6 Conexión segura a la interfaz web

Descripción general

Esta sección proporciona los pasos de configuración de Zabbix y ejemplos de configuración para conexiones TLS seguras entre el frontend de Zabbix y el servidor de Zabbix.

Configuración

De forma predeterminada, la comunicación entre Zabbix frontend y Zabbix server no está cifrada. Para una mejor seguridad, habilite TLS en ambos lados. A continuación se muestra un ejemplo de la forma más sencilla de hacerlo.

1. Genere certificados y claves.

Cree un directorio de trabajo:

sudo mkdir -p /etc/zabbix/ssl && cd /etc/zabbix/ssl

Cree un certificado CA (ajuste el valor MyZabbixCA para que coincida con el nombre común real):

sudo openssl genrsa -out ca.key 4096
sudo openssl req -new -x509 -days 3650 -key ca.key -out ca.crt -subj "/CN=MyZabbixCA/"

Genere una clave privada y un certificado para Zabbix server (ajuste el valor zabbix-server.example.com para que coincida con el nombre común real):

sudo openssl genrsa -out server.key 2048
sudo openssl req -new -key server.key -out server.csr -subj "/CN=zabbix-server.example.com/"
sudo openssl x509 -req -days 365 -in server.csr -CA ca.crt -CAkey ca.key -CAcreateserial -sha256 -out server.crt

Genere una clave privada y un certificado para Zabbix frontend (ajuste el valor zabbix-frontend-node para que coincida con el nombre común real):

sudo openssl genrsa -out frontend.key 2048
sudo openssl req -new -key frontend.key -out frontend.csr -subj "/CN=zabbix-frontend-node/"
sudo openssl x509 -req -days 365 -in frontend.csr -CA ca.crt -CAkey ca.key -CAcreateserial -sha256 -out frontend.crt

2. Establezca los permisos adecuados.

Para Zabbix server (ajuste el propietario/grupo según el usuario del daemon de Zabbix server de su distribución):

sudo chown root:zabbix /etc/zabbix/ssl/server.{crt,key} /etc/zabbix/ssl/ca.crt
sudo chmod 640 /etc/zabbix/ssl/server.key
sudo chmod 644 /etc/zabbix/ssl/server.crt /etc/zabbix/ssl/ca.crt

Para frontend (ajuste el propietario/grupo según el usuario del servidor web de su distribución):

sudo chown root:www-data /etc/zabbix/ssl/frontend.{crt,key}
sudo chmod 640 /etc/zabbix/ssl/frontend.key
sudo chmod 644 /etc/zabbix/ssl/frontend.crt

3. Configure Zabbix server.

En zabbix_server.conf añada:

TLSFrontendAccept=cert
TLSCertFile=/etc/zabbix/ssl/server.crt
TLSKeyFile=/etc/zabbix/ssl/server.key
TLSCAFile=/etc/zabbix/ssl/ca.crt
# Opcionalmente:
# TLSFrontendCertIssuer=CN=MyZabbixCA
# TLSFrontendCertSubject=CN=zabbix-frontend-node

Luego reinicie el server:

sudo systemctl restart zabbix-server

4. Configure Zabbix frontend.

Durante la instalación de la interfaz web, habilite la opción Encrypt connections from Web interface (y la opción Verify server certificate issuer and subject, si es necesario) y complete los campos TLS CA file, TLS key file, TLS certificate file (y los campos Server TLS certificate issuer y Server TLS certificate subject, si es necesario):

En instalaciones existentes, edite los siguientes campos en zabbix.conf.php:

$ZBX_SERVER_TLS['ACTIVE'] = '1';
$ZBX_SERVER_TLS['CA_FILE'] = '/etc/zabbix/ssl/ca.crt';
$ZBX_SERVER_TLS['KEY_FILE'] = '/etc/zabbix/ssl/frontend.key';
$ZBX_SERVER_TLS['CERT_FILE'] = '/etc/zabbix/ssl/frontend.crt';
// Opcionalmente:
// $ZBX_SERVER_TLS['CERTIFICATE_ISSUER']  = 'CN=MyZabbixCA';
// $ZBX_SERVER_TLS['CERTIFICATE_SUBJECT'] = 'CN=zabbix-server.example.com';

5. Verifique el cifrado confirmando que no haya mensajes de error en el frontend de Zabbix ni en el archivo de registro de Zabbix server:

tail -f /var/log/zabbix/zabbix_server.log

Troubleshooting

Incorrect or incomplete TLS configuration can cause errors in the Zabbix frontend or indicate that the Zabbix server is running but the connection is not established successfully:

To identify the exact configuration issue, set the Zabbix server log level to 4, reproduce the error in the frontend, and check the Zabbix server log for the corresponding error message.

The following cases describe common errors and their possible causes.

Frontend IP address is not allowed

The Zabbix server log contains an error similar to:

54283:20260819:105926.400 frontend connection from "127.0.0.1" is not allowed by FrontendAllowedIP

The connection is dropped after the TCP handshake because the frontend IP address is not authorized.

Add the frontend IP address to the FrontendAllowedIP parameter in zabbix_server.conf and restart the Zabbix server.

Unencrypted connection is not allowed

The Zabbix server log contains an error similar to:

56884:20260819:111154.285 frontend connection of type "unencrypted" is not allowed by TLSFrontendAccept

The Zabbix server is configured to accept only TLS connections, for example with TLSFrontendAccept=cert, but the frontend is attempting to connect without encryption.

Enable frontend encryption and configure the required TLS files in zabbix.conf.php, as described in step 4 of the Configuration.

Frontend attempts TLS while server expects unencrypted

The Zabbix server log contains an error similar to:

61091:20260819:115916.019 End of zbx_tls_accept():FAIL error:'TLS handshake set result code to 1: file ../ssl/record/rec_layer_s3.c line 317 func ssl3_read_n: error:0A000126:SSL routines::unexpected eof while reading: TLS write fatal alert "decode error"'

The exact error message depends on the OpenSSL version.

The Zabbix server is configured to accept only unencrypted connections, for example with TLSFrontendAccept=unencrypted, while the frontend is attempting to establish a TLS connection.

Configure the Zabbix server to accept TLS connections by setting TLSFrontendAccept=cert and defining TLSCertFile and TLSKeyFile in zabbix_server.conf. Alternatively, disable frontend encryption in zabbix.conf.php.

Frontend certificate is not trusted

The Zabbix server log contains an error similar to:

62248:20260819:124203.812 End of zbx_tls_accept():FAIL error:'self-signed certificate: TLS handshake set result code to 1: file ../ssl/statem/statem_srvr.c line 3522 func tls_process_client_certificate: error:0A000086:SSL routines::certificate verify failed: TLS write fatal alert "unknown CA"'

The frontend presented a certificate, but the Zabbix server does not trust the Certificate Authority (CA) that signed it.

The same problem can also appear in the frontend system information as:

fread(): SSL operation failed with code 1. OpenSSL Error messages:

error:0A000418:SSL routines::tlsv1 alert unknown ca [zabbix.php:17 → require_once() → ZBase->run() → ZBase->processRequest() → CController->run() → Widgets\SystemInfo\Actions\WidgetView->doAction() → CSystemInfoHelper::getData() → CSystemInfoHelper::getServerStatus() → CZabbixServer->getStatus() → CZabbixServer->request() → fread() → CConfigFile->{closure:/user/share/conf/zabbix.conf.php:89}() in conf/zabbix.conf.php:95]

The frontend may also display "Incorrect response received from Zabbix server "localhost"".

Verify that the frontend certificate is signed by the CA specified by TLSCAFile in zabbix_server.conf.

TLS key file is not readable

The frontend may display "TLS key file: file is not readable."

It may also display "Unable to connect to the Zabbix server due to TLS settings. Some functions are unavailable.".

The web server user does not have sufficient permissions to read one or more certificate, key, or CA files configured in zabbix.conf.php. This can occur when certificate files are stored in a restricted directory, such as /root/ or a user's home directory.

Move the certificate files to a directory accessible to the web server and set appropriate permissions as described in step 2 of the Configuration.

TLS files are invalid or corrupted

The frontend may display "Unable to connect to the Zabbix server due to TLS settings. Some functions are unavailable.".

This can occur when the configured certificate or key files exist and are readable, but their contents are empty, corrupted, or otherwise invalid. In this case, the frontend does not establish a connection to the Zabbix server, and no corresponding connection attempt appears in the Zabbix server log.

Verify that the certificate and key files contain valid, properly formatted data and that the private key corresponds to the certificate.