CnaEmulator is a standalone Java harness that validates .cna Aggressor Script syntax, mocks Beacon APIs, and executes BOFs via COFFLoader64.exe for authorized tool developers and researchers.
| Tool | iterat0r/CnaEmulator — standalone emulation and testing harness for Cobalt Strike Aggressor Scripts |
| Category | Java development/testing harness for offensive tooling |
| Primary Use | Validating .cna syntax, mocking Beacon APIs, and regression-testing BOF aliases without a teamserver or GUI client |
| Safe Use | Intended for security researchers, tool developers, and BOF authors working in authorized lab environments and controlled development workflows |
| Telemetry Note | Purely a local development tool; it launches no network infrastructure, and defenders should note that BOF execution occurs in-process via COFFLoader64.exe on the analyst's own machine, leaving only local process and stdout traces |
Anyone who has written a Cobalt Strike Aggressor Script knows the friction: the natural edit-test loop for a .cna file traditionally demands a licensed teamserver, a connected GUI client, and at least one live Beacon session before an alias can be exercised end to end. iterat0r/CnaEmulator attacks exactly that bottleneck. It is a standalone, general-purpose development, emulation, and testing harness, written in Java, that compiles and validates .cna scripts against the real Sleep 2.1 engine, mocks the Aggressor API surface, and even executes Beacon Object Files in memory through COFFLoader64.exe — all without a single piece of Cobalt Strike infrastructure running.
The architecture is best understood as three layers stitched together by a thin CLI. The first layer is the parsing core: the CnaEmulator.java class bridges the Sleep engine, so the check action performs genuine compilation rather than regex-based linting. The README claims it accurately catches runaway strings, unescaped characters, parser syntax errors, and missing delimiters, reporting exact file line numbers. That detail matters, because .cna scripts are Sleep source at heart, and shallow syntax checkers routinely miss the failure modes that actually break script loading on a real teamserver.
The second layer is API emulation. CnaEmulator reimplements the documented Aggressor function catalog — process injection, token manipulation, filesystem, network, and GUI callback APIs — returning realistic mock values or positive non-error results. The idea is that a script's control flow can be exercised fully offline: aliases resolve, guard clauses fire, argument counts validate, and blog/berror/btask messages format correctly to stdout. Functions like beacon_command_register, beacon_commands, and beacon_command_detail maintain a live command catalog, which is what powers the tool's interactive help system.
The third layer is where the harness gets genuinely interesting for BOF authors. bof_pack implements native Little-Endian serialization matching Cobalt Strike's datap binary format — 'i' for 4-byte integers, 's' for shorts, 'z' for length-prefixed null-terminated strings, 'Z' for wide UTF-16LE strings, and 'b' for length-prefixed binary buffers, each with a 4-byte length prefix. The harness intercepts beacon_inline_execute($bid, $bof_data, "go", $packed_args), converts the packed arguments to hex, and spawns COFFLoader64.exe go <bof_path> <hex_args> as a child subprocess, streaming its console output live to stdout. In practical terms, you get the argument-marshalling contract of the real Beacon execution path exercised against the same public COFF loader from trustedsec/COFFLoader.
Operationally, the project is Windows-centric and self-contained. The repository ships cna_emulator.bat as the recommended launcher, which handles JDK discovery, classpath assembly, and path resolution. Prerequisites are a Java JDK 17+ with JAVA_HOME set, Sleep 2.1 as sleep.jar (locatable via a SLEEP_JAR environment variable or placement in the root/CnaEmulator directory), and COFFLoader64.exe in the root or pointed to via COFFLOADER_PATH. Four actions drive everything: check for syntax validation, run for single alias execution with live BOF dispatch, test for automated batteries, and console for an interactive beacon> prompt with command history and per-alias help.
The test action deserves attention because it encodes a whole methodology for regression-testing offensive tooling. CnaEmulator auto-discovers companion suites named <script>.cna.tests or <script>.tests sitting adjacent to the script; each non-comment line is an alias invocation with arguments, executed sequentially. If no companion file exists, the harness introspects all registered aliases and runs guard-clause tests, verifying that invalid argument counts produce usage errors rather than unhandled exceptions. That last behavior — automated verification that your BOF's argument validation doesn't crash the script engine — is the kind of polish usually missing from red-team tooling repos, and it maps directly to fewer mid-engagement surprises.
The project also ships its own quality gates. A 48-scenario, seven-category test specification (documented in TEST_SPEC.md, with a verification report in TESTING.md) is executable via CnaEmulator\test.bat, and the README reports 48/48 passing with 172 assertions in roughly 2.8 seconds. Bundled fixtures — sample_bof.cna, multi_alias.cna, and their companion .tests files — give newcomers an immediately runnable path from clone to green output. One caveat the author states plainly in a warning banner: the code was fully generated with Antigravity and has not yet been reviewed. Treat that as an instruction to audit the Java source before relying on it, and to sandbox COFFLoader64.exe execution regardless of provenance.
For authorized use, the positioning is clear: this is a developer's workbench, not an engagement tool. It belongs in the same mental category as unit-test scaffolds and CI linters — the place where a BOF author validates that a .cna loads cleanly, that bof_pack format strings match the loader's parsing, and that alias help text renders, all before anything touches operational infrastructure. Because script_resource resolution searches the script directory, bin/, ../bin/, and relative paths, external BOF projects anywhere on the filesystem can be dropped in without restructuring. Two representative invocations illustrate the shape of a workflow: cna_emulator.bat check CnaEmulator\tests\fixtures\sample_bof.cna validates a bundled script, and cna_emulator.bat test C:\Projects\CustomBof\my_bof.cna runs the full companion battery against an external project.
From a defensive research angle, CnaEmulator is equally useful as an analysis instrument. Analysts dissecting third-party .cna scripts or studying BOF behavior can load them in a harness where every emulated API call is observable and no real post-exploitation occurs — the mocked Beacon functions return synthetic data, and BOF execution happens inside a local COFFLoader64.exe subprocess on the analyst's own machine. It runs no listeners, beacons out nowhere, and touches no network beyond what the operator's local processes do, so the telemetry footprint is essentially local process creation and console output.
With 21 stars, no license file declared, and a candid AI-generation disclaimer, this is an early-stage but thoughtfully specified project rather than a battle-tested utility. The specification-driven test suite, the exact datap format emulation, and the guard-clause automation suggest real engineering intent. For BOF developers and authorized red-team tooling maintainers who have suffered through Sleep parser errors surfacing only after a script reload against a live session, CnaEmulator offers a credible local loop — review the source first, run it in a lab, and it earns its place next to the compiler in your toolchain.
iterat0r/CnaEmulator.Educational analysis for authorized security professionals. Use only in controlled, authorized environments.
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