mcp-bash

#!/usr/bin/env bash # UI Resource Provider for mcp-bash # Serves HTML content from ui:// URIs per MCP Apps specification (SEP-1865) # # URI formats: # ui://resource-name (authority only) # ui://server-name/path (authority + path) # # Exit codes: # 0 = success (HTML content on stdout) # 2 = access denied # 3 = not found # 4 = invalid URI scheme set -euo pipefail # Source UI libraries for template support (provider runs as subprocess) if [ -n "${MCPBASH_HOME:-}" ]; then # Set required environment variables if not already set : "${MCPBASH_STATE_DIR:=${MCPBASH_PROJECT_ROOT:-.}/.mcp-bash}" : "${MCPBASH_REGISTRY_DIR:=${MCPBASH_STATE_DIR}}" : "${MCPBASH_TOOLS_DIR:=${MCPBASH_PROJECT_ROOT:-}/tools}" : "${MCPBASH_UI_DIR:=${MCPBASH_PROJECT_ROOT:-}/ui}" export MCPBASH_STATE_DIR MCPBASH_REGISTRY_DIR MCPBASH_TOOLS_DIR MCPBASH_UI_DIR # Source JSON tool detection first if [ -f "${MCPBASH_HOME}/lib/json.sh" ]; then # shellcheck source=/dev/null . "${MCPBASH_HOME}/lib/json.sh" mcp_json_detect_tool >/dev/null 2>&1 || true fi # Source UI library if [ -f "${MCPBASH_HOME}/lib/ui.sh" ]; then # shellcheck source=/dev/null . "${MCPBASH_HOME}/lib/ui.sh" fi # Source UI templates library if [ -f "${MCPBASH_HOME}/lib/ui-templates.sh" ]; then # shellcheck source=/dev/null . "${MCPBASH_HOME}/lib/ui-templates.sh" fi fi uri="${1:-}" # Validate URI scheme if [[ ! "${uri}" =~ ^ui:// ]]; then printf '%s\n' "Invalid URI scheme: expected ui://" >&2 exit 4 fi # Extract resource name, handling both formats: # - ui://weather-dashboard -> weather-dashboard (authority only) # - ui://server/path/to/app -> path/to/app (authority + path) without_scheme="${uri#ui://}" resource_name="" if [[ "${without_scheme}" == */* ]]; then # Has path component - extract everything after first / resource_name="${without_scheme#*/}" else # Authority only - use as resource name resource_name="${without_scheme}" fi if [ -z "${resource_name}" ]; then printf '%s\n' "Empty resource name in URI: ${uri}" >&2 exit 3 fi # Prevent directory traversal attacks case "${resource_name}" in *..* | /*) printf '%s\n' "Invalid resource name: ${resource_name}" >&2 exit 2 ;; esac # Resolve resource to filesystem path # Priority order: # 1. tools/NAME/ui/index.html (tool-specific UI) # 2. ui/NAME/index.html (standalone UI) # 3. Registry-defined custom paths (handled by lib/ui.sh after Phase 2) mcp_ui_resolve_path() { local name="$1" local tools_dir="${MCPBASH_TOOLS_DIR:-${MCPBASH_PROJECT_ROOT:-}/tools}" local ui_dir="${MCPBASH_UI_DIR:-${MCPBASH_PROJECT_ROOT:-}/ui}" # For nested paths like "path/to/app", extract path after first component local sub_path="${name#*/}" [ "${sub_path}" = "${name}" ] && sub_path="" # Priority 1: Tool-specific UI (single-level names only) if [ -z "${sub_path}" ]; then local tool_ui="${tools_dir}/${name}/ui/index.html" if [ -f "${tool_ui}" ]; then printf '%s' "${tool_ui}" return 0 fi fi # Priority 2: Standalone UI directory local standalone_ui="${ui_dir}/${name}/index.html" if [ -f "${standalone_ui}" ]; then printf '%s' "${standalone_ui}" return 0 fi # Priority 3: Check registry for custom paths (if lib/ui.sh is loaded) if declare -F mcp_ui_get_path_from_registry >/dev/null 2>&1; then local registry_path if registry_path="$(mcp_ui_get_path_from_registry "${name}")"; then if [ -n "${registry_path}" ] && [ -f "${registry_path}" ]; then printf '%s' "${registry_path}" return 0 fi fi fi return 1 } # Try to get content via mcp_ui_get_content (supports templates) if declare -F mcp_ui_get_content >/dev/null 2>&1; then if content="$(mcp_ui_get_content "${resource_name}" 2>/dev/null)"; then printf '%s' "${content}" exit 0 fi fi # Fallback: resolve to static file html_path="" if ! html_path="$(mcp_ui_resolve_path "${resource_name}")"; then printf '%s\n' "UI resource not found: ${resource_name}" >&2 exit 3 fi if [ -z "${html_path}" ] || [ ! -f "${html_path}" ]; then printf '%s\n' "UI resource not found: ${resource_name}" >&2 exit 3 fi # Reject symlinks (security: prevent path swapping attacks) if [ -L "${html_path}" ]; then printf '%s\n' "Symlinks not allowed for UI resources" >&2 exit 2 fi # Check size limits if configured max_size="${MCPBASH_MAX_UI_RESOURCE_BYTES:-1048576}" # Default 1MB if command -v stat >/dev/null 2>&1; then # Portable stat: try GNU format first, fall back to BSD format file_size="" if file_size="$(stat -c%s "${html_path}" 2>/dev/null)"; then : # GNU stat worked elif file_size="$(stat -f%z "${html_path}" 2>/dev/null)"; then : # BSD stat worked fi if [ -n "${file_size}" ] && [ "${file_size}" -gt "${max_size}" ]; then printf '%s\n' "UI resource too large: ${file_size} bytes (max: ${max_size})" >&2 exit 3 fi fi # Output HTML content # Use fd 3 to prevent race conditions (same pattern as file provider) if ! exec 3<"${html_path}"; then exit 3 fi # Final symlink check after open (TOCTOU protection) if [ -L "${html_path}" ]; then exec 3<&- exit 2 fi cat <&3 exec 3<&-