ae769f52a1
Concurrent enroll-url launches could both pass the enrollment
marker check and run overlapping elevated installs, racing on
LoadOrExchangeAPIKey and overwriting agent.key.
Add an exclusive flock on {configDir}/enrolling.lock for the
full install path and re-check IsEnrolled under that lock so
only one install exchanges a token and configures the device.
Signed-off-by: Ludovic Vielle <ludovic@probo.com>
85 lines
3.1 KiB
Go
85 lines
3.1 KiB
Go
// Copyright (c) 2026 Probo Inc <hello@probo.com>.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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package deviceagent
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import (
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"fmt"
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"os"
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"path/filepath"
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)
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const (
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// EnrollmentLockFileName serializes concurrent LoadOrExchangeAPIKey
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// calls that exchange enrollment tokens and write agent.key. It lives
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// under EnrollmentRunDir so a reboot clears it with the run tree.
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EnrollmentLockFileName = "enrolling.lock"
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// enrollmentLockMode is owner-only; only the elevated install path
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// creates and holds this lock.
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enrollmentLockMode = 0o600
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)
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// EnrollmentLockPath returns the absolute path of the enrollment lock file
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// under EnrollmentRunDir for the given state directory.
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func EnrollmentLockPath(configDir string) string {
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return filepath.Join(EnrollmentRunDir(configDir), EnrollmentLockFileName)
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}
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// AcquireEnrollmentLock takes an exclusive lock on enrolling.lock under
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// EnrollmentRunDir(configDir) for the duration of credential exchange. The
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// returned release function unlocks and closes the lock file. The path is
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// left in place so waiters that already opened the inode stay serialized
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// with later acquirers; the kernel releases the lock on close (including
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// after crashes). Callers must not unlink this path while a holder may
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// exist.
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func AcquireEnrollmentLock(configDir string) (release func(), err error) {
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runDir := EnrollmentRunDir(configDir)
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if err := os.MkdirAll(runDir, EnrollmentRunDirMode); err != nil {
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return nil, fmt.Errorf("cannot create enrollment run dir: %w", err)
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}
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if err := os.Chmod(runDir, EnrollmentRunDirMode); err != nil {
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return nil, fmt.Errorf("cannot set enrollment run dir permissions: %w", err)
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}
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path := EnrollmentLockPath(configDir)
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file, err := os.OpenFile(
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path,
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os.O_RDWR|os.O_CREATE,
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enrollmentLockMode,
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)
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if err != nil {
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return nil, fmt.Errorf("cannot open enrollment lock: %w", err)
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}
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if err := lockFileExclusive(file); err != nil {
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_ = file.Close()
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return nil, fmt.Errorf("cannot acquire enrollment lock: %w", err)
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}
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return func() {
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_ = unlockFile(file)
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_ = file.Close()
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}, nil
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}
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