In some cases it might be needed to reject SSL handshake based on SNI
server name provided, for example, to make sure an invalid certificate
is not returned to clients trying to contact a name-based virtual server
without SSL configured. Previously, a "ssl_ciphers aNULL;" was used for
this. This workaround, however, is not compatible with TLSv1.3, in
particular, when using BoringSSL, where it is not possible to configure
TLSv1.3 ciphers at all.
With this change, the ssl_reject_handshake directive is introduced,
which instructs nginx to reject SSL handshakes with an "unrecognized_name"
alert in a particular server block.
For example, to reject handshake with names other than example.com,
one can use the following configuration:
server {
listen 443 ssl;
ssl_reject_handshake on;
}
server {
listen 443 ssl;
server_name example.com;
ssl_certificate example.com.crt;
ssl_certificate_key example.com.key;
}
The following configuration can be used to reject all SSL handshakes
without SNI server name provided:
server {
listen 443 ssl;
ssl_reject_handshake on;
}
server {
listen 443 ssl;
server_name ~^;
ssl_certificate example.crt;
ssl_certificate_key example.key;
}
Additionally, the ssl_reject_handshake directive makes configuring
certificates for the default server block optional. If no certificates
are configured in the default server for a given listening socket,
certificates must be defined in all non-default server blocks with
the listening socket in question.
With the ssl_conf_command directive it is now possible to set
arbitrary OpenSSL configuration parameters as long as nginx is compiled
with OpenSSL 1.0.2 or later. Full list of available configuration
commands can be found in the SSL_CONF_cmd manual page
(https://www.openssl.org/docs/man1.1.1/man3/SSL_CONF_cmd.html).
In particular, this allows configuring PrioritizeChaCha option
(ticket #1445):
ssl_conf_command Options PrioritizeChaCha;
It can be also used to configure TLSv1.3 ciphers in OpenSSL,
which fails to configure them via the SSL_CTX_set_cipher_list()
interface (ticket #1529):
ssl_conf_command Ciphersuites TLS_CHACHA20_POLY1305_SHA256;
Configuration commands are applied after nginx own configuration
for SSL, so they can be used to override anything set by nginx.
Note though that configuring OpenSSL directly with ssl_conf_command
might result in a behaviour nginx does not expect, and should be
done with care.
When enabled, certificate status is stored in cache and is used to validate
the certificate in future requests.
New directive ssl_ocsp_cache is added to configure the cache.
OCSP validation for client certificates is enabled by the "ssl_ocsp" directive.
OCSP responder can be optionally specified by "ssl_ocsp_responder".
When session is reused, peer chain is not available for validation.
If the verified chain contains certificates from the peer chain not available
at the server, validation will fail.
If ngx_pool_cleanup_add() fails, we have to clean just created SSL context
manually, thus appropriate call added.
Additionally, ngx_pool_cleanup_add() moved closer to ngx_ssl_create() in
the ngx_http_ssl_module, to make sure there are no leaks due to intermediate
code.
A virtual server may have no SSL context if it does not have certificates
defined, so we have to use config of the ngx_http_ssl_module from the
SSL context in the certificate callback. To do so, it is now passed as
the argument of the callback.
The stream module doesn't really need any changes, but was modified as
well to match http code.
Dynamic certificates re-introduce problem with incorrect session
reuse (AKA "virtual host confusion", CVE-2014-3616), since there are
no server certificates to generate session id context from.
To prevent this, session id context is now generated from ssl_certificate
directives as specified in the configuration. This approach prevents
incorrect session reuse in most cases, while still allowing sharing
sessions across multiple machines with ssl_session_ticket_key set as
long as configurations are identical.
Passwords have to be copied to the configuration pool to be used
at runtime. Also, to prevent blocking on stdin (with "daemon off;")
an empty password list is provided.
To make things simpler, password handling was modified to allow
an empty array (with 0 elements and elts set to NULL) as an equivalent
of an array with 1 empty password.
To evaluate variables, a request is created in the certificate callback,
and then freed. To do this without side effects on the stub_status
counters and connection state, an additional function was introduced,
ngx_http_alloc_request().
Only works with OpenSSL 1.0.2+, since there is no SSL_CTX_set_cert_cb()
in older versions.
Early data AKA 0-RTT mode is enabled as long as "ssl_early_data on" is
specified in the configuration (default is off).
The $ssl_early_data variable evaluates to "1" if the SSL handshake
isn't yet completed, and can be used to set the Early-Data header as
per draft-ietf-httpbis-replay-04.
In mail and stream modules, no certificate provided is a fatal condition,
much like with the "ssl" and "starttls" directives.
In http, "listen ... ssl" can be used in a non-default server without
certificates as long as there is a certificate in the default one, so
missing certificate is only fatal for default servers.
This variable contains URL-encoded client SSL certificate. In contrast
to $ssl_client_cert, it doesn't depend on deprecated header continuation.
The NGX_ESCAPE_URI_COMPONENT variant of encoding is used, so the resulting
variable can be safely used not only in headers, but also as a request
argument.
The $ssl_client_cert variable should be considered deprecated now.
The $ssl_client_raw_cert variable will be eventually renambed back
to $ssl_client_cert.
The variable contains a list of curves as supported by the client.
Known curves are listed by their names, unknown ones are shown
in hex, e.g., "0x001d:prime256v1:secp521r1:secp384r1".
Note that OpenSSL uses session data for SSL_get1_curves(), and
it doesn't store full list of curves supported by the client when
serializing a session. As a result $ssl_curves is only available
for new sessions (and will be empty for reused ones).
The variable is only meaningful when using OpenSSL 1.0.2 and above.
With older versions the variable is empty.
The variable contains list of ciphers as supported by the client.
Known ciphers are listed by their names, unknown ones are shown
in hex, e.g., ""AES128-SHA:AES256-SHA:0x00ff".
The variable is fully supported only when using OpenSSL 1.0.2 and above.
With older version there is an attempt to provide some information
using SSL_get_shared_ciphers(). It only lists known ciphers though.
Moreover, as OpenSSL uses session data for SSL_get_shared_ciphers(),
and it doesn't store relevant data when serializing a session. As
a result $ssl_ciphers is only available for new sessions (and not
available for reused ones) when using OpenSSL older than 1.0.2.
Originally, the variables kept a result of X509_NAME_oneline(),
which is, according to the official documentation, a legacy
function. It produces a non standard output form and has
various quirks and inconsistencies.
The RFC2253 compliant behavior is introduced for these variables.
The original variables are available through $ssl_client_s_dn_legacy
and $ssl_client_i_dn_legacy.
This patch moves various OpenSSL-specific function calls into the
OpenSSL module and introduces ngx_ssl_ciphers() to make nginx more
crypto-library-agnostic.
OpenSSL 1.0.2+ allows configuring a curve list instead of a single curve
previously supported. This allows use of different curves depending on
what client supports (as available via the elliptic_curves extension),
and also allows use of different curves in an ECDHE key exchange and
in the ECDSA certificate.
The special value "auto" was introduced (now the default for ssl_ecdh_curve),
which means "use an internal list of curves as available in the OpenSSL
library used". For versions prior to OpenSSL 1.0.2 it maps to "prime256v1"
as previously used. The default in 1.0.2b+ prefers prime256v1 as well
(and X25519 in OpenSSL 1.1.0+).
As client vs. server preference of curves is controlled by the
same option as used for ciphers (SSL_OP_CIPHER_SERVER_PREFERENCE),
the ssl_prefer_server_ciphers directive now controls both.
LibreSSL removed support for export ciphers and a call to
SSL_CTX_set_tmp_rsa_callback() results in an error left in the error
queue. This caused alerts "ignoring stale global SSL error (...called
a function you should not call) while SSL handshaking" on a first connection
in each worker process.
This adds support so it's possible to explicitly disable SSL Session
Tickets. In order to have good Forward Secrecy support either the
session ticket key has to be reloaded by using nginx' binary upgrade
process or using an external key file and reloading the configuration.
This directive adds another possibility to have good support by
disabling session tickets altogether.
If session tickets are enabled and the process lives for a long a time,
an attacker can grab the session ticket from the process and use that to
decrypt any traffic that occured during the entire lifetime of the
process.
