fix: sanitize package name in linked-strategy path construction

workspaces/arborist/lib/arborist/isolated-reifier.js

@@ -4,6 +4,7 @@ const { join } = require('node:path')
 const { depth } = require('treeverse')
 const crypto = require('node:crypto')
 const { IsolatedNode, IsolatedLink } = require('../isolated-classes.js')
+const nameFromFolder = require('@npmcli/name-from-folder')
 
 // generate short hash key based on the dependency tree starting at this node
 const getKey = (startNode) => {
@@ -151,11 +152,14 @@ module.exports = cls => class IsolatedReifier extends cls {
     this.#externalProxies.set(node, result)
     await this.#assignCommonProperties(node, result, !node.hasShrinkwrap)
     if (node.hasShrinkwrap) {
+      // strip any path traversal from package.json name fields before they hit path.join below
+      /* istanbul ignore next - packageName is always set for real packages */
+      const safeName = nameFromFolder(node.packageName || node.path)
       const dir = join(
         node.root.path,
         'node_modules',
         '.store',
-        `${node.packageName}@${node.version}`
+        `${safeName}@${node.version}`
       )
       mkdirSync(dir, { recursive: true })
       // TODO this approach feels wrong and shouldn't be necessary for shrinkwraps
@@ -198,7 +202,8 @@ module.exports = cls => class IsolatedReifier extends cls {
     result.id = this.counter++
     /* istanbul ignore next - packageName is always set for real packages */
     result.name = result.isWorkspace ? (node.packageName || node.name) : node.name
-    result.packageName = node.packageName || node.name
+    // strip any path traversal from package.json name fields before they hit path.join below
+    result.packageName = nameFromFolder(node.packageName || node.path)
     result.package = { ...node.package }
     result.package.bundleDependencies = undefined
 

workspaces/arborist/lib/isolated-classes.js

@@ -104,6 +104,11 @@ class IsolatedNode {
     return !!(hasInstallScript || install || preinstall || postinstall)
   }
 
+  /* istanbul ignore next -- emulate lib/node.js */
+  get packageName () {
+    return this.package.name || null
+  }
+
   get version () {
     return this.package.version
   }

workspaces/arborist/test/arborist/reify.js

@@ -4065,6 +4065,128 @@ t.test('workspace installs retain existing versions with newer package specs', a
     'another-cool-package package.json should be updated to abbrev@1.0.4')
 })
 
+for (const poisoned of ['../../../escape-target', '@evil/../../../escape-target']) {
+  t.test(`install strategy linked sanitizes traversal in lockfile name (${poisoned})`, async t => {
+    // a poisoned lockfile name field would otherwise escape node_modules/.store
+    const testDir = t.testdir({
+      'package.json': JSON.stringify({
+        dependencies: {
+          abbrev: '1.1.1',
+        },
+      }),
+      'package-lock.json': JSON.stringify({
+        lockfileVersion: 3,
+        requires: true,
+        packages: {
+          '': {
+            dependencies: {
+              abbrev: '1.1.1',
+            },
+          },
+          'node_modules/abbrev': {
+            name: poisoned,
+            version: '1.1.1',
+            resolved: 'https://registry.npmjs.org/abbrev/-/abbrev-1.1.1.tgz',
+            integrity: 'sha512-nne9/IiQ/hzIhY6pdDnbBtz7DjPTKrY00P/zvPSm5pOFkl6xuGrGnXn/VtTNNfNtAfZ9/1RtehkszU9qcTii0Q==',
+          },
+        },
+      }),
+    })
+
+    const arb = new Arborist({
+      path: testDir,
+      registry: 'https://registry.npmjs.org',
+      cache: resolve(testDir, 'cache'),
+      installStrategy: 'linked',
+      packageLockOnly: true,
+    })
+    await arb.reify({ installStrategy: 'linked', packageLockOnly: true })
+
+    const external = arb.idealGraph.external
+    t.equal(external.length, 1, 'one external dep planned')
+
+    const pkgName = external[0].packageName
+    t.notMatch(pkgName, /\.\./, 'packageName has no traversal segments')
+    t.ok(!pkgName.includes('/') || pkgName.startsWith('@'),
+      'packageName is a single segment (or @scope/name)')
+
+    // joining the sanitized name into the .store layout must not escape
+    const storePrefix = resolve(testDir, 'node_modules/.store/key/node_modules')
+    const projected = resolve(storePrefix, pkgName)
+    t.ok(projected.startsWith(storePrefix), 'projected path stays inside .store')
+
+    // belt-and-suspenders: nothing should have been written outside testDir,
+    // even if a future change starts materializing paths during reify
+    t.notOk(fs.existsSync(resolve(testDir, '..', 'escape-target')),
+      'no escape-target leaked one level above testDir')
+    t.notOk(fs.existsSync(resolve(testDir, '..', '..', 'escape-target')),
+      'no escape-target leaked two levels above testDir')
+    t.notOk(fs.existsSync(resolve(testDir, '..', '..', '..', 'escape-target')),
+      'no escape-target leaked three levels above testDir')
+  })
+}
+
+for (const poisoned of ['../../../escape-target', '@evil/../../../escape-target']) {
+  t.test(`install strategy linked sanitizes traversal in shrinkwrapped lockfile name (${poisoned})`, async t => {
+    // the hasShrinkwrap branch in #externalProxy materializes
+    // node_modules/.store/<name>@<version> via mkdirSync before any other
+    // check, so a poisoned name in a shrinkwrapped entry would escape
+    // node_modules/.store on disk without sanitization
+    const testDir = t.testdir({
+      'package.json': JSON.stringify({
+        dependencies: {
+          abbrev: '1.1.1',
+        },
+      }),
+      'package-lock.json': JSON.stringify({
+        lockfileVersion: 3,
+        requires: true,
+        packages: {
+          '': {
+            dependencies: {
+              abbrev: '1.1.1',
+            },
+          },
+          'node_modules/abbrev': {
+            name: poisoned,
+            version: '1.1.1',
+            hasShrinkwrap: true,
+            resolved: 'https://registry.npmjs.org/abbrev/-/abbrev-1.1.1.tgz',
+            integrity: 'sha512-nne9/IiQ/hzIhY6pdDnbBtz7DjPTKrY00P/zvPSm5pOFkl6xuGrGnXn/VtTNNfNtAfZ9/1RtehkszU9qcTii0Q==',
+          },
+        },
+      }),
+    })
+
+    const arb = new Arborist({
+      path: testDir,
+      registry: 'https://registry.npmjs.org',
+      cache: resolve(testDir, 'cache'),
+      installStrategy: 'linked',
+      packageLockOnly: true,
+    })
+    // pacote.extract may fail in this offline test setup; the mkdirSync that
+    // runs before it is what we care about and runs unconditionally
+    try {
+      await arb.reify({ installStrategy: 'linked', packageLockOnly: true })
+    } catch {
+      // expected in offline test setup
+    }
+
+    // the sanitized store entry must land inside testDir/node_modules/.store
+    t.ok(fs.existsSync(resolve(testDir, 'node_modules/.store/escape-target@1.1.1')),
+      'sanitized .store/escape-target@1.1.1 created inside the project')
+
+    // and no escape-target@1.1.1 directory should appear above testDir
+    t.notOk(fs.existsSync(resolve(testDir, '..', 'escape-target@1.1.1')),
+      'no escape-target@1.1.1 leaked one level above testDir')
+    t.notOk(fs.existsSync(resolve(testDir, '..', '..', 'escape-target@1.1.1')),
+      'no escape-target@1.1.1 leaked two levels above testDir')
+    t.notOk(fs.existsSync(resolve(testDir, '..', '..', '..', 'escape-target@1.1.1')),
+      'no escape-target@1.1.1 leaked three levels above testDir')
+  })
+}
+
 t.test('externalOptionalDependencies excludes inert optional node with installStrategy linked', async t => {
   const testDir = t.testdir({
     'package.json': JSON.stringify({