implement denomination key revocation logic in exchangedb and taler-exchange-keyup (part of #3887)

doc/taler-exchange-keyup.1

@@ -1,4 +1,4 @@
-.TH TALER\-EXCHANGE\-KEYUP 1 "Apr 22, 2015" "GNU Taler"
+.TH TALER\-EXCHANGE\-KEYUP 1 "Apr 7, 2017" "GNU Taler"
 
 .SH NAME
 taler\-exchange\-keyup \- Setup Taler exchange denomination and signing keys.
@@ -25,6 +25,9 @@ Location of the private EdDSA offline master key of the exchange.
 .IP "\-o FILE,  \-\-ouptut=FILE"
 Where to write a denomination key signing request file to be given to the auditor.
 .B
+.IP "\-r DKH,  \-\-revoke=DKH"
+Revoke the denomination key where the denomination public key's hash is DKH.
+.B
 .IP "\-t TIMESTAMP,  \-\-time=TIMESTAMP"
 Operate as if the current time was TIMESTAMP.
 .B

src/exchange-tools/taler-exchange-keycheck.c

@@ -122,6 +122,7 @@ exchange_signkeys_check ()
  * @param cls closure (NULL)
  * @param dki the denomination key
  * @param alias coin alias
+ * @param was_revoked #GNUNET_YES if the @a dki was revoked and wallets should trigger /payback
  * @return #GNUNET_OK to continue to iterate,
  *  #GNUNET_NO to stop iteration with no error,
  *  #GNUNET_SYSERR to abort iteration with error!
@@ -129,7 +130,8 @@ exchange_signkeys_check ()
 static int
 denomkeys_iter (void *cls,
                 const char *alias,
-                const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki)
+                const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki,
+                int was_revoked)
 {
   struct GNUNET_HashCode hc;
 
@@ -190,7 +192,23 @@ denomkeys_iter (void *cls,
 static int
 exchange_denomkeys_check ()
 {
+  struct TALER_MasterPublicKeyP master_public_key_from_cfg;
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_data (kcfg,
+                                     "exchange",
+                                     "master_public_key",
+                                     &master_public_key_from_cfg,
+                                     sizeof (struct GNUNET_CRYPTO_EddsaPublicKey)))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "exchange",
+                               "master_public_key");
+    global_ret = 1;
+    return GNUNET_NO;
+  }
   if (0 > TALER_EXCHANGEDB_denomination_keys_iterate (exchange_directory,
+                                                      &master_public_key_from_cfg,
                                                       &denomkeys_iter,
                                                       NULL))
     return GNUNET_NO;

src/exchange-tools/taler-exchange-keyup.c

@@ -220,6 +220,11 @@ static struct GNUNET_TIME_Absolute lookahead_sign_stamp;
  */
 static struct GNUNET_TIME_Relative max_duration_spend;
 
+/**
+ * Revoke denomination key identified by this hash (if non-zero).
+ */
+static struct GNUNET_HashCode revoke_dkh;
+
 /**
  * Return value from main().
  */
@@ -1018,6 +1023,106 @@ create_wire_fees ()
 }
 
 
+/**
+ * Closure for functions processing a request to revoke a denomination
+ * public key and request the wallets to initiate /payback.
+ */
+struct RevokeClosure
+{
+  /**
+   * Hash of the denomination public key to revoke.
+   */
+  const struct GNUNET_HashCode *hc;
+
+  /**
+   * Base directory for keys.
+   */
+  char *basedir;
+
+  /**
+   * Set to #GNUNET_OK if we found a matching key,
+   * Set to #GNUNET_SYSERR on error.
+   */
+  int ok;
+};
+
+
+
+/**
+ * Revoke denomination keys matching the given hash.
+ *
+ * @param cls a `struct RevokeClosure` with information about what to revoke
+ * @param dki the denomination key
+ * @param alias coin alias
+ * @param was_revoked #GNUNET_YES if the @a dki was revoked and wallets should trigger /payback
+ * @return #GNUNET_OK to continue to iterate,
+ *  #GNUNET_NO to stop iteration with no error,
+ *  #GNUNET_SYSERR to abort iteration with error!
+ */
+static int
+exchange_keys_revoke_by_dki (void *cls,
+                             const char *alias,
+                             const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki,
+                             int was_revoked)
+{
+  struct RevokeClosure *rc = cls;
+
+  if (GNUNET_YES == was_revoked)
+    return GNUNET_OK; /* refuse to do it twice */
+  if (0 != memcmp (rc->hc,
+                   &dki->issue.properties.denom_hash,
+                   sizeof (struct GNUNET_HashCode)))
+    return GNUNET_OK;
+  rc->ok = GNUNET_OK;
+  if (GNUNET_OK !=
+      TALER_EXCHANGEDB_denomination_key_revoke (rc->basedir,
+                                                alias,
+                                                dki,
+                                                &master_priv))
+  {
+    rc->ok = GNUNET_SYSERR;
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_NO;
+}
+
+
+/**
+ * Revoke the denomination key matching @a hc and request /payback to be
+ * initiated.
+ *
+ * @param hc denomination key hash to revoke
+ * @return #GNUNET_OK on success,
+ *         #GNUNET_NO if @a hc was not found
+ *         #GNUNET_SYSERR on error
+ */
+static int
+revoke_denomination (const struct GNUNET_HashCode *hc)
+{
+  struct RevokeClosure rc;
+
+  rc.hc = hc;
+  rc.ok = GNUNET_NO;
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (kcfg,
+                                               "exchange",
+                                               "KEYDIR",
+                                               &rc.basedir))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "exchange",
+                               "KEYDIR");
+    return GNUNET_SYSERR;
+  }
+  TALER_EXCHANGEDB_denomination_keys_iterate (rc.basedir,
+                                              &master_public_key,
+                                              &exchange_keys_revoke_by_dki,
+                                              &rc);
+  GNUNET_free (rc.basedir);
+  return rc.ok;
+}
+
+
 /**
  * Main function that will be run.
  *
@@ -1032,6 +1137,7 @@ run (void *cls,
      const char *cfgfile,
      const struct GNUNET_CONFIGURATION_Handle *cfg)
 {
+  static struct GNUNET_HashCode zero;
   struct GNUNET_TIME_Relative lookahead_sign;
   struct GNUNET_CRYPTO_EddsaPrivateKey *eddsa_priv;
 
@@ -1119,7 +1225,7 @@ run (void *cls,
 
   /* check if key from file matches the one from the configuration */
   {
-    struct GNUNET_CRYPTO_EddsaPublicKey master_public_key_from_cfg;
+    struct TALER_MasterPublicKeyP master_public_key_from_cfg;
 
     if (GNUNET_OK !=
         GNUNET_CONFIGURATION_get_data (kcfg,
@@ -1137,7 +1243,7 @@ run (void *cls,
     if (0 !=
         memcmp (&master_public_key,
                 &master_public_key_from_cfg,
-                sizeof (struct GNUNET_CRYPTO_EddsaPublicKey)))
+                sizeof (struct TALER_MasterPublicKeyP)))
     {
       GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
                                  "exchange",
@@ -1190,6 +1296,15 @@ run (void *cls,
     global_ret = 1;
     return;
   }
+  if ( (0 != memcmp (&zero,
+                     &revoke_dkh,
+                     sizeof (zero))) &&
+       (GNUNET_OK !=
+        revoke_denomination (&revoke_dkh)) )
+  {
+    global_ret = 1;
+    return;
+  }
 }
 
 
@@ -1226,6 +1341,11 @@ main (int argc,
                                    "FILENAME",
                                    "auditor denomination key signing request file to create",
                                    &auditorrequestfile),
+    GNUNET_GETOPT_option_base32_auto ('r',
+                                      "revoke",
+                                      "DKH",
+                                      "revoke denomination key hash (DKH) and request wallets to initiate /payback",
+                                      &revoke_dkh),
     GNUNET_GETOPT_option_absolute_time ('t',
                                         "time",
                                         "TIMESTAMP",

src/exchange/taler-exchange-httpd_keystate.c

@@ -210,6 +210,7 @@ TALER_EXCHANGE_conf_duration_provide ()
  * @param cls closure
  * @param dki the denomination key issue
  * @param alias coin alias
+ * @param was_revoked #GNUNET_YES if @a dki has been revoked
  * @return #GNUNET_OK to continue to iterate,
  *  #GNUNET_NO to stop iteration with no error,
  *  #GNUNET_SYSERR to abort iteration with error!
@@ -217,7 +218,8 @@ TALER_EXCHANGE_conf_duration_provide ()
 static int
 reload_keys_denom_iter (void *cls,
                         const char *alias,
-                        const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki)
+                        const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki,
+                        int was_revoked)
 {
   struct TEH_KS_StateHandle *ctx = cls;
   struct GNUNET_TIME_Absolute now;
@@ -674,6 +676,7 @@ TEH_KS_acquire_ (const char *location)
                 "Loading keys from `%s'\n",
                 TEH_exchange_directory);
     if (-1 == TALER_EXCHANGEDB_denomination_keys_iterate (TEH_exchange_directory,
+                                                          &TEH_master_public_key,
                                                           &reload_keys_denom_iter,
                                                           key_state))
     {

src/exchangedb/exchangedb_denomkeys.c

@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014, 2015, 2016 Inria & GNUnet e.V.
+  Copyright (C) 2014-2017 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
@@ -25,6 +25,68 @@
 #include "taler_exchangedb_lib.h"
 
 
+/**
+ * Mark the given denomination key as revoked and request the wallets
+ * to initiate /payback.
+ *
+ * @param exchange_base_dir base directory for the exchange,
+ *                      the signing keys must be in the #TALER_EXCHANGEDB_DIR_DENOMINATION_KEYS
+ *                      subdirectory
+ * @param alias coin alias
+ * @param dki the denomination key to revoke
+ * @param mpriv master private key to sign
+ * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure.
+ */
+int
+TALER_EXCHANGEDB_denomination_key_revoke (const char *exchange_base_dir,
+                                          const char *alias,
+                                          const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki,
+                                          const struct TALER_MasterPrivateKeyP *mpriv)
+{
+  struct GNUNET_TIME_Absolute start;
+  struct TALER_MasterDenominationKeyRevocation rm;
+  struct TALER_MasterSignatureP msig;
+  char *fn;
+  struct GNUNET_DISK_FileHandle *fh;
+  ssize_t wrote;
+  int ret;
+
+  ret = GNUNET_SYSERR;
+  start = GNUNET_TIME_absolute_ntoh (dki->issue.properties.start);
+  GNUNET_asprintf (&fn,
+                   "%s" DIR_SEPARATOR_STR "%s" DIR_SEPARATOR_STR "%llu.rev",
+                   exchange_base_dir,
+                   alias,
+                   (unsigned long long) start.abs_value_us);
+
+  rm.purpose.purpose = htonl (TALER_SIGNATURE_MASTER_DENOMINATION_KEY_REVOKED);
+  rm.purpose.size = htonl (sizeof (rm));
+  rm.h_denom_pub = dki->issue.properties.denom_hash;
+  GNUNET_assert (GNUNET_OK ==
+                 GNUNET_CRYPTO_eddsa_sign (&mpriv->eddsa_priv,
+                                           &rm.purpose,
+                                           &msig.eddsa_signature));
+  if (NULL == (fh = GNUNET_DISK_file_open
+               (fn,
+                GNUNET_DISK_OPEN_WRITE | GNUNET_DISK_OPEN_CREATE | GNUNET_DISK_OPEN_TRUNCATE,
+                GNUNET_DISK_PERM_USER_READ | GNUNET_DISK_PERM_USER_WRITE)))
+    goto cleanup;
+  if (GNUNET_SYSERR ==
+      (wrote = GNUNET_DISK_file_write (fh,
+                                       &msig,
+                                       sizeof (msig))))
+    goto cleanup;
+  if (wrote != sizeof (msig))
+    goto cleanup;
+  ret = GNUNET_OK;
+cleanup:
+  if (NULL != fh)
+    (void) GNUNET_DISK_file_close (fh);
+  GNUNET_free (fn);
+  return ret;
+}
+
+
 /**
  * Import a denomination key from the given file.
  *
@@ -157,6 +219,11 @@ struct DenomkeysIterateContext
    */
   const char *alias;
 
+  /**
+   * Master public key to use to validate revocations.
+   */
+  const struct TALER_MasterPublicKeyP *master_pub;
+
   /**
    * Function to call on each denomination key.
    */
@@ -187,6 +254,15 @@ denomkeys_iterate_keydir_iter (void *cls,
   struct DenomkeysIterateContext *dic = cls;
   struct TALER_EXCHANGEDB_DenominationKeyIssueInformation issue;
   int ret;
+  char *rev;
+  struct TALER_MasterSignatureP msig;
+  struct TALER_MasterDenominationKeyRevocation rm;
+  int revoked;
+
+  if ( (strlen(filename) > strlen (".rev")) &&
+       (0 == strcmp (&filename[strlen(filename) - strlen (".rev")],
+                     ".rev")) )
+    return GNUNET_OK; /* ignore revocation files _here_; we'll try for them just below */
 
   memset (&issue, 0, sizeof (issue));
   if (GNUNET_OK !=
@@ -198,9 +274,53 @@ denomkeys_iterate_keydir_iter (void *cls,
                 filename);
     return GNUNET_OK;
   }
+  /* check for revocation file */
+  GNUNET_asprintf (&rev,
+                   "%s.rev",
+                   filename);
+  revoked = GNUNET_NO;
+  if (GNUNET_YES == GNUNET_DISK_file_test (rev))
+  {
+    /* Check if revocation is valid... */
+    if (sizeof (msig) !=
+        GNUNET_DISK_fn_read (rev,
+                             &msig,
+                             sizeof (msig)))
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  _("Invalid revocation file `%s' found and ignored (bad size)\n"),
+                  rev);
+    }
+    else
+    {
+      rm.purpose.purpose = htonl (TALER_SIGNATURE_MASTER_DENOMINATION_KEY_REVOKED);
+      rm.purpose.size = htonl (sizeof (rm));
+      rm.h_denom_pub = issue.issue.properties.denom_hash;
+      if (GNUNET_OK !=
+          GNUNET_CRYPTO_eddsa_verify (TALER_SIGNATURE_MASTER_DENOMINATION_KEY_REVOKED,
+                                      &rm.purpose,
+                                      &msig.eddsa_signature,
+                                      &dic->master_pub->eddsa_pub))
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                    _("Invalid revocation file `%s' found and ignored (bad signature)\n"),
+                    rev);
+      }
+      else
+      {
+        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                    "Denomination key `%s' was revoked!\n",
+                   filename);
+        revoked = GNUNET_YES;
+      }
+    }
+
+  }
+  GNUNET_free (rev);
   ret = dic->it (dic->it_cls,
                  dic->alias,
-                 &issue);
+                 &issue,
+                 revoked);
   GNUNET_CRYPTO_rsa_private_key_free (issue.denom_priv.rsa_private_key);
   GNUNET_CRYPTO_rsa_public_key_free (issue.denom_pub.rsa_public_key);
   return ret;
@@ -238,6 +358,7 @@ denomkeys_iterate_topdir_iter (void *cls,
  * @param exchange_base_dir base directory for the exchange,
  *                      the signing keys must be in the #TALER_EXCHANGEDB_DIR_DENOMINATION_KEYS
  *                      subdirectory
+ * @param master_pub master public key (used to check revocations)
  * @param it function to call on each denomination key found
  * @param it_cls closure for @a it
  * @return -1 on error, 0 if no files were found, otherwise
@@ -247,6 +368,7 @@ denomkeys_iterate_topdir_iter (void *cls,
  */
 int
 TALER_EXCHANGEDB_denomination_keys_iterate (const char *exchange_base_dir,
+                                            const struct TALER_MasterPublicKeyP *master_pub,
                                             TALER_EXCHANGEDB_DenominationKeyIterator it,
                                             void *it_cls)
 {
@@ -257,6 +379,7 @@ TALER_EXCHANGEDB_denomination_keys_iterate (const char *exchange_base_dir,
   GNUNET_asprintf (&dir,
                    "%s" DIR_SEPARATOR_STR TALER_EXCHANGEDB_DIR_DENOMINATION_KEYS,
                    exchange_base_dir);
+  dic.master_pub = master_pub;
   dic.it = it;
   dic.it_cls = it_cls;
   ret = GNUNET_DISK_directory_scan (dir,

src/include/taler_exchangedb_lib.h

@@ -160,8 +160,9 @@ TALER_EXCHANGEDB_signing_key_write (const char *exchange_base_dir,
  * @brief Iterator over denomination keys.
  *
  * @param cls closure
- * @param dki the denomination key
  * @param alias coin alias
+ * @param dki the denomination key
+ * @param was_revoked #GNUNET_YES if the @a dki was revoked and wallets should trigger /payback
  * @return #GNUNET_OK to continue to iterate,
  *  #GNUNET_NO to stop iteration with no error,
  *  #GNUNET_SYSERR to abort iteration with error!
@@ -169,7 +170,8 @@ TALER_EXCHANGEDB_signing_key_write (const char *exchange_base_dir,
 typedef int
 (*TALER_EXCHANGEDB_DenominationKeyIterator)(void *cls,
                                             const char *alias,
-                                            const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki);
+                                            const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki,
+                                            int was_revoked);
 
 
 /**
@@ -178,6 +180,7 @@ typedef int
  * @param exchange_base_dir base directory for the exchange,
  *                      the signing keys must be in the #TALER_EXCHANGEDB_DIR_DENOMINATION_KEYS
  *                      subdirectory
+ * @param master_pub master public key (used to check revocations)
  * @param it function to call on each denomination key found
  * @param it_cls closure for @a it
  * @return -1 on error, 0 if no files were found, otherwise
@@ -187,10 +190,30 @@ typedef int
  */
 int
 TALER_EXCHANGEDB_denomination_keys_iterate (const char *exchange_base_dir,
+                                            const struct TALER_MasterPublicKeyP *master_pub,
                                             TALER_EXCHANGEDB_DenominationKeyIterator it,
                                             void *it_cls);
 
 
+/**
+ * Mark the given denomination key as revoked and request the wallets
+ * to initiate /payback.
+ *
+ * @param exchange_base_dir base directory for the exchange,
+ *                      the signing keys must be in the #TALER_EXCHANGEDB_DIR_DENOMINATION_KEYS
+ *                      subdirectory
+ * @param alias coin alias
+ * @param dki the denomination key to revoke
+ * @param mpriv master private key to sign
+ * @return #GNUNET_OK upon success; #GNUNET_SYSERR upon failure.
+ */
+int
+TALER_EXCHANGEDB_denomination_key_revoke (const char *exchange_base_dir,
+                                          const char *alias,
+                                          const struct TALER_EXCHANGEDB_DenominationKeyIssueInformation *dki,
+                                          const struct TALER_MasterPrivateKeyP *mpriv);
+
+
 /**
  * Exports a denomination key to the given file.
  *

src/include/taler_signatures.h

@@ -83,6 +83,10 @@
  */
 #define TALER_SIGNATURE_MASTER_WIRE_FEES 1028
 
+/**
+ * The given revocation key was revoked and must no longer be used.
+ */
+#define TALER_SIGNATURE_MASTER_DENOMINATION_KEY_REVOKED 1029
 
 /*********************************************/
 /* Exchange online signatures (with signing key) */
@@ -937,6 +941,24 @@ struct TALER_MasterWireFeePS
 };
 
 
+/**
+ * @brief Message confirming that a denomination key was revoked.
+ */
+struct TALER_MasterDenominationKeyRevocation
+{
+  /**
+   * Purpose is #TALER_SIGNATURE_MASTER_DENOMINATION_KEY_REVOKED.
+   */
+  struct GNUNET_CRYPTO_EccSignaturePurpose purpose;
+
+  /**
+   * Hash of the denomination key.
+   */
+  struct GNUNET_HashCode h_denom_pub;
+
+};
+
+
 /**
  * @brief Format used to generate the signature on a request to obtain
  * the wire transfer identifier associated with a deposit.