lib: explicitly initialize debuglog during bootstrap

This patch splits the implementation of util.debuglog into a
separate file and explicitly initialize it during pre-execution
since the initialization depends on environment variables.
Also delays the call to `debuglog` in modules that are loaded during
bootstrap to make sure we only access the environment variable
during pre-execution.

PR-URL: https://github.com/nodejs/node/pull/26468
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/internal/util/debuglog.js b/lib/internal/util/debuglog.js
new file mode 100644
index 0000000000..769328ac9d
--- /dev/null
+++ b/lib/internal/util/debuglog.js
@@ -0,0 +1,54 @@
+'use strict';
+
+const { format } = require('internal/util/inspect');
+
+// `debugs` is deliberately initialized to undefined so any call to
+// debuglog() before initializeDebugEnv() is called will throw.
+let debugs;
+
+let debugEnvRegex = /^$/;
+
+// `debugEnv` is initial value of process.env.NODE_DEBUG
+function initializeDebugEnv(debugEnv) {
+  debugs = {};
+  if (debugEnv) {
+    debugEnv = debugEnv.replace(/[|\\{}()[\]^$+?.]/g, '\\$&')
+      .replace(/\*/g, '.*')
+      .replace(/,/g, '$|^')
+      .toUpperCase();
+    debugEnvRegex = new RegExp(`^${debugEnv}$`, 'i');
+  }
+}
+
+// Emits warning when user sets
+// NODE_DEBUG=http or NODE_DEBUG=http2.
+function emitWarningIfNeeded(set) {
+  if ('HTTP' === set || 'HTTP2' === set) {
+    process.emitWarning('Setting the NODE_DEBUG environment variable ' +
+      'to \'' + set.toLowerCase() + '\' can expose sensitive ' +
+      'data (such as passwords, tokens and authentication headers) ' +
+      'in the resulting log.');
+  }
+}
+
+function debuglog(set) {
+  set = set.toUpperCase();
+  if (!debugs[set]) {
+    if (debugEnvRegex.test(set)) {
+      const pid = process.pid;
+      emitWarningIfNeeded(set);
+      debugs[set] = function debug(...args) {
+        const msg = format(...args);
+        console.error('%s %d: %s', set, pid, msg);
+      };
+    } else {
+      debugs[set] = function debug() {};
+    }
+  }
+  return debugs[set];
+}
+
+module.exports = {
+  debuglog,
+  initializeDebugEnv
+};