Merge #22: Clamp JSON object depth to PHP limit

54c4015 Clamp JSON object depth to PHP limit (Jeff Garzik)

Pull request description:

  Cherry-picks jgarzik#64 to fix CVE-2019-18936.

  Based on fe2227d

ACKs for top commit:
  MarcoFalke:
    ACK 54c4015 📣

Tree-SHA512: d21458bcfdd37abd84daad46cead0635098d3b1ecd86720c48e724f5e3fcbea39692e1b1fbb2e0d9401a5121df44f280dc6eba8e3ace474c8f4cdb81004a6189

Makefile.am

@@ -95,6 +95,7 @@ TEST_FILES = \
 	$(TEST_DATA_DIR)/fail41.json \
 	$(TEST_DATA_DIR)/fail42.json \
 	$(TEST_DATA_DIR)/fail44.json \
+	$(TEST_DATA_DIR)/fail45.json \
 	$(TEST_DATA_DIR)/fail3.json \
 	$(TEST_DATA_DIR)/fail4.json \
 	$(TEST_DATA_DIR)/fail5.json \
@@ -105,6 +106,7 @@ TEST_FILES = \
 	$(TEST_DATA_DIR)/pass1.json \
 	$(TEST_DATA_DIR)/pass2.json \
 	$(TEST_DATA_DIR)/pass3.json \
+	$(TEST_DATA_DIR)/pass4.json \
 	$(TEST_DATA_DIR)/round1.json \
 	$(TEST_DATA_DIR)/round2.json \
 	$(TEST_DATA_DIR)/round3.json \

lib/univalue_read.cpp

@@ -8,6 +8,14 @@
 #include "univalue.h"
 #include "univalue_utffilter.h"
 
+/*
+ * According to stackexchange, the original json test suite wanted
+ * to limit depth to 22.  Widely-deployed PHP bails at depth 512,
+ * so we will follow PHP's lead, which should be more than sufficient
+ * (further stackexchange comments indicate depth > 32 rarely occurs).
+ */
+static const size_t MAX_JSON_DEPTH = 512;
+
 static bool json_isdigit(int ch)
 {
     return ((ch >= '0') && (ch <= '9'));
@@ -323,6 +331,9 @@ bool UniValue::read(const char *raw, size_t size)
                 stack.push_back(newTop);
             }
 
+            if (stack.size() > MAX_JSON_DEPTH)
+                return false;
+
             if (utyp == VOBJ)
                 setExpect(OBJ_NAME);
             else

test/fail45.json

@@ -0,0 +1 @@
+[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]

test/pass4.json

@@ -0,0 +1 @@
+[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]

test/unitester.cpp

@@ -114,6 +114,7 @@ static const char *filenames[] = {
         "fail41.json",               // invalid unicode: unfinished UTF-8
         "fail42.json",               // valid json with garbage following a nul byte
         "fail44.json",               // unterminated string
+        "fail45.json",               // nested beyond max depth
         "fail3.json",
         "fail4.json",                // extra comma
         "fail5.json",
@@ -124,6 +125,7 @@ static const char *filenames[] = {
         "pass1.json",
         "pass2.json",
         "pass3.json",
+        "pass4.json",
         "round1.json",              // round-trip test
         "round2.json",              // unicode
         "round3.json",              // bare string