feat: adding support for CHALK_BYPASS environment variable

this allows to completely skip chalk when wrapping `docker`.
Whenever its enabled, chalk directly proxies the command
to `docker` without invoking any of the chalk internal machinery
such as loading configs/etc

CHANGELOG.md

@@ -10,6 +10,9 @@
 - `_OP_CLOUD_SYS_VENDOR` key for reporting sys vendor
   file content used to identity cloud provider.
   ([#418](https://github.com/crashappsec/chalk/pull/418))
+- Supporting `CHALK_BYPASS` environment variable which
+  bypasses chalk altogether when chalk wraps `docker`.
+  ([#419](https://github.com/crashappsec/chalk/pull/419))
 
 ## 0.4.12
 

src/bypass.nim

@@ -0,0 +1,36 @@
+##
+## Copyright (c) 2024, Crash Override, Inc.
+##
+## This file is part of Chalk
+## (see https://crashoverride.com/docs/chalk)
+##
+
+import std/[os, strutils]
+import pkg/nimutils/[file]
+import "."/[util]
+
+proc bypassChalk*() =
+  # bypass any chalk execution if possible and directly exec into underlying command
+      # note this function explicitly uses echo for "logging" not to invoke any of the con4m machinery
+  if getEnv("CHALK_BYPASS").toLower() notin @["1", "true", "on"]:
+    return
+
+  let
+    (path, exe) = getAppFilename().splitPath()
+    # setup.sh for example stores chalkless variants of binaries
+    # in chalkless folder
+    # we need to account for it as otherwise original binary
+    # might not be on PATH overwise
+    # and as we dont load the chalk config here as a precausion
+    # we mimick disk structure direcly
+    chalklessDir = path.parentDir().joinPath("chalkless")
+
+  case exe
+  of "docker":
+    let chalkless = file.findExePath(exe, extraPaths = @[chalklessDir])
+    if chalkless == "":
+      stderr.writeLine("Could not find " & exe & " to exec while bypassing chalk")
+      quitChalk(1)
+    handleExec(@[chalkless], commandLineParams(), log = false)
+  else:
+    return

src/chalk.nim

@@ -7,10 +7,12 @@
 
 # Note that imports cause topics and plugins to register.
 {.warning[UnusedImport]: off.}
-import "."/[config, confload, commands, norecurse, sinks,
+import "."/[bypass, config, confload, commands, norecurse, sinks,
             attestation_api, util]
 
 when isMainModule:
+  bypassChalk()
+
   setupSignalHandlers() # util.nim
   setupTerminal()       # util.nim
   ioSetup()             # sinks.nim

src/util.nim

@@ -399,10 +399,11 @@ proc findExePath*(cmdName:    string,
   trace("Found '" & cmdName & "' in PATH: " & foundExes[0])
   return some(foundExes[0])
 
-proc handleExec*(prioritizedExes: seq[string], args: seq[string]) {.noreturn.} =
+proc handleExec*(prioritizedExes: seq[string], args: seq[string], log = true) {.noreturn.} =
   for path in prioritizedExes:
     let cargs = allocCStringArray(@[path] & args)
-    trace("execv: " & path & " " & args.join(" "))
+    if log:
+      trace("execv: " & path & " " & args.join(" "))
     discard execv(cstring(path), cargs)
     # Either execv doesn't return, or something went wrong. No need to check the
     # error code.

tests/functional/data/configs/docker_cmd.c4m

@@ -1 +1,2 @@
 default_command: "docker"
+error("chalk is wrapping docker")

tests/functional/test_docker.py

@@ -1344,14 +1344,17 @@ def test_docker_diff_user(chalk_default: Chalk):
     assert result
 
 
-def test_docker_default_command(chalk_copy: Chalk, tmp_data_dir: Path):
+@pytest.mark.parametrize("bypass", [True, False])
+def test_docker_default_command(chalk_copy: Chalk, tmp_data_dir: Path, bypass: bool):
     assert chalk_copy.load(CONFIGS / "docker_cmd.c4m")
     expected = Docker.version()
     docker = tmp_data_dir / "docker"
     shutil.copy(chalk_copy.binary, docker)
-    actual = run([str(docker), "--version"])
+    actual = run([str(docker), "--version"], env={"CHALK_BYPASS": str(bypass)})
     assert actual
     assert actual.text == expected.text
+    if bypass:
+        assert actual.logs == expected.logs
 
 
 def test_version_bare(chalk_default: Chalk):