PBKDF2 Hash (Django / passlib format) Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching pbkdf2 hash (django / passlib format), ported and verified for Go. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// PBKDF2 Hash (Django / passlib format)
// ReDoS-safe | RegexVault — Security > Password Formats

package validation

import "regexp"

var pbkdf2HashDjangoPasslibFormatRe = regexp.MustCompile(`^pbkdf2_sha(256|512)\$([0-9]+)\$([A-Za-z0-9+/=]{1,32})\$([A-Za-z0-9+/=]{43,86})$`)

func ValidatePbkdf2HashDjangoPasslibFormat(s string) bool {
    return pbkdf2HashDjangoPasslibFormatRe.MatchString(s)
}

// Example
// fmt.Println(ValidatePbkdf2HashDjangoPasslibFormat("pbkdf2_sha256$390000$abcdefghijklmnop$abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMN01234567890=")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Password Formats category and carries a ReDoS-safe certification. That matters for Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Format: algorithm + $ + iterations + $ + salt (base64) + $ + hash (base64). Django default uses sha256 with 390000 iterations (Django 4.2). NIST SP 800-63b recommends at least 10000 iterations — modern systems should use much higher. SHA-512 is preferred over SHA-256.