How to install Mythic and agents in an offline environment
This guide will assume you can install Mythic on a box that has Internet access and then migrate to your offline testing/development environment.

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Setup

  1. Install Mythic following the normal installation
  2. With Mythic running, install any other agents or profiles you might need/want. 
sudo ./mythic-cli install github https://github.com/MythicAgents/Apollo
3. Export your docker containers. Make sure you also save the tags. 
docker save $(docker images -q) -o mythic_images.tar
docker images | sed '1d' | awk '{print $1 " " $2 " " $3}' > mythic_tags
4. Download donut from pypi. (this is apollo specific, so there might be others depending on your agent) 
mkdir Payload_Types/apollo/depends
pip3 download donut -d Payload_Types/apollo/depends
Download Apollo dependencies (apollo specifically installs these dynamically within the Docker container at build-time, so pre-fetch these) 
 wget https://www.nuget.org/api/v2/package/Fody/2.0.0 -O Payload_Types/apollo/depends/fody.2.0.0.nupkg
 wget https://www.nuget.org/api/v2/package/Costura.Fody/1.6.2 -O Payload_Types/apollo/depends/costura.fody.1.6.2.nupkg
5. Tar Mythic directoy. 
tar cfz mythic.tar.gz /Mythic
6. Push mythic_images.tar, mythic_tags, and mythic.tar.gz to your offline box. 7. Import docker images and restore tags. 
docker load -i mythic_images.tar
while read REPOSITORY TAG IMAGE_ID; do echo "== Tagging $REPOSITORY $TAG $IMAGE_ID =="; docker tag "$IMAGE_ID" "$REPOSITORY:$TAG"; done < mythic_tags
8. Extract Mythic directory. 
tar xfz mythic.tar.gz
cd mythic

from itsafeaturemythic/csharp_payload:0.1.1

COPY ["depends/donut-0.2.2.tar.gz", "donut-0.2.2.tar.gz"]
COPY ["depends/costura.fody.1.6.2.nupkg", "costura.fody.1.6.2.nupkg"]
COPY ["depends/fody.2.0.0.nupkg", "fody.2.0.0.nupkg"]

RUN /usr/local/bin/python3.8 -m pip install /donut-0.2.2.tar.gz
RUN mkdir /mythic_nuget
RUN nuget sources add -name mythic_nuget -source /mythic_nuget
RUN nuget sources disable -name nuget.org
RUN nuget add /fody.2.0.0.nupkg -source /mythic_nuget
RUN nuget add /costura.fody.1.6.2.nupkg -source /mythic_nuget
10. Start Mythic 
sudo ./mythic-cli start
Normally, Mythic containers will try to re-build every time you bring them down and back up. This might not be great for an offline environment. The configuration variable, REBUILD_ON_START, can be set to false to tell Mythic that the containers should specifically NOT be rebuilt when restarted.