Apache SSL Directives

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　　Link:http://httpd.apache.org/docs/2.0/mod/mod_ssl.html
　　
　　

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Apache Module mod_ssl

　　Available Languages:  en
  Description:Strong cryptography using the Secure Sockets Layer (SSL) and Transport Layer Security (TLS) protocols Status:Extension Module Identifier:ssl_module Source File:mod_ssl.c Summary
　　This module provides SSL v2/v3 and TLS v1 support for the Apache HTTP Server.  It was contributed by Ralf S. Engeschall based on his mod_ssl project and originally derived from work by Ben Laurie.
　　This module relies on OpenSSL to provide the cryptography engine.
　　Further details, discussion, and examples are provided in the SSL documentation.
  
Directives

• SSLCACertificateFile
  
• SSLCACertificatePath
  
• SSLCARevocationFile
  
• SSLCARevocationPath
  
• SSLCertificateChainFile
  
• SSLCertificateFile
  
• SSLCertificateKeyFile
  
• SSLCipherSuite
  
• SSLEngine
  
• SSLMutex
  
• SSLOptions
  
• SSLPassPhraseDialog
  
• SSLProtocol
  
• SSLProxyCACertificateFile
  
• SSLProxyCACertificatePath
  
• SSLProxyCARevocationFile
  
• SSLProxyCARevocationPath
  
• SSLProxyCipherSuite
  
• SSLProxyEngine
  
• SSLProxyMachineCertificateFile
  
• SSLProxyMachineCertificatePath
  
• SSLProxyProtocol
  
• SSLProxyVerify
  
• SSLProxyVerifyDepth
  
• SSLRandomSeed
  
• SSLRequire
  
• SSLRequireSSL
  
• SSLSessionCache
  
• SSLSessionCacheTimeout
  
• SSLUserName
  
• SSLVerifyClient
  
• SSLVerifyDepth
  

Topics

• Environment Variables
  
• Custom Log Formats
  

Environment Variables
　　This module provides a lot of SSL information as additional environment variables to the SSI and CGI namespace. The generated variables are listed in the table below. For backward compatibility the information can be made available under different names, too. Look in the Compatibility chapter for details on the compatibility variables.
    Variable Name:  Value Type:  Description:  HTTPS                         flag      HTTPS is being used. SSL_PROTOCOL                  string    The SSL protocol version (SSLv2, SSLv3, TLSv1) SSL_SESSION_ID                string    The hex-encoded SSL session id SSL_CIPHER                    string    The cipher specification name SSL_CIPHER_EXPORT             string    true if cipher is an export cipher SSL_CIPHER_USEKEYSIZE         number    Number of cipher bits (actually used) SSL_CIPHER_ALGKEYSIZE         number    Number of cipher bits (possible) SSL_VERSION_INTERFACE         string    The mod_ssl program version SSL_VERSION_LIBRARY           string    The OpenSSL program version SSL_CLIENT_M_VERSION          string    The version of the client certificate SSL_CLIENT_M_SERIAL           string    The serial of the client certificate SSL_CLIENT_S_DN               string    Subject DN in client's certificate SSL_CLIENT_S_DN_x509 string    Component of client's Subject DN SSL_CLIENT_I_DN               string    Issuer DN of client's certificate SSL_CLIENT_I_DN_x509 string    Component of client's Issuer DN SSL_CLIENT_V_START            string    Validity of client's certificate (start time) SSL_CLIENT_V_END              string    Validity of client's certificate (end time) SSL_CLIENT_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_CHAINn string    PEM-encoded certificates in client certificate chain SSL_CLIENT_VERIFY             string    NONE, SUCCESS, GENEROUS or FAILED:reason SSL_SERVER_M_VERSION          string    The version of the server certificate SSL_SERVER_M_SERIAL           string    The serial of the server certificate SSL_SERVER_S_DN               string    Subject DN in server's certificate SSL_SERVER_S_DN_x509 string    Component of server's Subject DN SSL_SERVER_I_DN               string    Issuer DN of server's certificate SSL_SERVER_I_DN_x509 string    Component of server's Issuer DN SSL_SERVER_V_START            string    Validity of server's certificate (start time) SSL_SERVER_V_END              string    Validity of server's certificate (end time) SSL_SERVER_A_SIG              string    Algorithm used for the signature of server's certificate SSL_SERVER_A_KEY              string    Algorithm used for the public key of server's certificate SSL_SERVER_CERT               string    PEM-encoded server certificate　　[ where x509 is a component of a X.509 DN:   C,ST,L,O,OU,CN,T,I,G,S,D,UID,Email ]


Custom Log Formats
　　When mod_ssl is built into Apache or at least loaded (under DSO situation) additional functions exist for the Custom Log Format of  mod_log_config. First there is an additional ``%{varname}x'' eXtension format function which can be used to expand any variables provided by any module, especially those provided by mod_ssl which can you find in the above table.
　　For backward compatibility there is additionally a special ``%{name}c'' cryptography format function provided. Information about this function is provided in the Compatibility chapter.
　　Example:

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

SSLCACertificateFile Directive
Description:File of concatenated PEM-encoded CA Certificates  for Client Auth Syntax:SSLCACertificateFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the all-in-one file where you can assemble the Certificates of Certification Authorities (CA) whose clients you deal with. These are used for Client Authentication. Such a file is simply the concatenation of the various PEM-encoded Certificate files, in order of preference. This can be used alternatively and/or additionally to  SSLCACertificatePath.

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

SSLCACertificatePath Directive
Description:Directory of PEM-encoded CA Certificates for  Client Auth Syntax:SSLCACertificatePath directory-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the directory where you keep the Certificates of Certification Authorities (CAs) whose clients you deal with. These are used to verify the client certificate on Client Authentication.
　　The files in this directory have to be PEM-encoded and are accessed through hash filenames. So usually you can't just place the Certificate files there: you also have to create symbolic links named hash-value.N. And you should always make sure this directory contains the appropriate symbolic links.

Example
　　 SSLCACertificatePath /usr/local/apache2/conf/ssl.crt/
   

SSLCARevocationFile Directive
Description:File of concatenated PEM-encoded CA CRLs for  Client Auth Syntax:SSLCARevocationFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the all-in-one file where you can assemble the Certificate Revocation Lists (CRL) of Certification Authorities (CA) whose clients you deal with. These are used for Client Authentication.  Such a file is simply the concatenation of the various PEM-encoded CRL files, in order of preference. This can be used alternatively and/or additionally to SSLCARevocationPath.

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

SSLCARevocationPath Directive
Description:Directory of PEM-encoded CA CRLs for  Client Auth Syntax:SSLCARevocationPath directory-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the directory where you keep the Certificate Revocation Lists (CRL) of Certification Authorities (CAs) whose clients you deal with. These are used to revoke the client certificate on Client Authentication.
　　The files in this directory have to be PEM-encoded and are accessed through hash filenames. So usually you have not only to place the CRL files there. Additionally you have to create symbolic links named hash-value.rN. And you should always make sure this directory contains the appropriate symbolic links.

Example
　　 SSLCARevocationPath /usr/local/apache2/conf/ssl.crl/
   

SSLCertificateChainFile Directive
Description:File of PEM-encoded Server CA Certificates Syntax:SSLCertificateChainFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the optional all-in-one file where you can assemble the certificates of Certification Authorities (CA) which form the certificate chain of the server certificate. This starts with the issuing CA certificate of 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. That's usually not one expect.
　　But be careful: Providing the certificate chain works only if you are using a single (either RSA or DSA) based server certificate. If you are using a coupled RSA+DSA certificate pair, this will work only if actually both certificates use the same certificate chain. Else the browsers will be confused in this situation.

Example
　　 SSLCertificateChainFile /usr/local/apache2/conf/ssl.crt/ca.crt
   

SSLCertificateFile Directive
Description:Server PEM-encoded X.509 Certificate file Syntax:SSLCertificateFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive points to the PEM-encoded Certificate file for the server and optionally also to the corresponding RSA or DSA Private Key file for it (contained in the same file). If the contained Private Key is encrypted the Pass Phrase dialog is forced at startup time. This directive can be used up to two times (referencing different filenames) when both a RSA and a DSA based server certificate is used in parallel.

Example
　　 SSLCertificateFile /usr/local/apache2/conf/ssl.crt/server.crt
   

SSLCertificateKeyFile Directive
Description:Server PEM-encoded Private Key file Syntax:SSLCertificateKeyFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive points to the PEM-encoded Private Key file for the server. If the Private Key is not combined with the Certificate in the SSLCertificateFile, use this additional directive to point to the file with the stand-alone Private Key. When SSLCertificateFile is used and the file contains both the Certificate and the Private Key this directive need not be used. But we strongly discourage this practice.  Instead we recommend you to separate the Certificate and the Private Key. If the contained Private Key is encrypted, the Pass Phrase dialog is forced at startup time. This directive can be used up to two times (referencing different filenames) when both a RSA and a DSA based private key is used in parallel.

Example
　　 SSLCertificateKeyFile /usr/local/apache2/conf/ssl.key/server.key
   

SSLCipherSuite Directive
Description:Cipher Suite available for negotiation in SSL  handshake Syntax:SSLCipherSuite cipher-spec Default:SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP Context:server config, virtual host, directory, .htaccess Override:AuthConfig Status:Extension Module:mod_ssl　　This complex directive uses a colon-separated cipher-spec string consisting of OpenSSL cipher specifications to configure the Cipher Suite the client is permitted to negotiate in the SSL handshake phase. Notice that this directive can be used both in per-server and per-directory context. In per-server context it applies to the standard SSL handshake when a connection is established. In per-directory context it forces a SSL renegotation with the reconfigured Cipher Suite after the HTTP request was read but before the HTTP response is sent.
　　An SSL cipher specification in cipher-spec is composed of 4 major attributes plus a few extra minor ones:

• Key Exchange Algorithm:
       RSA or Diffie-Hellman variants.
  
• Authentication Algorithm:
       RSA, Diffie-Hellman, DSS or none.
  
• Cipher/Encryption Algorithm:
       DES, Triple-DES, RC4, RC2, IDEA or none.
  
• MAC Digest Algorithm:
       MD5, SHA or SHA1.
  

　　An SSL cipher can also be an export cipher and is either a SSLv2 or SSLv3/TLSv1 cipher (here TLSv1 is equivalent to SSLv3). To specify which ciphers to use, one can either specify all the Ciphers, one at a time, or use aliases to specify the preference and order for the ciphers (see Table 1).
  Tag Description Key Exchange Algorithm: kRSA   RSA key exchange kDHr   Diffie-Hellman key exchange with RSA key kDHd   Diffie-Hellman key exchange with DSA key kEDH   Ephemeral (temp.key) Diffie-Hellman key exchange (no cert)    Authentication Algorithm: aNULL  No authentication aRSA   RSA authentication aDSS   DSS authentication  aDH    Diffie-Hellman authentication Cipher Encoding Algorithm: eNULL  No encoding          DES    DES encoding         3DES   Triple-DES encoding  RC4    RC4 encoding        RC2    RC2 encoding        IDEA   IDEA encoding        MAC Digest Algorithm: MD5    MD5 hash function SHA1   SHA1 hash function SHA    SHA hash function  Aliases: SSLv2  all SSL version 2.0 ciphers SSLv3  all SSL version 3.0 ciphers  TLSv1  all TLS version 1.0 ciphers  EXP    all export ciphers   EXPORT40 all 40-bit export ciphers only   EXPORT56 all 56-bit export ciphers only   LOW    all low strength ciphers (no export, single DES) MEDIUM all ciphers with 128 bit encryption  HIGH   all ciphers using Triple-DES      RSA    all ciphers using RSA key exchange  DH     all ciphers using Diffie-Hellman key exchange  EDH    all ciphers using Ephemeral Diffie-Hellman key exchange  ADH    all ciphers using Anonymous Diffie-Hellman key exchange  DSS    all ciphers using DSS authentication  NULL   all ciphers using no encryption 　　Now where this becomes interesting is that these can be put together to specify the order and ciphers you wish to use. To speed this up there are also aliases (SSLv2, SSLv3, TLSv1, EXP, LOW, MEDIUM, HIGH) for certain groups of ciphers. These tags can be joined together with prefixes to form the cipher-spec. Available prefixes are:

• none: add cipher to list
  
• +: add ciphers to list and pull them to current location in list
  
• -: remove cipher from list (can be added later again)
  
• !: kill cipher from list completely (can not be added later again)
  

　　A simpler way to look at all of this is to use the ``openssl ciphers -v'' command which provides a nice way to successively create the correct cipher-spec string. The default cipher-spec string is ``ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP'' which means the following: first, remove from consideration any ciphers that do not authenticate, i.e. for SSL only the Anonymous Diffie-Hellman ciphers. Next, use ciphers using RC4 and RSA. Next include the high, medium and then the low security ciphers. Finally pull all SSLv2 and export ciphers to the end of the list.

$ openssl ciphers -v 'ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP'
NULL-SHA                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
NULL-MD5                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5
EDH-RSA-DES-CBC3-SHA    SSLv3 Kx=DH       Au=RSA  Enc=3DES(168) Mac=SHA1
...                     ...               ...     ...           ...
EXP-RC4-MD5             SSLv3 Kx=RSA(512) Au=RSA  Enc=RC4(40)   Mac=MD5  export
EXP-RC2-CBC-MD5         SSLv2 Kx=RSA(512) Au=RSA  Enc=RC2(40)   Mac=MD5  export
EXP-RC4-MD5             SSLv2 Kx=RSA(512) Au=RSA  Enc=RC4(40)   Mac=MD5  export
　　The complete list of particular RSA & DH ciphers for SSL is given in Table 2.

Example
　　 SSLCipherSuite RSA:!EXP:!NULL:+HIGH:+MEDIUM:-LOW
Cipher-Tag Protocol Key Ex. Auth. Enc. MAC Type  RSA Ciphers: DES-CBC3-SHA SSLv3 RSA RSA 3DES(168) SHA1  
DES-CBC3-MD5 SSLv2 RSA RSA 3DES(168) MD5  
IDEA-CBC-SHA SSLv3 RSA RSA IDEA(128) SHA1  
RC4-SHA SSLv3 RSA RSA RC4(128) SHA1  
RC4-MD5 SSLv3 RSA RSA RC4(128) MD5  
IDEA-CBC-MD5 SSLv2 RSA RSA IDEA(128) MD5  
RC2-CBC-MD5 SSLv2 RSA RSA RC2(128) MD5  
RC4-MD5 SSLv2 RSA RSA RC4(128) MD5  
DES-CBC-SHA SSLv3 RSA RSA DES(56) SHA1  
RC4-64-MD5 SSLv2 RSA RSA RC4(64) MD5  
DES-CBC-MD5 SSLv2 RSA RSA DES(56) MD5  
EXP-DES-CBC-SHA SSLv3 RSA(512) RSA DES(40) SHA1  export  EXP-RC2-CBC-MD5 SSLv3 RSA(512) RSA RC2(40) MD5   export  EXP-RC4-MD5 SSLv3 RSA(512) RSA RC4(40) MD5   export  EXP-RC2-CBC-MD5 SSLv2 RSA(512) RSA RC2(40) MD5   export  EXP-RC4-MD5 SSLv2 RSA(512) RSA RC4(40) MD5   export  NULL-SHA SSLv3 RSA RSA None SHA1  
NULL-MD5 SSLv3 RSA RSA None MD5  
Diffie-Hellman Ciphers: ADH-DES-CBC3-SHA SSLv3 DH None 3DES(168) SHA1  
ADH-DES-CBC-SHA SSLv3 DH None DES(56) SHA1  
ADH-RC4-MD5 SSLv3 DH None RC4(128) MD5  
EDH-RSA-DES-CBC3-SHA SSLv3 DH RSA 3DES(168) SHA1  
EDH-DSS-DES-CBC3-SHA SSLv3 DH DSS 3DES(168) SHA1  
EDH-RSA-DES-CBC-SHA SSLv3 DH RSA DES(56) SHA1  
EDH-DSS-DES-CBC-SHA SSLv3 DH DSS DES(56) SHA1  
EXP-EDH-RSA-DES-CBC-SHA SSLv3 DH(512) RSA DES(40) SHA1  export  EXP-EDH-DSS-DES-CBC-SHA SSLv3 DH(512) DSS DES(40) SHA1  export  EXP-ADH-DES-CBC-SHA SSLv3 DH(512) None DES(40) SHA1  export  EXP-ADH-RC4-MD5 SSLv3 DH(512) None RC4(40) MD5   export   

SSLEngine Directive
Description:SSL Engine Operation Switch Syntax:SSLEngine on|off 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 usually used inside a  section to enable SSL/TLS for a particular virtual host. By default the SSL/TLS Protocol Engine is disabled for both the main server and all configured virtual hosts.

Example
　　
SSLEngine on
...
  
   

SSLMutex Directive
Description:Semaphore for internal mutual exclusion of  operations Syntax:SSLMutex type Default:SSLMutex none Context:server config Status:Extension Module:mod_ssl　　This configures the SSL engine's semaphore (aka. lock) which is used for mutual exclusion of operations which have to be done in a synchronized way between the pre-forked Apache server processes. This directive can only be used in the global server context because it's only useful to have one global mutex. This directive is designed to closely match the AcceptMutex directive
　　The following Mutex types are available:

• none | no　　This is the default where no Mutex is used at all. Use it at your own     risk. But because currently the Mutex is mainly used for synchronizing     write access to the SSL Session Cache you can live without it as long     as you accept a sometimes garbled Session Cache. So it's not recommended     to leave this the default. Instead configure a real Mutex.
  
• posixsem　　This is an elegant Mutex variant where a Posix Semaphore is used when possible.     It is only available when the underlying platform     and APR supports it.
  
• sysvsem　　This is a somewhat elegant Mutex variant where a SystemV IPC Semaphore is used when     possible. It is possible to "leak" SysV semaphores if processes crash before     the semaphore is removed. It is only available when the underlying platform     and APR supports it.
  
• sem　　This directive tells the SSL Module to pick the "best" semaphore implementation     available to it, choosing between Posix and SystemV IPC, in that order. It is only     available when the underlying platform and APR supports at least one of the 2.
  
• pthread　　This directive tells the SSL Module to use Posix thread mutexes. It is only available     if the underlying platform and APR supports it.
  
• fcntl:/path/to/mutex　　This is a portable Mutex variant where a physical (lock-)file and the fcntl()     fucntion are used as the Mutex.     Always use a local disk filesystem for /path/to/mutex and never a file     residing on a NFS- or AFS-filesystem. It is only available when the underlying platform     and APR supports it. Note: Internally, the Process ID (PID) of the     Apache parent process is automatically appended to     /path/to/mutex to make it unique, so you don't have to worry     about conflicts yourself. Notice that this type of mutex is not available     under the Win32 environment. There you have to use the semaphore     mutex.
  
• flock:/path/to/mutex　　This is similar to the fcntl:/path/to/mutex method with the     exception that the flock() function is used to provide file     locking. It is only available when the underlying platform     and APR supports it.
  
• file:/path/to/mutex　　This directive tells the SSL Module to pick the "best" file locking implementation     available to it, choosing between fcntl and flock,     in that order. It is only available when the underlying platform and APR supports     at least one of the 2.
  
• default | yes　　This directive tells the SSL Module to pick the default locking implementation     as determined by the platform and APR.
  

Example
　　 SSLMutex file:/usr/local/apache/logs/ssl_mutex
   

SSLOptions Directive
Description:Configure various SSL engine run-time options Syntax:SSLOptions [+|-]option ... Context:server config, virtual host, directory, .htaccess Override:Options Status:Extension Module:mod_ssl　　This directive can be used to control various run-time options on a per-directory basis. Normally, if multiple SSLOptions could apply to a directory, then the most specific one is taken completely; the options are not merged. However if all the options on the SSLOptions directive are preceded by a plus (+) or minus (-) symbol, the options are merged. Any options preceded by a + are added to the options currently in force, and any options preceded by a - are removed from the options currently in force.
　　The available options are:

• 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.
  
• CompatEnvVars　　When this option is enabled, additional CGI/SSI environment variables are     created for backward compatibility to other Apache SSL solutions. Look in     the Compatibility chapter for details     on the particular variables generated.
  
• ExportCertData　　When this option is enabled, additional CGI/SSI environment variables are     created: SSL_SERVER_CERT, SSL_CLIENT_CERT and     SSL_CLIENT_CERT_CHAINn (with n = 0,1,2,..).     These contain the PEM-encoded X.509 Certificates of server and client for     the current HTTPS connection and can be used by CGI scripts for deeper     Certificate checking. Additionally all other certificates of the client     certificate chain are provided, too. This bloats up the environment a     little bit which is why you have to use this option to enable it on     demand.
  
• FakeBasicAuth　　When this option is enabled, the Subject Distinguished Name (DN) of the     Client X509 Certificate is translated into a HTTP Basic Authorization     username. This means that the standard Apache authentication methods can     be used for access control. The user name is just the Subject of the     Client's X509 Certificate (can be determined by running OpenSSL's     openssl x509 command: openssl x509 -noout -subject -in     certificate.crt). Note that no password is     obtained from the user. Every entry in the user file needs this password:     ``xxj31ZMTZzkVA'', which is the DES-encrypted version of the     word `password''. Those who live under MD5-based encryption     (for instance under FreeBSD or BSD/OS, etc.) should use the following MD5     hash of the same word: ``$1$OXLyS...$Owx8s2/m9/gfkcRVXzgoE/''.
  
• StrictRequire　　This forces forbidden access when SSLRequireSSL or     SSLRequire successfully decided that access should be     forbidden. Usually the default is that in the case where a ``Satisfy     any'' directive is used, and other access restrictions are passed,     denial of access due to SSLRequireSSL or     SSLRequire is overridden (because that's how the Apache     Satisfy mechanism should work.) But for strict access restriction     you can use SSLRequireSSL and/or SSLRequire in     combination with an ``SSLOptions +StrictRequire''. Then an     additional ``Satisfy Any'' has no chance once mod_ssl has     decided to deny access.
  
• OptRenegotiate　　This enables optimized SSL connection renegotiation handling when SSL     directives are used in per-directory context. By default a strict     scheme is enabled where every per-directory reconfiguration of     SSL parameters causes a full SSL renegotiation handshake. When this     option is used mod_ssl tries to avoid unnecessary handshakes by doing more     granular (but still safe) parameter checks. Nevertheless these granular     checks sometimes maybe not what the user expects, so enable this on a     per-directory basis only, please.
  

Example
　　 SSLOptions +FakeBasicAuth -StrictRequire

     SSLOptions +StdEnvVars +CompatEnvVars -ExportCertData
  
   

SSLPassPhraseDialog Directive
Description:Type of pass phrase dialog for encrypted private  keys Syntax:SSLPassPhraseDialog type Default:SSLPassPhraseDialog builtin Context:server config Status:Extension Module:mod_ssl　　When Apache starts up it has to read the various Certificate (see SSLCertificateFile) and Private Key (see SSLCertificateKeyFile) files of the SSL-enabled virtual servers. Because for security reasons the Private Key files are usually encrypted, mod_ssl needs to query the administrator for a Pass Phrase in order to decrypt those files. This query can be done in two ways which can be configured by type:

• 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).
  
• exec:/path/to/program　　Here an external program is configured which is called at startup for each     encrypted Private Key file. It is called with two arguments (the first is     of the form ``servername:portnumber'', the second is either     ``RSA'' or ``DSA''), which indicate for which     server and algorithm it has to print the corresponding Pass Phrase to     stdout. The intent is that this external program first runs     security checks to make sure that the system is not compromised by an     attacker, and only when these checks were passed successfully it provides     the Pass Phrase.
  　　Both these security checks, and the way the Pass Phrase is determined, can     be as complex as you like. Mod_ssl just defines the interface: an     executable program which provides the Pass Phrase on stdout.     Nothing more or less! So, if you're really paranoid about security, here     is your interface. Anything else has to be left as an exercise to the     administrator, because local security requirements are so different.
  　　The reuse-algorithm above is used here, too. In other words: The external     program is called only once per unique Pass Phrase.
  

　　Example:

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

SSLProtocol Directive
Description:Configure usable SSL protocol flavors Syntax:SSLProtocol [+|-]protocol ... Default:SSLProtocol all Context:server config, virtual host Override:Options Status:Extension Module:mod_ssl　　This directive can be used to control the SSL protocol flavors mod_ssl should use when establishing its server environment. Clients then can only connect with one of the provided protocols.
　　The available (case-insensitive) protocols are:

• SSLv2　　This is the Secure Sockets Layer (SSL) protocol, version 2.0. It is the     original SSL protocol as designed by Netscape Corporation.
  
• SSLv3　　This is the Secure Sockets Layer (SSL) protocol, version 3.0. It is the     successor to SSLv2 and the currently (as of February 1999) de-facto     standardized SSL protocol from Netscape Corporation. It's supported by     almost all popular browsers.
  
• TLSv1　　This is the Transport Layer Security (TLS) protocol, version 1.0. It is the     successor to SSLv3 and currently (as of February 1999) still under     construction by the Internet Engineering Task Force (IETF). It's still     not supported by any popular browsers.
  
• All　　This is a shortcut for ``+SSLv2 +SSLv3 +TLSv1'' and a     convinient way for enabling all protocols except one when used in     combination with the minus sign on a protocol as the example above      shows.
  

Example
　　 #   enable SSLv3 and TLSv1, but not SSLv2
SSLProtocol all -SSLv2
   

SSLProxyCACertificateFile Directive
Description:File of concatenated PEM-encoded CA Certificates  for Remote Server Auth Syntax:SSLProxyCACertificateFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the all-in-one file where you can assemble the Certificates of Certification Authorities (CA) whose remote servers you deal with. These are used for Remote Server Authentication. Such a file is simply the concatenation of the various PEM-encoded Certificate files, in order of preference. This can be used alternatively and/or additionally to  SSLProxyCACertificatePath.

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

SSLProxyCACertificatePath Directive
Description:Directory of PEM-encoded CA Certificates for  Remote Server Auth Syntax:SSLProxyCACertificatePath directory-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the directory where you keep the Certificates of Certification Authorities (CAs) whose remote servers you deal with. These are used to verify the remote server certificate on Remote Server Authentication.
　　The files in this directory have to be PEM-encoded and are accessed through hash filenames. So usually you can't just place the Certificate files there: you also have to create symbolic links named hash-value.N. And you should always make sure this directory contains the appropriate symbolic links. Use the Makefile which comes with mod_ssl to accomplish this task.

Example
　　 SSLProxyCACertificatePath /usr/local/apache2/conf/ssl.crt/
   

SSLProxyCARevocationFile Directive
Description:File of concatenated PEM-encoded CA CRLs for  Remote Server Auth Syntax:SSLProxyCARevocationFile file-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the all-in-one file where you can assemble the Certificate Revocation Lists (CRL) of Certification Authorities (CA) whose remote servers you deal with. These are used for Remote Server Authentication.  Such a file is simply the concatenation of the various PEM-encoded CRL files, in order of preference. This can be used alternatively and/or additionally to SSLProxyCARevocationPath.

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

SSLProxyCARevocationPath Directive
Description:Directory of PEM-encoded CA CRLs for  Remote Server Auth Syntax:SSLProxyCARevocationPath directory-path Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive sets the directory where you keep the Certificate Revocation Lists (CRL) of Certification Authorities (CAs) whose remote servers you deal with. These are used to revoke the remote server certificate on Remote Server Authentication.
　　The files in this directory have to be PEM-encoded and are accessed through hash filenames. So usually you have not only to place the CRL files there. Additionally you have to create symbolic links named hash-value.rN. And you should always make sure this directory contains the appropriate symbolic links. Use the Makefile which comes with mod_ssl to accomplish this task.

Example
　　 SSLProxyCARevocationPath /usr/local/apache2/conf/ssl.crl/
   

SSLProxyCipherSuite Directive
Description:Cipher Suite available for negotiation in SSL  proxy handshake Syntax:SSLProxyCipherSuite cipher-spec Default:SSLProxyCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP Context:server config, virtual host, directory, .htaccess Override:AuthConfig Status:Extension Module:mod_ssl　　Equivalent to SSLCipherSuite, but for the proxy connection. Please refer to SSLCipherSuite for additional information.
   

SSLProxyEngine Directive
Description:SSL Proxy Engine Operation Switch Syntax:SSLProxyEngine on|off Default:SSLProxyEngine off Context:server config, virtual host Status:Extension Module:mod_ssl　　This directive toggles the usage of the SSL/TLS Protocol Engine for proxy. This is usually used inside a  section to enable SSL/TLS for proxy usage in a particular virtual host. By default the SSL/TLS Protocol Engine is disabled for proxy image both for the main server and all configured virtual hosts.

Example
　　
SSLProxyEngine on
...
  
   

SSLProxyMachineCertificateFile Directive
Description:File of concatenated PEM-encoded client certificates and keys to be used by the proxy Syntax:SSLProxyMachineCertificateFile filename Context:server config Override:Not applicable Status:Extension Module:mod_ssl　　This directive sets the all-in-one file where you keep the certificates and keys used for authentication of the proxy server to remote servers.
　　This referenced file is simply the concatenation of the various PEM-encoded certificate files, in order of preference. Use this directive alternatively or additionally to SSLProxyMachineCertificatePath.

　　Currently there is no support for encrypted private keys
　　Example:

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

SSLProxyMachineCertificatePath Directive
Description:Directory of PEM-encoded client certificates and keys to be used by the proxy Syntax:SSLProxyMachineCertificatePath directory Context:server config Override:Not applicable Status:Extension Module:mod_ssl　　This directive sets the directory where you keep the certificates and keys used for authentication of the proxy server to remote servers.
　　The files in this directory must be PEM-encoded and are accessed through hash filenames. Additionally, you must create symbolic links named hash-value.N. And you should always make sure this directory contains the appropriate symbolic links. Use the Makefile which comes with mod_ssl to accomplish this task.

　　Currently there is no support for encrypted private keys
　　Example:

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

SSLProxyProtocol Directive
Description:Configure usable SSL protocol flavors for proxy usage Syntax:SSLProxyProtocol [+|-]protocol ... Default:SSLProxyProtocol all Context:server config, virtual host Override:Options Status:Extension Module:mod_ssl　　This directive can be used to control the SSL protocol flavors mod_ssl should use when establishing its server environment for proxy . It will only connect to servers using one of the provided protocols.
　　Please refer to SSLProtocol for additional information.
   

SSLProxyVerify Directive
Description:Type of remote server Certificate verification Syntax:SSLProxyVerify level Default:SSLProxyVerify none Context:server config, virtual host, directory, .htaccess Override:AuthConfig Status:Extension Module:mod_ssl　　This directive sets the Certificate verification level for the remote server Authentication. Notice that this directive can be used both in per-server and per-directory context. In per-server context it applies to the remote server authentication process used in the standard SSL handshake when a connection is established. In per-directory context it forces a SSL renegotation with the reconfigured remote server verification level after the HTTP request was read but before the HTTP response is sent.
　　The following levels are available for level:

• none:      no remote server Certificate is required at all
  
• optional:      the remote server may present a valid Certificate
  
• require:      the remote server has to present a valid Certificate
  
• optional_no_ca:      the remote server may present a valid Certificate
        but it need not to be (successfully) verifiable.
  

　　In practice only levels none and require are really interesting, because level optional doesn't work with all servers and level optional_no_ca is actually against the idea of authentication (but can be used to establish SSL test pages, etc.)

Example
　　 SSLProxyVerify require
   

SSLProxyVerifyDepth Directive
Description:Maximum depth of CA Certificates in Remote Server Certificate verification Syntax:SSLProxyVerifyDepth number Default:SSLProxyVerifyDepth 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 remote server does not 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 renegotation with the reconfigured remote server 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 remote server certificate. A depth of 0 means that self-signed remote server certificates are accepted only, the default depth of 1 means the remote server certificate can be self-signed or has to be signed by a CA which is directly known to the server (i.e. the CA's certificate is under SSLProxyCACertificatePath), etc.

Example
　　 SSLProxyVerifyDepth 10
   

SSLRandomSeed Directive
Description:Pseudo Random Number Generator (PRNG) seeding  source Syntax:SSLRandomSeed context source  [bytes] Context:server config Status:Extension Module:mod_ssl　　This configures one or more sources for seeding the Pseudo Random Number Generator (PRNG) in OpenSSL at startup time (context is startup) and/or just before a new SSL connection is established (context is connect). This directive can only be used in the global server context because the PRNG is a global facility.
　　The following source variants are available:

• builtin　　This is the always available builtin seeding source. It's usage     consumes minimum CPU cycles under runtime and hence can be always used     without drawbacks. The source used for seeding the PRNG contains of the     current time, the current process id and (when applicable) a randomly     choosen 1KB extract of the inter-process scoreboard structure of Apache.     The drawback is that this is not really a strong source and at startup     time (where the scoreboard is still not available) this source just     produces a few bytes of entropy. So you should always, at least for the     startup, use an additional seeding source.
  
• file:/path/to/source　　This variant uses an external file /path/to/source as the     source for seeding the PRNG. When bytes is specified, only the     first bytes number of bytes of the file form the entropy (and     bytes is given to /path/to/source as the first     argument). When bytes is not specified the whole file forms the     entropy (and 0 is given to /path/to/source as     the first argument). Use this especially at startup time, for instance     with an available /dev/random and/or     /dev/urandom devices (which usually exist on modern Unix     derivates like FreeBSD and Linux).
  　　But be careful: Usually /dev/random provides only as     much entropy data as it actually has, i.e. when you request 512 bytes of     entropy, but the device currently has only 100 bytes available two things     can happen: On some platforms you receive only the 100 bytes while on     other platforms the read blocks until enough bytes are available (which     can take a long time). Here using an existing /dev/urandom is     better, because it never blocks and actually gives the amount of requested     data. The drawback is just that the quality of the received data may not     be the best.
  　　On some platforms like FreeBSD one can even control how the entropy is     actually generated, i.e. by which system interrupts. More details one can     find under rndcontrol(8) on those platforms. Alternatively, when     your system lacks such a random device, you can use tool     like EGD     (Entropy Gathering Daemon) and run it's client program with the     exec:/path/to/program/ variant (see below) or use     egd:/path/to/egd-socket (see below).
  
• exec:/path/to/program　　This variant uses an external executable     /path/to/program as the source for seeding the     PRNG. When bytes is specified, only the first     bytes number of bytes of its stdout contents     form the entropy. When bytes is not specified, the     entirety of the data produced on stdout form the     entropy. Use this only at startup time when you need a very strong     seeding with the help of an external program (for instance as in     the example above with the truerand utility you can     find in the mod_ssl distribution which is based on the AT&T     truerand library). Using this in the connection context     slows down the server too dramatically, of course.  So usually you     should avoid using external programs in that context.
  
• egd:/path/to/egd-socket (Unix only)　　This variant uses the Unix domain socket of the     external Entropy Gathering Daemon (EGD) (see http://www.lothar.com/tech     /crypto/) to seed the PRNG. Use this if no random device exists     on your platform.
  

Example
　　 SSLRandomSeed startup builtin
SSLRandomSeed startup file:/dev/random
SSLRandomSeed startup file:/dev/urandom 1024
SSLRandomSeed startup exec:/usr/local/bin/truerand 16
SSLRandomSeed connect builtin
SSLRandomSeed connect file:/dev/random
SSLRandomSeed connect file:/dev/urandom 1024

   

SSLRequire Directive
Description:Allow access only when an arbitrarily complex  boolean expression is true Syntax:SSLRequire expression Context:directory, .htaccess Override:AuthConfig Status:Extension Module:mod_ssl　　This directive specifies a general access requirement which has to be fulfilled in order to allow access. It's 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 "ge" word
           | word "in" "{" wordlist "}"
           | word "=~" regex
           | word "!~" regex
wordlist ::= word
           | wordlist "," word
word     ::= digit
           | cstring
           | variable
           | function
digit    ::= [0-9]+
cstring  ::= "..."
variable ::= "%{" varname "}"
function ::= funcname "(" funcargs ")"

　　while for varname any variable from Table 3 can be used. Finally for funcname the following functions are available:

• file(filename)　　This function takes one string argument and expands to the contents of the     file. This is especially useful for matching this contents against a     regular expression, etc.
  

　　Notice that expression is first parsed into an internal machine representation and then evaluated in a second step. Actually, in Global and Per-Server Class context expression is parsed at startup time and at runtime only the machine representation is executed. For Per-Directory context this is different: here expression has to be parsed and immediately executed for every request.

Example
　　 SSLRequire (    %{SSL_CIPHER} !~ m/^(EXP|NULL)-/ \
             and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \
             and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \
             and %{TIME_WDAY} >= 1 and %{TIME_WDAY} = 8 and %{TIME_HOUR}