Index: openssl-1.0.2a/doc/ssl/SSL_COMP_add_compression_method.pod =================================================================== --- openssl-1.0.2a.orig/doc/ssl/SSL_COMP_add_compression_method.pod 2015-04-03 22:10:19.262805732 +0200 +++ openssl-1.0.2a/doc/ssl/SSL_COMP_add_compression_method.pod 2015-04-03 22:10:28.958939879 +0200 @@ -41,6 +41,24 @@ of compression methods supported on a pe The OpenSSL library has the compression methods B and (when especially enabled during compilation) B available. +And, there is an environment variable to switch the compression +methods off and on. In default the compression is off to mitigate +the so called CRIME attack ( CVE-2012-4929). If you want to enable +compression again set OPENSSL_NO_DEFAULT_ZLIB to "no". + +The variable can be switched on and off at runtime; when this variable +is set "no" compression is enabled, otherwise no, for example: + +in shell 'export OPENSSL_NO_DEFAULT_ZLIB=no' +or in C to call +int setenv(const char *name, const char *value, int overwrite); and +int unsetenv(const char *name); + +Note: This reverts the behavior of the variable as it was before! + +And pay attention that this freaure is temporary, it maybe changed by +the following updates. + =head1 WARNINGS Once the identities of the compression methods for the TLS protocol have Index: openssl-1.0.2a/ssl/ssl_ciph.c =================================================================== --- openssl-1.0.2a.orig/ssl/ssl_ciph.c 2015-04-03 22:10:28.959939893 +0200 +++ openssl-1.0.2a/ssl/ssl_ciph.c 2015-04-03 22:12:33.425662139 +0200 @@ -478,10 +478,16 @@ static void load_builtin_compressions(vo if (ssl_comp_methods == NULL) { SSL_COMP *comp = NULL; + const char *nodefaultzlib; MemCheck_off(); ssl_comp_methods = sk_SSL_COMP_new(sk_comp_cmp); - if (ssl_comp_methods != NULL) { + /* The default is "no" compression to avoid CRIME/BEAST */ + nodefaultzlib = getenv("OPENSSL_NO_DEFAULT_ZLIB"); + if ( ssl_comp_methods != NULL && + nodefaultzlib && + strncmp( nodefaultzlib, "no", 2) == 0) + { comp = (SSL_COMP *)OPENSSL_malloc(sizeof(SSL_COMP)); if (comp != NULL) { comp->method = COMP_zlib();