http: authentication module; hash-password cmd; http_basic provider

This implements HTTP basicauth into Caddy 2. The basic auth module will
not work with passwords that are not securely hashed, so a subcommand
hash-password was added to make it convenient to produce those hashes.

Also included is Caddyfile support.

Closes #2747.

5 files changed, 561 insertions, 0 deletions

diff --git a/modules/caddyhttp/caddyauth/basicauth.go b/modules/caddyhttp/caddyauth/basicauth.go
new file mode 100644
index 0000000..b7c002b
--- /dev/null
+++ b/modules/caddyhttp/caddyauth/basicauth.go
@@ -0,0 +1,164 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyauth
+
+import (
+	"crypto/sha256"
+	"crypto/subtle"
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"github.com/caddyserver/caddy/v2"
+)
+
+func init() {
+	caddy.RegisterModule(HTTPBasicAuth{})
+}
+
+// HTTPBasicAuth facilitates HTTP basic authentication.
+type HTTPBasicAuth struct {
+	HashRaw     json.RawMessage `json:"hash,omitempty"`
+	AccountList []Account       `json:"accounts,omitempty"`
+	Realm       string          `json:"realm,omitempty"`
+
+	Accounts map[string]Account `json:"-"`
+	Hash     Comparer           `json:"-"`
+}
+
+// CaddyModule returns the Caddy module information.
+func (HTTPBasicAuth) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		Name: "http.handlers.authentication.providers.http_basic",
+		New:  func() caddy.Module { return new(HTTPBasicAuth) },
+	}
+}
+
+// Provision provisions the HTTP basic auth provider.
+func (hba *HTTPBasicAuth) Provision(ctx caddy.Context) error {
+	if hba.HashRaw == nil {
+		return fmt.Errorf("passwords must be hashed, so a hash must be defined")
+	}
+
+	// load password hasher
+	hashIface, err := ctx.LoadModuleInline("algorithm", "http.handlers.authentication.hashes", hba.HashRaw)
+	if err != nil {
+		return fmt.Errorf("loading password hasher module: %v", err)
+	}
+	hba.Hash = hashIface.(Comparer)
+	hba.HashRaw = nil // allow GC to deallocate
+
+	if hba.Hash == nil {
+		return fmt.Errorf("hash is required")
+	}
+
+	// load account list
+	hba.Accounts = make(map[string]Account)
+	for _, acct := range hba.AccountList {
+		if _, ok := hba.Accounts[acct.Username]; ok {
+			return fmt.Errorf("username is not unique: %s", acct.Username)
+		}
+		hba.Accounts[acct.Username] = acct
+	}
+	hba.AccountList = nil // allow GC to deallocate
+
+	return nil
+}
+
+// Authenticate validates the user credentials in req and returns the user, if valid.
+func (hba HTTPBasicAuth) Authenticate(w http.ResponseWriter, req *http.Request) (User, bool, error) {
+	username, plaintextPasswordStr, ok := req.BasicAuth()
+
+	// if basic auth is missing or invalid, prompt for credentials
+	if !ok {
+		// browsers show a message that says something like:
+		// "The website says: <realm>"
+		// which is kinda dumb, but whatever.
+		realm := hba.Realm
+		if realm == "" {
+			realm = "restricted"
+		}
+
+		w.Header().Set("WWW-Authenticate", fmt.Sprintf(`Basic realm="%s"`, realm))
+
+		return User{}, false, nil
+	}
+
+	plaintextPassword := []byte(plaintextPasswordStr)
+
+	account, accountExists := hba.Accounts[username]
+	// don't return early if account does not exist; we want
+	// to try to avoid side-channels that leak existence
+
+	same, err := hba.Hash.Compare(account.Password, plaintextPassword, account.Salt)
+	if err != nil {
+		return User{}, false, err
+	}
+	if !same || !accountExists {
+		return User{}, false, nil
+	}
+
+	return User{ID: username}, true, nil
+}
+
+// Comparer is a type that can securely compare
+// a plaintext password with a hashed password
+// in constant-time. Comparers should hash the
+// plaintext password and then use constant-time
+// comparison.
+type Comparer interface {
+	// Compare returns true if the result of hashing
+	// plaintextPassword with salt is hashedPassword,
+	// false otherwise. An error is returned only if
+	// there is a technical/configuration error.
+	Compare(hashedPassword, plaintextPassword, salt []byte) (bool, error)
+}
+
+type quickComparer struct{}
+
+func (quickComparer) Compare(theirHash, plaintext, _ []byte) (bool, error) {
+	ourHash := quickHash(plaintext)
+	return hashesMatch(ourHash, theirHash), nil
+}
+
+func hashesMatch(pwdHash1, pwdHash2 []byte) bool {
+	return subtle.ConstantTimeCompare(pwdHash1, pwdHash2) == 1
+}
+
+// quickHash returns the SHA-256 of v. It
+// is not secure for password storage, but
+// it is useful for efficiently normalizing
+// the length of plaintext passwords for
+// constant-time comparisons.
+//
+// Errors are discarded.
+func quickHash(v []byte) []byte {
+	h := sha256.New()
+	h.Write([]byte(v))
+	return h.Sum(nil)
+}
+
+// Account contains a username, password, and salt (if applicable).
+type Account struct {
+	Username string `json:"username"`
+	Password []byte `json:"password"`
+	Salt     []byte `json:"salt,omitempty"` // for algorithms where external salt is needed
+}
+
+// Interface guards
+var (
+	_ caddy.Provisioner = (*HTTPBasicAuth)(nil)
+	_ Authenticator     = (*HTTPBasicAuth)(nil)
+)
diff --git a/modules/caddyhttp/caddyauth/caddyauth.go b/modules/caddyhttp/caddyauth/caddyauth.go
new file mode 100644
index 0000000..48d4fba
--- /dev/null
+++ b/modules/caddyhttp/caddyauth/caddyauth.go
@@ -0,0 +1,102 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyauth
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/caddyserver/caddy/v2"
+	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
+)
+
+func init() {
+	caddy.RegisterModule(Authentication{})
+}
+
+// Authentication is a middleware which provides user authentication.
+type Authentication struct {
+	ProvidersRaw map[string]json.RawMessage `json:"providers,omitempty"`
+
+	Providers map[string]Authenticator `json:"-"`
+}
+
+// CaddyModule returns the Caddy module information.
+func (Authentication) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		Name: "http.handlers.authentication",
+		New:  func() caddy.Module { return new(Authentication) },
+	}
+}
+
+// Provision sets up a.
+func (a *Authentication) Provision(ctx caddy.Context) error {
+	a.Providers = make(map[string]Authenticator)
+	for modName, rawMsg := range a.ProvidersRaw {
+		val, err := ctx.LoadModule("http.handlers.authentication.providers."+modName, rawMsg)
+		if err != nil {
+			return fmt.Errorf("loading authentication provider module '%s': %v", modName, err)
+		}
+		a.Providers[modName] = val.(Authenticator)
+	}
+	a.ProvidersRaw = nil // allow GC to deallocate
+
+	return nil
+}
+
+func (a Authentication) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
+	var user User
+	var authed bool
+	var err error
+	for provName, prov := range a.Providers {
+		user, authed, err = prov.Authenticate(w, r)
+		if err != nil {
+			log.Printf("[ERROR] Authenticating with %s: %v", provName, err)
+			continue
+		}
+		if authed {
+			break
+		}
+	}
+	if !authed {
+		return caddyhttp.Error(http.StatusUnauthorized, fmt.Errorf("not authenticated"))
+	}
+
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(caddy.Replacer)
+	repl.Set("http.handlers.authentication.user.id", user.ID)
+
+	return next.ServeHTTP(w, r)
+}
+
+// Authenticator is a type which can authenticate a request.
+// If a request was not authenticated, it returns false. An
+// error is only returned if authenticating the request fails
+// for a technical reason (not for bad/missing credentials).
+type Authenticator interface {
+	Authenticate(http.ResponseWriter, *http.Request) (User, bool, error)
+}
+
+// User represents an authenticated user.
+type User struct {
+	ID string
+}
+
+// Interface guards
+var (
+	_ caddy.Provisioner           = (*Authentication)(nil)
+	_ caddyhttp.MiddlewareHandler = (*Authentication)(nil)
+)
diff --git a/modules/caddyhttp/caddyauth/caddyfile.go b/modules/caddyhttp/caddyauth/caddyfile.go
new file mode 100644
index 0000000..3600324
--- /dev/null
+++ b/modules/caddyhttp/caddyauth/caddyfile.go
@@ -0,0 +1,104 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyauth
+
+import (
+	"encoding/base64"
+	"encoding/json"
+
+	"github.com/caddyserver/caddy/v2/caddyconfig"
+	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
+	"github.com/caddyserver/caddy/v2/modules/caddyhttp"
+)
+
+func init() {
+	httpcaddyfile.RegisterHandlerDirective("basicauth", parseCaddyfile)
+}
+
+// parseCaddyfile sets up the handler from Caddyfile tokens. Syntax:
+//
+//     basicauth [<matcher>] [<hash_algorithm>] {
+//         <username> <hashed_password_base64> [<salt_base64>]
+//         ...
+//     }
+//
+// If no hash algorithm is supplied, bcrypt will be assumed.
+func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error) {
+	var ba HTTPBasicAuth
+
+	for h.Next() {
+		var cmp Comparer
+		args := h.RemainingArgs()
+
+		var hashName string
+		switch len(args) {
+		case 0:
+			hashName = "bcrypt"
+		case 1:
+			hashName = args[0]
+		default:
+			return nil, h.ArgErr()
+		}
+
+		switch hashName {
+		case "bcrypt":
+			cmp = BcryptHash{}
+		case "scrypt":
+			cmp = ScryptHash{}
+		default:
+			return nil, h.Errf("unrecognized hash algorithm: %s", hashName)
+		}
+
+		ba.HashRaw = caddyconfig.JSONModuleObject(cmp, "algorithm", hashName, nil)
+
+		for h.NextBlock(0) {
+			username := h.Val()
+
+			var b64Pwd, b64Salt string
+			h.Args(&b64Pwd, &b64Salt)
+			if h.NextArg() {
+				return nil, h.ArgErr()
+			}
+
+			if username == "" || b64Pwd == "" {
+				return nil, h.Err("username and password cannot be empty or missing")
+			}
+
+			pwd, err := base64.StdEncoding.DecodeString(b64Pwd)
+			if err != nil {
+				return nil, h.Errf("decoding password: %v", err)
+			}
+			var salt []byte
+			if b64Salt != "" {
+				salt, err = base64.StdEncoding.DecodeString(b64Salt)
+				if err != nil {
+					return nil, h.Errf("decoding salt: %v", err)
+				}
+			}
+
+			ba.AccountList = append(ba.AccountList, Account{
+				Username: username,
+				Password: pwd,
+				Salt:     salt,
+			})
+		}
+	}
+
+	return Authentication{
+		ProvidersRaw: map[string]json.RawMessage{
+			"http_basic": caddyconfig.JSON(ba, nil),
+		},
+	}, nil
+}
diff --git a/modules/caddyhttp/caddyauth/command.go b/modules/caddyhttp/caddyauth/command.go
new file mode 100644
index 0000000..c110001
--- /dev/null
+++ b/modules/caddyhttp/caddyauth/command.go
@@ -0,0 +1,80 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyauth
+
+import (
+	"encoding/base64"
+	"flag"
+	"fmt"
+
+	"github.com/caddyserver/caddy/v2"
+	caddycmd "github.com/caddyserver/caddy/v2/cmd"
+	"golang.org/x/crypto/bcrypt"
+	"golang.org/x/crypto/scrypt"
+)
+
+func init() {
+	caddycmd.RegisterCommand(caddycmd.Command{
+		Name:  "hash-password",
+		Func:  cmdHashPassword,
+		Usage: "--plaintext <password> [--salt <string>] [--algorithm <name>]",
+		Short: "Hashes a password and writes base64",
+		Long: `
+Convenient way to hash a plaintext password. The resulting
+hash is written to stdout as a base64 string.
+
+--algorithm may be bcrypt or scrypt. If script, the default
+parameters are used.
+
+Use the --salt flag for algorithms which require a salt to
+be provided (scrypt).
+`,
+		Flags: func() *flag.FlagSet {
+			fs := flag.NewFlagSet("hash-password", flag.ExitOnError)
+			fs.String("algorithm", "bcrypt", "Name of the hash algorithm")
+			fs.String("plaintext", "", "The plaintext password")
+			fs.String("salt", "", "The password salt")
+			return fs
+		}(),
+	})
+}
+
+func cmdHashPassword(fs caddycmd.Flags) (int, error) {
+	algorithm := fs.String("algorithm")
+	plaintext := []byte(fs.String("plaintext"))
+	salt := []byte(fs.String("salt"))
+
+	var hash []byte
+	var err error
+	switch algorithm {
+	case "bcrypt":
+		hash, err = bcrypt.GenerateFromPassword(plaintext, bcrypt.DefaultCost)
+	case "scrypt":
+		def := ScryptHash{}
+		def.SetDefaults()
+		hash, err = scrypt.Key(plaintext, salt, def.N, def.R, def.P, def.KeyLength)
+	default:
+		return caddy.ExitCodeFailedStartup, fmt.Errorf("unrecognized hash algorithm: %s", algorithm)
+	}
+	if err != nil {
+		return caddy.ExitCodeFailedStartup, err
+	}
+
+	hashBase64 := base64.StdEncoding.EncodeToString([]byte(hash))
+
+	fmt.Println(hashBase64)
+
+	return 0, nil
+}
diff --git a/modules/caddyhttp/caddyauth/hashes.go b/modules/caddyhttp/caddyauth/hashes.go
new file mode 100644
index 0000000..a515c09
--- /dev/null
+++ b/modules/caddyhttp/caddyauth/hashes.go
@@ -0,0 +1,111 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package caddyauth
+
+import (
+	"github.com/caddyserver/caddy/v2"
+	"golang.org/x/crypto/bcrypt"
+	"golang.org/x/crypto/scrypt"
+)
+
+func init() {
+	caddy.RegisterModule(BcryptHash{})
+	caddy.RegisterModule(ScryptHash{})
+}
+
+// BcryptHash implements the bcrypt hash.
+type BcryptHash struct{}
+
+// CaddyModule returns the Caddy module information.
+func (BcryptHash) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		Name: "http.handlers.authentication.hashes.bcrypt",
+		New:  func() caddy.Module { return new(BcryptHash) },
+	}
+}
+
+// Compare compares passwords.
+func (BcryptHash) Compare(hashed, plaintext, _ []byte) (bool, error) {
+	err := bcrypt.CompareHashAndPassword(hashed, plaintext)
+	if err == bcrypt.ErrMismatchedHashAndPassword {
+		return false, nil
+	}
+	if err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+// ScryptHash implements the scrypt KDF as a hash.
+type ScryptHash struct {
+	N         int `json:"N,omitempty"`
+	R         int `json:"r,omitempty"`
+	P         int `json:"p,omitempty"`
+	KeyLength int `json:"key_length,omitempty"`
+}
+
+// CaddyModule returns the Caddy module information.
+func (ScryptHash) CaddyModule() caddy.ModuleInfo {
+	return caddy.ModuleInfo{
+		Name: "http.handlers.authentication.hashes.scrypt",
+		New:  func() caddy.Module { return new(ScryptHash) },
+	}
+}
+
+// Provision sets up s.
+func (s *ScryptHash) Provision(_ caddy.Context) error {
+	s.SetDefaults()
+	return nil
+}
+
+// SetDefaults sets safe default parameters, but does
+// not overwrite existing values. Each default parameter
+// is set independently; it does not check to ensure
+// that r*p < 2^30. The defaults chosen are those as
+// recommended in 2019 by
+// https://godoc.org/golang.org/x/crypto/scrypt.
+func (s *ScryptHash) SetDefaults() {
+	if s.N == 0 {
+		s.N = 32768
+	}
+	if s.R == 0 {
+		s.R = 8
+	}
+	if s.P == 0 {
+		s.P = 1
+	}
+	if s.KeyLength == 0 {
+		s.KeyLength = 32
+	}
+}
+
+// Compare compares passwords.
+func (s ScryptHash) Compare(hashed, plaintext, salt []byte) (bool, error) {
+	ourHash, err := scrypt.Key(plaintext, salt, s.N, s.R, s.P, s.KeyLength)
+	if err != nil {
+		return false, err
+	}
+	if hashesMatch(hashed, ourHash) {
+		return true, nil
+	}
+	return false, nil
+}
+
+// Interface guards
+var (
+	_ Comparer          = (*BcryptHash)(nil)
+	_ Comparer          = (*ScryptHash)(nil)
+	_ caddy.Provisioner = (*ScryptHash)(nil)
+)