Snapshot Attack Demo
This is the original demo of Unanticipated Snapshot Attack found by us. Thanks Intel for the Security Advisory.
Build the demo
Install Intel SGX SDK and Occlum
First of all, anyone willing to run the demo must install Intel SGX SDK and Occlum (you can choose to use our modified SGX SDK). We provide a Dockerfile for fast Occlum/SDK installation. The modified SGX SDK is to help the attacker to decide the timing.
You can also install Occlum on the host machine. (Please refer to https://github.com/occlum/occlum for more installation details.) Either way, you will need to install Intel SGX driver on your host first, or use a in-kernel SGX driver.
(sudo) docker build -t $Your_Image_Name .
After the image is built, run
(sudo) docker run -it --privileged -p $Redis_Server_Port:6379 -v $Host_SGX_Driver_Path:/dev/sgx --name "snapshot-demo" $Your_Image_Name
Here $Redis_Server_Port is the host port number that you would like to expose for the in-container Redis server, while $Host_SGX_Driver_Path is the abovementioned device path of your installed SGX driver.
Build the target program
The target program is at the bash_redis folder.
The victim program is running a bash-shell script (occlum_bash.sh). It first fetches a provisioned password, to generate a customized Redis configuration file, with the "requirepass" entry filled. Then it invokes a Redis server, according to the customized config file.
To build the config generation program, run make. To build the Redis server, execute the following commands.
cd bash_redis
./download_and_build_redis_glibc.sh
Run the demo
Make sure that the victim Redis program works
Open a terminal for the victim. Run run_redis.sh, checking if the Redis server works well.
Using command redis-cli -h $Redis_Server_IP -p $Redis_Server_Port -a admin123456 to verify whether the password (admin123456) has been set in the config file.
Press ctrl + C to terminate the Redis server.
Snapshot capture
Prepare 2 terminals, one for the victim and one for the attacker. You can only open one more terminal (for the attacker) if one terminal has been opened already for the victim.
Run run_redis.sh at the victim terminal again. This script will start up the target program.
The attacker needs to take a snapshot (using ./take_snapshot_step-1.sh) when he/she can determine that the snapshot is flushing. In the demo, the attacker can get a clear notice from the victim's terminal as follows.
...
Run ./take_snapshot_step-1.sh NOW!
line 4522: # passwords, then flags, or key patterns. However note that the additive
line 4523: # and subtractive rules will CHANGE MEANING depending on the ordering.
line 4524: # For instance see the following example:
...
Launch the ./take_snapshot_step-1.sh script on the attacker's terminal.
If you build Occlum with our modified SGX SDK, you will see more hint message. This is because we modified the untrusted part of Intel SGX SDK, printing helper messages to facilitate the attacker to decide the timing. For attacker's convenience, we reserve time slots to allow the attacker to run ./take_snapshot_step-1.sh. In fact, the attacker who has host root privilege could intercept the enclave execution and capture any snapshots by modifying the untrusted part of SGX SDK.
Once upon the Redis server is up and running, run ./take_snapshot_step-2.sh to complete the snapshot collection.
Enclave replay
The attacker executes replay_redis.sh to replay the enclave using our collected snapshot. Any client can log onto the Redis server without authentication.
Example command for Redis client:
redis-cli -h $Redis_Server_IP -p $Redis_Server_Port
keys *
If a message of (error) NOAUTH Authentication required. is prompted, it means you will need a password to access the Redis server. Type auth $Your_Password to pass the authentication. Use auth admin123456 in this demo.
If a message of (empty array) is prompted, it means you do not need a password to access the Redis server.
Note
Sometimes the demo fails due to Occlum's integrity check. You probably see the following message.
Replaying ...
~/snapshot-demo/bash_redis_replay/occlum_instance ~/snapshot-demo/bash_redis_replay
In: writing meta-data in write_all_changes_to_disk
In: writing meta-data in write_all_changes_to_disk
Error: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }
[ERROR] occlum-pal: The init process exit with code: 1 (line 59, file src/pal_api.c)
[ERROR] occlum-pal: Failed to run the init process: EINVAL (line 129, file src/pal_api.c)
Simply run the demo again (from the record phase), then the error will be gone for good.
GL & HF!