011218 801D932C 801D9318
00:06:08: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:09: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:10: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:11: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:12: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:13: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:14: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:15: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:16: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:17: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:18: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:19: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:20: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:21: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:22: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:23: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:38: %SYS-2-MALLOCFAIL: Memory allocation of 140 bytes failed from 0x801E28BC, alignment 0
Pool: Processor Free: 0 Cause: Not enough free memory
Alternate Pool: I/O Free: 32 Cause: Not enough free memory
-Process= "Calhoun Statistics Process", ipl= 0, pid= 21
-Traceback= 801DFC30 801E1DD8 801E28C4 801F13BC 801F1470 802F7C90 802F9190 802F9788 801D932C 801D9318
00:06:38: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:39: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:40: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:41: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:42: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:44: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:45: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:46: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:47: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:48: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:49: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:50: ../src-calhoun/strata_stats.c at line 137: can't not push event list
00:06:59: %SYS-3-CPUHOG: Task ran for 2076 msec (11/10), process = Net Background, PC = 801ABD40.
-Traceback= 801ABD48 801D932C 801D9318
E então, o processo CDP cai completamente, mesmo quando paramos o ataque. Sem mais bebês CDP...