reworked zero-padding machinery and added one more instance of zero-padding

3 files changed, 20 insertions, 14 deletions

diff --git a/lib/consumer.cc b/lib/consumer.cc
index 12866f0..282f0cc 100644
--- a/lib/consumer.cc
+++ b/lib/consumer.cc
@@ -1,344 +1,345 @@
 #include <algorithm>
 #include <cassert>
 #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 <curl/curl.h>
 #include <pcre++.h>
 
 #include <iostream>
 
 #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))
         #ifdefDISABLE_CURL_SSL_VERIFYHOST
         || (r=curl_easy_setopt(c,CURLOPT_SSL_VERIFYHOST,0))
 #endif
         #ifdefDISABLE_CURL_SSL_VERIFYPEER
         || (r=curl_easy_setopt(c,CURLOPT_SSL_VERIFYPEER,0))
 #endif
         ;
         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);
+            vector<unsigned char> ck(DH_size(dh)+1);
+            unsigned char *ckptr = &(ck.front())+1;
+            int cklen = DH_compute_key(ckptr,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);
+            if(cklen && (*ckptr)&0x80) {
+                (*(--ckptr)) = 0; ++cklen;
+            }
             unsigned char key_sha1[SHA_DIGEST_LENGTH];
-            SHA1(&(ck.front()),ck.size(),key_sha1);
+            SHA1(ckptr,cklen,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,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,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,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 {
             string ah = find_assoc(server)->handle();
             p["assoc_handle"] = ah;
         }catch(failed_lookup& fl) {
             string ah = associate(server)->handle();
             p["assoc_handle"] = ah;
         }
         if(ext) ext->checkid_hook(p,identity);
         return p.append_query(server);
     }
 
     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");
             vector<unsigned char> sig;
             util::decode_base64(sigenc,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.")-1)] = 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/server.cc b/lib/server.cc
index e81d4b6..8db97be 100644
--- a/lib/server.cc
+++ b/lib/server.cc
@@ -1,169 +1,170 @@
 #include <vector>
 #include <openssl/sha.h>
 #include <openssl/hmac.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));
+            vector<unsigned char> ck(DH_size(dh)+1);
+            unsigned char *ckptr = &(ck.front())+1;
             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);
+            if(cklen && (*ckptr)&0x80) {
+                (*(--ckptr)) = 0; ++cklen;
+            }
+            SHA1(ckptr,cklen,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,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,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,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["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;
         const string& sigenc = pin.get_param("openid.sig");
         util::decode_base64(sigenc,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
index d9abca7..94f6f53 100644
--- a/lib/util.cc
+++ b/lib/util.cc
@@ -1,158 +1,162 @@
 #include <errno.h>
 #include <cassert>
 #include <vector>
 #include <string>
 #include <openssl/bio.h>
 #include <openssl/evp.h>
 #include <curl/curl.h>
 #include "opkele/util.h"
 #include "opkele/exception.h"
 
 namespace opkele {
     using namespace std;
 
     namespace util {
 
         /*
          * base64
          */
         string encode_base64(const void *data,size_t length) {
             BIO *b64 = 0, *bmem = 0;
             try {
                 b64 = BIO_new(BIO_f_base64());
                 if(!b64)
                     throw exception_openssl(OPKELE_CP_ "failed to BIO_new() base64 encoder");
                 BIO_set_flags(b64,BIO_FLAGS_BASE64_NO_NL);
                 bmem = BIO_new(BIO_s_mem());
                 BIO_set_flags(b64,BIO_CLOSE);
                 if(!bmem)
                     throw exception_openssl(OPKELE_CP_ "failed to BIO_new() memory buffer");
                 BIO_push(b64,bmem);
                 if(BIO_write(b64,data,length)!=length)
                     throw exception_openssl(OPKELE_CP_ "failed to BIO_write()");
                 BIO_flush(b64);
                 char *rvd;
                 long rvl = BIO_get_mem_data(bmem,&rvd);
                 string rv(rvd,rvl);
                 BIO_free_all(b64);
                 return rv;
             }catch(...) {
                 if(b64) BIO_free_all(b64);
                 throw;
             }
         }
 
         void decode_base64(const string& data,vector<unsigned char>& rv) {
             BIO *b64 = 0, *bmem = 0;
             rv.clear();
             try {
                 bmem = BIO_new_mem_buf((void*)data.data(),data.size());
                 if(!bmem)
                     throw exception_openssl(OPKELE_CP_ "failed to BIO_new_mem_buf()");
                 b64 = BIO_new(BIO_f_base64());
                 if(!b64)
                     throw exception_openssl(OPKELE_CP_ "failed to BIO_new() base64 decoder");
                 BIO_set_flags(b64,BIO_FLAGS_BASE64_NO_NL);
                 BIO_push(b64,bmem);
                 unsigned char tmp[512];
                 size_t rb = 0;
                 while((rb=BIO_read(b64,tmp,sizeof(tmp)))>0)
                     rv.insert(rv.end(),tmp,&tmp[rb]);
                 BIO_free_all(b64);
             }catch(...) {
                 if(b64) BIO_free_all(b64);
                 throw;
             }
         }
 
         /*
          * big numerics
          */
 
         BIGNUM *base64_to_bignum(const string& b64) {
             vector<unsigned char> bin;
             decode_base64(b64,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()));
-            return encode_base64(&(bin.front()),l);
+            vector<unsigned char> bin(BN_num_bytes(bn)+1);
+            unsigned char *binptr = &(bin.front())+1;
+            int l = BN_bn2bin(bn,binptr);
+            if(l && (*binptr)&0x80){
+                (*(--binptr)) = 0; ++l;
+            }
+            return encode_base64(binptr,l);
         }
 
         /*
          * 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 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;
         }
 
     }
 
 }