How Can I Safely Drop Root Privileges After Binding to Port 80 in a Go Web Server?

Privilege Dropping with Golang in v1.7

Problem:

Designing a customized web server in Go requires initial root privileges to bind to port 80. However, it is desirable to relinquish root privileges as quickly as possible.

Background:

Go's syscall.SetUid() is unavailable due to issue #1435, making direct privilege dropping impractical. Alternative methods like IPtables introduce security vulnerabilities.

Solution:

The Go language offers a solution to this problem without relying on external tools or workarounds. By implementing custom code, we can bind to the required port and subsequently drop root privileges.

Implementation:

1. Bind to the desired port.
2. Check the current user ID (UID).
3. If the UID is 0 (root), identify the intended user and their associated UID and GID.
4. Utilize glibc calls setuid() and setgid() to modify the process's UID and GID accordingly.

Benefits:

This approach allows for flexible privilege management. For instance, during development, the application can run on a non-root user and high port without additional configurations.

Example Code:

package main

import (
    "crypto/tls"
    "log"
    "net/http"
    "os/user"
    "strconv"
    "syscall"
)

func main() {
    //... (continued)
}

By following these steps, you can effectively drop privileges in your Go application, ensuring a secure and user-specific execution environment.

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