go-mockid/mockid/route.go

package mockid

import (
	"crypto/sha1"
	"crypto/sha256"
	"crypto/sha512"
	"crypto/subtle"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"git.coolaj86.com/coolaj86/go-mockid/kvdb"
	"git.coolaj86.com/coolaj86/go-mockid/mockid/api"
	"git.coolaj86.com/coolaj86/go-mockid/xkeypairs"
	"git.rootprojects.org/root/keypairs"
	"git.rootprojects.org/root/keypairs/keyfetch"

	"github.com/google/uuid"
	ua "github.com/mileusna/useragent"
)

var errTokenNotVerified = apiError{"token has not been verified"}
var errUsedToken = apiError{"token has already been used"}
var errInvalidEmail = apiError{"invalid email address"}

// API Errors
type serverError struct {
	error string
}

func (e serverError) Error() string {
	return e.error
}

type apiError struct {
	error string
}

func (e apiError) Error() string {
	return e.error
}

type HTTPResponse struct {
	Error   string `json:"error,omitempty"`
	Code    string `json:"code,omitempty"`
	Success bool   `json:"success"`
}

type TokenResponse struct {
	Receipt string `json:"receipt"`
	HTTPResponse
}

type OTPResponse struct {
	OTP
	HTTPResponse
}

type Contact struct {
	Email    string   `json:"email"`
	Subjects []string `json:"subjects"`
}

type Subject struct {
	Subject string               `json:"subject"`
	Emails  map[string]time.Time `json:"emails"`
}

var privKeyJWKPath string
var tokenPrefix string

// Route returns an HTTP Mux containing the full API
func Route(jwksPrefix string, privkey keypairs.PrivateKey) http.Handler {
	Init()

	contactPrefix := jwksPrefix + "/contacts"
	contactKV := kvdb.KVDB{
		Prefix: contactPrefix,
		Ext:    "eml.json",
	}

	subjectPrefix := jwksPrefix + "/subjects"
	subjectKV := kvdb.KVDB{
		Prefix: subjectPrefix,
		Ext:    "sub.json",
	}

	// TODO get from main()
	tokenPrefix = jwksPrefix + "/tokens"
	for _, pre := range []string{tokenPrefix, contactPrefix, subjectPrefix} {
		if err := os.MkdirAll(pre, 0750); nil != err {
			panic(err)
		}
	}
	pubkey := keypairs.NewPublicKey(privkey.Public())

	privKeyJWKPath = jwksPrefix + "/private/priv.jwk.json"
	signingKey, err := xkeypairs.ParsePrivateKeyFile(privKeyJWKPath)
	if nil != err {
		signingKey = xkeypairs.GenPrivKey(&xkeypairs.KeyOptions{})
		_ = os.MkdirAll(jwksPrefix+"/private", 0750)
		b := xkeypairs.MarshalJWKPrivateKey(signingKey)
		if err := ioutil.WriteFile(privKeyJWKPath, b, 0600); nil != err {
			panic(err)
		}
	}
	signingPub := keypairs.NewPublicKey(signingKey.Public())
	//signingKid := keypairs.ThumbprintPublicKey(signingPub)

	http.HandleFunc("/api/new-hashcash", func(w http.ResponseWriter, r *http.Request) {
		if "POST" != r.Method {
			http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
			return
		}

		indexURL := getBaseURL(r) + "/api/directory"
		w.Header().Set("Link", "<"+indexURL+">;rel=\"index\"")

		w.Header().Set("Date", time.Now().Format(http.TimeFormat))
		// disable caching in every possible way
		w.Header().Set("Expires", time.Now().Format(http.TimeFormat))
		w.Header().Set("Cache-Control", "max-age=0, no-cache, no-store")
		w.Header().Set("Pragma", "no-cache")
		// add reasonable security options
		w.Header().Set("Strict-Transport-Security", "max-age=604800")
		w.Header().Set("X-Frame-Options", "DENY")

		h := issueHashcash(w, r)
		b, _ := json.Marshal(h)
		w.Write(b)
	})

	http.HandleFunc("/api/authn/meta", func(w http.ResponseWriter, r *http.Request) {
		if "GET" != r.Method {
			http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
			return
		}

		query := r.URL.Query()
		contact := strings.Replace(strings.TrimPrefix(query.Get("contact"), "mailto:"), " ", "+", -1)
		if "" == contact {
			fmt.Println("meta: empty contact query")
			http.Error(w, "Bad Request", http.StatusBadRequest)
			b, _ := json.Marshal(&HTTPResponse{
				Error: "missing require query parameter 'contact'",
			})
			w.Write(b)
			return
		}

		contact, err = lintEmail(contact)
		if nil != err {
			b, _ := json.Marshal(&HTTPResponse{
				Error: err.Error(),
				Code:  "E_USER",
			})
			w.Write(b)
			return
		}

		_, ok, err := contactKV.Load(contact)
		if nil != err {
			fmt.Fprintf(os.Stderr, "meta: error loading contact: %s\n", err.Error())
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}
		if ok {
			b, _ := json.Marshal(&HTTPResponse{
				Success: true,
			})
			w.Write(b)
			return
		}

		b, _ := json.Marshal(&HTTPResponse{
			Error: "not found",
			Code:  "E_USER",
		})
		w.Write(b)
	})

	// TODO rename as challenge?
	http.HandleFunc("/api/authn/verify", func(w http.ResponseWriter, r *http.Request) {
		baseURL := getBaseURL(r)
		query := r.URL.Query()
		contact := strings.Replace(strings.TrimPrefix(query.Get("contact"), "mailto:"), " ", "+", -1)
		fmt.Println("contact:", contact)
		addr := strings.Split(r.RemoteAddr, ":")[0]
		receipt, err := startVerification(
			baseURL,
			contact,
			r.Header.Get("User-Agent"),
			addr,
		)

		if nil != err {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			msg, _ := json.Marshal(err.Error())
			fmt.Fprintf(w, `{"error":%s}`+"\n", msg)
			return
		}

		b, _ := json.Marshal(&TokenResponse{
			HTTPResponse: HTTPResponse{Success: true},
			Receipt:      receipt,
		})
		w.Write(b)
	})

	// TODO rename as present?
	http.HandleFunc("/api/authn/consume", func(w http.ResponseWriter, r *http.Request) {
		query := r.URL.Query()
		otpSecret := query.Get("secret")
		secret, b64err := base64.RawURLEncoding.DecodeString(otpSecret)
		receipt := query.Get("receipt")
		fmt.Println("secret:", otpSecret, secret, b64err)

		if (0 == len(secret) || nil != b64err) && "" == receipt {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			msg, _ := json.Marshal("missing token secret and/or token receipt")
			fmt.Fprintf(w, `{"error":%s}`+"\n", msg)
			return
		}

		addr := strings.Split(r.RemoteAddr, ":")[0]
		agent := r.Header.Get("User-Agent")
		var otp *OTP
		var err error
		if 0 != len(secret) && nil == b64err {
			if "" != receipt {
				_, rcpt := hashOTPSecret(secret)
				if rcpt != receipt {
					http.Error(w, "Bad Request", http.StatusBadRequest)
					fmt.Fprintf(w, "%s", "otp secret and receipt do not match")
					return
				}
			}
			otp, err = consumeOTPSecret("TODO", secret, agent, addr)
		} else if 0 != len(receipt) {
			otp, err = consumeOTPReceipt("TODO", receipt, agent, addr)
		}
		if nil != err {
			if errTokenNotVerified == err {
				b, _ := json.Marshal(&HTTPResponse{
					Error: err.Error(),
				})
				w.Write(b)
				return
			}
			// TODO propagate error types
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, "%s", err)
			return
		}

		var contact *Contact
		val, ok, err := contactKV.Load(otp.Email, &Contact{})
		if nil != err {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			fmt.Println("error loading contact:", err)
			fmt.Fprintf(w, "%s", err)
			return
		}

		if ok {
			contact = val.(*Contact)
		} else {
			// TODO c := Contacts.New(); c.Save();
			uuid, _ := uuid.NewRandom()
			uuidBin, _ := uuid.MarshalBinary()
			sub := base64.RawURLEncoding.EncodeToString(uuidBin)
			contact = &Contact{
				Email:    otp.Email,
				Subjects: []string{sub},
			}
			if err := contactKV.Store(otp.Email, contact); nil != err {
				fmt.Println("ERROR contactKV Store", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
				fmt.Fprintf(w, "%s", err)
				return
			}
			subject := &Subject{
				Subject: sub,
				Emails: map[string]time.Time{
					otp.Email: time.Now(),
				},
			}
			if err := subjectKV.Store(sub, subject); nil != err {
				fmt.Println("ERROR subjectKV Store", err)
				http.Error(w, "Internal Server Error", http.StatusInternalServerError)
				fmt.Fprintf(w, "%s", err)
				return
			}
		}

		var sub string
		if len(contact.Subjects) < 1 || len(contact.Subjects) > 1 {
			fmt.Printf("%#v\n", contact)
			if len(contact.Subjects) > 1 {
				fmt.Fprintf(os.Stderr, "TODO: give exchange token for multiple accounts\n")
			}
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			fmt.Fprintf(w, "%s", err)
			return
		}
		sub = contact.Subjects[0]

		uuid, _ := uuid.NewRandom()
		nonce, _ := uuid.MarshalBinary()
		baseURL := getBaseURL(r)
		tok, err := xkeypairs.SignClaims(
			signingKey,
			xkeypairs.Object{},
			xkeypairs.Object{
				"sub": sub,
				"iss": baseURL + "/",
				"jti": base64.RawURLEncoding.EncodeToString(nonce),
				"iat": time.Now().Unix(),
				"exp": "1h",
			},
		)
		if nil != err {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			fmt.Fprintf(w, "%s", err)
			return
		}
		otp.AccessToken = xkeypairs.JWSToJWT(tok)
		b, _ := json.Marshal(&OTPResponse{
			HTTPResponse: HTTPResponse{Success: true},
			OTP:          *otp,
		})
		w.Write(b)
	})

	http.HandleFunc("/api/authz/email", func(w http.ResponseWriter, r *http.Request) {
		token := r.Header.Get("Authorization")
		log.Printf("%s %s %s\n", r.Method, r.URL.Path, token)

		if "" == token {
			http.Error(
				w,
				"Bad Format: missing Authorization header and 'access_token' query",
				http.StatusBadRequest,
			)
			return
		}
		parts := strings.Split(token, " ")
		if 2 != len(parts) {
			http.Error(
				w,
				"Bad Format: expected Authorization header to be in the format of 'Bearer <Token>'",
				http.StatusBadRequest,
			)
			return
		}
		token = parts[1]

		inspected, err := verifyToken(token)
		if nil != err {
			http.Error(w, "Invalid Token: "+err.Error(), http.StatusBadRequest)
			return
		}
		if !inspected.Verified {
			http.Error(w, "bad token signature", http.StatusBadRequest)
			return
		}

		iss, _ := inspected.Payload["iss"].(string)
		baseURL := getBaseURL(r)
		if baseURL != strings.TrimSuffix(iss, "/") {
			http.Error(w, "unacceptable token issuer", http.StatusBadRequest)
			return
		}

		subject, _ := inspected.Payload["sub"].(string)
		value, ok, err := subjectKV.Load(subject, &Subject{})
		if nil != err {
			http.Error(w, "Server Error: "+err.Error(),
				http.StatusInternalServerError,
			)
			return
		}
		if !ok {
			http.Error(w, "Server Error: the user went missing... huh",
				http.StatusInternalServerError,
			)
			return
		}

		sub, ok := value.(*Subject)
		if !ok {
			http.Error(
				w,
				"Server Error: invalid data type",
				http.StatusInternalServerError,
			)
			return
		}

		var emails []string
		for k := range sub.Emails {
			emails = append(emails, k)
		}
		jsonb, _ := json.MarshalIndent(struct {
			Emails []string `json:"emails"`
		}{
			Emails: emails,
		}, "", "    ")

		fmt.Fprintf(w, string(jsonb)+"\n")
	})

	http.HandleFunc("/api/new-nonce", requireHashcash(func(w http.ResponseWriter, r *http.Request) {
		indexURL := getBaseURL(r) + "/api/directory"
		w.Header().Set("Link", "<"+indexURL+">;rel=\"index\"")

		w.Header().Set("Date", time.Now().Format(http.TimeFormat))
		// disable caching in every possible way
		w.Header().Set("Expires", time.Now().Format(http.TimeFormat))
		w.Header().Set("Cache-Control", "max-age=0, no-cache, no-store")
		w.Header().Set("Pragma", "no-cache")
		w.Header().Set("Strict-Transport-Security", "max-age=604800")

		w.Header().Set("X-Frame-Options", "DENY")

		issueNonce(w, r)
	}))

	http.HandleFunc("/api/test-hashcash", func(w http.ResponseWriter, r *http.Request) {
		if err := UseHashcash(r.Header.Get("Hashcash"), r.Host); nil != err {
			b, _ := json.Marshal(&HTTPResponse{
				Error: err.Error(),
			})
			w.Write(b)
			return
		}

		b, _ := json.Marshal(&HTTPResponse{
			Success: true,
		})
		w.Write(b)
	})

	type NewAccount struct {
		Contact              []string `json:"contact"`
		TermsOfServiceAgreed bool     `json:"termsOfServiceAgreed"`
	}

	http.HandleFunc("/api/new-account", func(w http.ResponseWriter, r *http.Request) {
		myURL := getBaseURL(r) + r.URL.Path

		jws := &xkeypairs.JWS{}

		decoder := json.NewDecoder(r.Body)
		if err := decoder.Decode(jws); nil != err {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			return
		}
		defer r.Body.Close()

		if err := jws.DecodeComponents(); nil != err {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, `{"error":%q}`+"\n", err)
			return
		}

		kid, _ := jws.Header["kid"].(string)
		if "" != kid {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, `{"error":"jws must include protected jwk, which is mutually exclusive from kid"}`+"\n")
			return
		}

		alg, _ := jws.Header["alg"].(string)
		if !strings.HasSuffix(alg, "256") {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, `{"error":"invalid jws protected algorithm"}`+"\n")
			return
		}

		nonce, _ := jws.Header["nonce"].(string)
		if !useNonce(nonce) {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, `{"error":"invalid jws protected nonce"}`+"\n")
			return
		}

		jwsURL, _ := jws.Header["url"].(string)
		if myURL != jwsURL {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, `{"error":"invalid jws protected target URL"}`+"\n")
			return
		}

		ok, err := xkeypairs.VerifyClaims(nil, jws)
		if nil != err || !ok {
			if nil != err {
				log.Printf("jws verify error: %s", err)
			}
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, `{"error":"could not verify JWS claims"}`+"\n")
			return
		}

		contacts, _ := jws.Claims["contact"].([]string)
		contact := ""
		if 1 == len(contacts) {
			contact = contacts[0]
		}

		baseURL := getBaseURL(r)
		addr := strings.Split(r.RemoteAddr, ":")[0]
		receipt, err := startVerification(
			baseURL,
			contact,
			r.Header.Get("User-Agent"),
			addr,
		)
		if nil != err {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			msg, _ := json.Marshal(err.Error())
			fmt.Fprintf(w, `{"error":%s}`+"\n", msg)
			return
		}

		fmt.Fprintf(w, `{ "success": true, "error": "", "receipt":, "%s" }%s`, receipt, "\n")
	})

	// TODO use chi
	http.HandleFunc("/verify/", requireNonce(func(w http.ResponseWriter, r *http.Request) {
		parts := strings.Split(r.URL.Path, "/")
		if 3 != len(parts) {
			http.Error(w, "invalid url path", http.StatusBadRequest)
			return
		}
		secret, err := base64.RawURLEncoding.DecodeString(parts[2])
		if nil != err {
			http.Error(w, "Bad Request", http.StatusBadRequest)
			fmt.Fprintf(w, "%s", err)
			return
		}
		addr := strings.Split(r.RemoteAddr, ":")[0]
		if _, err := consumeOTPSecret("TODO", secret, r.Header.Get("User-Agent"), addr); nil != err {
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			fmt.Fprintf(w, "%s", err)
			return
		}

		fmt.Fprintf(w, `{ "success": true, "error": "" }%s`, "\n")
	}))

	http.HandleFunc("/api/jwks", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s %s", r.Method, r.Host, r.URL.Path)
		if "POST" != r.Method {
			http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
			return
		}

		tok := make(map[string]interface{})
		decoder := json.NewDecoder(r.Body)
		err := decoder.Decode(&tok)
		if nil != err {
			http.Error(w, "Bad Request: invalid json", http.StatusBadRequest)
			return
		}
		defer r.Body.Close()

		// TODO better, JSON error messages
		if _, ok := tok["d"]; ok {
			http.Error(w, "Bad Request: private key", http.StatusBadRequest)
			return
		}

		kty, _ := tok["kty"].(string)
		switch kty {
		case "EC":
			postEC(jwksPrefix, tok, w, r)
		case "RSA":
			postRSA(jwksPrefix, tok, w, r)
		default:
			http.Error(w, "Bad Request: only EC and RSA keys are supported", http.StatusBadRequest)
			return
		}
	})

	http.HandleFunc("/access_token", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s\n", r.Method, r.URL.Path)
		_, _, token := GenToken(getBaseURL(r), privkey, r.URL.Query())
		fmt.Fprintf(w, token)
	})

	// TODO add /debug prefix
	http.HandleFunc("/debug/private.jwk.json", api.GeneratePrivateJWK)
	http.HandleFunc("/debug/priv.der", api.GeneratePrivateDER)
	http.HandleFunc("/debug/priv.pem", api.GeneratePrivatePEM)

	http.HandleFunc("/debug/public.jwk.json", api.GeneratePublicJWK)
	http.HandleFunc("/debug/pub.der", api.GeneratePublicDER)
	http.HandleFunc("/debug/pub.pem", api.GeneratePublicPEM)

	http.HandleFunc("/debug/jose.jws.json", api.SignJWS)
	http.HandleFunc("/debug/jose.jws.jwt", api.SignJWT)
	http.HandleFunc("/debug/verify", api.Verify)

	http.HandleFunc("/inspect_token", func(w http.ResponseWriter, r *http.Request) {
		token := r.Header.Get("Authorization")
		log.Printf("%s %s %s\n", r.Method, r.URL.Path, token)

		if "" == token {
			token = r.URL.Query().Get("access_token")
			if "" == token {
				http.Error(
					w,
					"Bad Format: missing Authorization header and 'access_token' query",
					http.StatusBadRequest,
				)
				return
			}
		} else {
			parts := strings.Split(token, " ")
			if 2 != len(parts) {
				http.Error(
					w,
					"Bad Format: expected Authorization header to be in the format of 'Bearer <Token>'",
					http.StatusBadRequest,
				)
				return
			}
			token = parts[1]
		}

		inspected, err := verifyToken(token)
		if nil != err {
			http.Error(w, "Invalid Token: "+err.Error(), http.StatusBadRequest)
			return
		}

		tokenB, _ := json.MarshalIndent(inspected, "", "    ")
		if nil != err {
			http.Error(
				w,
				"Bad Format: malformed token, or malformed jwk at issuer url",
				http.StatusInternalServerError,
			)
			return
		}
		fmt.Fprintf(w, string(tokenB)+"\n")
	})

	http.HandleFunc("/authorization_header", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s\n", r.Method, r.URL.Path)

		var header string
		headers, _ := r.URL.Query()["header"]
		if 0 == len(headers) {
			header = "Authorization"
		} else {
			header = headers[0]
		}

		var prefix string
		prefixes, _ := r.URL.Query()["prefix"]
		if 0 == len(prefixes) {
			prefix = "Bearer "
		} else {
			prefix = prefixes[0]
		}

		_, _, token := GenToken(getBaseURL(r), privkey, r.URL.Query())
		fmt.Fprintf(w, "%s: %s%s", header, prefix, token)
	})

	http.HandleFunc("/key.jwk.json", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s", r.Method, r.URL.Path)
		jwk := string(xkeypairs.MarshalJWKPrivateKey(privkey))
		jwk = strings.Replace(jwk, `{"`, `{ "`, 1)
		jwk = strings.Replace(jwk, `",`, `", `, -1)
		jwk = jwk[0 : len(jwk)-1]
		jwk = jwk + `, "ext": true , "key_ops": ["sign"] }`
		// `{ "kty": "EC" , "crv": %q , "d": %q , "x": %q , "y": %q }`, jwk.Crv, jwk.D, jwk.X, jwk.Y
		fmt.Fprintf(w, jwk)
	})

	http.HandleFunc("/.well-known/openid-configuration", func(w http.ResponseWriter, r *http.Request) {
		baseURL := getBaseURL(r)
		log.Printf("%s %s\n", r.Method, r.URL.Path)
		fmt.Fprintf(w, `{ "issuer": "%s", "jwks_uri": "%s/.well-known/jwks.json" }`, baseURL, baseURL)
	})

	http.HandleFunc("/.well-known/jwks.json", func(w http.ResponseWriter, r *http.Request) {
		log.Printf("%s %s %s", r.Method, r.Host, r.URL.Path)
		parts := strings.Split(r.Host, ".")
		kid := parts[0]

		b, err := ioutil.ReadFile(filepath.Join(jwksPrefix, strings.ToLower(kid)+".jwk.json"))
		if nil != err {
			//http.Error(w, "Not Found", http.StatusNotFound)
			exp := strconv.FormatInt(time.Now().Add(15*time.Minute).Unix(), 10)
			jwkReal := string(keypairs.MarshalJWKPublicKey(signingPub))
			jwkReal = strings.Replace(jwkReal, `{"`, `{ "`, 1)
			jwkReal = strings.Replace(jwkReal, `",`, `" ,`, -1)
			jwkReal = jwkReal[0 : len(jwkReal)-1]
			jwkReal = jwkReal + fmt.Sprintf(`, "ext": true , "key_ops": ["verify"], "exp": %s, "REAL": true }`, exp)

			jwkFake := string(keypairs.MarshalJWKPublicKey(pubkey))
			jwkFake = strings.Replace(jwkFake, `{"`, `{ "`, 1)
			jwkFake = strings.Replace(jwkFake, `",`, `" ,`, -1)
			jwkFake = jwkFake[0 : len(jwkFake)-1]
			jwkFake = jwkFake + fmt.Sprintf(`, "ext": true , "key_ops": ["verify"], "exp": %s, "FAKE": true }`, exp)
			// { "kty": "EC" , "crv": %q , "x": %q , "y": %q , "kid": %q , "ext": true , "key_ops": ["verify"] , "exp": %s }
			jwkstr := fmt.Sprintf(`{ "keys": [ %s, %s ] }`, jwkFake, jwkReal)
			fmt.Println("jwkstr:", jwkstr)
			fmt.Fprintf(w, jwkstr)
			return
		}

		tok := &PublicJWK{}
		err = json.Unmarshal(b, tok)
		if nil != err {
			// TODO delete the bad file?
			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
			return
		}

		jwkstr := fmt.Sprintf(
			`{ "keys": [ { "kty": "EC", "crv": %q, "x": %q, "y": %q, "kid": %q,`+
				` "ext": true, "key_ops": ["verify"], "exp": %s } ] }`,
			tok.Crv, tok.X, tok.Y, tok.KeyID, strconv.FormatInt(time.Now().Add(15*time.Minute).Unix(), 10),
		)
		fmt.Println("jwkstr:", jwkstr)
		fmt.Fprintf(w, jwkstr)
	})

	return http.DefaultServeMux
}

func verifyToken(token string) (*InspectableToken, error) {
	parts := strings.Split(token, ".")
	if 3 != len(parts) {
		return nil, errors.New("Bad Format: token should be in the format of <protected-header>.<payload>.<signature>")
	}
	protected64 := parts[0]
	payload64 := parts[1]
	signature64 := parts[2]

	protectedB, err := base64.RawURLEncoding.DecodeString(protected64)
	if nil != err {
		return nil, errors.New("Bad Format: token's header should be URL-safe base64 encoded")
	}
	payloadB, err := base64.RawURLEncoding.DecodeString(payload64)
	if nil != err {
		return nil, errors.New("Bad Format: token's payload should be URL-safe base64 encoded")
	}
	// TODO verify signature
	sig, err := base64.RawURLEncoding.DecodeString(signature64)
	if nil != err {
		return nil, errors.New("Bad Format: token's signature should be URL-safe base64 encoded")
	}

	errs := []string{}

	protected := map[string]interface{}{}
	err = json.Unmarshal(protectedB, &protected)
	if nil != err {
		return nil, errors.New("Bad Format: token's header should be URL-safe base64-encoded JSON")
	}
	kid, kidOK := protected["kid"].(string)
	// TODO parse jwkM
	_, jwkOK := protected["jwk"]
	if !kidOK && !jwkOK {
		errs = append(errs, "must have either header.kid or header.jwk")
	}

	data := map[string]interface{}{}
	err = json.Unmarshal(payloadB, &data)
	if nil != err {
		return nil, errors.New("Bad Format: token's payload should be URL-safe base64-encoded JSON")
	}
	iss, issOK := data["iss"].(string)
	if !jwkOK && !issOK {
		errs = append(errs, "payload.iss must exist to complement header.kid")
	}

	pub, err := keyfetch.OIDCJWK(kid, iss)
	if nil != err {
		fmt.Println("couldn't fetch pub key:")
		fmt.Println(err)
	}
	fmt.Println("fetched pub key:")
	fmt.Println(pub)

	hash := sha256.Sum256([]byte(fmt.Sprintf("%s.%s", protected64, payload64)))
	verified := JOSEVerify(pub, hash[:], sig)

	inspected := &InspectableToken{
		Public:    pub,
		Protected: protected,
		Payload:   data,
		Signature: signature64,
		Verified:  verified,
		Errors:    errs,
	}

	return inspected, nil
}

type OTP struct {
	//Attempts    int       `json:"attempts"`
	CreatedAt   time.Time `json:"created_at"`
	Email       string    `json:"email"`
	ReceiptUA   string    `json:"receipt_agent"`
	ReceiptIP   string    `json:"receipt_addr"`
	ReceiptUsed time.Time `json:"receipt_used"`
	SecretUA    string    `json:"secret_agent"`
	SecretIP    string    `json:"secret_addr"`
	SecretUsed  time.Time `json:"secret_used"`
	AccessToken string    `json:"access_token,omitempty"`
}

func hashOTPSecret(secret []byte) (hash string, receipt string) {
	tokenID := sha1.Sum(secret[:])
	receipt = base64.RawURLEncoding.EncodeToString(tokenID[:])
	return hashOTPReceipt(receipt), receipt
}
func hashOTPReceipt(receipt string) (hash string) {
	return base64.RawURLEncoding.EncodeToString([]byte(receipt))
}

func newOTP(email string, agent string, addr string) (id string, secret []byte, err error) {
	uuid, err := uuid.NewRandom()
	secret, _ = uuid.MarshalBinary()
	if nil != err {
		// nothing else to do if we run out of random
		// or are on a platform that doesn't support random
		panic(fmt.Errorf("random bytes read failure: %w", err))
	}
	// The (double) hash becomes the file or DB id.
	// Using this rather than the secret itself prevents DB / FS / compare timing attacks
	hash, receipt := hashOTPSecret(secret)
	otp := OTP{
		CreatedAt: time.Now(),
		Email:     strings.ToLower(email),
		ReceiptUA: agent,
		ReceiptIP: addr,
		//Attempts:  0,
	}
	otpJSON, _ := json.Marshal(otp)
	if err := ioutil.WriteFile(
		filepath.Join(tokenPrefix, hash+".tok.txt"),
		otpJSON,
		// keep it secret, keep it safe
		os.FileMode(0600),
	); nil != err {
		return "", nil, serverError{"database connection failed when writing verification token"}
	}
	return receipt, secret, nil
}

type otpConsumer struct {
	secret  bool
	receipt bool
}

func consumeOTPSecret(email string, secret []byte, agent string, addr string) (*OTP, error) {
	hash, _ := hashOTPSecret(secret)
	return checkOTP(hash, email, agent, addr, otpConsumer{secret: true})
}

func consumeOTPReceipt(email string, receipt string, agent string, addr string) (*OTP, error) {
	hash := hashOTPReceipt(receipt)
	return checkOTP(hash, email, agent, addr, otpConsumer{receipt: true})
}

func checkOTP(hash, email, agent, addr string, consume otpConsumer) (*OTP, error) {
	email = strings.ToLower(email)
	// the double hash will not leak timing info on lookup
	tokfile := filepath.Join(tokenPrefix, hash+".tok.txt")
	b, err := ioutil.ReadFile(tokfile)
	if nil != err {
		return nil, serverError{"database connection failed when reading verification token"}
	}

	otp := OTP{}
	if err := json.Unmarshal(b, &otp); nil != err {
		return nil, serverError{"database verification token parse failed"}
	}

	if 0 == subtle.ConstantTimeCompare([]byte(otp.Email), []byte(email)) {
		// TODO error
		// TODO increment attempts?
	}

	if consume.secret {
		if !otp.SecretUsed.IsZero() {
			return nil, errUsedToken
		}
		otp.SecretUsed = time.Now()
		if addr != otp.ReceiptIP {
			otp.SecretUA = agent
			otp.SecretIP = addr
		}
		if consume.receipt && otp.ReceiptUsed.IsZero() {
			otp.ReceiptUsed = otp.SecretUsed
		}
	} else if consume.receipt {
		if otp.SecretUsed.IsZero() {
			return nil, errTokenNotVerified
		}
		if !otp.ReceiptUsed.IsZero() {
			return nil, errUsedToken
		}
		otp.ReceiptUsed = time.Now()
	}

	if consume.secret || consume.receipt {
		otpJSON, _ := json.Marshal(otp)
		if err := ioutil.WriteFile(
			filepath.Join(tokenPrefix, hash+".tok.txt"),
			otpJSON,
			// keep it secret, keep it safe
			os.FileMode(0600),
		); nil != err {
			return nil, serverError{"database connection failed when consuming token"}
		}
	}

	return &otp, nil
}

func lintEmail(email string) (string, error) {
	// TODO check DNS for MX records
	parts := strings.Split(email, "@")
	domain := parts[1]
	if 2 != len(parts) || strings.Contains(email, " \t\n") {
		return "", errInvalidEmail
	}
	mxs, err := net.LookupMX(domain)
	if len(mxs) < 1 || nil != err {
		// TODO it possible in some cases that this
		// could be a network error
		return "", errInvalidEmail
	}
	return strings.ToLower(email), nil
}

func startVerification(baseURL, contact, agent, addr string) (receipt string, err error) {
	email := strings.Replace(strings.TrimPrefix(contact, "mailto:"), " ", "+", -1)
	if "" == email {
		return "", errors.New("missing contact:[\"mailto:me@example.com\"]")
	}

	email, err = lintEmail(email)
	if nil != err {
		return "", err
	}

	// TODO expect JWK in JWS/JWT
	// TODO place validated JWK into file with token

	ua := ua.Parse(agent)

	receipt, secret, err := newOTP(email, agent, addr)
	if nil != err {
		return "", err
	}
	subject := "Verify New Account"
	// TODO go tpl
	// TODO determine OS and Browser from user agent
	page := "pocket/iframe.html"
	text := fmt.Sprintf(
		"It looks like you just tried to register a new Pocket ID account.\n\n    Verify account: %s/%s#/verify/%s\n\n%s on %s %s from %s\n\nNot you? Just ignore this message.",
		baseURL, page, base64.RawURLEncoding.EncodeToString(secret), ua.Name, ua.OS, ua.Device, addr,
	)
	fmt.Println("email:", text)
	if !strings.Contains(contact, "+noreply") {
		if _, err = SendSimpleMessage(email, defaultFrom, subject, text, defaultReplyTo); nil != err {
			return "", err
		}
	}

	return receipt, nil
}

func getBaseURL(r *http.Request) string {
	var scheme string
	if nil != r.TLS || "https" == r.Header.Get("X-Forwarded-Proto") {
		scheme = "https:"
	} else {
		scheme = "http:"
	}
	return fmt.Sprintf(
		"%s//%s",
		scheme,
		r.Host,
	)
}

// HTTPError describes an error that should be propagated to the HTTP client
type HTTPError struct {
	message string
	code    int
}

func postEC(jwksPrefix string, tok map[string]interface{}, w http.ResponseWriter, r *http.Request) {
	data, err := postECHelper(r.Host, jwksPrefix, tok, r)
	if nil != err {
		http.Error(w, err.message, err.code)
		return
	}
	w.Write(data)
}

func postECHelper(hostname, jwksPrefix string, tok map[string]interface{}, r *http.Request) ([]byte, *HTTPError) {
	crv, ok := tok["crv"].(string)
	if 5 != len(crv) || "P-" != crv[:2] {
		return nil, &HTTPError{"Bad Request: bad curve", http.StatusBadRequest}
	}
	x, ok := tok["x"].(string)
	if !ok {
		return nil, &HTTPError{"Bad Request: missing 'x'", http.StatusBadRequest}
	}
	y, ok := tok["y"].(string)
	if !ok {
		return nil, &HTTPError{"Bad Request: missing 'y'", http.StatusBadRequest}
	}

	thumbprintable := []byte(
		fmt.Sprintf(`{"crv":%q,"kty":"EC","x":%q,"y":%q}`, crv, x, y),
	)
	alg := crv[2:]

	var thumb []byte
	switch alg {
	case "256":
		hash := sha256.Sum256(thumbprintable)
		thumb = hash[:]
	case "384":
		hash := sha512.Sum384(thumbprintable)
		thumb = hash[:]
	case "521":
		fallthrough
	case "512":
		hash := sha512.Sum512(thumbprintable)
		thumb = hash[:]
	default:
		return nil, &HTTPError{"Bad Request: bad key length or curve", http.StatusBadRequest}
	}

	kid := base64.RawURLEncoding.EncodeToString(thumb)
	if kid2, _ := tok["kid"].(string); "" != kid2 && kid != kid2 {
		return nil, &HTTPError{"Bad Request: kid should be " + kid, http.StatusBadRequest}
	}

	pub := []byte(fmt.Sprintf(
		`{"crv":%q,"kid":%q,"kty":"EC","x":%q,"y":%q}`, crv, kid, x, y,
	))

	// TODO allow posting at the top-level?
	// TODO support a group of keys by PPID
	// (right now it's only by KID)
	if !strings.HasPrefix(hostname, strings.ToLower(kid)+".") {
		return nil, &HTTPError{"Bad Request: prefix should be " + kid, http.StatusBadRequest}
	}

	if err := ioutil.WriteFile(
		filepath.Join(jwksPrefix, strings.ToLower(kid)+".jwk.json"),
		pub,
		0644,
	); nil != err {
		fmt.Println("can't write file")
		return nil, &HTTPError{"Internal Server Error", http.StatusInternalServerError}
	}

	baseURL := getBaseURL(r)
	return []byte(fmt.Sprintf(
		`{ "iss":%q, "jwks_url":%q }`, baseURL+"/", baseURL+"/.well-known/jwks.json",
	)), nil
}

func postRSA(jwksPrefix string, tok map[string]interface{}, w http.ResponseWriter, r *http.Request) {
	data, err := postRSAHelper(r.Host, jwksPrefix, tok, r)
	if nil != err {
		http.Error(w, err.message, err.code)
		return
	}
	w.Write(data)
}

func postRSAHelper(hostname, jwksPrefix string, tok map[string]interface{}, r *http.Request) ([]byte, *HTTPError) {
	e, ok := tok["e"].(string)
	if !ok {
		return nil, &HTTPError{"Bad Request: missing 'e'", http.StatusBadRequest}
	}
	n, ok := tok["n"].(string)
	if !ok {
		return nil, &HTTPError{"Bad Request: missing 'n'", http.StatusBadRequest}
	}

	thumbprintable := []byte(
		fmt.Sprintf(`{"e":%q,"kty":"RSA","n":%q}`, e, n),
	)

	var thumb []byte
	// TODO handle bit lengths well
	switch 3 * (len(n) / 4.0) {
	case 256:
		hash := sha256.Sum256(thumbprintable)
		thumb = hash[:]
	case 384:
		hash := sha512.Sum384(thumbprintable)
		thumb = hash[:]
	case 512:
		hash := sha512.Sum512(thumbprintable)
		thumb = hash[:]
	default:
		return nil, &HTTPError{"Bad Request: only standard RSA key lengths (2048, 3072, 4096) are supported", http.StatusBadRequest}
	}

	kid := base64.RawURLEncoding.EncodeToString(thumb)
	if kid2, _ := tok["kid"].(string); "" != kid2 && kid != kid2 {
		return nil, &HTTPError{"Bad Request: kid should be " + kid, http.StatusBadRequest}
	}

	pub := []byte(fmt.Sprintf(
		`{"e":%q,"kid":%q,"kty":"EC","n":%q}`, e, kid, n,
	))

	// TODO allow posting at the top-level?
	// TODO support a group of keys by PPID
	// (right now it's only by KID)
	if !strings.HasPrefix(hostname, strings.ToLower(kid)+".") {
		return nil, &HTTPError{"Bad Request: prefix should be " + kid, http.StatusBadRequest}
	}

	if err := ioutil.WriteFile(
		filepath.Join(jwksPrefix, strings.ToLower(kid)+".jwk.json"),
		pub,
		0644,
	); nil != err {
		fmt.Println("can't write file")
		return nil, &HTTPError{"Internal Server Error", http.StatusInternalServerError}
	}

	baseURL := getBaseURL(r)
	return []byte(fmt.Sprintf(
		`{ "iss":%q, "jwks_url":%q }`, baseURL+"/", baseURL+"/.well-known/jwks.json",
	)), nil
}