This Metasploit module exploits a integer overflow vulnerability in the Stagefright Library (libstagefright.so). The vulnerability occurs when parsing specially crafted MP4 files. While a wide variety of remote attack vectors exist, this particular exploit is designed to work within an HTML5 compliant browser. Exploitation is done by supplying a specially crafted MP4 file with two tx3g atoms that, when their sizes are summed, cause an integer overflow when processing the second atom. As a result, a temporary buffer is allocated with insufficient size and a memcpy call leads to a heap overflow. This version of the exploit uses a two-stage information leak based on corrupting the MetaData that the browser reads from mediaserver. This method is based on a technique published in NorthBit's Metaphor paper. First, we use a variant of their technique to read the address of a heap buffer located adjacent to a SampleIterator object as the video HTML element's videoHeight. Next, we read the vtable pointer from an empty Vector within the SampleIterator object using the video element's duration. This gives us a code address that we can use to determine the base address of libstagefright and construct a ROP chain dynamically. NOTE: the mediaserver process on many Android devices (Nexus, for example) is constrained by SELinux and thus cannot use the execve system call. To avoid this problem, the original exploit uses a kernel exploit payload that disables SELinux and spawns a shell as root. Work is underway to make the framework more amenable to these types of situations. Until that work is complete, this exploit will only yield a shell on devices without SELinux or with SELinux in permissive mode.
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