[Security] Harden relative path sanitization

packages/cli-kit/src/public/node/path.test.ts

@@ -1,5 +1,5 @@
-import {relativizePath, normalizePath, cwd, sniffForPath, commonParentDirectory} from './path.js'
-import {describe, test, expect} from 'vitest'
+import {relativizePath, normalizePath, cwd, sniffForPath, commonParentDirectory, sanitizeRelativePath} from './path.js'
+import {describe, test, expect, vi} from 'vitest'
 
 describe('relativize', () => {
   test('relativizes the path', () => {
@@ -93,3 +93,53 @@ describe('sniffForPath', () => {
     expect(path).toStrictEqual('/path/to/project')
   })
 })
+
+describe('sanitizeRelativePath', () => {
+  test('strips traversal segments', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('a/../../b', warn)).toBe('b')
+    expect(warn).toHaveBeenCalled()
+  })
+
+  test('strips leading slashes (absolute Unix paths)', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('/etc/passwd', warn)).toBe('etc/passwd')
+    expect(warn).toHaveBeenCalled()
+  })
+
+  test('strips multiple leading slashes', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('//etc/passwd', warn)).toBe('etc/passwd')
+    expect(warn).toHaveBeenCalled()
+  })
+
+  test('strips Windows drive letters', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('C:/Windows/System32', warn)).toBe('Windows/System32')
+    expect(warn).toHaveBeenCalled()
+  })
+
+  test('handles Windows backslashes', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('C:\\Windows\\System32', warn)).toBe('Windows/System32')
+    expect(warn).toHaveBeenCalled()
+  })
+
+  test('collapses internal current directory markers', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('a/./b', warn)).toBe('a/b')
+    expect(warn).not.toHaveBeenCalled()
+  })
+
+  test('returns empty string for empty result', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('..', warn)).toBe('')
+    expect(warn).toHaveBeenCalled()
+  })
+
+  test('returns empty string for single slash', () => {
+    const warn = vi.fn()
+    expect(sanitizeRelativePath('/', warn)).toBe('')
+    expect(warn).toHaveBeenCalled()
+  })
+})

packages/cli-kit/src/public/node/path.ts

@@ -224,13 +224,20 @@ export function sanitizeRelativePath(input: string, warn: (msg: string) => void)
     if (seg === '..') {
       stripped = true
       stack.pop()
-    } else if (seg !== '.') {
+    } else if (seg === '.' || seg === '') {
+      // Skip empty segments (leading/multiple slashes) and current directory markers.
+      // This prevents absolute paths like '/etc/passwd' from being treated as such.
+      if (seg === '') stripped = true
+    } else if (/^[a-zA-Z]:$/.test(seg)) {
+      // Skip Windows drive letters (e.g. 'C:') to prevent escaping to other drives.
+      stripped = true
+    } else {
       stack.push(seg)
     }
   }
   const result = stack.join('/')
   if (stripped) {
-    warn(`Warning: path '${input}' contains '..' traversal — sanitized to '${result || '.'}'\n`)
+    warn(`Warning: path '${input}' contains traversal or absolute segments — sanitized to '${result || '.'}'\n`)
   }
   return result
 }