From 6680f9b4ef37db66880d774d7dc9f97e7d639f13 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Wed, 16 Jun 2021 23:12:21 +0200
Subject: [PATCH] implement logic to replace 'true' forgettable salts with
 random salts, fix object deletion when forgetting

---
 src/include/taler_json_lib.h | 13 +++++
 src/json/json.c              | 98 ++++++++++++++++++++++++++++++++++--
 src/json/test_json.c         | 15 +++++-
 3 files changed, 121 insertions(+), 5 deletions(-)

diff --git a/src/include/taler_json_lib.h b/src/include/taler_json_lib.h
index bf8c22177..aefc28061 100644
--- a/src/include/taler_json_lib.h
+++ b/src/include/taler_json_lib.h
@@ -198,6 +198,19 @@ TALER_JSON_contract_hash (const json_t *json,
                           struct GNUNET_HashCode *hc);
 
 
+/**
+ * Take a given contract with "forgettable" fields marked
+ * but with 'True' instead of a real salt. Replaces all
+ * 'True' values with proper random salts.  Fails if any
+ * forgettable markers are neither 'True' nor valid salts.
+ *
+ * @param[in,out] json JSON to transform
+ * @return #GNUNET_OK on success
+ */
+int
+TALER_JSON_contract_seed_forgettable (json_t *json);
+
+
 /**
  * Mark part of a contract object as 'forgettable'.
  *
diff --git a/src/json/json.c b/src/json/json.c
index faae36d62..fe2ea8382 100644
--- a/src/json/json.c
+++ b/src/json/json.c
@@ -506,9 +506,8 @@ TALER_JSON_contract_part_forget (json_t *json,
   }
   /* finally, set 'forgotten' field to null */
   if (0 !=
-      json_object_set_new (json,
-                           field,
-                           json_null ()))
+      json_object_del (json,
+                       field))
   {
     GNUNET_break (0);
     return GNUNET_SYSERR;
@@ -517,6 +516,99 @@ TALER_JSON_contract_part_forget (json_t *json,
 }
 
 
+/**
+ * Look over all of the values of a '$forgettable' object.  Replace 'True'
+ * values with proper random salts.  Fails if any forgettable values are
+ * neither 'True' nor valid salts (strings).
+ *
+ * @param[in,out] f JSON to transform
+ * @return #GNUNET_OK on success
+ */
+static int
+seed_forgettable (json_t *f)
+{
+  const char *key;
+  json_t *val;
+
+  json_object_foreach (f,
+                       key,
+                       val)
+  {
+    if (json_is_string (val))
+      continue;
+    if (json_is_true (val))
+    {
+      struct GNUNET_ShortHashCode sh;
+
+      GNUNET_CRYPTO_random_block (GNUNET_CRYPTO_QUALITY_NONCE,
+                                  &sh,
+                                  sizeof (sh));
+      json_object_set_new (f,
+                           key,
+                           GNUNET_JSON_from_data_auto (&sh));
+      continue;
+    }
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Forgettable field `%s' has invalid value\n",
+                key);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Take a given contract with "forgettable" fields marked
+ * but with 'True' instead of a real salt. Replaces all
+ * 'True' values with proper random salts.  Fails if any
+ * forgettable markers are neither 'True' nor valid salts.
+ *
+ * @param[in,out] json JSON to transform
+ * @return #GNUNET_OK on success
+ */
+int
+TALER_JSON_contract_seed_forgettable (json_t *json)
+{
+  if (json_is_object (json))
+  {
+    const char *key;
+    json_t *val;
+
+    json_object_foreach (json,
+                         key,
+                         val)
+    {
+      if (0 == strcmp ("$forgettable",
+                       key))
+      {
+        if (GNUNET_OK !=
+            seed_forgettable (val))
+          return GNUNET_SYSERR;
+        continue;
+      }
+      if (GNUNET_OK !=
+          TALER_JSON_contract_seed_forgettable (val))
+        return GNUNET_SYSERR;
+    }
+  }
+  if (json_is_array (json))
+  {
+    size_t index;
+    json_t *val;
+
+    json_array_foreach (json,
+                        index,
+                        val)
+    {
+      if (GNUNET_OK !=
+          TALER_JSON_contract_seed_forgettable (val))
+        return GNUNET_SYSERR;
+    }
+  }
+  return GNUNET_OK;
+}
+
+
 /**
  * Parse a json path.
  *
diff --git a/src/json/test_json.c b/src/json/test_json.c
index b3c36837f..bedea76ac 100644
--- a/src/json/test_json.c
+++ b/src/json/test_json.c
@@ -96,6 +96,17 @@ test_contract (void)
   json_t *c3;
   json_t *c4;
 
+  c1 = json_pack ("{s:s, s:{s:s, s:{s:b}}}",
+                  "k1", "v1",
+                  "k2", "n1", "n2",
+                  /***/ "$forgettable", "n1", true);
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_JSON_contract_seed_forgettable (c1));
+  GNUNET_assert (GNUNET_OK ==
+                 TALER_JSON_contract_hash (c1,
+                                           &h1));
+  json_decref (c1);
+
   c1 = json_pack ("{s:s, s:{s:s, s:{s:s}}}",
                   "k1", "v1",
                   "k2", "n1", "n2",
@@ -147,6 +158,7 @@ test_contract (void)
   GNUNET_assert (GNUNET_OK ==
                  TALER_JSON_contract_part_forget (c1,
                                                   "k2"));
+  json_dumpf (c1, stderr, JSON_INDENT (2));
   GNUNET_assert (GNUNET_OK ==
                  TALER_JSON_contract_hash (c1,
                                            &h2));
@@ -159,7 +171,6 @@ test_contract (void)
     return 1;
   }
 
-
   c1 = json_pack ("{s:I, s:{s:s}, s:{s:b, s:{s:s}}, s:{s:s}}",
                   "k1", 1,
                   "$forgettable", "k1", "SALT",
@@ -178,7 +189,7 @@ test_contract (void)
                                              sizeof (h1));
     if (0 !=
         strcmp (s,
-                "48YVST0SZJXWNG3KAD14SSK3AD0T5V01W5AE6E76DYKMJSC5BQ19M0FZ7CZP5JY26FC4AFXTXRGEVSQ1NSKPQ1DQ4GS9C4SAECG5RZ8"))
+                "VDE8JPX0AEEE3EX1K8E11RYEWSZQKGGZCV6BWTE4ST1C8711P7H850Z7F2Q2HSSYETX87ERC2JNHWB7GTDWTDWMM716VKPSRBXD7SRR"))
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                   "Invalid reference hash: %s\n",