Apache HTTP Server Version 2.2
This document refers to a legacy release (2.2) of Apache httpd. The active release (2.4) is documented here. If you have not already upgraded, please follow this link for more information.
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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. It was contributed by Ralf S. Engeschall based on his mod_ssl project and originally derived from work by Ben Laurie.
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 (SSLv2, SSLv3, TLSv1, TLSv1.1, TLSv1.2) |
SSL_SESSION_ID | string | The hex-encoded SSL session id |
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 |
SSL_TLS_SNI | string | Contents of the SNI TLS extension (if supplied with ClientHello) |
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 an index to select a particular
attribute. For example, where the server certificate subject DN
included two OU fields, SSL_SERVER_S_DN_OU_0
and
SSL_SERVER_S_DN_OU_1
could be used to reference each.
SSL_CLIENT_V_REMAIN
is only available in version 2.1
and later.
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"
These formats even work without setting the StdEnvVars
option of the SSLOptions
directive.
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: | 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 |
Compatibility: | ECC support is available in Apache 2.2.26 and later |
This directive points to a file with certificate data in PEM format. At a minimum, the file must include an end-entity (leaf) certificate. The directive can be used up to three times (referencing different filenames) when an RSA, a DSA, and an ECC based server certificate is used in parallel.
Custom DH parameters and an EC curve name for ephemeral keys,
can be added to end of the first file configured using
SSLCertificateFile
.
This is supported in version 2.2.30 or later.
Such parameters can be generated using the commands
openssl dhparam
and openssl ecparam
.
The parameters can be added as-is to the end of the first
certificate file. Only the first file can be used for custom
parameters, as they are applied independently of the authentication
algorithm type.
Finally the the end-entity certificate's private key can also be
added to the certificate file instead of using a separate
SSLCertificateKeyFile
directive. This practice is highly discouraged. If the private
key is encrypted, the pass phrase dialog is forced at startup time.
Beginning with version 2.2.30, mod_ssl makes use of standardized DH parameters with prime lengths of 2048, 3072, 4096, 6144 and 8192 bits (from RFC 3526), and hands them out to clients based on the length of the certificate's RSA/DSA key. With Java-based clients in particular (Java 7 or earlier), this may lead to handshake failures - see this FAQ answer for working around such issues.
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 |
Compatibility: | ECC support is available in Apache 2.2.26 and later |
This directive points to the PEM-encoded private key file for the server. If the contained private key is encrypted, the pass phrase dialog is forced at startup time.
The directive can be used up to three times (referencing different filenames)
when an RSA, a DSA, and an ECC based private key is used in parallel. For each
SSLCertificateKeyFile
directive, there must be a matching SSLCertificateFile
directive.
The private key may also be combined with the certificate in the file given by
SSLCertificateFile
, but this practice
is highly discouraged.
SSLCertificateKeyFile /usr/local/apache2/conf/ssl.key/server.key
Description: | Cipher Suite available for negotiation in SSL handshake |
---|---|
Syntax: | SSLCipherSuite cipher-spec |
Default: | SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP |
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 a 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)aNULL
, eNULL
and EXP
ciphers are always disabledBeginning with version 2.2.30, null and export-grade
ciphers are always disabled, as mod_ssl unconditionally prepends any supplied
cipher suite string with !aNULL:!eNULL:!EXP:
at initialization.
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
is ``ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP
'' which
means the following: first, remove from consideration any ciphers that do not
authenticate, i.e. for SSL only the Anonymous Diffie-Hellman ciphers. Next,
use ciphers using RC4 and RSA. Next include the high, medium and then the low
security ciphers. Finally pull all SSLv2 and export ciphers to the
end of the list.
$ openssl ciphers -v 'ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP' NULL-SHA SSLv3 Kx=RSA Au=RSA Enc=None Mac=SHA1 NULL-MD5 SSLv3 Kx=RSA Au=RSA Enc=None Mac=MD5 EDH-RSA-DES-CBC3-SHA SSLv3 Kx=DH Au=RSA Enc=3DES(168) Mac=SHA1 ... ... ... ... ... EXP-RC4-MD5 SSLv3 Kx=RSA(512) Au=RSA Enc=RC4(40) Mac=MD5 export EXP-RC2-CBC-MD5 SSLv2 Kx=RSA(512) Au=RSA Enc=RC2(40) Mac=MD5 export EXP-RC4-MD5 SSLv2 Kx=RSA(512) Au=RSA Enc=RC4(40) Mac=MD5 export
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: | Enable compression on the SSL level |
---|---|
Syntax: | SSLCompression on|off |
Default: | SSLCompression off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.2.24 and later, if using OpenSSL 0.9.8 or later;
virtual host scope available if using OpenSSL 1.0.0 or later.
The default used to be on in versions 2.2.24 to 2.2.25. |
This directive allows to enable compression on the SSL level.
Enabling compression causes security issues in most setups (the so called CRIME attack).
Description: | Enable use of a cryptographic hardware accelerator |
---|---|
Syntax: | SSLCryptoDevice engine |
Default: | SSLCryptoDevice builtin |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in Apache 2.1 and later, if using -engine flavor of OpenSSL 0.9.6, or OpenSSL 0.9.7 or later |
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
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: | Semaphore for internal mutual exclusion of operations |
---|---|
Syntax: | SSLMutex type |
Default: | SSLMutex none |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This configures the SSL engine's semaphore (aka. lock) which is used for mutual
exclusion of operations which have to be done in a synchronized way between the
pre-forked Apache server processes. This directive can only be used in the
global server context because it's only useful to have one global mutex.
This directive is designed to closely match the
AcceptMutex
directive.
The following Mutex types are available:
none | no
This is the default where no Mutex is used at all. Use it at your own risk. But because currently the Mutex is mainly used for synchronizing write access to the SSL Session Cache you can live without it as long as you accept a sometimes garbled Session Cache. So it's not recommended to leave this the default. Instead configure a real Mutex.
posixsem
This is an elegant Mutex variant where a Posix Semaphore is used when possible. It is only available when the underlying platform and APR supports it.
sysvsem
This is a somewhat elegant Mutex variant where a SystemV IPC Semaphore is used when possible. It is possible to "leak" SysV semaphores if processes crash before the semaphore is removed. It is only available when the underlying platform and APR supports it.
sem
This directive tells the SSL Module to pick the "best" semaphore implementation available to it, choosing between Posix and SystemV IPC, in that order. It is only available when the underlying platform and APR supports at least one of the 2.
pthread
This directive tells the SSL Module to use Posix thread mutexes. It is only available if the underlying platform and APR supports it.
fcntl:/path/to/mutex
This is a portable Mutex variant where a physical (lock-)file and the fcntl()
function are used as the Mutex.
Always use a local disk filesystem for /path/to/mutex
and never a file
residing on a NFS- or AFS-filesystem. It is only available when the underlying platform
and APR supports it. Note: Internally, the Process ID (PID) of the
Apache parent process is automatically appended to
/path/to/mutex
to make it unique, so you don't have to worry
about conflicts yourself. Notice that this type of mutex is not available
under the Win32 environment. There you have to use the semaphore
mutex.
flock:/path/to/mutex
This is similar to the fcntl:/path/to/mutex
method with the
exception that the flock()
function is used to provide file
locking. It is only available when the underlying platform
and APR supports it.
file:/path/to/mutex
This directive tells the SSL Module to pick the "best" file locking implementation
available to it, choosing between fcntl
and flock
,
in that order. It is only available when the underlying platform and APR supports
at least one of the 2.
default | yes
This directive tells the SSL Module to pick the default locking implementation as determined by the platform and APR.
SSLMutex file:/usr/local/apache/logs/ssl_mutex
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...$Owx8s2/m9/gfkcRVXzgoE/
''.
StrictRequire
This forces forbidden access when SSLRequireSSL
or
SSLRequire
successfully decided that access should be
forbidden. Usually the default is that in the case where a ``Satisfy
any
'' directive is used, and other access restrictions are passed,
denial of access due to SSLRequireSSL
or
SSLRequire
is overridden (because that's how the Apache
Satisfy
mechanism should work.) But for strict access restriction
you can use SSLRequireSSL
and/or SSLRequire
in
combination with an ``SSLOptions +StrictRequire
''. Then an
additional ``Satisfy Any
'' has no chance once mod_ssl has
decided to deny access.
OptRenegotiate
This enables optimized SSL connection renegotiation handling when SSL directives are used in per-directory context. By default a strict scheme is enabled where every per-directory reconfiguration of SSL parameters causes a full SSL renegotiation handshake. When this option is used mod_ssl tries to avoid unnecessary handshakes by doing more granular (but still safe) parameter checks. Nevertheless these granular checks sometimes maybe not what the user expects, so enable this on a per-directory basis only, please.
SSLOptions +FakeBasicAuth -StrictRequire
<Files ~ "\.(cgi|shtml)$">
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
'', ``DSA
'', or ``ECC
''), 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 protocol flavors |
---|---|
Syntax: | SSLProtocol [+|-]protocol ... |
Default: | SSLProtocol 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. Clients then can only connect with one of the provided protocols.
The available (case-insensitive) protocols are:
SSLv2
This is the Secure Sockets Layer (SSL) protocol, version 2.0. It is the original SSL protocol as designed by Netscape Corporation. Though its use has been deprecated, because of weaknesses in the security of the protocol.
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 ``+SSLv2 +SSLv3 +TLSv1
'' or
- when using OpenSSL 1.0.1 and later -
``+SSLv2 +SSLv3 +TLSv1 +TLSv1.1 +TLSv1.2
'', respectively.
# enable SSLv3 and all available TLSv1 flavors, but not SSLv2
SSLProtocol All -SSLv2
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: | 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 off |
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 off |
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 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 |
Compatibility: | Available in Apache 2.2.23 and later |
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.
Note that even when certificate verification is enabled,
mod_ssl
does not check whether the
commonName
(hostname) attribute of the server certificate
matches the hostname used to connect to the server. In other words,
the proxy does not guarantee that the SSL connection to the backend
server is "secure" beyond the fact that the certificate is signed by
one of the CAs configured using the
SSLProxyCACertificatePath
and/or
SSLProxyCACertificateFile
directives.
In order to get this check done please have a look at
SSLProxyCheckPeerCN
and
SSLProxyCheckPeerExpire
directives which are off by
default.
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 |
Override: | AuthConfig |
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.
On some platforms like FreeBSD one can even control how the entropy is
actually generated, i.e. by which system interrupts. More details one can
find under rndcontrol(8) on those platforms. Alternatively, when
your system lacks such a random device, you can use a tool
like EGD
(Entropy Gathering Daemon) and run its client program with the
exec:/path/to/program/
variant (see below) or use
egd:/path/to/egd-socket
(see below).
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 |
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 implementation of SSLRequire
is not thread safe.
Using SSLRequire
inside .htaccess
files
on a threaded MPM may cause random crashes.
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" "OID(" word ")" | word "=~" regex | word "!~" regex wordlist ::= word | wordlist "," word word ::= digit | cstring | variable | function digit ::= [0-9]+ cstring ::= "..." variable ::= "%{" varname "}" function ::= funcname "(" funcargs ")"
while for varname
any variable from Table 3 can be used. Finally for
funcname
the following functions are available:
file(
filename)
This function takes one string argument and expands to the contents of the file. This is especially useful for matching this contents against a regular expression, etc.
Notice that expression is first parsed into an internal machine representation and then evaluated in a second step. Actually, in Global and Per-Server Class context expression is parsed at startup time and at runtime only the machine representation is executed. For Per-Directory context, specifically in a .htaccess context, this is different: here expression has to be parsed and immediately executed for every request.
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} >= 1 and %{TIME_WDAY} <= 5 \
and %{TIME_HOUR} >= 8 and %{TIME_HOUR} <= 20 ) \
or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/
The OID()
function expects to find zero or more instances
of the given OID in the client certificate, and compares the left-hand side
string against the value of matching OID attributes. Every matching OID is
checked, until a match is found.
Standard CGI/1.0 and Apache variables:
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 HTTP:headername SERVER_NAME TIME_MIN THE_REQUEST SERVER_PORT TIME_SEC REQUEST_METHOD SERVER_PROTOCOL TIME_WDAY REQUEST_SCHEME REMOTE_ADDR TIME REQUEST_URI REMOTE_USER ENV:variablename REQUEST_FILENAME
SSL-related variables:
HTTPS SSL_CLIENT_M_VERSION SSL_SERVER_M_VERSION SSL_CLIENT_M_SERIAL SSL_SERVER_M_SERIAL SSL_PROTOCOL SSL_CLIENT_V_START SSL_SERVER_V_START SSL_SESSION_ID SSL_CLIENT_V_END SSL_SERVER_V_END SSL_CIPHER SSL_CLIENT_S_DN SSL_SERVER_S_DN SSL_CIPHER_EXPORT SSL_CLIENT_S_DN_C SSL_SERVER_S_DN_C SSL_CIPHER_ALGKEYSIZE SSL_CLIENT_S_DN_ST SSL_SERVER_S_DN_ST SSL_CIPHER_USEKEYSIZE SSL_CLIENT_S_DN_L SSL_SERVER_S_DN_L SSL_VERSION_LIBRARY SSL_CLIENT_S_DN_O SSL_SERVER_S_DN_O SSL_VERSION_INTERFACE SSL_CLIENT_S_DN_OU SSL_SERVER_S_DN_OU SSL_CLIENT_S_DN_CN SSL_SERVER_S_DN_CN SSL_CLIENT_S_DN_T SSL_SERVER_S_DN_T SSL_CLIENT_S_DN_I SSL_SERVER_S_DN_I SSL_CLIENT_S_DN_G SSL_SERVER_S_DN_G SSL_CLIENT_S_DN_S SSL_SERVER_S_DN_S SSL_CLIENT_S_DN_D SSL_SERVER_S_DN_D SSL_CLIENT_S_DN_UID SSL_SERVER_S_DN_UID SSL_CLIENT_S_DN_Email SSL_SERVER_S_DN_Email SSL_CLIENT_I_DN SSL_SERVER_I_DN SSL_CLIENT_I_DN_C SSL_SERVER_I_DN_C SSL_CLIENT_I_DN_ST SSL_SERVER_I_DN_ST SSL_CLIENT_I_DN_L SSL_SERVER_I_DN_L SSL_CLIENT_I_DN_O SSL_SERVER_I_DN_O SSL_CLIENT_I_DN_OU SSL_SERVER_I_DN_OU SSL_CLIENT_I_DN_CN SSL_SERVER_I_DN_CN SSL_CLIENT_I_DN_T SSL_SERVER_I_DN_T SSL_CLIENT_I_DN_I SSL_SERVER_I_DN_I SSL_CLIENT_I_DN_G SSL_SERVER_I_DN_G SSL_CLIENT_I_DN_S SSL_SERVER_I_DN_S SSL_CLIENT_I_DN_D SSL_SERVER_I_DN_D SSL_CLIENT_I_DN_UID SSL_SERVER_I_DN_UID SSL_CLIENT_I_DN_Email SSL_SERVER_I_DN_Email SSL_CLIENT_A_SIG SSL_SERVER_A_SIG SSL_CLIENT_A_KEY SSL_SERVER_A_KEY SSL_CLIENT_CERT SSL_SERVER_CERT SSL_CLIENT_CERT_CHAIN_n SSL_CLIENT_VERIFY SSL_TLS_SNI
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 four 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.
shm:/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.
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.
SSLSessionCache dbm:/usr/local/apache/logs/ssl_gcache_data
SSLSessionCache shm:/usr/local/apache/logs/ssl_gcache_data(512000)
Description: | Number of seconds before an SSL session expires in the Session Cache |
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Syntax: | SSLSessionCacheTimeout seconds |
Default: | SSLSessionCacheTimeout 300 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Applies also to RFC 5077 TLS session resumption in Apache 2.2.28 and later |
This directive sets the timeout in seconds for the information stored in the global/inter-process SSL Session Cache, the OpenSSL internal memory cache and for sessions resumed by TLS session resumption (RFC 5077). 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 2.2.30 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. A new ticket key only gets used after restarting the web server. All existing session tickets become invalid after a restart.
The ticket key file contains sensitive keying material and should
be protected with file permissions similar to those used for
SSLCertificateKeyFile
.
Description: | Enable or disable use of TLS session tickets |
---|---|
Syntax: | SSLSessionTickets on|off |
Default: | SSLSessionTickets on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.2.30 and later, if using OpenSSL 0.9.8f or later. |
This directive allows to enable or disable the use of TLS session tickets (RFC 5077).
TLS session tickets are enabled by default. Using them without restarting the web server with an appropriate frequency (e.g. daily) compromises perfect forward secrecy.
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 non default name based virtual
host, non SNI clients are not allowed to access this particular virtual host.
If set to on
in the default name based virtual host, non SNI
clients are not allowed to access any name based virtual host belonging to
this IP / port combination.
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: | 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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