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Apache > HTTP Server > Documentation > Version 2.4 > Modules

Apache Module mod_ssl

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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

Summary

This module provides SSL v3 and TLS v1.x support for the Apache HTTP Server. SSL v2 is no longer supported.

This module relies on OpenSSL to provide the cryptography engine.

Further details, discussion, and examples are provided in the SSL documentation.

Directives

Topics

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Environment Variables

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
SSL_SRP_USER string SRP username
SSL_SRP_USERINFO string SRP user info
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 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
This will expand to the standard environment variable variablename.
HTTP:headername
This will expand to the value of the request header with name headername.
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Custom Log Formats

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.

Example

CustomLog logs/ssl_request_log "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
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Request Notes

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
This note is set to the value 1 if access was denied due to an SSLRequire or SSLRequireSSL directive.
ssl-secure-reneg
If 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.
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Authorization providers for use with Require

mod_ssl provides a few authentication providers for use with mod_authz_core's Require directive.

Require ssl

The ssl provider denies access if a connection is not encrypted with SSL. This is similar to the SSLRequireSSL directive.

Require ssl

Require ssl-verify-client

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
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SSLCACertificateFile 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.

Example

SSLCACertificateFile /usr/local/apache2/conf/ssl.crt/ca-bundle-client.crt
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SSLCACertificatePath Directive

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.

Example

SSLCACertificatePath /usr/local/apache2/conf/ssl.crt/
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SSLCADNRequestFile Directive

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.

Example

SSLCADNRequestFile /usr/local/apache2/conf/ca-names.crt
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SSLCADNRequestPath Directive

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.

Example

SSLCADNRequestPath /usr/local/apache2/conf/ca-names.crt/
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SSLCARevocationCheck Directive

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.

When set to 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.

Example

SSLCARevocationCheck chain
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SSLCARevocationFile Directive

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.

Example

SSLCARevocationFile /usr/local/apache2/conf/ssl.crl/ca-bundle-client.crl
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SSLCARevocationPath Directive

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.

Example

SSLCARevocationPath /usr/local/apache2/conf/ssl.crl/
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SSLCertificateChainFile Directive

Description:File of PEM-encoded Server CA Certificates
Syntax:SSLCertificateChainFile file-path
Context:server config, virtual host
Status:Extension
Module:mod_ssl

SSLCertificateChainFile is deprecated

SSLCertificateChainFile became obsolete with version 2.4.8, when SSLCertificateFile was extended to also load intermediate CA certificates from the server certificate file.

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.

Example

SSLCertificateChainFile /usr/local/apache2/conf/ssl.crt/ca.crt
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SSLCertificateFile Directive

Description:Server PEM-encoded X.509 certificate data file
Syntax:SSLCertificateFile file-path
Context:server config, virtual host
Status:Extension
Module:mod_ssl

This directive points to a file with certificate data in PEM format. At a minimum, the file must include an end-entity (leaf) certificate. Beginning with version 2.4.8, it may also include intermediate CA certificates, sorted from leaf to root, and obsoletes SSLCertificateChainFile.

Additional optional elements are DH parameters and/or an EC curve name for ephemeral keys, as generated by openssl dhparam and openssl ecparam, respectively (supported in version 2.4.7 or later) and finally, the end-entity certificate's private key. If the private key is encrypted, the pass phrase dialog is forced at startup time.

This directive can be used multiple times (referencing different filenames) to support multiple algorithms for server authentication - typically RSA, DSA, and ECC. The number of supported algorithms depends on the OpenSSL version being used for mod_ssl: with version 1.0.0 or later, openssl list-public-key-algorithms will output a list of supported algorithms.

When running with OpenSSL 1.0.2 or later, this directive allows to configure the intermediate CA chain on a per-certificate basis, which removes a limitation of the (now obsolete) SSLCertificateChainFile directive. DH and ECDH parameters, however, are only read from the first SSLCertificateFile directive, as they are applied independently of the authentication algorithm type.

DH parameter interoperability with primes > 1024 bit

Beginning with version 2.4.7, mod_ssl makes use of standardized DH parameters with prime lengths of 2048, 3072 and 4096 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.

Example

SSLCertificateFile /usr/local/apache2/conf/ssl.crt/server.crt
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SSLCertificateKeyFile Directive

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 (the private key may also be combined with the certificate in the SSLCertificateFile, but this practice is discouraged). If the contained private key is encrypted, the pass phrase dialog is forced at startup time.

The directive can be used multiple times (referencing different filenames) to support multiple algorithms for server authentication. For each SSLCertificateKeyFile directive, there must be a matching SSLCertificateFile directive.

Example

SSLCertificateKeyFile /usr/local/apache2/conf/ssl.key/server.key
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SSLCipherSuite Directive

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. SSLv2 ciphers are no longer supported. 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). The actually available ciphers and aliases depends on the used openssl version. Newer openssl versions may include additional ciphers.

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)
kSRP Secure Remote Password (SRP) key exchange
Authentication Algorithm:
aNULL No authentication
aRSA RSA authentication
aDSS DSS authentication
aDH Diffie-Hellman authentication
Cipher Encoding Algorithm:
eNULL No encryption
NULL alias for eNULL
AES AES encryption
DES DES encryption
3DES Triple-DES encryption
RC4 RC4 encryption
RC2 RC2 encryption
IDEA IDEA encryption
MAC Digest Algorithm:
MD5 MD5 hash function
SHA1 SHA1 hash function
SHA alias for SHA1
SHA256 SHA256 hash function
SHA384 SHA384 hash function
Aliases:
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
ECDH Elliptic Curve Diffie-Hellman key exchange
ADH all ciphers using Anonymous Diffie-Hellman key exchange
AECDH all ciphers using Anonymous Elliptic Curve Diffie-Hellman key exchange
SRP all ciphers using Secure Remote Password (SRP) key exchange
DSS all ciphers using DSS authentication
ECDSA all ciphers using ECDSA authentication
aNULL all ciphers using no authentication

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 (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:

aNULL, eNULL and EXP ciphers are always disabled

Beginning with version 2.4.7, 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 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.

Example

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
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
DES-CBC-SHA SSLv3 RSA RSA DES(56) SHA1
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
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
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SSLCompression Directive

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 2.4.3 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 version 2.4.3.

This directive allows to enable compression on the SSL level.

Enabling compression causes security issues in most setups (the so called CRIME attack).

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SSLCryptoDevice Directive

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".

Example

# For a Broadcom accelerator:
SSLCryptoDevice ubsec
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SSLEngine Directive

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.

Example

<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.

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SSLFIPS Directive

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.

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SSLHonorCipherOrder Directive

Description:Option to prefer the server's cipher preference order
Syntax:SSLHonorCipherOrder on|off
Default:SSLHonorCipherOrder off
Context:server config, virtual host
Status:Extension
Module:mod_ssl

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.

Example

SSLHonorCipherOrder on
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SSLInsecureRenegotiation Directive

Description:Option to enable support for insecure renegotiation
Syntax:SSLInsecureRenegotiation on|off
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.

Security warning

If this directive is enabled, SSL connections will be vulnerable to the Man-in-the-Middle prefix attack as described in CVE-2009-3555.

Example

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.

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SSLOCSPDefaultResponder Directive

Description:Set the default responder URI for OCSP validation
Syntax:SSLOCSDefaultResponder uri
Context:server config, virtual host
Status:Extension
Module:mod_ssl

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.

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SSLOCSPEnable Directive

Description:Enable OCSP validation of the client certificate chain
Syntax:SSLOCSPEnable on|off
Default:SSLOCSPEnable off
Context:server config, virtual host
Status:Extension
Module:mod_ssl

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.

Example

SSLVerifyClient on
SSLOCSPEnable on
SSLOCSPDefaultResponder http://responder.example.com:8888/responder
SSLOCSPOverrideResponder on
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SSLOCSPOverrideResponder Directive

Description:Force use of the default responder URI for OCSP validation
Syntax:SSLOCSPOverrideResponder on|off
Default:SSLOCSPOverrideResponder off
Context:server config, virtual host
Status:Extension
Module:mod_ssl

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.

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SSLOCSPResponderTimeout Directive

Description:Timeout for OCSP queries
Syntax:SSLOCSPResponderTimeout seconds
Default:SSLOCSPResponderTimeout 10
Context:server config, virtual host
Status:Extension
Module:mod_ssl

This option sets the timeout for queries to OCSP responders, when SSLOCSPEnable is turned on.

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SSLOCSPResponseMaxAge Directive

Description:Maximum allowable age for OCSP responses
Syntax:SSLOCSPResponseMaxAge seconds
Default:SSLOCSPResponseMaxAge -1
Context:server config, virtual host
Status:Extension
Module:mod_ssl

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.

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SSLOCSPResponseTimeSkew Directive

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

This option sets the maximum allowable time skew for OCSP responses (when checking their thisUpdate and nextUpdate fields).

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SSLOpenSSLConfCmd Directive

Description:Configure OpenSSL parameters through its SSL_CONF API
Syntax:SSLOpenSSLConfCmd command-name command-value
Context:server config, virtual host
Status:Extension
Module:mod_ssl
Compatibility:Available in httpd 2.4.8 and later, if using OpenSSL 1.0.2 or later

This directive exposes OpenSSL's SSL_CONF API to mod_ssl, allowing a flexible configuration of OpenSSL parameters without the need of implementing additional mod_ssl directives when new features are added to OpenSSL.

The set of available SSLOpenSSLConfCmd commands depends on the OpenSSL version being used for mod_ssl (at least version 1.0.2 is required). For a list of supported command names, see the section Supported configuration file commands in the SSL_CONF_cmd(3) manual page for OpenSSL.

Some of the SSLOpenSSLConfCmd commands can be used as an alternative to existing directives (such as SSLCipherSuite or SSLProtocol), though it should be noted that the syntax / allowable values for the parameters may sometimes differ.

Examples

SSLOpenSSLConfCmd Options -SessionTicket,ServerPreference
SSLOpenSSLConfCmd ECDHParameters brainpoolP256r1
SSLOpenSSLConfCmd ServerInfoFile /usr/local/apache2/conf/server-info.pem
SSLOpenSSLConfCmd Protocol "-ALL, TLSv1.2"
SSLOpenSSLConfCmd SignatureAlgorithms RSA+SHA384:ECDSA+SHA256
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SSLOptions Directive

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:

Example

SSLOptions +FakeBasicAuth -StrictRequire
<Files ~ "\.(cgi|shtml)$">
    SSLOptions +StdEnvVars -ExportCertData
<Files>
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SSLPassPhraseDialog Directive

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:

Example

SSLPassPhraseDialog exec:/usr/local/apache/sbin/pp-filter
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SSLProtocol Directive

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:

Example

SSLProtocol TLSv1
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SSLProxyCACertificateFile Directive

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.

Example

SSLProxyCACertificateFile /usr/local/apache2/conf/ssl.crt/ca-bundle-remote-server.crt
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SSLProxyCACertificatePath Directive

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.

Example

SSLProxyCACertificatePath /usr/local/apache2/conf/ssl.crt/
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SSLProxyCARevocationCheck Directive

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.

When set to 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.

Example

SSLProxyCARevocationCheck chain
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SSLProxyCARevocationFile Directive

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.

Example

SSLProxyCARevocationFile /usr/local/apache2/conf/ssl.crl/ca-bundle-remote-server.crl
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SSLProxyCARevocationPath Directive

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.

Example

SSLProxyCARevocationPath /usr/local/apache2/conf/ssl.crl/
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SSLProxyCheckPeerCN Directive

Description:Whether to check the remote server certificate's 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 certificate's CN field is compared against the hostname of the request URL. If both are not equal a 502 status code (Bad Gateway) is sent.

In 2.4.5 and later, SSLProxyCheckPeerCN has been superseded by SSLProxyCheckPeerName, and its setting is only taken into account when SSLProxyCheckPeerName off is specified at the same time.

Example

SSLProxyCheckPeerCN on
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SSLProxyCheckPeerExpire Directive

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.

Example

SSLProxyCheckPeerExpire on
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SSLProxyCheckPeerName Directive

Description:Configure host name checking for remote server certificates
Syntax:SSLProxyCheckPeerName on|off
Default:SSLProxyCheckPeerName on
Context:server config, virtual host
Status:Extension
Module:mod_ssl
Compatibility:Apache HTTP Server 2.4.5 and later

This directive configures host name checking for server certificates when mod_ssl is acting as an SSL client. The check will succeed if the host name from the request URI is found in either the subjectAltName extension or (one of) the CN attribute(s) in the certificate's subject. If the check fails, the SSL request is aborted and a 502 status code (Bad Gateway) is returned. The directive supersedes SSLProxyCheckPeerCN, which only checks for the expected host name in the first CN attribute.

Wildcard matching is supported in one specific flavor: subjectAltName entries of type dNSName or CN attributes starting with *. will match for any DNS name with the same number of labels and the same suffix (i.e., *.example.org matches for foo.example.org, but not for foo.bar.example.org).

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SSLProxyCipherSuite Directive

Description:Cipher Suite available for negotiation in SSL proxy handshake
Syntax:SSLProxyCipherSuite cipher-spec
Default:SSLProxyCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+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.

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SSLProxyEngine Directive

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.

Example

<VirtualHost _default_:443>
    SSLProxyEngine on
    #...
</VirtualHost>
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SSLProxyMachineCertificateChainFile Directive

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.

Security warning

If this directive is enabled, all of the certificates in the file will be trusted as if they were also in SSLProxyCACertificateFile.

Example

SSLProxyMachineCertificateChainFile /usr/local/apache2/conf/ssl.crt/proxyCA.pem
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SSLProxyMachineCertificateFile Directive

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

Example

SSLProxyMachineCertificateFile /usr/local/apache2/conf/ssl.crt/proxy.pem
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SSLProxyMachineCertificatePath Directive

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

Example

SSLProxyMachineCertificatePath /usr/local/apache2/conf/proxy.crt/
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SSLProxyProtocol Directive

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.

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SSLProxyVerify Directive

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.)

Example

SSLProxyVerify require
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SSLProxyVerifyDepth Directive

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.

Example

SSLProxyVerifyDepth 10
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SSLRandomSeed Directive

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:

Example

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
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SSLRenegBufferSize Directive

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.

Example

SSLRenegBufferSize 262144
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SSLRequire Directive

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

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.

Example

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).

Example

SSLRequire "foobar" in PeerExtList("1.2.3.4.5.6")

Notes on the PeerExtList function

  • 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.

See also

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SSLRequireSSL Directive

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.

Example

SSLRequireSSL
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SSLSessionCache Directive

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:

Examples

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.

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SSLSessionCacheTimeout 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.

Example

SSLSessionCacheTimeout 600
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SSLSessionTicketKeyFile Directive

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.

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SSLSRPUnknownUserSeed Directive

Description:SRP unknown user seed
Syntax:SSLSRPUnknownUserSeed secret-string
Context:server config, virtual host
Status:Extension
Module:mod_ssl
Compatibility:Available in httpd 2.4.4 and later, if using OpenSSL 1.0.1 or later

This directive sets the seed used to fake SRP user parameters for unknown users, to avoid leaking whether a given user exists. Specify a secret string. If this directive is not used, then Apache will return the UNKNOWN_PSK_IDENTITY alert to clients who specify an unknown username.

Example

SSLSRPUnknownUserSeed "secret"

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SSLSRPVerifierFile Directive

Description:Path to SRP verifier file
Syntax:SSLSRPVerifierFile file-path
Context:server config, virtual host
Status:Extension
Module:mod_ssl
Compatibility:Available in httpd 2.4.4 and later, if using OpenSSL 1.0.1 or later

This directive enables TLS-SRP and sets the path to the OpenSSL SRP (Secure Remote Password) verifier file containing TLS-SRP usernames, verifiers, salts, and group parameters.

Example

SSLSRPVerifierFile "/path/to/file.srpv"

The verifier file can be created with the openssl command line utility:

Creating the SRP verifier file

openssl srp -srpvfile passwd.srpv -userinfo "some info" -add username

The value given with the optional -userinfo parameter is avalable in the SSL_SRP_USERINFO request environment variable.

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SSLStaplingCache Directive

Description:Configures the OCSP stapling cache
Syntax:SSLStaplingCache type
Context:server config
Status:Extension
Module:mod_ssl
Compatibility:Available 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.

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SSLStaplingErrorCacheTimeout Directive

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 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.

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SSLStaplingFakeTryLater Directive

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 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.

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SSLStaplingForceURL Directive

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 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.

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SSLStaplingResponderTimeout Directive

Description:Timeout for OCSP stapling queries
Syntax:SSLStaplingResponderTimeout seconds
Default:SSLStaplingResponderTimeout 10
Context:server config, virtual host
Status:Extension
Module:mod_ssl
Compatibility:Available 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.

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SSLStaplingResponseMaxAge Directive

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 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.

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SSLStaplingResponseTimeSkew Directive

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 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.

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SSLStaplingReturnResponderErrors Directive

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 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.

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SSLStaplingStandardCacheTimeout Directive

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 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.

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SSLStrictSNIVHostCheck Directive

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.

Example

SSLStrictSNIVHostCheck on
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SSLUserName Directive

Description:Variable name to determine user name
Syntax:SSLUserName varname
Context:server config, directory, .htaccess
Override:AuthConfig
Status:Extension
Module:mod_ssl

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).

Example

SSLUserName SSL_CLIENT_S_DN_CN
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SSLUseStapling Directive

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 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 with the RFC 6066 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 implementation therefore only partially achieves the stated goal of "saving roundtrips and resources" - see also RFC 6961 (TLS Multiple Certificate Status Extension).

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SSLVerifyClient Directive

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.)

Example

SSLVerifyClient require
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SSLVerifyDepth Directive

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.

Example

SSLVerifyDepth 10

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Comments

Notice:
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