fix(utils): add path traversal validation for ShardedWal groupId

packages/utils/src/lib/wal-sharded.ts

@@ -28,6 +28,44 @@ function ensureDirectoryExistsSync(dirPath: string): void {
   }
 }
 
+/**
+ * Validates that a groupId is safe to use as a single path segment.
+ * Rejects path traversal attempts and path separators to prevent writing outside intended directory.
+ *
+ * @param groupId - The groupId to validate
+ * @throws Error if groupId contains unsafe characters or path traversal sequences
+ */
+function validateGroupId(groupId: string): void {
+  // Reject empty or whitespace-only groupIds
+  if (!groupId || groupId.trim().length === 0) {
+    throw new Error('groupId cannot be empty or whitespace-only');
+  }
+
+  // Reject path separators (both forward and backward slashes)
+  if (groupId.includes('/') || groupId.includes('\\')) {
+    throw new Error('groupId cannot contain path separators (/ or \\)');
+  }
+
+  // Reject relative path components
+  if (groupId === '..' || groupId === '.') {
+    throw new Error('groupId cannot be "." or ".."');
+  }
+
+  // Reject null bytes which can be used to bypass validation
+  if (groupId.includes('\0')) {
+    throw new Error('groupId cannot contain null bytes');
+  }
+
+  // Validate that the resolved path stays within the intended directory
+  // This catches cases where the path library normalizes to a parent directory
+  const normalized = path.normalize(groupId);
+  if (normalized !== groupId || normalized.startsWith('..')) {
+    throw new Error(
+      `groupId normalization resulted in unsafe path: ${normalized}`,
+    );
+  }
+}
+
 // eslint-disable-next-line functional/no-let
 let shardCount = 0;
 
@@ -142,10 +180,10 @@ export class ShardedWal<T extends WalRecord = WalRecord> {
     // Determine groupId: use provided, then env var, or generate
     // eslint-disable-next-line functional/no-let
     let resolvedGroupId: string;
-    if (groupId) {
-      // User explicitly provided groupId - use it
+    if (groupId != null) {
+      // User explicitly provided groupId - use it (even if empty, validation will catch it)
       resolvedGroupId = groupId;
-    } else if (measureNameEnvVar && process.env[measureNameEnvVar]) {
+    } else if (measureNameEnvVar && process.env[measureNameEnvVar] != null) {
       // Env var is set (by coordinator or previous process) - use it
       resolvedGroupId = process.env[measureNameEnvVar];
     } else if (measureNameEnvVar) {
@@ -158,6 +196,9 @@ export class ShardedWal<T extends WalRecord = WalRecord> {
       resolvedGroupId = getUniqueTimeId();
     }
 
+    // Validate groupId for path safety before using it
+    validateGroupId(resolvedGroupId);
+
     this.groupId = resolvedGroupId;
 
     if (dir) {

packages/utils/src/lib/wal-sharded.unit.test.ts

@@ -18,6 +18,7 @@ const getShardedWal = (overrides?: {
   format?: Partial<WalFormat>;
   measureNameEnvVar?: string;
   autoCoordinator?: boolean;
+  groupId?: string;
 }) => {
   const { format, ...rest } = overrides ?? {};
   return new ShardedWal({
@@ -39,6 +40,9 @@ describe('ShardedWal', () => {
     // Clear coordinator env var for fresh state
     // eslint-disable-next-line functional/immutable-data, @typescript-eslint/no-dynamic-delete
     delete process.env[PROFILER_SHARDER_ID_ENV_VAR];
+    // Clear measure name env var to avoid test pollution
+    // eslint-disable-next-line functional/immutable-data, @typescript-eslint/no-dynamic-delete
+    delete process.env.CP_PROFILER_MEASURE_NAME;
   });
 
   describe('initialization', () => {
@@ -73,6 +77,70 @@ describe('ShardedWal', () => {
     });
   });
 
+  describe('path traversal validation', () => {
+    it('should reject groupId with forward slashes', () => {
+      expect(() => getShardedWal({ groupId: '../etc/passwd' })).toThrow(
+        'groupId cannot contain path separators (/ or \\)',
+      );
+    });
+
+    it('should reject groupId with backward slashes', () => {
+      expect(() => getShardedWal({ groupId: '..\\windows\\system32' })).toThrow(
+        'groupId cannot contain path separators (/ or \\)',
+      );
+    });
+
+    it('should reject groupId with parent directory reference', () => {
+      expect(() => getShardedWal({ groupId: '..' })).toThrow(
+        'groupId cannot be "." or ".."',
+      );
+    });
+
+    it('should reject groupId with current directory reference', () => {
+      expect(() => getShardedWal({ groupId: '.' })).toThrow(
+        'groupId cannot be "." or ".."',
+      );
+    });
+
+    it('should reject groupId with null bytes', () => {
+      expect(() => getShardedWal({ groupId: 'test\0malicious' })).toThrow(
+        'groupId cannot contain null bytes',
+      );
+    });
+
+    it('should reject empty groupId', () => {
+      expect(() => getShardedWal({ groupId: '' })).toThrow(
+        'groupId cannot be empty or whitespace-only',
+      );
+    });
+
+    it('should reject whitespace-only groupId', () => {
+      expect(() => getShardedWal({ groupId: '   ' })).toThrow(
+        'groupId cannot be empty or whitespace-only',
+      );
+    });
+
+    it('should accept safe alphanumeric groupId', () => {
+      const sw = getShardedWal({ groupId: 'safe-group-123' });
+      expect(sw.groupId).toBe('safe-group-123');
+    });
+
+    it('should accept groupId with underscores and hyphens', () => {
+      const sw = getShardedWal({ groupId: 'test_group-name' });
+      expect(sw.groupId).toBe('test_group-name');
+    });
+
+    it('should reject groupId from env var with path traversal', () => {
+      // eslint-disable-next-line functional/immutable-data
+      process.env.CP_PROFILER_MEASURE_NAME = '../malicious';
+      expect(() =>
+        getShardedWal({
+          measureNameEnvVar: 'CP_PROFILER_MEASURE_NAME',
+        }),
+      ).toThrow('groupId cannot contain path separators (/ or \\)');
+    });
+  });
+
   describe('shard management', () => {
     it('should create shard with correct file path', () => {
       const sw = getShardedWal({