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- _ _
- _ __ ___ ___ __| | ___ ___| |
- | '_ ` _ \ / _ \ / _` | / __/ __| |
- | | | | | | (_) | (_| | \__ \__ \ | ``mod_ssl combines the flexibility of
- |_| |_| |_|\___/ \__,_|___|___/___/_| Apache with the security of OpenSSL.''
- |_____|
- mod_ssl ``Ralf Engelschall has released an
- Apache Interface to OpenSSL excellent module that integrates
- http://www.modssl.org/ Apache and SSLeay.''
- Version 2.8 -- Tim J. Hudson
-
- SYNOPSIS
-
- This Apache module provides strong cryptography for the Apache 1.3 webserver
- via the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS
- v1) protocols by the help of the SSL/TLS implementation library OpenSSL which
- is based on SSLeay from Eric A. Young and Tim J. Hudson. The mod_ssl package
- was created in April 1998 by Ralf S. Engelschall and was originally derived
- from software developed by Ben Laurie for use in the Apache-SSL HTTP server
- project.
-
- SOURCES
-
- Here is a short overview of the source files:
-
- * README .................. This file ;)
- # Makefile.in ............. Makefile template for Unix platform
- # config.m4 ............... Autoconf stub for the Apache config mechanism
- # mod_ssl.c ............... main source file containing API structures
- # mod_ssl.h ............... common header file of mod_ssl
- # ssl_engine_config.c ..... module configuration handling
- # ssl_engine_dh.c ......... DSA/DH support
- # ssl_engine_init.c ....... module initialization
- # ssl_engine_io.c ......... I/O support
- # ssl_engine_kernel.c ..... SSL engine kernel
- # ssl_engine_log.c ........ logfile support
- # ssl_engine_mutex.c ...... mutual exclusion support
- # ssl_engine_pphrase.c .... pass-phrase handling
- # ssl_engine_rand.c ....... PRNG support
- # ssl_engine_vars.c ....... Variable Expansion support
- # ssl_expr.c .............. expression handling main source
- # ssl_expr.h .............. expression handling common header
- # ssl_expr_scan.c ......... expression scanner automaton (pre-generated)
- # ssl_expr_scan.l ......... expression scanner source
- # ssl_expr_parse.c ........ expression parser automaton (pre-generated)
- # ssl_expr_parse.h ........ expression parser header (pre-generated)
- # ssl_expr_parse.y ........ expression parser source
- # ssl_expr_eval.c ......... expression machine evaluation
- # ssl_scache.c ............ session cache abstraction layer
- # ssl_scache_dbm.c ........ session cache via DBM file
- ~ ssl_scache_shmcb.c ...... session cache via shared memory cyclic buffer
- ~ ssl_scache_shmht.c ...... session cache via shared memory hash table
- # ssl_util.c .............. utility functions
- # ssl_util_ssl.c .......... the OpenSSL companion source
- # ssl_util_ssl.h .......... the OpenSSL companion header
- # ssl_util_table.c ........ the hash table library source
- # ssl_util_table.h ........ the hash table library header
-
- Legend: # = already ported to Apache 2.0 and is cleaned up
- * = ported to Apache 2.0 but still needs cleaning up
- ~ = ported to Apache 2.0 but still needs work
- - = port still not finished
-
- The source files are written in clean ANSI C and pass the ``gcc -O -g
- -ggdb3 -Wall -Wshadow -Wpointer-arith -Wcast-align -Wmissing-prototypes
- -Wmissing-declarations -Wnested-externs -Winline'' compiler test
- (assuming `gcc' is GCC 2.95.2 or newer) without any complains. When
- you make changes or additions make sure the source still passes this
- compiler test.
-
- FUNCTIONS
-
- Inside the source code you will be confronted with the following types of
- functions which can be identified by their prefixes:
-
- ap_xxxx() ............... Apache API function
- ssl_xxxx() .............. mod_ssl function
- SSL_xxxx() .............. OpenSSL function (SSL library)
- OpenSSL_xxxx() .......... OpenSSL function (SSL library)
- X509_xxxx() ............. OpenSSL function (Crypto library)
- PEM_xxxx() .............. OpenSSL function (Crypto library)
- EVP_xxxx() .............. OpenSSL function (Crypto library)
- RSA_xxxx() .............. OpenSSL function (Crypto library)
-
- DATA STRUCTURES
-
- Inside the source code you will be confronted with the following
- data structures:
-
- server_rec .............. Apache (Virtual) Server
- conn_rec ................ Apache Connection
- request_rec ............. Apache Request
- SSLModConfig ............ mod_ssl (Global) Module Configuration
- SSLSrvConfig ............ mod_ssl (Virtual) Server Configuration
- SSLDirConfig ............ mod_ssl Directory Configuration
- SSLConnConfig ........... mod_ssl Connection Configuration
- SSLFilterRec ............ mod_ssl Filter Context
- SSL_CTX ................. OpenSSL Context
- SSL_METHOD .............. OpenSSL Protocol Method
- SSL_CIPHER .............. OpenSSL Cipher
- SSL_SESSION ............. OpenSSL Session
- SSL ..................... OpenSSL Connection
- BIO ..................... OpenSSL Connection Buffer
-
- For an overview how these are related and chained together have a look at the
- page in README.dsov.{fig,ps}. It contains overview diagrams for those data
- structures. It's designed for DIN A4 paper size, but you can easily generate
- a smaller version inside XFig by specifing a magnification on the Export
- panel.
-
- EXPERIMENTAL CODE
-
- Experimental code is always encapsulated as following:
-
- | #ifdef SSL_EXPERIMENTAL_xxxx
- | ...
- | #endif
-
- This way it is only compiled in when this define is enabled with
- the APACI --enable-rule=SSL_EXPERIMENTAL option and as long as the
- C pre-processor variable SSL_EXPERIMENTAL_xxxx_IGNORE is _NOT_
- defined (via CFLAGS). Or in other words: SSL_EXPERIMENTAL enables all
- SSL_EXPERIMENTAL_xxxx variables, except if SSL_EXPERIMENTAL_xxxx_IGNORE
- is already defined. Currently the following features are experimental:
-
- o SSL_EXPERIMENTAL_ENGINE
- The ability to support the new forthcoming OpenSSL ENGINE stuff.
- Until this development branch of OpenSSL is merged into the main
- stream, you have to use openssl-engine-0.9.x.tar.gz for this.
- mod_ssl automatically recognizes this OpenSSL variant and then can
- activate external crypto devices through SSLCryptoDevice directive.
-
- INCOMPATIBILITIES
-
- The following intentional incompatibilities exist between mod_ssl 2.x
- from Apache 1.3 and this mod_ssl version for Apache 2.0:
-
- o The complete EAPI-based SSL_VENDOR stuff was removed.
- o The complete EAPI-based SSL_COMPAT stuff was removed.
- o The <IfDefine> variable MOD_SSL is no longer provided automatically
-
- MAJOR CHANGES
-
- The following major changes were made between mod_ssl 2.x
- from Apache 1.3 and this mod_ssl version for Apache 2.0:
-
- o The DBM based session cache is now based on APR's DBM API only.
- o The shared memory based session cache is now based on APR's APIs.
- o SSL I/O is now implemented in terms of filters rather than BUFF
- o Eliminated ap_global_ctx. Storing Persistant information in
- process_rec->pool->user_data. The ssl_pphrase_Handle_CB() and
- ssl_config_global_* () functions have an extra parameter now -
- "server_rec *" - which is used to retrieve the SSLModConfigRec.
- o Properly support restarts, allowing mod_ssl to be added to a server
- that is already running and to change server certs/keys on restart
- o Various performance enhancements
- o proxy support is no longer an "extension", much of the mod_ssl core
- was re-written (ssl_engine_{init,kernel,config}.c) to be generic so
- it could be re-used in proxy mode.
- - the optional function ssl_proxy_enable is provide for mod_proxy
- to enable proxy support
- - proxy support now requires 'SSLProxyEngine on' to be configured
- - proxy now supports SSLProxyCARevocation{Path,File} in addition to
- the original SSLProxy* directives
- o per-directory SSLCACertificate{File,Path} is now thread-safe but
- requires SSL_set_cert_store patch to OpenSSL
- o RSA sslc is supported via ssl_toolkit_compat.h
- o the ssl_engine_{ds,ext}.c source files are obsolete and no longer
- exist
-
- TODO
-
- o SSL renegotiations in combination with POST request
- o Port all remaining code (code inside #if 0...#endif blocks)
- o Do we need SSL_set_read_ahead()?
- o the ssl_expr api is NOT THREAD SAFE. race conditions exist:
- -in ssl_expr_comp() if SSLRequire is used in .htaccess
- (ssl_expr_info is global)
- -is ssl_expr_eval() if there is an error
- (ssl_expr_error is global)
- o SSLRequire directive (parsing of) leaks memory
- o Diffie-Hellman-Parameters for temporary keys are hardcoded in
- ssl_engine_dh.c, while the comment in ssl_engine_kernel.c says:
- "it is suggested that keys be changed daily or every 500
- transactions, and more often if possible."
- o ssl_var_lookup could be rewritten to be MUCH faster
- o CRL callback should be pluggable
- o session cache store should be pluggable
- o init functions should return status code rather than ssl_die()
- o ssl_engine_pphrase.c needs to be reworked so it is generic enough
- to also decrypt proxy keys
- o the shmcb code should just align its memory segment rather than
- jumping through all the "safe" memcpy and memset hoops
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