Fix http auth header parsing (#34936)

Using `strings.EqualFold` is wrong in many cases.

modules/auth/httpauth/httpauth.go

@@ -0,0 +1,47 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httpauth
+
+import (
+	"encoding/base64"
+	"strings"
+
+	"code.gitea.io/gitea/modules/util"
+)
+
+type BasicAuth struct {
+	Username, Password string
+}
+
+type BearerToken struct {
+	Token string
+}
+
+type ParsedAuthorizationHeader struct {
+	BasicAuth   *BasicAuth
+	BearerToken *BearerToken
+}
+
+func ParseAuthorizationHeader(header string) (ret ParsedAuthorizationHeader, _ bool) {
+	parts := strings.Fields(header)
+	if len(parts) != 2 {
+		return ret, false
+	}
+	if util.AsciiEqualFold(parts[0], "basic") {
+		s, err := base64.StdEncoding.DecodeString(parts[1])
+		if err != nil {
+			return ret, false
+		}
+		u, p, ok := strings.Cut(string(s), ":")
+		if !ok {
+			return ret, false
+		}
+		ret.BasicAuth = &BasicAuth{Username: u, Password: p}
+		return ret, true
+	} else if util.AsciiEqualFold(parts[0], "token") || util.AsciiEqualFold(parts[0], "bearer") {
+		ret.BearerToken = &BearerToken{Token: parts[1]}
+		return ret, true
+	}
+	return ret, false
+}

modules/auth/httpauth/httpauth_test.go

@@ -0,0 +1,43 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httpauth
+
+import (
+	"encoding/base64"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseAuthorizationHeader(t *testing.T) {
+	type parsed = ParsedAuthorizationHeader
+	type basic = BasicAuth
+	type bearer = BearerToken
+	cases := []struct {
+		headerValue string
+		expected    parsed
+		ok          bool
+	}{
+		{"", parsed{}, false},
+		{"?", parsed{}, false},
+		{"foo", parsed{}, false},
+		{"any value", parsed{}, false},
+
+		{"Basic ?", parsed{}, false},
+		{"Basic " + base64.StdEncoding.EncodeToString([]byte("foo")), parsed{}, false},
+		{"Basic " + base64.StdEncoding.EncodeToString([]byte("foo:bar")), parsed{BasicAuth: &basic{"foo", "bar"}}, true},
+		{"basic " + base64.StdEncoding.EncodeToString([]byte("foo:bar")), parsed{BasicAuth: &basic{"foo", "bar"}}, true},
+
+		{"token value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"Token value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"bearer value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"Bearer value", parsed{BearerToken: &bearer{"value"}}, true},
+		{"Bearer wrong value", parsed{}, false},
+	}
+	for _, c := range cases {
+		ret, ok := ParseAuthorizationHeader(c.headerValue)
+		assert.Equal(t, c.ok, ok, "header %q", c.headerValue)
+		assert.Equal(t, c.expected, ret, "header %q", c.headerValue)
+	}
+}

modules/base/tool.go

@@ -8,13 +8,10 @@ import (
 	"crypto/sha1"
 	"crypto/sha256"
 	"crypto/subtle"
-	"encoding/base64"
 	"encoding/hex"
-	"errors"
 	"fmt"
 	"hash"
 	"strconv"
-	"strings"
 	"time"
 
 	"code.gitea.io/gitea/modules/setting"
@@ -36,19 +33,6 @@ func ShortSha(sha1 string) string {
 	return util.TruncateRunes(sha1, 10)
 }
 
-// BasicAuthDecode decode basic auth string
-func BasicAuthDecode(encoded string) (string, string, error) {
-	s, err := base64.StdEncoding.DecodeString(encoded)
-	if err != nil {
-		return "", "", err
-	}
-
-	if username, password, ok := strings.Cut(string(s), ":"); ok {
-		return username, password, nil
-	}
-	return "", "", errors.New("invalid basic authentication")
-}
-
 // VerifyTimeLimitCode verify time limit code
 func VerifyTimeLimitCode(now time.Time, data string, minutes int, code string) bool {
 	if len(code) <= 18 {

modules/base/tool_test.go

@@ -26,25 +26,6 @@ func TestShortSha(t *testing.T) {
 	assert.Equal(t, "veryverylo", ShortSha("veryverylong"))
 }
 
-func TestBasicAuthDecode(t *testing.T) {
-	_, _, err := BasicAuthDecode("?")
-	assert.Equal(t, "illegal base64 data at input byte 0", err.Error())
-
-	user, pass, err := BasicAuthDecode("Zm9vOmJhcg==")
-	assert.NoError(t, err)
-	assert.Equal(t, "foo", user)
-	assert.Equal(t, "bar", pass)
-
-	_, _, err = BasicAuthDecode("aW52YWxpZA==")
-	assert.Error(t, err)
-
-	_, _, err = BasicAuthDecode("invalid")
-	assert.Error(t, err)
-
-	_, _, err = BasicAuthDecode("YWxpY2U=") // "alice", no colon
-	assert.Error(t, err)
-}
-
 func TestVerifyTimeLimitCode(t *testing.T) {
 	defer test.MockVariableValue(&setting.InstallLock, true)()
 	initGeneralSecret := func(secret string) {

modules/util/string.go

@@ -110,3 +110,24 @@ func SplitTrimSpace(input, sep string) []string {
 	}
 	return stringList
 }
+
+func asciiLower(b byte) byte {
+	if 'A' <= b && b <= 'Z' {
+		return b + ('a' - 'A')
+	}
+	return b
+}
+
+// AsciiEqualFold is from Golang https://cs.opensource.google/go/go/+/refs/tags/go1.24.4:src/net/http/internal/ascii/print.go
+// ASCII only. In most cases for protocols, we should only use this but not [strings.EqualFold]
+func AsciiEqualFold(s, t string) bool { //nolint:revive // PascalCase
+	if len(s) != len(t) {
+		return false
+	}
+	for i := 0; i < len(s); i++ {
+		if asciiLower(s[i]) != asciiLower(t[i]) {
+			return false
+		}
+	}
+	return true
+}