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Roll Your Own Auth or Use a Provider? A Solo Developer Decision Guide

Author
Vishal Maurya
Published on
Reading time
4 min read

Overview

You are building a SaaS product alone, and "login" looks like a weekend task. Then you list what it involves: password storage, email verification, resets, rate limiting, sessions, social login, maybe MFA. Should you build it, or hand it to a provider?

This guide lays out what self-built auth really requires and when a provider is the safer default.

1. What Rolling Your Own Actually Includes

Sign-in is the visible part. Behind it sits a list of features that each have known failure modes:

  • Password hashing and storage.
  • Account creation with email verification.
  • Password reset and email change flows.
  • Session or token management, logout, and revocation.
  • Brute-force and credential-stuffing protection.
  • Account enumeration prevention.
  • Optional: MFA, social login, SSO, audit logs.

None of these are exotic, but each one is easy to implement almost correctly. That is the risk.

2. Password Hashing Done Properly

Never store plain or fast-hashed passwords. Use a purpose-built password hashing algorithm, such as Argon2id, scrypt, or bcrypt, with parameters recommended by OWASP at the time you build. Do not invent your own scheme, and do not use plain SHA-256 or MD5.

from argon2 import PasswordHasher
from argon2.exceptions import VerifyMismatchError

ph = PasswordHasher()


def hash_password(password: str) -> str:
    return ph.hash(password)


def verify_password(stored_hash: str, password: str) -> bool:
    try:
        ph.verify(stored_hash, password)
    except VerifyMismatchError:
        return False
    if ph.check_needs_rehash(stored_hash):
        # Re-hash with current parameters and save the new hash.
        pass
    return True

Review the library defaults against the current OWASP Password Storage Cheat Sheet rather than assuming they are enough.

3. Rate Limiting and Enumeration

A login form without throttling invites credential stuffing. Limit attempts per account and per IP, add progressive delays or lockouts carefully (hard lockouts can become a denial-of-service tool), and consider checking passwords against known-breached lists.

Return the same message for "unknown email" and "wrong password", and make login, registration, and reset responses similar in content and timing where practical. Otherwise an attacker can learn which emails have accounts.

Attackers often skip the password and go after the reset path. A safe reset flow typically:

  • Generates a long random token with a cryptographically secure generator.
  • Stores only a hash of the token, with a short expiry.
  • Makes the token single-use.
  • Does not reveal whether the email exists.
  • Invalidates existing sessions after the password changes.
  • Sends the link only to the address on file.

Email change and MFA reset deserve the same care, since they are alternate account takeover routes.

5. When a Provider Is the Safer Default

A managed provider or well-maintained auth library is usually the better choice when:

  • You are a solo developer with limited time for security maintenance.
  • You need social login, SSO, or MFA soon.
  • Your customers may ask for SAML or enterprise SSO later.
  • You would otherwise be on call for credential-related incidents.

A provider does not remove your responsibility. You still must validate tokens properly, configure redirect URIs strictly, handle authorization in your own code, and plan for the provider's outages and pricing changes.

6. When Building It Yourself Can Make Sense

Using your framework's mature auth system or a library is different from writing everything from scratch. Django's built-in auth, for example, handles hashing, sessions, and reset tokens with a long track record. Building on that is generally more defensible than a custom implementation.

Self-built can be reasonable if you have strict data residency or cost constraints, a simple internal tool, or the expertise to maintain it. Plan for ongoing work: dependency updates, parameter upgrades, and incident response.

7. Questions to Decide

  • Do I need MFA, social login, or SSO within the next year?
  • Can I afford to be the one handling a credential breach?
  • How hard would it be to migrate users away from a provider later? Check whether password hashes can be exported.
  • What does the provider cost at my expected user count?
  • Is user data allowed to leave my infrastructure?

Conclusion

For most solo developers, a mature framework auth system or a reputable provider is safer than custom code. If you do build parts yourself, get hashing, rate limiting, and reset flows right, and review them against OWASP guidance.

If you want help choosing an approach, migrating between options, or reviewing an existing login system, I can help. Contact me.

Additional Resources

  • OWASP Authentication Cheat Sheet
  • OWASP Password Storage Cheat Sheet
  • OWASP Forgot Password Cheat Sheet