Function validateObfuscatedFlags

src/tools/BashTool/bashSecurity.ts:1130–1537

(context: ValidationContext)

}

function validateObfuscatedFlags(context: ValidationContext): PermissionResult {
  // Block shell quoting bypass patterns used to circumvent negative lookaheads we use in our regexes to block known dangerous flags

  const { originalCommand, baseCommand } = context

  // Echo is safe for obfuscated flags, BUT only for simple echo commands.
  // For compound commands (with |, &, ;), we need to check the whole command
  // because the dangerous ANSI-C quoting might be after the operator.
  const hasShellOperators = /[|&;]/.test(originalCommand)
  if (baseCommand === 'echo' && !hasShellOperators) {
    return {
      behavior: 'passthrough',
      message: 'echo command is safe and has no dangerous flags',
    }
  }

  // COMPREHENSIVE OBFUSCATION DETECTION
  // These checks catch various ways to hide flags using shell quoting

  // 1. Block ANSI-C quoting ($'...') - can encode any character via escape sequences
  // Simple pattern that matches $'...' anywhere. This correctly handles:
  // - grep '$' file => no match ($ is regex anchor inside quotes, no $'...' structure)
  // - 'test'$'-exec' => match (quote concatenation with ANSI-C)
  // - Zero-width space and other invisible chars => match
  // The pattern requires $' followed by content (can be empty) followed by closing '
  if (/\$'[^']*'/.test(originalCommand)) {
    logEvent('tengu_bash_security_check_triggered', {
      checkId: BASH_SECURITY_CHECK_IDS.OBFUSCATED_FLAGS,
      subId: 5,
    })
    return {
      behavior: 'ask',
      message: 'Command contains ANSI-C quoting which can hide characters',
    }
  }

  // 2. Block locale quoting ($"...")  - can also use escape sequences
  // Same simple pattern as ANSI-C quoting above
  if (/\$"[^"]*"/.test(originalCommand)) {
    logEvent('tengu_bash_security_check_triggered', {
      checkId: BASH_SECURITY_CHECK_IDS.OBFUSCATED_FLAGS,
      subId: 6,
    })
    return {
      behavior: 'ask',
      message: 'Command contains locale quoting which can hide characters',
    }
  }

  // 3. Block empty ANSI-C or locale quotes followed by dash
  // $''-exec or $""-exec
  if (/\$['"]{2}\s*-/.test(originalCommand)) {
    logEvent('tengu_bash_security_check_triggered', {
      checkId: BASH_SECURITY_CHECK_IDS.OBFUSCATED_FLAGS,
      subId: 9,
    })
    return {
      behavior: 'ask',