Clamp JSON object depth to PHP limit

Based on fe2227d4ace9d4d5b30710684c9d3b1012e3c0fc.
Fuzzbawls · Dec 15, 2019 · 54c4015 · 54c4015
1 parent 5a58a46
commit 54c4015
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diff --git a/Makefile.am b/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 \

diff --git a/lib/univalue_read.cpp b/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

diff --git a/test/fail45.json b/test/fail45.json
@@ -0,0 +1 @@
+[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]
diff --git a/test/pass4.json b/test/pass4.json
@@ -0,0 +1 @@
+[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[[]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]
diff --git a/test/unitester.cpp b/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