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Este documento descreve a configuração do Secure Shell (SSH) em dispositivos Cisco IOS® XE usando certificados X.509v3 para autenticação, de acordo com as diretrizes definidas no RFC 6187.
A Cisco recomenda que você tenha conhecimento da infraestrutura de Public Key Infrastructure (PKI).
As informações neste documento são baseadas nestas versões de software e hardware:
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 rede estiver ativa, certifique-se de que você entenda o impacto potencial de qualquer comando
A abordagem melhora a segurança SSH ao habilitar a autenticação baseada em certificado, alinhando, assim, as práticas de gerenciamento de chave SSH com as usadas no Transport Layer Security (TLS).
O SSH fornece autenticação mútua para estabelecer uma conexão segura entre cliente e servidor. Tradicionalmente, os servidores são autenticados usando pares de chaves RSA (Rivest-Shamir-Addleman). O cliente computa uma impressão digital da chave pública do servidor e solicita que o administrador a verifique, de preferência comparando-a com um valor conhecido obtido por meio de um método seguro e fora da banda. No entanto, essa verificação manual é frequentemente ignorada devido à sua complexidade, aumentando o risco de ataques man-in-the-middle (MitM) e enfraquecendo o modelo de confiança SSH.
O RFC 6187 aborda esses problemas habilitando a autenticação baseada em certificado X.509v3, que integra SSH com PKI. Essa abordagem melhora a segurança e a escalabilidade, permitindo que a confiança seja estabelecida por meio de Autoridades de Certificação (CAs) confiáveis, oferecendo uma experiência de usuário e um modelo de confiança semelhante ao TLS.
Configure um ponto confiável que contenha o certificado CA e, opcionalmente, o certificado do roteador.
crypto pki trustpoint pki-server
enrollment pkcs12
subject-name cn=RTR-DC01.cisco.com
revocation-check none
rsakeypair ssh-cert
! The username has to be fetched from the certificate for accounting and authorization purposes. Multiple options are available.
authorization username subjectname commonname
Configure os mecanismos de autenticação permitidos usados durante a negociação do túnel SSH.
! Alorithms used to authenticate server
ip ssh server algorithm hostkey x509v3-ssh-rsa ssh-rsa
! Acceptable algorithms used to authenticate the client
ip ssh server algorithm authentication publickey password keyboard
! Acceptable pubkey-based algorithms used to authenticate the client
ip ssh server algorithm publickey x509v3-ssh-rsa ssh-rsa
Configure o servidor SSH para usar certificados corretos no processo de autenticação.
ip ssh server certificate profile
server
trustpoint sign
user
trustpoint verify
Note: Certifique-se de que o servidor SSH e o cliente SSH tenham o certificado de ID emitido pelo mesmo servidor CA.
Note: Se, no caso de o cliente SSH, como a máquina Windows, tiver um certificado de ID emitido por alguma outra CA, faça com que ele seja importado no servidor SSH, ou seja, o Switch Cisco e mapeie esse ponto confiável para o perfil de certificado do servidor SSH acima na seção do usuário.
show ip ssh
SSH Enabled - version 1.99
Authentication methods:publickey,password,keyboard-interactive
Authentication Publickey Algorithms:x509v3-ssh-rsa,ssh-rsa
Hostkey Algorithms:x509v3-ssh-rsa,ssh-rsa
--- output truncated ----
show users
Line User Host(s) Idle Location
1 vty 0 sameer.cisco.com idle 00:02:37 192.168.1.100
Essas depurações são usadas para rastrear sessões bem-sucedidas:
debug ip ssh detail
debug crypto pki transactions
debug crypto pki messages
debug crypto pki validation
Mar 27 15:35:40.103: SSH1: starting SSH control process
! Server identifies itself
Mar 27 15:35:40.103: SSH1: sent protocol version id SSH-1.99-Cisco-1.25
! Client identifies itself
Mar 27 15:35:40.106: SSH1: protocol version id is - SSH-2.0-Pragma FortressCL 5.0.10.4176
! Authentication algorithms supported by server
Mar 27 15:35:40.106: SSH2 1: kexinit sent: kex algo = diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1
Mar 27 15:35:40.106: SSH2 1: kexinit sent: hostkey algo = x509v3-ssh-rsa,ssh-rsa
Mar 27 15:35:40.106: SSH2 1: kexinit sent: encryption algo = aes128-ctr,aes192-ctr,aes256-ctr
Mar 27 15:35:40.106: SSH2 1: kexinit sent: mac algo = hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha1-96
Mar 27 15:35:40.106: SSH2 1: SSH2_MSG_KEXINIT sent
Mar 27 15:35:40.109: SSH2 1: SSH2_MSG_KEXINIT received
Mar 27 15:35:40.109: SSH2 1: kex: client->server enc:aes256-ctr mac:hmac-sha2-256
Mar 27 15:35:40.109: SSH2 1: kex: server->client enc:aes256-ctr mac:hmac-sha2-256
! Client chooses authentication algorithm
Mar 27 15:35:40.109: SSH2 1: Using hostkey algo = x509v3-ssh-rsa
Mar 27 15:35:40.109: SSH2 1: Using kex_algo = diffie-hellman-group-exchange-sha1
Mar 27 15:35:40.109: SSH2 1: SSH2_MSG_KEX_DH_GEX_REQUEST received
Mar 27 15:35:40.109: SSH2 1: Range sent by client is - 1024 < 2048 < 8192
Mar 27 15:35:40.109: SSH2 1: Modulus size established : 2048 bits
Mar 27 15:35:40.121: SSH2 1: expecting SSH2_MSG_KEX_DH_GEX_INIT
Mar 27 15:35:40.121: SSH2 1: SSH2_MSG_KEXDH_INIT received
! SSH Server sends certificate associated with trustpoint "pki-server"
Mar 27 15:35:40.133: SSH2 1: Sending Server certificate associated with PKI trustpoint "pki-server"
Mar 27 15:35:40.133: SSH2 1: Got 2 certificate(s) on certificate chain
Mar 27 15:35:40.135: SSH2: kex_derive_keys complete
Mar 27 15:35:40.135: SSH2 1: SSH2_MSG_NEWKEYS sent
Mar 27 15:35:40.135: SSH2 1: waiting for SSH2_MSG_NEWKEYS
Mar 27 15:35:40.214: SSH2 0: channel window adjust message received 49926
Mar 27 15:35:41.417: SSH2 1: SSH2_MSG_NEWKEYS received
Mar 27 15:35:41.436: SSH2 1: Authentications that can continue = publickey,password,keyboard-interactive
Mar 27 15:35:41.437: SSH2 1: Using method = none
Mar 27 15:35:41.437: SSH2 1: Authentications that can continue = publickey,password,keyboard-interactive
Mar 27 15:35:41.438: SSH2 1: Using method = publickey
! Client sends certificate
Mar 27 15:35:41.438: SSH2 1: Received publickey algo = x509v3-ssh-rsa
Mar 27 15:35:41.438: SSH2 1: Verifying certificate for user 'sameer.cisco.com' in SSH2_MSG_USERAUTH_REQUEST
Mar 27 15:35:41.439: SSH2 1: Verifying certificate for user 'sameer.cisco.com'
Mar 27 15:35:41.439: SSH2 1: Received a chain of 2 certificate
Mar 27 15:35:41.439: SSH2 1: Received 0 ocsp-response
Mar 27 15:35:41.439: SSH2 1: Starting PKI session for certificate verification
! Client certificate is verified by the SSH-Server
Mar 27 15:35:41.444: SSH2 1: Verifying certificate for user 'sameer.cisco.com'
Mar 27 15:35:41.444: SSH2 1: Received a chain of 2 certificate
Mar 27 15:35:41.444: SSH2 1: Received 0 ocsp-response
Mar 27 15:35:41.444: SSH2 1: Starting PKI session for certificate verification
Mar 27 15:35:41.445: SSH2 1: Verifying signature for user 'sameer.cisco.com' in SSH2_MSG_USERAUTH_REQUEST
Mar 27 15:35:41.445: SSH2 1: Received a chain of 2 certificate
Mar 27 15:35:41.445: SSH2 1: Received 0 ocsp-response
! Certificate status verified successfully
Mar 27 15:35:41.446: SSH2 1: Client Signature verification PASSED
Mar 27 15:35:41.446: SSH2 1: Certificate authentication passed for user 'sameer.cisco.com'
Mar 27 15:35:41.446: SSH2 1: authentication successful for sameer.cisco.com
Mar 27 15:35:41.448: SSH2 1: channel open request
Mar 27 15:35:41.451: SSH2 1: pty-req request
Mar 27 15:35:41.451: SSH2 1: setting TTY - requested: height 25, width 80; set: height 25, width 80
Mar 27 15:35:41.452: SSH2 1: shell request
Mar 27 15:35:41.452: SSH2 1: shell message received
Mar 27 15:35:41.452: SSH2 1: starting shell for vty
Mar 27 15:35:41.464: SSH2 1: channel window adjust message received 9
Aug 21 20:07:32.311: CRYPTO_PKI: ip-ext-val: IP extension validation not required
A validação do certificado é bem-sucedida para o usuário, no entanto, devido à ausência do comando obrigatório authorization username subjectname commonname na configuração, a Autenticação do Certificado para o usuário falha.
Apr 26 01:35:32.222: SSH1: starting SSH control process
Apr 26 01:35:32.222: SSH1: sent protocol version id SSH-1.99-Cisco-1.25
Apr 26 01:35:32.224: SSH1: protocol version id is - SSH-2.0-Pragma FortressCL 5.0.10.4176
Apr 26 01:35:32.224: SSH2 1: kexinit sent: kex algo = diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1
Apr 26 01:35:32.224: SSH2 1: kexinit sent: hostkey algo = x509v3-ssh-rsa,ssh-rsa
Apr 26 01:35:32.224: SSH2 1: kexinit sent: encryption algo = aes128-ctr,aes192-ctr,aes256-ctr
Apr 26 01:35:32.224: SSH2 1: kexinit sent: mac algo = hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha1-96
Apr 26 01:35:32.224: SSH2 1: SSH2_MSG_KEXINIT sent
Apr 26 01:35:32.234: SSH2 1: SSH2_MSG_KEXINIT received
Apr 26 01:35:32.234: SSH2 1: kex: client->server enc:aes256-ctr mac:hmac-sha2-256
Apr 26 01:35:32.235: SSH2 1: kex: server->client enc:aes256-ctr mac:hmac-sha2-256
Apr 26 01:35:32.235: SSH2 1: Using hostkey algo = x509v3-ssh-rsa
Apr 26 01:35:32.235: SSH2 1: Using kex_algo = diffie-hellman-group-exchange-sha1
Apr 26 01:35:32.235: SSH2 1: SSH2_MSG_KEX_DH_GEX_REQUEST received
Apr 26 01:35:32.235: SSH2 1: Range sent by client is - 1024 < 2048 < 8192
Apr 26 01:35:32.235: SSH2 1: Modulus size established : 2048 bits
Apr 26 01:35:32.246: SSH2 1: expecting SSH2_MSG_KEX_DH_GEX_INIT
Apr 26 01:35:32.246: SSH2 1: SSH2_MSG_KEXDH_INIT received
Apr 26 01:35:32.259: SSH2 1: Sending Server certificate associated with PKI trustpoint “pki-server”
Apr 26 01:35:32.259: CRYPTO_PKI: (A0049) Session started - identity selected (pki-server)
Apr 26 01:35:32.259: SSH2 1: Got 3 certificate(s) on certificate chain
Apr 26 01:35:32.259: CRYPTO_PKI: Rcvd request to end PKI session A0049.
Apr 26 01:35:32.260: CRYPTO_PKI: PKI session A0049 has ended. Freeing all resources.
Apr 26 01:35:32.260: CRYPTO_PKI: unlocked trustpoint pki-server, refcount is 0
Apr 26 01:35:32.273: SSH2: kex_derive_keys complete
Apr 26 01:35:32.274: SSH2 1: SSH2_MSG_NEWKEYS sent
Apr 26 01:35:32.274: SSH2 1: waiting for SSH2_MSG_NEWKEYS
Apr 26 01:35:45.664: SSH2 1: SSH2_MSG_NEWKEYS received
Apr 26 01:35:45.665: SSH2 1: Authentications that can continue = publickey,password,keyboard-interactive
Apr 26 01:35:45.666: SSH2 1: Using method = none
Apr 26 01:35:45.666: SSH2 1: Authentications that can continue = publickey,password,keyboard-interactive
Apr 26 01:35:45.675: SSH2 1: Using method = publickey
Apr 26 01:35:45.675: SSH2 1: Received publickey algo = x509v3-ssh-rsa
Apr 26 01:35:45.676: SSH2 1: Verifying certificate for user 'sameer.cisco.com' in SSH2_MSG_USERAUTH_REQUEST
Apr 26 01:35:45.676: SSH2 1: Verifying certificate for user 'sameer.cisco.com'
Apr 26 01:35:45.676: SSH2 1: Received a chain of 3 certificate
Apr 26 01:35:45.676: SSH2 1: Received 0 ocsp-response
Apr 26 01:35:45.676: SSH2 1: Starting PKI session for certificate verification
Apr 26 01:35:45.676: CRYPTO_PKI: (A004A) Session started - identity not specified
Apr 26 01:35:45.676: CRYPTO_PKI: (A004A) Adding peer certificate
Apr 26 01:35:45.676: CRYPTO_PKI: Added x509 peer certificate - (1249) bytes
Apr 26 01:35:45.676: CRYPTO_PKI: (A004A) Adding peer certificate
Apr 26 01:35:45.676: CRYPTO_PKI: Added x509 peer certificate - (1215) bytes
Apr 26 01:35:45.676: CRYPTO_PKI: (A004A) Adding peer certificate
Apr 26 01:35:45.676: CRYPTO_PKI: Added x509 peer certificate - (921) bytes
Apr 26 01:35:45.676: CRYPTO_PKI: ip-ext-val: IP extension validation not required
Apr 26 01:35:45.677: CRYPTO_PKI: create new ca_req_context type PKI_VERIFY_CHAIN_CONTEXT,ident 37
Apr 26 01:35:45.677: CRYPTO_PKI: (A004A)validation path has 1 certs
Apr 26 01:35:45.677: CRYPTO_PKI: (A004A) Check for identical certs
Apr 26 01:35:45.677: CRYPTO_PKI : (A004A) Validating non-trusted cert
Apr 26 01:35:45.677: CRYPTO_PKI: (A004A) Create a list of suitable trustpoints
Apr 26 01:35:45.677: CRYPTO_PKI: Found a issuer match
Apr 26 01:35:45.677: CRYPTO_PKI: (A004A) Suitable trustpoints are: pki-server,
Apr 26 01:35:45.677: CRYPTO_PKI: (A004A) Attempting to validate certificate using pki-server policy
Apr 26 01:35:45.677: CRYPTO_PKI: EKU validation successful. Cert matches configuration.
Apr 26 01:35:45.677: CRYPTO_PKI: (A004A) Using pki-server to validate certificate
Apr 26 01:35:45.677: CRYPTO_PKI: Added 1 certs to trusted chain.
Apr 26 01:35:45.677: CRYPTO_PKI: Prepare session revocation service providers
Apr 26 01:35:45.677: CRYPTO_PKI: Deleting cached key having key id 50
Apr 26 01:35:45.677: CRYPTO_PKI: Attempting to insert the peer's public key into cache
Apr 26 01:35:45.677: CRYPTO_PKI:Peer's public inserted successfully with key id 51
Apr 26 01:35:45.678: CRYPTO_PKI: Expiring peer's cached key with key id 51
Apr 26 01:35:45.678: CRYPTO_PKI: (A004A) Certificate is verified
Apr 26 01:35:45.678: CRYPTO_PKI: Remove session revocation service providers
Apr 26 01:35:45.678: CRYPTO_PKI: Remove session revocation service providers
Apr 26 01:35:45.678: CRYPTO_PKI: (A004A) Certificate validated without revocation check
Apr 26 01:35:45.678: CRYPTO_PKI: Populate AAA auth data
Apr 26 01:35:45.678: CRYPTO_PKI: Unable to get configured attribute for primary AAA list authorization.
Apr 26 01:35:45.678: CRYPTO_PKI: (A004A)chain cert was anchored to trustpoint pki-server, and chain validation result was: CRYPTO_VALID_CERT_WITH_WARNING
Apr 26 01:35:45.678: CRYPTO_PKI: destroying ca_req_context type PKI_VERIFY_CHAIN_CONTEXT,ident 37, ref count 1
Apr 26 01:35:45.678: CRYPTO_PKI: ca_req_context released
Apr 26 01:35:45.678: CRYPTO_PKI: (A004A) Validation TP is pki-server
Apr 26 01:35:45.678: CRYPTO_PKI: (A004A) Certificate validation succeeded
Apr 26 01:35:45.678: SSH2 1: Could not find username field configured for certificate in trustpoint Err code = 7
Apr 26 01:35:45.678: CRYPTO_PKI: Rcvd request to end PKI session A004A.
Apr 26 01:35:45.678: CRYPTO_PKI: PKI session A004A has ended. Freeing all resources.
Apr 26 01:35:45.679: SSH2 1: Can not decode the certificate Err code = 7
Apr 26 01:35:45.679: SSH2 1: Certificate authentication failed for user 'sameer.cisco.com'
Revisão | Data de publicação | Comentários |
---|---|---|
1.0 |
25-Jul-2025 |
Versão inicial |