Este documento fornece uma configuração de exemplo para a inspeção de conexões de entrada do Simple Mail Transfer Protocol (SMTP) ou do Extended Simple Mail Transfer Protocol (ESMTP) utilizando o Cisco IOS® Firewall no Cisco IOS. Tal inspeção é similar à característica MailGuard encontrada nos Cisco PIX 500 Series Security Appliances.
Não existem requisitos específicos para este documento.
As informações neste documento são baseadas nestas versões de software e hardware:
Cisco IOS Software Release 12.3(4)T ou Mais Recente
Cisco 3640 Router
As informações neste documento foram criadas a partir de dispositivos em um ambiente de laboratório específico. Todos os dispositivos utilizados neste documento foram iniciados com uma configuração (padrão) inicial. Se a sua rede estiver ativa, certifique-se de que entende o impacto potencial de qualquer comando.
Consulte as Convenções de Dicas Técnicas da Cisco para obter mais informações sobre convenções de documentos.
A inspeção de SMTP causa comandos S TP ser inspecionado para comandos ilegais. Os pacotes com comandos ilegais são alterados a um teste padrão de “xxxx” e enviados ao server. Este processo faz com que o server envie uma resposta negativa, que force o cliente a emitir um comando válido. Um comando ilegal S TP é comando any à exceção destes comandos:
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A inspeção de ESMTP opera-se da mesma forma que a inspeção de SMTP faz. Os pacotes com comandos ilegais são alterados a um teste padrão “xxxx” e enviados ao server, que provoca uma resposta negativa. Um comando ilegal ESMTP é comando any à exceção destes comandos:
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A inspeção de ESMTP igualmente examina estes Ramais através de uma inspeção mais profunda do comando:
Declaração do tamanho de mensagem (TAMANHO)
Fila remota que processa a declaração (ETRN)
O binário MIMICA (BINARYMIME)
Encanamento do comando
Autenticação
Notificação de Status de entrega (DSN)
Código de status aumentado (ENHANCEDSTATUSCODE)
MIMEtransport de 8 bits (8BITMIME)
Nota: O S TP e a inspeção de ESMTP não podem ser configurados simultaneamente. Uma tentativa de configurar ambos os resultados em um Mensagem de Erro.
Nota: No Cisco IOS Software Release 12.3(4)T e Mais Recente, o Cisco IOS Firewall já não cria entradas de lista de acesso dinâmico para permitir o tráfego. O Cisco IOS Firewall mantém agora uma tabela do estado de sessão para controlar a segurança de conexões inspecionadas.
Nesta seção, você encontrará informações para configurar os recursos descritos neste documento.
Nota: Use a Command Lookup Tool (somente clientes registrados) para obter mais informações sobre os comandos usados nesta seção.
Este documento utiliza a seguinte configuração de rede:
Este documento utiliza esta configuração:
3640 Router |
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3640-123#show running-config Building configuration... Current configuration : 1432 bytes ! version 12.3 service config service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname 3640-123 ! boot-start-marker boot-end-marker ! enable password 7 02050D4808095E731F ! no aaa new-model ! resource policy ! voice-card 3 ! ip subnet-zero ! ! ip cef no ip dhcp use vrf connected ! ! !--- This is the Cisco IOS Firewall configuration. !--- IN-OUT is the inspection rule for traffic that flows !--- from the inside interface of the router to the outside interface. ip inspect name IN-OUT tcp ip inspect name IN-OUT udp ip inspect name IN-OUT ftp ip inspect name IN-OUT http ip inspect name IN-OUT icmp !--- OUT-IN is the inspection rule for traffic that flows !--- from the outside interface of the router to the inside interface. !--- This rule is where SMTP/ESMTP inspection is specified. ip inspect name OUT-IN smtp ! no ip ips deny-action ips-interface ! no ftp-server write-enable ! ! ! ! controller T1 3/0 framing sf linecode ami ! ! ! ! ! !--- The outside interface. interface Ethernet2/0 ip address 172.22.1.16 255.255.255.0 !--- Apply the access list to permit SMTP/ESMTP connections !--- to the mail server. This also allows Cisco IOS Firewall !--- to inspect SMTP or ESMTP commands. ip access-group 101 in ip nat outside !--- Apply the inspection rule OUT-IN inbound on this interface. This is !--- the rule that defines SMTP/ESMTP inspection. ip inspect OUT-IN in ip virtual-reassembly half-duplex ! interface Serial2/0 no ip address shutdown ! !--- The inside interface. interface Ethernet2/1 ip address 10.10.10.1 255.255.255.0 ip nat inside !--- Apply the inspection rule IN-OUT inbound on this interface. ip inspect IN-OUT in ip virtual-reassembly half-duplex ! ip http server no ip http secure-server ip classless ip route 0.0.0.0 0.0.0.0 172.22.1.1 ! ! !--- The static translation for the mail server. ip nat inside source static 10.10.10.2 172.22.1.110 ip nat inside source static 10.10.10.5 172.22.1.111 ! !--- The access list to permit SMTP and ESMTP to the mail server. !--- Cisco IOS Firewall inspects permitted traffic. access-list 101 permit tcp any host 172.22.1.110 eq smtp ! ! ! control-plane ! ! ! voice-port 1/0/0 ! voice-port 1/0/1 ! voice-port 1/1/0 ! voice-port 1/1/1 ! ! ! ! ! ! ! ! line con 0 line aux 0 line vty 0 4 password 7 121A0C0411045D5679 login ! ! end |
Use esta seção para confirmar se a sua configuração funciona corretamente.
A Output Interpreter Tool (apenas para clientes registrados) (OIT) suporta determinados comandos show. Use a OIT para exibir uma análise da saída do comando show.
a mostra IP inspeciona tudo — Verifica a configuração de regras da inspeção do Cisco IOS Firewall e de seu aplicativo às relações.
3640-123#show ip inspect all Session audit trail is disabled Session alert is enabled one-minute (sampling period) thresholds are [400:500] connections max-incomplete sessions thresholds are [400:500] max-incomplete tcp connections per host is 50. Block-time 0 minute. tcp synwait-time is 30 sec -- tcp finwait-time is 5 sec tcp idle-time is 3600 sec -- udp idle-time is 30 sec dns-timeout is 5 sec Inspection Rule Configuration Inspection name IN-OUT tcp alert is on audit-trail is off timeout 3600 udp alert is on audit-trail is off timeout 30 ftp alert is on audit-trail is off timeout 3600 http alert is on audit-trail is off timeout 3600 icmp alert is on audit-trail is off timeout 10 Inspection name OUT-IN smtp max-data 20000000 alert is on audit-trail is off timeout 3600 Interface Configuration Interface Ethernet2/1 Inbound inspection rule is IN-OUT tcp alert is on audit-trail is off timeout 3600 udp alert is on audit-trail is off timeout 30 ftp alert is on audit-trail is off timeout 3600 http alert is on audit-trail is off timeout 3600 icmp alert is on audit-trail is off timeout 10 Outgoing inspection rule is not set Inbound access list is not set Outgoing access list is not set Interface Ethernet2/0 Inbound inspection rule is OUT-IN smtp max-data 20000000 alert is on audit-trail is off timeout 3600 Outgoing inspection rule is not set Inbound access list is 101 Outgoing access list is not set
smtp do debug ip inspect — Indica mensagens sobre eventos da inspeção de SMTP do Cisco IOS Firewall.
Nota: Consulte Informações Importantes sobre Comandos de Depuração antes de usar comandos debug.
ausnml-3600-02#debug ip inspect smtp INSPECT SMTP Inspection debugging is on ausnml-3600-02# *Oct 18 21:51:35.886: CBAC SMTP: reply_type OTHERS *Oct 18 21:51:35.886: CBAC SMTP: OTHER REPLY - Reply len: 64, match_len:64, reply_re_state:18 *Oct 18 21:51:35.886: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:51:35.886: CBAC SMTP: OTHER REPLY match id:10 *Oct 18 21:51:35.886: CBAC SMTP: End Of Reply Line - index:0 ,len:64 !--- The client issues a command. *Oct 18 21:51:40.810: CBAC SMTP: VERB - Cmd len:1, match_len:1, cmd_re_state:9 *Oct 18 21:51:40.994: CBAC SMTP: VERB - Cmd len:2, match_len:1, cmd_re_state:24 *Oct 18 21:51:41.190: CBAC SMTP: VERB - Cmd len:3, match_len:1, cmd_re_state:40 *Oct 18 21:51:41.390: CBAC SMTP: VERB - Cmd len:4, match_len:1, cmd_re_state:56 *Oct 18 21:51:41.390: CBAC SMTP: VERB - match id:5 *Oct 18 21:51:42.046: CBAC SMTP: CMD PARAM - Cmd len:5, match_len:1, cmd_re_state:7 *Oct 18 21:51:43.462: CBAC SMTP: CMD PARAM - Cmd len:6, match_len:1, cmd_re_state:2 *Oct 18 21:51:43.594: CBAC SMTP: CMD PARAM - Cmd len:7, match_len:1, cmd_re_state:2 *Oct 18 21:51:43.794: CBAC SMTP: CMD PARAM - Cmd len:9, match_len:2, cmd_re_state:2 *Oct 18 21:51:43.994: CBAC SMTP: CMD PARAM - Cmd len:10, match_len:1, cmd_re_state:2 *Oct 18 21:51:44.194: CBAC SMTP: CMD PARAM - Cmd len:12, match_len:2, cmd_re_state:3 *Oct 18 21:51:44.194: CBAC SMTP: CMD PARAM - match id:6 *Oct 18 21:51:44.194: CBAC SMTP: End Of Command Line - index:1, len:12 !--- The server replies. *Oct 18 21:51:44.198: CBAC SMTP: reply_type OTHERS *Oct 18 21:51:44.198: CBAC SMTP: OTHER REPLY - Reply len: 11, match_len:11, reply_re_state:18 *Oct 18 21:51:44.198: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:51:44.198: CBAC SMTP: OTHER REPLY match id:10 *Oct 18 21:51:44.198: CBAC SMTP: End Of Reply Line - index:1 ,len:11 !--- The client issues a command. *Oct 18 21:51:49.482: CBAC SMTP: VERB - Cmd len:1, match_len:1, cmd_re_state:3 *Oct 18 21:51:50.222: CBAC SMTP: VERB - Cmd len:2, match_len:1, cmd_re_state:15 *Oct 18 21:51:50.618: CBAC SMTP: VERB - Cmd len:3, match_len:1, cmd_re_state:31 *Oct 18 21:51:50.954: CBAC SMTP: VERB - Cmd len:4, match_len:1, cmd_re_state:46 *Oct 18 21:51:50.954: CBAC SMTP: VERB - match id:15 *Oct 18 21:51:51.642: CBAC SMTP: CMD PARAM - Cmd len:5, match_len:1, cmd_re_state:7 *Oct 18 21:51:51.914: CBAC SMTP: CMD PARAM - Cmd len:6, match_len:1, cmd_re_state:2 *Oct 18 21:51:52.106: CBAC SMTP: CMD PARAM - Cmd len:7, match_len:1, cmd_re_state:2 *Oct 18 21:51:54.754: CBAC SMTP: CMD PARAM - Cmd len:8, match_len:1, cmd_re_state:4 *Oct 18 21:51:55.098: CBAC SMTP: CMD PARAM - Cmd len:9, match_len:1, cmd_re_state:2 *Oct 18 21:51:55.322: CBAC SMTP: CMD PARAM - Cmd len:11, match_len:2, cmd_re_state:3 *Oct 18 21:51:55.322: CBAC SMTP: CMD PARAM - match id:6 *Oct 18 21:51:55.322: CBAC SMTP: End Of Command Line - index:2, len:11 !--- The server replies. *Oct 18 21:51:55.326: CBAC SMTP: reply_type OTHERS *Oct 18 21:51:55.326: CBAC SMTP: OTHER REPLY - Reply len: 19, match_len:19, reply_re_state:3 *Oct 18 21:51:55.326: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:51:55.326: CBAC SMTP: End Of Reply Line - index:2 ,len:19 *Oct 18 21:51:57.070: CBAC SMTP: VERB - Cmd len:1, match_len:1, cmd_re_state:3 *Oct 18 21:51:57.402: CBAC SMTP: VERB - Cmd len:2, match_len:1, cmd_re_state:15 *Oct 18 21:51:58.162: CBAC SMTP: VERB - Cmd len:3, match_len:1, cmd_re_state:31 *Oct 18 21:51:58.462: CBAC SMTP: VERB - Cmd len:4, match_len:1, cmd_re_state:46 *Oct 18 21:51:58.466: CBAC SMTP: VERB - match id:15 *Oct 18 21:51:58.746: CBAC SMTP: CMD PARAM - Cmd len:5, match_len:1, cmd_re_state:7 *Oct 18 21:51:59.006: CBAC SMTP: CMD PARAM - Cmd len:6, match_len:1, cmd_re_state:2 *Oct 18 21:51:59.234: CBAC SMTP: CMD PARAM - Cmd len:7, match_len:1, cmd_re_state:2 *Oct 18 21:51:59.418: CBAC SMTP: CMD PARAM - Cmd len:9, match_len:2, cmd_re_state:2 *Oct 18 21:51:59.618: CBAC SMTP: CMD PARAM - Cmd len:10, match_len:1, cmd_re_state:2 *Oct 18 21:51:59.818: CBAC SMTP: CMD PARAM - Cmd len:12, match_len:2, cmd_re_state:3 *Oct 18 21:51:59.818: CBAC SMTP: CMD PARAM - match id:6 *Oct 18 21:51:59.818: CBAC SMTP: End Of Command Line - index:3, len:12 *Oct 18 21:51:59.818: CBAC SMTP: reply_type OTHERS *Oct 18 21:51:59.818: CBAC SMTP: OTHER REPLY - Reply len: 19, match_len:19, reply_re_state:3 *Oct 18 21:51:59.822: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:51:59.822: CBAC SMTP: End Of Reply Line - index:3 ,len:19 *Oct 18 21:52:04.974: CBAC SMTP: VERB - Cmd len:1, match_len:1, cmd_re_state:9 *Oct 18 21:52:05.170: CBAC SMTP: VERB - Cmd len:2, match_len:1, cmd_re_state:24 *Oct 18 21:52:05.326: CBAC SMTP: VERB - Cmd len:3, match_len:1, cmd_re_state:40 *Oct 18 21:52:05.526: CBAC SMTP: VERB - Cmd len:4, match_len:1, cmd_re_state:55 *Oct 18 21:52:05.526: CBAC SMTP: VERB - match id:6 *Oct 18 21:52:05.742: CBAC SMTP: CMD PARAM - Cmd len:6, match_len:2, cmd_re_state:3 *Oct 18 21:52:05.742: CBAC SMTP: CMD PARAM - match id:6 *Oct 18 21:52:05.742: CBAC SMTP: End Of Command Line - index:4, len:6 *Oct 18 21:52:05.746: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.746: CBAC SMTP: OTHER REPLY - Reply len: 54, match_len:54, reply_re_state:3 *Oct 18 21:52:05.746: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.746: CBAC SMTP: End Of Reply Line - index:4 ,len:54 *Oct 18 21:52:05.746: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.746: CBAC SMTP: OTHER REPLY - Reply len: 15, match_len:15, reply_re_state:3 *Oct 18 21:52:05.746: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.746: CBAC SMTP: End Of Reply Line - index:5 ,len:15 *Oct 18 21:52:05.746: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.746: CBAC SMTP: OTHER REPLY - Reply len: 15, match_len:15, reply_re_state:3 *Oct 18 21:52:05.746: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.746: CBAC SMTP: End Of Reply Line - index:6 ,len:15 *Oct 18 21:52:05.746: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY - Reply len: 6, match_len:6, reply_re_state:3 *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.750: CBAC SMTP: End Of Reply Line - index:7 ,len:6 *Oct 18 21:52:05.750: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY - Reply len: 19, match_len:19, reply_re_state:3 *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.750: CBAC SMTP: End Of Reply Line - index:8 ,len:19 *Oct 18 21:52:05.750: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY - Reply len: 17, match_len:17, reply_re_state:3 *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.750: CBAC SMTP: End Of Reply Line - index:9 ,len:17 *Oct 18 21:52:05.750: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY - Reply len: 6, match_len:6, reply_re_state:3 *Oct 18 21:52:05.750: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.754: CBAC SMTP: End Of Reply Line - index:10 ,len:6 *Oct 18 21:52:05.754: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.754: CBAC SMTP: OTHER REPLY - Reply len: 6, match_len:6, reply_re_state:3 *Oct 18 21:52:05.754: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.754: CBAC SMTP: End Of Reply Line - index:11 ,len:6 *Oct 18 21:52:05.754: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.754: CBAC SMTP: OTHER REPLY - Reply len: 6, match_len:6, reply_re_state:3 *Oct 18 21:52:05.754: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.754: CBAC SMTP: End Of Reply Line - index:12 ,len:6 *Oct 18 21:52:05.754: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:05.754: CBAC SMTP: OTHER REPLY - Reply len: 3, match_len:3, reply_re_state:3 *Oct 18 21:52:05.754: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:05.754: CBAC SMTP: End Of Reply Line - index:13 ,len:3 *Oct 18 21:52:15.646: CBAC SMTP: VERB - Cmd len:1, match_len:1, cmd_re_state:6 *Oct 18 21:52:15.838: CBAC SMTP: VERB - Cmd len:3, match_len:2, cmd_re_state:37 *Oct 18 21:52:16.206: CBAC SMTP: VERB - Cmd len:4, match_len:1, cmd_re_state:52 *Oct 18 21:52:16.206: CBAC SMTP: VERB - match id:9 *Oct 18 21:52:18.954: CBAC SMTP: CMD PARAM - Cmd len:6, match_len:2, cmd_re_state:3 *Oct 18 21:52:18.958: CBAC SMTP: CMD PARAM - match id:6 *Oct 18 21:52:18.958: CBAC SMTP: End Of Command Line - index:5, len:6 *Oct 18 21:52:18.958: CBAC SMTP: reply_type OTHERS *Oct 18 21:52:18.958: CBAC SMTP: OTHER REPLY - Reply len: 21, match_len:21, reply_re_state:18 *Oct 18 21:52:18.958: CBAC SMTP: OTHER REPLY match id:13 *Oct 18 21:52:18.958: CBAC SMTP: OTHER REPLY match id:10 *Oct 18 21:52:18.958: CBAC SMTP: End Of Reply Line - index:14 ,len:21
Atualmente, não existem informações disponíveis específicas sobre Troubleshooting para esta configuração.