FEAT: Harden Shell Actuator and implement formal safety tests
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docs/rca/rca-shell-hardening.org
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docs/rca/rca-shell-hardening.org
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#+TITLE: Root Cause Analysis: Shell Actuator Security Hardening
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#+DATE: 2026-04-11
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#+FILETAGS: :rca:security:shell:injection:psf:
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* Executive Summary
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During the formal verification of the `org-skill-shell-actuator`, a critical command injection vulnerability was identified and patched. The previous implementation relied on a naive whitelist check that could be bypassed using shell metacharacters.
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* 1. Issue: Command Injection Vulnerability
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** Symptoms
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Commands like `ls ; rm -rf /` were potentially executable if the first word (`ls`) was in the whitelist.
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** Root Cause
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The `execute-shell-safely` function only checked the first space-delimited word of the command string against the `*allowed-commands*` whitelist. Since `uiop:run-program` executes string-based commands via `/bin/sh -c`, the shell would process the entire string, including injected commands following metacharacters like `;`, `&`, or `|`.
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** Resolution
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1. **Metacharacter Blacklist:** Introduced `*shell-metacharacters*` containing dangerous shell symbols (`; & | > < $ \` \ !`).
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2. **Strict Validation:** Updated `execute-shell-safely` to scan the *entire* command string for these characters before performing the whitelist check.
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3. **Defense-in-Depth:** Any command containing a metacharacter is now rejected with a "Security Violation" error, even if the primary command is whitelisted.
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* 2. Side-Issue: Missing Package Context
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** Symptoms
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`UNDEFINED-FUNCTION EXECUTE-SHELL-SAFELY` during unit tests.
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** Root Cause
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`src/shell-logic.lisp` was missing an `(in-package :org-agent)` declaration, causing symbols to be defined in the default `COMMON-LISP-USER` package instead of the kernel package.
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** Resolution
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Added the `in-package` header to `shell-logic.lisp`.
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* 3. PSF Mandate Alignment
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** Invariant Check
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- *High-Integrity Memory:* The shell actuator is now formally verified with 4 new unit tests covering whitelist enforcement and injection blocking.
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- *Literate Programming:* Updated `org-skill-shell-actuator.org` Phase A and Build sections to reflect the hardened logic.
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* 4. Permanent Learnings
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- **Whole-String Validation:** Never assume that whitelisting the "head" of a command string is sufficient when passing that string to a shell.
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- **Subshell Avoidance:** While the current fix blacklists metacharacters, future iterations should move toward passing command arguments as a Lisp list to `uiop:run-program`, bypassing the shell entirely.
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@@ -19,6 +19,7 @@
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(:file "src/safety-harness")
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(:file "src/self-fix")
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(:file "src/lisp-repair")
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(:file "src/shell-logic")
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(:file "src/bouncer")
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(:file "src/core"))
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:build-operation "program-op"
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@@ -38,7 +39,7 @@
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(:file "tests/self-fix-tests")
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(:file "tests/lisp-repair-tests")
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(:file "tests/bouncer-tests")
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(:file "tests/llm-gateway-tests")
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(:file "tests/shell-actuator-tests")
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(:file "tests/chaos-qa"))
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:perform (test-op (o s)
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(uiop:symbol-call :fiveam :run! (uiop:find-symbol* :oacp-suite :org-agent-tests))
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@@ -53,4 +54,5 @@
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(uiop:symbol-call :fiveam :run! (uiop:find-symbol* :lisp-repair-suite :org-agent-lisp-repair-tests))
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(uiop:symbol-call :fiveam :run! (uiop:find-symbol* :bouncer-suite :org-agent-bouncer-tests))
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(uiop:symbol-call :fiveam :run! (uiop:find-symbol* :llm-gateway-suite :org-agent-llm-gateway-tests))
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(uiop:symbol-call :fiveam :run! (uiop:find-symbol* :shell-actuator-suite :org-agent-shell-actuator-tests))
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(uiop:symbol-call :fiveam :run! (uiop:find-symbol* :chaos-suite :org-agent-chaos-qa))))
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@@ -42,6 +42,30 @@ Interfaces for secure system calls. State is event-driven via the core kernel bu
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(defun execute-shell-safely (action)
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"Verifies command against whitelist and captures diagnostics.")
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(defun trigger-skill-shell-actuator (context)
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"Monitors for shell-response events.")
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** 3. Success Criteria
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*** DONE Whitelist Enforcement
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- Verified that only `*allowed-commands*` can be executed.
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- Added a strict `*shell-metacharacters*` check to block command injection.
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*** DONE Diagnostic Capture
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- Verified that STDOUT, STDERR, and Exit Codes are correctly captured and re-injected.
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*** DONE Result Analysis Loop
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- The `:neuro` component successfully formats command results for Sovereign review.
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* Phase B: Blueprint (PROTOCOL)
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:PROPERTIES:
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:STATUS: SIGNED
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:END:
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** 1. Architectural Intent
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Interfaces for secure system calls. State is event-driven via the core kernel bus.
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** 2. Semantic Interfaces
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#+begin_src lisp
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(defun execute-shell-safely (action)
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"Verifies command against whitelist and metacharacter blacklist, then captures diagnostics.")
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(defun trigger-skill-shell-actuator (context)
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"Monitors for shell-response events.")
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@@ -53,21 +77,41 @@ Interfaces for secure system calls. State is event-driven via the core kernel bu
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** Whitelisting & Execution
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#+begin_src lisp :tangle ../src/shell-logic.lisp
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(in-package :org-agent)
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(defparameter *allowed-commands* '("ls" "git" "rg" "grep" "date" "echo" "cat" "node" "python3" "sbcl"))
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(defparameter *shell-metacharacters* '(#\; #\& #\| #\> #\< #\$ #\` #\\ #\!)
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"Characters that are banned in shell commands to prevent injection.")
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(defun shell-command-safe-p (cmd-string)
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"Returns T if the command string contains no dangerous metacharacters."
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(not (some (lambda (char) (find char cmd-string)) *shell-metacharacters*)))
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(defun execute-shell-safely (action context)
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(let* ((cmd-string (getf (getf action :payload) :cmd))
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(executable (car (uiop:split-string cmd-string :separator '(#\Space)))))
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(if (member executable *allowed-commands* :test #'string=)
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(multiple-value-bind (stdout stderr exit-code)
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(uiop:run-program cmd-string :output :string :error-output :string :ignore-error-status t)
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout ,(or stdout "") :stderr ,(or stderr "") :exit-code ,exit-code))
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:stream (getf context :reply-stream)))
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout "" :stderr "ERROR - Command not in security whitelist." :exit-code 1))
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:stream (getf context :reply-stream)))))
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(executable (car (uiop:split-string (string-trim " " cmd-string) :separator '(#\Space)))))
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(cond
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;; 1. Metacharacter check (Injection prevention)
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((not (shell-command-safe-p cmd-string))
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout "" :stderr "ERROR - Security Violation: Dangerous metacharacters detected." :exit-code 1))
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:stream (getf context :reply-stream)))
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;; 2. Whitelist check
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((not (member executable *allowed-commands* :test #'string=))
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout "" :stderr "ERROR - Command not in security whitelist." :exit-code 1))
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:stream (getf context :reply-stream)))
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;; 3. Safe Execution
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(t
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(multiple-value-bind (stdout stderr exit-code)
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(uiop:run-program cmd-string :output :string :error-output :string :ignore-error-status t)
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout ,(or stdout "") :stderr ,(or stderr "") :exit-code ,exit-code))
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:stream (getf context :reply-stream)))))))
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#+end_src
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(defun execute-sandboxed-script (action context)
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"Executes a synthesized script (Python/Lisp/JS) in a controlled directory.
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This enables SOTA-level Tool Synthesis and Iterative Fixing."
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@@ -1,17 +1,37 @@
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(in-package :org-agent)
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(defparameter *allowed-commands* '("ls" "git" "rg" "grep" "date" "echo" "cat" "node" "python3" "sbcl"))
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(defparameter *shell-metacharacters* '(#\; #\& #\| #\> #\< #\$ #\` #\\ #\!)
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"Characters that are banned in shell commands to prevent injection.")
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(defun shell-command-safe-p (cmd-string)
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"Returns T if the command string contains no dangerous metacharacters."
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(not (some (lambda (char) (find char cmd-string)) *shell-metacharacters*)))
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(defun execute-shell-safely (action context)
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(let* ((cmd-string (getf (getf action :payload) :cmd))
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(executable (car (uiop:split-string cmd-string :separator '(#\Space)))))
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(if (member executable *allowed-commands* :test #'string=)
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(multiple-value-bind (stdout stderr exit-code)
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(uiop:run-program cmd-string :output :string :error-output :string :ignore-error-status t)
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout ,(or stdout "") :stderr ,(or stderr "") :exit-code ,exit-code))
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:stream (getf context :reply-stream)))
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout "" :stderr "ERROR - Command not in security whitelist." :exit-code 1))
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:stream (getf context :reply-stream)))))
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(executable (car (uiop:split-string (string-trim " " cmd-string) :separator '(#\Space)))))
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(cond
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;; 1. Metacharacter check (Injection prevention)
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((not (shell-command-safe-p cmd-string))
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout "" :stderr "ERROR - Security Violation: Dangerous metacharacters detected." :exit-code 1))
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:stream (getf context :reply-stream)))
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;; 2. Whitelist check
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((not (member executable *allowed-commands* :test #'string=))
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout "" :stderr "ERROR - Command not in security whitelist." :exit-code 1))
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:stream (getf context :reply-stream)))
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;; 3. Safe Execution
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(t
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(multiple-value-bind (stdout stderr exit-code)
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(uiop:run-program cmd-string :output :string :error-output :string :ignore-error-status t)
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(org-agent:inject-stimulus
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`(:type :EVENT :payload (:sensor :shell-response :cmd ,cmd-string :stdout ,(or stdout "") :stderr ,(or stderr "") :exit-code ,exit-code))
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:stream (getf context :reply-stream)))))))
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(defun execute-sandboxed-script (action context)
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"Executes a synthesized script (Python/Lisp/JS) in a controlled directory.
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83
tests/shell-actuator-tests.lisp
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83
tests/shell-actuator-tests.lisp
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(defpackage :org-agent-shell-actuator-tests
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(:use :cl :fiveam :org-agent)
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(:export #:shell-actuator-suite))
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(in-package :org-agent-shell-actuator-tests)
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(def-suite shell-actuator-suite :description "Tests for Shell Actuator safety and diagnostics.")
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(in-suite shell-actuator-suite)
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(test test-whitelisted-execution
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"Verify that a whitelisted command executes and returns output."
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(let* ((action '(:type :REQUEST :target :tool :payload (:action :call :tool "shell" :cmd "echo \"hello shell\"")))
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(context '(:reply-stream nil))
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(original-inject (symbol-function 'org-agent:inject-stimulus))
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(captured-stimulus nil))
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(unwind-protect
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(progn
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(setf (symbol-function 'org-agent:inject-stimulus)
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(lambda (stim &key stream)
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(declare (ignore stream))
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(setf captured-stimulus stim)))
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(org-agent::execute-shell-safely action context)
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(is (not (null captured-stimulus)))
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(is (eq :EVENT (getf captured-stimulus :type)))
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(is (eq :shell-response (getf (getf captured-stimulus :payload) :sensor)))
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(is (search "hello shell" (getf (getf captured-stimulus :payload) :stdout)))
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(is (= 0 (getf (getf captured-stimulus :payload) :exit-code))))
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(setf (symbol-function 'org-agent:inject-stimulus) original-inject))))
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(test test-unlisted-command-blocked
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"Verify that a non-whitelisted command is blocked."
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(let* ((action '(:type :REQUEST :target :tool :payload (:action :call :tool "shell" :cmd "wget http://example.com")))
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(context '(:reply-stream nil))
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(original-inject (symbol-function 'org-agent:inject-stimulus))
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(captured-stimulus nil))
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(unwind-protect
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(progn
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(setf (symbol-function 'org-agent:inject-stimulus)
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(lambda (stim &key stream)
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(declare (ignore stream))
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(setf captured-stimulus stim)))
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(org-agent::execute-shell-safely action context)
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(is (not (null captured-stimulus)))
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(is (search "ERROR - Command not in security whitelist" (getf (getf captured-stimulus :payload) :stderr)))
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(is (= 1 (getf (getf captured-stimulus :payload) :exit-code))))
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(setf (symbol-function 'org-agent:inject-stimulus) original-inject))))
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(test test-command-injection-blocked
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"Verify that command injection attempts are blocked."
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(let* ((action '(:type :REQUEST :target :tool :payload (:action :call :tool "shell" :cmd "ls ; date")))
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(context '(:reply-stream nil))
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(original-inject (symbol-function 'org-agent:inject-stimulus))
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(captured-stimulus nil))
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(unwind-protect
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(progn
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(setf (symbol-function 'org-agent:inject-stimulus)
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(lambda (stim &key stream)
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(declare (ignore stream))
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(setf captured-stimulus stim)))
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(org-agent::execute-shell-safely action context)
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(is (not (null captured-stimulus)))
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;; With current (vulnerable) code, this might actually pass whitelisting
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;; because the first word is "ls". We WANT this to fail.
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(is (search "ERROR" (getf (getf captured-stimulus :payload) :stderr)))
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(is (search "Security Violation" (getf (getf captured-stimulus :payload) :stderr))))
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(setf (symbol-function 'org-agent:inject-stimulus) original-inject))))
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(test test-error-capture
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"Verify that a failing whitelisted command returns STDERR and exit code."
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(let* ((action '(:type :REQUEST :target :tool :payload (:action :call :tool "shell" :cmd "ls /non-existent-directory")))
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(context '(:reply-stream nil))
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(original-inject (symbol-function 'org-agent:inject-stimulus))
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(captured-stimulus nil))
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(unwind-protect
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(progn
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(setf (symbol-function 'org-agent:inject-stimulus)
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(lambda (stim &key stream)
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(declare (ignore stream))
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(setf captured-stimulus stim)))
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(org-agent::execute-shell-safely action context)
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(is (not (null captured-stimulus)))
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(is (not (= 0 (getf (getf captured-stimulus :payload) :exit-code))))
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(is (not (equal "" (getf (getf captured-stimulus :payload) :stderr)))))
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(setf (symbol-function 'org-agent:inject-stimulus) original-inject))))
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