SSLCACertificateFile指令

This directive sets theall-in-onefile where you can assemble the Certificates of Certification Authorities (CA) whoseclientsyou 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 toSSLCACertificatePath.

SSLCACertificatePath指令

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 namedhash-value.N. And you should always make sure this directory contains the appropriate symbolic links. Use theMakefilewhich comes with mod_ssl to accomplish this task.

SSLCADNRequestFile指令

When a client certificate is requested by mod_ssl, a list ofacceptable Certificate Authority namesis 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 directivesSSLCADNRequestPath或SSLCADNRequestFileare given, then the set of acceptable CA names sent to the client is the names of all the CA certificates given by theSSLCACertificateFile和SSLCACertificatePathdirectives; 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,SSLCADNRequestPathand/orSSLCADNRequestFilecan 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.

SSLCADNRequestFilemust specify anall-in-onefile containing a concatenation of PEM-encoded CA certificates.

SSLCADNRequestPath指令

This optional directive can be used to specify the set ofacceptable CA nameswhich will be sent to the client when a client certificate is requested. See theSSLCADNRequestFiledirective 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 namedhash-value.N. And you should always make sure this directory contains the appropriate symbolic links. Use theMakefilewhich comes with mod_ssl to accomplish this task.

SSLCARevocationFile指令

This directive sets theall-in-onefile where you can assemble the Certificate Revocation Lists (CRL) of Certification Authorities (CA) whoseclientsyou 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 toSSLCARevocationPath.

SSLCARevocationPath指令

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 namedhash-value.rN. And you should always make sure this directory contains the appropriate symbolic links. Use theMakefilewhich comes withmod_sslto accomplish this task.

SSLCertificateChainFile指令

This directive sets the optionalall-in-onefile 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 toSSLCACertificatePathfor 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 intoSSLCACertificatePathhas 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 asingle(either RSA或DSA) based server certificate. If you are using a coupled RSA+DSA certificate pair, this will work only if actually both certificates use thesamecertificate chain. Else the browsers will be confused in this situation.

SSLCertificateFile指令

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.

SSLCertificateKeyFile指令

This directive points to the PEM-encoded Private Key file for the server. If the Private Key is not combined with the Certificate in theSSLCertificateFile, use this additional directive to point to the file with the stand-alone Private Key. WhenSSLCertificateFileis 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.

SSLCipherSuite指令

This complex directive uses a colon-separatedcipher-specstring 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 incipher-specis 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).

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 thecipher-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 (cannotbe 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 correctcipher-specstring. The defaultcipher-specstring 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. Finallypullall 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.

SSLCryptoDevice指令

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".

SSLEngine指令

This directive toggles the usage of the SSL/TLS Protocol Engine. This is usually used inside asection 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.

In Apache 2.1 and later,SSLEnginecan be set tooptional. This enables support for RFC 2817, Upgrading to TLS Within HTTP/1.1. At this time no web browsers support RFC 2817.

SSLHonorCipherOrder指令

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.

SSLMutex指令

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 theAcceptMutexdirective.

The following Mutextypesare 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 thefcntl()fucntion are used as the Mutex. Always use a local disk filesystem for/path/to/mutexand 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/mutexto 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 youhaveto use the semaphore mutex.

• flock:/path/to/mutex

  This is similar to thefcntl:/path/to/mutexmethod with the exception that theflock()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 betweenfcntl和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.

SSLOptions指令

This directive can be used to control various run-time options on a per-directory basis. Normally, if multipleSSLOptionscould apply to a directory, then the most specific one is taken completely; the options are not merged. However ifallthe options on theSSLOptionsdirective 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 availableoptions 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和SSL_CLIENT_CERT_CHAIN_n(withn= 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'sopenssl x509command:openssl x509 -noout -subject -incertificate.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

  Thisforcesforbidden access whenSSLRequireSSL或SSLRequiresuccessfully 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 toSSLRequireSSL或SSLRequireis overridden (because that's how the ApacheSatisfymechanism should work.) But for strict access restriction you can useSSLRequireSSLand/orSSLRequirein 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 whereeveryper-directory reconfiguration of SSL parameters causes afullSSL 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.

SSLPassPhraseDialog指令

When Apache starts up it has to read the various Certificate (seeSSLCertificateFile) and Private Key (seeSSLCertificateKeyFile) 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 bytype:

• 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 youcanuse 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 thebuiltinmode onstdin, and is expected to write password strings onstdout. If several passwords are needed (or an incorrect password is entered), additional prompt text will be written subsequent to the first password being returned, and more passwords must then be written back.

• exec:/path/to/program

  Here an external program is configured which is called at startup for each encrypted Private Key file. It is called with two arguments (the first is of the form "servername:portnumber", the second is either "RSA" or "DSA"), which indicate for which server and algorithm it has to print the corresponding Pass Phrase tostdout. 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 onstdout. 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.

SSLProtocol指令

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.

SSLProxyCACertificateFile指令

This directive sets theall-in-onefile where you can assemble the Certificates of Certification Authorities (CA) whoseremote serversyou 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 toSSLProxyCACertificatePath.

SSLProxyCACertificatePath指令

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 namedhash-value.N. And you should always make sure this directory contains the appropriate symbolic links. Use theMakefilewhich comes with mod_ssl to accomplish this task.

SSLProxyCARevocationFile指令

This directive sets theall-in-onefile where you can assemble the Certificate Revocation Lists (CRL) of Certification Authorities (CA) whoseremote serversyou 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 toSSLProxyCARevocationPath.

SSLProxyCARevocationPath指令

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 namedhash-value.rN. And you should always make sure this directory contains the appropriate symbolic links. Use theMakefilewhich comes withmod_sslto accomplish this task.

SSLProxyCipherSuite指令

Equivalent toSSLCipherSuite, but for the proxy connection. Please refer toSSLCipherSuitefor additional information.

SSLProxyEngine指令

This directive toggles the usage of the SSL/TLS Protocol Engine for proxy. This is usually used inside asection 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.

SSLProxyMachineCertificateFile指令

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 toSSLProxyMachineCertificatePath.

SSLProxyMachineCertificatePath指令

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 namedhash-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.

SSLProxyProtocol指令

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 toSSLProtocolfor additional information.

SSLProxyVerify指令

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. 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 by the proxy. 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 forlevel:

• none: no remote server Certificate is required at all
• optional: the remote servermaypresent a valid Certificate
• require: the remote serverhas topresent 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 levelsnone和requireare really interesting, because leveloptionaldoesn't work with all servers and leveloptional_no_cais actually against the idea of authentication (but can be used to establish SSL test pages, etc.)

SSLProxyVerifyDepth指令

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 underSSLProxyCACertificatePath), etc.

SSLRandomSeed指令

This configures one or more sources for seeding the Pseudo Random Number Generator (PRNG) in OpenSSL at startup time (contextisstartup) and/or just before a new SSL connection is established (contextisconnect). This directive can only be used in the global server context because the PRNG is a global facility.

The followingsourcevariants 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/sourceas the source for seeding the PRNG. Whenbytesis specified, only the firstbytesnumber of bytes of the file form the entropy (andbytesis given to/path/to/sourceas the first argument). Whenbytesis not specified the whole file forms the entropy (and0is given to/path/to/sourceas the first argument). Use this especially at startup time, for instance with an available/dev/randomand/or/dev/urandomdevices (which usually exist on modern Unix derivates like FreeBSD and Linux).

  But be careful: Usually/dev/randomprovides 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/urandomis 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 underrndcontrol(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 theexec:/path/to/program/variant (see below) or useegd:/path/to/egd-socket(see below).

• exec:/path/to/program

  This variant uses an external executable/path/to/programas the source for seeding the PRNG. Whenbytesis specified, only the firstbytesnumber of bytes of itsstdoutcontents form the entropy. Whenbytesis not specified, the entirety of the data produced onstdoutform 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 thetruerandutility you can find in the mod_ssl distribution which is based on the AT&Ttruerandlibrary). 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.

SSLRequire指令

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.

Theexpressionmust match the following syntax (given as a BNF grammar notation):

expr ::= "true" | "false" | "!" expr | expr "&&" expr | expr "||" expr | "(" expr ")" | comp comp ::= word "==" word | word "eq" word | word "!=" word | word "ne" word | word "<" word | word "lt" word | word "<=" word | word "le" word | word ">" word | word "gt" word | word ">=" word | word "ge" word | word "in" "{" wordlist "}" | word "in" "OID(" word ")" | word "=~" regex | word "!~" regex wordlist ::= word | wordlist "," word word ::= digit | cstring | variable | function digit ::= [0-9]+ cstring ::= "..." variable ::= "%{" varname "}" function ::= funcname "(" funcargs ")"

while forvarnameany variable from Table 3 can be used. Finally forfuncnamethe 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 thatexpressionis first parsed into an internal machine representation and then evaluated in a second step. Actually, in Global and Per-Server Class contextexpressionis parsed at startup time and at runtime only the machine representation is executed. For Per-Directory context this is different: hereexpressionhas to be parsed and immediately executed for every request.

OID()function expects to find zero or more instances of the given OID in the client certificate, and compares the left-hand side string against the value of matching OID attributes. Every matching OID is checked, until a match is found.

Standard CGI/1.0 and Apache variables:

HTTP_USER_AGENT PATH_INFO AUTH_TYPE HTTP_REFERER QUERY_STRING SERVER_SOFTWARE HTTP_COOKIE REMOTE_HOST API_VERSION HTTP_FORWARDED REMOTE_IDENT TIME_YEAR HTTP_HOST IS_SUBREQ TIME_MON HTTP_PROXY_CONNECTION DOCUMENT_ROOT TIME_DAY HTTP_ACCEPT SERVER_ADMIN TIME_HOUR HTTP:headername SERVER_NAME TIME_MIN THE_REQUEST SERVER_PORT TIME_SEC REQUEST_METHOD SERVER_PROTOCOL TIME_WDAY REQUEST_SCHEME REMOTE_ADDR TIME REQUEST_URI REMOTE_USER ENV:variablenameREQUEST_FILENAME

SSL-related variables:

HTTPS SSL_CLIENT_M_VERSION SSL_SERVER_M_VERSION SSL_CLIENT_M_SERIAL SSL_SERVER_M_SERIAL SSL_PROTOCOL SSL_CLIENT_V_START SSL_SERVER_V_START SSL_SESSION_ID SSL_CLIENT_V_END SSL_SERVER_V_END SSL_CIPHER SSL_CLIENT_S_DN SSL_SERVER_S_DN SSL_CIPHER_EXPORT SSL_CLIENT_S_DN_C SSL_SERVER_S_DN_C SSL_CIPHER_ALGKEYSIZE SSL_CLIENT_S_DN_ST SSL_SERVER_S_DN_ST SSL_CIPHER_USEKEYSIZE SSL_CLIENT_S_DN_L SSL_SERVER_S_DN_L SSL_VERSION_LIBRARY SSL_CLIENT_S_DN_O SSL_SERVER_S_DN_O SSL_VERSION_INTERFACE SSL_CLIENT_S_DN_OU SSL_SERVER_S_DN_OU SSL_CLIENT_S_DN_CN SSL_SERVER_S_DN_CN SSL_CLIENT_S_DN_T SSL_SERVER_S_DN_T SSL_CLIENT_S_DN_I SSL_SERVER_S_DN_I SSL_CLIENT_S_DN_G SSL_SERVER_S_DN_G SSL_CLIENT_S_DN_S SSL_SERVER_S_DN_S SSL_CLIENT_S_DN_D SSL_SERVER_S_DN_D SSL_CLIENT_S_DN_UID SSL_SERVER_S_DN_UID SSL_CLIENT_S_DN_Email SSL_SERVER_S_DN_Email SSL_CLIENT_I_DN SSL_SERVER_I_DN SSL_CLIENT_I_DN_C SSL_SERVER_I_DN_C SSL_CLIENT_I_DN_ST SSL_SERVER_I_DN_ST SSL_CLIENT_I_DN_L SSL_SERVER_I_DN_L SSL_CLIENT_I_DN_O SSL_SERVER_I_DN_O SSL_CLIENT_I_DN_OU SSL_SERVER_I_DN_OU SSL_CLIENT_I_DN_CN SSL_SERVER_I_DN_CN SSL_CLIENT_I_DN_T SSL_SERVER_I_DN_T SSL_CLIENT_I_DN_I SSL_SERVER_I_DN_I SSL_CLIENT_I_DN_G SSL_SERVER_I_DN_G SSL_CLIENT_I_DN_S SSL_SERVER_I_DN_S SSL_CLIENT_I_DN_D SSL_SERVER_I_DN_D SSL_CLIENT_I_DN_UID SSL_SERVER_I_DN_UID SSL_CLIENT_I_DN_Email SSL_SERVER_I_DN_Email SSL_CLIENT_A_SIG SSL_SERVER_A_SIG SSL_CLIENT_A_KEY SSL_SERVER_A_KEY SSL_CLIENT_CERT SSL_SERVER_CERT SSL_CLIENT_CERT_CHAIN_nSSL_CLIENT_VERIFY

SSLRequireSSL指令

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.

SSLSessionCache指令

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 bydifferentpre-forked server processes. Here an inter-process cache helps to avoid unneccessary session handshakes.

The following four storagetypes are currently supported:

• none

  This disables the global/inter-process Session Cache. This will incur a noticeable speed penalty and may cause problems if using certain browsers, particularly if client certificates are enabled. This setting is not recommended.

• nonenotnull

  This disables any global/inter-process Session Cache. However it does force OpenSSL to send a non-null session ID to accommodate buggy clients that require one.

• dbm:/path/to/datafile

  This makes use of a DBM hashfile on the local disk to synchronize the local OpenSSL memory caches of the server processes. This session cache may suffer reliability issues under high load.

• shm:/path/to/datafile[(size)]

  This makes use of a high-performance cyclic buffer (approx.sizebytes in size) inside a shared memory segment in RAM (established via/path/to/datafile) to synchronize the local OpenSSL memory caches of the server processes. This is the recommended session cache.

• dc:UNIX:/path/to/socket

  This makes use of the distcache distributed session caching libraries. The argument should specify the location of the server or proxy to be used using the distcache address syntax; for example,UNIX:/path/to/socketspecifies a UNIX domain socket (typically a local dc_client proxy);IP:server.example.com:9001specifies an IP address.

SSLSessionCacheTimeout指令

This directive sets the timeout in seconds for the information stored in the global/inter-process SSL Session Cache and the OpenSSL internal memory cache. It can be set as low as 15 for testing, but should be set to higher values like 300 in real life.

SSLUserName指令

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 variableREMOTE_USERto be set. Thevarnamecan be any of the SSL environment variables.

Note that this directive has no effect if theFakeBasicoption is used (see SSLOptions).

SSLVerifyClient指令

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 renegotation with the reconfigured client verification level after the HTTP request was read but before the HTTP response is sent.

The following levels are available forlevel:

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

In practice only levelsnone和requireare really interesting, because leveloptionaldoesn't work with all browsers and leveloptional_no_cais actually against the idea of authentication (but can be used to establish SSL test pages, etc.)

SSLVerifyDepth指令

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 renegotation 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 underSSLCACertificatePath), etc.