fix: inject NAT rules into child containers to prevent proxy bypass

containers/agent/docker-wrapper.sh

@@ -1,11 +1,132 @@
 #!/bin/bash
 # Docker wrapper that injects --network awf-net and proxy env vars to all docker run commands
 # This ensures spawned containers are subject to the same firewall rules
+#
+# Security: This wrapper also injects NAT rules into child containers to prevent proxy bypass.
+# Applications that ignore HTTP_PROXY environment variables will still have their traffic
+# redirected to Squid via iptables NAT rules.
 
 NETWORK_NAME="awf-net"
 SQUID_PROXY="http://172.30.0.10:3128"
+SQUID_IP="172.30.0.10"
+SQUID_PORT="3128"
 LOG_FILE="/tmp/docker-wrapper.log"
 
+# NAT setup script that will be injected into child containers
+# This script redirects HTTP/HTTPS traffic to Squid proxy using iptables
+# It's designed to be minimal and work with busybox/alpine shells
+# Note: The script ends with a semicolon to ensure proper command separation
+NAT_SETUP_SCRIPT='if command -v iptables >/dev/null 2>&1; then iptables -t nat -F OUTPUT 2>/dev/null || true; iptables -t nat -A OUTPUT -o lo -j RETURN; iptables -t nat -A OUTPUT -d 127.0.0.0/8 -j RETURN; iptables -t nat -A OUTPUT -p udp -d 127.0.0.11 --dport 53 -j RETURN; iptables -t nat -A OUTPUT -p tcp -d 127.0.0.11 --dport 53 -j RETURN; iptables -t nat -A OUTPUT -p udp -d 8.8.8.8 --dport 53 -j RETURN; iptables -t nat -A OUTPUT -p tcp -d 8.8.8.8 --dport 53 -j RETURN; iptables -t nat -A OUTPUT -p udp -d 8.8.4.4 --dport 53 -j RETURN; iptables -t nat -A OUTPUT -p tcp -d 8.8.4.4 --dport 53 -j RETURN; iptables -t nat -A OUTPUT -d 8.8.8.8 -j RETURN; iptables -t nat -A OUTPUT -d 8.8.4.4 -j RETURN; iptables -t nat -A OUTPUT -d '"$SQUID_IP"' -j RETURN; iptables -t nat -A OUTPUT -p tcp --dport 80 -j DNAT --to-destination '"$SQUID_IP:$SQUID_PORT"'; iptables -t nat -A OUTPUT -p tcp --dport 443 -j DNAT --to-destination '"$SQUID_IP:$SQUID_PORT"'; fi; '
+
+# Function to escape a command argument for use in sh -c
+# Uses printf %q for robust escaping of all shell metacharacters
+escape_for_shell() {
+  local arg="$1"
+  # Use printf %q for proper shell escaping
+  printf '%q' "$arg"
+}
+
+# Function to build escaped command string from array of arguments
+build_escaped_cmd() {
+  local escaped=""
+  for arg in "$@"; do
+    if [ -n "$escaped" ]; then
+      escaped="$escaped "
+    fi
+    escaped="$escaped$(escape_for_shell "$arg")"
+  done
+  echo "$escaped"
+}
+
+# Function to check if an argument is a Docker option that takes a value
+is_docker_option_with_value() {
+  local arg="$1"
+  case "$arg" in
+    -e|--env|-l|--label|-v|--volume|-p|--publish|--name|--hostname|\
+    --user|-u|--workdir|-w|--mount|--network-alias|--dns|--dns-search|\
+    --dns-option|--cpus|--memory|-m|--memory-swap|--memory-reservation|\
+    --kernel-memory|--cpu-shares|--cpu-period|--cpu-quota|--cpuset-cpus|\
+    --cpuset-mems|--blkio-weight|--device|--device-cgroup-rule|\
+    --device-read-bps|--device-read-iops|--device-write-bps|\
+    --device-write-iops|--cap-add|--cap-drop|--security-opt|--ulimit|\
+    --sysctl|--restart|--stop-signal|--stop-timeout|--health-cmd|\
+    --health-interval|--health-retries|--health-start-period|\
+    --health-timeout|--log-driver|--log-opt|--storage-opt|\
+    --tmpfs|--ipc|--pid|--userns|--uts|--runtime|--isolation|\
+    --platform|--pull|--shm-size|--group-add|--cidfile|--cgroup-parent|\
+    --init|--read-only|--gpus|--link|--link-local-ip|--ip|--ip6|\
+    --mac-address|--expose|--domainname|--add-host|--annotation)
+      return 0
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+# Function to parse docker run arguments and extract options, image, and command
+# Sets global variables: PARSED_DOCKER_OPTS, PARSED_IMAGE, PARSED_USER_CMD
+parse_docker_run_args() {
+  local include_network="$1"
+  shift
+
+  PARSED_DOCKER_OPTS=()
+  PARSED_USER_CMD=()
+  PARSED_IMAGE=""
+  local parsing_opts=true
+  local skip_next=false
+
+  for arg in "$@"; do
+    if [ "$skip_next" = true ]; then
+      PARSED_DOCKER_OPTS+=("$arg")
+      skip_next=false
+      continue
+    fi
+
+    if [ "$parsing_opts" = true ]; then
+      # Check for --entrypoint flag (we track this but don't use it currently)
+      if [ "$arg" = "--entrypoint" ]; then
+        PARSED_DOCKER_OPTS+=("$arg")
+        skip_next=true
+        continue
+      fi
+      if [[ "$arg" == "--entrypoint="* ]]; then
+        PARSED_DOCKER_OPTS+=("$arg")
+        continue
+      fi
+
+      # Check if it's a Docker option that takes a value
+      if is_docker_option_with_value "$arg"; then
+        PARSED_DOCKER_OPTS+=("$arg")
+        skip_next=true
+        continue
+      fi
+
+      # Handle --network and --net specially if we need to include them
+      if [ "$include_network" = "true" ]; then
+        if [ "$arg" = "--network" ] || [ "$arg" = "--net" ]; then
+          PARSED_DOCKER_OPTS+=("$arg")
+          skip_next=true
+          continue
+        fi
+      fi
+
+      # Docker options that are flags (no value) or have = format
+      if [[ "$arg" == -* ]]; then
+        PARSED_DOCKER_OPTS+=("$arg")
+        continue
+      fi
+
+      # First non-option argument is the image name
+      PARSED_IMAGE="$arg"
+      parsing_opts=false
+    else
+      # Everything after the image name is the command
+      PARSED_USER_CMD+=("$arg")
+    fi
+  done
+}
+
 # Log all docker commands
 echo "[$(date -Iseconds)] WRAPPER CALLED: docker $@" >> "$LOG_FILE"
 
@@ -78,23 +199,107 @@ if [ "$1" = "run" ]; then
     exit 1
   fi
 
-  # If --network not specified, inject it along with proxy environment variables
+  # If --network not specified, inject it along with proxy environment variables and NAT rules
   if [ "$has_network" = false ]; then
-    # Build new args: docker run --network awf-net -e HTTP_PROXY -e HTTPS_PROXY <rest of args>
     shift # remove 'run'
-    echo "[$(date -Iseconds)] INJECTING --network $NETWORK_NAME and proxy env vars" >> "$LOG_FILE"
-    exec /usr/bin/docker-real run \
-      --network "$NETWORK_NAME" \
-      -e HTTP_PROXY="$SQUID_PROXY" \
-      -e HTTPS_PROXY="$SQUID_PROXY" \
-      -e http_proxy="$SQUID_PROXY" \
-      -e https_proxy="$SQUID_PROXY" \
-      "$@"
+    echo "[$(date -Iseconds)] INJECTING --network $NETWORK_NAME, proxy env vars, and NAT rules" >> "$LOG_FILE"
+
+    # Parse docker run arguments
+    parse_docker_run_args "false" "$@"
+
+    # If no image was found, just pass through
+    if [ -z "$PARSED_IMAGE" ]; then
+      echo "[$(date -Iseconds)] ERROR: Could not find image name, passing through" >> "$LOG_FILE"
+      exec /usr/bin/docker-real run "$@"
+    fi
+
+    echo "[$(date -Iseconds)] Image: $PARSED_IMAGE, Command: ${PARSED_USER_CMD[*]:-<default>}" >> "$LOG_FILE"
+
+    # Build the wrapped command that sets up NAT rules then runs the user's command
+    if [ ${#PARSED_USER_CMD[@]} -gt 0 ]; then
+      # User specified a command - wrap it with NAT setup
+      escaped_cmd=$(build_escaped_cmd "${PARSED_USER_CMD[@]}")
+      wrapped_cmd="${NAT_SETUP_SCRIPT}exec ${escaped_cmd}"
+
+      # Execute with NAT wrapper
+      exec /usr/bin/docker-real run \
+        --network "$NETWORK_NAME" \
+        --cap-add NET_ADMIN \
+        -e HTTP_PROXY="$SQUID_PROXY" \
+        -e HTTPS_PROXY="$SQUID_PROXY" \
+        -e http_proxy="$SQUID_PROXY" \
+        -e https_proxy="$SQUID_PROXY" \
+        -e SQUID_PROXY_IP="$SQUID_IP" \
+        -e SQUID_PROXY_PORT="$SQUID_PORT" \
+        "${PARSED_DOCKER_OPTS[@]}" \
+        --entrypoint sh \
+        "$PARSED_IMAGE" \
+        -c "$wrapped_cmd"
+    else
+      # No user command - can't easily wrap the default entrypoint
+      echo "[$(date -Iseconds)] WARNING: No command specified, NAT rules may not apply to default entrypoint" >> "$LOG_FILE"
+      exec /usr/bin/docker-real run \
+        --network "$NETWORK_NAME" \
+        --cap-add NET_ADMIN \
+        -e HTTP_PROXY="$SQUID_PROXY" \
+        -e HTTPS_PROXY="$SQUID_PROXY" \
+        -e http_proxy="$SQUID_PROXY" \
+        -e https_proxy="$SQUID_PROXY" \
+        -e SQUID_PROXY_IP="$SQUID_IP" \
+        -e SQUID_PROXY_PORT="$SQUID_PORT" \
+        "${PARSED_DOCKER_OPTS[@]}" \
+        "$PARSED_IMAGE"
+    fi
   else
-    echo "[$(date -Iseconds)] --network $network_value already specified, passing through" >> "$LOG_FILE"
+    # Network is already specified (and not host) - still inject NAT rules and proxy env vars
+    echo "[$(date -Iseconds)] --network $network_value already specified, injecting NAT rules and proxy env vars" >> "$LOG_FILE"
+
+    shift # remove 'run'
+
+    # Parse docker run arguments (include network options in docker_opts)
+    parse_docker_run_args "true" "$@"
+
+    # If no image was found, just pass through
+    if [ -z "$PARSED_IMAGE" ]; then
+      echo "[$(date -Iseconds)] ERROR: Could not find image name, passing through" >> "$LOG_FILE"
+      exec /usr/bin/docker-real run "$@"
+    fi
+
+    echo "[$(date -Iseconds)] Image: $PARSED_IMAGE, Command: ${PARSED_USER_CMD[*]:-<default>}" >> "$LOG_FILE"
+
+    # Build the wrapped command
+    if [ ${#PARSED_USER_CMD[@]} -gt 0 ]; then
+      escaped_cmd=$(build_escaped_cmd "${PARSED_USER_CMD[@]}")
+      wrapped_cmd="${NAT_SETUP_SCRIPT}exec ${escaped_cmd}"
+
+      exec /usr/bin/docker-real run \
+        --cap-add NET_ADMIN \
+        -e HTTP_PROXY="$SQUID_PROXY" \
+        -e HTTPS_PROXY="$SQUID_PROXY" \
+        -e http_proxy="$SQUID_PROXY" \
+        -e https_proxy="$SQUID_PROXY" \
+        -e SQUID_PROXY_IP="$SQUID_IP" \
+        -e SQUID_PROXY_PORT="$SQUID_PORT" \
+        "${PARSED_DOCKER_OPTS[@]}" \
+        --entrypoint sh \
+        "$PARSED_IMAGE" \
+        -c "$wrapped_cmd"
+    else
+      # No command specified - pass through with proxy env vars
+      exec /usr/bin/docker-real run \
+        --cap-add NET_ADMIN \
+        -e HTTP_PROXY="$SQUID_PROXY" \
+        -e HTTPS_PROXY="$SQUID_PROXY" \
+        -e http_proxy="$SQUID_PROXY" \
+        -e https_proxy="$SQUID_PROXY" \
+        -e SQUID_PROXY_IP="$SQUID_IP" \
+        -e SQUID_PROXY_PORT="$SQUID_PORT" \
+        "${PARSED_DOCKER_OPTS[@]}" \
+        "$PARSED_IMAGE"
+    fi
   fi
 fi
 
-# For all other commands or if --network already specified, pass through
+# For all other commands (not docker run), pass through
 echo "[$(date -Iseconds)] PASSING THROUGH: /usr/bin/docker-real $@" >> "$LOG_FILE"
 exec /usr/bin/docker-real "$@"

tests/integration/docker-egress.test.ts

@@ -346,4 +346,84 @@ describe('Docker Container Egress Tests', () => {
       expect(result).toFail();
     }, 120000);
   });
+
+  describe('8M. NAT rules in child containers (proxy bypass prevention)', () => {
+    test('Container: NAT rules applied - blocks traffic even when proxy env vars are ignored', async () => {
+      // This test verifies that child containers have NAT rules applied via docker-wrapper.sh
+      // Even if an application ignores HTTP_PROXY env vars, traffic is still redirected to Squid
+      const result = await runner.runWithSudo(
+        `docker run --rm alpine:latest sh -c 'apk add --no-cache curl iptables >/dev/null 2>&1 && unset HTTP_PROXY HTTPS_PROXY http_proxy https_proxy && curl -f https://example.com --max-time 10'`,
+        {
+          allowDomains: ['github.com'],
+          logLevel: 'warn',
+          timeout: 60000,
+        }
+      );
+
+      // Should fail because NAT rules redirect traffic to Squid which blocks example.com
+      expect(result).toFail();
+    }, 180000);
+
+    test('Container: NAT rules applied - allows whitelisted domains even when proxy env vars are ignored', async () => {
+      // Verify that allowed domains still work even when proxy env vars are unset
+      const result = await runner.runWithSudo(
+        `docker run --rm alpine:latest sh -c 'apk add --no-cache curl iptables >/dev/null 2>&1 && unset HTTP_PROXY HTTPS_PROXY http_proxy https_proxy && curl -fsS https://api.github.com/zen --max-time 30'`,
+        {
+          allowDomains: ['api.github.com'],
+          logLevel: 'warn',
+          timeout: 60000,
+        }
+      );
+
+      // Should succeed because NAT rules redirect to Squid which allows api.github.com
+      expect(result).toSucceed();
+    }, 180000);
+
+    test('Container: wget --no-proxy blocked by NAT rules', async () => {
+      // wget --no-proxy explicitly ignores proxy settings, but NAT rules should still work
+      const result = await runner.runWithSudo(
+        `docker run --rm alpine:latest sh -c 'apk add --no-cache wget iptables >/dev/null 2>&1 && wget --no-proxy -q -O- https://example.com --timeout=10'`,
+        {
+          allowDomains: ['github.com'],
+          logLevel: 'warn',
+          timeout: 60000,
+        }
+      );
+
+      // Should fail because NAT rules redirect traffic to Squid regardless of --no-proxy
+      expect(result).toFail();
+    }, 180000);
+
+    test('Container: Verify NAT rules are present in child container', async () => {
+      // Directly check if NAT rules are applied in child container
+      const result = await runner.runWithSudo(
+        `docker run --rm alpine:latest sh -c 'apk add --no-cache iptables >/dev/null 2>&1 && iptables -t nat -L OUTPUT -n 2>/dev/null | grep DNAT || echo "No NAT rules"'`,
+        {
+          allowDomains: ['github.com'],
+          logLevel: 'warn',
+          timeout: 60000,
+        }
+      );
+
+      // Should show DNAT rules pointing to Squid
+      expect(result).toSucceed();
+      expect(result.stdout).toContain('DNAT');
+      expect(result.stdout).toContain('172.30.0.10:3128');
+    }, 180000);
+
+    test('Container: Images without iptables still work via HTTP_PROXY', async () => {
+      // Containers without iptables should still be able to access allowed domains via HTTP_PROXY
+      const result = await runner.runWithSudo(
+        'docker run --rm curlimages/curl:latest -fsS https://api.github.com/zen',
+        {
+          allowDomains: ['api.github.com'],
+          logLevel: 'warn',
+          timeout: 30000,
+        }
+      );
+
+      // Should succeed via HTTP_PROXY (NAT rules won't apply without iptables)
+      expect(result).toSucceed();
+    }, 120000);
+  });
 });