basicauth: Accept placeholders; move base64 decoding to provision

See https://caddy.community/t/v2-basicauth-bug/6738?u=matt

modules/caddyhttp/caddyauth/basicauth.go

@@ -15,6 +15,7 @@
 package caddyauth
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -66,12 +67,34 @@ func (hba *HTTPBasicAuth) Provision(ctx caddy.Context) error {
 		return fmt.Errorf("hash is required")
 	}
 
+	repl := caddy.NewReplacer()
+
 	// load account list
 	hba.Accounts = make(map[string]Account)
-	for _, acct := range hba.AccountList {
+	for i, acct := range hba.AccountList {
 		if _, ok := hba.Accounts[acct.Username]; ok {
-			return fmt.Errorf("username is not unique: %s", acct.Username)
+			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
@@ -104,7 +127,7 @@ func (hba HTTPBasicAuth) Authenticate(w http.ResponseWriter, req *http.Request)
 	// 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)
+	same, err := hba.Hash.Compare(account.password, plaintextPassword, account.salt)
 	if err != nil {
 		return User{}, false, err
 	}
@@ -134,11 +157,13 @@ type Account struct {
 	Username string `json:"username"`
 
 	// The user's hashed password, base64-encoded.
-	Password []byte `json:"password"`
+	Password string `json:"password"`
 
 	// The user's password salt, base64-encoded; for
 	// algorithms where external salt is needed.
-	Salt []byte `json:"salt,omitempty"`
+	Salt string `json:"salt,omitempty"`
+
+	password, salt []byte
 }
 
 // Interface guards

modules/caddyhttp/caddyauth/caddyfile.go

@@ -15,8 +15,6 @@
 package caddyauth
 
 import (
-	"encoding/base64"
-
 	"github.com/caddyserver/caddy/v2"
 	"github.com/caddyserver/caddy/v2/caddyconfig"
 	"github.com/caddyserver/caddy/v2/caddyconfig/httpcaddyfile"
@@ -76,22 +74,10 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
 				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,
+				Password: b64Pwd,
+				Salt:     b64Salt,
 			})
 		}
 	}