Vault7: CIA Hacking Tools Revealed
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Caterpillar
Caterpillar Design
Requirements
Refer to Caterpillar v1.0 User Requirements Document (URD) IMIS: 2014-0638 Revision K January 30, 2014.
Use cases
Use Case 0: Operator exfiltrates a file.
Use Case 1: Operator exfiltrates arbitrary bytes of a file.
Use Case 2: Operator exfiltrates a glob.
Use Case 3: Operator resumes an aborted exfiltration.
Public interfaces
Low-side client
WinShell interface
TBD.
ICE interface
Will implement the Fire, Forget modes.
High-side server
TBD.
Runtime parameters
Low-side client
A resource will convey runtime parameters.
| Name | Type | Description | Default |
|---|---|---|---|
| subject_filenames | String[] | Absolute filenames with globbing, supporting environment variables |
C:\data.txt |
| caterpillar_chunksize | Unsigned Integer | Outer Caterpillar subject chunk size (B) | 1045876 (1 MB) |
| caterpillar_packetsize | Unsigned Integer | Maximum Size of RTP payload (B) | ??? |
| exfiltration_rate | Unsigned Integer | Bits per second | 1045876 (1 Mbps) |
| state_filename | String | Absolute filename to persist state, supporting environment variables | C:\state.txt |
| instance_identifier | Unsigned Integer | Deconflicts concurrent sessions | 0 |
| begin_index | Signed LongLong | Subject begin offset (modulo filesize, inclusive, B) | 0 |
| end_index | Signed LongLong | Subject end offset (modulo filesize, inclusive, B) | -1 |
| destination_ip | String | Destination IP | 192.168.100.100 |
| ticks_per_packet | Integer | Amount to increment RTP timestamp | 1000 |
High-side server
TBD.
Exfiltration algorithm
0. Open or initialize state file.
1. Open UDPUser Datagram Protocol socket.
2. Iterate over subject filenames.
2.0. Iterate over glob.
2.0.0. Consult state file.
2.0.0.0. If new mission, create an entry in the state file and set start_chunk to 0.
2.0.0.1. If previously completed mission, break.
2.0.0.2. If previously attempted mission set start_chunk to first unsent chunk.
2.0.1. Generate file metadata.
2.0.2. Iterate over chunks.
2.0.2.0. Build chunk payload containing data to send (if first chunk, start with file metadata)
2.0.2.1. Build chunk metadata.
2.0.2.2. Raptor the chunk, receiving one or more raptor packets in return.
2.0.2.3. For each raptor packet
2.0.2.3.0. Generate packet metadata.
2.0.2.3.1. Prepend packet metadata to packet buffer.
2.0.2.3.2. Generate RTP header.
2.0.2.3.3. Prepend RTP header to packet buffer.
2.0.2.3.4. Determine actual exfiltration rate.
2.0.2.3.5. Pause until actual falls below provisioned exfiltration rate.
2.0.2.3.6. Send RTP packet via UDPUser Datagram Protocol socket.
2.0.2.3.4. Update state file.
Resume algorithm
0. Search the state file for incomplete entries.
1. For each incomplete entry:
1.0. Run exfiltration algorithm.
Packet format
The Caterpillar low-side client will prepare a packet comprising an RTP header, packet metadata and raptored chunk metadata, file metadata and subject payload.
Basic strategy
given SUBJECT_FILE
ENHANCED_SUBJECT_FILE = FILE_METADATA(SUBJECT_FILE) + SUBJECT_FILE
CHUNKS = CHUNK(ENHANCED_SUBJECT_FILE)
ENHANCED_CHUNKS[i] = CHUNK_METADATA(CHUNKS[i]) + CHUNKS[i]
PACKETS[i] = RAPTOR(ENHANCED_CHUNKS[i])
ENHANCED_PACKETS[i][j] = PACKET_METADATA(PACKETS[i][j]) + PACKETS[i][j]
COVERED_PACKETS[i][j] = RTP_HEADER + ENHANCED_PACKETS[i][j]
| subject file |
||||||||||||||
file |
subject file |
|||||||||||||
| chunk 0 |
... | chunk k |
||||||||||||
| chunk 0 metadata |
chunk 0 | ... | chunk |
chunk k |
||||||||||
| packet 00 |
... | packet 0m |
... | packet k0 |
... | packet km |
||||||||
| packet 00 metadata |
packet 00 |
... | packet 0m metadata |
packet 0m |
... | packet k0 metadata |
packet k0 |
... | packet km metadata |
packet km |
||||
RTP |
packet 00 metadata |
packet 00 |
... | RTP header |
packet |
packet 0m |
... | RTP header |
packet k0 metadata |
packet k0 |
... | RTP header |
packet km metadata |
packet km |
The purpose of the RTP encapsulation is deception. We use 53 for the payload type because it is in the middle of the longest series of unassigned values. The complete list is: [20, 24], 27, 29, 30, [35, 71] and [77, 95].
| Offset (b) | Length (b) | Name | Value |
|---|---|---|---|
| 0 | 2 | Version | 2 |
| 2 | 1 | Padding | 0 |
| 3 | 1 | Extension header present | 0 |
| 4 | 4 | Contributing source (CSRC) count | 0 |
| 8 | 1 | Marker | 0 |
| 9 | 7 | Payload type | 53 |
| 16 | 16 | Sequence number | 1-up counter |
| 32 | 32 | Timestamp | ticks_per_packet-up counter |
| 64 | 32 | Synchronization source (SSRC) | 0x00000000 |
| 96 | CSRC count * 32 | CSRC list | N/A |
| 96 + CSRC count * 32 | variable | Extension header | N/A |
The purpose of the packet metadata is to document the chunk reassembly. File ID is a hash of the file name.
| Offset (B) | Length (B) | Name |
|---|---|---|
| 0 | 4 | Instance ID |
| 4 | 4 | File ID |
| 8 | 4 | Chunk ID |
The purpose of the chunk metadata is to document the file reassembly. File ID is a hash of the file name.
| Offset (B) | Length (B) | Name |
|---|---|---|
| 0 | 4 | Instance ID |
| 4 | 4 | File ID |
| 8 | 8 | File size |
| 16 | 8 | Chunk begin index (inclusive) |
| 24 | 8 | Chunk end index (inclusive) |
The purpose of the file metadata is to document the operation.
| Offset (B) | Length (B) | Name |
|---|---|---|
| 0 | 4 | Instance ID |
| 4 | 8 | Exfiltration time (Windows File Time format) |
| 12 | 8 | File begin index (inclusive) |
| 20 | 8 | File end index (inclusive) |
| 28 | 4 | File name size (in bytes) |
| 32 | Variable | File name (utf-8 encoded) |
Globbing
Globbing is pattern-matching based on wildcard characters; it is not a regular expression capability. Globbing operators are not standardized: Caterpillar will use the WinAPI implementation of globbing, specifically calls to FindFirstFile() and FindNextFile().
Obfuscating the metadata
We considered symmetric-key XOR, RC4 and AESAdvanced Encryption Standard techniques for obfuscating the metadata. The first iteration will use XOR with an eight bit symmetric key, and we can upgrade to a stronger mechanism in a later iteration. This capability cannot be considered encryption because the key is present in the low-side client.