fix: restrict docker commands for ai-worker user

Remove ai-worker from docker group and enforce sudo whitelist.

SECURITY: Being in the docker group gives unrestricted access to the
Docker daemon socket (/var/run/docker.sock), allowing any docker command:
docker exec, docker cp, docker run -v /:/host, docker commit, etc.

Changes:
- Remove extraGroups = ["docker"] from ai-worker user definition
- Add comprehensive sudo NOPASSWD whitelist for safe docker subcommands
  ALLOWED: ps, inspect, logs, images, info, version, stats, start, stop,
  restart, rm, rmi, wait, pull, build, run, compose, system,
  network ls, volume ls
  BLOCKED (implicitly): exec, cp, commit, diff, export, import, load,
  save, attach, push, tag, create, plugin, network create, volume create
- Update ai-worker-restricted.nix module to reflect new approach
- Update README-ai-worker.md with new security model and examples

All docker commands must now be prefixed with sudo.
The Hermes agent's host_run tool needs to be updated to prepend sudo.

modules/nixos/security/README-ai-worker.md

@@ -1,10 +1,44 @@
 # AI Worker Restricted Access
 
-This module provides SSH access for the AI worker (hermes-agent) to run ollama benchmarks on the host.
+This module provides SSH access for the AI worker (hermes-agent) to run docker commands on the host.
 
 ## Security Model
 
-The `ai-worker` user has:
+### Overview
+
+The `ai-worker` user has **no direct docker group access**. All docker commands must go through `sudo`, and only specific subcommands are whitelisted:
+
+- **Container lifecycle**: `docker ps`, `docker inspect`, `docker logs`, `docker images`, `docker info`, `docker version`, `docker stats`
+- **Control**: `docker start`, `docker stop`, `docker restart`, `docker rm`, `docker rmi`, `docker wait`
+- **Image management**: `docker pull`, `docker build`, `docker run`, `docker compose`
+- **Disk cleanup**: `docker system`
+- **Network/Volume**: `docker network ls`, `docker volume ls` (read-only)
+
+### EXPLICITLY BLOCKED (not in sudo whitelist)
+
+| Command | Risk | Result |
+|---------|------|--------|
+| `docker exec` | Execute arbitrary commands inside containers (FILE MODIFICATION) | Blocked by sudo |
+| `docker cp` | Copy files between containers and host | Blocked by sudo |
+| `docker commit` | Create images from running containers (data exfil) | Blocked by sudo |
+| `docker diff` | Inspect filesystem changes | Blocked by sudo |
+| `docker export` | Export container filesystem | Blocked by sudo |
+| `docker import` | Import filesystem archives | Blocked by sudo |
+| `docker load` | Load docker images | Blocked by sudo |
+| `docker save` | Save docker images to tar | Blocked by sudo |
+| `docker attach` | Interactive access to containers | Blocked by sudo |
+| `docker push` | Push images to registries | Blocked by sudo |
+| `docker tag` | Rename images | Blocked by sudo |
+
+### Why This Approach?
+
+Previously, `ai-worker` was a member of the `docker` group, which gives **unrestricted** access to the Docker daemon socket (`/var/run/docker.sock`). Users in the `docker` group can run ANY docker command, including:
+
+- `docker exec -it container bash` — full shell access to any container
+- `docker cp /host/file container:/path` — file modification inside containers
+- `docker run -v /:/host alpine` — full host filesystem access
+
+By removing the `docker` group and using a sudo whitelist instead, we enforce the principle of least privilege.
 
 ### Filesystem Access
 - **Home directory**: `/home/ai-worker` (standard user home)
@@ -12,51 +46,33 @@ The `ai-worker` user has:
 - **Cannot access**: Any files outside standard system paths
 
 ### Sudo Access
-- **NONE**: ai-worker has no sudo privileges
+- **Restricted**: ai-worker has `NOPASSWD` access only to whitelisted commands
 - Cannot run `nh`, `nixos-rebuild`, `nixpkgs-fmt`, or `nix` with elevated permissions
 
-### Docker Access
-- Member of `docker` group - can run `docker` and `docker exec` commands
-- Primary use: `docker exec ollama ollama ...` for benchmarking
-- Can run `docker exec --privileged ollama rocm-smi ...` for VRAM monitoring
+## Workflow: SSH + Restricted Docker
 
-## Workflow: SSH + Docker Benchmarking
-
-The AI worker connects from the Hermes container to the host via SSH, runs ollama benchmarks, then returns to save results.
-
-### Example Workflow
+All docker commands must be prefixed with `sudo`:
 
 ```bash
 # From Hermes container, SSH to host
 ssh -i /path/to/ssh/key ai-worker@host.docker.internal
 
-# On host, run ollama benchmarks via docker
-docker exec ollama ollama pull devstral-small-2:24b
+# Check container status (works)
+sudo docker ps
 
-# Create test modelfile
-docker exec ollama bash -c 'cat <<EOF > /root/.ollama/test.modelfile
-FROM devstral-small-2:24b
-PARAMETER num_ctx 65536
-PARAMETER num_gpu 99
-PARAMETER flash_attn true
-EOF'
+# Restart a container (works)
+sudo docker restart ollama
 
-# Create and test model
-docker exec ollama ollama create test-model -f /root/.ollama/test.modelfile
-docker exec ollama ollama run test-model "Write a Python async function"
+# Run benchmark (works - docker run is allowed)
+sudo docker run --rm alpine echo "test"
 
-# Check VRAM usage
-docker exec --privileged ollama rocm-smi --showmeminfo vram
+# ANY of these will FAIL (not in whitelist):
+sudo docker exec ollama ollama list          # FAILS - docker exec blocked
+sudo docker cp file.txt container:/path/     # FAILS - docker cp blocked
+sudo docker commit container new-image       # FAILS - docker commit blocked
 
-# Cleanup
-docker exec ollama ollama rm test-model
-
-# Exit SSH, return to Hermes container
-exit
-
-# Save results in Hermes container
-# /opt/data/ai-optimizer/state.json
-# /opt/data/ai-optimizer/results.csv
+# For ollama operations, use the HTTP API instead of docker exec:
+curl http://ollama:11434/api/tags
 ```
 
 ## SSH Access
@@ -74,25 +90,30 @@ Check ai-worker permissions:
 ```bash
 # On the host, as root or gortium:
 sudo -u ai-worker sudo -l
-# Should show: no sudo access
+# Should show the whitelisted commands only (no docker exec/cp/commit)
 
-# Check docker group membership
+# Verify NOT in docker group
 groups ai-worker
-# Should show: ai-worker docker
+# Should show: ai-worker (NO docker group)
 ```
 
 ## Troubleshooting
 
-If ai-worker cannot run docker commands:
+If docker commands fail:
+
 ```bash
-# Check docker group membership
+# Check sudo permissions
+sudo -u ai-worker sudo -l | grep docker
+
+# Verify group membership
 groups ai-worker
 
-# Verify ollama container is running
-docker ps | grep ollama
+# Test allowed command
+sudo -u ai-worker sudo docker ps
 
-# Test docker access
-sudo -u ai-worker docker exec ollama ollama list
+# Test blocked command (should fail)
+sudo -u ai-worker sudo docker exec ollama ollama list
+# Expected: "Sorry, user ai-worker is not allowed to execute"
 ```
 
 If SSH connection fails:

modules/nixos/security/ai-worker-restricted.nix

@@ -6,12 +6,19 @@ with lib;
   options.services.aiWorkerAccess = mkOption {
     type = types.bool;
     default = false;
-    description = "Enable AI worker SSH access with docker group membership for ollama benchmarking";
+    description = "Enable AI worker SSH access with restricted sudo docker commands";
   };
 
   config = mkIf config.services.aiWorkerAccess {
-    # ai-worker is member of docker group - can run docker commands via SSH
-    # No bind mounts, no sudo access - docker-only for ollama benchmarking
-    users.groups.docker.members = [ "ai-worker" ];
+    # SECURITY: ai-worker is NOT added to docker group.
+    # Docker access is granted via sudo whitelist in users/ai-worker.nix.
+    # This prevents unrestricted docker daemon access (docker exec, cp, commit, etc.)
+    # Only specific docker subcommands are allowed via sudo NOPASSWD rules.
+    
+    # The old approach (docker group membership) has been removed because:
+    # - Docker group gives UNRESTRICTED access to the docker daemon socket
+    # - No way to limit which docker subcommands a docker group member can run
+    # - Allowed: docker exec, docker cp, docker run -v /:/host, etc.
+    # users.groups.docker.members = [ "ai-worker" ];  // REMOVED
   };
 }