From 22a7d04fa004462e0dca35c3cc7809bea38e65f9 Mon Sep 17 00:00:00 2001
From: Max Bruckner <max@maxbruckner.de>
Date: Fri, 2 Mar 2018 19:49:55 +0100
Subject: [PATCH 1/2] add_item_to_object: Fix use-after-free when string is
 aliased

If the `string` property of the item that is added is an alias to the
`string` parameter of `add_item_to_object`, and `constant` is false,
`cJSON_strdup` would access the string after it has been freed.

Thanks @hhallen for reporting this in #248.
---
 cJSON.c            | 37 +++++++++++++++++++++----------------
 tests/misc_tests.c | 20 ++++++++++++++++++++
 2 files changed, 41 insertions(+), 16 deletions(-)

diff --git a/cJSON.c b/cJSON.c
index 3dcde3d..cf48ac9 100644
--- a/cJSON.c
+++ b/cJSON.c
@@ -1895,32 +1895,37 @@ static void* cast_away_const(const void* string)
 
 static cJSON_bool add_item_to_object(cJSON * const object, const char * const string, cJSON * const item, const internal_hooks * const hooks, const cJSON_bool constant_key)
 {
+    char *new_key = NULL;
+    int new_type = cJSON_Invalid;
+
     if ((object == NULL) || (string == NULL) || (item == NULL))
     {
         return false;
     }
 
+    if (constant_key)
+    {
+        new_key = (char*)cast_away_const(string);
+        new_type = item->type | cJSON_StringIsConst;
+    }
+    else
+    {
+        new_key = (char*)cJSON_strdup((const unsigned char*)string, hooks);
+        if (new_key == NULL)
+        {
+            return false;
+        }
+
+        new_type = item->type & ~cJSON_StringIsConst;
+    }
+
     if (!(item->type & cJSON_StringIsConst) && (item->string != NULL))
     {
         hooks->deallocate(item->string);
     }
 
-    if (constant_key)
-    {
-        item->string = (char*)cast_away_const(string);
-        item->type |= cJSON_StringIsConst;
-    }
-    else
-    {
-        char *key = (char*)cJSON_strdup((const unsigned char*)string, hooks);
-        if (key == NULL)
-        {
-            return false;
-        }
-
-        item->string = key;
-        item->type &= ~cJSON_StringIsConst;
-    }
+    item->string = new_key;
+    item->type = new_type;
 
     return add_item_to_array(object, item);
 }
diff --git a/tests/misc_tests.c b/tests/misc_tests.c
index a900e8f..a0b4f7e 100644
--- a/tests/misc_tests.c
+++ b/tests/misc_tests.c
@@ -508,6 +508,25 @@ static void cjson_create_array_reference_should_create_an_array_reference(void)
     cJSON_Delete(number_reference);
 }
 
+static void cjson_add_item_to_object_should_not_use_after_free_when_string_is_aliased(void)
+{
+    cJSON *object = cJSON_CreateObject();
+    cJSON *number = cJSON_CreateNumber(42);
+    char *name = (char*)cJSON_strdup((const unsigned char*)"number", &global_hooks);
+
+    TEST_ASSERT_NOT_NULL(object);
+    TEST_ASSERT_NOT_NULL(number);
+    TEST_ASSERT_NOT_NULL(name);
+
+    number->string = name;
+
+    /* The following should not have a use after free
+     * that would show up in valgrind or with AddressSanitizer */
+    cJSON_AddItemToObject(object, number->string, number);
+
+    cJSON_Delete(object);
+}
+
 int main(void)
 {
     UNITY_BEGIN();
@@ -530,6 +549,7 @@ int main(void)
     RUN_TEST(cjson_create_string_reference_should_create_a_string_reference);
     RUN_TEST(cjson_create_object_reference_should_create_an_object_reference);
     RUN_TEST(cjson_create_array_reference_should_create_an_array_reference);
+    RUN_TEST(cjson_add_item_to_object_should_not_use_after_free_when_string_is_aliased);
 
     return UNITY_END();
 }

From 5da9edc8b145d4f335267a23076c63a90a78b672 Mon Sep 17 00:00:00 2001
From: Max Bruckner <max@maxbruckner.de>
Date: Fri, 2 Mar 2018 19:57:36 +0100
Subject: [PATCH 2/2] Release version 1.7.4

---
 CHANGELOG.md   | 8 +++++++-
 CMakeLists.txt | 2 +-
 Makefile       | 2 +-
 cJSON.c        | 2 +-
 cJSON.h        | 2 +-
 5 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 001269b..b40c895 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,10 @@
-1.7.2
+1.7.4
+=====
+Fixes:
+------
+* Fix potential use after free if the `string` parameter to `cJSON_AddItemToObject` is an alias of the `string` property of the object that is added (#248). Thanks @hhallen for reporting.
+
+1.7.3
 =====
 Fixes:
 ------
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 774280e..41b8b29 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@ include(GNUInstallDirs)
 
 set(PROJECT_VERSION_MAJOR 1)
 set(PROJECT_VERSION_MINOR 7)
-set(PROJECT_VERSION_PATCH 3)
+set(PROJECT_VERSION_PATCH 4)
 set(CJSON_VERSION_SO 1)
 set(CJSON_UTILS_VERSION_SO 1)
 set(PROJECT_VERSION "${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}.${PROJECT_VERSION_PATCH}")
diff --git a/Makefile b/Makefile
index 1b4552b..01ee754 100644
--- a/Makefile
+++ b/Makefile
@@ -8,7 +8,7 @@ CJSON_TEST_SRC = cJSON.c test.c
 
 LDLIBS = -lm
 
-LIBVERSION = 1.7.3
+LIBVERSION = 1.7.4
 CJSON_SOVERSION = 1
 UTILS_SOVERSION = 1
 
diff --git a/cJSON.c b/cJSON.c
index cf48ac9..b4fc727 100644
--- a/cJSON.c
+++ b/cJSON.c
@@ -82,7 +82,7 @@ CJSON_PUBLIC(char *) cJSON_GetStringValue(cJSON *item) {
 }
 
 /* This is a safeguard to prevent copy-pasters from using incompatible C and header files */
-#if (CJSON_VERSION_MAJOR != 1) || (CJSON_VERSION_MINOR != 7) || (CJSON_VERSION_PATCH != 3)
+#if (CJSON_VERSION_MAJOR != 1) || (CJSON_VERSION_MINOR != 7) || (CJSON_VERSION_PATCH != 4)
     #error cJSON.h and cJSON.c have different versions. Make sure that both have the same.
 #endif
 
diff --git a/cJSON.h b/cJSON.h
index b6937b3..4dc1cfb 100644
--- a/cJSON.h
+++ b/cJSON.h
@@ -31,7 +31,7 @@ extern "C"
 /* project version */
 #define CJSON_VERSION_MAJOR 1
 #define CJSON_VERSION_MINOR 7
-#define CJSON_VERSION_PATCH 3
+#define CJSON_VERSION_PATCH 4
 
 #include <stddef.h>