fix(git): Do not drop uid/gid when executing in root-owned directory

Fix: npm/cli#624

Infer the ownership of a git command invocation based on the cwd, if one is
specified.

lib/util/git.js

@@ -16,6 +16,7 @@ const promiseRetry = require('promise-retry')
 const uniqueFilename = require('unique-filename')
 const which = BB.promisify(require('which'))
 const semver = require('semver')
+const inferOwner = require('infer-owner')
 
 const GOOD_ENV_VARS = new Set([
   'GIT_ASKPASS',
@@ -181,10 +182,24 @@ function revs (repo, opts) {
   })
 }
 
+// infer the owner from the cwd git is operating in, if not the
+// process cwd, but only if we're root.
+// See: https://github.com/npm/cli/issues/624
+module.exports._cwdOwner = cwdOwner
+function cwdOwner (gitOpts, opts) {
+  const isRoot = process.getuid && process.getuid() === 0
+  if (!isRoot || !gitOpts.cwd) { return Promise.resolve() }
+
+  return BB.resolve(inferOwner(gitOpts.cwd).then(owner => {
+    gitOpts.uid = owner.uid
+    gitOpts.gid = owner.gid
+  }))
+}
+
 module.exports._exec = execGit
 function execGit (gitArgs, gitOpts, opts) {
   opts = optCheck(opts)
-  return checkGit(opts).then(gitPath => {
+  return BB.resolve(cwdOwner(gitOpts, opts).then(() => checkGit(opts).then(gitPath => {
     return promiseRetry((retry, number) => {
       if (number !== 1) {
         opts.log.silly('pacote', 'Retrying git command: ' + gitArgs.join(' ') + ' attempt # ' + number)
@@ -202,13 +217,13 @@ function execGit (gitArgs, gitOpts, opts) {
       maxTimeout: opts['fetch-retry-maxtimeout'],
       minTimeout: opts['fetch-retry-mintimeout']
     })
-  })
+  })))
 }
 
 module.exports._spawn = spawnGit
 function spawnGit (gitArgs, gitOpts, opts) {
   opts = optCheck(opts)
-  return checkGit(opts).then(gitPath => {
+  return BB.resolve(cwdOwner(gitOpts, opts).then(() => checkGit(opts).then(gitPath => {
     return promiseRetry((retry, number) => {
       if (number !== 1) {
         opts.log.silly('pacote', 'Retrying git command: ' + gitArgs.join(' ') + ' attempt # ' + number)
@@ -231,7 +246,7 @@ function spawnGit (gitArgs, gitOpts, opts) {
         return stdout
       })
     }, opts.retry)
-  })
+  })))
 }
 
 module.exports._mkOpts = mkOpts

test/git.cwd-owner.js

@@ -0,0 +1,75 @@
+'use strict'
+const t = require('tap')
+
+process.getuid = () => 0
+process.getgid = () => 0
+
+const requireInject = require('require-inject')
+const fs = require('fs')
+const { _cwdOwner: cwdOwner } = requireInject('../lib/util/git.js', {
+  fs: Object.assign({}, fs, {
+    lstat: (path, cb) => {
+      if (path === '/var/root/.npm/_cacache/bleep/boop') {
+        return process.nextTick(() => cb(null, { uid: 0, gid: 0 }))
+      }
+      if (path === '/home/user/.npm/_cacache/bleep/boop') {
+        return process.nextTick(() => cb(null, { uid: 69, gid: 420 }))
+      }
+      fs.lstat(path, cb)
+    },
+    stat: (path, cb) => {
+      if (path === '/var/root/.npm/_cacache/bleep/boop') {
+        return process.nextTick(() => cb(null, { uid: 0, gid: 0 }))
+      }
+      if (path === '/home/user/.npm/_cacache/bleep/boop') {
+        return process.nextTick(() => cb(null, { uid: 69, gid: 420 }))
+      }
+      fs.stat(path, cb)
+    }
+  })
+})
+
+t.test('running in root-owned folder, but with non-root uid/gid opts', t => {
+  const gitOpts = {
+    cwd: '/var/root/.npm/_cacache/bleep/boop'
+  }
+  const opts = {
+    uid: 69,
+    gid: 420
+  }
+  return cwdOwner(gitOpts, opts).then(() => {
+    t.strictSame(gitOpts, {
+      cwd: '/var/root/.npm/_cacache/bleep/boop',
+      uid: 0,
+      gid: 0
+    })
+  })
+})
+
+t.test('running in non-root-owned folder', t => {
+  const gitOpts = {
+    cwd: '/home/user/.npm/_cacache/bleep/boop'
+  }
+  const opts = {
+    uid: 12,
+    gid: 34
+  }
+  return cwdOwner(gitOpts, opts).then(() => {
+    t.strictSame(gitOpts, {
+      cwd: '/home/user/.npm/_cacache/bleep/boop',
+      uid: 69,
+      gid: 420
+    })
+  })
+})
+
+t.test('running without a cwd', t => {
+  const gitOpts = {}
+  const opts = {
+    uid: 12,
+    gid: 34
+  }
+  return cwdOwner(gitOpts, opts).then(() => {
+    t.strictSame(gitOpts, {})
+  })
+})