Zabbix 7.2
OS Oracle Linux 9.6
I have a legacy switch that is monitored by a Zabbix Proxy and has SSH items configured. However, the SSH items are unable to reach the host due to a mismatch in Kex algorithms.
Here's the error message that Zabbix displays:
Cannot establish SSH session: kex error : no match for method kex algos: server [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1], client [curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512] I'm unable to connect to the switch from the Proxy terminal either, with basically the same error message.
So, I've added the following configuration to the proxy /etc/ssh/ssh_config file.
Host 10.22.200.89 KexAlgorithms ^diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 MACs ^hmac-sha1,hmac-sha1-96 Also, the /etc/ssl/openssl.cnf file is configured to allow legacy algorithms.
[ evp_properties ] rh-allow-sha1-signatures = yes [provider_sect] default = default_sect legacy = legacy_sect [legacy_sect] activate = 1 After making this configuration change, I can SSH to the host from the Proxy CLI with my own user.
However, the error remains the same when connecting from Zabbix itself. 
When I try to manually SSH to the switch via the Zabbix Proxy terminal with the zabbix user, the host key also fails.
# su - zabbix -c "ssh -vvv [email protected]" OpenSSH_8.7p1, OpenSSL 3.2.2 4 Jun 2024 debug1: Reading configuration data /etc/ssh/ssh_config debug3: kex names ok: [diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1] debug1: /etc/ssh/ssh_config line 13: Applying options for * debug2: resolve_canonicalize: hostname 10.22.200.89 is address debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/var/lib/zabbix/.ssh/known_hosts' debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/var/lib/zabbix/.ssh/known_hosts2' debug3: ssh_connect_direct: entering debug1: Connecting to 10.22.200.89 [10.22.200.89] port 22. debug3: set_sock_tos: set socket 5 IP_TOS 0x48 debug1: Connection established. debug1: identity file /var/lib/zabbix/.ssh/id_rsa type -1 debug1: identity file /var/lib/zabbix/.ssh/id_rsa-cert type -1 debug1: identity file /var/lib/zabbix/.ssh/id_dsa type -1 debug1: identity file /var/lib/zabbix/.ssh/id_dsa-cert type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ecdsa type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ecdsa-cert type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ecdsa_sk type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ecdsa_sk-cert type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ed25519 type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ed25519-cert type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ed25519_sk type -1 debug1: identity file /var/lib/zabbix/.ssh/id_ed25519_sk-cert type -1 debug1: identity file /var/lib/zabbix/.ssh/id_xmss type -1 debug1: identity file /var/lib/zabbix/.ssh/id_xmss-cert type -1 debug1: Local version string SSH-2.0-OpenSSH_8.7 debug1: Remote protocol version 1.99, remote software version Cisco-1.25 debug1: compat_banner: match: Cisco-1.25 pat Cisco-1.* compat 0x60000000 debug2: fd 5 setting O_NONBLOCK debug1: Authenticating to 10.22.200.89:22 as 'switchuser' debug1: load_hostkeys: fopen /var/lib/zabbix/.ssh/known_hosts: No such file or directory debug1: load_hostkeys: fopen /var/lib/zabbix/.ssh/known_hosts2: No such file or directory debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory debug3: order_hostkeyalgs: no algorithms matched; accept original debug3: send packet: type 20 debug1: SSH2_MSG_KEXINIT sent debug3: receive packet: type 20 debug1: SSH2_MSG_KEXINIT received debug2: local client KEXINIT proposal debug2: KEX algorithms: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1,curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c,[email protected] debug2: host key algorithms: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],rsa-sha2-512,rsa-sha2-256,ssh-rsa debug2: ciphers ctos: aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected] debug2: ciphers stoc: aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected] debug2: MACs ctos: [email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha1-96 debug2: MACs stoc: [email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1,hmac-sha1-96 debug2: compression ctos: none,[email protected],zlib debug2: compression stoc: none,[email protected],zlib debug2: languages ctos: debug2: languages stoc: debug2: first_kex_follows 0 debug2: reserved 0 debug2: peer server KEXINIT proposal debug2: KEX algorithms: diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 debug2: host key algorithms: ssh-rsa debug2: ciphers ctos: aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc debug2: ciphers stoc: aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc debug2: MACs ctos: hmac-sha1,hmac-sha1-96 debug2: MACs stoc: hmac-sha1,hmac-sha1-96 debug2: compression ctos: none debug2: compression stoc: none debug2: languages ctos: debug2: languages stoc: debug2: first_kex_follows 0 debug2: reserved 0 debug1: kex: algorithm: diffie-hellman-group-exchange-sha1 debug1: kex: host key algorithm: ssh-rsa debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha1 compression: none debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha1 compression: none debug1: kex: diffie-hellman-group-exchange-sha1 need=20 dh_need=20 debug1: kex: diffie-hellman-group-exchange-sha1 need=20 dh_need=20 debug3: send packet: type 34 debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(2048<4096<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug3: receive packet: type 31 debug1: SSH2_MSG_KEX_DH_GEX_GROUP received debug3: send packet: type 32 debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug3: receive packet: type 33 debug1: SSH2_MSG_KEX_DH_GEX_REPLY received debug1: Server host key: ssh-rsa SHA256:ycZPa..[redacted] debug1: load_hostkeys: fopen /var/lib/zabbix/.ssh/known_hosts: No such file or directory debug1: load_hostkeys: fopen /var/lib/zabbix/.ssh/known_hosts2: No such file or directory debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory debug3: hostkeys_find_by_key_hostfile: trying user hostfile "/var/lib/zabbix/.ssh/known_hosts" debug1: hostkeys_find_by_key_hostfile: hostkeys file /var/lib/zabbix/.ssh/known_hosts does not exist debug3: hostkeys_find_by_key_hostfile: trying user hostfile "/var/lib/zabbix/.ssh/known_hosts2" debug1: hostkeys_find_by_key_hostfile: hostkeys file /var/lib/zabbix/.ssh/known_hosts2 does not exist debug3: hostkeys_find_by_key_hostfile: trying system hostfile "/etc/ssh/ssh_known_hosts" debug1: hostkeys_find_by_key_hostfile: hostkeys file /etc/ssh/ssh_known_hosts does not exist debug3: hostkeys_find_by_key_hostfile: trying system hostfile "/etc/ssh/ssh_known_hosts2" debug1: hostkeys_find_by_key_hostfile: hostkeys file /etc/ssh/ssh_known_hosts2 does not exist debug1: read_passphrase: can't open /dev/tty: No such device or address Host key verification failed. As I understand it, the Proxy should handle the SSH connection to the monitored host. It seems that no matter what SSH configuration I try, it does not affect the Zabbix connection. So, I'm not sure what the issue is.
Has anyone encountered this issue before?
