Apache HTTP Server Version 2.4
Available Languages: en
Description: | Strong cryptography using the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols |
---|---|
Status: | Extension |
Module Identifier: | ssl_module |
Source File: | mod_ssl.c |
This module provides SSL v2/v3 and TLS v1 support for the Apache HTTP Server.
This module relies on OpenSSL to provide the cryptography engine.
Further details, discussion, and examples are provided in the SSL documentation.
This module can be configured to provide several items of SSL information
as additional environment variables to the SSI and CGI namespace. This
information is not provided by default for performance reasons. (See
SSLOptions
StdEnvVars, below.) The generated variables
are listed in the table below. For backward compatibility the information can
be made available under different names, too. Look in the Compatibility chapter for details on the
compatibility variables.
Variable Name: | Value Type: | Description: |
---|---|---|
HTTPS | flag | HTTPS is being used. |
SSL_PROTOCOL | string | The SSL protocol version (SSLv3, TLSv1, TLSv1.1, TLSv1.2) |
SSL_SESSION_ID | string | The hex-encoded SSL session id |
SSL_SESSION_RESUMED | string | Initial or Resumed SSL Session. Note: multiple requests may be served over the same (Initial or Resumed) SSL session if HTTP KeepAlive is in use |
SSL_SECURE_RENEG | string | true if secure renegotiation is supported, else false |
SSL_CIPHER | string | The cipher specification name |
SSL_CIPHER_EXPORT | string | true if cipher is an export cipher |
SSL_CIPHER_USEKEYSIZE | number | Number of cipher bits (actually used) |
SSL_CIPHER_ALGKEYSIZE | number | Number of cipher bits (possible) |
SSL_COMPRESS_METHOD | string | SSL compression method negotiated |
SSL_VERSION_INTERFACE | string | The mod_ssl program version |
SSL_VERSION_LIBRARY | string | The OpenSSL program version |
SSL_CLIENT_M_VERSION | string | The version of the client certificate |
SSL_CLIENT_M_SERIAL | string | The serial of the client certificate |
SSL_CLIENT_S_DN | string | Subject DN in client's certificate |
SSL_CLIENT_S_DN_ x509 | string | Component of client's Subject DN |
SSL_CLIENT_I_DN | string | Issuer DN of client's certificate |
SSL_CLIENT_I_DN_ x509 | string | Component of client's Issuer DN |
SSL_CLIENT_V_START | string | Validity of client's certificate (start time) |
SSL_CLIENT_V_END | string | Validity of client's certificate (end time) |
SSL_CLIENT_V_REMAIN | string | Number of days until client's certificate expires |
SSL_CLIENT_A_SIG | string | Algorithm used for the signature of client's certificate |
SSL_CLIENT_A_KEY | string | Algorithm used for the public key of client's certificate |
SSL_CLIENT_CERT | string | PEM-encoded client certificate |
SSL_CLIENT_CERT_CHAIN_ n | string | PEM-encoded certificates in client certificate chain |
SSL_CLIENT_VERIFY | string | NONE , SUCCESS , GENEROUS or FAILED: reason |
SSL_SERVER_M_VERSION | string | The version of the server certificate |
SSL_SERVER_M_SERIAL | string | The serial of the server certificate |
SSL_SERVER_S_DN | string | Subject DN in server's certificate |
SSL_SERVER_S_DN_ x509 | string | Component of server's Subject DN |
SSL_SERVER_I_DN | string | Issuer DN of server's certificate |
SSL_SERVER_I_DN_ x509 | string | Component of server's Issuer DN |
SSL_SERVER_V_START | string | Validity of server's certificate (start time) |
SSL_SERVER_V_END | string | Validity of server's certificate (end time) |
SSL_SERVER_A_SIG | string | Algorithm used for the signature of server's certificate |
SSL_SERVER_A_KEY | string | Algorithm used for the public key of server's certificate |
SSL_SERVER_CERT | string | PEM-encoded server certificate |
x509 specifies a component of an X.509 DN; one of
C,ST,L,O,OU,CN,T,I,G,S,D,UID,Email
. In Apache 2.1 and
later, x509 may also include a numeric _n
suffix. If the DN in question contains multiple attributes of the
same name, this suffix is used as a zero-based index to select a
particular attribute. For example, where the server certificate
subject DN included two OU attributes, SSL_SERVER_S_DN_OU_0
and
SSL_SERVER_S_DN_OU_1
could be used to reference each. A
variable name without a _n
suffix is equivalent to that
name with a _0
suffix; the first (or only) attribute.
When the environment table is populated using
the StdEnvVars
option of
the SSLOptions
directive, the
first (or only) attribute of any DN is added only under a non-suffixed
name; i.e. no _0
suffixed entries are added.
The format of the *_DN variables has changed in Apache HTTPD
2.3.11. See the LegacyDNStringFormat
option for
SSLOptions
for details.
SSL_CLIENT_V_REMAIN
is only available in version 2.1
and later.
A number of additional environment variables can also be used
in SSLRequire
expressions, or in custom log
formats:
HTTP_USER_AGENT PATH_INFO AUTH_TYPE HTTP_REFERER QUERY_STRING SERVER_SOFTWARE HTTP_COOKIE REMOTE_HOST API_VERSION HTTP_FORWARDED REMOTE_IDENT TIME_YEAR HTTP_HOST IS_SUBREQ TIME_MON HTTP_PROXY_CONNECTION DOCUMENT_ROOT TIME_DAY HTTP_ACCEPT SERVER_ADMIN TIME_HOUR THE_REQUEST SERVER_NAME TIME_MIN REQUEST_FILENAME SERVER_PORT TIME_SEC REQUEST_METHOD SERVER_PROTOCOL TIME_WDAY REQUEST_SCHEME REMOTE_ADDR TIME REQUEST_URI REMOTE_USER
In these contexts, two special formats can also be used:
ENV:variablename
HTTP:headername
When mod_ssl
is built into Apache or at least
loaded (under DSO situation) additional functions exist for the Custom Log Format of
mod_log_config
. First there is an
additional ``%{
varname}x
''
eXtension format function which can be used to expand any variables
provided by any module, especially those provided by mod_ssl which can
you find in the above table.
For backward compatibility there is additionally a special
``%{
name}c
'' cryptography format function
provided. Information about this function is provided in the Compatibility chapter.
CustomLog logs/ssl_request_log "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
mod_ssl
sets "notes" for the request which can be
used in logging with the %{name}n
format
string in mod_log_config
.
The notes supported are as follows:
ssl-access-forbidden
1
if access was
denied due to an SSLRequire
or SSLRequireSSL
directive.ssl-secure-reneg
mod_ssl
is built against a version of
OpenSSL which supports the secure renegotiation extension, this note
is set to the value 1
if SSL is in used for the current
connection, and the client also supports the secure renegotiation
extension. If the client does not support the secure renegotiation
extension, the note is set to the value 0
.
If mod_ssl
is not built against a version of
OpenSSL which supports secure renegotiation, or if SSL is not in use
for the current connection, the note is not set.mod_ssl
provides a few authentication providers for use
with mod_authz_core
's
Require
directive.
The ssl
provider denies access if a connection is not
encrypted with SSL. This is similar to the
SSLRequireSSL
directive.
Require ssl
The ssl
provider allows access if the user is
authenticated with a valid client certificate. This is only
useful if SSLVerifyClient optional
is in effect.
The following example grants access if the user is authenticated either with a client certificate or by username and password.
Require ssl-verify-client
Require valid-user
Description: | File of concatenated PEM-encoded CA Certificates for Client Auth |
---|---|
Syntax: | SSLCACertificateFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the all-in-one file where you can assemble the
Certificates of Certification Authorities (CA) whose clients you deal
with. These are used for Client Authentication. Such a file is simply the
concatenation of the various PEM-encoded Certificate files, in order of
preference. This can be used alternatively and/or additionally to
SSLCACertificatePath
.
SSLCACertificateFile /usr/local/apache2/conf/ssl.crt/ca-bundle-client.crt
Description: | Directory of PEM-encoded CA Certificates for Client Auth |
---|---|
Syntax: | SSLCACertificatePath directory-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the directory where you keep the Certificates of Certification Authorities (CAs) whose clients you deal with. These are used to verify the client certificate on Client Authentication.
The files in this directory have to be PEM-encoded and are accessed through
hash filenames. So usually you can't just place the Certificate files
there: you also have to create symbolic links named
hash-value.N
. And you should always make sure this directory
contains the appropriate symbolic links.
SSLCACertificatePath /usr/local/apache2/conf/ssl.crt/
Description: | File of concatenated PEM-encoded CA Certificates for defining acceptable CA names |
---|---|
Syntax: | SSLCADNRequestFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
When a client certificate is requested by mod_ssl, a list of acceptable Certificate Authority names is sent to the client in the SSL handshake. These CA names can be used by the client to select an appropriate client certificate out of those it has available.
If neither of the directives SSLCADNRequestPath
or SSLCADNRequestFile
are given, then the
set of acceptable CA names sent to the client is the names of all the
CA certificates given by the SSLCACertificateFile
and SSLCACertificatePath
directives; in other
words, the names of the CAs which will actually be used to verify the
client certificate.
In some circumstances, it is useful to be able to send a set of
acceptable CA names which differs from the actual CAs used to verify
the client certificate - for example, if the client certificates are
signed by intermediate CAs. In such cases, SSLCADNRequestPath
and/or SSLCADNRequestFile
can be used; the
acceptable CA names are then taken from the complete set of
certificates in the directory and/or file specified by this pair of
directives.
SSLCADNRequestFile
must
specify an all-in-one file containing a concatenation of
PEM-encoded CA certificates.
SSLCADNRequestFile /usr/local/apache2/conf/ca-names.crt
Description: | Directory of PEM-encoded CA Certificates for defining acceptable CA names |
---|---|
Syntax: | SSLCADNRequestPath directory-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This optional directive can be used to specify the set of
acceptable CA names which will be sent to the client when a
client certificate is requested. See the SSLCADNRequestFile
directive for more
details.
The files in this directory have to be PEM-encoded and are accessed
through hash filenames. So usually you can't just place the
Certificate files there: you also have to create symbolic links named
hash-value.N
. And you should always make sure
this directory contains the appropriate symbolic links.
SSLCADNRequestPath /usr/local/apache2/conf/ca-names.crt/
Description: | Enable CRL-based revocation checking |
---|---|
Syntax: | SSLCARevocationCheck chain|leaf|none |
Default: | SSLCARevocationCheck none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Enables certificate revocation list (CRL) checking. At least one of
SSLCARevocationFile
or SSLCARevocationPath
must be
configured. When set to chain
(recommended setting),
CRL checks are applied to all certificates in the chain, while setting it to
leaf
limits the checks to the end-entity cert.
chain
or leaf
,
CRLs must be available for successful validation
Prior to version 2.3.15, CRL checking in mod_ssl also succeeded when
no CRL(s) were found in any of the locations configured with
SSLCARevocationFile
or SSLCARevocationPath
.
With the introduction of this directive, the behavior has been changed:
when checking is enabled, CRLs must be present for the validation
to succeed - otherwise it will fail with an
"unable to get certificate CRL"
error.
SSLCARevocationCheck chain
Description: | File of concatenated PEM-encoded CA CRLs for Client Auth |
---|---|
Syntax: | SSLCARevocationFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the all-in-one file where you can
assemble the Certificate Revocation Lists (CRL) of Certification
Authorities (CA) whose clients you deal with. These are used
for Client Authentication. Such a file is simply the concatenation of
the various PEM-encoded CRL files, in order of preference. This can be
used alternatively and/or additionally to SSLCARevocationPath
.
SSLCARevocationFile /usr/local/apache2/conf/ssl.crl/ca-bundle-client.crl
Description: | Directory of PEM-encoded CA CRLs for Client Auth |
---|---|
Syntax: | SSLCARevocationPath directory-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the directory where you keep the Certificate Revocation Lists (CRL) of Certification Authorities (CAs) whose clients you deal with. These are used to revoke the client certificate on Client Authentication.
The files in this directory have to be PEM-encoded and are accessed through
hash filenames. So usually you have not only to place the CRL files there.
Additionally you have to create symbolic links named
hash-value.rN
. And you should always make sure this directory
contains the appropriate symbolic links.
SSLCARevocationPath /usr/local/apache2/conf/ssl.crl/
Description: | File of PEM-encoded Server CA Certificates |
---|---|
Syntax: | SSLCertificateChainFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the optional all-in-one file where you can assemble the certificates of Certification Authorities (CA) which form the certificate chain of the server certificate. This starts with the issuing CA certificate of the server certificate and can range up to the root CA certificate. Such a file is simply the concatenation of the various PEM-encoded CA Certificate files, usually in certificate chain order.
This should be used alternatively and/or additionally to SSLCACertificatePath
for explicitly
constructing the server certificate chain which is sent to the browser
in addition to the server certificate. It is especially useful to
avoid conflicts with CA certificates when using client
authentication. Because although placing a CA certificate of the
server certificate chain into SSLCACertificatePath
has the same effect
for the certificate chain construction, it has the side-effect that
client certificates issued by this same CA certificate are also
accepted on client authentication.
But be careful: Providing the certificate chain works only if you are using a single RSA or DSA based server certificate. If you are using a coupled RSA+DSA certificate pair, this will work only if actually both certificates use the same certificate chain. Else the browsers will be confused in this situation.
SSLCertificateChainFile /usr/local/apache2/conf/ssl.crt/ca.crt
Description: | Server PEM-encoded X.509 Certificate file |
---|---|
Syntax: | SSLCertificateFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive points to the PEM-encoded Certificate file for the server and optionally also to the corresponding RSA or DSA Private Key file for it (contained in the same file). If the contained Private Key is encrypted the Pass Phrase dialog is forced at startup time. This directive can be used up to two times (referencing different filenames) when both a RSA and a DSA based server certificate is used in parallel.
SSLCertificateFile /usr/local/apache2/conf/ssl.crt/server.crt
Description: | Server PEM-encoded Private Key file |
---|---|
Syntax: | SSLCertificateKeyFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive points to the PEM-encoded Private Key file for the
server. If the Private Key is not combined with the Certificate in the
SSLCertificateFile
, use this additional directive to
point to the file with the stand-alone Private Key. When
SSLCertificateFile
is used and the file
contains both the Certificate and the Private Key this directive need
not be used. But we strongly discourage this practice. Instead we
recommend you to separate the Certificate and the Private Key. If the
contained Private Key is encrypted, the Pass Phrase dialog is forced
at startup time. This directive can be used up to two times
(referencing different filenames) when both a RSA and a DSA based
private key is used in parallel.
SSLCertificateKeyFile /usr/local/apache2/conf/ssl.key/server.key
Description: | Cipher Suite available for negotiation in SSL handshake |
---|---|
Syntax: | SSLCipherSuite cipher-spec |
Default: | SSLCipherSuite DEFAULT (depends on OpenSSL version) |
Context: | server config, virtual host, directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
This complex directive uses a colon-separated cipher-spec string consisting of OpenSSL cipher specifications to configure the Cipher Suite the client is permitted to negotiate in the SSL handshake phase. Notice that this directive can be used both in per-server and per-directory context. In per-server context it applies to the standard SSL handshake when a connection is established. In per-directory context it forces a SSL renegotiation with the reconfigured Cipher Suite after the HTTP request was read but before the HTTP response is sent.
An SSL cipher specification in cipher-spec is composed of 4 major attributes plus a few extra minor ones:
An SSL cipher can also be an export cipher and is either an SSLv2 or SSLv3/TLSv1 cipher (here TLSv1 is equivalent to SSLv3). To specify which ciphers to use, one can either specify all the Ciphers, one at a time, or use aliases to specify the preference and order for the ciphers (see Table 1).
Tag | Description |
---|---|
Key Exchange Algorithm: | |
kRSA | RSA key exchange |
kDHr | Diffie-Hellman key exchange with RSA key |
kDHd | Diffie-Hellman key exchange with DSA key |
kEDH | Ephemeral (temp.key) Diffie-Hellman key exchange (no cert) |
Authentication Algorithm: | |
aNULL | No authentication |
aRSA | RSA authentication |
aDSS | DSS authentication |
aDH | Diffie-Hellman authentication |
Cipher Encoding Algorithm: | |
eNULL | No encoding |
DES | DES encoding |
3DES | Triple-DES encoding |
RC4 | RC4 encoding |
RC2 | RC2 encoding |
IDEA | IDEA encoding |
MAC Digest Algorithm: | |
MD5 | MD5 hash function |
SHA1 | SHA1 hash function |
SHA | SHA hash function |
Aliases: | |
SSLv2 | all SSL version 2.0 ciphers |
SSLv3 | all SSL version 3.0 ciphers |
TLSv1 | all TLS version 1.0 ciphers |
EXP | all export ciphers |
EXPORT40 | all 40-bit export ciphers only |
EXPORT56 | all 56-bit export ciphers only |
LOW | all low strength ciphers (no export, single DES) |
MEDIUM | all ciphers with 128 bit encryption |
HIGH | all ciphers using Triple-DES |
RSA | all ciphers using RSA key exchange |
DH | all ciphers using Diffie-Hellman key exchange |
EDH | all ciphers using Ephemeral Diffie-Hellman key exchange |
ADH | all ciphers using Anonymous Diffie-Hellman key exchange |
DSS | all ciphers using DSS authentication |
NULL | all ciphers using no encryption |
Now where this becomes interesting is that these can be put together
to specify the order and ciphers you wish to use. To speed this up
there are also aliases (SSLv2, SSLv3, TLSv1, EXP, LOW, MEDIUM,
HIGH
) for certain groups of ciphers. These tags can be joined
together with prefixes to form the cipher-spec. Available
prefixes are:
+
: move matching ciphers to the current location in list-
: remove cipher from list (can be added later again)!
: kill cipher from list completely (can not be added later again)A simpler way to look at all of this is to use the ``openssl ciphers
-v
'' command which provides a nice way to successively create the
correct cipher-spec string. The default cipher-spec string
depends on the version of the OpenSSL libraries used. Let's suppose it is
``RC4-SHA:AES128-SHA:HIGH:MEDIUM:!aNULL:!MD5
'' which
means the following: Put RC4-SHA
and AES128-SHA
at
the beginning. We do this, because these ciphers offer a good compromise
between speed and security. Next, include high and medium security ciphers.
Finally, remove all ciphers which do not authenticate, i.e. for SSL the
Anonymous Diffie-Hellman ciphers, as well as all ciphers which use
MD5
as hash algorithm, because it has been proven insufficient.
$ openssl ciphers -v 'RC4-SHA:AES128-SHA:HIGH:MEDIUM:!aNULL:!MD5' RC4-SHA SSLv3 Kx=RSA Au=RSA Enc=RC4(128) Mac=SHA1 AES128-SHA SSLv3 Kx=RSA Au=RSA Enc=AES(128) Mac=SHA1 DHE-RSA-AES256-SHA SSLv3 Kx=DH Au=RSA Enc=AES(256) Mac=SHA1 ... ... ... ... ... SEED-SHA SSLv3 Kx=RSA Au=RSA Enc=SEED(128) Mac=SHA1 PSK-RC4-SHA SSLv3 Kx=PSK Au=PSK Enc=RC4(128) Mac=SHA1 KRB5-RC4-SHA SSLv3 Kx=KRB5 Au=KRB5 Enc=RC4(128) Mac=SHA1
The complete list of particular RSA & DH ciphers for SSL is given in Table 2.
SSLCipherSuite RSA:!EXP:!NULL:+HIGH:+MEDIUM:-LOW
Cipher-Tag | Protocol | Key Ex. | Auth. | Enc. | MAC | Type |
---|---|---|---|---|---|---|
RSA Ciphers: | ||||||
DES-CBC3-SHA | SSLv3 | RSA | RSA | 3DES(168) | SHA1 | |
DES-CBC3-MD5 | SSLv2 | RSA | RSA | 3DES(168) | MD5 | |
IDEA-CBC-SHA | SSLv3 | RSA | RSA | IDEA(128) | SHA1 | |
RC4-SHA | SSLv3 | RSA | RSA | RC4(128) | SHA1 | |
RC4-MD5 | SSLv3 | RSA | RSA | RC4(128) | MD5 | |
IDEA-CBC-MD5 | SSLv2 | RSA | RSA | IDEA(128) | MD5 | |
RC2-CBC-MD5 | SSLv2 | RSA | RSA | RC2(128) | MD5 | |
RC4-MD5 | SSLv2 | RSA | RSA | RC4(128) | MD5 | |
DES-CBC-SHA | SSLv3 | RSA | RSA | DES(56) | SHA1 | |
RC4-64-MD5 | SSLv2 | RSA | RSA | RC4(64) | MD5 | |
DES-CBC-MD5 | SSLv2 | RSA | RSA | DES(56) | MD5 | |
EXP-DES-CBC-SHA | SSLv3 | RSA(512) | RSA | DES(40) | SHA1 | export |
EXP-RC2-CBC-MD5 | SSLv3 | RSA(512) | RSA | RC2(40) | MD5 | export |
EXP-RC4-MD5 | SSLv3 | RSA(512) | RSA | RC4(40) | MD5 | export |
EXP-RC2-CBC-MD5 | SSLv2 | RSA(512) | RSA | RC2(40) | MD5 | export |
EXP-RC4-MD5 | SSLv2 | RSA(512) | RSA | RC4(40) | MD5 | export |
NULL-SHA | SSLv3 | RSA | RSA | None | SHA1 | |
NULL-MD5 | SSLv3 | RSA | RSA | None | MD5 | |
Diffie-Hellman Ciphers: | ||||||
ADH-DES-CBC3-SHA | SSLv3 | DH | None | 3DES(168) | SHA1 | |
ADH-DES-CBC-SHA | SSLv3 | DH | None | DES(56) | SHA1 | |
ADH-RC4-MD5 | SSLv3 | DH | None | RC4(128) | MD5 | |
EDH-RSA-DES-CBC3-SHA | SSLv3 | DH | RSA | 3DES(168) | SHA1 | |
EDH-DSS-DES-CBC3-SHA | SSLv3 | DH | DSS | 3DES(168) | SHA1 | |
EDH-RSA-DES-CBC-SHA | SSLv3 | DH | RSA | DES(56) | SHA1 | |
EDH-DSS-DES-CBC-SHA | SSLv3 | DH | DSS | DES(56) | SHA1 | |
EXP-EDH-RSA-DES-CBC-SHA | SSLv3 | DH(512) | RSA | DES(40) | SHA1 | export |
EXP-EDH-DSS-DES-CBC-SHA | SSLv3 | DH(512) | DSS | DES(40) | SHA1 | export |
EXP-ADH-DES-CBC-SHA | SSLv3 | DH(512) | None | DES(40) | SHA1 | export |
EXP-ADH-RC4-MD5 | SSLv3 | DH(512) | None | RC4(40) | MD5 | export |
Description: | Disallow compression on the SSL level |
---|---|
Syntax: | SSLCompression on|off |
Default: | SSLCompression on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.4.3 and later, if using OpenSSL 0.9.8 or later; virtual host scope available if using OpenSSL 1.0.0 or later |
This directive allows to disable compression on the SSL level.
Description: | Enable use of a cryptographic hardware accelerator |
---|---|
Syntax: | SSLCryptoDevice engine |
Default: | SSLCryptoDevice builtin |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This directive enables use of a cryptographic hardware accelerator board to offload some of the SSL processing overhead. This directive can only be used if the SSL toolkit is built with "engine" support; OpenSSL 0.9.7 and later releases have "engine" support by default, the separate "-engine" releases of OpenSSL 0.9.6 must be used.
To discover which engine names are supported, run the command
"openssl engine
".
# For a Broadcom accelerator: SSLCryptoDevice ubsec
Description: | SSL Engine Operation Switch |
---|---|
Syntax: | SSLEngine on|off|optional |
Default: | SSLEngine off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive toggles the usage of the SSL/TLS Protocol Engine. This
is should be used inside a <VirtualHost>
section to enable SSL/TLS for a
that virtual host. By default the SSL/TLS Protocol Engine is
disabled for both the main server and all configured virtual hosts.
<VirtualHost _default_:443> SSLEngine on #... </VirtualHost>
In Apache 2.1 and later, SSLEngine
can be set to
optional
. This enables support for
RFC 2817, Upgrading to TLS
Within HTTP/1.1. At this time no web browsers support RFC 2817.
Description: | SSL FIPS mode Switch |
---|---|
Syntax: | SSLFIPS on|off |
Default: | SSLFIPS off |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This directive toggles the usage of the SSL library FIPS_mode flag. It must be set in the global server context and cannot be configured with conflicting settings (SSLFIPS on followed by SSLFIPS off or similar). The mode applies to all SSL library operations.
If httpd was compiled against an SSL library which did not support
the FIPS_mode flag, SSLFIPS on
will fail. Refer to the
FIPS 140-2 Security Policy document of the SSL provider library for
specific requirements to use mod_ssl in a FIPS 140-2 approved mode
of operation; note that mod_ssl itself is not validated, but may be
described as using FIPS 140-2 validated cryptographic module, when
all components are assembled and operated under the guidelines imposed
by the applicable Security Policy.
Description: | Option to prefer the server's cipher preference order |
---|---|
Syntax: | SSLHonorCipherOrder flag |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in Apache 2.1 and later, if using OpenSSL 0.9.7 or later |
When choosing a cipher during an SSLv3 or TLSv1 handshake, normally the client's preference is used. If this directive is enabled, the server's preference will be used instead.
SSLHonorCipherOrder on
Description: | Option to enable support for insecure renegotiation |
---|---|
Syntax: | SSLInsecureRenegotiation flag |
Default: | SSLInsecureRenegotiation off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.2.15 and later, if using OpenSSL 0.9.8m or later |
As originally specified, all versions of the SSL and TLS protocols (up to and including TLS/1.2) were vulnerable to a Man-in-the-Middle attack (CVE-2009-3555) during a renegotiation. This vulnerability allowed an attacker to "prefix" a chosen plaintext to the HTTP request as seen by the web server. A protocol extension was developed which fixed this vulnerability if supported by both client and server.
If mod_ssl
is linked against OpenSSL version 0.9.8m
or later, by default renegotiation is only supported with
clients supporting the new protocol extension. If this directive is
enabled, renegotiation will be allowed with old (unpatched) clients,
albeit insecurely.
If this directive is enabled, SSL connections will be vulnerable to the Man-in-the-Middle prefix attack as described in CVE-2009-3555.
SSLInsecureRenegotiation on
The SSL_SECURE_RENEG
environment variable can be used
from an SSI or CGI script to determine whether secure renegotiation is
supported for a given SSL connection.
Description: | Set the default responder URI for OCSP validation |
---|---|
Syntax: | SSLOCSDefaultResponder uri |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3 and later, if using OpenSSL 0.9.7 or later |
This option sets the default OCSP responder to use. If SSLOCSPOverrideResponder
is not enabled,
the URI given will be used only if no responder URI is specified in
the certificate being verified.
Description: | Enable OCSP validation of the client certificate chain |
---|---|
Syntax: | SSLOCSPEnable flag |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3 and later, if using OpenSSL 0.9.7 or later |
This option enables OCSP validation of the client certificate chain. If this option is enabled, certificates in the client's certificate chain will be validated against an OCSP responder after normal verification (including CRL checks) have taken place.
The OCSP responder used is either extracted from the certificate
itself, or derived by configuration; see the
SSLOCSPDefaultResponder
and
SSLOCSPOverrideResponder
directives.
SSLVerifyClient on SSLOCSPEnable on SSLOCSPDefaultResponder http://responder.example.com:8888/responder SSLOCSPOverrideResponder on
Description: | Force use of the default responder URI for OCSP validation |
---|---|
Syntax: | SSLOCSPOverrideResponder flag |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3 and later, if using OpenSSL 0.9.7 or later |
This option forces the configured default OCSP responder to be used during OCSP certificate validation, regardless of whether the certificate being validated references an OCSP responder.
Description: | Timeout for OCSP queries |
---|---|
Syntax: | SSLOCSPResponderTimeout seconds |
Default: | SSLOCSPResponderTimeout 10 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3 and later, if using OpenSSL 0.9.7 or later |
This option sets the timeout for queries to OCSP responders, when
SSLOCSPEnable
is turned on.
Description: | Maximum allowable age for OCSP responses |
---|---|
Syntax: | SSLOCSPResponseMaxAge seconds |
Default: | SSLOCSPResponseMaxAge -1 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3 and later, if using OpenSSL 0.9.7 or later |
This option sets the maximum allowable age ("freshness") for OCSP responses.
The default value (-1
) does not enforce a maximum age,
which means that OCSP responses are considered valid as long as their
nextUpdate
field is in the future.
Description: | Maximum allowable time skew for OCSP response validation |
---|---|
Syntax: | SSLOCSPResponseTimeSkew seconds |
Default: | SSLOCSPResponseTimeSkew 300 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3 and later, if using OpenSSL 0.9.7 or later |
This option sets the maximum allowable time skew for OCSP responses
(when checking their thisUpdate
and nextUpdate
fields).
Description: | Configure various SSL engine run-time options |
---|---|
Syntax: | SSLOptions [+|-]option ... |
Context: | server config, virtual host, directory, .htaccess |
Override: | Options |
Status: | Extension |
Module: | mod_ssl |
This directive can be used to control various run-time options on a
per-directory basis. Normally, if multiple SSLOptions
could apply to a directory, then the most specific one is taken
completely; the options are not merged. However if all the
options on the SSLOptions
directive are preceded by a
plus (+
) or minus (-
) symbol, the options
are merged. Any options preceded by a +
are added to the
options currently in force, and any options preceded by a
-
are removed from the options currently in force.
The available options are:
StdEnvVars
When this option is enabled, the standard set of SSL related CGI/SSI environment variables are created. This per default is disabled for performance reasons, because the information extraction step is a rather expensive operation. So one usually enables this option for CGI and SSI requests only.
ExportCertData
When this option is enabled, additional CGI/SSI environment variables are
created: SSL_SERVER_CERT
, SSL_CLIENT_CERT
and
SSL_CLIENT_CERT_CHAIN_
n (with n = 0,1,2,..).
These contain the PEM-encoded X.509 Certificates of server and client for
the current HTTPS connection and can be used by CGI scripts for deeper
Certificate checking. Additionally all other certificates of the client
certificate chain are provided, too. This bloats up the environment a
little bit which is why you have to use this option to enable it on
demand.
FakeBasicAuth
When this option is enabled, the Subject Distinguished Name (DN) of the
Client X509 Certificate is translated into a HTTP Basic Authorization
username. This means that the standard Apache authentication methods can
be used for access control. The user name is just the Subject of the
Client's X509 Certificate (can be determined by running OpenSSL's
openssl x509
command: openssl x509 -noout -subject -in
certificate.crt
). Note that no password is
obtained from the user. Every entry in the user file needs this password:
``xxj31ZMTZzkVA
'', which is the DES-encrypted version of the
word `password
''. Those who live under MD5-based encryption
(for instance under FreeBSD or BSD/OS, etc.) should use the following MD5
hash of the same word: ``$1$OXLyS...$Owx8s2/m9/gfkcRVXzgoE/
''.
StrictRequire
This forces forbidden access when SSLRequireSSL
or
SSLRequire
successfully decided that access should be
forbidden. Usually the default is that in the case where a ``Satisfy
any
'' directive is used, and other access restrictions are passed,
denial of access due to SSLRequireSSL
or
SSLRequire
is overridden (because that's how the Apache
Satisfy
mechanism should work.) But for strict access restriction
you can use SSLRequireSSL
and/or SSLRequire
in
combination with an ``SSLOptions +StrictRequire
''. Then an
additional ``Satisfy Any
'' has no chance once mod_ssl has
decided to deny access.
OptRenegotiate
This enables optimized SSL connection renegotiation handling when SSL directives are used in per-directory context. By default a strict scheme is enabled where every per-directory reconfiguration of SSL parameters causes a full SSL renegotiation handshake. When this option is used mod_ssl tries to avoid unnecessary handshakes by doing more granular (but still safe) parameter checks. Nevertheless these granular checks sometimes maybe not what the user expects, so enable this on a per-directory basis only, please.
LegacyDNStringFormat
This option influences how values of the
SSL_{CLIENT,SERVER}_{I,S}_DN
variables are formatted. Since
version 2.3.11, Apache HTTPD uses a RFC 2253 compatible format by
default. This uses commas as delimiters between the attributes, allows the
use of non-ASCII characters (which are converted to UTF8), escapes
various special characters with backslashes, and sorts the attributes
with the "C" attribute last.
If LegacyDNStringFormat
is set, the old format will be
used which sorts the "C" attribute first, uses slashes as separators, and
does not handle non-ASCII and special characters in any consistent way.
SSLOptions +FakeBasicAuth -StrictRequire <Files ~ "\.(cgi|shtml)$"> SSLOptions +StdEnvVars -ExportCertData <Files>
Description: | Type of pass phrase dialog for encrypted private keys |
---|---|
Syntax: | SSLPassPhraseDialog type |
Default: | SSLPassPhraseDialog builtin |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
When Apache starts up it has to read the various Certificate (see
SSLCertificateFile
) and
Private Key (see SSLCertificateKeyFile
) files of the
SSL-enabled virtual servers. Because for security reasons the Private
Key files are usually encrypted, mod_ssl needs to query the
administrator for a Pass Phrase in order to decrypt those files. This
query can be done in two ways which can be configured by
type:
builtin
This is the default where an interactive terminal dialog occurs at startup time just before Apache detaches from the terminal. Here the administrator has to manually enter the Pass Phrase for each encrypted Private Key file. Because a lot of SSL-enabled virtual hosts can be configured, the following reuse-scheme is used to minimize the dialog: When a Private Key file is encrypted, all known Pass Phrases (at the beginning there are none, of course) are tried. If one of those known Pass Phrases succeeds no dialog pops up for this particular Private Key file. If none succeeded, another Pass Phrase is queried on the terminal and remembered for the next round (where it perhaps can be reused).
This scheme allows mod_ssl to be maximally flexible (because for N encrypted Private Key files you can use N different Pass Phrases - but then you have to enter all of them, of course) while minimizing the terminal dialog (i.e. when you use a single Pass Phrase for all N Private Key files this Pass Phrase is queried only once).
|/path/to/program [args...]
This mode allows an external program to be used which acts as a
pipe to a particular input device; the program is sent the standard
prompt text used for the builtin
mode on
stdin
, and is expected to write password strings on
stdout
. If several passwords are needed (or an
incorrect password is entered), additional prompt text will be
written subsequent to the first password being returned, and more
passwords must then be written back.
exec:/path/to/program
Here an external program is configured which is called at startup for each
encrypted Private Key file. It is called with two arguments (the first is
of the form ``servername:portnumber
'', the second is either
``RSA
'' or ``DSA
''), which indicate for which
server and algorithm it has to print the corresponding Pass Phrase to
stdout
. The intent is that this external program first runs
security checks to make sure that the system is not compromised by an
attacker, and only when these checks were passed successfully it provides
the Pass Phrase.
Both these security checks, and the way the Pass Phrase is determined, can
be as complex as you like. Mod_ssl just defines the interface: an
executable program which provides the Pass Phrase on stdout
.
Nothing more or less! So, if you're really paranoid about security, here
is your interface. Anything else has to be left as an exercise to the
administrator, because local security requirements are so different.
The reuse-algorithm above is used here, too. In other words: The external program is called only once per unique Pass Phrase.
SSLPassPhraseDialog exec:/usr/local/apache/sbin/pp-filter
Description: | Configure usable SSL/TLS protocol versions |
---|---|
Syntax: | SSLProtocol [+|-]protocol ... |
Default: | SSLProtocol all |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive can be used to control which versions of the SSL/TLS protocol will be accepted in new connections.
The available (case-insensitive) protocols are:
SSLv3
This is the Secure Sockets Layer (SSL) protocol, version 3.0, from the Netscape Corporation. It is the successor to SSLv2 and the predecessor to TLSv1. It's supported by almost all popular browsers.
TLSv1
This is the Transport Layer Security (TLS) protocol, version 1.0. It is the successor to SSLv3 and is defined in RFC 2246.
TLSv1.1
(when using OpenSSL 1.0.1 and later)
A revision of the TLS 1.0 protocol, as defined in RFC 4346.
TLSv1.2
(when using OpenSSL 1.0.1 and later)
A revision of the TLS 1.1 protocol, as defined in RFC 5246.
all
This is a shortcut for ``+SSLv3 +TLSv1
'' or
- when using OpenSSL 1.0.1 and later -
``+SSLv3 +TLSv1 +TLSv1.1 +TLSv1.2
, respectively.
SSLProtocol TLSv1
Description: | File of concatenated PEM-encoded CA Certificates for Remote Server Auth |
---|---|
Syntax: | SSLProxyCACertificateFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the all-in-one file where you can assemble the
Certificates of Certification Authorities (CA) whose remote servers you deal
with. These are used for Remote Server Authentication. Such a file is simply the
concatenation of the various PEM-encoded Certificate files, in order of
preference. This can be used alternatively and/or additionally to
SSLProxyCACertificatePath
.
SSLProxyCACertificateFile /usr/local/apache2/conf/ssl.crt/ca-bundle-remote-server.crt
Description: | Directory of PEM-encoded CA Certificates for Remote Server Auth |
---|---|
Syntax: | SSLProxyCACertificatePath directory-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the directory where you keep the Certificates of Certification Authorities (CAs) whose remote servers you deal with. These are used to verify the remote server certificate on Remote Server Authentication.
The files in this directory have to be PEM-encoded and are accessed through
hash filenames. So usually you can't just place the Certificate files
there: you also have to create symbolic links named
hash-value.N
. And you should always make sure this directory
contains the appropriate symbolic links.
SSLProxyCACertificatePath /usr/local/apache2/conf/ssl.crt/
Description: | Enable CRL-based revocation checking for Remote Server Auth |
---|---|
Syntax: | SSLProxyCARevocationCheck chain|leaf|none |
Default: | SSLProxyCARevocationCheck none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Enables certificate revocation list (CRL) checking for the
remote servers you deal with. At least one of
SSLProxyCARevocationFile
or SSLProxyCARevocationPath
must be
configured. When set to chain
(recommended setting),
CRL checks are applied to all certificates in the chain, while setting it to
leaf
limits the checks to the end-entity cert.
chain
or leaf
,
CRLs must be available for successful validation
Prior to version 2.3.15, CRL checking in mod_ssl also succeeded when
no CRL(s) were found in any of the locations configured with
SSLProxyCARevocationFile
or SSLProxyCARevocationPath
.
With the introduction of this directive, the behavior has been changed:
when checking is enabled, CRLs must be present for the validation
to succeed - otherwise it will fail with an
"unable to get certificate CRL"
error.
SSLProxyCARevocationCheck chain
Description: | File of concatenated PEM-encoded CA CRLs for Remote Server Auth |
---|---|
Syntax: | SSLProxyCARevocationFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the all-in-one file where you can
assemble the Certificate Revocation Lists (CRL) of Certification
Authorities (CA) whose remote servers you deal with. These are used
for Remote Server Authentication. Such a file is simply the concatenation of
the various PEM-encoded CRL files, in order of preference. This can be
used alternatively and/or additionally to SSLProxyCARevocationPath
.
SSLProxyCARevocationFile /usr/local/apache2/conf/ssl.crl/ca-bundle-remote-server.crl
Description: | Directory of PEM-encoded CA CRLs for Remote Server Auth |
---|---|
Syntax: | SSLProxyCARevocationPath directory-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the directory where you keep the Certificate Revocation Lists (CRL) of Certification Authorities (CAs) whose remote servers you deal with. These are used to revoke the remote server certificate on Remote Server Authentication.
The files in this directory have to be PEM-encoded and are accessed through
hash filenames. So usually you have not only to place the CRL files there.
Additionally you have to create symbolic links named
hash-value.rN
. And you should always make sure this directory
contains the appropriate symbolic links.
SSLProxyCARevocationPath /usr/local/apache2/conf/ssl.crl/
Description: | Whether to check the remote server certificates CN field |
---|---|
Syntax: | SSLProxyCheckPeerCN on|off |
Default: | SSLProxyCheckPeerCN on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets whether the remote server certificates CN field is compared against the hostname of the request URL. If both are not equal a 502 status code (Bad Gateway) is sent.
SSLProxyCheckPeerCN on
Description: | Whether to check if remote server certificate is expired |
---|---|
Syntax: | SSLProxyCheckPeerExpire on|off |
Default: | SSLProxyCheckPeerExpire on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets whether it is checked if the remote server certificate is expired or not. If the check fails a 502 status code (Bad Gateway) is sent.
SSLProxyCheckPeerExpire on
Description: | Cipher Suite available for negotiation in SSL proxy handshake |
---|---|
Syntax: | SSLProxyCipherSuite cipher-spec |
Default: | SSLProxyCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP |
Context: | server config, virtual host, directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
Equivalent to SSLCipherSuite
, but for the proxy connection.
Please refer to SSLCipherSuite
for additional information.
Description: | SSL Proxy Engine Operation Switch |
---|---|
Syntax: | SSLProxyEngine on|off |
Default: | SSLProxyEngine off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive toggles the usage of the SSL/TLS Protocol Engine for proxy. This
is usually used inside a <VirtualHost>
section to enable SSL/TLS for proxy
usage in a particular virtual host. By default the SSL/TLS Protocol Engine is
disabled for proxy image both for the main server and all configured virtual hosts.
Note that the SSLProxyEngine directive should not, in general, be included in a virtual host that will be acting as a forward proxy (using <Proxy> or <ProxyRequest> directives. SSLProxyEngine is not required to enable a forward proxy server to proxy SSL/TLS requests.
<VirtualHost _default_:443> SSLProxyEngine on #... </VirtualHost>
Description: | File of concatenated PEM-encoded CA certificates to be used by the proxy for choosing a certificate |
---|---|
Syntax: | SSLProxyMachineCertificateChainFile filename |
Context: | server config |
Override: | Not applicable |
Status: | Extension |
Module: | mod_ssl |
This directive sets the all-in-one file where you keep the certificate chain for all of the client certs in use. This directive will be needed if the remote server presents a list of CA certificates that are not direct signers of one of the configured client certificates.
This referenced file is simply the concatenation of the various PEM-encoded certificate files. Upon startup, each client certificate configured will be examined and a chain of trust will be constructed.
If this directive is enabled, all of the certificates in the file will be
trusted as if they were also in
SSLProxyCACertificateFile
.
SSLProxyMachineCertificateChainFile /usr/local/apache2/conf/ssl.crt/proxyCA.pem
Description: | File of concatenated PEM-encoded client certificates and keys to be used by the proxy |
---|---|
Syntax: | SSLProxyMachineCertificateFile filename |
Context: | server config |
Override: | Not applicable |
Status: | Extension |
Module: | mod_ssl |
This directive sets the all-in-one file where you keep the certificates and keys used for authentication of the proxy server to remote servers.
This referenced file is simply the concatenation of the various PEM-encoded
certificate files, in order of preference. Use this directive alternatively
or additionally to SSLProxyMachineCertificatePath
.
Currently there is no support for encrypted private keys
SSLProxyMachineCertificateFile /usr/local/apache2/conf/ssl.crt/proxy.pem
Description: | Directory of PEM-encoded client certificates and keys to be used by the proxy |
---|---|
Syntax: | SSLProxyMachineCertificatePath directory |
Context: | server config |
Override: | Not applicable |
Status: | Extension |
Module: | mod_ssl |
This directive sets the directory where you keep the certificates and keys used for authentication of the proxy server to remote servers.
The files in this directory must be PEM-encoded and are accessed through
hash filenames. Additionally, you must create symbolic links named
hash-value.N
. And you should always make sure this
directory contains the appropriate symbolic links.
Currently there is no support for encrypted private keys
SSLProxyMachineCertificatePath /usr/local/apache2/conf/proxy.crt/
Description: | Configure usable SSL protocol flavors for proxy usage |
---|---|
Syntax: | SSLProxyProtocol [+|-]protocol ... |
Default: | SSLProxyProtocol all |
Context: | server config, virtual host |
Override: | Options |
Status: | Extension |
Module: | mod_ssl |
This directive can be used to control the SSL protocol flavors mod_ssl should use when establishing its server environment for proxy . It will only connect to servers using one of the provided protocols.
Please refer to SSLProtocol
for additional information.
Description: | Type of remote server Certificate verification |
---|---|
Syntax: | SSLProxyVerify level |
Default: | SSLProxyVerify none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
When a proxy is configured to forward requests to a remote SSL server, this directive can be used to configure certificate verification of the remote server.
The following levels are available for level:
In practice only levels none and require are really interesting, because level optional doesn't work with all servers and level optional_no_ca is actually against the idea of authentication (but can be used to establish SSL test pages, etc.)
SSLProxyVerify require
Description: | Maximum depth of CA Certificates in Remote Server Certificate verification |
---|---|
Syntax: | SSLProxyVerifyDepth number |
Default: | SSLProxyVerifyDepth 1 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets how deeply mod_ssl should verify before deciding that the remote server does not have a valid certificate.
The depth actually is the maximum number of intermediate certificate issuers,
i.e. the number of CA certificates which are max allowed to be followed while
verifying the remote server certificate. A depth of 0 means that self-signed
remote server certificates are accepted only, the default depth of 1 means
the remote server certificate can be self-signed or has to be signed by a CA
which is directly known to the server (i.e. the CA's certificate is under
SSLProxyCACertificatePath
), etc.
SSLProxyVerifyDepth 10
Description: | Pseudo Random Number Generator (PRNG) seeding source |
---|---|
Syntax: | SSLRandomSeed context source
[bytes] |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This configures one or more sources for seeding the Pseudo Random Number
Generator (PRNG) in OpenSSL at startup time (context is
startup
) and/or just before a new SSL connection is established
(context is connect
). This directive can only be used
in the global server context because the PRNG is a global facility.
The following source variants are available:
builtin
This is the always available builtin seeding source. Its usage consumes minimum CPU cycles under runtime and hence can be always used without drawbacks. The source used for seeding the PRNG contains of the current time, the current process id and (when applicable) a randomly chosen 1KB extract of the inter-process scoreboard structure of Apache. The drawback is that this is not really a strong source and at startup time (where the scoreboard is still not available) this source just produces a few bytes of entropy. So you should always, at least for the startup, use an additional seeding source.
file:/path/to/source
This variant uses an external file /path/to/source
as the
source for seeding the PRNG. When bytes is specified, only the
first bytes number of bytes of the file form the entropy (and
bytes is given to /path/to/source
as the first
argument). When bytes is not specified the whole file forms the
entropy (and 0
is given to /path/to/source
as
the first argument). Use this especially at startup time, for instance
with an available /dev/random
and/or
/dev/urandom
devices (which usually exist on modern Unix
derivatives like FreeBSD and Linux).
But be careful: Usually /dev/random
provides only as
much entropy data as it actually has, i.e. when you request 512 bytes of
entropy, but the device currently has only 100 bytes available two things
can happen: On some platforms you receive only the 100 bytes while on
other platforms the read blocks until enough bytes are available (which
can take a long time). Here using an existing /dev/urandom
is
better, because it never blocks and actually gives the amount of requested
data. The drawback is just that the quality of the received data may not
be the best.
exec:/path/to/program
This variant uses an external executable
/path/to/program
as the source for seeding the
PRNG. When bytes is specified, only the first
bytes number of bytes of its stdout
contents
form the entropy. When bytes is not specified, the
entirety of the data produced on stdout
form the
entropy. Use this only at startup time when you need a very strong
seeding with the help of an external program (for instance as in
the example above with the truerand
utility you can
find in the mod_ssl distribution which is based on the AT&T
truerand library). Using this in the connection context
slows down the server too dramatically, of course. So usually you
should avoid using external programs in that context.
egd:/path/to/egd-socket
(Unix only)
This variant uses the Unix domain socket of the external Entropy Gathering Daemon (EGD) (see http://www.lothar.com/tech /crypto/) to seed the PRNG. Use this if no random device exists on your platform.
SSLRandomSeed startup builtin SSLRandomSeed startup file:/dev/random SSLRandomSeed startup file:/dev/urandom 1024 SSLRandomSeed startup exec:/usr/local/bin/truerand 16 SSLRandomSeed connect builtin SSLRandomSeed connect file:/dev/random SSLRandomSeed connect file:/dev/urandom 1024
Description: | Set the size for the SSL renegotiation buffer |
---|---|
Syntax: | SSLRenegBufferSize bytes |
Default: | SSLRenegBufferSize 131072 |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
If an SSL renegotiation is required in per-location context, for
example, any use of SSLVerifyClient
in a Directory or
Location block, then mod_ssl
must buffer any HTTP
request body into memory until the new SSL handshake can be performed.
This directive can be used to set the amount of memory that will be
used for this buffer.
Note that in many configurations, the client sending the request body will be untrusted so a denial of service attack by consumption of memory must be considered when changing this configuration setting.
SSLRenegBufferSize 262144
Description: | Allow access only when an arbitrarily complex boolean expression is true |
---|---|
Syntax: | SSLRequire expression |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
SSLRequire
is deprecated and should in general be replaced
by Require expr. The so called
ap_expr syntax of Require expr
is
a superset of the syntax of SSLRequire
, with the following
exception:
In SSLRequire
, the comparison operators <
,
<=
, ... are completely equivalent to the operators
lt
, le
, ... and work in a somewhat peculiar way that
first compares the length of two strings and then the lexical order.
On the other hand, ap_expr has two sets of
comparison operators: The operators <
,
<=
, ... do lexical string comparison, while the operators
-lt
, -le
, ... do integer comparison.
For the latter, there are also aliases without the leading dashes:
lt
, le
, ...
This directive specifies a general access requirement which has to be fulfilled in order to allow access. It is a very powerful directive because the requirement specification is an arbitrarily complex boolean expression containing any number of access checks.
The expression must match the following syntax (given as a BNF grammar notation):
expr ::= "true" | "false" | "!" expr | expr "&&" expr | expr "||" expr | "(" expr ")" | comp comp ::= word "==" word | word "eq" word | word "!=" word | word "ne" word | word "<" word | word "lt" word | word "<=" word | word "le" word | word ">" word | word "gt" word | word ">=" word | word "ge" word | word "in" "{" wordlist "}" | word "in" "PeerExtList(" word ")" | word "=~" regex | word "!~" regex wordlist ::= word | wordlist "," word word ::= digit | cstring | variable | function digit ::= [0-9]+ cstring ::= "..." variable ::= "%{" varname "}" function ::= funcname "(" funcargs ")"
For varname
any of the variables described in Environment Variables can be used. For
funcname
the available functions are listed in
the ap_expr documentation.
The expression is parsed into an internal machine representation when the configuration is loaded, and then evaluated during request processing. In .htaccess context, the expression is both parsed and executed each time the .htaccess file is encountered during request processing.
SSLRequire ( %{SSL_CIPHER} !~ m/^(EXP|NULL)-/ \ and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \ and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \ and %{TIME_WDAY} -ge 1 and %{TIME_WDAY} -le 5 \ and %{TIME_HOUR} -ge 8 and %{TIME_HOUR} -le 20 ) \ or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/
The PeerExtList(object-ID)
function expects
to find zero or more instances of the X.509 certificate extension
identified by the given object ID (OID) in the client certificate.
The expression evaluates to true if the left-hand side string matches
exactly against the value of an extension identified with this OID.
(If multiple extensions with the same OID are present, at least one
extension must match).
SSLRequire "foobar" in PeerExtList("1.2.3.4.5.6")
The object ID can be specified either as a descriptive
name recognized by the SSL library, such as "nsComment"
,
or as a numeric OID, such as "1.2.3.4.5.6"
.
Expressions with types known to the SSL library are rendered to a string before comparison. For an extension with a type not recognized by the SSL library, mod_ssl will parse the value if it is one of the primitive ASN.1 types UTF8String, IA5String, VisibleString, or BMPString. For an extension of one of these types, the string value will be converted to UTF-8 if necessary, then compared against the left-hand-side expression.
Description: | Deny access when SSL is not used for the HTTP request |
---|---|
Syntax: | SSLRequireSSL |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
This directive forbids access unless HTTP over SSL (i.e. HTTPS) is enabled for the current connection. This is very handy inside the SSL-enabled virtual host or directories for defending against configuration errors that expose stuff that should be protected. When this directive is present all requests are denied which are not using SSL.
SSLRequireSSL
Description: | Type of the global/inter-process SSL Session Cache |
---|---|
Syntax: | SSLSessionCache type |
Default: | SSLSessionCache none |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This configures the storage type of the global/inter-process SSL Session Cache. This cache is an optional facility which speeds up parallel request processing. For requests to the same server process (via HTTP keep-alive), OpenSSL already caches the SSL session information locally. But because modern clients request inlined images and other data via parallel requests (usually up to four parallel requests are common) those requests are served by different pre-forked server processes. Here an inter-process cache helps to avoid unnecessary session handshakes.
The following five storage types are currently supported:
none
This disables the global/inter-process Session Cache. This will incur a noticeable speed penalty and may cause problems if using certain browsers, particularly if client certificates are enabled. This setting is not recommended.
nonenotnull
This disables any global/inter-process Session Cache. However it does force OpenSSL to send a non-null session ID to accommodate buggy clients that require one.
dbm:/path/to/datafile
This makes use of a DBM hashfile on the local disk to
synchronize the local OpenSSL memory caches of the server
processes. This session cache may suffer reliability issues under
high load. To use this, ensure that
mod_socache_dbm
is loaded.
shmcb:/path/to/datafile
[(
size)
]
This makes use of a high-performance cyclic buffer
(approx. size bytes in size) inside a shared memory
segment in RAM (established via /path/to/datafile
) to
synchronize the local OpenSSL memory caches of the server
processes. This is the recommended session cache. To use this,
ensure that mod_socache_shmcb
is loaded.
dc:UNIX:/path/to/socket
This makes use of the distcache distributed session
caching libraries. The argument should specify the location of
the server or proxy to be used using the distcache address syntax;
for example, UNIX:/path/to/socket
specifies a UNIX
domain socket (typically a local dc_client proxy);
IP:server.example.com:9001
specifies an IP
address. To use this, ensure that
mod_socache_dc
is loaded.
SSLSessionCache dbm:/usr/local/apache/logs/ssl_gcache_data SSLSessionCache shmcb:/usr/local/apache/logs/ssl_gcache_data(512000)
The ssl-cache
mutex is used to serialize access to
the session cache to prevent corruption. This mutex can be configured
using the Mutex
directive.
Description: | Number of seconds before an SSL session expires in the Session Cache |
---|---|
Syntax: | SSLSessionCacheTimeout seconds |
Default: | SSLSessionCacheTimeout 300 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets the timeout in seconds for the information stored in the global/inter-process SSL Session Cache and the OpenSSL internal memory cache. It can be set as low as 15 for testing, but should be set to higher values like 300 in real life.
SSLSessionCacheTimeout 600
Description: | Persistent encryption/decryption key for TLS session tickets |
---|---|
Syntax: | SSLSessionTicketKeyFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.4.0 and later, if using OpenSSL 0.9.8h or later |
Optionally configures a secret key for encrypting and decrypting TLS session tickets, as defined in RFC 5077. Primarily suitable for clustered environments where TLS sessions information should be shared between multiple nodes. For single-instance httpd setups, it is recommended to not configure a ticket key file, but to rely on (random) keys generated by mod_ssl at startup, instead.
The ticket key file must contain 48 bytes of random data, preferrably created from a high-entropy source. On a Unix-based system, a ticket key file can be created as follows:
dd if=/dev/random of=/path/to/file.tkey bs=1 count=48
Ticket keys should be rotated (replaced) on a frequent basis, as this is the only way to invalidate an existing session ticket - OpenSSL currently doesn't allow to specify a limit for ticket lifetimes.
The ticket key file contains sensitive keying material and should
be protected with file permissions similar to those used for
SSLCertificateKeyFile
.
Description: | Configures the OCSP stapling cache |
---|---|
Syntax: | SSLStaplingCache type |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
Configures the cache used to store OCSP responses which get included
in the TLS handshake if SSLUseStapling
is enabled. Configuration of a cache is mandatory for OCSP stapling.
With the exception of none
and nonenotnull
,
the same storage types are supported as with
SSLSessionCache
.
Description: | Number of seconds before expiring invalid responses in the OCSP stapling cache |
---|---|
Syntax: | SSLStaplingErrorCacheTimeout seconds |
Default: | SSLStaplingErrorCacheTimeout 600 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
Sets the timeout in seconds before invalid responses
in the OCSP stapling cache (configured through SSLStaplingCache
) will expire.
To set the cache timeout for valid responses, see
SSLStaplingStandardCacheTimeout
.
Description: | Synthesize "tryLater" responses for failed OCSP stapling queries |
---|---|
Syntax: | SSLStaplingFakeTryLater on|off |
Default: | SSLStaplingFakeTryLater on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
When enabled and a query to an OCSP responder for stapling
purposes fails, mod_ssl will synthesize a "tryLater" response for the
client. Only effective if SSLStaplingReturnResponderErrors
is also enabled.
Description: | Override the OCSP responder URI specified in the certificate's AIA extension |
---|---|
Syntax: | SSLStaplingForceURL uri |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
This directive overrides the URI of an OCSP responder as obtained from the authorityInfoAccess (AIA) extension of the certificate. Of potential use when going through a proxy for retrieving OCSP queries.
Description: | Timeout for OCSP stapling queries |
---|---|
Syntax: | SSLStaplingResponderTimeout seconds |
Default: | SSLStaplingResponderTimeout 10 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
This option sets the timeout for queries to OCSP responders when
SSLUseStapling
is enabled
and mod_ssl is querying a responder for OCSP stapling purposes.
Description: | Maximum allowable age for OCSP stapling responses |
---|---|
Syntax: | SSLStaplingResponseMaxAge seconds |
Default: | SSLStaplingResponseMaxAge -1 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
This option sets the maximum allowable age ("freshness") when
considering OCSP responses for stapling purposes, i.e. when
SSLUseStapling
is turned on.
The default value (-1
) does not enforce a maximum age,
which means that OCSP responses are considered valid as long as their
nextUpdate
field is in the future.
Description: | Maximum allowable time skew for OCSP stapling response validation |
---|---|
Syntax: | SSLStaplingResponseTimeSkew seconds |
Default: | SSLStaplingResponseTimeSkew 300 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
This option sets the maximum allowable time skew when mod_ssl checks the
thisUpdate
and nextUpdate
fields of OCSP responses
which get included in the TLS handshake (OCSP stapling). Only applicable
if SSLUseStapling
is turned on.
Description: | Pass stapling related OCSP errors on to client |
---|---|
Syntax: | SSLStaplingReturnResponderErrors on|off |
Default: | SSLStaplingReturnResponderErrors on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
When enabled, mod_ssl will pass responses from unsuccessful
stapling related OCSP queries (such as status errors, expired responses etc.)
on to the client. If set to off
, no stapled responses
for failed queries will be included in the TLS handshake.
Description: | Number of seconds before expiring responses in the OCSP stapling cache |
---|---|
Syntax: | SSLStaplingStandardCacheTimeout seconds |
Default: | SSLStaplingStandardCacheTimeout 3600 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
Sets the timeout in seconds before responses in the OCSP stapling cache
(configured through SSLStaplingCache
)
will expire. This directive applies to valid responses, while
SSLStaplingErrorCacheTimeout
is
used for controlling the timeout for invalid/unavailable responses.
Description: | Whether to allow non-SNI clients to access a name-based virtual host. |
---|---|
Syntax: | SSLStrictSNIVHostCheck on|off |
Default: | SSLStrictSNIVHostCheck off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in Apache 2.2.12 and later |
This directive sets whether a non-SNI client is allowed to access a name-based
virtual host. If set to on
in the default name-based virtual
host, clients that are SNI unaware will not be allowed to access any
virtual host, belonging to this particular IP / port combination.
If set to on
in any other virtual host, SNI unaware clients
are not allowed to access this particular virtual host.
This option is only available if httpd was compiled against an SNI capable version of OpenSSL.
SSLStrictSNIVHostCheck on
Description: | Variable name to determine user name |
---|---|
Syntax: | SSLUserName varname |
Context: | server config, directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in Apache 2.0.51 and later |
This directive sets the "user" field in the Apache request object.
This is used by lower modules to identify the user with a character
string. In particular, this may cause the environment variable
REMOTE_USER
to be set. The varname can be
any of the SSL environment variables.
Note that this directive has no effect if the
FakeBasicAuth
option is used (see SSLOptions).
SSLUserName SSL_CLIENT_S_DN_CN
Description: | Enable stapling of OCSP responses in the TLS handshake |
---|---|
Syntax: | SSLUseStapling on|off |
Default: | SSLUseStapling off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.3.3 and later, if using OpenSSL 0.9.8h or later |
This option enables OCSP stapling, as defined by the "Certificate
Status Request" TLS extension specified in RFC 6066. If enabled (and
requested by the client), mod_ssl will include an OCSP response
for its own certificate in the TLS handshake. Configuring an
SSLStaplingCache
is a
prerequisite for enabling OCSP stapling.
OCSP stapling relieves the client of querying the OCSP responder
on its own, but it should be noted that in its current specification,
the server's CertificateStatus
reply may only include an
OCSP response for a single cert. For server certificates with intermediate
CA certificates in their chain (the typical case nowadays),
stapling in its current form therefore only partially achieves the
stated goal of "saving roundtrips and resources" - see also the
"Adding Multiple TLS Certificate Status Extension requests" Internet draft.
Description: | Type of Client Certificate verification |
---|---|
Syntax: | SSLVerifyClient level |
Default: | SSLVerifyClient none |
Context: | server config, virtual host, directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
This directive sets the Certificate verification level for the Client Authentication. Notice that this directive can be used both in per-server and per-directory context. In per-server context it applies to the client authentication process used in the standard SSL handshake when a connection is established. In per-directory context it forces a SSL renegotiation with the reconfigured client verification level after the HTTP request was read but before the HTTP response is sent.
The following levels are available for level:
In practice only levels none and require are really interesting, because level optional doesn't work with all browsers and level optional_no_ca is actually against the idea of authentication (but can be used to establish SSL test pages, etc.)
SSLVerifyClient require
Description: | Maximum depth of CA Certificates in Client Certificate verification |
---|---|
Syntax: | SSLVerifyDepth number |
Default: | SSLVerifyDepth 1 |
Context: | server config, virtual host, directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
This directive sets how deeply mod_ssl should verify before deciding that the clients don't have a valid certificate. Notice that this directive can be used both in per-server and per-directory context. In per-server context it applies to the client authentication process used in the standard SSL handshake when a connection is established. In per-directory context it forces a SSL renegotiation with the reconfigured client verification depth after the HTTP request was read but before the HTTP response is sent.
The depth actually is the maximum number of intermediate certificate issuers,
i.e. the number of CA certificates which are max allowed to be followed while
verifying the client certificate. A depth of 0 means that self-signed client
certificates are accepted only, the default depth of 1 means the client
certificate can be self-signed or has to be signed by a CA which is directly
known to the server (i.e. the CA's certificate is under
SSLCACertificatePath
), etc.
SSLVerifyDepth 10
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