Apache HTTP Server Version 2.5
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 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 cryptographic engine.
Further details, discussion, and examples are provided in the SSL documentation.
This module can be configured to provide several items of SSL information
as additional environment variables to the SSI and CGI namespace. This
information is not provided by default for performance reasons. (See
SSLOptions
StdEnvVars, below.) The generated variables
are listed in the table below. For backward compatibility the information can
be made available under different names, too. Look in the Compatibility chapter for details on the
compatibility variables.
Variable Name: | Value Type: | Description: |
---|---|---|
HTTPS | flag | HTTPS is being used. |
SSL_PROTOCOL | string | The SSL protocol version (SSLv3, TLSv1, TLSv1.1, TLSv1.2) |
SSL_SESSION_ID | string | The hex-encoded SSL session id |
SSL_SESSION_RESUMED | string | Initial or Resumed SSL Session. Note: multiple requests may be served over the same (Initial or Resumed) SSL session if HTTP KeepAlive is in use |
SSL_SECURE_RENEG | string | true if secure renegotiation is supported, else false |
SSL_CIPHER | string | The cipher specification name |
SSL_CIPHER_EXPORT | string | true if cipher is an export cipher |
SSL_CIPHER_USEKEYSIZE | number | Number of cipher bits (actually used) |
SSL_CIPHER_ALGKEYSIZE | number | Number of cipher bits (possible) |
SSL_COMPRESS_METHOD | string | SSL compression method negotiated |
SSL_VERSION_INTERFACE | string | The mod_ssl program version |
SSL_VERSION_LIBRARY | string | The OpenSSL program version |
SSL_CLIENT_M_VERSION | string | The version of the client certificate |
SSL_CLIENT_M_SERIAL | string | The serial of the client certificate |
SSL_CLIENT_S_DN | string | Subject DN in client's certificate |
SSL_CLIENT_S_DN_ x509 | string | Component of client's Subject DN |
SSL_CLIENT_SAN_Email_ n | string | Client certificate's subjectAltName extension entries of type rfc822Name |
SSL_CLIENT_SAN_DNS_ n | string | Client certificate's subjectAltName extension entries of type dNSName |
SSL_CLIENT_SAN_OTHER_msUPN_ n | string | Client certificate's subjectAltName extension entries of type otherName, Microsoft User Principal Name form (OID 1.3.6.1.4.1.311.20.2.3) |
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_CERT_RFC4523_CEA | string | Serial number and issuer of the certificate. The format matches that of the CertificateExactAssertion in RFC4523 |
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_SAN_Email_ n | string | Server certificate's subjectAltName extension entries of type rfc822Name |
SSL_SERVER_SAN_DNS_ n | string | Server certificate's subjectAltName extension entries of type dNSName |
SSL_SERVER_SAN_OTHER_dnsSRV_ n | string | Server certificate's subjectAltName extension entries of type otherName, SRVName form (OID 1.3.6.1.5.5.7.8.7, RFC 4985) |
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 httpd 2.2.0 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.
In httpd 2.4.32 and later, an optional _RAW suffix may be
added to x509 in a DN component, to suppress conversion of
the attribute value to UTF-8. This must be placed after the index
suffix (if any). For example, SSL_SERVER_S_DN_OU_RAW
or
SSL_SERVER_S_DN_OU_0_RAW
could be used.
The format of the *_DN variables has changed in Apache HTTPD
2.3.11. See the LegacyDNStringFormat
option for
SSLOptions
for details.
SSL_CLIENT_V_REMAIN
is only available in version 2.1
and later.
A number of additional environment variables can also be used
in SSLRequire
expressions, or in custom log
formats:
HTTP_USER_AGENT PATH_INFO AUTH_TYPE HTTP_REFERER QUERY_STRING SERVER_SOFTWARE HTTP_COOKIE REMOTE_HOST API_VERSION HTTP_FORWARDED REMOTE_IDENT TIME_YEAR HTTP_HOST IS_SUBREQ TIME_MON HTTP_PROXY_CONNECTION DOCUMENT_ROOT TIME_DAY HTTP_ACCEPT SERVER_ADMIN TIME_HOUR THE_REQUEST SERVER_NAME TIME_MIN REQUEST_FILENAME SERVER_PORT TIME_SEC REQUEST_METHOD SERVER_PROTOCOL TIME_WDAY REQUEST_SCHEME REMOTE_ADDR TIME REQUEST_URI REMOTE_USER
In these contexts, two special formats can also be used:
ENV:variablename
HTTP:headername
When mod_ssl
is built into Apache or at least
loaded (under DSO situation) additional functions exist for the Custom Log Format of
mod_log_config
. First there is an
additional ``%{
varname}x
''
eXtension format function which can be used to expand any variables
provided by any module, especially those provided by mod_ssl which can
you find in the above table.
For backward compatibility there is additionally a special
``%{
name}c
'' cryptography format function
provided. Information about this function is provided in the Compatibility chapter.
CustomLog "logs/ssl_request_log" "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
These formats even work without setting the StdEnvVars
option of the SSLOptions
directive.
mod_ssl
sets "notes" for the request which can be
used in logging with the %{name}n
format
string in mod_log_config
.
The notes supported are as follows:
ssl-access-forbidden
1
if access was
denied due to an SSLRequire
or SSLRequireSSL
directive.ssl-secure-reneg
mod_ssl
is built against a version of
OpenSSL which supports the secure renegotiation extension, this note
is set to the value 1
if SSL is in used for the current
connection, and the client also supports the secure renegotiation
extension. If the client does not support the secure renegotiation
extension, the note is set to the value 0
.
If mod_ssl
is not built against a version of
OpenSSL which supports secure renegotiation, or if SSL is not in use
for the current connection, the note is not set.When mod_ssl
is built into Apache or at least
loaded (under DSO situation) any variables
provided by mod_ssl
can be used in expressions
for the ap_expr Expression Parser.
The variables can be referenced using the syntax
``%{
varname}
''. Starting
with version 2.4.18 one can also use the
mod_rewrite
style syntax
``%{SSL:
varname}
'' or
the function style syntax
``ssl(
varname)
''.
mod_headers
)Header set X-SSL-PROTOCOL "expr=%{SSL_PROTOCOL}" Header set X-SSL-CIPHER "expr=%{SSL:SSL_CIPHER}"
This feature even works without setting the StdEnvVars
option of the SSLOptions
directive.
mod_ssl
provides a few authentication providers for use
with mod_authz_core
's
Require
directive.
The ssl
provider denies access if a connection is not
encrypted with SSL. This is similar to the
SSLRequireSSL
directive.
Require ssl
The ssl
provider allows access if the user is
authenticated with a valid client certificate. This is only
useful if SSLVerifyClient optional
is in effect.
The following example grants access if the user is authenticated either with a client certificate or by username and password.
Require ssl-verify-client Require valid-user
Description: | File of concatenated PEM-encoded CA Certificates for Client Auth |
---|---|
Syntax: | SSLCACertificateFile file-path |
Context: | server config, virtual host |
Override: | AuthConfig |
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 |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
This directive sets the directory where you keep the Certificates of Certification Authorities (CAs) whose clients you deal with. These are used to verify the client certificate on Client Authentication.
The files in this directory have to be PEM-encoded and are accessed through
hash filenames. So usually you can't just place the Certificate files
there: you also have to create symbolic links named
hash-value.N
. And you should always make sure this directory
contains the appropriate symbolic links.
SSLCACertificatePath "/usr/local/apache2/conf/ssl.crt/"
Description: | File of concatenated PEM-encoded CA Certificates for defining acceptable CA names |
---|---|
Syntax: | SSLCADNRequestFile file-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
When a client certificate is requested by mod_ssl, a list of acceptable Certificate Authority names is sent to the client in the SSL handshake. These CA names can be used by the client to select an appropriate client certificate out of those it has available.
If neither of the directives SSLCADNRequestPath
or SSLCADNRequestFile
are given, then the
set of acceptable CA names sent to the client is the names of all the
CA certificates given by the SSLCACertificateFile
and SSLCACertificatePath
directives; in other
words, the names of the CAs which will actually be used to verify the
client certificate.
In some circumstances, it is useful to be able to send a set of
acceptable CA names which differs from the actual CAs used to verify
the client certificate - for example, if the client certificates are
signed by intermediate CAs. In such cases, SSLCADNRequestPath
and/or SSLCADNRequestFile
can be used; the
acceptable CA names are then taken from the complete set of
certificates in the directory and/or file specified by this pair of
directives.
SSLCADNRequestFile
must
specify an all-in-one file containing a concatenation of
PEM-encoded CA certificates.
SSLCADNRequestFile "/usr/local/apache2/conf/ca-names.crt"
Description: | Directory of PEM-encoded CA Certificates for defining acceptable CA names |
---|---|
Syntax: | SSLCADNRequestPath directory-path |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This optional directive can be used to specify the set of
acceptable CA names which will be sent to the client when a
client certificate is requested. See the SSLCADNRequestFile
directive for more
details.
The files in this directory have to be PEM-encoded and are accessed
through hash filenames. So usually you can't just place the
Certificate files there: you also have to create symbolic links named
hash-value.N
. And you should always make sure
this directory contains the appropriate symbolic links.
SSLCADNRequestPath "/usr/local/apache2/conf/ca-names.crt/"
Description: | Enable CRL-based revocation checking |
---|---|
Syntax: | SSLCARevocationCheck chain|leaf|none [flags ...] |
Default: | SSLCARevocationCheck none |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Optional flags available in httpd 2.4.21 or later |
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.
The available flags are:
no_crl_for_cert_ok
Prior to version 2.3.15, CRL checking in mod_ssl also succeeded when
no CRL(s) for the checked certificate(s) were found in any of the locations
configured with SSLCARevocationFile
or SSLCARevocationPath
.
With the introduction of SSLCARevocationFile
,
the behavior has been changed: by default with chain
or
leaf
, CRLs must be present for the
validation to succeed - otherwise it will fail with an
"unable to get certificate CRL"
error.
The flag no_crl_for_cert_ok
allows to restore
previous behaviour.
SSLCARevocationCheck chain
SSLCARevocationCheck chain no_crl_for_cert_ok
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 |
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.
SSLCertificateChainFile "/usr/local/apache2/conf/ssl.crt/ca.crt"
Description: | Server PEM-encoded X.509 certificate data file or token identifier |
---|---|
Syntax: | SSLCertificateFile file-path|certid |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | certid available in 2.5.1 and later. |
This directive points to a file with certificate data in PEM format, or the certificate identifier through a configured cryptographic token.
If using a PEM file, at minimum, the file must include an end-entity (leaf) certificate.
The 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, see also the note below about limitations
of OpenSSL versions prior to 1.0.2 and the ways to work around them.
The files may also include intermediate CA certificates, sorted from
leaf to root. This is supported with version 2.4.8 and later,
and obsoletes SSLCertificateChainFile
.
When running with OpenSSL 1.0.2 or later, this allows
to configure the intermediate CA chain on a per-certificate basis.
Custom DH parameters and an EC curve name for ephemeral keys,
can also be added to end of the first file configured using
SSLCertificateFile
.
This is supported in version 2.4.7 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 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 it is used,
the certificate files using such an embedded key must be configured
after the certificates using a separate key file. If the private
key is encrypted, the pass phrase dialog is forced at startup time.
As an alternative to storing certificates and private keys in
files, a certificate identifier can be used to identify a certificate
stored in a token. Currently, only PKCS#11 URIs are
recognized as certificate identifiers, and can be used in conjunction
with the OpenSSL pkcs11
engine. If SSLCertificateKeyFile
is omitted, the
certificate and private key can be loaded through the single
identifier specified with SSLCertificateFile
.
Beginning with version 2.4.7, mod_ssl makes use of standardized DH parameters with prime lengths of 2048, 3072 and 4096 bits and with additional prime lengths of 6144 and 8192 bits beginning with version 2.4.10 (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.
When using multiple certificates to support different authentication algorithms
(like RSA, DSA, but mainly ECC) and OpenSSL prior to 1.0.2, it is recommended
to either use custom DH parameters (preferably) by adding them to the
first certificate file (as described above), or to order the
SSLCertificateFile
directives such that RSA/DSA
certificates are placed after the ECC one.
This is due to a limitation in older versions of OpenSSL which don't let the Apache HTTP Server determine the currently selected certificate at handshake time (when the DH parameters must be sent to the peer) but instead always provide the last configured certificate. Consequently, the server may select default DH parameters based on the length of the wrong certificate's key (ECC keys are much smaller than RSA/DSA ones and their length is not relevant for selecting DH primes).
Since custom DH parameters always take precedence over the default ones, this issue can be avoided by creating and configuring them (as described above), thus using a custom/suitable length.
# Example using a PEM-encoded file. SSLCertificateFile "/usr/local/apache2/conf/ssl.crt/server.crt" # Example use of a certificate and private key from a PKCS#11 token: SSLCertificateFile "pkcs11:token=My%20Token%20Name;id=45"
Description: | Server PEM-encoded private key file |
---|---|
Syntax: | SSLCertificateKeyFile file-path|keyid |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | keyid available in 2.5.1 and later. |
This directive points to the PEM-encoded private key file for the server, or the key ID through a configured cryptographic token. 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.
The private key may also be combined with the certificate in the file given by
SSLCertificateFile
, but this practice
is highly discouraged. If it is used, the certificate files using such
an embedded key must be configured after the certificates using a separate
key file.
As an alternative to storing private keys in files, a key
identifier can be used to identify a private key stored in a
token. Currently, only PKCS#11 URIs are recognized as private key
identifiers, and can be used in conjunction with the OpenSSL
pkcs11
engine.
# To use a private key from a PEM-encoded file: SSLCertificateKeyFile "/usr/local/apache2/conf/ssl.key/server.key" # To use a private key from a PKCS#11 token: SSLCertificateKeyFile "pkcs11:token=My%20Token%20Name;id=45"
Description: | Cipher Suite available for negotiation in SSL handshake |
---|---|
Syntax: | SSLCipherSuite [protocol] 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. The optional protocol specifier can configure the Cipher Suite for a specific SSL version. Possible values include "SSL" for all SSL Protocols up to and including TLSv1.2.
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.
If the SSL library supports TLSv1.3 (OpenSSL 1.1.1 and later), the protocol specifier "TLSv1.3" can be used to configure the cipher suites for that protocol. Since TLSv1.3 does not offer renegotiations, specifying ciphers for it in a directory context is not allowed.
For a list of TLSv1.3 cipher names, see the OpenSSL documentation.
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:
+
: 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 2.4.7, null and export-grade
ciphers are always disabled, as mod_ssl unconditionally adds
!aNULL:!eNULL:!EXP
to any cipher string 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.
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 |
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).
Description: | Enable use of a cryptographic hardware accelerator |
---|---|
Syntax: | SSLCryptoDevice engine |
Default: | SSLCryptoDevice builtin |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This directive enables use of a cryptographic hardware accelerator board to offload some of the SSL processing overhead. This directive can only be used if the SSL toolkit is built with "engine" support; OpenSSL 0.9.7 and later releases have "engine" support by default, the separate "-engine" releases of OpenSSL 0.9.6 must be used.
To discover which engine names are supported, run the command
"openssl engine
".
# For a Broadcom accelerator: SSLCryptoDevice ubsec
Description: | SSL Engine Operation Switch |
---|---|
Syntax: | SSLEngine on|off|optional |
Default: | SSLEngine off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive toggles the usage of the SSL/TLS Protocol Engine. This
is should be used inside a <VirtualHost>
section to enable SSL/TLS for a
that virtual host. By default the SSL/TLS Protocol Engine is
disabled for both the main server and all configured virtual hosts.
<VirtualHost _default_:443> SSLEngine on #... </VirtualHost>
SSLEngine
can be set to optional
:
this enables support for
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 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.
SSLHonorCipherOrder on
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 if using OpenSSL 0.9.8m or later |
As originally specified, all versions of the SSL and TLS protocols (up to and including TLS/1.2) were vulnerable to a Man-in-the-Middle attack (CVE-2009-3555) during a renegotiation. This vulnerability allowed an attacker to "prefix" a chosen plaintext to the HTTP request as seen by the web server. A protocol extension was developed which fixed this vulnerability if supported by both client and server.
If mod_ssl
is linked against OpenSSL version 0.9.8m
or later, by default renegotiation is only supported with
clients supporting the new protocol extension. If this directive is
enabled, renegotiation will be allowed with old (unpatched) clients,
albeit insecurely.
If this directive is enabled, SSL connections will be vulnerable to the Man-in-the-Middle prefix attack as described in CVE-2009-3555.
SSLInsecureRenegotiation on
The SSL_SECURE_RENEG
environment variable can be used
from an SSI or CGI script to determine whether secure renegotiation is
supported for a given SSL connection.
Description: | Set the default responder URI for OCSP validation |
---|---|
Syntax: | SSLOCSPDefaultResponder 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.
Description: | Enable OCSP validation of the client certificate chain |
---|---|
Syntax: | SSLOCSPEnable on|leaf|off |
Default: | SSLOCSPEnable off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Mode leaf available in httpd 2.4.34 and later |
This option enables OCSP validation of the client certificate chain. If this option is enabled, certificates in the client's certificate chain will be validated against an OCSP responder after normal verification (including CRL checks) have taken place. In mode 'leaf', only the client certificate itself will be validated.
The OCSP responder used is either extracted from the certificate
itself, or derived by configuration; see the
SSLOCSPDefaultResponder
and
SSLOCSPOverrideResponder
directives.
SSLVerifyClient on SSLOCSPEnable on SSLOCSPDefaultResponder "http://responder.example.com:8888/responder" SSLOCSPOverrideResponder on
Description: | skip the OCSP responder certificates verification |
---|---|
Syntax: | SSLOCSPNoverify on|off |
Default: | SSLOCSPNoverify off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.4.26 and later, if using OpenSSL 0.9.7 or later |
Skip the OCSP responder certificates verification, mostly useful when testing an OCSP server.
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.
Description: | Proxy URL to use for OCSP requests |
---|---|
Syntax: | SSLOCSPProxyURL url |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.4.19 and later |
This option allows to set the URL of a HTTP proxy that should be used for all queries to OCSP responders.
Description: | Set of trusted PEM encoded OCSP responder certificates |
---|---|
Syntax: | SSLOCSPResponderCertificateFile file |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.4.26 and later, if using OpenSSL 0.9.7 or later |
This supplies a list of trusted OCSP responder certificates to be used during OCSP responder certificate validation. The supplied certificates are implicitly trusted without any further validation. This is typically used where the OCSP responder certificate is self signed or omitted from the OCSP response.
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.
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.
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).
Description: | Use a nonce within OCSP queries |
---|---|
Syntax: | SSLOCSPUseRequestNonce on|off |
Default: | SSLOCSPUseRequestNonce on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.4.10 and later |
This option determines whether queries to OCSP responders should contain
a nonce or not. By default, a query nonce is always used and checked against
the response's one. When the responder does not use nonces (e.g. Microsoft OCSP
Responder), this option should be turned off
.
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.
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
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
). The optional SSLUserName
directive can be used to
specify which part of the certificate Subject is embedded in the username.
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/
''.
Note that the AuthBasicFake
directive within mod_auth_basic
can be used as a more
general mechanism for faking basic authentication, giving control over the
structure of both the username and password.
The usernames used for FakeBasicAuth
must not
include any non-ASCII characters, ASCII escape characters (such
a newline), or a colon. If a colon is found, a 403 Forbidden
error will be generated with httpd 2.5.1 and later.
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 may not be what the user expects, so enable this on a per-directory basis only, please.
LegacyDNStringFormat
This option influences how values of the
SSL_{CLIENT,SERVER}_{I,S}_DN
variables are formatted. Since
version 2.3.11, Apache HTTPD uses a RFC 2253 compatible format by
default. This uses commas as delimiters between the attributes, allows the
use of non-ASCII characters (which are converted to UTF8), escapes
various special characters with backslashes, and sorts the attributes
with the "C" attribute last.
If LegacyDNStringFormat
is set, the old format will be
used which sorts the "C" attribute first, uses slashes as separators, and
does not handle non-ASCII and special characters in any consistent way.
SSLOptions +FakeBasicAuth -StrictRequire <Files ~ "\.(cgi|shtml)$"> SSLOptions +StdEnvVars -ExportCertData </Files>
Description: | Type of pass phrase dialog for encrypted private keys |
---|---|
Syntax: | SSLPassPhraseDialog type |
Default: | SSLPassPhraseDialog builtin |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
When Apache starts up it has to read the various Certificate (see
SSLCertificateFile
) and
Private Key (see SSLCertificateKeyFile
) files of the
SSL-enabled virtual servers. Because for security reasons the Private
Key files are usually encrypted, mod_ssl needs to query the
administrator for a Pass Phrase in order to decrypt those files. This
query can be done in two ways which can be configured by
type:
builtin
This is the default where an interactive terminal dialog occurs at startup time just before Apache detaches from the terminal. Here the administrator has to manually enter the Pass Phrase for each encrypted Private Key file. Because a lot of SSL-enabled virtual hosts can be configured, the following reuse-scheme is used to minimize the dialog: When a Private Key file is encrypted, all known Pass Phrases (at the beginning there are none, of course) are tried. If one of those known Pass Phrases succeeds no dialog pops up for this particular Private Key file. If none succeeded, another Pass Phrase is queried on the terminal and remembered for the next round (where it perhaps can be reused).
This scheme allows mod_ssl to be maximally flexible (because for N encrypted Private Key files you can use N different Pass Phrases - but then you have to enter all of them, of course) while minimizing the terminal dialog (i.e. when you use a single Pass Phrase for all N Private Key files this Pass Phrase is queried only once).
|/path/to/program [args...]
This mode allows an external program to be used which acts as a
pipe to a particular input device; the program is sent the standard
prompt text used for the builtin
mode on
stdin
, and is expected to write password strings on
stdout
. If several passwords are needed (or an
incorrect password is entered), additional prompt text will be
written subsequent to the first password being returned, and more
passwords must then be written back.
exec:/path/to/program
Here an external program is configured which is called at startup for each
encrypted Private Key file. It is called with one argument, a string of the
form ``servername:portnumber:index
'' (with index
being a zero-based sequence number), which indicates for which server,
TCP port and certificate number 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: | Apply a SSLPolicy by name |
---|---|
Syntax: | SSLPolicy name |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available in httpd 2.5.0 and later |
This directive applies the set of SSL* directives defined under 'name' as the base settings in the current context. Apache comes with the following pre-defined policies from Mozilla, the makers of the Firefox browser (see here for a detailed description by them.):
modern
: recommended when your server is accessible on the open Internet. Works with all modern browsers, but old devices might be unable to connect.intermediate
: the fallback if you need to support old (but not very old) clients.old
: when you need to give Windows XP/Internet Explorer 6 access. The last resort.SSLPolicy applies configuration settings in place, meaning previous values are overwritten. Configuration directives following an SSLPolicy may overwrite it.
You can check the detailed description of all defined policies via the command line:
httpd -t -D DUMP_SSL_POLICIES
Description: | Configure usable SSL/TLS protocol versions |
---|---|
Syntax: | SSLProtocol [+|-]protocol ... |
Default: | SSLProtocol all -SSLv3 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive can be used to control which versions of the SSL/TLS protocol will be accepted in new connections.
The available (case-insensitive) protocols are:
SSLv3
This is the Secure Sockets Layer (SSL) protocol, version 3.0, from the Netscape Corporation. It is the successor to SSLv2 and the predecessor to TLSv1, but is deprecated in RFC 7568.
TLSv1
This is the Transport Layer Security (TLS) protocol, version 1.0. It is the successor to SSLv3 and is defined in RFC 2246. It is supported by nearly every client.
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.
TLSv1.3
(when using OpenSSL 1.1.1 and later)
A new version of the TLS protocol, as defined in RFC 8446.
all
This is a shortcut for ``+SSLv3 +TLSv1
'' or
- when using OpenSSL 1.0.1 and later -
``+SSLv3 +TLSv1 +TLSv1.1 +TLSv1.2
'', respectively
(except for OpenSSL versions compiled with the ``no-ssl3'' configuration
option, where all
does not include +SSLv3
).
SSLProtocol TLSv1
SSLProtocol
for name-based virtual hosts
Before OpenSSL 1.1.1, even though the Server Name Indication (SNI) allowed to
determine the targeted virtual host early in the TLS handshake, it was not
possible to switch the TLS protocol version of the connection at this point,
and thus the SSLProtocol
negotiated was always based off
the one of the base virtual host (first virtual host declared on the
listening IP:port
of the connection).
Beginning with Apache HTTP server version 2.5.1, when built/linked against
OpenSSL 1.1.1 or later, and when the SNI is provided by the client in the TLS
handshake, the SSLProtocol
of each (name-based) virtual
host can and will be honored.
For compatibility with previous versions, if no
SSLProtocol
is configured in a name-based virtual host,
the one from the base virtual host still applies, unless
SSLProtocol
is configured globally in which case the
global value applies (this latter exception is more sensible than compatible,
though).
Description: | File of concatenated PEM-encoded CA Certificates for Remote Server Auth |
---|---|
Syntax: | SSLProxyCACertificateFile file-path |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
This directive sets the directory where you keep the Certificates of Certification Authorities (CAs) whose remote servers you deal with. These are used to verify the remote server certificate on Remote Server Authentication.
The files in this directory have to be PEM-encoded and are accessed through
hash filenames. So usually you can't just place the Certificate files
there: you also have to create symbolic links named
hash-value.N
. And you should always make sure this directory
contains the appropriate symbolic links.
SSLProxyCACertificatePath "/usr/local/apache2/conf/ssl.crt/"
Description: | Enable CRL-based revocation checking for Remote Server Auth |
---|---|
Syntax: | SSLProxyCARevocationCheck chain|leaf|none |
Default: | SSLProxyCARevocationCheck none |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
Enables certificate revocation list (CRL) checking for the
remote servers you deal with. At least one of
SSLProxyCARevocationFile
or SSLProxyCARevocationPath
must be
configured. When set to chain
(recommended setting),
CRL checks are applied to all certificates in the chain, while setting it to
leaf
limits the checks to the end-entity cert.
chain
or leaf
,
CRLs must be available for successful validation
Prior to version 2.3.15, CRL checking in mod_ssl also succeeded when
no CRL(s) were found in any of the locations configured with
SSLProxyCARevocationFile
or SSLProxyCARevocationPath
.
With the introduction of this directive, the behavior has been changed:
when checking is enabled, CRLs must be present for the validation
to succeed - otherwise it will fail with an
"unable to get certificate CRL"
error.
SSLProxyCARevocationCheck chain
Description: | File of concatenated PEM-encoded CA CRLs for Remote Server Auth |
---|---|
Syntax: | SSLProxyCARevocationFile file-path |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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 certificate's CN field |
---|---|
Syntax: | SSLProxyCheckPeerCN on|off |
Default: | SSLProxyCheckPeerCN on |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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. SSLProxyCheckPeerCN
is
superseded by SSLProxyCheckPeerName
in release 2.4.5 and later.
In all releases 2.4.5 through 2.4.20, setting
SSLProxyCheckPeerName off
was sufficient to enable this behavior
(as the SSLProxyCheckPeerCN
default was on
.) In
these releases, both directives must be set to off
to completely
avoid remote server certificate name validation. Many users reported this
to be very confusing.
As of release 2.4.21, all configurations which enable either one of the
SSLProxyCheckPeerName
or SSLProxyCheckPeerCN
options
will use the new SSLProxyCheckPeerName
behavior, and all configurations which disable either one of the
SSLProxyCheckPeerName
or SSLProxyCheckPeerCN
options
will suppress all remote server certificate name validation. Only the following
configuration will trigger the legacy certificate CN comparison in 2.4.21 and
later releases;
SSLProxyCheckPeerCN on SSLProxyCheckPeerName off
Description: | Whether to check if remote server certificate is expired |
---|---|
Syntax: | SSLProxyCheckPeerExpire on|off |
Default: | SSLProxyCheckPeerExpire on |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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: | Configure host name checking for remote server certificates |
---|---|
Syntax: | SSLProxyCheckPeerName on|off |
Default: | SSLProxyCheckPeerName on |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Apache HTTP Server 2.4.5 and later The proxy section context is allowed in httpd 2.4.30 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 matches one of the CN attribute(s) of the certificate's subject, or matches the subjectAltName extension. If the check fails, the SSL request is aborted and a 502 status code (Bad Gateway) is returned.
Wildcard matching is supported for specific cases: an subjectAltName entry
of type dNSName, or CN attributes starting with *.
will match
with any host name of the same number of name elements and the same suffix.
E.g. *.example.org
will match foo.example.org
,
but will not match foo.bar.example.org
, because the number of
elements in the respective host names differs.
This feature was introduced in 2.4.5 and superseded the behavior of the
SSLProxyCheckPeerCN
directive, which
only tested the exact value in the first CN attribute against the host name.
However, many users were confused by the behavior of using these directives
individually, so the mutual behavior of SSLProxyCheckPeerName
and SSLProxyCheckPeerCN
directives were improved in release
2.4.21. See the SSLProxyCheckPeerCN
directive description for the original behavior and details of these
improvements.
Description: | Cipher Suite available for negotiation in SSL proxy handshake |
---|---|
Syntax: | SSLProxyCipherSuite [protocol] cipher-spec |
Default: | SSLProxyCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+EXP |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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 ProxyRequests
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, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 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, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
This directive sets the directory where you keep the certificates and keys used for authentication of the proxy server to remote servers.
mod_ssl will attempt to load every file inside the specified directory, but will ignore any sub-directories. Each file should contain a PEM-encoded certificate and matching private key.
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 -SSLv3 |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
When a proxy is configured to forward requests to a remote SSL server, this directive can be used to configure certificate verification of the remote server.
The following levels are available for level:
In practice only levels none and require are really interesting, because level optional doesn't work with all servers and level optional_no_ca is actually against the idea of authentication (but can be used to establish SSL test pages, etc.)
SSLProxyVerify require
Description: | Maximum depth of CA Certificates in Remote Server Certificate verification |
---|---|
Syntax: | SSLProxyVerifyDepth number |
Default: | SSLProxyVerifyDepth 1 |
Context: | server config, virtual host, proxy section |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | The proxy section context is allowed in httpd 2.4.30 and later |
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 a randomly chosen 128 bytes extract of the stack. The drawback is that this is not really a strong source and at startup time (where the scoreboard is still not available) this source just produces a few bytes of entropy. So you should always, at least for the startup, use an additional seeding source.
file:/path/to/source
This variant uses an external file /path/to/source
as the
source for seeding the PRNG. When bytes is specified, only the
first bytes number of bytes of the file form the entropy (and
bytes is given to /path/to/source
as the first
argument). When bytes is not specified the whole file forms the
entropy (and 0
is given to /path/to/source
as
the first argument). Use this especially at startup time, for instance
with an available /dev/random
and/or
/dev/urandom
devices (which usually exist on modern Unix
derivatives like FreeBSD and Linux).
But be careful: Usually /dev/random
provides only as
much entropy data as it actually has, i.e. when you request 512 bytes of
entropy, but the device currently has only 100 bytes available two things
can happen: On some platforms you receive only the 100 bytes while on
other platforms the read blocks until enough bytes are available (which
can take a long time). Here using an existing /dev/urandom
is
better, because it never blocks and actually gives the amount of requested
data. The drawback is just that the quality of the received data may not
be the best.
exec:/path/to/program
This variant uses an external executable
/path/to/program
as the source for seeding the
PRNG. When bytes is specified, only the first
bytes number of bytes of its stdout
contents
form the entropy. When bytes is not specified, the
entirety of the data produced on stdout
form the
entropy. Use this only at startup time when you need a very strong
seeding with the help of an external program (for instance as in
the example above with the truerand
utility you can
find in the mod_ssl distribution which is based on the AT&T
truerand library). Using this in the connection context
slows down the server too dramatically, of course. So usually you
should avoid using external programs in that context.
egd:/path/to/egd-socket
(Unix only)
This variant uses the Unix domain socket of the external Entropy Gathering Daemon (EGD) (see http://www.lothar.com/tech /crypto/) to seed the PRNG. Use this if no random device exists on your platform.
SSLRandomSeed startup builtin SSLRandomSeed startup "file:/dev/random" SSLRandomSeed startup "file:/dev/urandom" 1024 SSLRandomSeed startup "exec:/usr/local/bin/truerand" 16 SSLRandomSeed connect builtin SSLRandomSeed connect "file:/dev/random" SSLRandomSeed connect "file:/dev/urandom" 1024
Description: | Set the size for the SSL renegotiation buffer |
---|---|
Syntax: | SSLRenegBufferSize bytes |
Default: | SSLRenegBufferSize 131072 |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
If an SSL renegotiation is required in per-location context, for
example, any use of SSLVerifyClient
in a Directory or
Location block, then mod_ssl
must buffer any HTTP
request body into memory until the new SSL handshake can be performed.
This directive can be used to set the amount of memory that will be
used for this buffer.
Note that in many configurations, the client sending the request body will be untrusted so a denial of service attack by consumption of memory must be considered when changing this configuration setting.
SSLRenegBufferSize 262144
Description: | Allow access only when an arbitrarily complex boolean expression is true |
---|---|
Syntax: | SSLRequire expression |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
SSLRequire
is deprecated and should in general be replaced
by Require expr. The so called
ap_expr syntax of Require expr
is
a superset of the syntax of SSLRequire
, with the following
exception:
In SSLRequire
, the comparison operators <
,
<=
, ... are completely equivalent to the operators
lt
, le
, ... and work in a somewhat peculiar way that
first compares the length of two strings and then the lexical order.
On the other hand, ap_expr has two sets of
comparison operators: The operators <
,
<=
, ... do lexical string comparison, while the operators
-lt
, -le
, ... do integer comparison.
For the latter, there are also aliases without the leading dashes:
lt
, le
, ...
This directive specifies a general access requirement which has to be fulfilled in order to allow access. It is a very powerful directive because the requirement specification is an arbitrarily complex boolean expression containing any number of access checks.
The expression must match the following syntax (given as a BNF grammar notation):
expr ::= "true" | "false" | "!" expr | expr "&&" expr | expr "||" expr | "(" expr ")" | comp comp ::= word "==" word | word "eq" word | word "!=" word | word "ne" word | word "<" word | word "lt" word | word "<=" word | word "le" word | word ">" word | word "gt" word | word ">=" word | word "ge" word | word "in" "{" wordlist "}" | word "in" "PeerExtList(" word ")" | word "=~" regex | word "!~" regex wordlist ::= word | wordlist "," word word ::= digit | cstring | variable | function digit ::= [0-9]+ cstring ::= "..." variable ::= "%{" varname "}" function ::= funcname "(" funcargs ")"
For varname
any of the variables described in Environment Variables can be used. For
funcname
the available functions are listed in
the ap_expr documentation.
The expression is parsed into an internal machine representation when the configuration is loaded, and then evaluated during request processing. In .htaccess context, the expression is both parsed and executed each time the .htaccess file is encountered during request processing.
SSLRequire ( %{SSL_CIPHER} !~ m/^(EXP|NULL)-/ \ and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \ and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \ and %{TIME_WDAY} -ge 1 and %{TIME_WDAY} -le 5 \ and %{TIME_HOUR} -ge 8 and %{TIME_HOUR} -le 20 ) \ or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/
The PeerExtList(object-ID)
function expects
to find zero or more instances of the X.509 certificate extension
identified by the given object ID (OID) in the client certificate.
The expression evaluates to true if the left-hand side string matches
exactly against the value of an extension identified with this OID.
(If multiple extensions with the same OID are present, at least one
extension must match).
SSLRequire "foobar" in PeerExtList("1.2.3.4.5.6")
The object ID can be specified either as a descriptive
name recognized by the SSL library, such as "nsComment"
,
or as a numeric OID, such as "1.2.3.4.5.6"
.
Expressions with types known to the SSL library are rendered to a string before comparison. For an extension with a type not recognized by the SSL library, mod_ssl will parse the value if it is one of the primitive ASN.1 types UTF8String, IA5String, VisibleString, or BMPString. For an extension of one of these types, the string value will be converted to UTF-8 if necessary, then compared against the left-hand-side expression.
Description: | Deny access when SSL is not used for the HTTP request |
---|---|
Syntax: | SSLRequireSSL |
Context: | directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
This directive forbids access unless HTTP over SSL (i.e. HTTPS) is enabled for the current connection. This is very handy inside the SSL-enabled virtual host or directories for defending against configuration errors that expose stuff that should be protected. When this directive is present all requests are denied which are not using SSL.
SSLRequireSSL
Description: | Type of the global/inter-process SSL Session Cache |
---|---|
Syntax: | SSLSessionCache type |
Default: | SSLSessionCache none |
Context: | server config |
Status: | Extension |
Module: | mod_ssl |
This configures the storage type of the global/inter-process SSL Session Cache. This cache is an optional facility which speeds up parallel request processing. For requests to the same server process (via HTTP keep-alive), OpenSSL already caches the SSL session information locally. But because modern clients request inlined images and other data via parallel requests (usually up to four parallel requests are common) those requests are served by different pre-forked server processes. Here an inter-process cache helps to avoid unnecessary session handshakes.
The following five storage types are currently supported:
none
This disables the global/inter-process Session Cache. This will incur a noticeable speed penalty and may cause problems if using certain browsers, particularly if client certificates are enabled. This setting is not recommended.
nonenotnull
This disables any global/inter-process Session Cache. However it does force OpenSSL to send a non-null session ID to accommodate buggy clients that require one.
dbm:/path/to/datafile
This makes use of a DBM hashfile on the local disk to
synchronize the local OpenSSL memory caches of the server
processes. This session cache may suffer reliability issues under
high load. To use this, ensure that
mod_socache_dbm
is loaded.
shmcb:/path/to/datafile
[(
size)
]
This makes use of a high-performance cyclic buffer
(approx. size bytes in size) inside a shared memory
segment in RAM (established via /path/to/datafile
) to
synchronize the local OpenSSL memory caches of the server
processes. This is the recommended session cache. To use this,
ensure that mod_socache_shmcb
is loaded.
dc:UNIX:/path/to/socket
This makes use of the distcache distributed session
caching libraries. The argument should specify the location of
the server or proxy to be used using the distcache address syntax;
for example, UNIX:/path/to/socket
specifies a UNIX
domain socket (typically a local dc_client proxy);
IP:server.example.com:9001
specifies an IP
address. To use this, ensure that
mod_socache_dc
is loaded.
SSLSessionCache "dbm:/usr/local/apache/logs/ssl_gcache_data" SSLSessionCache "shmcb:/usr/local/apache/logs/ssl_gcache_data(512000)"
The ssl-cache
mutex is used to serialize access to
the session cache to prevent corruption. This mutex can be configured
using the Mutex
directive.
Description: | Number of seconds before an SSL session expires in the Session Cache |
---|---|
Syntax: | SSLSessionCacheTimeout seconds |
Default: | SSLSessionCacheTimeout 300 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Applies also to RFC 5077 TLS session resumption in Apache 2.4.10 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 2.4.0 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. 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 2.4.11 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: | 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.
SSLSRPUnknownUserSeed "secret"
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.
SSLSRPVerifierFile "/path/to/file.srpv"
The verifier file can be created with the openssl
command line
utility:
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.
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
.
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
.
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.
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. One potential use is when a proxy is used for retrieving OCSP queries.
Description: | Timeout for OCSP stapling queries |
---|---|
Syntax: | SSLStaplingResponderTimeout seconds |
Default: | SSLStaplingResponderTimeout 10 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available if using OpenSSL 0.9.8h or later |
This option sets the timeout for queries to OCSP responders when
SSLUseStapling
is enabled
and mod_ssl is querying a responder for OCSP stapling purposes.
Description: | Maximum allowable age for OCSP stapling responses |
---|---|
Syntax: | SSLStaplingResponseMaxAge seconds |
Default: | SSLStaplingResponseMaxAge -1 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available if using OpenSSL 0.9.8h or later |
This option sets the maximum allowable age ("freshness") when
considering OCSP responses for stapling purposes, i.e. when
SSLUseStapling
is turned on.
The default value (-1
) does not enforce a maximum age,
which means that OCSP responses are considered valid as long as their
nextUpdate
field is in the future.
Description: | Maximum allowable time skew for OCSP stapling response validation |
---|---|
Syntax: | SSLStaplingResponseTimeSkew seconds |
Default: | SSLStaplingResponseTimeSkew 300 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available if using OpenSSL 0.9.8h or later |
This option sets the maximum allowable time skew when mod_ssl checks the
thisUpdate
and nextUpdate
fields of OCSP responses
which get included in the TLS handshake (OCSP stapling). Only applicable
if SSLUseStapling
is turned on.
Description: | Pass stapling related OCSP errors on to client |
---|---|
Syntax: | SSLStaplingReturnResponderErrors on|off |
Default: | SSLStaplingReturnResponderErrors on |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available if using OpenSSL 0.9.8h or later |
When enabled, mod_ssl will pass responses from unsuccessful
stapling related OCSP queries (such as responses with an overall status
other than "successful", responses with a certificate status other than
"good", expired responses etc.) on to the client.
If set to off
, only responses indicating a certificate status
of "good" will be included in the TLS handshake.
Description: | Number of seconds before expiring responses in the OCSP stapling cache |
---|---|
Syntax: | SSLStaplingStandardCacheTimeout seconds |
Default: | SSLStaplingStandardCacheTimeout 3600 |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available if using OpenSSL 0.9.8h or later |
Sets the timeout in seconds before responses in the OCSP stapling cache
(configured through SSLStaplingCache
)
will expire. This directive applies to valid responses, while
SSLStaplingErrorCacheTimeout
is
used for controlling the timeout for invalid/unavailable responses.
Description: | Whether to allow non-SNI clients to access a name-based virtual host. |
---|---|
Syntax: | SSLStrictSNIVHostCheck on|off |
Default: | SSLStrictSNIVHostCheck off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
This directive sets whether a non-SNI client is allowed to access a name-based
virtual host. If set to on
in the default name-based virtual
host, clients that are SNI unaware will not be allowed to access any
virtual host, belonging to this particular IP / port combination.
If set to on
in any other virtual host, SNI unaware clients
are not allowed to access this particular virtual host.
This option is only available if httpd was compiled against an SNI capable version of OpenSSL.
SSLStrictSNIVHostCheck on
Description: | Variable name to determine user name |
---|---|
Syntax: | SSLUserName varname |
Context: | server config, directory, .htaccess |
Override: | AuthConfig |
Status: | Extension |
Module: | mod_ssl |
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.
When the FakeBasicAuth
option is enabled, this directive
instead controls the value of the username embedded within the basic
authentication header (see SSLOptions).
SSLUserName SSL_CLIENT_S_DN_CN
Description: | Enable stapling of OCSP responses in the TLS handshake |
---|---|
Syntax: | SSLUseStapling on|off |
Default: | SSLUseStapling off |
Context: | server config, virtual host |
Status: | Extension |
Module: | mod_ssl |
Compatibility: | Available 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).
When OCSP stapling is enabled, the ssl-stapling
mutex is used
to control access to the OCSP stapling cache in order to prevent corruption,
and the sss-stapling-refresh
mutex is used to control refreshes
of OCSP responses. These mutexes can be configured using the
Mutex
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:
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