87 lines
2.6 KiB
Markdown
87 lines
2.6 KiB
Markdown
# go-passwd
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Its a multi password type checker. Using the [PHC string format](https://github.com/P-H-C/phc-string-format/blob/master/phc-sf-spec.md) we can identify a password hashing format from the prefix `$name$` and then dispatch the hashing or checking to its specific format.
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# Example
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Here is an example of usage:
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```go
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// Example of upgrading password hash to a greater complexity.
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//
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// Note: This example uses very unsecure hash functions to allow for predictable output. Use of argon2.Argon2id or scrypt.Scrypt2 for greater hash security is recommended.
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func Example() {
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pass := []byte("my_pass")
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hash := []byte("$1$81ed91e1131a3a5a50d8a68e8ef85fa0")
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pwd := passwd.New(
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argon2.Argon2id, // first is preferred type.
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&unix.MD5{},
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)
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_, err := pwd.Passwd(pass, hash)
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if err != nil {
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fmt.Println("fail: ", err)
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return
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}
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// Check if we want to update.
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if !pwd.IsPreferred(hash) {
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newHash, err := pwd.Passwd(pass, nil)
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if err != nil {
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fmt.Println("fail: ", err)
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return
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}
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fmt.Println("new hash:", string(newHash)[:31], "...")
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}
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// Output:
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// new hash: $argon2id$v=19,m=65536,t=1,p=4$ ...
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}
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```
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https://github.com/sour-is/go-passwd/blob/main/passwd_test.go#L40-L68
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This shows how one would set a preferred hashing type and if the current version of ones password is not the preferred type updates it to enhance the security of the hashed password when someone logs in.
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# Fallthrough
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> Hold up now, that example hash doesn’t have a `$` prefix!
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Well for this there is the option for a hash type to set itself as a fall through if a matching hash doesn’t exist. This is good for legacy password types that don’t follow the convention.
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```go
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func (p *plainPasswd) ApplyPasswd(passwd *passwd.Passwd) {
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passwd.Register("plain", p)
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passwd.SetFallthrough(p)
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}
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```
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https://github.com/sour-is/go-passwd/blob/main/passwd_test.go#L28-L31
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# Custom Preference Checks
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Circling back to the `IsPreferred` method. A hasher can define its own `IsPreferred` method that will be called to check if the current hash meets the complexity requirements. This is good for updating the password hashes to be more secure over time.
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```go
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func (p *Passwd) IsPreferred(hash []byte) bool {
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_, algo := p.getAlgo(hash)
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if algo != nil && algo == p.d {
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// if the algorithm defines its own check for preference.
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if ck, ok := algo.(interface{ IsPreferred([]byte) bool }); ok {
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return ck.IsPreferred(hash)
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}
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return true
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}
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return false
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}
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```
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https://github.com/sour-is/go-passwd/blob/main/passwd.go#L62-L74
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Example: https://github.com/sour-is/go-passwd/blob/main/pkg/argon2/argon2.go#L104-L133
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