X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=src%2Fcredential%2Fgnunet-service-credential.c;h=be75e485ec375f65b2e573615e93fe7f1f9ad95c;hb=1eb75229e02e5bd678f1a99eae9a6062330ecb46;hp=3ad2e2e1dd580c057e72569d00e2f529c47fd9a9;hpb=3664423a917b4cf3773445b40b5ad8f5dd8e35e8;p=oweals%2Fgnunet.git

diff --git a/src/credential/gnunet-service-credential.c b/src/credential/gnunet-service-credential.c
index 3ad2e2e1d..be75e485e 100644
--- a/src/credential/gnunet-service-credential.c
+++ b/src/credential/gnunet-service-credential.c
@@ -27,43 +27,199 @@
 #include "gnunet_credential_service.h"
 #include "gnunet_statistics_service.h"
 #include "credential.h"
+#include "credential_serialization.h"
 #include "gnunet_protocols.h"
+#include "gnunet_signatures.h"
 
-// For Looking up GNS request
 #include <gnunet_dnsparser_lib.h>
 #include <gnunet_identity_service.h>
 #include <gnunet_gnsrecord_lib.h>
 #include <gnunet_namestore_service.h>
 #include <gnunet_gns_service.h>
-#include "gnunet_gns_service.h"
 
 
+#define GNUNET_CREDENTIAL_MAX_LENGTH 255
 
+struct VerifyRequestHandle;
 
-#define GNUNET_CREDENTIAL_MAX_LENGTH 255
+struct DelegationSetQueueEntry;
+
+
+struct DelegationChainEntry
+{
+  /**
+   * DLL
+   */
+  struct DelegationChainEntry *next;
+
+  /**
+   * DLL
+   */
+  struct DelegationChainEntry *prev;
+
+  /**
+   * The issuer
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey issuer_key;
+  
+  /**
+   * The subject
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey subject_key;
+  
+  /**
+   * The issued attribute
+   */
+  char *issuer_attribute;
+  
+  /**
+   * The delegated attribute
+   */
+  char *subject_attribute;
+};
 
 /**
  * DLL for record
  */
-struct AttributeRecordEntry
+struct CredentialRecordEntry
 {
   /**
    * DLL
    */
-  struct AttributeRecordEntry *next;
+  struct CredentialRecordEntry *next;
 
   /**
    * DLL
    */
-  struct AttributeRecordEntry *prev;
-
+  struct CredentialRecordEntry *prev;
+  
+  /**
+   * Number of references in delegation chains
+   */
+  uint32_t refcount;
 
   /**
    * Payload
    */
-  struct GNUNET_CREDENTIAL_AttributeRecordData record_data;
+  struct GNUNET_CREDENTIAL_Credential *credential;
+};
+
+/**
+ * DLL used for delegations
+ * Used for OR delegations
+ */
+struct DelegationQueueEntry
+{
+  /**
+   * DLL
+   */
+  struct DelegationQueueEntry *next;
+
+  /**
+   * DLL
+   */
+  struct DelegationQueueEntry *prev;
+
+  /**
+   * Sets under this Queue
+   */
+  struct DelegationSetQueueEntry *set_entries_head;
+
+  /**
+   * Sets under this Queue
+   */
+  struct DelegationSetQueueEntry *set_entries_tail;
+
+  /**
+   * Parent set
+   */
+  struct DelegationSetQueueEntry *parent_set;
+
+  /**
+   * Required solutions
+   */
+  uint32_t required_solutions;
+};
+
+/**
+ * DLL for delegation sets
+ * Used for AND delegation set
+ */
+struct DelegationSetQueueEntry
+{
+  /**
+   * DLL
+   */
+  struct DelegationSetQueueEntry *next;
+
+  /**
+   * DLL
+   */
+  struct DelegationSetQueueEntry *prev;
+
+    /**
+   * GNS handle
+   */
+  struct GNUNET_GNS_LookupRequest *lookup_request;
+
+  /**
+   * Verify handle
+   */
+  struct VerifyRequestHandle *handle;
+
+  /**
+   * Parent attribute delegation
+   */
+  struct DelegationQueueEntry *parent;
+
+  /**
+   * Issuer key
+   */
+  struct GNUNET_CRYPTO_EcdsaPublicKey *issuer_key;
+
+  /**
+   * Queue entries of this set
+   */
+  struct DelegationQueueEntry *queue_entries_head;
+
+  /**
+   * Queue entries of this set
+   */
+  struct DelegationQueueEntry *queue_entries_tail;
+
+  /**
+   * Parent QueueEntry
+   */
+  struct DelegationQueueEntry *parent_queue_entry;
+
+  /**
+   * Issuer attribute delegated to
+   */
+  char *issuer_attribute;
+
+  /**
+   * The current attribute to look up
+   */
+  char *lookup_attribute;
+
+  /**
+   * Trailing attribute context
+   */
+  char *attr_trailer;
+
+  /**
+   * Still to resolve delegation as string
+   */
+  char *unresolved_attribute_delegation;
+
+  /**
+   * The delegation chain entry
+   */
+  struct DelegationChainEntry *delegation_chain_entry;
+
 };
 
+
 /**
  * Handle to a lookup operation from api
  */
@@ -86,35 +242,85 @@ struct VerifyRequestHandle
   struct GNUNET_SERVICE_Client *client;
 
   /**
-   * Handle to GNS lookup
+   * GNS handle
    */
   struct GNUNET_GNS_LookupRequest *lookup_request;
 
+  /**
+   * Size of delegation tree
+   */
+  uint32_t delegation_chain_size;
+
+  /**
+   * Children of this attribute
+   */
+  struct DelegationChainEntry *delegation_chain_head;
+
+  /**
+   * Children of this attribute
+   */
+  struct DelegationChainEntry *delegation_chain_tail;
+
   /**
    * Issuer public key
    */
   struct GNUNET_CRYPTO_EcdsaPublicKey issuer_key;
 
+  /**
+   * Issuer attribute
+   */
+  char *issuer_attribute;
+
   /**
    * Subject public key
    */
   struct GNUNET_CRYPTO_EcdsaPublicKey subject_key;
 
   /**
-   * Attribute Chain
+   * Credential DLL
    */
-  struct AttributeRecordEntry *attr_chain_head;
+  struct CredentialRecordEntry *cred_chain_head;
 
   /**
-   * Attribute Chain
+   * Credential DLL
    */
-  struct AttributeRecordEntry *attr_chain_tail;
+  struct CredentialRecordEntry *cred_chain_tail;
+
+  /**
+   * Credential DLL size
+   */
+  uint32_t cred_chain_size;
+
+  /**
+   * Root Delegation Set
+   */
+  struct DelegationSetQueueEntry *root_set;
+
+  /**
+   * Current Delegation Pointer
+   */
+  struct DelegationQueueEntry *current_delegation;
 
   /**
    * request id
    */
   uint32_t request_id;
 
+  /**
+   * Pending lookups
+   */
+  uint64_t pending_lookups;
+
+  /**
+   * Credential iterator
+   */
+  struct GNUNET_NAMESTORE_ZoneIterator *cred_collection_iter;
+
+  /**
+   * Collect task
+   */
+  struct GNUNET_SCHEDULER_Task *collect_next_task;
+
 };
 
 
@@ -133,13 +339,98 @@ static struct VerifyRequestHandle *vrh_tail;
  */
 static struct GNUNET_STATISTICS_Handle *statistics;
 
-
-
 /**
  * Handle to GNS service.
  */
 static struct GNUNET_GNS_Handle *gns;
 
+
+/**
+ * Handle to namestore service
+ */
+static struct GNUNET_NAMESTORE_Handle *namestore;
+
+static void
+cleanup_delegation_set (struct DelegationSetQueueEntry *ds_entry)
+{
+  struct DelegationQueueEntry *dq_entry;
+  struct DelegationSetQueueEntry *child;
+
+  if (NULL == ds_entry)
+    return;
+
+  for (dq_entry = ds_entry->queue_entries_head;
+       NULL != dq_entry;
+       dq_entry = ds_entry->queue_entries_head)
+  {
+    GNUNET_CONTAINER_DLL_remove (ds_entry->queue_entries_head,
+                                 ds_entry->queue_entries_tail,
+                                 dq_entry);
+    for (child = dq_entry->set_entries_head;
+         NULL != child;
+         child = dq_entry->set_entries_head)
+    {
+      GNUNET_CONTAINER_DLL_remove (dq_entry->set_entries_head,
+                                   dq_entry->set_entries_tail,
+                                   child);
+      cleanup_delegation_set (child);
+    }
+    GNUNET_free (dq_entry);
+  }
+  if (NULL != ds_entry->issuer_key)
+    GNUNET_free (ds_entry->issuer_key);
+  if (NULL != ds_entry->lookup_attribute)
+    GNUNET_free (ds_entry->lookup_attribute);
+  if (NULL != ds_entry->issuer_attribute)
+    GNUNET_free (ds_entry->issuer_attribute);
+  if (NULL != ds_entry->unresolved_attribute_delegation)
+    GNUNET_free (ds_entry->unresolved_attribute_delegation);
+  if (NULL != ds_entry->attr_trailer)
+    GNUNET_free (ds_entry->attr_trailer);
+  if (NULL != ds_entry->lookup_request)
+  {
+    GNUNET_GNS_lookup_cancel (ds_entry->lookup_request);
+    ds_entry->lookup_request = NULL;
+  }
+  if (NULL != ds_entry->delegation_chain_entry)
+  {
+    if (NULL != ds_entry->delegation_chain_entry->subject_attribute)
+      GNUNET_free (ds_entry->delegation_chain_entry->subject_attribute);
+    if (NULL != ds_entry->delegation_chain_entry->issuer_attribute)
+      GNUNET_free (ds_entry->delegation_chain_entry->issuer_attribute);
+    GNUNET_free (ds_entry->delegation_chain_entry);
+  }
+  GNUNET_free (ds_entry);
+}
+
+static void
+cleanup_handle (struct VerifyRequestHandle *vrh)
+{
+  struct CredentialRecordEntry *cr_entry;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Cleaning up...\n");
+  if (NULL != vrh->lookup_request)
+  {
+    GNUNET_GNS_lookup_cancel (vrh->lookup_request);
+    vrh->lookup_request = NULL;
+  }
+  cleanup_delegation_set (vrh->root_set);
+  if (NULL != vrh->issuer_attribute)
+    GNUNET_free (vrh->issuer_attribute);
+  for (cr_entry = vrh->cred_chain_head; 
+       NULL != vrh->cred_chain_head;
+       cr_entry = vrh->cred_chain_head)
+  {
+    GNUNET_CONTAINER_DLL_remove (vrh->cred_chain_head,
+                                 vrh->cred_chain_tail,
+                                 cr_entry);
+    if (NULL != cr_entry->credential);
+      GNUNET_free (cr_entry->credential);
+    GNUNET_free (cr_entry);
+  }
+  GNUNET_free (vrh);
+}
+
 /**
  * Task run during shutdown.
  *
@@ -150,26 +441,421 @@ static void
 shutdown_task (void *cls)
 {
   struct VerifyRequestHandle *vrh;
-  
+
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-	      "Shutting down!\n");
+              "Shutting down!\n");
+
   while (NULL != (vrh = vrh_head))
   {
     //CREDENTIAL_resolver_lookup_cancel (clh->lookup);
     GNUNET_CONTAINER_DLL_remove (vrh_head,
                                  vrh_tail,
                                  vrh);
-    GNUNET_free (vrh);
+    cleanup_handle (vrh);
   }
 
-  
+  if (NULL != gns)
+  {
+    GNUNET_GNS_disconnect (gns);
+    gns = NULL;
+  }
+  if (NULL != namestore)
+  {
+    GNUNET_NAMESTORE_disconnect (namestore);
+    namestore = NULL;
+  }
   if (NULL != statistics)
   {
     GNUNET_STATISTICS_destroy (statistics,
                                GNUNET_NO);
     statistics = NULL;
   }
-  
+
+}
+
+
+
+/**
+ * Send.
+ *
+ * @param handle the handle to the request
+ */
+static void
+send_lookup_response (struct VerifyRequestHandle *vrh)
+{
+  struct GNUNET_MQ_Envelope *env;
+  struct DelegationChainResultMessage *rmsg;
+  struct DelegationChainEntry *dce;
+  struct GNUNET_CREDENTIAL_Delegation dd[vrh->delegation_chain_size];
+  struct GNUNET_CREDENTIAL_Credential cred[vrh->cred_chain_size];
+  struct CredentialRecordEntry *cd;
+  struct CredentialRecordEntry *tmp;
+  size_t size;
+  int i;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Sending response\n");
+  dce = vrh->delegation_chain_head;
+  for (i=0;i<vrh->delegation_chain_size;i++)
+  {
+    dd[i].issuer_key = dce->issuer_key;
+    dd[i].subject_key = dce->subject_key;
+    dd[i].issuer_attribute = dce->issuer_attribute;
+    dd[i].issuer_attribute_len = strlen (dce->issuer_attribute)+1;
+    dd[i].subject_attribute_len = 0;
+    dd[i].subject_attribute = NULL;
+    if (NULL != dce->subject_attribute)
+    {
+      dd[i].subject_attribute = dce->subject_attribute;
+      dd[i].subject_attribute_len = strlen(dce->subject_attribute)+1;
+    }
+    dce = dce->next;
+  }
+
+  /**
+   * Remove all credentials not needed
+   */
+  for (cd = vrh->cred_chain_head; NULL != cd;)
+  {
+    if (cd->refcount > 0)
+    {
+      cd = cd->next;
+      continue;
+    }
+    tmp = cd;
+    cd = cd->next;
+    GNUNET_CONTAINER_DLL_remove (vrh->cred_chain_head,
+                                 vrh->cred_chain_tail,
+                                 tmp);
+    GNUNET_free (tmp->credential);
+    GNUNET_free (tmp);
+    vrh->cred_chain_size--;
+  }
+
+  /**
+   * Get serialized record data
+   * Append at the end of rmsg
+   */
+  cd = vrh->cred_chain_head;
+  for (i=0;i<vrh->cred_chain_size;i++)
+  {
+    cred[i].issuer_key = cd->credential->issuer_key;
+    cred[i].subject_key = cd->credential->subject_key;
+    cred[i].issuer_attribute_len = strlen(cd->credential->issuer_attribute)+1;
+    cred[i].issuer_attribute = cd->credential->issuer_attribute;
+    cred[i].expiration = cd->credential->expiration;
+    cred[i].signature = cd->credential->signature;
+    cd = cd->next;
+  }
+  size = GNUNET_CREDENTIAL_delegation_chain_get_size (vrh->delegation_chain_size,
+                                                      dd,
+                                                      vrh->cred_chain_size,
+                                                      cred);
+  env = GNUNET_MQ_msg_extra (rmsg,
+                             size,
+                             GNUNET_MESSAGE_TYPE_CREDENTIAL_VERIFY_RESULT);
+  //Assign id so that client can find associated request
+  rmsg->id = vrh->request_id;
+  rmsg->d_count = htonl (vrh->delegation_chain_size);
+  rmsg->c_count = htonl (vrh->cred_chain_size);
+
+  if (0 < vrh->cred_chain_size)
+    rmsg->cred_found = htonl (GNUNET_YES);
+  else
+    rmsg->cred_found = htonl (GNUNET_NO);
+
+  GNUNET_assert (-1 != 
+                 GNUNET_CREDENTIAL_delegation_chain_serialize (vrh->delegation_chain_size,
+                                                               dd,
+                                                               vrh->cred_chain_size,
+                                                               cred,
+                                                               size,
+                                                               (char*)&rmsg[1]));
+
+  GNUNET_MQ_send (GNUNET_SERVICE_client_get_mq(vrh->client),
+                  env);
+  GNUNET_CONTAINER_DLL_remove (vrh_head, vrh_tail, vrh);
+  cleanup_handle(vrh);
+
+  GNUNET_STATISTICS_update (statistics,
+                            "Completed verifications", 1,
+                            GNUNET_NO);
+}
+
+
+static void
+backward_resolution (void* cls,
+                     uint32_t rd_count,
+                     const struct GNUNET_GNSRECORD_Data *rd)
+{
+
+  struct VerifyRequestHandle *vrh;
+  const struct GNUNET_CREDENTIAL_DelegationRecord *sets;
+  struct CredentialRecordEntry *cred_pointer;
+  struct DelegationSetQueueEntry *current_set;
+  struct DelegationSetQueueEntry *ds_entry;
+  struct DelegationSetQueueEntry *tmp_set;
+  struct DelegationQueueEntry *dq_entry;
+  char *expanded_attr;
+  char *lookup_attribute;
+  int i;
+  int j;
+
+
+  current_set = cls;
+  current_set->lookup_request = NULL;
+  vrh = current_set->handle;
+  vrh->pending_lookups--;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Got %d attrs\n", rd_count);
+
+  // Each OR
+  for (i=0; i < rd_count; i++) 
+  {
+    if (GNUNET_GNSRECORD_TYPE_ATTRIBUTE != rd[i].record_type)
+      continue;
+
+    sets = rd[i].data;
+    struct GNUNET_CREDENTIAL_DelegationSet set[ntohl(sets->set_count)];
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Found new attribute delegation with %d sets. Creating new Job...\n",
+                ntohl (sets->set_count));
+
+    if (GNUNET_OK !=GNUNET_CREDENTIAL_delegation_set_deserialize (GNUNET_ntohll(sets->data_size),
+                                                                  (const char*)&sets[1],
+                                                                  ntohl(sets->set_count),
+                                                                  set))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Failed to deserialize!\n");
+      continue;
+    }
+    dq_entry = GNUNET_new (struct DelegationQueueEntry);
+    dq_entry->required_solutions = ntohl(sets->set_count);
+    dq_entry->parent_set = current_set;
+    GNUNET_CONTAINER_DLL_insert (current_set->queue_entries_head,
+                                 current_set->queue_entries_tail,
+                                 dq_entry);
+    // Each AND
+    for (j=0; j<ntohl(sets->set_count); j++)
+    {
+      ds_entry = GNUNET_new (struct DelegationSetQueueEntry);
+      if (NULL != current_set->attr_trailer)
+      {
+        if (0 == set[j].subject_attribute_len)
+        {
+          GNUNET_asprintf (&expanded_attr,
+                           "%s",
+                           current_set->attr_trailer);
+
+        } else {
+          GNUNET_asprintf (&expanded_attr,
+                           "%s.%s",
+                           set[j].subject_attribute,
+                           current_set->attr_trailer);
+        }
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "Expanded to %s\n", expanded_attr);
+        ds_entry->unresolved_attribute_delegation = expanded_attr;
+      } else {
+        if (0 != set[j].subject_attribute_len)
+        {
+          GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                      "Not Expanding %s\n", set[j].subject_attribute);
+          ds_entry->unresolved_attribute_delegation = GNUNET_strdup (set[j].subject_attribute);
+        }
+      }
+
+      //Add a credential chain entry
+      ds_entry->delegation_chain_entry = GNUNET_new (struct DelegationChainEntry);
+      ds_entry->delegation_chain_entry->subject_key = set[j].subject_key;
+      ds_entry->issuer_key = GNUNET_new (struct GNUNET_CRYPTO_EcdsaPublicKey);
+      GNUNET_memcpy (ds_entry->issuer_key,
+                     &set[j].subject_key,
+                     sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey));
+      if (0 < set[j].subject_attribute_len)
+        ds_entry->delegation_chain_entry->subject_attribute =  GNUNET_strdup (set[j].subject_attribute);
+      ds_entry->delegation_chain_entry->issuer_key = *current_set->issuer_key;
+      ds_entry->delegation_chain_entry->issuer_attribute = GNUNET_strdup (current_set->lookup_attribute);
+
+      ds_entry->parent_queue_entry = dq_entry; //current_delegation;
+      GNUNET_CONTAINER_DLL_insert (dq_entry->set_entries_head,
+                                   dq_entry->set_entries_tail,
+                                   ds_entry);
+
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Checking for cred match\n");
+      /**
+       * Check if this delegation already matches one of our credentials
+       */
+      for(cred_pointer = vrh->cred_chain_head; cred_pointer != NULL; 
+          cred_pointer = cred_pointer->next)
+      {
+        if(0 != memcmp (&set->subject_key, 
+                        &cred_pointer->credential->issuer_key,
+                        sizeof(struct GNUNET_CRYPTO_EcdsaPublicKey)))
+          continue;
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "Checking if %s matches %s\n",
+                    ds_entry->unresolved_attribute_delegation,
+                    cred_pointer->credential->issuer_attribute);
+
+        if (0 != strcmp (ds_entry->unresolved_attribute_delegation,
+                         cred_pointer->credential->issuer_attribute))
+          continue;
+
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "Found issuer\n");
+        cred_pointer->refcount++;
+        //Backtrack
+        for (tmp_set = ds_entry;
+             NULL != tmp_set->parent_queue_entry;
+             tmp_set = tmp_set->parent_queue_entry->parent_set)
+        {
+          tmp_set->parent_queue_entry->required_solutions--;
+          if (NULL != tmp_set->delegation_chain_entry)
+          {
+            vrh->delegation_chain_size++;
+            GNUNET_CONTAINER_DLL_insert (vrh->delegation_chain_head,
+                                         vrh->delegation_chain_tail,
+                                         tmp_set->delegation_chain_entry);
+          }
+          if (0 < tmp_set->parent_queue_entry->required_solutions)
+            break;
+        }
+
+        if (NULL == tmp_set->parent_queue_entry)
+        {
+          GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                      "All solutions found\n");
+          //Found match
+          send_lookup_response (vrh);
+          return;
+        }
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "Not all solutions found yet.\n");
+        continue;
+
+      }
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Building new lookup request from %s\n",
+                  ds_entry->unresolved_attribute_delegation);
+      //Continue with backward resolution
+      char issuer_attribute_name[strlen (ds_entry->unresolved_attribute_delegation)+1];
+      strcpy (issuer_attribute_name,
+              ds_entry->unresolved_attribute_delegation);
+      char *next_attr = strtok (issuer_attribute_name, ".");
+      GNUNET_asprintf (&lookup_attribute,
+                       "%s.gnu",
+                       next_attr);
+      GNUNET_asprintf (&ds_entry->lookup_attribute,
+                       "%s",
+                       next_attr);
+      if (strlen (next_attr) == strlen (ds_entry->unresolved_attribute_delegation))
+      {
+        ds_entry->attr_trailer = NULL;
+      } else {
+        next_attr += strlen (next_attr) + 1;
+        ds_entry->attr_trailer = GNUNET_strdup (next_attr);
+      }
+
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                  "Looking up %s\n", ds_entry->lookup_attribute);
+      if (NULL != ds_entry->attr_trailer)
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "%s still to go...\n", ds_entry->attr_trailer);
+
+      vrh->pending_lookups++;
+      ds_entry->handle = vrh;
+      ds_entry->lookup_request = GNUNET_GNS_lookup (gns,
+                                                    lookup_attribute,
+                                                    ds_entry->issuer_key, //issuer_key,
+                                                    GNUNET_GNSRECORD_TYPE_ATTRIBUTE,
+                                                    GNUNET_GNS_LO_DEFAULT,
+                                                    &backward_resolution,
+                                                    ds_entry);
+      GNUNET_free (lookup_attribute);
+    }
+  }
+
+  if(0 == vrh->pending_lookups)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "We are all out of attributes...\n");
+    send_lookup_response (vrh);
+    return;
+
+  }
+} 
+
+
+/**
+ * Result from GNS lookup.
+ *
+ * @param cls the closure (our client lookup handle)
+ * @param rd_count the number of records in @a rd
+ * @param rd the record data
+ */
+static void
+delegation_chain_resolution_start (void* cls)
+{
+  struct VerifyRequestHandle *vrh = cls;
+  struct DelegationSetQueueEntry *ds_entry;
+  struct CredentialRecordEntry *cr_entry;
+  vrh->lookup_request = NULL;
+
+  if (0 == vrh->cred_chain_size)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "No credentials found\n");
+    send_lookup_response (vrh);
+    return;
+  }
+
+  for (cr_entry = vrh->cred_chain_head; cr_entry != NULL; cr_entry = cr_entry->next)
+  {
+    if (0 != memcmp (&cr_entry->credential->issuer_key,
+                     &vrh->issuer_key,
+                     sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey)))
+      continue;
+    if (0 != strcmp (cr_entry->credential->issuer_attribute, vrh->issuer_attribute))
+      continue;
+    cr_entry->refcount++;
+    //Found match prematurely
+    send_lookup_response (vrh);
+    return;
+
+  }
+
+  /**
+   * Check for attributes from the issuer and follow the chain 
+   * till you get the required subject's attributes
+   */
+  char issuer_attribute_name[strlen (vrh->issuer_attribute)];
+  strcpy (issuer_attribute_name,
+          vrh->issuer_attribute);
+  strcpy (issuer_attribute_name + strlen (vrh->issuer_attribute),
+          ".gnu");
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Looking up %s\n", issuer_attribute_name);
+  ds_entry = GNUNET_new (struct DelegationSetQueueEntry);
+  ds_entry->issuer_key = GNUNET_new (struct GNUNET_CRYPTO_EcdsaPublicKey);
+  memcpy (ds_entry->issuer_key,
+          &vrh->issuer_key,
+          sizeof (struct GNUNET_CRYPTO_EcdsaPublicKey));
+  ds_entry->issuer_attribute = GNUNET_strdup (vrh->issuer_attribute);
+  ds_entry->handle = vrh;
+  ds_entry->lookup_attribute = GNUNET_strdup (vrh->issuer_attribute);
+  vrh->root_set = ds_entry;
+  vrh->pending_lookups = 1;
+  //Start with backward resolution
+  ds_entry->lookup_request = GNUNET_GNS_lookup (gns,
+                                                issuer_attribute_name,
+                                                &vrh->issuer_key, //issuer_key,
+                                                GNUNET_GNSRECORD_TYPE_ATTRIBUTE,
+                                                GNUNET_GNS_LO_DEFAULT,
+                                                &backward_resolution,
+                                                ds_entry);
 }
 
 /**
@@ -181,12 +867,10 @@ shutdown_task (void *cls)
  */
 static int
 check_verify (void *cls,
-		    const struct VerifyMessage *v_msg)
+              const struct VerifyMessage *v_msg)
 {
   size_t msg_size;
-  size_t attr_len;
-  const char* s_attr;
-  const char* i_attr;
+  const char* attr;
 
   msg_size = ntohs (v_msg->header.size);
   if (msg_size < sizeof (struct VerifyMessage))
@@ -194,17 +878,14 @@ check_verify (void *cls,
     GNUNET_break (0);
     return GNUNET_SYSERR;
   }
-  i_attr = (const char *) &v_msg[1];
-  if ( ('\0' != i_attr[v_msg->header.size - sizeof (struct VerifyMessage) - 1]) ||
-       (strlen (i_attr) > GNUNET_CREDENTIAL_MAX_LENGTH) )
+  if (ntohs (v_msg->issuer_attribute_len) > GNUNET_CREDENTIAL_MAX_LENGTH)
   {
     GNUNET_break (0);
     return GNUNET_SYSERR;
   }
-  attr_len = strlen (i_attr);
-  s_attr = ((const char *) &v_msg[1]) + attr_len + 1;
-  if ( ('\0' != s_attr[v_msg->header.size - sizeof (struct VerifyMessage) - 1]) ||
-       (strlen (s_attr) > GNUNET_CREDENTIAL_MAX_LENGTH) )
+  attr = (const char *) &v_msg[1];
+
+  if ( strlen (attr) > GNUNET_CREDENTIAL_MAX_LENGTH)
   {
     GNUNET_break (0);
     return GNUNET_SYSERR;
@@ -212,174 +893,262 @@ check_verify (void *cls,
   return GNUNET_OK;
 }
 
-
 /**
- * Result from GNS lookup.
+ * Handle Credential verification requests from client
  *
- * @param cls the closure (our client lookup handle)
- * @param rd_count the number of records in @a rd
- * @param rd the record data
+ * @param cls the closure
+ * @param client the client
+ * @param message the message
  */
 static void
-send_lookup_response (void* cls,
-                      uint32_t rd_count,
-                      const struct GNUNET_GNSRECORD_Data *rd)
+handle_verify (void *cls,
+               const struct VerifyMessage *v_msg) 
 {
-  struct VerifyRequestHandle *vrh = cls;
-  size_t len;
+  struct VerifyRequestHandle *vrh;
+  struct GNUNET_SERVICE_Client *client = cls;
+  struct CredentialRecordEntry *cr_entry;
+  uint32_t credentials_count;
+  uint32_t credential_data_size;
   int i;
-  int attr_record_count;
-  struct GNUNET_MQ_Envelope *env;
-  struct VerifyResultMessage *rmsg;
-  const struct GNUNET_CREDENTIAL_AttributeRecordData *ard;
-  struct AttributeRecordEntry *ar_entry;
+  char attr[GNUNET_CREDENTIAL_MAX_LENGTH + 1];
+  char issuer_attribute[GNUNET_CREDENTIAL_MAX_LENGTH + 1];
+  char *attrptr = attr;
+  char *credential_data;
+  const char *utf_in;
 
-  attr_record_count = 0;
-  for (i=0; i < rd_count; i++)
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received VERIFY message\n");
+  utf_in = (const char *) &v_msg[1];
+  GNUNET_STRINGS_utf8_tolower (utf_in, attrptr);
+  GNUNET_memcpy (issuer_attribute, attr, ntohs (v_msg->issuer_attribute_len));
+  issuer_attribute[ntohs (v_msg->issuer_attribute_len)] = '\0';
+  vrh = GNUNET_new (struct VerifyRequestHandle);
+  GNUNET_CONTAINER_DLL_insert (vrh_head, vrh_tail, vrh);
+  vrh->client = client;
+  vrh->request_id = v_msg->id;
+  vrh->issuer_key = v_msg->issuer_key;
+  vrh->subject_key = v_msg->subject_key;
+  vrh->issuer_attribute = GNUNET_strdup (issuer_attribute);
+  if (NULL == issuer_attribute)
   {
-    if (GNUNET_GNSRECORD_TYPE_ATTRIBUTE != rd[i].record_type)
-      continue;
-    attr_record_count++;
-    ard = rd[i].data;
-    /**
-     * TODO:
-     * Check if we have already found our credential here
-     * If so return success
-     * Else
-     *  Save all found attributes/issues and prepare forward
-     *  resolution of issuer attribute
-     */
-    ar_entry = GNUNET_new (struct AttributeRecordEntry);
-    ar_entry->record_data = *ard;
-    GNUNET_CONTAINER_DLL_insert_tail (vrh->attr_chain_head,
-                                      vrh->attr_chain_tail,
-                                      ar_entry);
-
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, 
+                "No issuer attribute provided!\n");
+    send_lookup_response (vrh);
+    return;
   }
-
   /**
-   * TODO
-   * Start resolution of Attribute delegations from issuer
-   *
-   * - Build adequate data structures for attribute(s) to lookup
-   * - Use GNUNET_GNSRECORD_TYPE_XXX
-   * - recursively try to find match(es) with results found top
-   * - return one found credential chain
-   *
+   * First, collect credentials
+   * TODO: cleanup!
    */
+  credentials_count = ntohl(v_msg->c_count);
+  credential_data_size = ntohs (v_msg->header.size) 
+    - sizeof (struct VerifyMessage)
+    - ntohs (v_msg->issuer_attribute_len)
+    - 1;
+  struct GNUNET_CREDENTIAL_Credential credentials[credentials_count];
+  credential_data = (char*)&v_msg[1] + ntohs (v_msg->issuer_attribute_len) + 1;
+  if (GNUNET_OK != GNUNET_CREDENTIAL_credentials_deserialize (credential_data_size,
+                                                              credential_data,
+                                                              credentials_count,
+                                                              credentials))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, 
+                "Cannot deserialize credentials!\n");
+    send_lookup_response (vrh);
+    return;
+  }
 
-  /**
-   * Get serialized record data size
-   */
-  len = attr_record_count * sizeof (struct GNUNET_CREDENTIAL_AttributeRecordData);
+  for (i=0;i<credentials_count;i++) {
+    cr_entry = GNUNET_new (struct CredentialRecordEntry);
+    cr_entry->credential = GNUNET_malloc (sizeof (struct GNUNET_CREDENTIAL_Credential) +
+                                          credentials[i].issuer_attribute_len);
+    GNUNET_memcpy (cr_entry->credential,
+                   &credentials[i],
+                   sizeof (struct GNUNET_CREDENTIAL_Credential));
+    GNUNET_memcpy (&cr_entry->credential[1],
+                   credentials[i].issuer_attribute,
+                   credentials[i].issuer_attribute_len);
+    cr_entry->credential->issuer_attribute = (char*)&cr_entry->credential[1];
+    GNUNET_CONTAINER_DLL_insert_tail (vrh->cred_chain_head,
+                                      vrh->cred_chain_tail,
+                                      cr_entry);
+    vrh->cred_chain_size++;
+  }
 
-  /**
-   * Prepare a lookup result response message for the client
-   */
-  env = GNUNET_MQ_msg_extra (rmsg,
-                             len,
-                             GNUNET_MESSAGE_TYPE_CREDENTIAL_VERIFY_RESULT);
-  //Assign id so that client can find associated request
-  rmsg->id = vrh->request_id;
-  rmsg->ad_count = htonl (attr_record_count);
+  delegation_chain_resolution_start (vrh);
 
-  /**
-   * Get serialized record data
-   * Append at the end of rmsg
-   */
-  i = 0;
-  struct GNUNET_CREDENTIAL_AttributeRecordData *tmp_record = (struct GNUNET_CREDENTIAL_AttributeRecordData*) &rmsg[1];
-  for (ar_entry = vrh->attr_chain_head; NULL != ar_entry; ar_entry = ar_entry->next)
-  {
-    memcpy (tmp_record,
-            &ar_entry->record_data,
-            sizeof (struct GNUNET_CREDENTIAL_AttributeRecordData));
-    tmp_record++;
-  }
-  GNUNET_MQ_send (GNUNET_SERVICE_client_get_mq(vrh->client),
-                  env);
+}
 
-  GNUNET_CONTAINER_DLL_remove (vrh_head, vrh_tail, vrh);
+/**
+ * We encountered an error while collecting
+ */
+static void
+handle_cred_collection_error_cb (void *cls)
+{
+  struct VerifyRequestHandle *vrh = cls;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Got disconnected from namestore database.\n");
+  vrh->cred_collection_iter = NULL;
+  send_lookup_response (vrh);
+}
 
-  /**
-   * TODO:
-   * - Free DLL
-   * - Refactor into cleanup_handle() function for this
-   */
-  GNUNET_free (vrh);
+static void
+collect_next (void *cls)
+{
+  struct VerifyRequestHandle *vrh = cls;
+  vrh->collect_next_task = NULL;
+  GNUNET_assert (NULL != vrh->cred_collection_iter);
+  GNUNET_NAMESTORE_zone_iterator_next (vrh->cred_collection_iter);
+}
 
-  GNUNET_STATISTICS_update (statistics,
-                            "Completed verifications", 1,
-                            GNUNET_NO);
-  GNUNET_STATISTICS_update (statistics,
-                            "Attributes resolved",
-                            rd_count,
-                            GNUNET_NO);
+/**
+ * Store credential
+ */
+static void
+handle_cred_collection_cb (void *cls,
+                           const struct GNUNET_CRYPTO_EcdsaPrivateKey *key,
+                           const char *label,
+                           unsigned int rd_count,
+                           const struct GNUNET_GNSRECORD_Data *rd)
+{
+  struct VerifyRequestHandle *vrh = cls;
+  struct GNUNET_CREDENTIAL_Credential *crd;
+  struct CredentialRecordEntry *cr_entry;
+  int cred_record_count;
+  int i;
+
+  cred_record_count = 0;
+  for (i=0; i < rd_count; i++)
+  {
+    if (GNUNET_GNSRECORD_TYPE_CREDENTIAL != rd[i].record_type)
+      continue;
+    cred_record_count++;
+    crd = GNUNET_CREDENTIAL_credential_deserialize (rd[i].data,
+                                                    rd[i].data_size);
+    if (NULL == crd)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                  "Invalid credential found\n");
+      continue;
+    }
+    cr_entry = GNUNET_new (struct CredentialRecordEntry);
+    cr_entry->credential = crd;
+    GNUNET_CONTAINER_DLL_insert_tail (vrh->cred_chain_head,
+                                      vrh->cred_chain_tail,
+                                      cr_entry);
+    vrh->cred_chain_size++;
+  }
+  vrh->collect_next_task = GNUNET_SCHEDULER_add_now (&collect_next,
+                                                     vrh);
 }
 
 /**
- * Handle attribute verification requests from client
+ * We encountered an error while collecting
+ */
+static void
+handle_cred_collection_finished_cb (void *cls)
+{
+  struct VerifyRequestHandle *vrh = cls;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Done collecting credentials.\n");
+  vrh->cred_collection_iter = NULL;
+  delegation_chain_resolution_start (vrh);
+}
+
+/**
+ * Handle Credential collection requests from client
  *
  * @param cls the closure
  * @param client the client
  * @param message the message
  */
 static void
-handle_verify (void *cls,
-               const struct VerifyMessage *v_msg) 
+handle_collect (void *cls,
+                const struct CollectMessage *c_msg) 
 {
+  char attr[GNUNET_CREDENTIAL_MAX_LENGTH + 1];
   char issuer_attribute[GNUNET_CREDENTIAL_MAX_LENGTH + 1];
-  char subject_attribute[GNUNET_CREDENTIAL_MAX_LENGTH + 1];
-  size_t issuer_attribute_len;
   struct VerifyRequestHandle *vrh;
   struct GNUNET_SERVICE_Client *client = cls;
-  char *attrptr = issuer_attribute;
+  char *attrptr = attr;
   const char *utf_in;
 
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "Received VERIFY message\n");
+              "Received COLLECT message\n");
 
-  utf_in = (const char *) &v_msg[1];
-  GNUNET_STRINGS_utf8_tolower (utf_in, attrptr);
-  issuer_attribute_len = strlen (utf_in);
-  utf_in = (const char *) (&v_msg[1] + issuer_attribute_len + 1);
-  attrptr = subject_attribute;
+  utf_in = (const char *) &c_msg[1];
   GNUNET_STRINGS_utf8_tolower (utf_in, attrptr);
+
+  GNUNET_memcpy (issuer_attribute, attr, ntohs (c_msg->issuer_attribute_len));
+  issuer_attribute[ntohs (c_msg->issuer_attribute_len)] = '\0';
   vrh = GNUNET_new (struct VerifyRequestHandle);
   GNUNET_CONTAINER_DLL_insert (vrh_head, vrh_tail, vrh);
   vrh->client = client;
-  vrh->request_id = v_msg->id;
-  vrh->issuer_key = v_msg->issuer_key;
-  vrh->subject_key = v_msg->subject_key;
+  vrh->request_id = c_msg->id;
+  vrh->issuer_key = c_msg->issuer_key;
+  GNUNET_CRYPTO_ecdsa_key_get_public (&c_msg->subject_key,
+                                      &vrh->subject_key);
+  vrh->issuer_attribute = GNUNET_strdup (issuer_attribute);
 
-  if (NULL == subject_attribute)
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, 
-                "No subject attribute provided!\n");
-    send_lookup_response (vrh, 0, NULL);
-    return;
-  }
   if (NULL == issuer_attribute)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR, 
                 "No issuer attribute provided!\n");
-    send_lookup_response (vrh, 0, NULL);
+    send_lookup_response (vrh);
     return;
   }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Getting credentials for subject\n");
   /**
    * First, get attribute from subject
    */
-  vrh->lookup_request = GNUNET_GNS_lookup (gns,
-                                           subject_attribute,
-                                           &v_msg->subject_key, //subject_pkey,
-                                           GNUNET_GNSRECORD_TYPE_ATTRIBUTE,
-                                           GNUNET_GNS_LO_DEFAULT,
-                                           NULL, //shorten_key, always NULL
-                                           &send_lookup_response,
-                                           vrh);
+  vrh->cred_collection_iter = GNUNET_NAMESTORE_zone_iteration_start (namestore,
+                                                                     &c_msg->subject_key,
+                                                                     &handle_cred_collection_error_cb,
+                                                                     vrh,
+                                                                     &handle_cred_collection_cb,
+                                                                     vrh,
+                                                                     &handle_cred_collection_finished_cb,
+                                                                     vrh);
 }
 
 
+/**
+ * Checks a #GNUNET_MESSAGE_TYPE_CREDENTIAL_COLLECT message
+ *
+ * @param cls client sending the message
+ * @param v_msg message of type `struct CollectMessage`
+ * @return #GNUNET_OK if @a v_msg is well-formed
+ */
+static int
+check_collect (void *cls,
+               const struct CollectMessage *c_msg)
+{
+  size_t msg_size;
+  const char* attr;
+
+  msg_size = ntohs (c_msg->header.size);
+  if (msg_size < sizeof (struct CollectMessage))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  if (ntohs (c_msg->issuer_attribute_len) > GNUNET_CREDENTIAL_MAX_LENGTH)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  attr = (const char *) &c_msg[1];
+
+  if ( ('\0' != attr[ntohs(c_msg->header.size) - sizeof (struct CollectMessage) - 1]) ||
+       (strlen (attr) > GNUNET_CREDENTIAL_MAX_LENGTH) )
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
 /**
  * One of our clients disconnected, clean up after it.
  *
@@ -434,6 +1203,12 @@ run (void *cls,
     fprintf (stderr,
              _("Failed to connect to GNS\n"));
   }
+  namestore = GNUNET_NAMESTORE_connect (c);
+  if (NULL == namestore)
+  {
+    fprintf (stderr,
+             _("Failed to connect to namestore\n"));
+  }
 
   statistics = GNUNET_STATISTICS_create ("credential", c);
   GNUNET_SCHEDULER_add_shutdown (&shutdown_task, NULL);
@@ -454,6 +1229,10 @@ GNUNET_SERVICE_MAIN
                         GNUNET_MESSAGE_TYPE_CREDENTIAL_VERIFY,
                         struct VerifyMessage,
                         NULL),
+ GNUNET_MQ_hd_var_size (collect,
+                        GNUNET_MESSAGE_TYPE_CREDENTIAL_COLLECT,
+                        struct CollectMessage,
+                        NULL),
  GNUNET_MQ_handler_end());
 
 /* end of gnunet-service-credential.c */