From 97e4c9276c5e5b1d9504d5deec0b5d65301a087b Mon Sep 17 00:00:00 2001 From: Graham Leggett Date: Fri, 4 Apr 2008 16:11:31 +0000 Subject: [PATCH] mod_session_crypto: Add a session encoding implementation capable of encrypting and decrypting sessions wherever they may be stored. Introduces a level of privacy when sessions are stored on the browser. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@644751 13f79535-47bb-0310-9956-ffa450edef68 --- CHANGES | 5 + docs/manual/mod/mod_session_crypto.xml | 200 +++++++++++ modules/session/config.m4 | 2 +- modules/session/mod_session_crypto.c | 468 +++++++++++++++++++++++++ 4 files changed, 674 insertions(+), 1 deletion(-) create mode 100644 docs/manual/mod/mod_session_crypto.xml create mode 100644 modules/session/mod_session_crypto.c diff --git a/CHANGES b/CHANGES index 9011e7e566..b1e275b8e2 100644 --- a/CHANGES +++ b/CHANGES @@ -2,6 +2,11 @@ Changes with Apache 2.3.0 [ When backported to 2.2.x, remove entry from this file ] + *) mod_session_crypto: Add a session encoding implementation capable + of encrypting and decrypting sessions wherever they may be stored. + Introduces a level of privacy when sessions are stored on the + browser. [Graham Leggett] + *) mod_session_cookie: Add a session implementation capable of storing session information within cookies on the browser. Useful for high volume sites where server bound sessions are too resource intensive. diff --git a/docs/manual/mod/mod_session_crypto.xml b/docs/manual/mod/mod_session_crypto.xml new file mode 100644 index 0000000000..b6fba7c131 --- /dev/null +++ b/docs/manual/mod/mod_session_crypto.xml @@ -0,0 +1,200 @@ + + + + + + + + + +mod_session_crypto +Session encryption support +Extension +mod_session_crypto.c +session_crypto_module + + + Warning +

The session modules make use of HTTP cookies, and as such can fall + victim to Cross Site Scripting attacks, or expose potentially private + information to clients. Please ensure that the relevant risks have + been taken into account before enabling the session functionality on + your server.

+ + +

This submodule of mod_session provides support for the + encryption of user sessions before being written to a local database, or + written to a remove browser via an HTTP cookie.

+ +

This can help provide privacy to user sessions where the contents of + the session should be kept private from the user, or where protection is + needed against the effects of cross site scripting attacks.

+ +

For more details on the session interface, see the documentation for + the mod_session module.

+ + +mod_session +mod_session_cookie +mod_session_dbd + +
Basic Usage + +

To create a simple encrypted session and store it in a cookie called + session, configure the session as follows:

+ + Browser based encrypted session + Session On
+ SessionCookieName session path=/
+ SessionCryptoPassphrase secret + + +

The session will be encrypted with the given key. Different servers can + be configured to share sessions by ensuring the same encryption key is used + on each server.

+ +

If the encryption key is changed, sessions will be invalidated + automatically.

+ +

For documentation on how the session can be used to store username + and password details, see the mod_auth_form module.

+ +
+ + +SessionCryptoPassphrase +The key used to encrypt the session +SessionCryptoPassphrase secret +none +directory + +Available in Apache 2.3.0 and later + + +

The SessionCryptoPassphrase directive specifies the key + to be used to encrypt the contents of the session before writing the session, or + decrypting the contents of the session after reading the session.

+ +

Keys are more secure when they are long, and consist of truly random characters. + Changing the key on a server has the effect of invalidating all existing sessions.

+ + + + + +SessionCryptoCertificateFile +The certificate used to encrypt and decrypt the session +SessionCryptoCertificateFile file +none +directory + +Available in Apache 2.3.0 and later + + +

The SessionCryptoCertificateFile directive specifies the name + of a certificate to be used to encrypt the contents of the session before writing + the session, or decrypting the content of the session after reading the session.

+ +

Changing the certificate on a server has the effect of invalidating all existing + sessions.

+ + Experimental +

This directive is dependent on experimental support for assymetrical encryption + support currently available in prerelease versions of OpenSSL, and will only be + available on platforms that support it.

+ + + + + + +SessionCryptoCertificateKeyFile +The certificate key used to encrypt and decrypt the session +SessionCryptoCertificateKeyFile file +none +directory + +Available in Apache 2.3.0 and later + + +

The SessionCryptoCertificateKeyFile directive specifies the name + of a certificate key to be used alongside a certificate to encrypt the contents of the + session before writing the session, or decrypting the content of the session after reading + the session.

+ +

Changing the certificate or key on a server has the effect of invalidating all existing + sessions.

+ + Experimental +

This directive is dependent on experimental support for asymmetrical encryption + support currently available in prerelease versions of OpenSSL, and will only be + available on platforms that support it.

+ + + + + + +SessionCryptoCipher +The name of the cipher to use during encryption / decryption +SessionCryptoCipher cipher +AES256 +directory + +Available in Apache 2.3.0 and later + + +

The SessionCryptoCipher directive specifies the name + of the cipher to use during encryption. The ciphers available will depend on the + underlying encryption toolkit on the server platform.

+ + + + +SessionCryptoDigest +The name of the digest to use during encryption / decryption +SessionCryptoDigest cipher +SHA +directory + +Available in Apache 2.3.0 and later + + +

The SessionCryptoDigest directive specifies the name + of the digest to use during encryption. The list of digests available will depend + on the underlying encryption toolkit on the server platform.

+ + + + +SessionCryptoEngine +The name of the engine to use during encryption / decryption +SessionCryptoEngine engine +none +directory + +Available in Apache 2.3.0 and later + + +

The SessionCryptoEngine directive specifies the name + of the engine to use during encryption, depending on the capabilities of the + underlying encryption toolkit on the server platform.

+ + + + diff --git a/modules/session/config.m4 b/modules/session/config.m4 index 53548cf076..9b1d523ced 100644 --- a/modules/session/config.m4 +++ b/modules/session/config.m4 @@ -11,7 +11,7 @@ dnl various places, such as databases, LDAP, or cookies. dnl APACHE_MODULE(session, session module, , , most) APACHE_MODULE(session_cookie, session cookie module, , , most) -dnl APACHE_MODULE(session_crypto, session crypto module, , , most) +APACHE_MODULE(session_crypto, session crypto module, , , most) dnl APACHE_MODULE(session_dbd, session dbd module, , , most) dnl APACHE_MODULE(session_ldap, session ldap module, , , most) diff --git a/modules/session/mod_session_crypto.c b/modules/session/mod_session_crypto.c new file mode 100644 index 0000000000..12da8c4d1c --- /dev/null +++ b/modules/session/mod_session_crypto.c @@ -0,0 +1,468 @@ +/* Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#define CORE_PRIVATE + +#include "mod_session.h" +#include "apu_version.h" +#include "apr_base64.h" /* for apr_base64_decode et al */ +#include "apr_ssl.h" /* for apr_*_encrypt et al */ +#include "apr_lib.h" +#include "apr_strings.h" +#include "http_log.h" + +#define LOG_PREFIX "mod_session_crypto: " +#define DEFAULT_CIPHER "AES256" +#define DEFAULT_DIGEST "SHA" + +module AP_MODULE_DECLARE_DATA session_crypto_module; + +/** + * Structure to carry the per-dir session config. + */ +typedef struct { + const char *passphrase; + int passphrase_set; + const char *certfile; + int certfile_set; + const char *keyfile; + int keyfile_set; + const char *cipher; + int cipher_set; + const char *digest; + int digest_set; + const char *engine; + int engine_set; +} session_crypto_dir_conf; + +/** + * Initialise the encryption as per the current config. + * + * Returns APR_SUCCESS if successful. + */ +#if APU_MAJOR_VERSION > 1 || (APU_MAJOR_VERSION == 1 && APU_MINOR_VERSION >= 3) +static apr_status_t crypt_init(request_rec * r, apr_evp_factory_t ** f, apr_evp_crypt_key_e * key, session_crypto_dir_conf * conf) +{ + apr_status_t res; + + if (!conf->certfile_set && !conf->keyfile_set && !conf->passphrase_set) { + ap_log_rerror(APLOG_MARK, APLOG_WARNING, 0, r, LOG_PREFIX + "encryption not configured, " + "no passphrase or certfile/keyfile set"); + return APR_EGENERAL; + } + + /* set up */ + if (conf->certfile_set) { + *key = APR_EVP_KEY_PUBLIC; + res = apr_evp_factory_create(f, conf->keyfile, conf->certfile, NULL, + NULL, NULL, conf->digest, APR_EVP_FACTORY_ASYM, r->pool); + if (APR_ENOTIMPL == res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "generic public/private key encryption is not supported by " + "this version of APR. session encryption not possible"); + } + } + if (conf->passphrase) { + *key = APR_EVP_KEY_SYM; + res = apr_evp_factory_create(f, NULL, NULL, conf->cipher, + conf->passphrase, NULL, conf->digest, APR_EVP_FACTORY_SYM, r->pool); + if (APR_ENOTIMPL == res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "generic symmetrical encryption is not supported by this " + "version of APR. session encryption not possible"); + } + } + if (APR_STATUS_IS_ENOCIPHER(res)) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "the cipher '%s' was not found", conf->cipher); + } + if (APR_STATUS_IS_ENODIGEST(res)) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "the digest '%s' was not found", conf->digest); + } + if (APR_STATUS_IS_ENOCERT(res)) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "the public and private key could not be extracted from " + "the certificates"); + } + if (APR_STATUS_IS_ENOENGINE(res)) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "the engine '%s' was not found", conf->engine); + } + if (APR_SUCCESS != res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "encryption could not be configured. Please check the " + "certificates and/or passphrase as appropriate"); + apr_evp_factory_cleanup(*f); + return APR_EGENERAL; + } + + return APR_SUCCESS; +} +#endif + +/** + * Encrypt the string given as per the current config. + * + * Returns APR_SUCCESS if successful. + */ +static apr_status_t encrypt_string(request_rec * r, const char *in, char **out) +{ +#if APU_MAJOR_VERSION > 1 || (APU_MAJOR_VERSION == 1 && APU_MINOR_VERSION >= 3) + apr_status_t res; + apr_evp_factory_t *f = NULL; + apr_evp_crypt_t *e = NULL; + apr_evp_crypt_key_e key; + unsigned char *encrypt = NULL; + apr_size_t encryptlen, tlen; + char *base64; + + session_crypto_dir_conf *conf = ap_get_module_config(r->per_dir_config, + &session_crypto_module); + + /* don't attempt to encrypt an empty string, trying to do so causes a segfault */ + if (!in || !*in) { + return APR_SUCCESS; + } + + res = crypt_init(r, &f, &key, conf); + if (res != APR_SUCCESS) { + return res; + } + + res = apr_evp_crypt_init(f, &e, APR_EVP_ENCRYPT, key, r->pool); + if (APR_SUCCESS != res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "encryption could be configured but not initialised"); + apr_evp_factory_cleanup(f); + return res; + } + + /* encrypt the given string */ + res = apr_evp_crypt(e, &encrypt, &encryptlen, (unsigned char *) in, strlen(in)); + if (APR_SUCCESS != res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "attempt to encrypt failed"); + apr_evp_factory_cleanup(f); + apr_evp_crypt_cleanup(e); + return res; + } + res = apr_evp_crypt_finish(e, encrypt + encryptlen, &tlen); + if (APR_SUCCESS != res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "attempt to finish the encryption failed"); + apr_evp_factory_cleanup(f); + apr_evp_crypt_cleanup(e); + return res; + } + encryptlen += tlen; + + /* base64 encode the result */ + base64 = apr_pcalloc(r->pool, apr_base64_encode_len(encryptlen + 1) * sizeof(char)); + apr_base64_encode(base64, (const char *) encrypt, encryptlen); + *out = base64; + + /* clean up afterwards */ + apr_evp_factory_cleanup(f); + apr_evp_crypt_cleanup(e); + + return res; + +#else + ap_log_rerror(APLOG_MARK, APLOG_ERR, APR_ENOTIMPL, r, LOG_PREFIX + "crypto is not supported by APR on this platform"); + return APR_ENOTIMPL; +#endif +} + +/** + * Decrypt the string given as per the current config. + * + * Returns APR_SUCCESS if successful. + */ +static apr_status_t decrypt_string(request_rec * r, const char *in, char **out) +{ +#if APU_MAJOR_VERSION > 1 || (APU_MAJOR_VERSION == 1 && APU_MINOR_VERSION >= 3) + apr_status_t res; + apr_evp_factory_t *f = NULL; + apr_evp_crypt_t *e = NULL; + apr_evp_crypt_key_e key; + unsigned char *decrypted = NULL; + apr_size_t decryptedlen, tlen; + apr_size_t decodedlen; + char *decoded; + + session_crypto_dir_conf *conf = ap_get_module_config(r->per_dir_config, + &session_crypto_module); + + res = crypt_init(r, &f, &key, conf); + if (res != APR_SUCCESS) { + return res; + } + + res = apr_evp_crypt_init(f, &e, APR_EVP_DECRYPT, key, r->pool); + if (APR_SUCCESS != res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "decryption could be configured but not initialised"); + apr_evp_factory_cleanup(f); + return res; + } + + /* strip base64 from the string */ + decoded = apr_palloc(r->pool, apr_base64_decode_len(in)); + decodedlen = apr_base64_decode(decoded, in); + decoded[decodedlen] = '\0'; + + /* decrypt the given string */ + res = apr_evp_crypt(e, &decrypted, &decryptedlen, (unsigned char *) decoded, decodedlen); + if (res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "decrypt: attempt to decrypt failed"); + return res; + } + *out = (char *) decrypted; + + res = apr_evp_crypt_finish(e, decrypted + decryptedlen, &tlen); + if (APR_SUCCESS != res) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "attempt to finish the decryption failed"); + apr_evp_factory_cleanup(f); + apr_evp_crypt_cleanup(e); + return res; + } + decryptedlen += tlen; + decrypted[decryptedlen] = 0; + + return APR_SUCCESS; + +#else + ap_log_rerror(APLOG_MARK, APLOG_ERR, APR_ENOTIMPL, r, LOG_PREFIX + "crypto is not supported by APR on this platform"); + return APR_ENOTIMPL; +#endif +} + + +/** + * Crypto encoding for the session. + * + * @param r The request pointer. + * @param z A pointer to where the session will be written. + */ +AP_DECLARE(int) ap_session_crypto_encode(request_rec * r, session_rec * z) +{ + + char *encoded = NULL; + apr_status_t res; + session_crypto_dir_conf *conf = ap_get_module_config(r->per_dir_config, + &session_crypto_module); + + if (conf->passphrase_set || conf->certfile_set) { + res = encrypt_string(r, z->encoded, &encoded); + if (res != OK) { + ap_log_rerror(APLOG_MARK, APLOG_DEBUG, res, r, LOG_PREFIX + "encrypt session failed"); + return res; + } + z->encoded = encoded; + } + + return OK; + +} + +/** + * Crypto decoding for the session. + * + * @param r The request pointer. + * @param z A pointer to where the session will be written. + */ +AP_DECLARE(int) ap_session_crypto_decode(request_rec * r, session_rec * z) +{ + + char *encoded = NULL; + apr_status_t res; + session_crypto_dir_conf *conf = ap_get_module_config(r->per_dir_config, + &session_crypto_module); + + if ((conf->passphrase_set || conf->certfile_set) && z->encoded) { + res = decrypt_string(r, z->encoded, &encoded); + if (res != APR_SUCCESS) { + ap_log_rerror(APLOG_MARK, APLOG_ERR, res, r, LOG_PREFIX + "decrypt session failed, wrong passphrase?"); + return res; + } + z->encoded = encoded; + } + + return OK; + +} + + + + +static void *create_session_crypto_dir_config(apr_pool_t * p, char *dummy) +{ + session_crypto_dir_conf *new = + (session_crypto_dir_conf *) apr_pcalloc(p, sizeof(session_crypto_dir_conf)); + + /* default cipher AES256-SHA */ + new->cipher = DEFAULT_CIPHER; + new->cipher_set = 1; + + new->digest = DEFAULT_DIGEST; + new->digest_set = 1; + + /* initialise SSL */ + apr_ssl_init(); + + return (void *) new; +} + +static void *merge_session_crypto_dir_config(apr_pool_t * p, void *basev, void *addv) +{ + session_crypto_dir_conf *new = (session_crypto_dir_conf *) apr_pcalloc(p, sizeof(session_crypto_dir_conf)); + session_crypto_dir_conf *add = (session_crypto_dir_conf *) addv; + session_crypto_dir_conf *base = (session_crypto_dir_conf *) basev; + + new->passphrase = (add->passphrase_set == 0) ? base->passphrase : add->passphrase; + new->passphrase_set = add->passphrase_set || base->passphrase_set; + new->certfile = (add->certfile_set == 0) ? base->certfile : add->certfile; + new->certfile_set = add->certfile_set || base->certfile_set; + new->keyfile = (add->keyfile_set == 0) ? base->keyfile : add->keyfile; + new->keyfile_set = add->keyfile_set || base->keyfile_set; + new->cipher = (add->cipher_set == 0) ? base->cipher : add->cipher; + new->cipher_set = add->cipher_set || base->cipher_set; + new->digest = (add->digest_set == 0) ? base->digest : add->digest; + new->digest_set = add->digest_set || base->digest_set; + new->engine = (add->engine_set == 0) ? base->engine : add->engine; + new->engine_set = add->engine_set || base->engine_set; + + return new; +} + +static const char *check_file(cmd_parms * cmd, const char **file) +{ + apr_finfo_t finfo; + const char *filepath = ap_server_root_relative(cmd->pool, *file); + + if (!filepath) { + return apr_pstrcat(cmd->pool, cmd->directive->directive, + ": Invalid file path ", *file, NULL); + } + if (apr_stat(&finfo, filepath, + APR_FINFO_TYPE | APR_FINFO_SIZE, cmd->pool) != 0 || + finfo.filetype != APR_REG || finfo.size <= 0) { + return apr_pstrcat(cmd->pool, cmd->directive->directive, + ": File empty or missing ", *file, NULL); + } + *file = filepath; + + return NULL; +} + +static const char *set_crypto_passphrase(cmd_parms * cmd, void *config, const char *passphrase) +{ + session_crypto_dir_conf *conf = (session_crypto_dir_conf *) config; + conf->passphrase = passphrase; + conf->passphrase_set = 1; + return NULL; +} + +static const char *set_crypto_certificate_file(cmd_parms * cmd, void *config, const char *file) +{ + const char *res = check_file(cmd, &file); + if (!res) { + session_crypto_dir_conf *conf = (session_crypto_dir_conf *) config; + conf->certfile = file; + conf->certfile_set = 1; + } + return res; +} + +static const char *set_crypto_certificate_keyfile(cmd_parms * cmd, void *config, const char *file) +{ + const char *res = check_file(cmd, &file); + if (!res) { + session_crypto_dir_conf *conf = (session_crypto_dir_conf *) config; + conf->keyfile = file; + conf->keyfile_set = 1; + } + return res; +} + +static const char *set_crypto_cipher(cmd_parms * cmd, void *config, const char *cipher) +{ + session_crypto_dir_conf *conf = (session_crypto_dir_conf *) config; + conf->cipher = cipher; + conf->cipher_set = 1; + return NULL; +} + +static const char *set_crypto_digest(cmd_parms * cmd, void *config, const char *digest) +{ + session_crypto_dir_conf *conf = (session_crypto_dir_conf *) config; + conf->digest = digest; + conf->digest_set = 1; + return NULL; +} + +static const char *set_crypto_engine(cmd_parms * cmd, void *config, const char *engine) +{ + session_crypto_dir_conf *conf = (session_crypto_dir_conf *) config; + conf->engine = engine; + conf->engine_set = 1; + return NULL; +} + + +static const command_rec session_crypto_cmds[] = +{ + AP_INIT_TAKE1("SessionCryptoPassphrase", set_crypto_passphrase, NULL, RSRC_CONF|OR_AUTHCFG, + "The passphrase used to encrypt cookies"), + AP_INIT_TAKE1("SessionCryptoCertificateFile", set_crypto_certificate_file, NULL, RSRC_CONF|OR_AUTHCFG, + "The name of a certificate whose public key will be used to encrypt cookies"), + AP_INIT_TAKE1("SessionCryptoCertificateKeyFile", set_crypto_certificate_keyfile, NULL, RSRC_CONF|OR_AUTHCFG, + "The name of a private key which will be used to decrypt cookies"), + AP_INIT_TAKE1("SessionCryptoCipher", set_crypto_cipher, NULL, RSRC_CONF|OR_AUTHCFG, + "The cipher used to encrypt cookies. Defaults to " DEFAULT_CIPHER), + AP_INIT_TAKE1("SessionCryptoDigest", set_crypto_digest, NULL, RSRC_CONF|OR_AUTHCFG, + "The digest used to encrypt cookies. Defaults to " DEFAULT_DIGEST), + AP_INIT_TAKE1("SessionCryptoEngine", set_crypto_engine, NULL, RSRC_CONF|OR_AUTHCFG, + "The optional engine used to encrypt cookies, if supported by the underlying crypto " + "toolkit"), + {NULL} +}; + +static void register_hooks(apr_pool_t * p) +{ + ap_hook_session_encode(ap_session_crypto_encode, NULL, NULL, APR_HOOK_LAST); + ap_hook_session_decode(ap_session_crypto_decode, NULL, NULL, APR_HOOK_FIRST); +} + +module AP_MODULE_DECLARE_DATA session_crypto_module = +{ + STANDARD20_MODULE_STUFF, + create_session_crypto_dir_config, /* dir config creater */ + merge_session_crypto_dir_config, /* dir merger --- default is to + * override */ + NULL, /* server config */ + NULL, /* merge server config */ + session_crypto_cmds, /* command apr_table_t */ + register_hooks /* register hooks */ +}; -- 2.40.0