Replace JSON-GLib by custom JSON dumper library

The (optional) JSON-GLib library adds dependencies on GObject, GIO. For
statically linked oss-fuzz builds it also adds libffi and more. To avoid
these dependencies, replace JSON-GLib by some custom code. This allows
`tshark -G elastic-mapping` to be enabled by default without extra deps.

API design goals of the new JSON dumper library:

- Small interface without a lot of abstraction.
- Avoid memory allocations if possible (currently none, but maybe
  json_puts_string will be replaced to improve UTF-8 support).
- Do not implement parsing, this is currently handled by jsmn.

Methods to open/close array/objects and to set members are inspired by
the JsonGlib interface. The interfaces to write values is inspired by
the sharkd code (json_puts_string is also borrowed from that).

The only observed differences in the tshark output:
- JSON-GLib ignores duplicates, json_dumper does not and may produce
  duplicates and currently print two "ip.opt.sec_prot_auth_unassigned".
- JSON-GLib adds a space before a colon (unimportant formatting detail).
- (Not observed, but UTF-8 strings will be wrong like bug 14948.)

A test was added to catch changes in the tshark output. I also fuzzed
json_dumper with libFuzzer + UBSAN/ASAN and fixed an off-by-one error.

Change-Id: I0c85b18777b04d1e0f613a3d59935ec59be87ff4
Link: https://www.wireshark.org/lists/wireshark-dev/201811/msg00052.html
Reviewed-on: https://code.wireshark.org/review/30732
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>

2 files changed, 62 insertions, 0 deletions

diff --git a/test/baseline/elastic-mapping-ip-subset.json b/test/baseline/elastic-mapping-ip-subset.json
new file mode 100644
index 0000000000..49333ffc01
--- /dev/null
+++ b/test/baseline/elastic-mapping-ip-subset.json
@@ -0,0 +1,45 @@
+{
+  "template" : "packets-*",
+  "settings" : {
+    "index.mapping.total_fields.limit" : 1000000
+  },
+  "mappings" : {
+    "pcap_file" : {
+      "dynamic" : false,
+      "properties" : {
+        "timestamp" : {
+          "type" : "date"
+        },
+        "layers" : {
+          "properties" : {
+            "ip" : {
+              "properties" : {
+                "ip_version" : {
+                  "type" : "short"
+                },
+                "ip_tos_delay" : {
+                  "type" : "boolean"
+                },
+                "ip_len" : {
+                  "type" : "integer"
+                },
+                "ip_dst" : {
+                  "type" : "ip"
+                },
+                "ip_dst_host" : {
+                  "type" : "string"
+                },
+                "ip_geoip_lat" : {
+                  "type" : "float"
+                },
+                "ip_opt_padding" : {
+                  "type" : "byte"
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/test/suite_clopts.py b/test/suite_clopts.py
index 722769b08d..4a0d7b10ce 100644
--- a/test/suite_clopts.py
+++ b/test/suite_clopts.py
@@ -9,6 +9,8 @@
 #
 '''Command line option tests'''
 
+import json
+import os.path
 import subprocess
 import subprocesstest
 import fixtures
@@ -181,6 +183,21 @@ class case_tshark_dump_glossaries(subprocesstest.SubprocessTestCase):
         self.runProcess((cmd_tshark, '-G', 'plugins'), env=base_env)
         self.assertGreaterEqual(self.countOutput('dissector'), 10, 'Fewer than 10 dissector plugins found')
 
+    def test_tshark_elastic_mapping(self, cmd_tshark, dirs, base_env):
+        def get_ip_props(obj):
+            return obj['mappings']['pcap_file']['properties']['layers']['properties']['ip']['properties']
+        baseline_file = os.path.join(dirs.baseline_dir, 'elastic-mapping-ip-subset.json')
+        with open(baseline_file) as f:
+            expected_obj = json.load(f)
+        keys_to_check = get_ip_props(expected_obj).keys()
+        proc = self.assertRun((cmd_tshark, '-G', 'elastic-mapping', '--elastic-mapping-filter', 'ip'))
+        actual_obj = json.loads(proc.stdout_str)
+        ip_props = get_ip_props(actual_obj)
+        for key in list(ip_props.keys()):
+            if key not in keys_to_check:
+                del ip_props[key]
+        self.assertEqual(actual_obj, expected_obj)
+
 
 @fixtures.mark_usefixtures('test_env')
 @fixtures.uses_fixtures