-sms wip

1 files changed, 354 insertions, 934 deletions

diff --git a/src/util/taler-exchange-secmod-eddsa.c b/src/util/taler-exchange-secmod-eddsa.c
index dc2d35d13..3b7ee3ded 100644
--- a/src/util/taler-exchange-secmod-eddsa.c
+++ b/src/util/taler-exchange-secmod-eddsa.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014-2020 Taler Systems SA
+  Copyright (C) 2014-2021 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU General Public License as published by the Free Software
@@ -26,7 +26,7 @@
  *   and merged with the public keys of the helper by the exchange HTTPD!
  * - the main loop of the helper is SINGLE-THREADED, but there are
  *   threads for crypto-workers which (only) do the signing in parallel,
- *   working of a work-queue.
+ *   one per client.
  * - thread-safety: signing happens in parallel, thus when REMOVING private keys,
  *   we must ensure that all signers are done before we fully free() the
  *   private key. This is done by reference counting (as work is always
@@ -41,6 +41,7 @@
 #include "taler_error_codes.h"
 #include "taler_signatures.h"
 #include "secmod_common.h"
+#include <poll.h>
 
 
 /**
@@ -80,6 +81,11 @@ struct Key
   struct GNUNET_TIME_Absolute anchor;
 
   /**
+   * Generation when this key was created or revoked.
+   */
+  uint64_t key_gen;
+
+  /**
    * Reference counter. Counts the number of threads that are
    * using this key at this time.
    */
@@ -95,92 +101,6 @@ struct Key
 
 
 /**
- * Information we keep for a client connected to us.
- */
-struct Client
-{
-
-  /**
-   * Kept in a DLL.
-   */
-  struct Client *next;
-
-  /**
-   * Kept in a DLL.
-   */
-  struct Client *prev;
-
-  /**
-   * Client address.
-   */
-  struct sockaddr_un addr;
-
-  /**
-   * Number of bytes used in @e addr.
-   */
-  socklen_t addr_size;
-
-};
-
-
-struct WorkItem
-{
-
-  /**
-   * Kept in a DLL.
-   */
-  struct WorkItem *next;
-
-  /**
-   * Kept in a DLL.
-   */
-  struct WorkItem *prev;
-
-  /**
-   * Key to be used for this operation.
-   */
-  struct Key *key;
-
-  /**
-   * EDDSA signature over @e msg using @e key. Result of doing the work.
-   */
-  struct TALER_ExchangeSignatureP signature;
-
-  /**
-   * Message to sign.
-   */
-  struct GNUNET_CRYPTO_EccSignaturePurpose *purpose;
-
-  /**
-   * Client address.
-   */
-  struct sockaddr_un addr;
-
-  /**
-   * Number of bytes used in @e addr.
-   */
-  socklen_t addr_size;
-
-  /**
-   * Operation status code.
-   */
-  enum TALER_ErrorCode ec;
-
-};
-
-
-/**
- * Private key of this security module. Used to sign denomination key
- * announcements.
- */
-static struct TALER_SecurityModulePrivateKeyP smpriv;
-
-/**
- * Public key of this security module.
- */
-static struct TALER_SecurityModulePublicKeyP smpub;
-
-/**
  * Head of DLL of actual keys, sorted by anchor.
  */
 static struct Key *keys_head;
@@ -201,13 +121,6 @@ static struct GNUNET_TIME_Relative duration;
 static int global_ret;
 
 /**
- * Number of worker threads to use. Default (0) is to use one per CPU core
- * available.
- * Length of the #workers array.
- */
-static unsigned int num_workers;
-
-/**
  * Time when the key update is executed.
  * Either the actual current time, or a pretended time.
  */
@@ -220,11 +133,6 @@ static struct GNUNET_TIME_Absolute now;
 static struct GNUNET_TIME_Absolute now_tmp;
 
 /**
- * Handle to the exchange's configuration
- */
-static const struct GNUNET_CONFIGURATION_Handle *kcfg;
-
-/**
  * Where do we store the keys?
  */
 static char *keydir;
@@ -242,400 +150,19 @@ static struct GNUNET_TIME_Relative overlap_duration;
 static struct GNUNET_TIME_Relative lookahead_sign;
 
 /**
- * Our listen socket.
- */
-static struct GNUNET_NETWORK_Handle *unix_sock;
-
-/**
- * Path where we are listening.
- */
-static char *unixpath;
-
-/**
- * Task run to accept new inbound connections.
- */
-static struct GNUNET_SCHEDULER_Task *read_task;
-
-/**
  * Task run to generate new keys.
  */
 static struct GNUNET_SCHEDULER_Task *keygen_task;
 
 /**
- * Head of DLL of clients connected to us.
- */
-static struct Client *clients_head;
-
-/**
- * Tail of DLL of clients connected to us.
- */
-static struct Client *clients_tail;
-
-/**
- * Head of DLL with pending signing operations.
- */
-static struct WorkItem *work_head;
-
-/**
- * Tail of DLL with pending signing operations.
- */
-static struct WorkItem *work_tail;
-
-/**
- * Lock for the work queue.
- */
-static pthread_mutex_t work_lock;
-
-/**
- * Condition variable for the semaphore of the work queue.
- */
-static pthread_cond_t work_cond = PTHREAD_COND_INITIALIZER;
-
-/**
- * Number of items in the work queue. Also used as the semaphore counter.
- */
-static unsigned long long work_counter;
-
-/**
- * Head of DLL with completed signing operations.
- */
-static struct WorkItem *done_head;
-
-/**
- * Tail of DLL with completed signing operations.
- */
-static struct WorkItem *done_tail;
-
-/**
- * Lock for the done queue.
- */
-static pthread_mutex_t done_lock;
-
-/**
- * Task waiting for work to be done.
- */
-static struct GNUNET_SCHEDULER_Task *done_task;
-
-/**
- * Signal used by threads to notify the #done_task that they
- * completed work that is now in the done queue.
- */
-static struct GNUNET_NETWORK_Handle *done_signal;
-
-/**
- * Set once we are in shutdown and workers should terminate.
- */
-static volatile bool in_shutdown;
-
-/**
- * Array of #num_workers sign_worker() threads.
- */
-static pthread_t *workers;
-
-
-/**
- * Main function of a worker thread that signs.
- *
- * @param cls NULL
- * @return NULL
- */
-static void *
-sign_worker (void *cls)
-{
-  (void) cls;
-  GNUNET_assert (0 == pthread_mutex_lock (&work_lock));
-  while (! in_shutdown)
-  {
-    struct WorkItem *wi;
-
-    while (NULL != (wi = work_head))
-    {
-      /* take work from queue */
-      GNUNET_CONTAINER_DLL_remove (work_head,
-                                   work_tail,
-                                   wi);
-      work_counter--;
-      GNUNET_assert (0 == pthread_mutex_unlock (&work_lock));
-      {
-        if (GNUNET_OK !=
-            GNUNET_CRYPTO_eddsa_sign_ (&wi->key->exchange_priv.eddsa_priv,
-                                       wi->purpose,
-                                       &wi->signature.eddsa_signature))
-          wi->ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
-        else
-          wi->ec = TALER_EC_NONE;
-      }
-      /* put completed work into done queue */
-      GNUNET_assert (0 == pthread_mutex_lock (&done_lock));
-      GNUNET_CONTAINER_DLL_insert (done_head,
-                                   done_tail,
-                                   wi);
-      GNUNET_assert (0 == pthread_mutex_unlock (&done_lock));
-      {
-        uint64_t val = GNUNET_htonll (1);
-
-        /* raise #done_signal */
-        if (sizeof(val) !=
-            write (GNUNET_NETWORK_get_fd (done_signal),
-                   &val,
-                   sizeof (val)))
-          GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
-                               "write(eventfd)");
-      }
-      GNUNET_assert (0 == pthread_mutex_lock (&work_lock));
-    }
-    if (in_shutdown)
-      break;
-    /* queue is empty, wait for work */
-    GNUNET_assert (0 ==
-                   pthread_cond_wait (&work_cond,
-                                      &work_lock));
-  }
-  GNUNET_assert (0 ==
-                 pthread_mutex_unlock (&work_lock));
-  return NULL;
-}
-
-
-/**
- * Free @a client, releasing all (remaining) state.
- *
- * @param[in] client data to free
- */
-static void
-free_client (struct Client *client)
-{
-  GNUNET_CONTAINER_DLL_remove (clients_head,
-                               clients_tail,
-                               client);
-  GNUNET_free (client);
-}
-
-
-/**
- * Function run to read incoming requests from a client.
- *
- * @param cls the `struct Client`
- */
-static void
-read_job (void *cls);
-
-
-/**
- * Free @a key. It must already have been removed from the DLL.
- *
- * @param[in] key the key to free
- */
-static void
-free_key (struct Key *key)
-{
-  GNUNET_free (key->filename);
-  GNUNET_free (key);
-}
-
-
-/**
- * Send a message starting with @a hdr to @a client.  We expect that
- * the client is mostly able to handle everything at whatever speed
- * we have (after all, the crypto should be the slow part). However,
- * especially on startup when we send all of our keys, it is possible
- * that the client cannot keep up. In that case, we throttle when
- * sending fails. This does not work with poll() as we cannot specify
- * the sendto() target address with poll(). So we nanosleep() instead.
- *
- * @param addr address where to send the message
- * @param addr_size number of bytes in @a addr
- * @param hdr beginning of the message, length indicated in size field
- * @return #GNUNET_OK on success
- */
-static int
-transmit (const struct sockaddr_un *addr,
-          socklen_t addr_size,
-          const struct GNUNET_MessageHeader *hdr)
-{
-  for (unsigned int i = 0; i<100; i++)
-  {
-    ssize_t ret = sendto (GNUNET_NETWORK_get_fd (unix_sock),
-                          hdr,
-                          ntohs (hdr->size),
-                          0 /* no flags => blocking! */,
-                          (const struct sockaddr *) addr,
-                          addr_size);
-    if ( (-1 == ret) &&
-         (EAGAIN == errno) )
-    {
-      /* _Maybe_ with blocking sendto(), this should no
-         longer be needed; still keeping it just in case. */
-      /* Wait a bit, in case client is just too slow */
-      struct timespec req = {
-        .tv_sec = 0,
-        .tv_nsec = 1000
-      };
-      nanosleep (&req, NULL);
-      continue;
-    }
-    if (ret == ntohs (hdr->size))
-      return GNUNET_OK;
-    if (ret != ntohs (hdr->size))
-      break;
-  }
-  GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
-                       "sendto");
-  return GNUNET_SYSERR;
-}
-
-
-/**
- * Process completed tasks that are in the #done_head queue, sending
- * the result back to the client (and resuming the client).
- *
- * @param cls NULL
+ * Lock for the keys queue.
  */
-static void
-handle_done (void *cls)
-{
-  uint64_t data;
-  (void) cls;
-
-  /* consume #done_signal */
-  if (sizeof (data) !=
-      read (GNUNET_NETWORK_get_fd (done_signal),
-            &data,
-            sizeof (data)))
-    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
-                         "read(eventfd)");
-  done_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
-                                             done_signal,
-                                             &handle_done,
-                                             NULL);
-  GNUNET_assert (0 == pthread_mutex_lock (&done_lock));
-  while (NULL != done_head)
-  {
-    struct WorkItem *wi = done_head;
-
-    GNUNET_CONTAINER_DLL_remove (done_head,
-                                 done_tail,
-                                 wi);
-    GNUNET_assert (0 == pthread_mutex_unlock (&done_lock));
-    if (TALER_EC_NONE != wi->ec)
-    {
-      struct TALER_CRYPTO_EddsaSignFailure sf = {
-        .header.size = htons (sizeof (sf)),
-        .header.type = htons (TALER_HELPER_EDDSA_MT_RES_SIGN_FAILURE),
-        .ec = htonl (wi->ec)
-      };
-
-      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
-                  "Signing request %p failed, worker failed to produce signature\n",
-                  wi);
-      (void) transmit (&wi->addr,
-                       wi->addr_size,
-                       &sf.header);
-    }
-    else
-    {
-      struct TALER_CRYPTO_EddsaSignResponse sr = {
-        .header.size = htons (sizeof (sr)),
-        .header.type = htons (TALER_HELPER_EDDSA_MT_RES_SIGNATURE),
-        .exchange_pub = wi->key->exchange_pub,
-        .exchange_sig = wi->signature
-      };
-
-      (void) transmit (&wi->addr,
-                       wi->addr_size,
-                       &sr.header);
-    }
-    {
-      struct Key *key = wi->key;
-
-      key->rc--;
-      if ( (0 == key->rc) &&
-           (key->purge) )
-        free_key (key);
-    }
-    GNUNET_free (wi->purpose);
-    GNUNET_free (wi);
-    GNUNET_assert (0 == pthread_mutex_lock (&done_lock));
-  }
-  GNUNET_assert (0 == pthread_mutex_unlock (&done_lock));
-
-}
-
+static pthread_mutex_t keys_lock;
 
 /**
- * Handle @a client request @a sr to create signature. Create the
- * signature using the respective key and return the result to
- * the client.
- *
- * @param addr address of the client making the request
- * @param addr_size number of bytes in @a addr
- * @param sr the request details
+ * Current key generation.
  */
-static void
-handle_sign_request (const struct sockaddr_un *addr,
-                     socklen_t addr_size,
-                     const struct TALER_CRYPTO_EddsaSignRequest *sr)
-{
-  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose = &sr->purpose;
-  struct WorkItem *wi;
-  size_t purpose_size = ntohs (sr->header.size) - sizeof (*sr)
-                        + sizeof (*purpose);
-
-  if (purpose_size != htonl (purpose->size))
-  {
-    struct TALER_CRYPTO_EddsaSignFailure sf = {
-      .header.size = htons (sizeof (sr)),
-      .header.type = htons (TALER_HELPER_EDDSA_MT_RES_SIGN_FAILURE),
-      .ec = htonl (TALER_EC_GENERIC_PARAMETER_MALFORMED)
-    };
-
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Signing request failed, request malformed\n");
-    (void) transmit (addr,
-                     addr_size,
-                     &sf.header);
-    return;
-  }
-  {
-    struct GNUNET_TIME_Absolute now;
-
-    now = GNUNET_TIME_absolute_get ();
-    if ( (now.abs_value_us >= keys_head->anchor.abs_value_us) &&
-         (now.abs_value_us < keys_head->anchor.abs_value_us
-          + duration.rel_value_us) )
-      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-                  "Signing at %llu with key valid from %llu to %llu\n",
-                  (unsigned long long) now.abs_value_us,
-                  (unsigned long long) keys_head->anchor.abs_value_us,
-                  (unsigned long long) keys_head->anchor.abs_value_us
-                  + duration.rel_value_us);
-    else
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                  "Signing at %llu with key valid from %llu to %llu\n",
-                  (unsigned long long) now.abs_value_us,
-                  (unsigned long long) keys_head->anchor.abs_value_us,
-                  (unsigned long long) keys_head->anchor.abs_value_us
-                  + duration.rel_value_us);
-  }
-  wi = GNUNET_new (struct WorkItem);
-  wi->addr = *addr;
-  wi->addr_size = addr_size;
-  wi->key = keys_head;
-  keys_head->rc++;
-  wi->purpose = GNUNET_memdup (purpose,
-                               purpose_size);
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Received request to sign over %u bytes, queueing as %p\n",
-              (unsigned int) purpose_size,
-              wi);
-  GNUNET_assert (0 == pthread_mutex_lock (&work_lock));
-  work_counter++;
-  GNUNET_CONTAINER_DLL_insert (work_head,
-                               work_tail,
-                               wi);
-  GNUNET_assert (0 == pthread_cond_signal (&work_cond));
-  GNUNET_assert (0 == pthread_mutex_unlock (&work_lock));
-}
+static uint64_t key_gen;
 
 
 /**
@@ -645,8 +172,8 @@ handle_sign_request (const struct sockaddr_un *addr,
  * @param key the key to notify @a client about
  * @return #GNUNET_OK on success
  */
-static int
-notify_client_key_add (struct Client *client,
+static enum GNUNET_GenericReturnValue
+notify_client_key_add (struct TES_Client *client,
                        const struct Key *key)
 {
   struct TALER_CRYPTO_EddsaKeyAvailableNotification an = {
@@ -655,23 +182,21 @@ notify_client_key_add (struct Client *client,
     .anchor_time = GNUNET_TIME_absolute_hton (key->anchor),
     .duration = GNUNET_TIME_relative_hton (duration),
     .exchange_pub = key->exchange_pub,
-    .secm_pub = smpub
+    .secm_pub = TES_smpub
   };
 
   TALER_exchange_secmod_eddsa_sign (&key->exchange_pub,
                                     key->anchor,
                                     duration,
-                                    &smpriv,
+                                    &TES_smpriv,
                                     &an.secm_sig);
   if (GNUNET_OK !=
-      transmit (&client->addr,
-                client->addr_size,
-                &an.header))
+      TES_transmit (client->csock,
+                    &an.header))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Client %s must have disconnected\n",
-                client->addr.sun_path);
-    free_client (client);
+                "Client %p must have disconnected\n",
+                client);
     return GNUNET_SYSERR;
   }
   return GNUNET_OK;
@@ -685,8 +210,8 @@ notify_client_key_add (struct Client *client,
  * @param key the key to notify @a client about
  * @return #GNUNET_OK on success
  */
-static int
-notify_client_key_del (struct Client *client,
+static enum GNUNET_GenericReturnValue
+notify_client_key_del (struct TES_Client *client,
                        const struct Key *key)
 {
   struct TALER_CRYPTO_EddsaKeyPurgeNotification pn = {
@@ -696,14 +221,12 @@ notify_client_key_del (struct Client *client,
   };
 
   if (GNUNET_OK !=
-      transmit (&client->addr,
-                client->addr_size,
-                &pn.header))
+      TES_transmit (client->csock,
+                    &pn.header))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Client %s must have disconnected\n",
-                client->addr.sun_path);
-    free_client (client);
+                "Client %p must have disconnected\n",
+                client);
     return GNUNET_SYSERR;
   }
   return GNUNET_OK;
@@ -711,13 +234,116 @@ notify_client_key_del (struct Client *client,
 
 
 /**
+ * Handle @a client request @a sr to create signature. Create the
+ * signature using the respective key and return the result to
+ * the client.
+ *
+ * @param client the client making the request
+ * @param sr the request details
+ * @return #GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+handle_sign_request (struct TES_Client *client,
+                     const struct TALER_CRYPTO_EddsaSignRequest *sr)
+{
+  const struct GNUNET_CRYPTO_EccSignaturePurpose *purpose = &sr->purpose;
+  size_t purpose_size = ntohs (sr->header.size) - sizeof (*sr)
+                        + sizeof (*purpose);
+  struct Key *key;
+  struct TALER_CRYPTO_EddsaSignResponse sres = {
+    .header.size = htons (sizeof (sres)),
+    .header.type = htons (TALER_HELPER_EDDSA_MT_RES_SIGNATURE)
+  };
+  enum TALER_ErrorCode ec;
+
+  if (purpose_size != htonl (purpose->size))
+  {
+    struct TALER_CRYPTO_EddsaSignFailure sf = {
+      .header.size = htons (sizeof (sr)),
+      .header.type = htons (TALER_HELPER_EDDSA_MT_RES_SIGN_FAILURE),
+      .ec = htonl (TALER_EC_GENERIC_PARAMETER_MALFORMED)
+    };
+
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Signing request failed, request malformed\n");
+    return TES_transmit (client->csock,
+                         &sf.header);
+  }
+
+  GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
+  key = keys_head;
+  while ( (NULL != key) &&
+          (GNUNET_TIME_absolute_is_past (
+             GNUNET_TIME_absolute_add (key->anchor,
+                                       duration))) )
+  {
+    struct Key *nxt = key->next;
+
+    if (0 != key->rc)
+      break; /* do later */
+    GNUNET_CONTAINER_DLL_remove (keys_head,
+                                 keys_tail,
+                                 key);
+    if ( (! key->purge) &&
+         (0 != unlink (key->filename)) )
+      GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                                "unlink",
+                                key->filename);
+    GNUNET_free (key->filename);
+    GNUNET_free (key);
+    key = nxt;
+  }
+  if (NULL == key)
+  {
+    GNUNET_break (0);
+    ec = TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING;
+  }
+  else
+  {
+    GNUNET_assert (key->rc < UINT_MAX);
+    key->rc++;
+    GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+
+    if (GNUNET_OK !=
+        GNUNET_CRYPTO_eddsa_sign_ (&key->exchange_priv.eddsa_priv,
+                                   purpose,
+                                   &sres.exchange_sig.eddsa_signature))
+      ec = TALER_EC_GENERIC_INTERNAL_INVARIANT_FAILURE;
+    else
+      ec = TALER_EC_NONE;
+    sres.exchange_pub = key->exchange_pub;
+    GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
+    GNUNET_assert (key->rc > 0);
+    key->rc--;
+  }
+  GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+  if (TALER_EC_NONE != ec)
+  {
+    struct TALER_CRYPTO_EddsaSignFailure sf = {
+      .header.size = htons (sizeof (sf)),
+      .header.type = htons (TALER_HELPER_EDDSA_MT_RES_SIGN_FAILURE),
+      .ec = htonl ((uint32_t) ec)
+    };
+
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Signing request %p failed, worker failed to produce signature\n",
+                client);
+    return TES_transmit (client->csock,
+                         &sf.header);
+  }
+  return TES_transmit (client->csock,
+                       &sres.header);
+}
+
+
+/**
  * Initialize key material for key @a key (also on disk).
  *
  * @param[in,out] key to compute key material for
  * @param position where in the DLL will the @a key go
  * @return #GNUNET_OK on success
  */
-static int
+static enum GNUNET_GenericReturnValue
 setup_key (struct Key *key,
            struct Key *position)
 {
@@ -746,54 +372,58 @@ setup_key (struct Key *key,
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Setup fresh private key in `%s'\n",
               key->filename);
+  key->key_gen = key_gen;
   key->exchange_priv.eddsa_priv = priv;
   key->exchange_pub.eddsa_pub = pub;
   GNUNET_CONTAINER_DLL_insert_after (keys_head,
                                      keys_tail,
                                      position,
                                      key);
+  return GNUNET_OK;
+}
 
-  /* tell clients about new key */
-  {
-    struct Client *nxt;
 
-    for (struct Client *client = clients_head;
-         NULL != client;
-         client = nxt)
-    {
-      nxt = client->next;
-      if (GNUNET_OK !=
-          notify_client_key_add (client,
-                                 key))
-      {
-        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                    "Failed to notify client about new key, client dropped\n");
-      }
-    }
-  }
-  return GNUNET_OK;
+/**
+ * The validity period of a key @a key has expired. Purge it.
+ *
+ * @param[in] key expired or revoked key to purge
+ */
+static void
+purge_key (struct Key *key)
+{
+  if (key->purge)
+    return;
+  if (0 != unlink (key->filename))
+    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
+                              "unlink",
+                              key->filename);
+  key->purge = true;
+  key->key_gen = key_gen;
+  GNUNET_free (key->filename);
 }
 
 
 /**
- * A client informs us that a key has been revoked.
+ * A @a client informs us that a key has been revoked.
  * Check if the key is still in use, and if so replace (!)
  * it with a fresh key.
  *
- * @param addr address of the client making the request
- * @param addr_size number of bytes in @a addr
+ * @param client the client making the request
  * @param rr the revocation request
+ * @return #GNUNET_OK on success
  */
-static void
-handle_revoke_request (const struct sockaddr_un *addr,
-                       socklen_t addr_size,
+static enum GNUNET_GenericReturnValue
+handle_revoke_request (struct TES_Client *client,
                        const struct TALER_CRYPTO_EddsaRevokeRequest *rr)
 {
   struct Key *key;
   struct Key *nkey;
 
   key = NULL;
-  for (struct Key *pos = keys_head; NULL != pos; pos = pos->next)
+  GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
+  for (struct Key *pos = keys_head;
+       NULL != pos;
+       pos = pos->next)
     if (0 == GNUNET_memcmp (&pos->exchange_pub,
                             &rr->exchange_pub))
     {
@@ -802,16 +432,18 @@ handle_revoke_request (const struct sockaddr_un *addr,
     }
   if (NULL == key)
   {
+    GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Revocation request ignored, key unknown\n");
-    return;
+    return GNUNET_OK;
   }
 
-  /* kill existing key, done first to ensure this always happens */
-  if (0 != unlink (key->filename))
-    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
-                              "unlink",
-                              key->filename);
+  key_gen++;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Revoking key %p, bumping generation to %llu\n",
+              key,
+              (unsigned long long) key_gen);
+  purge_key (key);
 
   /* Setup replacement key */
   nkey = GNUNET_new (struct Key);
@@ -820,157 +452,146 @@ handle_revoke_request (const struct sockaddr_un *addr,
       setup_key (nkey,
                  key))
   {
+    GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
     GNUNET_break (0);
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = 44;
-    return;
+    global_ret = EXIT_FAILURE;
+    return GNUNET_SYSERR;
   }
+  GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+  TES_wake_clients ();
+  return GNUNET_OK;
+}
 
-  /* get rid of the old key */
-  key->purge = true;
-  GNUNET_CONTAINER_DLL_remove (keys_head,
-                               keys_tail,
-                               key);
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Revocation complete\n");
 
-  /* Tell clients this key is gone */
-  {
-    struct Client *nxt;
+/**
+ * Handle @a hdr message received from @a client.
+ *
+ * @param client the client that received the message
+ * @param hdr message that was received
+ * @return #GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+eddsa_work_dispatch (struct TES_Client *client,
+                     const struct GNUNET_MessageHeader *hdr)
+{
+  uint16_t msize = ntohs (hdr->size);
 
-    for (struct Client *client = clients_head;
-         NULL != client;
-         client = nxt)
+  switch (ntohs (hdr->type))
+  {
+  case TALER_HELPER_EDDSA_MT_REQ_SIGN:
+    if (msize < sizeof (struct TALER_CRYPTO_EddsaSignRequest))
     {
-      nxt = client->next;
-      if (GNUNET_OK !=
-          notify_client_key_del (client,
-                                 key))
-        GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                    "Failed to notify client about revoked key, client dropped\n");
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
     }
+    return handle_sign_request (
+      client,
+      (const struct TALER_CRYPTO_EddsaSignRequest *) hdr);
+  case TALER_HELPER_EDDSA_MT_REQ_REVOKE:
+    if (msize != sizeof (struct TALER_CRYPTO_EddsaRevokeRequest))
+    {
+      GNUNET_break_op (0);
+      return GNUNET_SYSERR;
+    }
+    return handle_revoke_request (
+      client,
+      (const struct TALER_CRYPTO_EddsaRevokeRequest *) hdr);
+  default:
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
   }
-  if (0 == key->rc)
-    free_key (key);
 }
 
 
-static void
-read_job (void *cls)
+/**
+ * Send our initial key set to @a client together with the
+ * "sync" terminator.
+ *
+ * @param client the client to inform
+ * @return #GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+eddsa_client_init (struct TES_Client *client)
 {
-  struct Client *client = cls;
-  char buf[65536];
-  ssize_t buf_size;
-  const struct GNUNET_MessageHeader *hdr;
-  struct sockaddr_un addr;
-  socklen_t addr_size = sizeof (addr);
-
-  read_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
-                                             unix_sock,
-                                             &read_job,
-                                             NULL);
-  buf_size = GNUNET_NETWORK_socket_recvfrom (unix_sock,
-                                             buf,
-                                             sizeof (buf),
-                                             (struct sockaddr *) &addr,
-                                             &addr_size);
-  if (-1 == buf_size)
-  {
-    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
-                         "recv");
-    return;
-  }
-  if (0 == buf_size)
+  GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
+  for (struct Key *key = keys_head;
+       NULL != key;
+       key = key->next)
   {
-    return;
-  }
-  if (buf_size < sizeof (struct GNUNET_MessageHeader))
-  {
-    GNUNET_break_op (0);
-    return;
-  }
-  hdr = (const struct GNUNET_MessageHeader *) buf;
-  if (ntohs (hdr->size) != buf_size)
-  {
-    GNUNET_break_op (0);
-    free_client (client);
-    return;
+    if (GNUNET_OK !=
+        notify_client_key_add (client,
+                               key))
+    {
+      GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
+    }
   }
-  switch (ntohs (hdr->type))
+  client->key_gen = key_gen;
+  GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
   {
-  case TALER_HELPER_EDDSA_MT_REQ_INIT:
-    if (ntohs (hdr->size) != sizeof (struct GNUNET_MessageHeader))
+    struct GNUNET_MessageHeader synced = {
+      .type = htons (TALER_HELPER_EDDSA_SYNCED),
+      .size = htons (sizeof (synced))
+    };
+
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Client %p synced\n",
+                client);
+    if (GNUNET_OK !=
+        TES_transmit (client->csock,
+                      &synced))
     {
-      GNUNET_break_op (0);
-      return;
+      GNUNET_break (0);
+      return GNUNET_SYSERR;
     }
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Notify @a client about all changes to the keys since
+ * the last generation known to the @a client.
+ *
+ * @param client the client to notify
+ * @return #GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+eddsa_update_client_keys (struct TES_Client *client)
+{
+  GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
+  for (struct Key *key = keys_head;
+       NULL != key;
+       key = key->next)
+  {
+    if (key->key_gen <= client->key_gen)
+      continue;
+    if (key->purge)
     {
-      struct Client *client;
-
-      client = GNUNET_new (struct Client);
-      client->addr = addr;
-      client->addr_size = addr_size;
-      GNUNET_CONTAINER_DLL_insert (clients_head,
-                                   clients_tail,
-                                   client);
-      for (struct Key *key = keys_head;
-           NULL != key;
-           key = key->next)
-      {
-        if (GNUNET_OK !=
-            notify_client_key_add (client,
-                                   key))
-        {
-          /* client died, skip the rest */
-          client = NULL;
-          break;
-        }
-      }
-      if (NULL != client)
+      if (GNUNET_OK !=
+          notify_client_key_del (client,
+                                 key))
       {
-        struct GNUNET_MessageHeader synced = {
-          .type = htons (TALER_HELPER_EDDSA_SYNCED),
-          .size = htons (sizeof (synced))
-        };
-
-        if (GNUNET_OK !=
-            transmit (&client->addr,
-                      client->addr_size,
-                      &synced))
-        {
-          GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                      "Client %s must have disconnected\n",
-                      client->addr.sun_path);
-          free_client (client);
-        }
+        GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+        return GNUNET_SYSERR;
       }
     }
-    break;
-  case TALER_HELPER_EDDSA_MT_REQ_SIGN:
-    if (ntohs (hdr->size) < sizeof (struct TALER_CRYPTO_EddsaSignRequest))
-    {
-      GNUNET_break_op (0);
-      return;
-    }
-    handle_sign_request (&addr,
-                         addr_size,
-                         (const struct TALER_CRYPTO_EddsaSignRequest *) buf);
-    break;
-  case TALER_HELPER_EDDSA_MT_REQ_REVOKE:
-    if (ntohs (hdr->size) != sizeof (struct TALER_CRYPTO_EddsaRevokeRequest))
+    else
     {
-      GNUNET_break_op (0);
-      return;
+      if (GNUNET_OK !=
+          notify_client_key_add (client,
+                                 key))
+      {
+        GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+        return GNUNET_SYSERR;
+      }
     }
-    handle_revoke_request (&addr,
-                           addr_size,
-                           (const struct
-                            TALER_CRYPTO_EddsaRevokeRequest *) buf);
-    break;
-  default:
-    GNUNET_break_op (0);
-    return;
   }
+  client->key_gen = key_gen;
+  GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+  return GNUNET_OK;
 }
 
 
@@ -979,7 +600,7 @@ read_job (void *cls)
  *
  * @return #GNUNET_OK on success
  */
-static int
+static enum GNUNET_GenericReturnValue
 create_key (void)
 {
   struct Key *key;
@@ -1010,7 +631,7 @@ create_key (void)
     GNUNET_break (0);
     GNUNET_free (key);
     GNUNET_SCHEDULER_shutdown ();
-    global_ret = 42;
+    global_ret = EXIT_FAILURE;
     return GNUNET_SYSERR;
   }
   return GNUNET_OK;
@@ -1040,55 +661,6 @@ key_action_time (void)
 
 
 /**
- * The validity period of a key @a key has expired. Purge it.
- *
- * @param[in] key expired key to purge and free
- */
-static void
-purge_key (struct Key *key)
-{
-  struct Client *nxt;
-
-  for (struct Client *client = clients_head;
-       NULL != client;
-       client = nxt)
-  {
-    nxt = client->next;
-    if (GNUNET_OK !=
-        notify_client_key_del (client,
-                               key))
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                  "Failed to notify client about purged key, client dropped\n");
-    }
-  }
-  GNUNET_CONTAINER_DLL_remove (keys_head,
-                               keys_tail,
-                               key);
-  if (0 != unlink (key->filename))
-  {
-    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_ERROR,
-                              "unlink",
-                              key->filename);
-  }
-  else
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Purged expired private key `%s'\n",
-                key->filename);
-  }
-  GNUNET_free (key->filename);
-  if (0 != key->rc)
-  {
-    /* delay until all signing threads are done with this key */
-    key->purge = true;
-    return;
-  }
-  GNUNET_free (key);
-}
-
-
-/**
  * Create new keys and expire ancient keys.
  *
  * @param cls NULL
@@ -1096,35 +668,52 @@ purge_key (struct Key *key)
 static void
 update_keys (void *cls)
 {
-  (void) cls;
+  bool wake = false;
 
+  (void) cls;
   keygen_task = NULL;
+  GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
   /* create new keys */
   while ( (NULL == keys_tail) ||
-          (0 ==
-           GNUNET_TIME_absolute_get_remaining (
-             GNUNET_TIME_absolute_subtract (
-               GNUNET_TIME_absolute_subtract (
-                 GNUNET_TIME_absolute_add (keys_tail->anchor,
-                                           duration),
-                 lookahead_sign),
-               overlap_duration)).rel_value_us) )
+          GNUNET_TIME_absolute_is_past (
+            GNUNET_TIME_absolute_subtract (
+              GNUNET_TIME_absolute_subtract (
+                GNUNET_TIME_absolute_add (keys_tail->anchor,
+                                          duration),
+                lookahead_sign),
+              overlap_duration)) )
   {
+    if (! wake)
+    {
+      key_gen++;
+      wake = true;
+    }
     if (GNUNET_OK !=
         create_key ())
     {
+      GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
       GNUNET_break (0);
+      global_ret = EXIT_FAILURE;
       GNUNET_SCHEDULER_shutdown ();
       return;
     }
   }
   /* remove expired keys */
   while ( (NULL != keys_head) &&
-          (0 ==
-           GNUNET_TIME_absolute_get_remaining
-             (GNUNET_TIME_absolute_add (keys_head->anchor,
-                                        duration)).rel_value_us) )
+          GNUNET_TIME_absolute_is_past (
+            GNUNET_TIME_absolute_add (keys_head->anchor,
+                                      duration)))
+  {
+    if (! wake)
+    {
+      key_gen++;
+      wake = true;
+    }
     purge_key (keys_head);
+  }
+  GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
+  if (wake)
+    TES_wake_clients ();
   keygen_task = GNUNET_SCHEDULER_add_at (key_action_time (),
                                          &update_keys,
                                          NULL);
@@ -1137,8 +726,9 @@ update_keys (void *cls)
  * @param filename name of the file we are parsing, for logging
  * @param buf key material
  * @param buf_size number of bytes in @a buf
+ * @return #GNUNET_OK on success
  */
-static void
+static enum GNUNET_GenericReturnValue
 parse_key (const char *filename,
            const void *buf,
            size_t buf_size)
@@ -1155,7 +745,7 @@ parse_key (const char *filename,
   {
     /* File in a directory without '/' in the name, this makes no sense. */
     GNUNET_break (0);
-    return;
+    return GNUNET_SYSERR;
   }
   anchor_s++;
   if (1 != sscanf (anchor_s,
@@ -1167,7 +757,7 @@ parse_key (const char *filename,
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Filename `%s' invalid for key file, skipping\n",
                 filename);
-    return;
+    return GNUNET_SYSERR;
   }
   anchor.abs_value_us = anchor_ll * GNUNET_TIME_UNIT_SECONDS.rel_value_us;
   if (anchor_ll != anchor.abs_value_us / GNUNET_TIME_UNIT_SECONDS.rel_value_us)
@@ -1176,7 +766,7 @@ parse_key (const char *filename,
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "Filename `%s' invalid for key file, skipping\n",
                 filename);
-    return;
+    return GNUNET_SYSERR;
   }
   if (buf_size != sizeof (priv))
   {
@@ -1184,7 +774,7 @@ parse_key (const char *filename,
     GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
                 "File `%s' is malformed, skipping\n",
                 filename);
-    return;
+    return GNUNET_SYSERR;
   }
   memcpy (&priv,
           buf,
@@ -1197,11 +787,13 @@ parse_key (const char *filename,
 
     GNUNET_CRYPTO_eddsa_key_get_public (&priv,
                                         &pub);
+    GNUNET_assert (0 == pthread_mutex_lock (&keys_lock));
     key = GNUNET_new (struct Key);
     key->exchange_priv.eddsa_priv = priv;
     key->exchange_pub.eddsa_pub = pub;
     key->anchor = anchor;
     key->filename = GNUNET_strdup (filename);
+    key->key_gen = key_gen;
     before = NULL;
     for (struct Key *pos = keys_head;
          NULL != pos;
@@ -1215,10 +807,12 @@ parse_key (const char *filename,
                                        keys_tail,
                                        before,
                                        key);
+    GNUNET_assert (0 == pthread_mutex_unlock (&keys_lock));
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Imported key from `%s'\n",
                 filename);
   }
+  return GNUNET_OK;
 }
 
 
@@ -1228,7 +822,7 @@ parse_key (const char *filename,
  * @param cls NULL
  * @param filename name of a file in the directory
  */
-static int
+static enum GNUNET_GenericReturnValue
 import_key (void *cls,
             const char *filename)
 {
@@ -1326,9 +920,9 @@ import_key (void *cls,
     GNUNET_DISK_file_close (fh);
     return GNUNET_OK;
   }
-  parse_key (filename,
-             ptr,
-             (size_t) sbuf.st_size);
+  (void) parse_key (filename,
+                    ptr,
+                    (size_t) sbuf.st_size);
   GNUNET_DISK_file_unmap (map);
   GNUNET_DISK_file_close (fh);
   return GNUNET_OK;
@@ -1336,15 +930,16 @@ import_key (void *cls,
 
 
 /**
- * Load the various duration values from #kcfg.
+ * Load the various duration values from @a kcfg.
  *
+ * @param cfg configuration to use
  * @return #GNUNET_OK on success
  */
-static int
-load_durations (void)
+static enum GNUNET_GenericReturnValue
+load_durations (const struct GNUNET_CONFIGURATION_Handle *cfg)
 {
   if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_time (kcfg,
+      GNUNET_CONFIGURATION_get_value_time (cfg,
                                            "taler-exchange-secmod-eddsa",
                                            "OVERLAP_DURATION",
                                            &overlap_duration))
@@ -1355,7 +950,7 @@ load_durations (void)
     return GNUNET_SYSERR;
   }
   if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_time (kcfg,
+      GNUNET_CONFIGURATION_get_value_time (cfg,
                                            "taler-exchange-secmod-eddsa",
                                            "DURATION",
                                            &duration))
@@ -1368,7 +963,7 @@ load_durations (void)
   GNUNET_TIME_round_rel (&overlap_duration);
 
   if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_time (kcfg,
+      GNUNET_CONFIGURATION_get_value_time (cfg,
                                            "taler-exchange-secmod-eddsa",
                                            "LOOKAHEAD_SIGN",
                                            &lookahead_sign))
@@ -1392,51 +987,12 @@ static void
 do_shutdown (void *cls)
 {
   (void) cls;
-  if (NULL != read_task)
-  {
-    GNUNET_SCHEDULER_cancel (read_task);
-    read_task = NULL;
-  }
-  if (NULL != unix_sock)
-  {
-    GNUNET_break (GNUNET_OK ==
-                  GNUNET_NETWORK_socket_close (unix_sock));
-    unix_sock = NULL;
-  }
-  if (0 != unlink (unixpath))
-  {
-    GNUNET_log_strerror_file (GNUNET_ERROR_TYPE_WARNING,
-                              "unlink",
-                              unixpath);
-  }
-  GNUNET_free (unixpath);
+  TES_listen_stop ();
   if (NULL != keygen_task)
   {
     GNUNET_SCHEDULER_cancel (keygen_task);
     keygen_task = NULL;
   }
-  if (NULL != done_task)
-  {
-    GNUNET_SCHEDULER_cancel (done_task);
-    done_task = NULL;
-  }
-  /* shut down worker threads */
-  if (NULL != workers)
-  {
-    GNUNET_assert (0 == pthread_mutex_lock (&work_lock));
-    in_shutdown = true;
-    GNUNET_assert (0 == pthread_cond_broadcast (&work_cond));
-    GNUNET_assert (0 == pthread_mutex_unlock (&work_lock));
-    for (unsigned int i = 0; i<num_workers; i++)
-      GNUNET_assert (0 == pthread_join (workers[i],
-                                        NULL));
-  }
-  if (NULL != done_signal)
-  {
-    GNUNET_break (GNUNET_OK ==
-                  GNUNET_NETWORK_socket_close (done_signal));
-    done_signal = NULL;
-  }
 }
 
 
@@ -1454,10 +1010,15 @@ run (void *cls,
      const char *cfgfile,
      const struct GNUNET_CONFIGURATION_Handle *cfg)
 {
+  static struct TES_Callbacks cb = {
+    .dispatch = eddsa_work_dispatch,
+    .updater = eddsa_update_client_keys,
+    .init = eddsa_client_init
+  };
+
   (void) cls;
   (void) args;
   (void) cfgfile;
-  kcfg = cfg;
   if (now.abs_value_us != now_tmp.abs_value_us)
   {
     /* The user gave "--now", use it! */
@@ -1469,48 +1030,14 @@ run (void *cls,
     now = GNUNET_TIME_absolute_get ();
   }
   GNUNET_TIME_round_abs (&now);
-
-  {
-    char *pfn;
-
-    if (GNUNET_OK !=
-        GNUNET_CONFIGURATION_get_value_filename (kcfg,
-                                                 "taler-exchange-secmod-eddsa",
-                                                 "SM_PRIV_KEY",
-                                                 &pfn))
-    {
-      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
-                                 "taler-exchange-secmod-eddsa",
-                                 "SM_PRIV_KEY");
-      global_ret = 1;
-      return;
-    }
-    if (GNUNET_SYSERR ==
-        GNUNET_CRYPTO_eddsa_key_from_file (pfn,
-                                           GNUNET_YES,
-                                           &smpriv.eddsa_priv))
-    {
-      GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
-                                 "taler-exchange-secmod-rsa",
-                                 "SM_PRIV_KEY",
-                                 "Could not use file to persist private key");
-      GNUNET_free (pfn);
-      global_ret = 1;
-      return;
-    }
-    GNUNET_free (pfn);
-    GNUNET_CRYPTO_eddsa_key_get_public (&smpriv.eddsa_priv,
-                                        &smpub.eddsa_pub);
-  }
-
   if (GNUNET_OK !=
-      load_durations ())
+      load_durations (cfg))
   {
-    global_ret = 1;
+    global_ret = EXIT_NOTCONFIGURED;
     return;
   }
   if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_filename (kcfg,
+      GNUNET_CONFIGURATION_get_value_filename (cfg,
                                                "taler-exchange-secmod-eddsa",
                                                "KEY_DIR",
                                                &keydir))
@@ -1518,131 +1045,29 @@ run (void *cls,
     GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
                                "taler-exchange-secmod-eddsa",
                                "KEY_DIR");
-    global_ret = 1;
+    global_ret = EXIT_NOTCONFIGURED;
     return;
   }
-
-  /* Create client directory and set permissions. */
-  {
-    char *client_dir;
-
-    if (GNUNET_OK !=
-        GNUNET_CONFIGURATION_get_value_filename (kcfg,
-                                                 "taler-exchange-secmod-eddsa",
-                                                 "CLIENT_DIR",
-                                                 &client_dir))
-    {
-      GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+  global_ret = TES_listen_start (cfg,
                                  "taler-exchange-secmod-eddsa",
-                                 "CLIENT_DIR");
-      global_ret = 3;
-      return;
-    }
-
-    if (GNUNET_OK != GNUNET_DISK_directory_create (client_dir))
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                  "Can't create client directory (%s)\n",
-                  client_dir);
-      global_ret = 3;
-      return;
-    }
-    /* Set sticky group bit, so that clients will be writeable by the current service. */
-    if (0 != chmod (client_dir,
-                    S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IWGRP | S_IXGRP
-                    | S_ISGID))
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                  "Can't set permissions for client directory (%s)\n",
-                  client_dir);
-      global_ret = 3;
-      return;
-    }
-
-    GNUNET_free (client_dir);
-  }
-
-  if (GNUNET_OK !=
-      GNUNET_CONFIGURATION_get_value_filename (kcfg,
-                                               "taler-exchange-secmod-eddsa",
-                                               "UNIXPATH",
-                                               &unixpath))
-  {
-    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
-                               "taler-exchange-secmod-eddsa",
-                               "UNIXPATH");
-    global_ret = 3;
-    return;
-  }
-
-  GNUNET_assert (NULL != unixpath);
-  unix_sock = TES_open_socket (unixpath);
-
-  if (NULL == unix_sock)
-  {
-    GNUNET_free (unixpath);
-    global_ret = 2;
+                                 &cb);
+  if (0 != global_ret)
     return;
-  }
-
   GNUNET_SCHEDULER_add_shutdown (&do_shutdown,
                                  NULL);
-
   /* Load keys */
   GNUNET_break (GNUNET_OK ==
                 GNUNET_DISK_directory_create (keydir));
   GNUNET_DISK_directory_scan (keydir,
                               &import_key,
                               NULL);
-  /* start job to accept incoming requests on 'sock' */
-  read_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
-                                             unix_sock,
-                                             &read_job,
-                                             NULL);
-  /* start job to keep keys up-to-date; MUST be run before the #read_task,
+
+  /* start job to keep keys up-to-date; MUST be run before the #listen_task,
      hence with priority. */
   keygen_task = GNUNET_SCHEDULER_add_with_priority (
     GNUNET_SCHEDULER_PRIORITY_URGENT,
     &update_keys,
     NULL);
-
-  /* start job to handle completed work */
-  {
-    int fd;
-
-    fd = eventfd (0,
-                  EFD_NONBLOCK | EFD_CLOEXEC);
-    if (-1 == fd)
-    {
-      GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
-                           "eventfd");
-      global_ret = 6;
-      GNUNET_SCHEDULER_shutdown ();
-      return;
-    }
-    done_signal = GNUNET_NETWORK_socket_box_native (fd);
-  }
-  done_task = GNUNET_SCHEDULER_add_read_net (GNUNET_TIME_UNIT_FOREVER_REL,
-                                             done_signal,
-                                             &handle_done,
-                                             NULL);
-
-  /* start crypto workers */
-  if (0 == num_workers)
-    num_workers = sysconf (_SC_NPROCESSORS_CONF);
-  if (0 == num_workers)
-    num_workers = 1;
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Starting %u crypto workers\n",
-              num_workers);
-  workers = GNUNET_new_array (num_workers,
-                              pthread_t);
-  for (unsigned int i = 0; i<num_workers; i++)
-    GNUNET_assert (0 ==
-                   pthread_create (&workers[i],
-                                   NULL,
-                                   &sign_worker,
-                                   NULL));
 }
 
 
@@ -1660,11 +1085,6 @@ main (int argc,
   struct GNUNET_GETOPT_CommandLineOption options[] = {
     GNUNET_GETOPT_option_timetravel ('T',
                                      "timetravel"),
-    GNUNET_GETOPT_option_uint ('p',
-                               "parallelism",
-                               "NUM_WORKERS",
-                               "number of worker threads to use",
-                               &num_workers),
     GNUNET_GETOPT_option_absolute_time ('t',
                                         "time",
                                         "TIMESTAMP",
@@ -1672,7 +1092,7 @@ main (int argc,
                                         &now_tmp),
     GNUNET_GETOPT_OPTION_END
   };
-  int ret;
+  enum GNUNET_GenericReturnValue ret;
 
   /* Restrict permissions for the key files that we create. */
   (void) umask (S_IWGRP | S_IROTH | S_IWOTH | S_IXOTH);
@@ -1689,8 +1109,8 @@ main (int argc,
                             &run,
                             NULL);
   if (GNUNET_NO == ret)
-    return 0;
+    return EXIT_SUCCESS;
   if (GNUNET_SYSERR == ret)
-    return 1;
+    return EXIT_INVALIDARGUMENT;
   return global_ret;
 }