Module ngx_http_ssl_module

Example Configuration
Directives
     ssl
     ssl_buffer_size
     ssl_certificate
     ssl_certificate_key
     ssl_ciphers
     ssl_client_certificate
     ssl_crl
     ssl_dhparam
     ssl_ecdh_curve
     ssl_password_file
     ssl_prefer_server_ciphers
     ssl_protocols
     ssl_session_cache
     ssl_session_ticket_key
     ssl_session_tickets
     ssl_session_timeout
     ssl_stapling
     ssl_stapling_file
     ssl_stapling_responder
     ssl_stapling_verify
     ssl_trusted_certificate
     ssl_verify_client
     ssl_verify_depth
Error Processing
Embedded Variables

The ngx_http_ssl_module module provides the necessary support for HTTPS.

This module is not built by default, it should be enabled with the --with-http_ssl_module configuration parameter.

This module requires the OpenSSL library.

Example Configuration

To reduce the processor load it is recommended to

worker_processes auto;

http {

    ...

    server {
        listen              443 ssl;
        keepalive_timeout   70;

        ssl_protocols       SSLv3 TLSv1 TLSv1.1 TLSv1.2;
        ssl_ciphers         AES128-SHA:AES256-SHA:RC4-SHA:DES-CBC3-SHA:RC4-MD5;
        ssl_certificate     /usr/local/nginx/conf/cert.pem;
        ssl_certificate_key /usr/local/nginx/conf/cert.key;
        ssl_session_cache   shared:SSL:10m;
        ssl_session_timeout 10m;

        ...
    }

Directives

Syntax: ssl on | off;
Default:
ssl off;
Context: http, server

Enables the HTTPS protocol for the given virtual server.

It is recommended to use the ssl parameter of the listen directive instead of this directive.

Syntax: ssl_buffer_size size;
Default:
ssl_buffer_size 16k;
Context: http, server

This directive appeared in version 1.5.9.

Sets the size of the buffer used for sending data.

By default, the buffer size is 16k, which corresponds to minimal overhead when sending big responses. To minimize Time To First Byte it may be beneficial to use smaller values, for example:

ssl_buffer_size 4k;

Syntax: ssl_certificate file;
Default:
Context: http, server

Specifies a file with the certificate in the PEM format for the given virtual server. If intermediate certificates should be specified in addition to a primary certificate, they should be specified in the same file in the following order: the primary certificate comes first, then the intermediate certificates. A secret key in the PEM format may be placed in the same file.

It should be kept in mind that due to the HTTPS protocol limitations virtual servers should listen on different IP addresses:

server {
    listen          192.168.1.1:443;
    server_name     one.example.com;
    ssl_certificate /usr/local/nginx/conf/one.example.com.cert;
    ...
}

server {
    listen          192.168.1.2:443;
    server_name     two.example.com;
    ssl_certificate /usr/local/nginx/conf/two.example.com.cert;
    ...
}

otherwise the first server’s certificate will be issued for the second site.

Syntax: ssl_certificate_key file;
Default:
Context: http, server

Specifies a file with the secret key in the PEM format for the given virtual server.

Syntax: ssl_ciphers ciphers;
Default:
ssl_ciphers HIGH:!aNULL:!MD5;
Context: http, server

Specifies the enabled ciphers. The ciphers are specified in the format understood by the OpenSSL library, for example:

ssl_ciphers ALL:!aNULL:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP;

The full list can be viewed using the “openssl ciphers” command.

The previous versions of nginx used different ciphers by default.

Syntax: ssl_client_certificate file;
Default:
Context: http, server

Specifies a file with trusted CA certificates in the PEM format used to verify client certificates and OCSP responses if ssl_stapling is enabled.

The list of certificates will be sent to clients. If this is not desired, the ssl_trusted_certificate directive can be used.

Syntax: ssl_crl file;
Default:
Context: http, server

This directive appeared in version 0.8.7.

Specifies a file with revoked certificates (CRL) in the PEM format used to verify client certificates.

Syntax: ssl_dhparam file;
Default:
Context: http, server

This directive appeared in version 0.7.2.

Specifies a file with DH parameters for EDH ciphers.

Syntax: ssl_ecdh_curve curve;
Default:
ssl_ecdh_curve prime256v1;
Context: http, server

This directive appeared in versions 1.1.0 and 1.0.6.

Specifies a curve for ECDHE ciphers.

Syntax: ssl_password_file file;
Default:
Context: http, server

This directive appeared in version 1.7.3.

Specifies a file with passphrases for secret keys where each passphrase is specified on a separate line. Passphrases are tried in turn when loading the key.

Example:

http {
    ssl_password_file /etc/keys/global.pass;
    ...

    server {
        server_name www1.example.com;
        ssl_certificate_key /etc/keys/first.key;
    }

    server {
        server_name www2.example.com;

        # named pipe can also be used instead of a file
        ssl_password_file /etc/keys/fifo;
        ssl_certificate_key /etc/keys/second.key;
    }
}

Syntax: ssl_prefer_server_ciphers on | off;
Default:
ssl_prefer_server_ciphers off;
Context: http, server

Specifies that server ciphers should be preferred over client ciphers when using the SSLv3 and TLS protocols.

Syntax: ssl_protocols [SSLv2] [SSLv3] [TLSv1] [TLSv1.1] [TLSv1.2];
Default:
ssl_protocols SSLv3 TLSv1 TLSv1.1 TLSv1.2;
Context: http, server

Enables the specified protocols. The TLSv1.1 and TLSv1.2 parameters work only when the OpenSSL library of version 1.0.1 or higher is used.

The TLSv1.1 and TLSv1.2 parameters are supported starting from versions 1.1.13 and 1.0.12, so when the OpenSSL version 1.0.1 or higher is used on older nginx versions, these protocols work, but cannot be disabled.

Syntax: ssl_session_cache off | none | [builtin[:size]] [shared:name:size];
Default:
ssl_session_cache none;
Context: http, server

Sets the types and sizes of caches that store session parameters. A cache can be of any of the following types:

off
the use of a session cache is strictly prohibited: nginx explicitly tells a client that sessions may not be reused.
none
the use of a session cache is gently disallowed: nginx tells a client that sessions may be reused, but does not actually store session parameters in the cache.
builtin
a cache built in OpenSSL; used by one worker process only. The cache size is specified in sessions. If size is not given, it is equal to 20480 sessions. Use of the built-in cache can cause memory fragmentation.
shared
a cache shared between all worker processes. The cache size is specified in bytes; one megabyte can store about 4000 sessions. Each shared cache should have an arbitrary name. A cache with the same name can be used in several virtual servers.

Both cache types can be used simultaneously, for example:

ssl_session_cache builtin:1000 shared:SSL:10m;

but using only shared cache without the built-in cache should be more efficient.

Syntax: ssl_session_ticket_key file;
Default:
Context: http, server

This directive appeared in version 1.5.7.

Sets a file with the secret key used to encrypt and decrypt TLS session tickets. The directive is necessary if the same key has to be shared between multiple servers. By default, a randomly generated key is used.

If several keys are specified, only the first key is used to encrypt TLS session tickets. This allows configuring key rotation, for example:

ssl_session_ticket_key current.key;
ssl_session_ticket_key previous.key;

The file must contain 48 bytes of random data and can be created using the following command:

openssl rand 48 > ticket.key

Syntax: ssl_session_tickets on | off;
Default:
ssl_session_tickets on;
Context: http, server

This directive appeared in version 1.5.9.

Enables or disables session resumption through TLS session tickets.

Syntax: ssl_session_timeout time;
Default:
ssl_session_timeout 5m;
Context: http, server

Specifies a time during which a client may reuse the session parameters stored in a cache.

Syntax: ssl_stapling on | off;
Default:
ssl_stapling off;
Context: http, server

This directive appeared in version 1.3.7.

Enables or disables stapling of OCSP responses by the server. Example:

ssl_stapling on;
resolver 192.0.2.1;

For the OCSP stapling to work, the certificate of the server certificate issuer should be known. If the ssl_certificate file does not contain intermediate certificates, the certificate of the server certificate issuer should be present in the ssl_trusted_certificate file.

For a resolution of the OCSP responder hostname, the resolver directive should also be specified.

Syntax: ssl_stapling_file file;
Default:
Context: http, server

This directive appeared in version 1.3.7.

When set, the stapled OCSP response will be taken from the specified file instead of querying the OCSP responder specified in the server certificate.

The file should be in the DER format as produced by the “openssl ocsp” command.

Syntax: ssl_stapling_responder url;
Default:
Context: http, server

This directive appeared in version 1.3.7.

Overrides the URL of the OCSP responder specified in the “Authority Information Access” certificate extension.

Only “http://” OCSP responders are supported:

ssl_stapling_responder http://ocsp.example.com/;

Syntax: ssl_stapling_verify on | off;
Default:
ssl_stapling_verify off;
Context: http, server

This directive appeared in version 1.3.7.

Enables or disables verification of OCSP responses by the server.

For verification to work, the certificate of the server certificate issuer, the root certificate, and all intermediate certificates should be configured as trusted using the ssl_trusted_certificate directive.

Syntax: ssl_trusted_certificate file;
Default:
Context: http, server

This directive appeared in version 1.3.7.

Specifies a file with trusted CA certificates in the PEM format used to verify client certificates and OCSP responses if ssl_stapling is enabled.

In contrast to the certificate set by ssl_client_certificate, the list of these certificates will not be sent to clients.

Syntax: ssl_verify_client on | off | optional | optional_no_ca;
Default:
ssl_verify_client off;
Context: http, server

Enables verification of client certificates. The verification result is stored in the $ssl_client_verify variable.

The optional parameter (0.8.7+) requests the client certificate and verifies it if the certificate is present.

The optional_no_ca parameter (1.3.8, 1.2.5) requests the client certificate but does not require it to be signed by a trusted CA certificate. This is intended for the use in cases when a service that is external to nginx performs the actual certificate verification. The contents of the certificate is accessible through the $ssl_client_cert variable.

Syntax: ssl_verify_depth number;
Default:
ssl_verify_depth 1;
Context: http, server

Sets the verification depth in the client certificates chain.

Error Processing

The ngx_http_ssl_module module supports several non-standard error codes that can be used for redirects using the error_page directive:

495
an error has occurred during the client certificate verification;
496
a client has not presented the required certificate;
497
a regular request has been sent to the HTTPS port.

The redirection happens after the request is fully parsed and the variables, such as $request_uri, $uri, $args and others, are available.

Embedded Variables

The ngx_http_ssl_module module supports several embedded variables:

$ssl_cipher
returns the string of ciphers used for an established SSL connection;
$ssl_client_cert
returns the client certificate in the PEM format for an established SSL connection, with each line except the first prepended with the tab character; this is intended for the use in the proxy_set_header directive;
$ssl_client_fingerprint
returns the SHA1 fingerprint of the client certificate for an established SSL connection (1.7.1);
$ssl_client_raw_cert
returns the client certificate in the PEM format for an established SSL connection;
$ssl_client_serial
returns the serial number of the client certificate for an established SSL connection;
$ssl_client_s_dn
returns the “subject DN” string of the client certificate for an established SSL connection;
$ssl_client_i_dn
returns the “issuer DN” string of the client certificate for an established SSL connection;
$ssl_client_verify
returns the result of client certificate verification: “SUCCESS”, “FAILED”, and “NONE” if a certificate was not present;
$ssl_protocol
returns the protocol of an established SSL connection;
$ssl_server_name
returns the server name requested through SNI (1.7.0);
$ssl_session_id
returns the session identifier of an established SSL connection;
$ssl_session_reused
returns “r” if an SSL session was reused, or “.” otherwise (1.5.11).