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111 lines
4.0 KiB
Markdown
111 lines
4.0 KiB
Markdown
# simple-scrypt
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[](https://godoc.org/github.com/elithrar/simple-scrypt) [](https://travis-ci.org/elithrar/simple-scrypt)
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simple-scrypt provides a convenience wrapper around Go's existing
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[scrypt](http://golang.org/x/crypto/scrypt) package that makes it easier to
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securely derive strong keys ("hash user passwords"). This library allows you to:
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* Generate a scrypt derived key with a crytographically secure salt and sane
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default parameters for N, r and p.
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* Upgrade the parameters used to generate keys as hardware improves by storing
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them with the derived key (the scrypt spec. doesn't allow for this by
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default).
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* Provide your own parameters (if you wish to).
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The API closely mirrors Go's [bcrypt](https://golang.org/x/crypto/bcrypt)
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library in an effort to make it easy to migrate—and because it's an easy to grok
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API.
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## Example
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simple-scrypt doesn't try to re-invent the wheel or do anything "special". It
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wraps the `scrypt.Key` function as thinly as possible, generates a
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crytographically secure salt for you using Go's `crypto/rand` package, and
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returns the derived key with the parameters prepended:
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```go
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package main
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import(
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"fmt"
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"log"
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"github.com/elithrar/simple-scrypt"
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)
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func main() {
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// e.g. r.PostFormValue("password")
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passwordFromForm := "prew8fid9hick6c"
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// Generates a derived key of the form "N$r$p$salt$dk" where N, r and p are defined as per
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// Colin Percival's scrypt paper: http://www.tarsnap.com/scrypt/scrypt.pdf
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// scrypt.Defaults (N=16384, r=8, p=1) makes it easy to provide these parameters, and
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// (should you wish) provide your own values via the scrypt.Params type.
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hash, err := scrypt.GenerateFromPassword([]byte(passwordFromForm), scrypt.DefaultParams)
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if err != nil {
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log.Fatal(err)
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}
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// Print the derived key with its parameters prepended.
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fmt.Printf("%s\n", hash)
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// Uses the parameters from the existing derived key. Return an error if they don't match.
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err := scrypt.CompareHashAndPassword(hash, []byte(passwordFromForm))
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if err != nil {
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log.Fatal(err)
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}
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}
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```
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## Upgrading Parameters
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Upgrading derived keys from a set of parameters to a "stronger" set of parameters
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as hardware improves, or as you scale (and move your auth process to separate
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hardware), can be pretty useful. Here's how to do it with simple-scrypt:
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```go
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func main() {
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// SCENE: We've successfully authenticated a user, compared their submitted
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// (cleartext) password against the derived key stored in our database, and
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// now want to upgrade the parameters (more rounds, more parallelism) to
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// reflect some shiny new hardware we just purchased. As the user is logging
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// in, we can retrieve the parameters used to generate their key, and if
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// they don't match our "new" parameters, we can re-generate the key while
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// we still have the cleartext password in memory
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// (e.g. before the HTTP request ends).
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current, err := scrypt.Cost(hash)
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if err != nil {
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log.Fatal(err)
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}
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// Now to check them against our own Params struct (e.g. using reflect.DeepEquals)
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// and determine whether we want to generate a new key with our "upgraded" parameters.
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slower := scrypt.Params{
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N: 32768,
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R: 8,
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P: 2,
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SaltLen: 16,
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DKLen: 32,
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}
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if !reflect.DeepEqual(current, slower) {
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// Re-generate the key with the slower parameters
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// here using scrypt.GenerateFromPassword
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}
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}
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```
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## TO-DO:
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The following features are planned. PRs are welcome.
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- [x] Tag a release build.
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- [x] Automatically calculate "optimal" values for N, r, p similar [to the Ruby scrypt library](https://github.com/pbhogan/scrypt/blob/master/lib/scrypt.rb#L97-L146)
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e.g. `func Calibrate(duration int, mem int, fallback Params) (Params, error)`
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- contributed thanks to @tgulacsi.
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## License
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MIT Licensed. See LICENSE file for details.
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