metasploit-framework/dev/bh/outline.txt

04/19/2005

I. Introduction
   A. Who are we?
      1. spoonm
      2. skape
   B. Exploit Technology
      1. Three Phases of Exploitation
         a. Pre-exploitation
         b. Exploitation
         c. Post-exploitation
      2. Pre-exploitation - Preparing the payload
         a. NOP generation
         b. Payload encoders
         c. Connection handler initialization
      3. Exploitation - Leveraging the vulnerability
         a. Stack overflows
         c. Heap overflows
         b. SEH overwrites
         d. Arbitrary pointer overwrites
      4. Post-Exploitation - Manipulating the target
         a. Command shell redirection
         b. Arbitrary command execution
         c. Pivoting payloads
         d. Advanced payload interaction
   B. Where do we stand?
      1. Pre-exploitation
         a. Robust and elegant encoders do exist
            i. SkyLined's alpha-numeric encoder
            ii. Spoonm's Shikata Ga Nai
         b. Payload encoders generally taken for granted
            i. Most encoders are static with a variable key
            ii. IDS able to signature static decoder stubs
         c. NOP generation hasn't publically changed much
            i. PoC exploits generally use predictable nops, if any
            ii. ADMmutate easily signatured by most NIDS (Snort, Fnord)
            iii. Not considered very important to many researchers
         d. NIDS deployments are playing chase the tail
            i. The mouse always has the advantages; NIDS is reactive
            ii. Advanced nops and encoders push NIDS to its limits
      2. Exploitation
         a. Techniques have become very mature
            i. Linux/BSD exploitation techniques largely unchanged
            ii. Win32 heap overflows now more reliable (oded/shok)
            iii. Win32 SEH overwrites make exploitation easy, even on XPSP2
         b. Exploitation topics have been beaten to death
      3. Post-exploitation
         a. Common payloads are limited
            i. Command shell interaction has poor automation support
            ii. Limited to the command set that the interpreter provides
            iii. Bounded by the utilities installed on the target machine
            iv. Restrictive environments (chroot) can hinder command execution
            v. HIPS vendors becoming more adept at detecting basic payloads
               - LoadLibraryA from the stack, etc (mcafee 8.0i)
         b. Communication vectors largely unchanged
            i. Reverse and port-bind payloads still the most common
            ii. Findsock style payloads still unused by PoC exploits
            iii. Alternative communication vectors rarely discussed
         c. Pivoting technology exists
            i. Core ST described system call proxying in 2002
            ii. Metasploit's (2.3) meterpreter provides basic network pivoting
   C. What will we discuss?
      1. Pre-exploitation Research
         a. NOP generation
            i. Opty2
         b. Encoders
            i. Additive feedback encoders
            ii. Shikata Ga Nai
      2. Post-Exploitation Research
         a. Library Injection
            i. Facilitates things like Meterpreter and VNC injection
         b. VNC Injection
            i. Introduced at blackhat04 with the Metasploit 2.2 release
         c. Meterpreter & dN
            i. The cross-platform post-exploitation suite
      3. Payload Research
         a. PassiveX
            i. Taking advantage of ActiveX controls
         b. Ordinal Stagers
            i. Tiny network capable stagers
         c. Egghunt (maybe?)
            i. Small payload capable of locating a larger payload
            ii. Useful for exploits with limited space
II. Pre-exploitation
   A. Opty2
      1. spoonfu
   B. Additive feedback encoders
   C. Shikata Ga Nai
      1. spoonfu
III. Post-exploitation
   A. Library Injection
      1. Overview
         a. Paper published in 04/2004
         b. Provides advanced code execution
         c. Code can be written in any language that can compile down
            to a shared object.
         d. Allows developer to use all of the APIs exposed to a normal
            application.
         e. Detailed explanation can be found in included resources
            (include lib inject paper)
      2. Two types of library injection
         a. On-Disk
            i. Library is loaded from the target's harddrive or via a
               file share.
            ii. Can be detected by AV products due to fs access
         b. In-Memory
            i. Library is uploaded to the target and loaded from memory
               without touching the disk
            ii. Evades file system filter drivers, such as those
                provided by AV companies
            iii. Not touching the disk means no forensic trace
            iv. VirtualLock prevents swapping to disk, but requires admin
      3. In-memory library injection on Windows
         a. System calls used by the library loader are hooked
            i. NtCreateFile
            ii. NtMapViewOfSection
            iii. etc
         b. Unique image name is used to identify the image to image that
            is in memory
         c. System call hooks are removed so that future injectino can
            occur
         d. Alternative approaches
            i. Could do client-side relocations, but would need to handle
               import processing
      4. In-memory library injection on Linux/BSD
         a. No known public implementations
         b. Requires alternate approach
            i. Hooking API routines not always possible -- symtab not
               mapped into memory
            ii. libc symbol version mismatches lead to linking nightmare
         c. Client-side relocations seem most feasible
            i. Remote side maps a region of memory and sends the client 
               the base address
            ii. Client processes relocations and transmits the relocated
                image as its mapped segment would appear
            iii. Requires locating rtld base so that PLT lookups will
                 work
   B. VNC Injection
      1. Implements VNC as an injectable DLL
         a. Uses RealVNC as the code-base
         b. VNC communication uses the exploit connection
         c. No physical trace is left of the VNC server
         d. Can operate regardless of existing VNC installations
      2. Easy way to illustrate insecurities
         a. Suits understand mouse movement better than black box command 
            prompts
   C. Meterpreter
      1. Generic post-exploitation suite
         a. Based on library injection
         b. Uses the established exploit connection
            i. Especially powerful with findsock payloads; no new connection
         c. Executes entirely from memory
         d. No new processes or file access required for the payload to
            succeed
         e. Detailed explanation can be found in included resources
            (include meterpreter paper)
      2. Extension system provides advanced automation support
         a. No need to hand write tedious assembly
         b. Existing native code can be ported to a meterpreter extension
      3. Architecture
         a. Design goals
            i. Very flexible protocol; should adapt to extension requirements
            ii. Exposure of a channelized communication system to extensions
            iii. Stealth operation
            iv. Should be portable to various operating systems
            v. Client from one platform should work with server on another
               platform
         b. Protocol
            i. Uses TLVs (Type-Length-Value) to support arbitrary data
               passing.
            ii. TLVs allow the packet parser to be oblivious to the structure
                of the value field
            iii. Type field is broken down into meta types
      4. Core interface
         a. Overview
            i. Minimal interface to support the loading of extensions
            ii. Implements the basic packet transmission and dispatching
                facilities
            iii. Exposes channel allocation and management to extensions
         b. Advanced features
            i. Migrating the server instance between processes
      5. The ``stdapi'' extension
         a. Overview
            i. Included in Metasploit 3.0
            ii. Provides access to some of the common subsystems of the
                target operating system
            iii. Allows for easy automation and implementation of robust
                 post-exploitation scripts
         b. File System
            i. File and directory interaction
            ii. Files can be uploaded and downloaded between the
                attacker and the target
         c. Network
            i. Transparent network pivoting
            ii. Route table enumeration and manipulation
            iii. Local interface enumeration
         d. Process
            i. Process execution, optionally with channelized IO
            ii. Enumeration of running processes
            iii. Modification of arbitrary memory
            iv. Creation and modification of running threads
            v. Loading and interacting with shared object files
         e. Registry
            i. General registry API access
            ii. Opening, creating, and removing registry keys
            iii. Setting, querying, and deleting registry values
            iv. Enumeration of both keys and values
         f. User interface
            i. Disabling local user interaction via the keyboard
               and/or mouse (similar to VNC)
            ii. Idle timeout checking to see how long it's been
                since the user did something interactive
      6. The ``priv'' extension
         a. Still in development
         b. Exposes an interface to escalating local privileges
            through local vulnerabilities
         c. SAM dumping support similar to pwdump3
   D. dN
      1. spoonfu
IV. Payload Research
   A. PassiveX
      1. Overview
         a. Post-exploitation payload
         b. A derivative of On-Disk library injection that uses
            ActiveX controls
         c. Supports arbitrary DLL injection in any language that can
            be compiled as an ActiveX control (C++, VB, etc)
         d. Detailed analysis can be found in included resources
            (include passivex paper)
      2. Payload Implementation
         a. Disables iexplore Internet zone restrictions on 
            ActiveX controls
            i. Modifies four registry values that are stored per-user
         b. Launches a hidden iexplore at a URL with an embedded
            OCX
            i. The OCX does not have to be signed
            ii. No user interaction is required
            iii. OCX is automatically downloaded, registered, and loaded
                 into the browser's context
      3. Sample HTTP tunneling ActiveX control
         a. HTTP GET/POST used to build tunnel to attacker
            i. Uses the WININET API
            ii. Outbound traffic from target machine encapsulated in POST
                request
            iii. Inbound traffic from attacker encapsulated in GET response
            iv. Proxy configuration automatically inherited
            v. Requires HTTP server capable of performing encap/decap on the 
               HTTP packets
         b. Streaming connection through HTTP tunnel can be created
            i. socketpair doesn't exist natively on win32 but can be simulated
               with a local listener
            ii. Streaming abstraction allows advanced payloads to transparently
                use the HTTP transport (Meterpreter, VNC)
            iii. Local listener less covert, but highly beneficial
      4. Pros
         a. Bypasses restrictive outbound filters
         b. Re-uses proxy configuration
         c. Looks like normal user traffic
         d. Allows full access to the win32 API like all forms of 
            library injection
      5. Cons
         a. Touches the disk
         b. Requires administrative access
            i. Internet Explorer prohibits the downloading of 
               ActiveX controls as non-admin
   B. Windows Ordinal Stagers
      1. Overview
         a. Technique from Oded's lightning talk from core04
         b. Uses static ordinals to locate winsock symbol addresses
         c. Compatible with all versions of Windows
         d. 92 byte reverse stager, 93 byte findsock stager
         e. Detailed explanation can be found in included resources
            (include spoonm ordinal paper)
      2. Reverse Ordinal Stager
         a. Walks InitOrderModuleList searching for ws2_32
         b. Uses static ordinals to index the export table
         c. Creates fd with socket
         d. Chains connect and recv frames
         e. Returns into buffer read in from file descriptor
   C. Egghunting
      1. Overview
         a. Small stub payload that can search for a larger payload
         b. Useful for exploits that have limited payload space but can
            stash more payload elsewhere in memory
         c. Example exploits include the IE object type vulnerability.
         d. Goal is to safely search target address space for the larger
            payload.
         e. Larger payload is located by searching for an egg that is prepended
            to it.
         f. Detailed analysis can be found in included resources
            (include egghunt paper)
      2. Two primary methods of egghunting on Windows
         a. SEH
            1. 60 bytes in size, searches for an 8 byte egg, compatible with all
               versions of Windows (including 9x)
            2. Installs a custom exception handler
            3. Begins walking the address space
               i. When a bad address is encounter, the current pointer is
                  incremented by PAGE_SIZE
               ii. When a mismatch of the egg is encountered, the current pointer
                   is incremented by one
            4. Each address is compared against the 8-byte egg
               i. Bad addresses will throw exceptions which will be handled
                  by the custom exception handler
            5. When the egg is found, jump past the egg into the larger payload
         b. System call
            1. Very small stub (32 bytes), searches for an 8 byte egg, only
               compatible with NT+
            2. Uses a non-intrusive system call (NtDisplayString) to search validate
               addresses
               i. Same page walking logic as SEH is used
            3. When the egg is found, jump ast the egg into the larger payload
      3. One primary method of egghunting on Linux
         a. System call
            1. 30 bytes in size, searches for an 8 byte egg
            2. System call technique applies to other UNIX variants as well
            3. Uses the sigaction system call to validate 16 bytes at once
            4. Pros
               i. Very small
            5. Cons
               i. Corner cases may cause it to be unstable
V. The Complete Picture - Metasploit 3.0
   A. The power of pre-exploitation prepartion
      1. Abstract NOP generation
      2. Abstract payload encoding
      3. Abstract exploit connection handlers
         i. Bind handler
         ii. Reverse handler
         iii. Findsock handler
   B. The power of exploitat generalization
      1. Standardized exploit creation interface
         i. Robust target definitions
         ii. Detailed exploit implementation information
         iii. Entirely payload independent, no hardcoding paylaods
   C. The power of post-exploitation automation
      1. Complicated tasks made simple with scripting
         i. Want to download a targets entire harddrive?
         ii. Want to disable local user interaction?
         iii. Want to upload and play an mp3 on the target?
         iv. Want to 'be' on the target's network?
      2. Standard interface means cross platform support
VI. Conclusion - where do we go from here?
   A. Future Post-exploitation research
      1. Mesh network support 
      2. Expansion of the stdapi described in this document

cite:

STRIDE:
   http://www.ics.forth.gr/carv/acs/ACS/Activities/papers/stride-IFIP-SEC05.pdf

syscall proxy:
   http://www.coresecurity.com/files/files/11/SyscallProxying.pdf