go-mockid/mockid/api/common.go

package api

import (
	"bytes"
	"crypto/sha256"
	"encoding/binary"
	"encoding/json"
	"errors"
	"io"
	"log"
	"math/rand"
	mathrand "math/rand"
	"net/http"
)

// options are the things that we may need to know about a request to fulfill it properly
type options struct {
	KeyType string `json:"kty"`
	Seed    int64  `json:"-"`
	SeedStr string `json:"seed"`
}

// this shananigans is only for testing and debug API stuff
func (o *options) nextRand() *mathrand.Rand {
	if 0 == o.Seed {
		panic(errors.New("called nextRand impossibly"))
		return nil
	}
	return rand.New(rand.NewSource(o.Seed))
}

func (o *options) nextReader() io.Reader {
	if 0 == o.Seed {
		return RandomReader
	}
	return rand.New(rand.NewSource(o.Seed))
}

func getOpts(r *http.Request) (*options, error) {
	tok := make(map[string]interface{})
	decoder := json.NewDecoder(r.Body)
	err := decoder.Decode(&tok)
	if nil != err && io.EOF != err {
		log.Printf("json decode error: %s", err)
		return nil, errors.New("Bad Request: invalid json body")
	}
	defer r.Body.Close()

	var seed int64
	seedStr, _ := tok["seed"].(string)
	if "" != seedStr {
		if len(seedStr) > 256 {
			return nil, errors.New("Bad Request: base64 seed should be <256 characters (and is truncated to 64-bits anyway)")
		}
		b := sha256.Sum256([]byte(seedStr))
		seed, _ = binary.ReadVarint(bytes.NewReader(b[0:8]))
	}

	opts := &options{
		Seed: seed,
	}

	var n int
	if 0 != seed {
		n = opts.nextRand().Intn(2)
	} else {
		n = rand.Intn(2)
	}

	opts.KeyType, _ = tok["kty"].(string)
	if "" == opts.KeyType {
		if 0 == n {
			opts.KeyType = "RSA"
		} else {
			opts.KeyType = "EC"
		}
	}

	return opts, nil
}