CVE-2017-6439: Out-of-bounds Write (CWE-787)
value: Heap-based buffer overflow in the parse_string_node function in bplist.c in libimobiledevice libplist 1.12 allows local users to cause a denial of service (out-of-bounds write) via a crafted plist file.
CWE description: The product writes data past the end, or before the beginning, of the intended buffer.
CVSS v3 base score: 5
Published: 2017-03-15T14:59Z
Repository: https://github.com/libimobiledevice/libplist
Language: C
Files changed: src/bplist.c
Commit date: 2017-02-10 13:42:46 +0100
Commit message: bplist: Fix data range check for string/data/dict/array nodes

Passing a size of 0xFFFFFFFFFFFFFFFF to parse_string_node() might result
in a memcpy with a size of -1, leading to undefined behavior.
This commit makes sure that the actual node data (which depends on the size)
is in the range start_of_object..start_of_object+size.

Credit to OSS-Fuzz

Diff: diff --git a/src/bplist.c b/src/bplist.c
index 0fd149e..7d21b27 100644
--- a/src/bplist.c
+++ b/src/bplist.c
@@ -652,37 +652,37 @@ static plist_t parse_bin_node(struct bplist_data *bplist, const char** object)
             return NULL;
         }
         return parse_date_node(object, size);
 
     case BPLIST_DATA:
-        if (*object + size > bplist->offset_table) {
+        if (*object + size < *object || *object + size > bplist->offset_table) {
             PLIST_BIN_ERR("%s: BPLIST_DATA data bytes point outside of valid range\n", __func__);
             return NULL;
         }
         return parse_data_node(object, size);
 
     case BPLIST_STRING:
-        if (*object + size > bplist->offset_table) {
+        if (*object + size < *object || *object + size > bplist->offset_table) {
             PLIST_BIN_ERR("%s: BPLIST_STRING data bytes point outside of valid range\n", __func__);
             return NULL;
         }
         return parse_string_node(object, size);
 
     case BPLIST_UNICODE:
         if (size*2 < size) {
             PLIST_BIN_ERR("%s: Integer overflow when calculating BPLIST_UNICODE data size.\n", __func__);
             return NULL;
         }
-        if (*object + size*2 > bplist->offset_table) {
+        if (*object + size*2 < *object || *object + size*2 > bplist->offset_table) {
             PLIST_BIN_ERR("%s: BPLIST_UNICODE data bytes point outside of valid range\n", __func__);
             return NULL;
         }
         return parse_unicode_node(object, size);
 
     case BPLIST_SET:
     case BPLIST_ARRAY:
-        if (*object + size > bplist->offset_table) {
+        if (*object + size < *object || *object + size > bplist->offset_table) {
             PLIST_BIN_ERR("%s: BPLIST_ARRAY data bytes point outside of valid range\n", __func__);
             return NULL;
         }
         return parse_array_node(bplist, object, size);
 
@@ -692,12 +692,12 @@ static plist_t parse_bin_node(struct bplist_data *bplist, const char** object)
             return NULL;
         }
         return parse_uid_node(object, size);
 
     case BPLIST_DICT:
-        if (*object + size > bplist->offset_table) {
-            PLIST_BIN_ERR("%s: BPLIST_REAL data bytes point outside of valid range\n", __func__);
+        if (*object + size < *object || *object + size > bplist->offset_table) {
+            PLIST_BIN_ERR("%s: BPLIST_DICT data bytes point outside of valid range\n", __func__);
             return NULL;
         }
         return parse_dict_node(bplist, object, size);
 
     default:

Vulnerable code:         if (*object + size > bplist->offset_table) {
        if (*object + size > bplist->offset_table) {
        if (*object + size*2 > bplist->offset_table) {
        if (*object + size > bplist->offset_table) {
        if (*object + size > bplist->offset_table) {
            PLIST_BIN_ERR("%s: BPLIST_REAL data bytes point outside of valid range\n", __func__);
Fixed code:         if (*object + size < *object || *object + size > bplist->offset_table) {
        if (*object + size < *object || *object + size > bplist->offset_table) {
        if (*object + size*2 < *object || *object + size*2 > bplist->offset_table) {
        if (*object + size < *object || *object + size > bplist->offset_table) {
        if (*object + size < *object || *object + size > bplist->offset_table) {
            PLIST_BIN_ERR("%s: BPLIST_DICT data bytes point outside of valid range\n", __func__);