initial commit of libopkele - OpenID support library

9 files changed, 844 insertions, 0 deletions

diff --git a/lib/.gitignore b/lib/.gitignore
new file mode 100644
index 0000000..2325be6
--- a/dev/null
+++ b/lib/.gitignore
@@ -0,0 +1,7 @@
+*.lo
+*.o
+Makefile.in
+libopkele.la
+.libs
+.deps
+Makefile
diff --git a/lib/Makefile.am b/lib/Makefile.am
new file mode 100644
index 0000000..6f3f9f3
--- a/dev/null
+++ b/lib/Makefile.am
@@ -0,0 +1,24 @@
+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
diff --git a/lib/consumer.cc b/lib/consumer.cc
new file mode 100644
index 0000000..bd76b61
--- a/dev/null
+++ b/lib/consumer.cc
@@ -0,0 +1,316 @@
+#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_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_(mode_t mode,const string& identity,const string& return_to,const string& trust_root) {
+        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 = util::canonicalize_url(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) { }
+        return p.append_query(server);
+    }
+
+    void consumer_t::id_res(const params_t& pin,const string& identity) {
+        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"):util::canonicalize_url(identity),server,delegate);
+        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(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()");
+            }
+        }
+    }
+
+    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");
+    }
+
+}
diff --git a/lib/data.cc b/lib/data.cc
new file mode 100644
index 0000000..c040430
--- a/dev/null
+++ b/lib/data.cc
@@ -0,0 +1,11 @@
+#include <opkele/data.h>
+
+namespace opkele {
+
+    namespace data {
+
+        const char *_default_p = "155172898181473697471232257763715539915724801966915404479707795314057629378541917580651227423698188993727816152646631438561595825688188889951272158842675419950341258706556549803580104870537681476726513255747040765857479291291572334510643245094715007229621094194349783925984760375594985848253359305585439638443";
+        const char *_default_g = "2";
+
+    }
+}
diff --git a/lib/exception.cc b/lib/exception.cc
new file mode 100644
index 0000000..b7c1702
--- a/dev/null
+++ b/lib/exception.cc
@@ -0,0 +1,22 @@
+#include <openssl/err.h>
+#include <curl/curl.h>
+#include <opkele/exception.h>
+
+namespace opkele {
+
+    exception_openssl::exception_openssl(OPKELE_E_PARS)
+        : _error(ERR_peek_last_error()),
+        _ssl_string(ERR_error_string(_error,0)),
+        exception(OPKELE_E_CONS_ w+" ["+_ssl_string+']') {
+        }
+
+    exception_curl::exception_curl(OPKELE_E_PARS)
+        : _error(CURLE_OK),
+        exception_network(OPKELE_E_CONS) { }
+    exception_curl::exception_curl(OPKELE_E_PARS,CURLcode e)
+        : _error(e),
+        _curl_string(curl_easy_strerror(e)),
+        exception_network(OPKELE_E_CONS_ w+" ["+_curl_string+']') {
+        }
+
+}
diff --git a/lib/params.cc b/lib/params.cc
new file mode 100644
index 0000000..14f1a53
--- a/dev/null
+++ b/lib/params.cc
@@ -0,0 +1,96 @@
+#include <opkele/types.h>
+#include <opkele/exception.h>
+#include <opkele/util.h>
+#include <openssl/sha.h>
+#include <openssl/hmac.h>
+#include <mimetic/mimetic.h>
+
+namespace opkele {
+    using namespace std;
+
+    bool params_t::has_param(const string& n) const {
+        return find(n)!=end();
+    }
+    const string& params_t::get_param(const string& n) const {
+        const_iterator i = find(n);
+        if(i==end())
+            throw failed_lookup(OPKELE_CP_ n+": no such parameter");
+        return i->second;
+    }
+    string& params_t::get_param(const string& n) {
+        iterator i = find(n);
+        if(i==end())
+            throw failed_lookup(OPKELE_CP_ n+": no such parameter");
+        return i->second;
+    }
+
+    void params_t::parse_keyvalues(const string& kv) {
+        clear();
+        string::size_type p = 0;
+        while(true) {
+            string::size_type co = kv.find(':',p);
+            if(co==string::npos)
+                break;
+            string::size_type nl = kv.find('\n',co+1);
+            if(nl==string::npos)
+                throw bad_input(OPKELE_CP_ "malformed input");
+            insert(value_type(kv.substr(p,co-p),kv.substr(co+1,nl-co-1)));
+            p = nl+1;
+        }
+    }
+
+    void params_t::sign(secret_t secret,string& sig,const string& slist,const char *prefix) const {
+        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(prefix) f.insert(0,prefix);
+            kv += get_param(f);
+            kv += '\n';
+            if(co==string::npos)
+                break;
+            p = co+1;
+        }
+        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);
+        mimetic::Base64::Encoder b(0);
+        sig.erase();
+        mimetic::encode(
+                md,md+md_len, b,
+                back_insert_iterator<string>(sig) );
+    }
+
+    string params_t::append_query(const string& url,const char *prefix) const {
+        string rv = url;
+        bool p = true;
+        if(rv.find('?')==string::npos) {
+            rv += '?';
+            p = false;
+        }
+        for(const_iterator i=begin();i!=end();++i) {
+            if(p)
+                rv += '&';
+            else
+                p = true;
+            rv += prefix;
+            rv += i->first;
+            rv += '=';
+            rv += util::url_encode(i->second);
+        }
+        return rv;
+    }
+
+    ostream& operator << (ostream& o,const params_t& p) {
+        for(params_t::const_iterator i=p.begin();i!=p.end();++i)
+            o << i->first << ':' << i->second << '\n';
+        return o;
+    }
+
+}
diff --git a/lib/secret.cc b/lib/secret.cc
new file mode 100644
index 0000000..ae8a3c5
--- a/dev/null
+++ b/lib/secret.cc
@@ -0,0 +1,61 @@
+#include <algorithm>
+#include <functional>
+#include <opkele/types.h>
+#include <opkele/exception.h>
+#include <mimetic/mimetic.h>
+
+namespace opkele {
+    using namespace std;
+
+    template<class __a1,class __a2,class __r>
+        struct bitwise_xor : public binary_function<__a1,__a2,__r> {
+            __r operator() (const __a1& a1,const __a2& a2) const {
+                return a1^a2;
+            }
+        };
+
+    void secret_t::enxor_to_base64(const unsigned char *key_sha1,string& rv) const {
+        if(size()!=20)
+            throw bad_input(OPKELE_CP_ "wrong secret size");
+        vector<unsigned char> tmp;
+        transform(
+                begin(), end(),
+                key_sha1,
+                back_insert_iterator<vector<unsigned char> >(tmp),
+                bitwise_xor<unsigned char,unsigned char,unsigned char>() );
+        mimetic::Base64::Encoder b(0);
+        mimetic::encode(
+                tmp.begin(),tmp.end(), b,
+                back_insert_iterator<string>(rv) );
+    }
+
+    void secret_t::enxor_from_base64(const unsigned char *key_sha1,const string& b64) {
+        mimetic::Base64::Decoder b;
+        clear();
+        mimetic::decode(
+                b64.begin(),b64.end(), b,
+                back_insert_iterator<secret_t>(*this) );
+        transform(
+                begin(), end(),
+                key_sha1,
+                begin(),
+                bitwise_xor<unsigned char,unsigned char,unsigned char>() );
+    }
+
+    void secret_t::to_base64(string& rv) const {
+        if(size()!=20)
+            throw bad_input(OPKELE_CP_ "wrong secret size");
+        mimetic::Base64::Encoder b(0);
+        mimetic::encode(
+                begin(),end(), b,
+                back_insert_iterator<string>(rv) );
+    }
+
+    void secret_t::from_base64(const string& b64) {
+        mimetic::Base64::Decoder b;
+        mimetic::decode(
+                b64.begin(),b64.end(), b,
+                back_insert_iterator<secret_t>(*this) );
+    }
+
+}
diff --git a/lib/server.cc b/lib/server.cc
new file mode 100644
index 0000000..51d4554
--- a/dev/null
+++ b/lib/server.cc
@@ -0,0 +1,169 @@
+#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_setup(const params_t& pin,string& return_to,params_t& pout) {
+        checkid_(mode_checkid_setup,pin,return_to,pout);
+    }
+
+    void server_t::checkid_(mode_t mode,const params_t& pin,string& return_to,params_t& pout) {
+        if(mode!=mode_checkid_immediate && mode!=mode_checkid_setup)
+            throw bad_input(OPKELE_CP_ "invalid checkid_* mode");
+        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);
+        }
+        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.clear();
+        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");
+    }
+
+    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) { }
+        }
+    }
+
+}
diff --git a/lib/util.cc b/lib/util.cc
new file mode 100644
index 0000000..1e7335c
--- a/dev/null
+++ b/lib/util.cc
@@ -0,0 +1,138 @@
+#include <errno.h>
+#include <cassert>
+#include <vector>
+#include <string>
+#include <mimetic/mimetic.h>
+#include <curl/curl.h>
+#include "opkele/util.h"
+#include "opkele/exception.h"
+
+namespace opkele {
+    using namespace std;
+
+    namespace util {
+
+        /*
+         * big numerics
+         */
+
+        BIGNUM *base64_to_bignum(const string& b64) {
+            vector<unsigned char> bin;
+            mimetic::Base64::Decoder b;
+            mimetic::decode(
+                    b64.begin(),b64.end(), b,
+                    back_insert_iterator<vector<unsigned char> >(bin) );
+            BIGNUM *rv = BN_bin2bn(&(bin.front()),bin.size(),0);
+            if(!rv)
+                throw failed_conversion(OPKELE_CP_ "failed to BN_bin2bn()");
+            return rv;
+        }
+
+        BIGNUM *dec_to_bignum(const string& dec) {
+            BIGNUM *rv = 0;
+            if(!BN_dec2bn(&rv,dec.c_str()))
+                throw failed_conversion(OPKELE_CP_ "failed to BN_dec2bn()");
+            return rv;
+        }
+
+        string bignum_to_base64(const BIGNUM *bn) {
+            vector<unsigned char> bin(BN_num_bytes(bn));
+            int l = BN_bn2bin(bn,&(bin.front()));
+            string rv;
+            mimetic::Base64::Encoder b(0);
+            mimetic::encode(
+                    bin.begin(),bin.begin()+l, b,
+                    back_insert_iterator<string>(rv) );
+            return rv;
+        }
+
+        /*
+         * w3c times
+         */
+
+        string time_to_w3c(time_t t) {
+            struct tm tm_t;
+            if(!gmtime_r(&t,&tm_t))
+                throw failed_conversion(OPKELE_CP_ "failed to BN_dec2bn()");
+            char rv[25];
+            if(!strftime(rv,sizeof(rv)-1,"%Y-%m-%dT%H:%M:%SZ",&tm_t))
+                throw failed_conversion(OPKELE_CP_ "failed to strftime()");
+            return rv;
+        }
+
+        time_t w3c_to_time(const string& w) {
+            struct tm tm_t;
+            memset(&tm_t,0,sizeof(tm_t));
+            if(
+                    sscanf(
+                        w.c_str(),
+                        "%04d-%02d-%02dT%02d:%02d:%02dZ",
+                        &tm_t.tm_year,&tm_t.tm_mon,&tm_t.tm_mday,
+                        &tm_t.tm_hour,&tm_t.tm_min,&tm_t.tm_sec
+                    ) != 6 )
+                throw failed_conversion(OPKELE_CP_ "failed to sscanf()");
+            tm_t.tm_mon--;
+            tm_t.tm_year-=1900;
+            time_t rv = mktime(&tm_t);
+            if(rv==(time_t)-1)
+                throw failed_conversion(OPKELE_CP_ "failed to mktime()");
+            return rv;
+        }
+
+        /*
+         *
+         */
+
+        string canonicalize_url(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;
+            }
+            if(rv.find('/',i)==string::npos)
+                rv += '/';
+            return rv;
+        }
+
+        string url_encode(const string& str) {
+            char * t = curl_escape(str.c_str(),str.length());
+            if(!t)
+                throw failed_conversion(OPKELE_CP_ "failed to curl_escape()");
+            string rv(t);
+            curl_free(t);
+            return rv;
+        }
+
+        string long_to_string(long l) {
+            char rv[32];
+            int r=snprintf(rv,sizeof(rv),"%ld",l);
+            if(r<0 || r>=sizeof(rv))
+                throw failed_conversion(OPKELE_CP_ "failed to snprintf()");
+            return rv;
+        }
+
+        long string_to_long(const string& s) {
+            char *endptr = 0;
+            long rv = strtol(s.c_str(),&endptr,10);
+            if((!endptr) || endptr==s.c_str())
+                throw failed_conversion(OPKELE_CP_ "failed to strtol()");
+            return rv;
+        }
+
+    }
+
+}