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// 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"
"fmt"
"net/http"
"github.com/caddyserver/caddy/v2"
)
func init() {
caddy.RegisterModule(HTTPBasicAuth{})
}
// HTTPBasicAuth facilitates HTTP basic authentication.
type HTTPBasicAuth struct {
// The algorithm with which the passwords are hashed. Default: bcrypt
HashRaw json.RawMessage `json:"hash,omitempty" caddy:"namespace=http.authentication.hashes inline_key=algorithm"`
// The list of accounts to authenticate.
AccountList []Account `json:"accounts,omitempty"`
// The name of the realm. Default: restricted
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{
ID: "http.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 {
hba.HashRaw = json.RawMessage(`{"algorithm": "bcrypt"}`)
}
// load password hasher
hasherIface, err := ctx.LoadModule(hba, "HashRaw")
if err != nil {
return fmt.Errorf("loading password hasher module: %v", err)
}
hba.Hash = hasherIface.(Comparer)
if hba.Hash == nil {
return fmt.Errorf("hash is required")
}
repl := caddy.NewReplacer()
// load account list
hba.Accounts = make(map[string]Account)
for i, acct := range hba.AccountList {
if _, ok := hba.Accounts[acct.Username]; ok {
return fmt.Errorf("account %d: username is not unique: %s", i, acct.Username)
}
acct.Username = repl.ReplaceAll(acct.Username, "")
acct.Password = repl.ReplaceAll(string(acct.Password), "")
acct.Salt = repl.ReplaceAll(string(acct.Salt), "")
if acct.Username == "" || acct.Password == "" {
return fmt.Errorf("account %d: username and password are required", i)
}
acct.password, err = base64.StdEncoding.DecodeString(acct.Password)
if err != nil {
return fmt.Errorf("base64-decoding password: %v", err)
}
if acct.Salt != "" {
acct.salt, err = base64.StdEncoding.DecodeString(acct.Salt)
if err != nil {
return fmt.Errorf("base64-decoding salt: %v", err)
}
}
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 !ok {
return hba.promptForCredentials(w, 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 hba.promptForCredentials(w, err)
}
if !same || !accountExists {
return hba.promptForCredentials(w, nil)
}
return User{ID: username}, true, nil
}
func (hba HTTPBasicAuth) promptForCredentials(w http.ResponseWriter, err error) (User, bool, error) {
// 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, err
}
// 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)
}
// Account contains a username, password, and salt (if applicable).
type Account struct {
// A user's username.
Username string `json:"username"`
// The user's hashed password, base64-encoded.
Password string `json:"password"`
// The user's password salt, base64-encoded; for
// algorithms where external salt is needed.
Salt string `json:"salt,omitempty"`
password, salt []byte
}
// Interface guards
var (
_ caddy.Provisioner = (*HTTPBasicAuth)(nil)
_ Authenticator = (*HTTPBasicAuth)(nil)
)
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