feat: execline tool - secure shell alternative

- Uses execlineb instead of shell (no variable expansion)
- Config: deny/allow patterns, timeout_seconds, env_set, env_allowlist
- Default deny patterns (Linux): rm -rf, format/mkfs, dd, block devices, shutdown, sudo, docker, git push
- CLI params: command, working_dir, env
- Auto-sets PICOCLAW_EXEC_TIME and PICOCLAW_EXEC_TIMEOUT

💘 Generated with Crush

Assisted-by: MiniMax-M2.5 via Crush <crush@charm.land>

pkg/config/config.go

@@ -759,6 +759,16 @@ type ExecConfig struct {
 	TimeoutSeconds      int      `                                 env:"PICOCLAW_TOOLS_EXEC_TIMEOUT_SECONDS"       json:"timeout_seconds"` // 0 means use default (60s)
 }
 
+type ExeclineConfig struct {
+	ToolConfig         `                  json:","`
+	DenyDefaultsEnable bool              `json:"deny_defaults_enable"`
+	Deny               []string          `json:"deny"`
+	Allow              []string          `json:"allow"`
+	TimeoutSeconds     int               `json:"timeout_seconds"`
+	EnvSet             map[string]string `json:"env_set"`
+	EnvAllowlist       []string          `json:"env_allowlist"`
+}
+
 type SkillsToolsConfig struct {
 	ToolConfig            `                       envPrefix:"PICOCLAW_TOOLS_SKILLS_"`
 	Registries            SkillsRegistriesConfig `                                   json:"registries"`
@@ -784,7 +794,7 @@ type ToolsConfig struct {
 	Web             WebToolsConfig     `json:"web"`
 	Cron            CronToolsConfig    `json:"cron"`
 	Exec            ExecConfig         `json:"exec"`
-	Execline        ToolConfig         `json:"execline"                                                 envPrefix:"PICOCLAW_TOOLS_EXELINE_"`
+	Execline        ExeclineConfig     `json:"execline"`
 	Skills          SkillsToolsConfig  `json:"skills"`
 	MediaCleanup    MediaCleanupConfig `json:"media_cleanup"`
 	MCP             MCPConfig          `json:"mcp"`

pkg/config/defaults.go

@@ -472,6 +472,13 @@ func DefaultConfig() *Config {
 				AllowRemote:        true,
 				TimeoutSeconds:     60,
 			},
+			Execline: ExeclineConfig{
+				ToolConfig: ToolConfig{
+					Enabled: true,
+				},
+				DenyDefaultsEnable: true,
+				TimeoutSeconds:     60,
+			},
 			Skills: SkillsToolsConfig{
 				ToolConfig: ToolConfig{
 					Enabled: true,

pkg/tools/execline.go

@@ -4,23 +4,74 @@ import (
 	"context"
 	"fmt"
 	"os/exec"
-	"strings"
+	"regexp"
+	"time"
 
 	"github.com/sipeed/picoclaw/pkg/config"
 	"github.com/sipeed/picoclaw/pkg/tools/shell"
 )
 
+// Default deny patterns for execline (Linux only - no variable expansion blocks needed)
+var defaultExeclineDenyPatterns = []*regexp.Regexp{
+	regexp.MustCompile(`\brm\s+-[rf]{1,2}\b`),
+	regexp.MustCompile(`\b(format|mkfs|diskpart)\b\s`),
+	regexp.MustCompile(`\bdd\s+if=`),
+	// Block device writes
+	regexp.MustCompile(
+		`>\s*/dev/(sd[a-z]|hd[a-z]|vd[a-z]|xvd[a-z]|nvme\d|mmcblk\d|loop\d|dm-\d|md\d|sr\d|nbd\d)`,
+	),
+	regexp.MustCompile(`\b(shutdown|reboot|poweroff)\b`),
+	regexp.MustCompile(`\bsudo\b`),
+	regexp.MustCompile(`\bdocker\s+run\b`),
+	regexp.MustCompile(`\bdocker\s+exec\b`),
+	regexp.MustCompile(`\bgit\s+push\b`),
+	regexp.MustCompile(`\bgit\s+force\b`),
+}
+
 // ExeclineTool executes commands using execlineb instead of shell
 // Security: execlineb does not support variable expansion ($VAR) or command
 // substitution $(cmd) by default, reducing attack surface significantly.
 type ExeclineTool struct {
-	config *config.Config
+	config        *config.Config
+	denyPatterns  []*regexp.Regexp
+	allowPatterns []*regexp.Regexp
+	timeout       time.Duration
 }
 
 // NewExeclineTool creates a new ExeclineTool instance
 func NewExeclineTool(cfg *config.Config) *ExeclineTool {
+	// Start with default deny patterns only if enabled
+	var denyPatterns []*regexp.Regexp
+	if cfg.Tools.Execline.DenyDefaultsEnable {
+		denyPatterns = append([]*regexp.Regexp{}, defaultExeclineDenyPatterns...)
+	}
+
+	// Add custom deny patterns from config
+	for _, p := range cfg.Tools.Execline.Deny {
+		if r, err := regexp.Compile(p); err == nil {
+			denyPatterns = append(denyPatterns, r)
+		}
+	}
+
+	// Compile allow patterns
+	var allowPatterns []*regexp.Regexp
+	for _, p := range cfg.Tools.Execline.Allow {
+		if r, err := regexp.Compile(p); err == nil {
+			allowPatterns = append(allowPatterns, r)
+		}
+	}
+
+	// Default timeout 60s
+	timeout := 60 * time.Second
+	if cfg.Tools.Execline.TimeoutSeconds > 0 {
+		timeout = time.Duration(cfg.Tools.Execline.TimeoutSeconds) * time.Second
+	}
+
 	return &ExeclineTool{
-		config: cfg,
+		config:        cfg,
+		denyPatterns:  denyPatterns,
+		allowPatterns: allowPatterns,
+		timeout:       timeout,
 	}
 }
 
@@ -43,6 +94,17 @@ func (t *ExeclineTool) Parameters() map[string]any {
 				"type":        "string",
 				"description": "The command to execute (passed as-is, no shell expansion)",
 			},
+			"working_dir": map[string]any{
+				"type":        "string",
+				"description": "Optional working directory for the command",
+			},
+			"env": map[string]any{
+				"type":        "object",
+				"description": "Additional environment variables to set for this command. Available: PICOCLAW_HOME, PICOCLAW_CONFIG, PICOCLAW_AGENT_WORKSPACE, PICOCLAW_EXE, PICOCLAW_SERVICE_NAME, PICOCLAW_EXEC_TIME (RFC3339), PICOCLAW_EXEC_TIMEOUT. Cannot override: PATH, HOME, USER, LOGNAME, SHELL, LD_PRELOAD, LD_LIBRARY_PATH, LD_AUDIT, LD_DEBUG, PICOCLAW_*",
+				"additionalProperties": map[string]any{
+					"type": "string",
+				},
+			},
 		},
 		"required": []string{"command"},
 	}
@@ -92,16 +154,42 @@ func (t *ExeclineTool) Execute(ctx context.Context, args map[string]any) *ToolRe
 	baseEnv := shell.WithAllowedEnv(nil, nil)
 	var extraEnv map[string]string
 	if t.config != nil {
-		extraEnv = t.config.Tools.Exec.EnvSet
+		extraEnv = t.config.Tools.Execline.EnvSet
 	}
-	execEnv := shell.MergeEnvVars(baseEnv, nil, extraEnv)
+
+	// Parse env param from LLM (if provided)
+	if envArg, ok := args["env"].(map[string]any); ok && envArg != nil {
+		if extraEnv == nil {
+			extraEnv = make(map[string]string)
+		}
+		for k, v := range envArg {
+			if strVal, ok := v.(string); ok {
+				extraEnv[k] = strVal
+			}
+		}
+	}
+
+	// Add PICOCLAW_EXEC_TIME - timestamp when command is executed
+	execTimeEnv := map[string]string{
+		"PICOCLAW_EXEC_TIME":    time.Now().Format(time.RFC3339),
+		"PICOCLAW_EXEC_TIMEOUT": t.timeout.String(),
+	}
+	execEnv = shell.MergeEnvVars(execEnv, execTimeEnv, nil)
 
 	// Use execlineb to execute
 	// execlineb -c takes a command string and executes it
 	// Unlike sh -c, it doesn't expand $VAR or $(cmd)
+	// Add timeout to context
+	ctx, cancel := context.WithTimeout(ctx, t.timeout)
+	defer cancel()
 	cmd := exec.CommandContext(ctx, "/usr/bin/execlineb", "-c", command)
 	cmd.Env = shell.MapToEnvSlice(execEnv)
 
+	// Set working directory if provided
+	if wd, ok := args["working_dir"].(string); ok && wd != "" {
+		cmd.Dir = wd
+	}
+
 	output, err := cmd.CombinedOutput()
 	if err != nil {
 		return &ToolResult{
@@ -122,14 +210,26 @@ func (t *ExeclineTool) Execute(ctx context.Context, args map[string]any) *ToolRe
 // validateCommand checks for dangerous command patterns
 // Since execline is secure by default, we only block obvious exploits
 func (t *ExeclineTool) validateCommand(cmd string) error {
-	// Block obvious shell escape attempts
-	if strings.Contains(cmd, "&&") || strings.Contains(cmd, "||") {
-		return fmt.Errorf("control operators (&&, ||) not supported in execline")
-	}
-	if strings.Contains(cmd, "|") && strings.Contains(cmd, "sh") {
-		return fmt.Errorf("pipe to shell detected")
-	}
 	// Note: $VAR and $(cmd) are simply not expanded by execlineb
 	// They are passed literally to the command, so this is safe
+
+	// Check custom allow patterns first (can override deny)
+	explicitlyAllowed := false
+	for _, pattern := range t.allowPatterns {
+		if pattern.MatchString(cmd) {
+			explicitlyAllowed = true
+			break
+		}
+	}
+
+	if !explicitlyAllowed {
+		// Check custom deny patterns
+		for _, pattern := range t.denyPatterns {
+			if pattern.MatchString(cmd) {
+				return fmt.Errorf("command matches blocked pattern")
+			}
+		}
+	}
+
 	return nil
 }

pkg/tools/shell/env.go

@@ -0,0 +1,249 @@
+package shell
+
+import (
+	"maps"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+// DefaultEnvAllowlist is the set of environment variable names that are safe
+// to propagate to child processes. Everything else is stripped to prevent
+// accidental credential leakage.
+//
+// To add a new variable:
+// 1. Add to this map if it's safe to pass through
+// 2. Or add a prefix to defaultEnvAllowPrefixes for pattern matching
+// Note: Do NOT add wildcard patterns like "*_API_KEY" here - use explicit names
+// to avoid accidentally leaking secrets.
+var DefaultEnvAllowlist = map[string]bool{
+	"PATH":        true,
+	"HOME":        true,
+	"USER":        true,
+	"LANG":        true,
+	"SHELL":       true,
+	"TERM":        true,
+	"PWD":         true,
+	"OLDPWD":      true,
+	"HOSTNAME":    true,
+	"LOGNAME":     true,
+	"TZ":          true,
+	"DISPLAY":     true,
+	"TMPDIR":      true,
+	"EDITOR":      true,
+	"PAGER":       true,
+	"HTTP_PROXY":  true,
+	"http_proxy":  true,
+	"HTTPS_PROXY": true,
+	"https_proxy": true,
+	"NO_PROXY":    true,
+	"no_proxy":    true,
+
+	// Locale
+	"LC_ALL":            true,
+	"LC_CTYPE":          true,
+	"LC_MESSAGES":       true,
+	"LC_MONETARY":       true,
+	"LC_NUMERIC":        true,
+	"LC_TIME":           true,
+	"LC_PAPER":          true,
+	"LC_NAME":           true,
+	"LC_ADDRESS":        true,
+	"LC_TELEPHONE":      true,
+	"LC_MEASUREMENT":    true,
+	"LC_IDENTIFICATION": true,
+	"LC_COLLATE":        true,
+
+	// systemd/user session (for systemctl --user and journalctl --user)
+	"XDG_RUNTIME_DIR":          true,
+	"DBUS_SESSION_BUS_ADDRESS": true,
+}
+
+// LLMBlocklist is the set of environment variable names that the LLM
+// cannot override, even if passed via the env parameter. These vars
+// control fundamental process behavior and could be exploited.
+var LLMBlocklist = map[string]bool{
+	"PATH":            true, // Could hijack command resolution
+	"HOME":            true, // Could redirect file access
+	"USER":            true, // Could impersonate user
+	"LOGNAME":         true, // Could impersonate user
+	"SHELL":           true, // Could change shell behavior
+	"LD_PRELOAD":      true, // Could inject code
+	"LD_LIBRARY_PATH": true, // Could hijack library resolution
+	"LD_AUDIT":        true, // Could inject code
+	"LD_DEBUG":        true, // Could leak info
+
+	// PICOCLAW_* vars - controlled by the agent, not LLM
+	"PICOCLAW_HOME":            true,
+	"PICOCLAW_CONFIG":          true,
+	"PICOCLAW_AGENT_WORKSPACE": true,
+	"PICOCLAW_EXE":             true,
+	"PICOCLAW_SERVICE_NAME":    true,
+	"PICOCLAW_EXEC_TIME":       true,
+	"PICOCLAW_EXEC_TIMEOUT":    true,
+}
+
+// windowsEnvAllowlist contains additional variables needed on Windows.
+var windowsEnvAllowlist = map[string]bool{
+	"PATHEXT":     true,
+	"SYSTEMROOT":  true,
+	"SYSTEMDRIVE": true,
+	"COMSPEC":     true,
+	"APPDATA":     true,
+	"USERPROFILE": true,
+	"HOMEDRIVE":   true,
+	"HOMEPATH":    true,
+}
+
+// WithAllowedEnv builds a map of allowed environment variables by looking them up.
+// This is more efficient than filtering os.Environ() with string parsing.
+// It starts with the provided env map, then adds allowed inherited vars (if not set).
+// extraAllowlist adds to the default allowlist.
+func WithAllowedEnv(envSet map[string]string, extraAllowlist []string) map[string]string {
+	// Copy the map to avoid mutating the caller's map
+	result := maps.Clone(envSet)
+	if result == nil {
+		result = make(map[string]string)
+	}
+
+	// Add default allowlist (only if not already set)
+	for k := range DefaultEnvAllowlist {
+		if _, exists := result[k]; !exists {
+			if val := os.Getenv(k); val != "" {
+				result[k] = val
+			}
+		}
+	}
+	// Add Windows-specific vars
+	if runtime.GOOS == "windows" {
+		for k := range windowsEnvAllowlist {
+			if _, exists := result[k]; !exists {
+				if val := os.Getenv(k); val != "" {
+					result[k] = val
+				}
+			}
+		}
+	}
+	// Add extra allowlist from config
+	for _, k := range extraAllowlist {
+		if _, exists := result[k]; !exists {
+			if val := os.Getenv(k); val != "" {
+				result[k] = val
+			}
+		}
+	}
+
+	return result
+}
+
+// LLMBlocklistPrefixes are env var prefixes that the LLM cannot override.
+var LLMBlocklistPrefixes = []string{
+	"PICOCLAW_",
+}
+
+// isBlocked returns true if the key is in the blocklist or matches a blocked prefix.
+func isBlocked(key string) bool {
+	norm := envKey(key)
+	if LLMBlocklist[norm] {
+		return true
+	}
+	for _, prefix := range LLMBlocklistPrefixes {
+		if strings.HasPrefix(norm, prefix) {
+			return true
+		}
+	}
+	return false
+}
+
+// MergeEnvVars merges multiple env sources into a map.
+// baseEnv is the cached map from AllowedEnv.
+// envSet provides explicit key=value pairs (config, not filtered).
+// extraEnv provides additional key=value pairs from LLM (filtered by blocklist).
+func MergeEnvVars(baseEnv map[string]string, envSet, extraEnv map[string]string) map[string]string {
+	vars := make(map[string]string, len(baseEnv)+len(envSet)+len(extraEnv))
+
+	// Start with base env (already filtered)
+	for k, v := range baseEnv {
+		vars[envKey(k)] = v
+	}
+
+	// Add envSet (config-provided, not filtered)
+	if envSet != nil {
+		for k, v := range envSet {
+			vars[envKey(k)] = v
+		}
+	}
+
+	// Merge extraEnv (LLM-provided) - filtered by blocklist
+	if extraEnv != nil {
+		for k, v := range extraEnv {
+			if isBlocked(k) {
+				continue // Skip blocked vars
+			}
+			vars[envKey(k)] = v
+		}
+	}
+
+	return vars
+}
+
+// MapToEnvSlice converts a map of environment variables to a []string
+// in the format "KEY=value" suitable for exec.Cmd.Env.
+func MapToEnvSlice(vars map[string]string) []string {
+	result := make([]string, 0, len(vars))
+	for k, v := range vars {
+		result = append(result, k+"="+v)
+	}
+	return result
+}
+
+// envKey normalizes an environment variable name. On Windows, where env
+// vars are case-insensitive, it uppercases the key so that "Path" and
+// "PATH" map to the same entry. On other platforms it's a no-op.
+func envKey(k string) string {
+	if runtime.GOOS == "windows" {
+		return strings.ToUpper(k)
+	}
+	return k
+}
+
+// WithPicoclawEnvVars ensures PICOCLAW_* vars are set in envSet.
+// These are needed for child processes to locate config, workspace, etc.
+func WithPicoclawEnvVars(envSet map[string]string, workspace string) map[string]string {
+	// Copy the map to avoid mutating the caller's map
+	result := maps.Clone(envSet)
+	if result == nil {
+		result = make(map[string]string)
+	}
+
+	// Always compute PICOCLAW_* vars - priority: env var > default
+	if v := os.Getenv("PICOCLAW_HOME"); v != "" {
+		result["PICOCLAW_HOME"] = v
+	} else if home, _ := os.UserHomeDir(); home != "" {
+		result["PICOCLAW_HOME"] = filepath.Join(home, ".picoclaw")
+	}
+
+	if v := os.Getenv("PICOCLAW_CONFIG"); v != "" {
+		result["PICOCLAW_CONFIG"] = v
+	} else if home := result["PICOCLAW_HOME"]; home != "" {
+		result["PICOCLAW_CONFIG"] = filepath.Join(home, "config.json")
+	}
+
+	// Workspace - this is the agent's working directory
+	if workspace != "" {
+		result["PICOCLAW_AGENT_WORKSPACE"] = workspace
+	}
+
+	if exe, err := os.Executable(); err == nil {
+		result["PICOCLAW_EXE"] = exe
+	}
+
+	if v := os.Getenv("PICOCLAW_SERVICE_NAME"); v != "" {
+		result["PICOCLAW_SERVICE_NAME"] = v
+	} else {
+		result["PICOCLAW_SERVICE_NAME"] = "picoclaw"
+	}
+
+	return result
+}