introduced extension hooks framework

9 files changed, 127 insertions, 28 deletions

diff --git a/include/Makefile.am b/include/Makefile.am
index b014752..72931eb 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1,11 +1,12 @@
 nobase_include_HEADERS = \
 	opkele/acconfig.h \
 	opkele/opkele-config.h \
 	opkele/types.h \
 	opkele/association.h \
 	opkele/exception.h \
 	opkele/server.h \
-	opkele/consumer.h
+	opkele/consumer.h \
+	opkele/extension.h
 EXTRA_DIST = \
 	opkele/data.h \
 	opkele/util.h
diff --git a/include/opkele/consumer.h b/include/opkele/consumer.h
index 9932315..f9939cf 100644
--- a/include/opkele/consumer.h
+++ b/include/opkele/consumer.h
@@ -1,142 +1,145 @@
 #ifndef __OPKELE_CONSUMER_H
 #define __OPKELE_CONSUMER_H
 
 #include <opkele/types.h>
+#include <opkele/extension.h>
 
 /**
  * @file
  * @brief OpenID consumer-side functionality
  */
 
 /**
  * @brief the main opkele namespace
  */
 namespace opkele {
 
     /**
      * implementation of basic consumer functionality
      */
     class consumer_t {
 	public:
 
 	    /**
 	     * store association. The function should be overridden in the real
 	     * implementation to provide persistent associations store.
 	     * @param server the OpenID server
 	     * @param handle association handle
 	     * @param secret the secret associated with the server and handle
 	     * @param expires_in the number of seconds until the handle is expired
 	     * @return the auto_ptr<> for the newly allocated association_t object
 	     */
 	    virtual assoc_t store_assoc(const string& server,const string& handle,const secret_t& secret,int expires_in) = 0;
 	    /**
 	     * retrieve stored association. The function should be overridden
 	     * in the real implementation to provide persistent assocations
 	     * store.
 	     * @param server the OpenID server
 	     * @param handle association handle
 	     * @return the autho_ptr<> for the newly allocated association_t object
 	     * @throw failed_lookup in case of error
 	     */
 	    virtual assoc_t retrieve_assoc(const string& server,const string& handle) = 0;
 	    /**
 	     * invalidate stored association. The function should be overridden
 	     * in the real implementation of the consumer.
 	     * @param server the OpenID server
 	     * @param handle association handle
 	     */
 	    virtual void invalidate_assoc(const string& server,const string& handle) = 0;
 	    /**
 	     * retrieve any unexpired association for the server. If the
 	     * function is not overridden in the real implementation, the new
 	     * association will be established for each request.
 	     * @param server the OpenID server
 	     * @return the auto_ptr<> for the newly allocated association_t object
 	     * @throw failed_lookup in case of absence of the handle
 	     */
 	    virtual assoc_t find_assoc(const string& server);
 
 	    /**
 	     * retrieve the metainformation contained in link tags from the
 	     * page pointed by url. the function may implement caching of the
 	     * information.
 	     * @param url url to harvest for link tags
 	     * @param server reference to the string object where to put
 	     * openid.server value
 	     * @param delegate reference to the string object where to put the
 	     * openid.delegate value (if any)
 	     */
 	    virtual void retrieve_links(const string& url,string& server,string& delegate);
 
 	    /**
 	     * perform the associate request to OpenID server.
 	     * @param server the OpenID server
 	     * @return the auto_ptr<> for the newly allocated association_t
 	     * object, representing established association
 	     * @throw exception in case of error
 	     */
 	    assoc_t associate(const string& server);
 	    /**
 	     * prepare the parameters for the checkid_immediate
 	     * request.
 	     * @param identity the identity to verify
 	     * @param return_to the return_to url to pass with the request
 	     * @param trust_root the trust root to advertise with the request
+	     * @param ext pointer to an extension(s) hooks object
 	     * @return the location string
 	     * @throw exception in case of error
 	     */
-	    string checkid_immediate(const string& identity,const string& return_to,const string& trust_root="");
+	    string checkid_immediate(const string& identity,const string& return_to,const string& trust_root="",extension_t *ext=0);
 	    /**
 	     * prepare the parameters for the checkid_setup
 	     * request.
 	     * @param identity the identity to verify
 	     * @param return_to the return_to url to pass with the request
 	     * @param trust_root the trust root to advertise with the request
+	     * @param ext pointer to an extension(s) hooks object
 	     * @return the location string
 	     * @throw exception in case of error
 	     */
-	    string checkid_setup(const string& identity,const string& return_to,const string& trust_root="");
+	    string checkid_setup(const string& identity,const string& return_to,const string& trust_root="",extension_t *ext=0);
 	    /**
 	     * the actual implementation behind checkid_immediate() and
 	     * checkid_setup() functions.
 	     * @param mode checkid_* mode - either mode_checkid_immediate or mode_checkid_setup
 	     * @param identity the identity to verify
 	     * @param return_to the return_to url to pass with the request
 	     * @param trust_root the trust root to advertise with the request
+	     * @param ext pointer to an extension(s) hooks object
 	     * @return the location string
 	     * @throw exception in case of error
 	     */
-	    string checkid_(mode_t mode,const string& identity,const string& return_to,const string& trust_root="");
+	    string checkid_(mode_t mode,const string& identity,const string& return_to,const string& trust_root="",extension_t *ext=0);
 	    /**
 	     * verify the id_res response
 	     * @param pin the response parameters
-	     * @param identity the identity being checked (if not specified, extracted
-	     * from the openid.identity parameter
-	     * @throw id_res_mismatch in case of signature
-	     * mismatch
-	     * @throw id_res_setup in case of
-	     * openid.user_setup_url failure (supposedly
-	     * checkid_immediate only)
+	     * @param identity the identity being checked (if not specified,
+	     * @param ext pointer to an extension(s) hooks object
+	     * extracted from the openid.identity parameter
+	     * @throw id_res_mismatch in case of signature mismatch
+	     * @throw id_res_setup in case of openid.user_setup_url failure
+	     * (supposedly checkid_immediate only)
 	     * @throw id_res_failed in case of failure
 	     * @throw exception in case of other failures
 	     */
-	    void id_res(const params_t& pin,const string& identity="");
+	    void id_res(const params_t& pin,const string& identity="",extension_t *ext=0);
 	    /**
 	     * perform a check_authentication request.
 	     * @param server the OpenID server
 	     * @param p request parameters
 	     */
 	    void check_authentication(const string& server,const params_t& p);
 
 	    /**
 	     * make URL canonical, by adding http:// and trailing slash, if needed.
 	     * @param url
 	     * @return canonicalized url
 	     */
 	    static string canonicalize(const string& url);
 
     };
 
 }
 
 #endif /* __OPKELE_CONSUMER_H */
diff --git a/include/opkele/exception.h b/include/opkele/exception.h
index c5f5811..9fc9bd3 100644
--- a/include/opkele/exception.h
+++ b/include/opkele/exception.h
@@ -1,210 +1,220 @@
 #ifndef __OPKELE_EXCEPTION_H
 #define __OPKELE_EXCEPTION_H
 
 /**
  * @file
  * @brief opkele exceptions
  */
 
 #include <curl/curl.h>
 
 #include <opkele/opkele-config.h>
 #ifdef OPKELE_HAVE_KONFORKA
 # include <konforka/exception.h>
 /**
  * the exception parameters declaration
  */
 # define OPKELE_E_PARS const string& fi,const string&fu,int l,const string& w
 /**
  * the exception parameters list to pass to constructor
  */
 # define OPKELE_E_CONS_ fi,fu,l,
 /**
  * the exception codepoint specification
  */
 # define OPKELE_CP_ CODEPOINT,
 /**
  * the simple rethrow of konforka-based exception
  */
 # define OPKELE_RETHROW catch(konforka::exception& e) { e.see(CODEPOINT); throw }
 #else /* OPKELE_HAVE_KONFORKA */
 # include <exception>
 # include <string>
 /**
  * the exception parameter declaration
  */
 # define OPKELE_E_PARS const string& w
 /**
  * the dummy prefix for exception parameters list to prepend in the absence of
  * konforka library
  */
 # define OPKELE_E_CONS_ 
 /**
  * the dummy placeholder for konforka exception codepoint specification
  */
 # define OPKELE_CP_
 /**
  * the dummy define for the konforka-based rethrow of exception
  */
 # define OPKELE_RETHROW
 #endif /* OPKELE_HAVE_KONFORKA */
 /**
  * the exception parameters list to pass to constructor
  */
 # define OPKELE_E_CONS OPKELE_E_CONS_ w
 
 /*
  * @brief the main opkele namespace
  */
 namespace opkele {
     using std::string;
 
     /**
      * the base opkele exception class
      */
     class exception : public
 #   ifdef OPKELE_HAVE_KONFORKA
 		      konforka::exception
 #   else
                       std::exception
 #   endif
     {
 	public:
 #           ifdef OPKELE_HAVE_KONFORKA
 	    explicit
 		exception(const string& fi,const string& fu,int l,const string& w)
 		    : konforka::exception(fi,fu,l,w) { }
 #           else /* OPKELE_HAVE_KONFORKA */
 	    string _what;
 	    explicit
 		exception(const string& w)
 		    : _what(w) { } 
 	    virtual ~exception() throw();
 	    virtual const char * what() const throw();
 #           endif /* OPKELE_HAVE_KONFORKA */
     };
 
     /**
      * thrown in case of failed conversion
      */
     class failed_conversion : public exception {
 	public:
 	    failed_conversion(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
     /**
      * thrown in case of failed lookup (either parameter or persistent store)
      */
     class failed_lookup : public exception {
 	public:
 	    failed_lookup(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
     /**
      * thrown in case of bad input (either local or network)
      */
     class bad_input : public exception {
 	public:
 	    bad_input(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
 
     /**
      * thrown on failed assertion
      */
     class failed_assertion : public exception {
 	public:
 	    failed_assertion(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
 
     /**
      * thrown if the handle being retrieved is invalid
      */
     class invalid_handle : public exception {
 	public:
 	    invalid_handle(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
     /**
      * thrown if the handle passed to check_authentication request is not
      * stateless
      */
     class stateful_handle : public exception {
 	public:
 	    stateful_handle(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
 
     /**
      * thrown if check_authentication request fails
      */
     class failed_check_authentication : public exception {
 	public:
 	    failed_check_authentication(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
 
     /**
      * thrown if the id_res request result is negative
      */
     class id_res_failed : public exception {
 	public:
 	    id_res_failed(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
     /**
      * thrown if the user_setup_url is provided with negative response
      */
     class id_res_setup : public id_res_failed {
 	public:
 	    string setup_url;
 	    id_res_setup(OPKELE_E_PARS,const string& su)
 		: id_res_failed(OPKELE_E_CONS), setup_url(su) { }
 	    ~id_res_setup() throw() { }
     };
     /**
      * thrown in case of signature mismatch
      */
     class id_res_mismatch : public id_res_failed {
 	public:
 	    id_res_mismatch(OPKELE_E_PARS)
 		: id_res_failed(OPKELE_E_CONS) { }
     };
 
     /**
      * openssl malfunction occured
      */
     class exception_openssl : public exception {
 	public:
 	    unsigned long _error;
 	    string _ssl_string;
 	    exception_openssl(OPKELE_E_PARS);
 	    ~exception_openssl() throw() { }
     };
 
     /**
      * network operation related error occured
      */
     class exception_network : public exception {
 	public:
 	    exception_network(OPKELE_E_PARS)
 		: exception(OPKELE_E_CONS) { }
     };
 
     /**
      * network operation related error occured, specifically, related to
      * libcurl
      */
     class exception_curl : public exception_network {
 	public:
 	    CURLcode _error;
 	    string _curl_string;
 	    exception_curl(OPKELE_E_PARS);
 	    exception_curl(OPKELE_E_PARS,CURLcode e);
 	    ~exception_curl() throw() { }
     };
 
+    /**
+     * not implemented (think pure virtual) member function executed, signfies
+     * programmer error
+     */
+    class not_implemented : public exception {
+	public:
+	    not_implemented(OPKELE_E_PARS)
+		: exception(OPKELE_E_CONS) { }
+    };
+
 }
 
 #endif /* __OPKELE_EXCEPTION_H */
diff --git a/include/opkele/extension.h b/include/opkele/extension.h
new file mode 100644
index 0000000..3fb5f6e
--- a/dev/null
+++ b/include/opkele/extension.h
@@ -0,0 +1,59 @@
+#ifndef __OPKELE_EXTENSIONS_H
+#define __OPKELE_EXTENSIONS_H
+
+/**
+ * @file
+ * @brief extensions framework basics
+ */
+
+#include <opkele/types.h>
+
+/**
+ * @brief the main opkele namespace
+ */
+namespace opkele {
+
+    /**
+     * OpenID consumer extension hooks base class
+     */
+    class extension_t {
+	public:
+	    /**
+	     * hook called by consumer before submitting data to OpenID server.
+	     * It is supposed to manipulate parameters list.
+	     * @param p parameters about to be submitted to server
+	     * @param identity identity being verified. It may differ from the
+	     * one available in parameters list in case of delegation
+	     */
+	    virtual void checkid_hook(params_t& p,const string& identity);
+	    /**
+	     * hook called by consumer after identity information received from
+	     * OpenID server is verified.
+	     * @param p parameters received from server
+	     * @param sp signed parameters received from server with 'openid.'
+	     * leader stripped
+	     * @param identity identity confirmed. May differ from the one
+	     * available in parameters list in case of delegation. May also be
+	     * empty which means - extract one from parameters
+	     */
+	    virtual void id_res_hook(const params_t& p,const params_t& sp,const string& identity);
+
+	    /**
+	     * hook called by server before returning information to consumer.
+	     * The hook may manipulate output parameters. It is important to
+	     * note that modified pout["signed"] is used for signing response.
+	     * @param pin request parameters list
+	     * @param put response parameters list
+	     */
+	    virtual void checkid_hook(const params_t& pin,params_t& pout);
+
+	    /**
+	     * Casts the object to pointer to itself. For convenient passing
+	     * of pointer.
+	     */
+	    operator extension_t*(void) { return this; }
+    };
+
+}
+
+#endif /* __OPKELE_EXTENSIONS_H */
diff --git a/include/opkele/server.h b/include/opkele/server.h
index fe07448..bf131d8 100644
--- a/include/opkele/server.h
+++ b/include/opkele/server.h
@@ -1,95 +1,99 @@
 #ifndef __OPKELE_SERVER_H
 #define __OPKELE_SERVER_H
 
 /**
  * @file
  * @brief OpenID server-side functionality
  */
 
 #include <opkele/types.h>
+#include <opkele/extension.h>
 
 /**
  * @brief the main opkele namespace
  */
 namespace opkele {
 
     /**
      * implementation of basic server functionality
      */
     class server_t {
 	public:
 
 	    /**
 	     * allocate the new association. The function should be overridden
 	     * in the real implementation to provide persistent assocations
 	     * store.
 	     * @param mode the mode of request being processed to base the
 	     * statelessness of the association upon
 	     * @return the auto_ptr<> for the newly allocated association_t object
 	     */
 	    virtual assoc_t alloc_assoc(mode_t mode) = 0;
 	    /**
 	     * retrieve the association. The function should be overridden in
 	     * the reqal implementation to provide persistent assocations
 	     * store.
 	     * @param h association handle
 	     * @return the auto_ptr<> for the newly allocated association_t object
 	     * @throw failed_lookup in case of failure
 	     */
 	    virtual assoc_t retrieve_assoc(const string& h) = 0;
 
 	    /**
 	     * validate the identity.
 	     * @param assoc association object
 	     * @param pin incoming request parameters
 	     * @param identity being verified
 	     * @param trust_root presented in the request
 	     * @throw exception if identity can not be confirmed
 	     */
 	    virtual void validate(const association_t& assoc,const params_t& pin,const string& identity,const string& trust_root) = 0;
 
 
 	    /**
 	     * process the associate request.
 	     * @param pin the incoming request parameters
 	     * @param pout the store for the response parameters
 	     */
 	    void associate(const params_t& pin,params_t& pout);
 	    /**
 	     * process the checkid_immediate request.
 	     * @param pin the incoming request parameters
 	     * @param return_to reference to the object to store return_to url to
 	     * @param pout the response parameters
+	     * @param ext pointer to the extension hooks object
 	     * @throw exception in case of errors or negative reply
 	     */
-	    void checkid_immediate(const params_t& pin,string& return_to,params_t& pout);
+	    void checkid_immediate(const params_t& pin,string& return_to,params_t& pout,extension_t *ext=0);
 	    /**
 	     * process the checkid_setup request.
 	     * @param pin the incoming request parameters
 	     * @param return_to reference to the object to store return_to url to
 	     * @param pout the response parameters
+	     * @param ext pointer to the extension hooks object
 	     * @throw exception in case of errors or negative reply
 	     */
-	    void checkid_setup(const params_t& pin,string& return_to,params_t& pout);
+	    void checkid_setup(const params_t& pin,string& return_to,params_t& pout,extension_t *ext=0);
 	    /**
 	     * the actual functionality behind checkid_immediate() and
 	     * checkid_setup()
 	     * @param mode the request being processed (either
 	     * mode_checkid_immediate or mode_checkid_setup)
 	     * @param pin the incoming request parameters
 	     * @param return_to reference to the object to store return_to url to
 	     * @param pout the response parameters
+	     * @param ext pointer to the extension hooks object
 	     * @throw exception in case of errors or negative reply
 	     */
-	    void checkid_(mode_t mode,const params_t& pin,string& return_to,params_t& pout);
+	    void checkid_(mode_t mode,const params_t& pin,string& return_to,params_t& pout,extension_t *ext=0);
 	    /**
 	     * process the check_authentication request.
 	     * @param pin incoming request parameters
 	     * @param pout response parameters
 	     */
 	    void check_authentication(const params_t& pin,params_t& pout);
     };
 
 }
 
 #endif /* __OPKELE_SERVER_H */
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 6f3f9f3..69c749e 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -1,24 +1,25 @@
 lib_LTLIBRARIES = libopkele.la
 
 INCLUDES = \
 	   -I${top_srcdir}/include/ \
 	   ${KONFORKA_CFLAGS} \
 	   ${OPENSSL_CFLAGS} \
 	   ${MIMETIC_CFLAGS} \
 	   ${LIBCURL_CPPFLAGS} \
 	   ${PCREPP_CFLAGS}
 LDADD = \
 	${LIBCURL} \
 	${PCREPP_LIBS} \
 	${MIMETIC_LIBS} \
 	${OPENSSL_LIBS} \
 	${KONFORKA_LIBS}
 
 libopkele_la_SOURCES = \
 		       params.cc \
 		       util.cc \
 		       server.cc \
 		       secret.cc \
 		       data.cc \
 		       consumer.cc \
-		       exception.cc
+		       exception.cc \
+		       extension.cc
diff --git a/lib/consumer.cc b/lib/consumer.cc
index bb6358c..10c2fa0 100644
--- a/lib/consumer.cc
+++ b/lib/consumer.cc
@@ -1,348 +1,352 @@
 #include <algorithm>
 #include <opkele/util.h>
 #include <opkele/exception.h>
 #include <opkele/data.h>
 #include <opkele/consumer.h>
 #include <openssl/sha.h>
 #include <openssl/hmac.h>
 #include <mimetic/mimetic.h>
 #include <curl/curl.h>
 #include <pcre++.h>
 
 #include <iostream>
 
 /* silly mimetic */
 #undef PACKAGE
 #undef PACKAGE_BUGREPORT
 #undef PACKAGE_NAME
 #undef PACKAGE_STRING
 #undef PACKAGE_TARNAME
 #undef PACKAGE_VERSION
 #undef VERSION
 
 #include "config.h"
 
 namespace opkele {
     using namespace std;
 
     class curl_t {
 	public:
 	    CURL *_c;
 
 	    curl_t() : _c(0) { }
 	    curl_t(CURL *c) : _c(c) { }
 	    ~curl_t() throw() { if(_c) curl_easy_cleanup(_c); }
 
 	    curl_t& operator=(CURL *c) { if(_c) curl_easy_cleanup(_c); _c=c; return *this; }
 
 	    operator const CURL*(void) const { return _c; }
 	    operator CURL*(void) { return _c; }
     };
 
     static CURLcode curl_misc_sets(CURL* c) {
 	CURLcode r;
 	(r=curl_easy_setopt(c,CURLOPT_FOLLOWLOCATION,1))
 	|| (r=curl_easy_setopt(c,CURLOPT_MAXREDIRS,5))
 	|| (r=curl_easy_setopt(c,CURLOPT_DNS_CACHE_TIMEOUT,120))
 	|| (r=curl_easy_setopt(c,CURLOPT_DNS_USE_GLOBAL_CACHE,1))
 	|| (r=curl_easy_setopt(c,CURLOPT_USERAGENT,PACKAGE_NAME"/"PACKAGE_VERSION))
 	|| (r=curl_easy_setopt(c,CURLOPT_TIMEOUT,20))
 	;
 	return r;
     }
 
     static size_t _curl_tostring(void *ptr,size_t size,size_t nmemb,void *stream) {
 	string *str = (string*)stream;
 	size_t bytes = size*nmemb;
 	size_t get = min(16384-str->length(),bytes);
 	str->append((const char*)ptr,get);
 	return get;
     }
 
     assoc_t consumer_t::associate(const string& server) {
 	util::dh_t dh = DH_new();
 	if(!dh)
 	    throw exception_openssl(OPKELE_CP_ "failed to DH_new()");
 	dh->p = util::dec_to_bignum(data::_default_p);
 	dh->g = util::dec_to_bignum(data::_default_g);
 	if(!DH_generate_key(dh))
 	    throw exception_openssl(OPKELE_CP_ "failed to DH_generate_key()");
 	string request = 
 	    "openid.mode=associate"
 	    "&openid.assoc_type=HMAC-SHA1"
 	    "&openid.session_type=DH-SHA1"
 	    "&openid.dh_consumer_public=";
 	request += util::url_encode(util::bignum_to_base64(dh->pub_key));
 	curl_t curl = curl_easy_init();
 	if(!curl)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_init()");
 	string response;
 	CURLcode r;
 	(r=curl_misc_sets(curl))
 	|| (r=curl_easy_setopt(curl,CURLOPT_URL,server.c_str()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_POST,1))
 	|| (r=curl_easy_setopt(curl,CURLOPT_POSTFIELDS,request.data()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,request.length()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,_curl_tostring))
 	|| (r=curl_easy_setopt(curl,CURLOPT_WRITEDATA,&response))
 	;
 	if(r)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_setopt()",r);
 	if(r=curl_easy_perform(curl))
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_perform()",r);
 	params_t p; p.parse_keyvalues(response);
 	if(p.has_param("assoc_type") && p.get_param("assoc_type")!="HMAC-SHA1")
 	    throw bad_input(OPKELE_CP_ "unsupported assoc_type");
 	string st;
 	if(p.has_param("session_type")) st = p.get_param("session_type");
 	if((!st.empty()) && st!="DH-SHA1")
 	    throw bad_input(OPKELE_CP_ "unsupported session_type");
 	secret_t secret;
 	if(st.empty()) {
 	    secret.from_base64(p.get_param("mac_key"));
 	}else{
 	    util::bignum_t s_pub = util::base64_to_bignum(p.get_param("dh_server_public"));
 	    vector<unsigned char> ck(DH_size(dh));
 	    int cklen = DH_compute_key(&(ck.front()),s_pub,dh);
 	    if(cklen<0)
 		throw exception_openssl(OPKELE_CP_ "failed to DH_compute_key()");
 	    ck.resize(cklen);
 	    // OpenID algorithm requires extra zero in case of set bit here
 	    if(ck[0]&0x80) ck.insert(ck.begin(),1,0);
 	    unsigned char key_sha1[SHA_DIGEST_LENGTH];
 	    SHA1(&(ck.front()),ck.size(),key_sha1);
 	    secret.enxor_from_base64(key_sha1,p.get_param("enc_mac_key"));
 	}
 	int expires_in = 0;
 	if(p.has_param("expires_in")) {
 	    expires_in = util::string_to_long(p.get_param("expires_in"));
 	}else if(p.has_param("issued") && p.has_param("expiry")) {
 	    expires_in = util::w3c_to_time(p.get_param("expiry"))-util::w3c_to_time(p.get_param("issued"));
 	}else
 	    throw bad_input(OPKELE_CP_ "no expiration information");
 	return store_assoc(server,p.get_param("assoc_handle"),secret,expires_in);
     }
 
-    string consumer_t::checkid_immediate(const string& identity,const string& return_to,const string& trust_root) {
-	return checkid_(mode_checkid_immediate,identity,return_to,trust_root);
+    string consumer_t::checkid_immediate(const string& identity,const string& return_to,const string& trust_root,extension_t *ext) {
+	return checkid_(mode_checkid_immediate,identity,return_to,trust_root,ext);
     }
-    string consumer_t::checkid_setup(const string& identity,const string& return_to,const string& trust_root) {
-	return checkid_(mode_checkid_setup,identity,return_to,trust_root);
+    string consumer_t::checkid_setup(const string& identity,const string& return_to,const string& trust_root,extension_t *ext) {
+	return checkid_(mode_checkid_setup,identity,return_to,trust_root,ext);
     }
-    string consumer_t::checkid_(mode_t mode,const string& identity,const string& return_to,const string& trust_root) {
+    string consumer_t::checkid_(mode_t mode,const string& identity,const string& return_to,const string& trust_root,extension_t *ext) {
 	params_t p;
 	if(mode==mode_checkid_immediate)
 	    p["mode"]="checkid_immediate";
 	else if(mode==mode_checkid_setup)
 	    p["mode"]="checkid_setup";
 	else
 	    throw bad_input(OPKELE_CP_ "unknown checkid_* mode");
 	string iurl = canonicalize(identity);
 	string server, delegate;
 	retrieve_links(iurl,server,delegate);
 	p["identity"] = delegate.empty()?iurl:delegate;
 	if(!trust_root.empty())
 	    p["trust_root"] = trust_root;
 	p["return_to"] = return_to;
 	try {
 	    try {
 		string ah = find_assoc(server)->handle();
 		p["assoc_handle"] = ah;
 	    }catch(failed_lookup& fl) {
 		string ah = associate(server)->handle();
 		p["assoc_handle"] = ah;
 	    }
 	}catch(exception& e) { }
+	if(ext) ext->checkid_hook(p,identity);
 	return p.append_query(server);
     }
 
-    void consumer_t::id_res(const params_t& pin,const string& identity) {
+    void consumer_t::id_res(const params_t& pin,const string& identity,extension_t *ext) {
 	if(pin.has_param("openid.user_setup_url"))
 	    throw id_res_setup(OPKELE_CP_ "assertion failed, setup url provided",pin.get_param("openid.user_setup_url"));
 	string server,delegate;
 	retrieve_links(identity.empty()?pin.get_param("openid.identity"):canonicalize(identity),server,delegate);
+	params_t ps;
 	try {
 	    assoc_t assoc = retrieve_assoc(server,pin.get_param("openid.assoc_handle"));
 	    const string& sigenc = pin.get_param("openid.sig");
 	    mimetic::Base64::Decoder b;
 	    vector<unsigned char> sig;
 	    mimetic::decode(
 		    sigenc.begin(),sigenc.end(), b,
 		    back_insert_iterator<vector<unsigned char> >(sig) );
 	    const string& slist = pin.get_param("openid.signed");
 	    string kv;
 	    string::size_type p = 0;
 	    while(true) {
 		string::size_type co = slist.find(',',p);
 		string f = (co==string::npos)?slist.substr(p):slist.substr(p,co-p);
 		kv += f;
 		kv += ':';
 		f.insert(0,"openid.");
 		kv += pin.get_param(f);
 		kv += '\n';
+		if(ext) ps[f.substr(sizeof("openid."))] = pin.get_param(f);
 		if(co==string::npos)
 		    break;
 		p = co+1;
 	    }
 	    secret_t secret = assoc->secret();
 	    unsigned int md_len = 0;
 	    unsigned char *md = HMAC(
 		    EVP_sha1(),
 		    &(secret.front()),secret.size(),
 		    (const unsigned char *)kv.data(),kv.length(),
 		    0,&md_len);
 	    if(sig.size()!=md_len || memcmp(&(sig.front()),md,md_len))
 		throw id_res_mismatch(OPKELE_CP_ "signature mismatch");
 	}catch(failed_lookup& e) { /* XXX: more specific? */
 	    const string& slist = pin.get_param("openid.signed");
 	    string::size_type pp = 0;
 	    params_t p;
 	    while(true) {
 		string::size_type co = slist.find(',',pp);
 		string f = "openid.";
 		f += (co==string::npos)?slist.substr(pp):slist.substr(pp,co-pp);
 		p[f] = pin.get_param(f);
 		if(co==string::npos)
 		    break;
 		pp = co+1;
 	    }
 	    p["openid.assoc_handle"] = pin.get_param("openid.assoc_handle");
 	    p["openid.sig"] = pin.get_param("openid.sig");
 	    p["openid.signed"] = pin.get_param("openid.signed");
 	    try {
 		string ih = pin.get_param("openid.invalidate_handle");
 		p["openid.invalidate_handle"] = ih;
 	    }catch(failed_lookup& fl) { }
 	    try {
 		check_authentication(server,p);
 	    }catch(failed_check_authentication& fca) {
 		throw id_res_failed(OPKELE_CP_ "failed to check_authentication()");
 	    }
 	}
+	if(ext) ext->id_res_hook(pin,ps,identity);
     }
 
     void consumer_t::check_authentication(const string& server,const params_t& p) {
 	string request = "openid.mode=check_authentication";
 	for(params_t::const_iterator i=p.begin();i!=p.end();++i) {
 	    if(i->first!="openid.mode") {
 		request += '&';
 		request += i->first;
 		request += '=';
 		request += util::url_encode(i->second);
 	    }
 	}
 	curl_t curl = curl_easy_init();
 	if(!curl)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_init()");
 	string response;
 	CURLcode r;
 	(r=curl_misc_sets(curl))
 	|| (r=curl_easy_setopt(curl,CURLOPT_URL,server.c_str()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_POST,1))
 	|| (r=curl_easy_setopt(curl,CURLOPT_POSTFIELDS,request.data()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_POSTFIELDSIZE,request.length()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,_curl_tostring))
 	|| (r=curl_easy_setopt(curl,CURLOPT_WRITEDATA,&response))
 	;
 	if(r)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_setopt()",r);
 	if(r=curl_easy_perform(curl))
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_perform()",r);
 	params_t pp; pp.parse_keyvalues(response);
 	if(pp.has_param("invalidate_handle"))
 	    invalidate_assoc(server,pp.get_param("invalidate_handle"));
 	if(pp.has_param("is_valid")) {
 	    if(pp.get_param("is_valid")=="true")
 		return;
 	}else if(pp.has_param("lifetime")) {
 	    if(util::string_to_long(pp.get_param("lifetime")))
 		return;
 	}
 	throw failed_check_authentication(OPKELE_CP_ "failed to verify response");
     }
 
     void consumer_t::retrieve_links(const string& url,string& server,string& delegate) {
 	server.erase();
 	delegate.erase();
 	curl_t curl = curl_easy_init();
 	if(!curl)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_init()");
 	string html;
 	CURLcode r;
 	(r=curl_misc_sets(curl))
 	|| (r=curl_easy_setopt(curl,CURLOPT_URL,url.c_str()))
 	|| (r=curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,_curl_tostring))
 	|| (r=curl_easy_setopt(curl,CURLOPT_WRITEDATA,&html))
 	;
 	if(r)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_setopt()",r);
 	r = curl_easy_perform(curl);
 	if(r && r!=CURLE_WRITE_ERROR)
 	    throw exception_curl(OPKELE_CP_ "failed to curl_easy_perform()",r);
 	pcrepp::Pcre bre("<body\\b",PCRE_CASELESS);
 	// strip out everything past body
 	if(bre.search(html))
 	    html.erase(bre.get_match_start());
 	pcrepp::Pcre hdre("<head[^>]*>",PCRE_CASELESS);
 	if(!hdre.search(html))
 	    throw bad_input(OPKELE_CP_ "failed to find head");
 	html.erase(0,hdre.get_match_end()+1);
 	pcrepp::Pcre lre("<link\\b([^>]+)>",PCRE_CASELESS),
 	    rre("\\brel=['\"]([^'\"]+)['\"]",PCRE_CASELESS),
 	    hre("\\bhref=['\"]([^'\"]+)['\"]",PCRE_CASELESS);
 	while(lre.search(html)) {
 	    string attrs = lre[0];
 	    html.erase(0,lre.get_match_end()+1);
 	    if(!(rre.search(attrs)&&hre.search(attrs)))
 		continue;
 	    if(rre[0]=="openid.server") {
 		server = hre[0];
 		if(!delegate.empty())
 		    break;
 	    }else if(rre[0]=="openid.delegate") {
 		delegate = hre[0];
 		if(!server.empty())
 		    break;
 	    }
 	}
 	if(server.empty())
 	    throw failed_assertion(OPKELE_CP_ "The location has no openid.server declaration");
     }
 
     assoc_t consumer_t::find_assoc(const string& server) {
 	throw failed_lookup(OPKELE_CP_ "no find_assoc() provided");
     }
 
     string consumer_t::canonicalize(const string& url) {
 	string rv = url;
 	// strip leading and trailing spaces
 	string::size_type i = rv.find_first_not_of(" \t\r\n");
 	if(i==string::npos)
 	    throw bad_input(OPKELE_CP_ "empty URL");
 	if(i)
 	    rv.erase(0,i);
 	i = rv.find_last_not_of(" \t\r\n");
 	assert(i!=string::npos);
 	if(i<(rv.length()-1))
 	    rv.erase(i+1);
 	// add missing http://
 	i = rv.find("://");
 	if(i==string::npos) { // primitive. but do we need more?
 	    rv.insert(0,"http://");
 	    i = sizeof("http://")-1;
 	}else{
 	    i += sizeof("://")-1;
 	}
 	string::size_type qm = rv.find('?',i);
 	string::size_type sl = rv.find('/',i);
 	if(qm!=string::npos) {
 	    if(sl==string::npos || sl>qm)
 		rv.insert(qm,1,'/');
 	}else{
 	    if(sl==string::npos)
 		rv += '/';
 	}
 	return rv;
     }
 
 }
diff --git a/lib/extension.cc b/lib/extension.cc
new file mode 100644
index 0000000..bd2195d
--- a/dev/null
+++ b/lib/extension.cc
@@ -0,0 +1,15 @@
+#include <opkele/exception.h>
+#include <opkele/extension.h>
+
+namespace opkele {
+
+    void extension_t::checkid_hook(params_t& p,const string& identity) {
+	throw not_implemented(OPKELE_CP_ "Consumer checkid_hook not implemented");
+    }
+    void id_res_hook(const params_t& p,const params_t& sp,const string& identity) {
+	throw not_implemented(OPKELE_CP_ "Consumer id_res_hook not implemented");
+    }
+    void checkid_hook(const params_t& pin,params_t& pout) {
+	throw not_implemented(OPKELE_CP_ "Server checkid_hook not implemented");
+    }
+}
diff --git a/lib/server.cc b/lib/server.cc
index 5eee1f3..8c29abb 100644
--- a/lib/server.cc
+++ b/lib/server.cc
@@ -1,171 +1,173 @@
 #include <vector>
 #include <openssl/sha.h>
 #include <openssl/hmac.h>
 #include <mimetic/mimetic.h>
 #include <opkele/util.h>
 #include <opkele/exception.h>
 #include <opkele/server.h>
 #include <opkele/data.h>
 
 namespace opkele {
     using namespace std;
 
     void server_t::associate(const params_t& pin,params_t& pout) {
 	util::dh_t dh;
 	util::bignum_t c_pub;
 	unsigned char key_sha1[SHA_DIGEST_LENGTH];
 	enum {
 	    sess_cleartext,
 	    sess_dh_sha1
 	} st = sess_cleartext;
 	if(
 		pin.has_param("openid.session_type")
 		&& pin.get_param("openid.session_type")=="DH-SHA1" ) {
 	    /* TODO: fallback to cleartext in case of exceptions here? */
 	    if(!(dh = DH_new()))
 		throw exception_openssl(OPKELE_CP_ "failed to DH_new()");
 	    c_pub = util::base64_to_bignum(pin.get_param("openid.dh_consumer_public"));
 	    if(pin.has_param("openid.dh_modulus"))
 		dh->p = util::base64_to_bignum(pin.get_param("openid.dh_modulus"));
 	    else
 		dh->p = util::dec_to_bignum(data::_default_p);
 	    if(pin.has_param("openid.dh_gen"))
 		dh->g = util::base64_to_bignum(pin.get_param("openid.dh_gen"));
 	    else
 		dh->g = util::dec_to_bignum(data::_default_g);
 	    if(!DH_generate_key(dh))
 		throw exception_openssl(OPKELE_CP_ "failed to DH_generate_key()");
 	    vector<unsigned char> ck(DH_size(dh));
 	    int cklen = DH_compute_key(&(ck.front()),c_pub,dh);
 	    if(cklen<0)
 		throw exception_openssl(OPKELE_CP_ "failed to DH_compute_key()");
 	    ck.resize(cklen);
 	    // OpenID algorithm requires extra zero in case of set bit here
 	    if(ck[0]&0x80) ck.insert(ck.begin(),1,0);
 	    SHA1(&(ck.front()),ck.size(),key_sha1);
 	    st = sess_dh_sha1;
 	}
 	assoc_t assoc = alloc_assoc(mode_associate);
 	time_t now = time(0);
 	pout.clear();
 	pout["assoc_type"] = assoc->assoc_type();
 	pout["assoc_handle"] = assoc->handle();
 	/* TODO: eventually remove deprecated stuff */
 	pout["issued"] = util::time_to_w3c(now);
 	pout["expiry"] = util::time_to_w3c(now+assoc->expires_in());
 	pout["expires_in"] = util::long_to_string(assoc->expires_in());
 	secret_t secret = assoc->secret();
 	switch(st) {
 	    case sess_dh_sha1:
 		pout["session_type"] = "DH-SHA1";
 		pout["dh_server_public"] = util::bignum_to_base64(dh->pub_key);
 		secret.enxor_to_base64(key_sha1,pout["enc_mac_key"]);
 		break;
 	    default:
 		secret.to_base64(pout["mac_key"]);
 		break;
 	}
     }
 
-    void server_t::checkid_immediate(const params_t& pin,string& return_to,params_t& pout) {
-	checkid_(mode_checkid_immediate,pin,return_to,pout);
+    void server_t::checkid_immediate(const params_t& pin,string& return_to,params_t& pout,extension_t *ext) {
+	checkid_(mode_checkid_immediate,pin,return_to,pout,ext);
     }
 
-    void server_t::checkid_setup(const params_t& pin,string& return_to,params_t& pout) {
-	checkid_(mode_checkid_setup,pin,return_to,pout);
+    void server_t::checkid_setup(const params_t& pin,string& return_to,params_t& pout,extension_t *ext) {
+	checkid_(mode_checkid_setup,pin,return_to,pout,ext);
     }
 
-    void server_t::checkid_(mode_t mode,const params_t& pin,string& return_to,params_t& pout) {
+    void server_t::checkid_(mode_t mode,const params_t& pin,string& return_to,params_t& pout,extension_t *ext) {
 	if(mode!=mode_checkid_immediate && mode!=mode_checkid_setup)
 	    throw bad_input(OPKELE_CP_ "invalid checkid_* mode");
 	pout.clear();
 	assoc_t assoc;
 	try {
 	    assoc = retrieve_assoc(pin.get_param("openid.assoc_handle"));
 	}catch(failed_lookup& fl) {
 	    // no handle specified or no valid handle found, going dumb
 	    assoc = alloc_assoc(mode_checkid_setup);
 	    if(pin.has_param("openid.assoc_handle"))
 		pout["invalidate_handle"]=pin.get_param("openid.assoc_handle");
 	}
 	string trust_root;
 	try {
 	    trust_root = pin.get_param("openid.trust_root");
 	}catch(failed_lookup& fl) { }
 	string identity = pin.get_param("openid.identity");
 	return_to = pin.get_param("openid.return_to");
 	validate(*assoc,pin,identity,trust_root);
 	pout["mode"] = "id_res";
 	pout["assoc_handle"] = assoc->handle();
 	if(pin.has_param("openid.assoc_handle") && assoc->stateless())
 	    pout["invalidate_handle"] = pin.get_param("openid.assoc_handle");
 	pout["identity"] = identity;
 	pout["return_to"] = return_to;
 	/* TODO: eventually remove deprecated stuff */
 	time_t now = time(0);
 	pout["issued"] = util::time_to_w3c(now);
 	pout["valid_to"] = util::time_to_w3c(now+120);
 	pout["exipres_in"] = "120";
-	pout.sign(assoc->secret(),pout["sig"],pout["signed"]="mode,identity,return_to");
+	pout["signed"]="mode,identity,return_to";
+	if(ext) ext->checkid_hook(pin,pout);
+	pout.sign(assoc->secret(),pout["sig"],pout["signed"]);
     }
 
     void server_t::check_authentication(const params_t& pin,params_t& pout) {
 	vector<unsigned char>  sig;
 	mimetic::Base64::Decoder b;
 	const string& sigenc = pin.get_param("openid.sig");
 	mimetic::decode(
 		sigenc.begin(),sigenc.end(), b,
 		back_insert_iterator<vector<unsigned char> >(sig));
 	assoc_t assoc;
 	try {
 	    assoc = retrieve_assoc(pin.get_param("openid.assoc_handle"));
 	}catch(failed_lookup& fl) {
 	    throw failed_assertion(OPKELE_CP_ "invalid handle or handle not specified");
 	}
 	if(!assoc->stateless())
 	    throw stateful_handle(OPKELE_CP_ "will not do check_authentication on a stateful handle");
 	const string& slist = pin.get_param("openid.signed");
 	string kv;
 	string::size_type p =0;
 	while(true) {
 	    string::size_type co = slist.find(',',p);
 	    string f = (co==string::npos)?slist.substr(p):slist.substr(p,co-p);
 	    kv += f;
 	    kv += ':';
 	    if(f=="mode")
 		kv += "id_res";
 	    else {
 		f.insert(0,"openid.");
 		kv += pin.get_param(f);
 	    }
 	    kv += '\n';
 	    if(co==string::npos)
 		break;
 	    p = co+1;
 	}
 	secret_t secret = assoc->secret();
 	unsigned int md_len = 0;
 	unsigned char *md = HMAC(
 		EVP_sha1(),
 		&(secret.front()),secret.size(),
 		(const unsigned char *)kv.data(),kv.length(),
 		0,&md_len);
 	pout.clear();
 	if(sig.size()==md_len && !memcmp(&(sig.front()),md,md_len)) {
 	    pout["is_valid"]="true";
 	    pout["lifetime"]="60"; /* TODO: eventually remove deprecated stuff */
 	}else{
 	    pout["is_valid"]="false";
 	    pout["lifetime"]="0"; /* TODO: eventually remove deprecated stuff */
 	}
 	if(pin.has_param("openid.invalidate_handle")) {
 	    string h = pin.get_param("openid.invalidate_handle");
 	    try {
 		assoc_t assoc = retrieve_assoc(h);
 	    }catch(invalid_handle& ih) {
 		pout["invalidate_handle"] = h;
 	    }catch(failed_lookup& fl) { }
 	}
     }
 
 }