implementing #3987

7 files changed, 155 insertions, 68 deletions

diff --git a/src/exchange-lib/exchange_api_handle.c b/src/exchange-lib/exchange_api_handle.c
index aaca8bac1..26f5e7e15 100644
--- a/src/exchange-lib/exchange_api_handle.c
+++ b/src/exchange-lib/exchange_api_handle.c
@@ -360,16 +360,18 @@ parse_json_auditor (struct TALER_EXCHANGE_AuditorInformation *auditor,
   unsigned int len;
   unsigned int off;
   unsigned int i;
+  const char *auditor_url;
   struct TALER_ExchangeKeyValidityPS kv;
   struct GNUNET_JSON_Specification spec[] = {
     GNUNET_JSON_spec_fixed_auto ("auditor_pub",
-                         &auditor->auditor_pub),
+                                 &auditor->auditor_pub),
+    GNUNET_JSON_spec_string ("auditor_url",
+                             &auditor_url),
     GNUNET_JSON_spec_json ("denomination_keys",
-                   &keys),
+                           &keys),
     GNUNET_JSON_spec_end()
   };
 
-  auditor->auditor_url = NULL; /* #3987 */
   if (GNUNET_OK !=
       GNUNET_JSON_parse (auditor_obj,
                          spec,
@@ -378,8 +380,12 @@ parse_json_auditor (struct TALER_EXCHANGE_AuditorInformation *auditor,
     GNUNET_break_op (0);
     return GNUNET_SYSERR;
   }
+  auditor->auditor_url = GNUNET_strdup (auditor_url);
   kv.purpose.purpose = htonl (TALER_SIGNATURE_AUDITOR_EXCHANGE_KEYS);
   kv.purpose.size = htonl (sizeof (struct TALER_ExchangeKeyValidityPS));
+  GNUNET_CRYPTO_hash (auditor_url,
+                      strlen (auditor_url) + 1,
+                      &kv.auditor_url_hash);
   kv.master = key_data->master_pub;
   len = json_array_size (keys);
   auditor->denom_keys = GNUNET_new_array (len,
diff --git a/src/exchange-tools/taler-auditor-sign.c b/src/exchange-tools/taler-auditor-sign.c
index e4821f411..bde34b2a3 100644
--- a/src/exchange-tools/taler-auditor-sign.c
+++ b/src/exchange-tools/taler-auditor-sign.c
@@ -50,6 +50,11 @@ static char *exchange_request_file;
 static char *output_file;
 
 /**
+ * URL of the auditor (informative for the user).
+ */
+static char *auditor_url;
+
+/**
  * Master public key of the exchange.
  */
 static struct TALER_MasterPublicKeyP master_public_key;
@@ -134,6 +139,10 @@ main (int argc,
     {'m', "exchange-key", "KEY",
      "public key of the exchange (Crockford base32 encoded)", 1,
      &GNUNET_GETOPT_set_filename, &exchange_public_key},
+    {'u', "auditor-url", "URL",
+     "URL of the auditor (informative link for the user)", 1,
+     &GNUNET_GETOPT_set_string, &auditor_url},
+    TALER_GETOPT_OPTION_HELP ("Private key of the auditor to use for signing"),
     {'r', "exchange-request", "FILE",
      "set of keys the exchange requested the auditor to sign", 1,
      &GNUNET_GETOPT_set_string, &exchange_request_file},
@@ -168,6 +177,12 @@ main (int argc,
              "Auditor key file not given\n");
     return 1;
   }
+  if (NULL == auditor_url)
+  {
+    fprintf (stderr,
+             "Auditor URL not given\n");
+    return 1;
+  }
   eddsa_priv = GNUNET_CRYPTO_eddsa_key_create_from_file (auditor_key_file);
   if (NULL == eddsa_priv)
   {
@@ -240,6 +255,9 @@ main (int argc,
   dks_len = in_size / sizeof (struct TALER_DenominationKeyValidityPS);
   kv.purpose.purpose = htonl (TALER_SIGNATURE_AUDITOR_EXCHANGE_KEYS);
   kv.purpose.size = htonl (sizeof (struct TALER_ExchangeKeyValidityPS));
+  GNUNET_CRYPTO_hash (auditor_url,
+                      strlen (auditor_url) + 1,
+                      &kv.auditor_url_hash);
   kv.master = master_public_key;
   dks = GNUNET_new_array (dks_len,
                           struct TALER_DenominationKeyValidityPS);
@@ -281,8 +299,6 @@ main (int argc,
     GNUNET_CRYPTO_eddsa_sign (eddsa_priv,
                               &kv.purpose,
                               &sigs[i].eddsa_sig);
-
-
   }
 
   if (NULL == output_file)
@@ -298,11 +314,12 @@ main (int argc,
   /* write result to disk */
   if (GNUNET_OK !=
       TALER_EXCHANGEDB_auditor_write (output_file,
-                                  &apub,
-                                  sigs,
-                                  &master_public_key,
-                                  dks_len,
-                                  dks))
+                                      &apub,
+                                      auditor_url,
+                                      sigs,
+                                      &master_public_key,
+                                      dks_len,
+                                      dks))
   {
     fprintf (stderr,
              "Failed to write to file `%s': %s\n",
diff --git a/src/exchange/taler-exchange-httpd_keystate.c b/src/exchange/taler-exchange-httpd_keystate.c
index bf91b8183..dbb72fab2 100644
--- a/src/exchange/taler-exchange-httpd_keystate.c
+++ b/src/exchange/taler-exchange-httpd_keystate.c
@@ -419,6 +419,7 @@ reload_keys_sign_iter (void *cls,
  * Convert information from an auditor to a JSON object.
  *
  * @param apub the auditor's public key
+ * @param auditor_url URL of the auditor
  * @param dki_len length of @a dki and @a asigs arrays
  * @param asigs the auditor's signatures
  * @param dki array of denomination coin data signed by the auditor
@@ -426,6 +427,7 @@ reload_keys_sign_iter (void *cls,
  */
 static json_t *
 auditor_to_json (const struct TALER_AuditorPublicKeyP *apub,
+                 const char *auditor_url,
                  unsigned int dki_len,
                  const struct TALER_AuditorSignatureP **asigs,
                  const struct TALER_DenominationKeyValidityPS **dki)
@@ -442,10 +444,11 @@ auditor_to_json (const struct TALER_AuditorPublicKeyP *apub,
                                                             sizeof (struct GNUNET_HashCode)),
                                       "auditor_sig",
                                       GNUNET_JSON_from_data (asigs[i],
-                                                            sizeof (struct TALER_AuditorSignatureP))));
+                                                             sizeof (struct TALER_AuditorSignatureP))));
   return
-    json_pack ("{s:o, s:o}",
+    json_pack ("{s:o, s:s, s:o}",
                "denomination_keys", ja,
+               "auditor_url", auditor_url,
                "auditor_pub",
                GNUNET_JSON_from_data (apub,
                                      sizeof (struct TALER_AuditorPublicKeyP)));
@@ -460,6 +463,7 @@ auditor_to_json (const struct TALER_AuditorPublicKeyP *apub,
  *
  * @param cls closure with the `struct TMH_KS_StateHandle *`
  * @param apub the auditor's public key
+ * @param auditor_url URL of the auditor
  * @param mpub the exchange's public key (as expected by the auditor)
  * @param dki_len length of @a dki and @a asigs
  * @param asigs array with the auditor's signatures, of length @a dki_len
@@ -471,6 +475,7 @@ auditor_to_json (const struct TALER_AuditorPublicKeyP *apub,
 static int
 reload_auditor_iter (void *cls,
                      const struct TALER_AuditorPublicKeyP *apub,
+                     const char *auditor_url,
                      const struct TALER_MasterPublicKeyP *mpub,
                      unsigned int dki_len,
                      const struct TALER_AuditorSignatureP *asigs,
@@ -508,6 +513,7 @@ reload_auditor_iter (void *cls,
   /* add auditor information to our /keys response */
   json_array_append_new (ctx->auditors_array,
                          auditor_to_json (apub,
+                                          auditor_url,
                                           keep,
                                           kept_asigs,
                                           kept_dkis));
diff --git a/src/exchangedb/exchangedb_keyio.c b/src/exchangedb/exchangedb_keyio.c
index 6b8ca24e3..e560e8d6b 100644
--- a/src/exchangedb/exchangedb_keyio.c
+++ b/src/exchangedb/exchangedb_keyio.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014, 2015 GNUnet e.V.
+  Copyright (C) 2014, 2015, 2016 Inria & GNUnet e.V.
 
   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
@@ -93,8 +93,8 @@ signkeys_iterate_dir_iter (void *cls,
  */
 int
 TALER_EXCHANGEDB_signing_keys_iterate (const char *exchange_base_dir,
-                                   TALER_EXCHANGEDB_SigningKeyIterator it,
-                                   void *it_cls)
+                                       TALER_EXCHANGEDB_SigningKeyIterator it,
+                                       void *it_cls)
 {
   char *signkey_dir;
   struct SignkeysIterateContext skc;
@@ -123,7 +123,7 @@ TALER_EXCHANGEDB_signing_keys_iterate (const char *exchange_base_dir,
  */
 int
 TALER_EXCHANGEDB_denomination_key_read (const char *filename,
-                                    struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki)
+                                        struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki)
 {
   uint64_t size;
   size_t offset;
@@ -186,7 +186,7 @@ TALER_EXCHANGEDB_denomination_key_read (const char *filename,
  */
 int
 TALER_EXCHANGEDB_denomination_key_write (const char *filename,
-                                     const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki)
+                                         const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki)
 {
   char *priv_enc;
   size_t priv_enc_size;
@@ -331,8 +331,8 @@ denomkeys_iterate_topdir_iter (void *cls,
  */
 int
 TALER_EXCHANGEDB_denomination_keys_iterate (const char *exchange_base_dir,
-                                        TALER_EXCHANGEDB_DenominationKeyIterator it,
-                                        void *it_cls)
+                                            TALER_EXCHANGEDB_DenominationKeyIterator it,
+                                            void *it_cls)
 {
   char *dir;
   struct DenomkeysIterateContext dic;
@@ -388,6 +388,11 @@ struct AuditorFileHeaderP
    */
   struct TALER_MasterPublicKeyP mpub;
 
+  /**
+   * Number of signatures and DKI entries in this file.
+   */
+  uint32_t dki_len;
+
 };
 GNUNET_NETWORK_STRUCT_END
 
@@ -412,7 +417,9 @@ auditor_iter (void *cls,
   struct AuditorFileHeaderP *af;
   const struct TALER_AuditorSignatureP *sigs;
   const struct TALER_DenominationKeyValidityPS *dki;
-  unsigned int len;
+  const char *auditor_url;
+  unsigned int dki_len;
+  size_t url_len;
   int ret;
 
   if (GNUNET_OK != GNUNET_DISK_file_size (filename,
@@ -425,10 +432,7 @@ auditor_iter (void *cls,
                 filename);
     return GNUNET_SYSERR;
   }
-  if ( (size < sizeof (struct AuditorFileHeaderP)) ||
-       (0 != (len = ((size - sizeof (struct AuditorFileHeaderP)) %
-                     (sizeof (struct TALER_DenominationKeyValidityPS) +
-                      sizeof (struct TALER_AuditorSignatureP))))) )
+  if (size < sizeof (struct AuditorFileHeaderP))
   {
     GNUNET_break (0);
     return GNUNET_SYSERR;
@@ -445,12 +449,49 @@ auditor_iter (void *cls,
     GNUNET_free (af);
     return GNUNET_SYSERR;
   }
+  dki_len = ntohl (af->dki_len);
+  if (0 == dki_len)
+  {
+    GNUNET_break_op (0);
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "No signed keys in %s\n",
+                filename);
+    GNUNET_free (af);
+    return GNUNET_SYSERR;
+  }
+  if ( (size - sizeof (struct AuditorFileHeaderP)) / dki_len <
+       (sizeof (struct TALER_DenominationKeyValidityPS) +
+        sizeof (struct TALER_AuditorSignatureP)) )
+  {
+    GNUNET_break_op (0);
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Malformed key file %s\n",
+                filename);
+    GNUNET_free (af);
+    return GNUNET_SYSERR;
+  }
+  url_len = size
+    - sizeof (struct AuditorFileHeaderP)
+    - dki_len * (sizeof (struct TALER_DenominationKeyValidityPS) +
+                 sizeof (struct TALER_AuditorSignatureP));
   sigs = (const struct TALER_AuditorSignatureP *) &af[1];
-  dki = (const struct TALER_DenominationKeyValidityPS *) &sigs[len];
+  dki = (const struct TALER_DenominationKeyValidityPS *) &sigs[dki_len];
+  auditor_url = (const char *) &dki[dki_len];
+  if ( (0 == url_len) ||
+       ('\0' != auditor_url[url_len - 1]) )
+  {
+    GNUNET_break_op (0);
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Malformed key file %s\n",
+                filename);
+    GNUNET_free (af);
+    return GNUNET_SYSERR;
+  }
   ret = aic->it (aic->it_cls,
                  &af->apub,
+                 auditor_url,
                  &af->mpub,
-                 len,
+                 dki_len,
                  sigs,
                  dki);
   GNUNET_free (af);
@@ -473,8 +514,8 @@ auditor_iter (void *cls,
  */
 int
 TALER_EXCHANGEDB_auditor_iterate (const char *exchange_base_dir,
-                              TALER_EXCHANGEDB_AuditorIterator it,
-                              void *it_cls)
+                                  TALER_EXCHANGEDB_AuditorIterator it,
+                                  void *it_cls)
 {
   char *dir;
   struct AuditorIterateContext aic;
@@ -498,6 +539,7 @@ TALER_EXCHANGEDB_auditor_iterate (const char *exchange_base_dir,
  *
  * @param filename the file where to write the auditor information to
  * @param apub the auditor's public key
+ * @param auditor_url the URL of the auditor
  * @param asigs the auditor's signatures, array of length @a dki_len
  * @param mpub the exchange's public key (as expected by the auditor)
  * @param dki_len length of @a dki
@@ -506,11 +548,12 @@ TALER_EXCHANGEDB_auditor_iterate (const char *exchange_base_dir,
  */
 int
 TALER_EXCHANGEDB_auditor_write (const char *filename,
-                            const struct TALER_AuditorPublicKeyP *apub,
-                            const struct TALER_AuditorSignatureP *asigs,
-                            const struct TALER_MasterPublicKeyP *mpub,
-                            unsigned int dki_len,
-                            const struct TALER_DenominationKeyValidityPS *dki)
+                                const struct TALER_AuditorPublicKeyP *apub,
+                                const char *auditor_url,
+                                const struct TALER_AuditorSignatureP *asigs,
+                                const struct TALER_MasterPublicKeyP *mpub,
+                                unsigned int dki_len,
+                                const struct TALER_DenominationKeyValidityPS *dki)
 {
   struct AuditorFileHeaderP af;
   struct GNUNET_DISK_FileHandle *fh;
@@ -521,6 +564,7 @@ TALER_EXCHANGEDB_auditor_write (const char *filename,
 
   af.apub = *apub;
   af.mpub = *mpub;
+  af.dki_len = htonl ((uint32_t) dki_len);
   ret = GNUNET_SYSERR;
   if (NULL == (fh = GNUNET_DISK_file_open
                (filename,
@@ -546,6 +590,12 @@ TALER_EXCHANGEDB_auditor_write (const char *filename,
                               dki,
                               wsize))
     ret = GNUNET_OK;
+  wsize = strlen (auditor_url) + 1;
+  if (wsize ==
+      GNUNET_DISK_file_write (fh,
+                              auditor_url,
+                              wsize))
+    ret = GNUNET_OK;
  cleanup:
   eno = errno;
   if (NULL != fh)
diff --git a/src/include/taler_exchange_service.h b/src/include/taler_exchange_service.h
index c3ecba968..cb1bd12aa 100644
--- a/src/include/taler_exchange_service.h
+++ b/src/include/taler_exchange_service.h
@@ -208,19 +208,19 @@ struct TALER_EXCHANGE_DenomPublicKey
 struct TALER_EXCHANGE_AuditorInformation
 {
   /**
-   * Public key of the auditing institution.
+   * Public key of the auditing institution.  Wallets and merchants
+   * are expected to be configured with a set of public keys of
+   * auditors that they deem acceptable.  These public keys are
+   * the roots of the Taler PKI.
    */
   struct TALER_AuditorPublicKeyP auditor_pub;
 
   /**
-   * URL of the auditing institution.  The application must check that
-   * this is an acceptable auditor for its purpose and also verify
-   * that the @a auditor_pub matches the auditor's public key given at
-   * that website.  We expect that in practice software is going to
-   * often ship with an initial list of accepted auditors, just like
-   * browsers ship with a CA root store.
-   *
-   * This field may be NULL. (#3987).
+   * URL of the auditing institution.  Signed by the auditor's public
+   * key, this URL is a place where applications can direct users for
+   * additional information about the auditor.  In the future, there
+   * should also be an auditor API for automated submission about
+   * claims of misbehaving exchange providers.
    */
   const char *auditor_url;
 
@@ -230,7 +230,7 @@ struct TALER_EXCHANGE_AuditorInformation
   unsigned int num_denom_keys;
 
   /**
-   * Array of length @a denom_keys with the denomination
+   * Array of length @a num_denom_keys with the denomination
    * keys audited by this auditor.  Note that the array
    * elements point to the same locations as the entries
    * in the key's main `denom_keys` array.
diff --git a/src/include/taler_exchangedb_lib.h b/src/include/taler_exchangedb_lib.h
index 347ad0650..e13df2d46 100644
--- a/src/include/taler_exchangedb_lib.h
+++ b/src/include/taler_exchangedb_lib.h
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014, 2015 GNUnet e.V.
+  Copyright (C) 2014, 2015, 2016 Inria & GNUnet e.V.
 
   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
@@ -125,8 +125,8 @@ struct TALER_EXCHANGEDB_DenominationKeyIssueInformation
  */
 typedef int
 (*TALER_EXCHANGEDB_SigningKeyIterator)(void *cls,
-                                   const char *filename,
-                                   const struct TALER_EXCHANGEDB_PrivateSigningKeyInformationP *ski);
+                                       const char *filename,
+                                       const struct TALER_EXCHANGEDB_PrivateSigningKeyInformationP *ski);
 
 
 /**
@@ -143,8 +143,8 @@ typedef int
  */
 int
 TALER_EXCHANGEDB_signing_keys_iterate (const char *exchange_base_dir,
-                                   TALER_EXCHANGEDB_SigningKeyIterator it,
-                                   void *it_cls);
+                                       TALER_EXCHANGEDB_SigningKeyIterator it,
+                                       void *it_cls);
 
 
 
@@ -160,8 +160,8 @@ TALER_EXCHANGEDB_signing_keys_iterate (const char *exchange_base_dir,
  */
 typedef int
 (*TALER_EXCHANGEDB_DenominationKeyIterator)(void *cls,
-                                        const char *alias,
-                                        const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
+                                            const char *alias,
+                                            const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
 
 
 /**
@@ -179,8 +179,8 @@ typedef int
  */
 int
 TALER_EXCHANGEDB_denomination_keys_iterate (const char *exchange_base_dir,
-                                        TALER_EXCHANGEDB_DenominationKeyIterator it,
-                                        void *it_cls);
+                                            TALER_EXCHANGEDB_DenominationKeyIterator it,
+                                            void *it_cls);
 
 
 /**
@@ -192,7 +192,7 @@ TALER_EXCHANGEDB_denomination_keys_iterate (const char *exchange_base_dir,
  */
 int
 TALER_EXCHANGEDB_denomination_key_write (const char *filename,
-                                     const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
+                                         const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
 
 
 /**
@@ -204,7 +204,7 @@ TALER_EXCHANGEDB_denomination_key_write (const char *filename,
  */
 int
 TALER_EXCHANGEDB_denomination_key_read (const char *filename,
-                                    struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
+                                        struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
 
 
 /**
@@ -212,6 +212,7 @@ TALER_EXCHANGEDB_denomination_key_read (const char *filename,
  *
  * @param cls closure
  * @param apub the auditor's public key
+ * @param auditor_url URL of the auditor
  * @param mpub the exchange's public key (as expected by the auditor)
  * @param dki_len length of @a asig and @a dki arrays
  * @param asigs array of the auditor's signatures over the @a dks, of length @a dki_len
@@ -222,11 +223,12 @@ TALER_EXCHANGEDB_denomination_key_read (const char *filename,
  */
 typedef int
 (*TALER_EXCHANGEDB_AuditorIterator)(void *cls,
-                                const struct TALER_AuditorPublicKeyP *apub,
-                                const struct TALER_MasterPublicKeyP *mpub,
-                                unsigned int dki_len,
-                                const struct TALER_AuditorSignatureP *asigs,
-                                const struct TALER_DenominationKeyValidityPS *dki);
+                                    const struct TALER_AuditorPublicKeyP *apub,
+                                    const char *auditor_url,
+                                    const struct TALER_MasterPublicKeyP *mpub,
+                                    unsigned int dki_len,
+                                    const struct TALER_AuditorSignatureP *asigs,
+                                    const struct TALER_DenominationKeyValidityPS *dki);
 
 
 /**
@@ -244,8 +246,8 @@ typedef int
  */
 int
 TALER_EXCHANGEDB_auditor_iterate (const char *exchange_base_dir,
-                              TALER_EXCHANGEDB_AuditorIterator it,
-                              void *it_cls);
+                                  TALER_EXCHANGEDB_AuditorIterator it,
+                                  void *it_cls);
 
 
 /**
@@ -253,6 +255,7 @@ TALER_EXCHANGEDB_auditor_iterate (const char *exchange_base_dir,
  *
  * @param filename the file where to write the auditor information to
  * @param apub the auditor's public key
+ * @param auditor_url the URL of the auditor
  * @param asigs the auditor's signatures, array of length @a dki_len
  * @param mpub the exchange's public key (as expected by the auditor)
  * @param dki_len length of @a dki and @a asigs arrays
@@ -261,11 +264,12 @@ TALER_EXCHANGEDB_auditor_iterate (const char *exchange_base_dir,
  */
 int
 TALER_EXCHANGEDB_auditor_write (const char *filename,
-                            const struct TALER_AuditorPublicKeyP *apub,
-                            const struct TALER_AuditorSignatureP *asigs,
-                            const struct TALER_MasterPublicKeyP *mpub,
-                            unsigned int dki_len,
-                            const struct TALER_DenominationKeyValidityPS *dki);
+                                const struct TALER_AuditorPublicKeyP *apub,
+                                const char *auditor_url,
+                                const struct TALER_AuditorSignatureP *asigs,
+                                const struct TALER_MasterPublicKeyP *mpub,
+                                unsigned int dki_len,
+                                const struct TALER_DenominationKeyValidityPS *dki);
 
 
 /**
@@ -287,5 +291,4 @@ void
 TALER_EXCHANGEDB_plugin_unload (struct TALER_EXCHANGEDB_Plugin *plugin);
 
 
-
 #endif
diff --git a/src/include/taler_signatures.h b/src/include/taler_signatures.h
index 729bed262..d958f16ba 100644
--- a/src/include/taler_signatures.h
+++ b/src/include/taler_signatures.h
@@ -656,8 +656,13 @@ struct TALER_ExchangeKeyValidityPS
   struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
 
   /**
+   * Hash of the auditor's URL.
+   */
+  struct GNUNET_HashCode auditor_url_hash;
+
+  /**
    * The long-term offline master key of the exchange, affirmed by the
-   * auditor.
+   * auditor.  Hashed string, including 0-terminator.
    */
   struct TALER_MasterPublicKeyP master;