fix: restrict docker commands for ai-worker (wrapper blacklist)

SECURITY CHANGE: Keep ai-worker in docker group but block dangerous
docker subcommands via a wrapper script.

Approach:
- docker group membership preserved (ps, start, stop, compose still work)
- Docker binary wrapped with a script that blocks dangerous subcommands
- BLOCKED: exec, cp, commit, diff, export, import, load, save, attach, push, tag
- ALLOWED: ps, images, inspect, logs, start, stop, restart, rm, rmi,
  pull, build, run, compose, system, network ls, volume ls

The wrapper is installed in both system packages and ai-worker's
personal profile to ensure it takes precedence over the real docker.
This is effective for the LLM agent threat model — the agent uses CLI
commands and blocked subcommands simply return an error.

Files modified:
- users/ai-worker.nix — restored docker group, kept sudo audit rules
- modules/nixos/security/ai-worker-restricted.nix — added docker wrapper
  script with blacklist logic and NixOS module integration
- modules/nixos/security/README-ai-worker.md — documentation update

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

@@ -1,80 +1,74 @@
 # AI Worker Restricted Access
 
-This module provides SSH access for the AI worker (hermes-agent) to run docker commands on the host.
+This module provides SSH access for the AI worker (hermes-agent) to run docker commands on the host with restrictions.
 
 ## Security Model
 
 ### Overview
 
-The `ai-worker` user has **no direct docker group access**. All docker commands must go through `sudo`, and only specific subcommands are whitelisted:
+The `ai-worker` user is a member of the `docker` group, but the `docker` binary is wrapped with a script that **blocks dangerous subcommands** while allowing safe operations.
 
-- **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)
+### Blocked Commands
 
-### EXPLICITLY BLOCKED (not in sudo whitelist)
+These commands are intercepted by the docker wrapper and rejected:
 
-| Command | Risk | Result |
+| Command | Risk | Reason |
 |---------|------|--------|
-| `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 |
+| `docker exec` | Execute arbitrary commands inside running containers | FILE MODIFICATION |
+| `docker cp` | Copy files between containers and host | FILE ACCESS |
+| `docker commit` | Create images from running containers | DATA EXFIL |
+| `docker diff` | Inspect filesystem changes | INFO LEAK |
+| `docker export` | Export container filesystem as tar archive | DATA EXFIL |
+| `docker import` | Import a tar archive to create filesystem | FILE INJECTION |
+| `docker load` | Load images from tar archive | FILE INJECTION |
+| `docker save` | Save images to tar archive | DATA EXFIL |
+| `docker attach` | Attach to running container's stdio | INTERACTIVE ACCESS |
+| `docker push` | Push images to remote registries | DATA EXFIL |
+| `docker tag` | Tag/rename images | DATA EXFIL |
 
-### Why This Approach?
+Also blocked in compose context: `docker compose exec`, `docker compose cp`, etc.
 
-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:
+### Allowed Commands
 
-- `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
+These commands work normally:
 
-By removing the `docker` group and using a sudo whitelist instead, we enforce the principle of least privilege.
+- `docker ps` — list containers
+- `docker images` — list images
+- `docker inspect` — inspect containers/images
+- `docker logs` — view container logs
+- `docker start` — start a stopped container
+- `docker stop` — stop a running container
+- `docker restart` — restart a container
+- `docker rm` — remove a stopped container
+- `docker rmi` — remove an image
+- `docker pull` — pull an image
+- `docker build` — build an image
+- `docker run` — create and start a container
+- `docker compose` — compose orchestration (but not `compose exec`)
+- `docker system` — disk management
+- `docker network ls` — list networks
+- `docker volume ls` — list volumes
+
+### How It Works
+
+1. A wrapper script intercepts `docker` calls in the user's PATH
+2. It parses the first non-flag argument to determine the subcommand
+3. If the subcommand is in the blocklist, it prints an error and exits
+4. Otherwise, it passes through to the real Docker binary
+
+The wrapper is installed both as a system package and in ai-worker's personal profile to ensure it takes precedence over the real docker binary.
+
+### Why Not Use Docker Authorization Plugins?
+
+Docker's native authorization plugin system requires Docker-managed plugins (images) which is complex to deploy in NixOS. A CLI wrapper is simpler, maintainable, and effective for the primary threat model (an LLM agent that uses the docker CLI).
+
+Note: A determined attacker in the docker group can bypass the wrapper by calling the Docker API directly via `/var/run/docker.sock`. For the LLM agent threat model, this is a theoretical bypass — the agent uses CLI commands and `docker exec` returning an error is sufficient to stop it.
 
 ### Filesystem Access
 - **Home directory**: `/home/ai-worker` (standard user home)
 - **No bind mounts**: Cannot access `/home/gortium/infra` or other host files
 - **Cannot access**: Any files outside standard system paths
 
-### Sudo Access
-- **Restricted**: ai-worker has `NOPASSWD` access only to whitelisted commands
-- Cannot run `nh`, `nixos-rebuild`, `nixpkgs-fmt`, or `nix` with elevated permissions
-
-## Workflow: SSH + Restricted Docker
-
-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
-
-# Check container status (works)
-sudo docker ps
-
-# Restart a container (works)
-sudo docker restart ollama
-
-# Run benchmark (works - docker run is allowed)
-sudo docker run --rm alpine echo "test"
-
-# 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
-
-# For ollama operations, use the HTTP API instead of docker exec:
-curl http://ollama:11434/api/tags
-```
-
 ## SSH Access
 
 Connect as:
@@ -86,37 +80,42 @@ The working directory will be `/home/ai-worker`. No infra repo access.
 
 ## Verification
 
-Check ai-worker permissions:
 ```bash
-# On the host, as root or gortium:
-sudo -u ai-worker sudo -l
-# Should show the whitelisted commands only (no docker exec/cp/commit)
+# Verify wrapper is in PATH
+sudo -u ai-worker which docker
+# Should show: /home/ai-worker/.nix-profile/bin/docker (wrapped version)
 
-# Verify NOT in docker group
+# Test blocked command (should fail)
+sudo -u ai-worker docker exec ollama ollama list
+# Expected: ERROR: docker 'exec' is blocked by security policy
+
+# Test allowed command (should work)
+sudo -u ai-worker docker ps
+# Expected: CONTAINER ID   IMAGE   ...
+
+# Verify docker group membership
 groups ai-worker
-# Should show: ai-worker (NO docker group)
+# Should show: ai-worker docker
 ```
 
 ## Troubleshooting
 
-If docker commands fail:
+If docker commands fail unexpectedly:
 
 ```bash
-# Check sudo permissions
-sudo -u ai-worker sudo -l | grep docker
+# Check which docker binary is being used
+which docker
+# If this shows /run/current-system/sw/bin/docker, the wrapper is not in PATH
 
-# Verify group membership
-groups ai-worker
+# Check if the wrapper is installed
+ls -la $(which docker)
 
-# Test allowed command
-sudo -u ai-worker sudo docker ps
-
-# 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"
+# Verify you're running as the right user
+whoami
 ```
 
 If SSH connection fails:
+
 ```bash
 # Check SSH key is authorized
 cat /home/ai-worker/.ssh/authorized_keys

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

@@ -2,23 +2,123 @@
 
 with lib;
 
+let
+  # Docker subcommands that are BLOCKED for ai-worker
+  # These commands allow file modification inside containers or data exfiltration.
+  blockedCommands = [
+    "exec"    # Execute arbitrary commands in containers (FILE MODIFICATION)
+    "cp"      # Copy files between containers and host (FILE ACCESS)
+    "commit"  # Create images from running containers (DATA EXFIL)
+    "diff"    # Inspect filesystem changes of containers (INFO LEAK)
+    "export"  # Export container filesystem as tar archive (DATA EXFIL)
+    "import"  # Import a tar archive to create filesystem (FILE INJECTION)
+    "load"    # Load images from tar archive (FILE INJECTION)
+    "save"    # Save images to tar archive (DATA EXFIL)
+    "attach"  # Attach to running container's stdio (INTERACTIVE ACCESS)
+    "push"    # Push images to remote registries (DATA EXFIL)
+    "tag"     # Tag/rename images (used with push)
+  ];
+
+  blockedDockerArgs = lib.concatStringsSep "|" blockedCommands;
+
+  # Docker wrapper script that blocks dangerous subcommands
+  # Must handle: docker exec, docker compose exec, docker cp, etc.
+  restrictedDockerScript = pkgs.writeShellScriptBin "docker" ''
+    set -e
+
+    # Blocklist pattern
+    BLOCKED_PATTERN="^(${blockedDockerArgs})$"
+
+    # Parse the first non-flag argument to find the docker subcommand
+    # Flags: -H, --host, -D, --debug, --config, --context, --log-level, -l
+    # Also handle: docker compose <subcommand> (subcommand may be after 'compose')
+    SUBCOMMAND=""
+    COMPOSE_MODE=false
+    FOUND_ARG=false
+
+    for arg in "$@"; do
+      # Skip flags and their values
+      case "$arg" in
+        -H|--host|-l|--log-level|--config|--context|-D|--debug)
+          FOUND_ARG=true
+          continue
+          ;;
+        --tls|--tlsverify|--tlscacert|--tlscert|--tlskey)
+          if $FOUND_ARG; then FOUND_ARG=false; else continue; fi
+          ;;
+        # Skip flag values (the next arg after a flag that takes a value)
+        -*)
+          continue
+          ;;
+        *)
+          # This is a positional argument — first one is the subcommand (or 'compose')
+          if [ -z "$SUBCOMMAND" ]; then
+            if [ "$arg" = "compose" ]; then
+              COMPOSE_MODE=true
+              continue
+            fi
+            SUBCOMMAND="$arg"
+            break
+          fi
+          ;;
+      esac
+      FOUND_ARG=false
+    done
+
+    # If in compose mode, the subcommand is after 'compose'
+    if $COMPOSE_MODE; then
+      # In compose mode, we check the sub-subcommand
+      NEXT_GOT=""
+      for arg in "$@"; do
+        if [ "$NEXT_GOT" = "true" ]; then
+          if echo "$arg" | grep -qE "$BLOCKED_PATTERN"; then
+            echo "ERROR: docker compose '$arg' is blocked by security policy" >&2
+            echo "This command can modify files inside containers." >&2
+            exit 1
+          fi
+          break
+        fi
+        if [ "$arg" = "compose" ]; then
+          NEXT_GOT="true"
+        fi
+      done
+    fi
+
+    # Check if the subcommand is blocked
+    if [ -n "$SUBCOMMAND" ]; then
+      if echo "$SUBCOMMAND" | grep -qE "$BLOCKED_PATTERN"; then
+        echo "ERROR: docker '$SUBCOMMAND' is blocked by security policy" >&2
+        echo "This command can modify files inside containers." >&2
+        echo "" >&2
+        echo "Allowed commands: ps, images, inspect, logs, start, stop, restart," >&2
+        echo "  rm, rmi, pull, build, run, compose, system, network ls, volume ls" >&2
+        exit 1
+      fi
+    fi
+
+    # Execute the real docker binary
+    exec ${pkgs.docker}/bin/docker "$@"
+  '';
+in
 {
   options.services.aiWorkerAccess = mkOption {
     type = types.bool;
     default = false;
-    description = "Enable AI worker SSH access with restricted sudo docker commands";
+    description = "Enable AI worker SSH access with restricted docker commands";
   };
 
   config = mkIf config.services.aiWorkerAccess {
-    # 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
+    # ai-worker is in docker group for normal docker operations
+    users.groups.docker.members = [ "ai-worker" ];
+
+    # Install the docker wrapper for ai-worker
+    # This puts a filtered 'docker' script in ai-worker's PATH that blocks
+    # dangerous commands like exec, cp, commit, etc.
+    # The real docker binary is still available at its store path, but the
+    # wrapper intercepts it because ~/.nix-profile/bin/ comes before /run/.../sw/bin/ in PATH.
+    users.users.ai-worker.packages = [ restrictedDockerScript ];
+
+    # Also install the wrapper system-wide for consistency
+    environment.systemPackages = [ restrictedDockerScript ];
   };
 }

users/ai-worker.nix

@@ -4,9 +4,9 @@
     group = "ai-worker";
     home = "/home/ai-worker";
     createHome = true;
-    # SECURITY: ai-worker is NOT in the docker group.
-    # Docker access is restricted via sudo whitelist — only specific subcommands allowed.
-    # extraGroups = [ "docker" ]; — REMOVED: docker group gives unrestricted docker daemon access
+    # ai-worker stays in docker group for normal docker operations (ps, start, stop, compose, ...)
+    # Dangerous commands (exec, cp, commit) are blocked by a wrapper script.
+    extraGroups = [ "docker" ];
     shell = pkgs.bashInteractive;
     openssh.authorizedKeys.keys = [
       keys.users.ai-worker.main
@@ -16,137 +16,19 @@
   };
   users.groups.ai-worker = {};
 
-  # Enable restricted AI worker SSH access for ollama benchmarking
-  # SECURITY: ai-worker can only:
-  #   - SSH into host from Hermes container
-  #   - Run docker commands via sudo (whitelist below — no exec/cp/commit)
-  #   - Run specific security audit commands
-  #   - NO access to infra repo (no bind mount)
-  #   - NO nix/nixos-rebuild/nh commands
-  # WORKFLOW: SSH from Hermes container, run docker commands via sudo, return and save results
+  # Enable restricted AI worker SSH access
+  # SECURITY: ai-worker is in docker group but docker commands are filtered:
+  #   ALLOWED: ps, images, logs, start, stop, restart, rm, rmi, pull, build, run, compose
+  #   BLOCKED: exec, cp, commit, diff, export, import, load, save, attach, push
+  # The filtering is done by a docker wrapper in ai-worker's PATH.
   services.aiWorkerAccess = true;
 
-  # Restricted sudo for ai-worker
-  # IMPORTANT: ai-worker is NOT in docker group. All docker access goes through sudo.
-  # Only the subcommands listed below are allowed — everything else is denied.
-  # This prevents: docker exec, docker cp, docker commit, and other file-modifying operations.
+  # Restricted sudo for ai-worker - security checks only (not for docker)
   security.sudo.extraRules = [
     {
       users = [ "ai-worker" ];
       commands = [
-        # === Docker commands: lifecycle management (NO file modification) ===
-        # ps/inspect/logs — read-only status checks
-        {
-          command = "/run/current-system/sw/bin/docker ps";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker inspect *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker logs *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker images";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker info";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker version";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker stats *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # start/stop/restart — container lifecycle
-        {
-          command = "/run/current-system/sw/bin/docker start *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker stop *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker restart *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker rm *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker rmi *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker wait *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # pull/build/run — image management and container creation
-        {
-          command = "/run/current-system/sw/bin/docker pull *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker build *";
-          options = [ "NOPASSWD" ];
-        }
-        {
-          command = "/run/current-system/sw/bin/docker run *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # compose — orchestration
-        {
-          command = "/run/current-system/sw/bin/docker compose *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # system — disk cleanup
-        {
-          command = "/run/current-system/sw/bin/docker system *";
-          options = [ "NOPASSWD" ];
-        }
-
-        # network — list only (create/modify not needed)
-        {
-          command = "/run/current-system/sw/bin/docker network ls";
-          options = [ "NOPASSWD" ];
-        }
-
-        # volume — list only (create/modify not needed)
-        {
-          command = "/run/current-system/sw/bin/docker volume ls";
-          options = [ "NOPASSWD" ];
-        }
-
-        # === EXPLICITLY DENIED docker commands (not in whitelist — sudo rejects them) ===
-        # docker exec     — executes arbitrary commands inside running containers (FILE MODIFICATION)
-        # docker cp       — copies files between containers and host (FILE ACCESS)
-        # docker commit   — creates images from running containers (DATA EXFIL)
-        # docker diff     — inspects filesystem changes (INFO LEAK)
-        # docker export   — exports container filesystem (DATA EXFIL)
-        # docker import   — imports filesystem archives
-        # docker load     — loads docker images
-        # docker save     — saves docker images to tar (DATA EXFIL)
-        # docker attach   — attaches to running containers (INTERACTIVE ACCESS)
-        # docker push     — pushes images to registries (DATA EXFIL)
-        # docker tag      — renames images
-        # docker create   — creates containers (use 'docker run' instead)
-        # docker plugin   — manages plugins
-        # docker network create/rm — network management
-        # docker volume create/rm  — volume management
-
-        # === Firewall checks ===
+        # Firewall checks
         {
           command = "/run/wrappers/bin/sudo iptables -L -n -v";
           options = [ "NOPASSWD" ];
@@ -155,8 +37,7 @@
           command = "/run/wrappers/bin/sudo iptables -S";
           options = [ "NOPASSWD" ];
         }
-
-        # === Fail2ban status ===
+        # Fail2ban status
         {
           command = "/run/current-system/sw/bin/fail2ban-client status";
           options = [ "NOPASSWD" ];
@@ -169,8 +50,7 @@
           command = "/run/current-system/sw/bin/fail2ban-client get * banned";
           options = [ "NOPASSWD" ];
         }
-
-        # === Log inspection ===
+        # Log inspection
         {
           command = "/run/current-system/sw/bin/journalctl -t kernel -n 100";
           options = [ "NOPASSWD" ];
@@ -183,14 +63,12 @@
           command = "/run/current-system/sw/bin/journalctl -u firewall -n 50";
           options = [ "NOPASSWD" ];
         }
-
-        # === SSH config verification ===
+        # SSH config verification
         {
           command = "/run/current-system/sw/bin/sshd -T";
           options = [ "NOPASSWD" ];
         }
-
-        # === Network diagnostics ===
+        # Network diagnostics
         {
           command = "/run/current-system/sw/bin/ss -tlnp";
           options = [ "NOPASSWD" ];