first-commit

2025-08-25 15:46:12 +08:00
commit f4d95dfff4
5665 changed files with 705359 additions and 0 deletions
--- a/modules/httplib/request.go
+++ b/modules/httplib/request.go
@@ -0,0 +1,220 @@
+// Copyright 2013 The Beego Authors. All rights reserved.
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httplib
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+var defaultSetting = Settings{"GiteaServer", 60 * time.Second, 60 * time.Second, nil, nil}
+
+// newRequest returns *Request with specific method
+func newRequest(url, method string) *Request {
+	var resp http.Response
+	req := http.Request{
+		Method:     method,
+		Header:     make(http.Header),
+		Proto:      "HTTP/1.1",
+		ProtoMajor: 1,
+		ProtoMinor: 1,
+	}
+	return &Request{url, &req, map[string]string{}, defaultSetting, &resp, nil}
+}
+
+// NewRequest returns *Request with specific method
+func NewRequest(url, method string) *Request {
+	return newRequest(url, method)
+}
+
+// Settings is the default settings for http client
+type Settings struct {
+	UserAgent        string
+	ConnectTimeout   time.Duration
+	ReadWriteTimeout time.Duration
+	TLSClientConfig  *tls.Config
+	Transport        http.RoundTripper
+}
+
+// Request provides more useful methods for requesting one url than http.Request.
+type Request struct {
+	url     string
+	req     *http.Request
+	params  map[string]string
+	setting Settings
+	resp    *http.Response
+	body    []byte
+}
+
+// SetContext sets the request's Context
+func (r *Request) SetContext(ctx context.Context) *Request {
+	r.req = r.req.WithContext(ctx)
+	return r
+}
+
+// SetTimeout sets connect time out and read-write time out for BeegoRequest.
+func (r *Request) SetTimeout(connectTimeout, readWriteTimeout time.Duration) *Request {
+	r.setting.ConnectTimeout = connectTimeout
+	r.setting.ReadWriteTimeout = readWriteTimeout
+	return r
+}
+
+func (r *Request) SetReadWriteTimeout(readWriteTimeout time.Duration) *Request {
+	r.setting.ReadWriteTimeout = readWriteTimeout
+	return r
+}
+
+// SetTLSClientConfig sets tls connection configurations if visiting https url.
+func (r *Request) SetTLSClientConfig(config *tls.Config) *Request {
+	r.setting.TLSClientConfig = config
+	return r
+}
+
+// Header add header item string in request.
+func (r *Request) Header(key, value string) *Request {
+	r.req.Header.Set(key, value)
+	return r
+}
+
+// SetTransport sets transport to
+func (r *Request) SetTransport(transport http.RoundTripper) *Request {
+	r.setting.Transport = transport
+	return r
+}
+
+// Param adds query param in to request.
+// params build query string as ?key1=value1&key2=value2...
+func (r *Request) Param(key, value string) *Request {
+	r.params[key] = value
+	return r
+}
+
+// Body adds request raw body. It supports string, []byte and io.Reader as body.
+func (r *Request) Body(data any) *Request {
+	if r == nil {
+		return nil
+	}
+	switch t := data.(type) {
+	case nil: // do nothing
+	case string:
+		bf := strings.NewReader(t)
+		r.req.Body = io.NopCloser(bf)
+		r.req.ContentLength = int64(len(t))
+	case []byte:
+		bf := bytes.NewBuffer(t)
+		r.req.Body = io.NopCloser(bf)
+		r.req.ContentLength = int64(len(t))
+	case io.ReadCloser:
+		r.req.Body = t
+	case io.Reader:
+		r.req.Body = io.NopCloser(t)
+	default:
+		panic(fmt.Sprintf("unsupported request body type %T", t))
+	}
+	return r
+}
+
+func (r *Request) getResponse() (*http.Response, error) {
+	if r.resp.StatusCode != 0 {
+		return r.resp, nil
+	}
+
+	var paramBody string
+	if len(r.params) > 0 {
+		var buf bytes.Buffer
+		for k, v := range r.params {
+			buf.WriteString(url.QueryEscape(k))
+			buf.WriteByte('=')
+			buf.WriteString(url.QueryEscape(v))
+			buf.WriteByte('&')
+		}
+		paramBody = buf.String()
+		paramBody = paramBody[0 : len(paramBody)-1]
+	}
+
+	if r.req.Method == http.MethodGet && len(paramBody) > 0 {
+		if strings.Contains(r.url, "?") {
+			r.url += "&" + paramBody
+		} else {
+			r.url = r.url + "?" + paramBody
+		}
+	} else if r.req.Method == http.MethodPost && r.req.Body == nil && len(paramBody) > 0 {
+		r.Header("Content-Type", "application/x-www-form-urlencoded")
+		r.Body(paramBody) // string
+	}
+
+	var err error
+	r.req.URL, err = url.Parse(r.url)
+	if err != nil {
+		return nil, err
+	}
+
+	trans := r.setting.Transport
+	if trans == nil {
+		// create default transport
+		trans = &http.Transport{
+			TLSClientConfig: r.setting.TLSClientConfig,
+			Proxy:           http.ProxyFromEnvironment,
+			DialContext:     TimeoutDialer(r.setting.ConnectTimeout),
+		}
+	} else if t, ok := trans.(*http.Transport); ok {
+		if t.TLSClientConfig == nil {
+			t.TLSClientConfig = r.setting.TLSClientConfig
+		}
+		if t.DialContext == nil {
+			t.DialContext = TimeoutDialer(r.setting.ConnectTimeout)
+		}
+	}
+
+	client := &http.Client{
+		Transport: trans,
+		Timeout:   r.setting.ReadWriteTimeout,
+	}
+
+	if len(r.setting.UserAgent) > 0 && len(r.req.Header.Get("User-Agent")) == 0 {
+		r.req.Header.Set("User-Agent", r.setting.UserAgent)
+	}
+
+	resp, err := client.Do(r.req)
+	if err != nil {
+		return nil, err
+	}
+	r.resp = resp
+	return resp, nil
+}
+
+// Response executes request client gets response manually.
+// Caller MUST close the response body if no error occurs
+func (r *Request) Response() (*http.Response, error) {
+	if r == nil {
+		return nil, errors.New("invalid request")
+	}
+	return r.getResponse()
+}
+
+// TimeoutDialer returns functions of connection dialer with timeout settings for http.Transport Dial field.
+func TimeoutDialer(cTimeout time.Duration) func(ctx context.Context, net, addr string) (c net.Conn, err error) {
+	return func(ctx context.Context, netw, addr string) (net.Conn, error) {
+		d := net.Dialer{Timeout: cTimeout}
+		conn, err := d.DialContext(ctx, netw, addr)
+		if err != nil {
+			return nil, err
+		}
+		return conn, nil
+	}
+}
+
+func (r *Request) GoString() string {
+	return fmt.Sprintf("%s %s", r.req.Method, r.url)
+}
--- a/modules/httplib/serve.go
+++ b/modules/httplib/serve.go
@@ -0,0 +1,234 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httplib
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"path"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"time"
+
+	charsetModule "code.gitea.io/gitea/modules/charset"
+	"code.gitea.io/gitea/modules/container"
+	"code.gitea.io/gitea/modules/httpcache"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/typesniffer"
+	"code.gitea.io/gitea/modules/util"
+
+	"github.com/klauspost/compress/gzhttp"
+)
+
+type ServeHeaderOptions struct {
+	ContentType        string // defaults to "application/octet-stream"
+	ContentTypeCharset string
+	ContentLength      *int64
+	Disposition        string // defaults to "attachment"
+	Filename           string
+	CacheIsPublic      bool
+	CacheDuration      time.Duration // defaults to 5 minutes
+	LastModified       time.Time
+}
+
+// ServeSetHeaders sets necessary content serve headers
+func ServeSetHeaders(w http.ResponseWriter, opts *ServeHeaderOptions) {
+	header := w.Header()
+
+	skipCompressionExts := container.SetOf(".gz", ".bz2", ".zip", ".xz", ".zst", ".deb", ".apk", ".jar", ".png", ".jpg", ".webp")
+	if skipCompressionExts.Contains(strings.ToLower(path.Ext(opts.Filename))) {
+		w.Header().Add(gzhttp.HeaderNoCompression, "1")
+	}
+
+	contentType := typesniffer.MimeTypeApplicationOctetStream
+	if opts.ContentType != "" {
+		if opts.ContentTypeCharset != "" {
+			contentType = opts.ContentType + "; charset=" + strings.ToLower(opts.ContentTypeCharset)
+		} else {
+			contentType = opts.ContentType
+		}
+	}
+	header.Set("Content-Type", contentType)
+	header.Set("X-Content-Type-Options", "nosniff")
+
+	if opts.ContentLength != nil {
+		header.Set("Content-Length", strconv.FormatInt(*opts.ContentLength, 10))
+	}
+
+	if opts.Filename != "" {
+		disposition := opts.Disposition
+		if disposition == "" {
+			disposition = "attachment"
+		}
+
+		backslashEscapedName := strings.ReplaceAll(strings.ReplaceAll(opts.Filename, `\`, `\\`), `"`, `\"`) // \ -> \\, " -> \"
+		header.Set("Content-Disposition", fmt.Sprintf(`%s; filename="%s"; filename*=UTF-8''%s`, disposition, backslashEscapedName, url.PathEscape(opts.Filename)))
+		header.Set("Access-Control-Expose-Headers", "Content-Disposition")
+	}
+
+	httpcache.SetCacheControlInHeader(header, &httpcache.CacheControlOptions{
+		IsPublic:    opts.CacheIsPublic,
+		MaxAge:      opts.CacheDuration,
+		NoTransform: true,
+	})
+
+	if !opts.LastModified.IsZero() {
+		// http.TimeFormat required a UTC time, refer to https://pkg.go.dev/net/http#TimeFormat
+		header.Set("Last-Modified", opts.LastModified.UTC().Format(http.TimeFormat))
+	}
+}
+
+// ServeData download file from io.Reader
+func setServeHeadersByFile(r *http.Request, w http.ResponseWriter, mineBuf []byte, opts *ServeHeaderOptions) {
+	// do not set "Content-Length", because the length could only be set by callers, and it needs to support range requests
+	sniffedType := typesniffer.DetectContentType(mineBuf)
+
+	// the "render" parameter came from year 2016: 638dd24c, it doesn't have clear meaning, so I think it could be removed later
+	isPlain := sniffedType.IsText() || r.FormValue("render") != ""
+
+	if setting.MimeTypeMap.Enabled {
+		fileExtension := strings.ToLower(filepath.Ext(opts.Filename))
+		opts.ContentType = setting.MimeTypeMap.Map[fileExtension]
+	}
+
+	if opts.ContentType == "" {
+		if sniffedType.IsBrowsableBinaryType() {
+			opts.ContentType = sniffedType.GetMimeType()
+		} else if isPlain {
+			opts.ContentType = "text/plain"
+		} else {
+			opts.ContentType = typesniffer.MimeTypeApplicationOctetStream
+		}
+	}
+
+	if isPlain {
+		charset, err := charsetModule.DetectEncoding(mineBuf)
+		if err != nil {
+			log.Error("Detect raw file %s charset failed: %v, using by default utf-8", opts.Filename, err)
+			charset = "utf-8"
+		}
+		opts.ContentTypeCharset = strings.ToLower(charset)
+	}
+
+	isSVG := sniffedType.IsSvgImage()
+
+	// serve types that can present a security risk with CSP
+	if isSVG {
+		w.Header().Set("Content-Security-Policy", "default-src 'none'; style-src 'unsafe-inline'; sandbox")
+	} else if sniffedType.IsPDF() {
+		// no sandbox attribute for pdf as it breaks rendering in at least safari. this
+		// should generally be safe as scripts inside PDF can not escape the PDF document
+		// see https://bugs.chromium.org/p/chromium/issues/detail?id=413851 for more discussion
+		w.Header().Set("Content-Security-Policy", "default-src 'none'; style-src 'unsafe-inline'")
+	}
+
+	opts.Disposition = "inline"
+	if isSVG && !setting.UI.SVG.Enabled {
+		opts.Disposition = "attachment"
+	}
+
+	ServeSetHeaders(w, opts)
+}
+
+const mimeDetectionBufferLen = 1024
+
+func ServeContentByReader(r *http.Request, w http.ResponseWriter, size int64, reader io.Reader, opts *ServeHeaderOptions) {
+	buf := make([]byte, mimeDetectionBufferLen)
+	n, err := util.ReadAtMost(reader, buf)
+	if err != nil {
+		http.Error(w, "serve content: unable to pre-read", http.StatusRequestedRangeNotSatisfiable)
+		return
+	}
+	if n >= 0 {
+		buf = buf[:n]
+	}
+	setServeHeadersByFile(r, w, buf, opts)
+
+	// reset the reader to the beginning
+	reader = io.MultiReader(bytes.NewReader(buf), reader)
+
+	rangeHeader := r.Header.Get("Range")
+
+	// if no size or no supported range, serve as 200 (complete response)
+	if size <= 0 || !strings.HasPrefix(rangeHeader, "bytes=") {
+		if size >= 0 {
+			w.Header().Set("Content-Length", strconv.FormatInt(size, 10))
+		}
+		_, _ = io.Copy(w, reader) // just like http.ServeContent, not necessary to handle the error
+		return
+	}
+
+	// do our best to support the minimal "Range" request (no support for multiple range: "Range: bytes=0-50, 100-150")
+	//
+	// GET /...
+	// Range: bytes=0-1023
+	//
+	// HTTP/1.1 206 Partial Content
+	// Content-Range: bytes 0-1023/146515
+	// Content-Length: 1024
+
+	_, rangeParts, _ := strings.Cut(rangeHeader, "=")
+	rangeBytesStart, rangeBytesEnd, found := strings.Cut(rangeParts, "-")
+	start, err := strconv.ParseInt(rangeBytesStart, 10, 64)
+	if start < 0 || start >= size {
+		err = errors.New("invalid start range")
+	}
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusRequestedRangeNotSatisfiable)
+		return
+	}
+	end, err := strconv.ParseInt(rangeBytesEnd, 10, 64)
+	if rangeBytesEnd == "" && found {
+		err = nil
+		end = size - 1
+	}
+	if end >= size {
+		end = size - 1
+	}
+	if end < start {
+		err = errors.New("invalid end range")
+	}
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	partialLength := end - start + 1
+	w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, size))
+	w.Header().Set("Content-Length", strconv.FormatInt(partialLength, 10))
+	if _, err = io.CopyN(io.Discard, reader, start); err != nil {
+		http.Error(w, "serve content: unable to skip", http.StatusInternalServerError)
+		return
+	}
+
+	w.WriteHeader(http.StatusPartialContent)
+	_, _ = io.CopyN(w, reader, partialLength) // just like http.ServeContent, not necessary to handle the error
+}
+
+func ServeContentByReadSeeker(r *http.Request, w http.ResponseWriter, modTime *time.Time, reader io.ReadSeeker, opts *ServeHeaderOptions) {
+	buf := make([]byte, mimeDetectionBufferLen)
+	n, err := util.ReadAtMost(reader, buf)
+	if err != nil {
+		http.Error(w, "serve content: unable to read", http.StatusInternalServerError)
+		return
+	}
+	if _, err = reader.Seek(0, io.SeekStart); err != nil {
+		http.Error(w, "serve content: unable to seek", http.StatusInternalServerError)
+		return
+	}
+	if n >= 0 {
+		buf = buf[:n]
+	}
+	setServeHeadersByFile(r, w, buf, opts)
+	if modTime == nil {
+		modTime = &time.Time{}
+	}
+	http.ServeContent(w, r, opts.Filename, *modTime, reader)
+}
--- a/modules/httplib/serve_test.go
+++ b/modules/httplib/serve_test.go
@@ -0,0 +1,108 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httplib
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"os"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestServeContentByReader(t *testing.T) {
+	data := "0123456789abcdef"
+
+	test := func(t *testing.T, expectedStatusCode int, expectedContent string) {
+		_, rangeStr, _ := strings.Cut(t.Name(), "_range_")
+		r := &http.Request{Header: http.Header{}, Form: url.Values{}}
+		if rangeStr != "" {
+			r.Header.Set("Range", "bytes="+rangeStr)
+		}
+		reader := strings.NewReader(data)
+		w := httptest.NewRecorder()
+		ServeContentByReader(r, w, int64(len(data)), reader, &ServeHeaderOptions{})
+		assert.Equal(t, expectedStatusCode, w.Code)
+		if expectedStatusCode == http.StatusPartialContent || expectedStatusCode == http.StatusOK {
+			assert.Equal(t, strconv.Itoa(len(expectedContent)), w.Header().Get("Content-Length"))
+			assert.Equal(t, expectedContent, w.Body.String())
+		}
+	}
+
+	t.Run("_range_", func(t *testing.T) {
+		test(t, http.StatusOK, data)
+	})
+	t.Run("_range_0-", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data)
+	})
+	t.Run("_range_0-15", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data)
+	})
+	t.Run("_range_1-", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data[1:])
+	})
+	t.Run("_range_1-3", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data[1:3+1])
+	})
+	t.Run("_range_16-", func(t *testing.T) {
+		test(t, http.StatusRequestedRangeNotSatisfiable, "")
+	})
+	t.Run("_range_1-99999", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data[1:])
+	})
+}
+
+func TestServeContentByReadSeeker(t *testing.T) {
+	data := "0123456789abcdef"
+	tmpFile := t.TempDir() + "/test"
+	err := os.WriteFile(tmpFile, []byte(data), 0o644)
+	assert.NoError(t, err)
+
+	test := func(t *testing.T, expectedStatusCode int, expectedContent string) {
+		_, rangeStr, _ := strings.Cut(t.Name(), "_range_")
+		r := &http.Request{Header: http.Header{}, Form: url.Values{}}
+		if rangeStr != "" {
+			r.Header.Set("Range", "bytes="+rangeStr)
+		}
+
+		seekReader, err := os.OpenFile(tmpFile, os.O_RDONLY, 0o644)
+		require.NoError(t, err)
+		defer seekReader.Close()
+
+		w := httptest.NewRecorder()
+		ServeContentByReadSeeker(r, w, nil, seekReader, &ServeHeaderOptions{})
+		assert.Equal(t, expectedStatusCode, w.Code)
+		if expectedStatusCode == http.StatusPartialContent || expectedStatusCode == http.StatusOK {
+			assert.Equal(t, strconv.Itoa(len(expectedContent)), w.Header().Get("Content-Length"))
+			assert.Equal(t, expectedContent, w.Body.String())
+		}
+	}
+
+	t.Run("_range_", func(t *testing.T) {
+		test(t, http.StatusOK, data)
+	})
+	t.Run("_range_0-", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data)
+	})
+	t.Run("_range_0-15", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data)
+	})
+	t.Run("_range_1-", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data[1:])
+	})
+	t.Run("_range_1-3", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data[1:3+1])
+	})
+	t.Run("_range_16-", func(t *testing.T) {
+		test(t, http.StatusRequestedRangeNotSatisfiable, "")
+	})
+	t.Run("_range_1-99999", func(t *testing.T) {
+		test(t, http.StatusPartialContent, data[1:])
+	})
+}
--- a/modules/httplib/url.go
+++ b/modules/httplib/url.go
@@ -0,0 +1,184 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httplib
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+)
+
+type RequestContextKeyStruct struct{}
+
+var RequestContextKey = RequestContextKeyStruct{}
+
+func urlIsRelative(s string, u *url.URL) bool {
+	// Unfortunately browsers consider a redirect Location with preceding "//", "\\", "/\" and "\/" as meaning redirect to "http(s)://REST_OF_PATH"
+	// Therefore we should ignore these redirect locations to prevent open redirects
+	if len(s) > 1 && (s[0] == '/' || s[0] == '\\') && (s[1] == '/' || s[1] == '\\') {
+		return false
+	}
+	return u != nil && u.Scheme == "" && u.Host == ""
+}
+
+// IsRelativeURL detects if a URL is relative (no scheme or host)
+func IsRelativeURL(s string) bool {
+	u, err := url.Parse(s)
+	return err == nil && urlIsRelative(s, u)
+}
+
+func getRequestScheme(req *http.Request) string {
+	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto
+	if s := req.Header.Get("X-Forwarded-Proto"); s != "" {
+		return s
+	}
+	if s := req.Header.Get("X-Forwarded-Protocol"); s != "" {
+		return s
+	}
+	if s := req.Header.Get("X-Url-Scheme"); s != "" {
+		return s
+	}
+	if s := req.Header.Get("Front-End-Https"); s != "" {
+		return util.Iif(s == "on", "https", "http")
+	}
+	if s := req.Header.Get("X-Forwarded-Ssl"); s != "" {
+		return util.Iif(s == "on", "https", "http")
+	}
+	return ""
+}
+
+// GuessCurrentAppURL tries to guess the current full public URL (with sub-path) by http headers. It always has a '/' suffix, exactly the same as setting.AppURL
+// TODO: should rename it to GuessCurrentPublicURL in the future
+func GuessCurrentAppURL(ctx context.Context) string {
+	return GuessCurrentHostURL(ctx) + setting.AppSubURL + "/"
+}
+
+// GuessCurrentHostURL tries to guess the current full host URL (no sub-path) by http headers, there is no trailing slash.
+func GuessCurrentHostURL(ctx context.Context) string {
+	// Try the best guess to get the current host URL (will be used for public URL) by http headers.
+	// At the moment, if site admin doesn't configure the proxy headers correctly, then Gitea would guess wrong.
+	// There are some cases:
+	// 1. The reverse proxy is configured correctly, it passes "X-Forwarded-Proto/Host" headers. Perfect, Gitea can handle it correctly.
+	// 2. The reverse proxy is not configured correctly, doesn't pass "X-Forwarded-Proto/Host" headers, eg: only one "proxy_pass http://gitea:3000" in Nginx.
+	// 3. There is no reverse proxy.
+	// Without more information, Gitea is impossible to distinguish between case 2 and case 3, then case 2 would result in
+	// wrong guess like guessed public URL becomes "http://gitea:3000/" behind a "https" reverse proxy, which is not accessible by end users.
+	// So we introduced "PUBLIC_URL_DETECTION" option, to control the guessing behavior to satisfy different use cases.
+	req, ok := ctx.Value(RequestContextKey).(*http.Request)
+	if !ok {
+		return strings.TrimSuffix(setting.AppURL, setting.AppSubURL+"/")
+	}
+	reqScheme := getRequestScheme(req)
+	if reqScheme == "" {
+		// if no reverse proxy header, try to use "Host" header for absolute URL
+		if setting.PublicURLDetection == setting.PublicURLAuto && req.Host != "" {
+			return util.Iif(req.TLS == nil, "http://", "https://") + req.Host
+		}
+		// fall back to default AppURL
+		return strings.TrimSuffix(setting.AppURL, setting.AppSubURL+"/")
+	}
+	// X-Forwarded-Host has many problems: non-standard, not well-defined (X-Forwarded-Port or not), conflicts with Host header.
+	// So do not use X-Forwarded-Host, just use Host header directly.
+	return reqScheme + "://" + req.Host
+}
+
+func GuessCurrentHostDomain(ctx context.Context) string {
+	_, host, _ := strings.Cut(GuessCurrentHostURL(ctx), "://")
+	domain, _, _ := net.SplitHostPort(host)
+	return util.IfZero(domain, host)
+}
+
+// MakeAbsoluteURL tries to make a link to an absolute public URL:
+// * If link is empty, it returns the current public URL.
+// * If link is absolute, it returns the link.
+// * Otherwise, it returns the current host URL + link, the link itself should have correct sub-path (AppSubURL) if needed.
+func MakeAbsoluteURL(ctx context.Context, link string) string {
+	if link == "" {
+		return GuessCurrentAppURL(ctx)
+	}
+	if !IsRelativeURL(link) {
+		return link
+	}
+	return GuessCurrentHostURL(ctx) + "/" + strings.TrimPrefix(link, "/")
+}
+
+type urlType int
+
+const (
+	urlTypeGiteaAbsolute     urlType = iota + 1 // "http://gitea/subpath"
+	urlTypeGiteaPageRelative                    // "/subpath"
+	urlTypeGiteaSiteRelative                    // "?key=val"
+	urlTypeUnknown                              // "http://other"
+)
+
+func detectURLRoutePath(ctx context.Context, s string) (routePath string, ut urlType) {
+	u, err := url.Parse(s)
+	if err != nil {
+		return "", urlTypeUnknown
+	}
+	cleanedPath := ""
+	if u.Path != "" {
+		cleanedPath = util.PathJoinRelX(u.Path)
+		cleanedPath = util.Iif(cleanedPath == ".", "", "/"+cleanedPath)
+	}
+	if urlIsRelative(s, u) {
+		if u.Path == "" {
+			return "", urlTypeGiteaPageRelative
+		}
+		if strings.HasPrefix(strings.ToLower(cleanedPath+"/"), strings.ToLower(setting.AppSubURL+"/")) {
+			return cleanedPath[len(setting.AppSubURL):], urlTypeGiteaSiteRelative
+		}
+		return "", urlTypeUnknown
+	}
+	u.Path = cleanedPath + "/"
+	urlLower := strings.ToLower(u.String())
+	if strings.HasPrefix(urlLower, strings.ToLower(setting.AppURL)) {
+		return cleanedPath[len(setting.AppSubURL):], urlTypeGiteaAbsolute
+	}
+	guessedCurURL := GuessCurrentAppURL(ctx)
+	if strings.HasPrefix(urlLower, strings.ToLower(guessedCurURL)) {
+		return cleanedPath[len(setting.AppSubURL):], urlTypeGiteaAbsolute
+	}
+	return "", urlTypeUnknown
+}
+
+func IsCurrentGiteaSiteURL(ctx context.Context, s string) bool {
+	_, ut := detectURLRoutePath(ctx, s)
+	return ut != urlTypeUnknown
+}
+
+type GiteaSiteURL struct {
+	RoutePath   string
+	OwnerName   string
+	RepoName    string
+	RepoSubPath string
+}
+
+func ParseGiteaSiteURL(ctx context.Context, s string) *GiteaSiteURL {
+	routePath, ut := detectURLRoutePath(ctx, s)
+	if ut == urlTypeUnknown || ut == urlTypeGiteaPageRelative {
+		return nil
+	}
+	ret := &GiteaSiteURL{RoutePath: routePath}
+	fields := strings.SplitN(strings.TrimPrefix(ret.RoutePath, "/"), "/", 3)
+
+	// TODO: now it only does a quick check for some known reserved paths, should do more strict checks in the future
+	if fields[0] == "attachments" {
+		return ret
+	}
+	if len(fields) < 2 {
+		return ret
+	}
+	ret.OwnerName = fields[0]
+	ret.RepoName = fields[1]
+	if len(fields) == 3 {
+		ret.RepoSubPath = "/" + fields[2]
+	}
+	return ret
+}
--- a/modules/httplib/url_test.go
+++ b/modules/httplib/url_test.go
@@ -0,0 +1,184 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package httplib
+
+import (
+	"context"
+	"crypto/tls"
+	"net/http"
+	"testing"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsRelativeURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	rel := []string{
+		"",
+		"foo",
+		"/",
+		"/foo?k=%20#abc",
+	}
+	for _, s := range rel {
+		assert.True(t, IsRelativeURL(s), "rel = %q", s)
+	}
+	abs := []string{
+		"//",
+		"\\\\",
+		"/\\",
+		"\\/",
+		"mailto:a@b.com",
+		"https://test.com",
+	}
+	for _, s := range abs {
+		assert.False(t, IsRelativeURL(s), "abs = %q", s)
+	}
+}
+
+func TestGuessCurrentHostURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, "http://cfg-host/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	headersWithProto := http.Header{"X-Forwarded-Proto": {"https"}}
+
+	t.Run("Legacy", func(t *testing.T) {
+		defer test.MockVariableValue(&setting.PublicURLDetection, setting.PublicURLLegacy)()
+
+		assert.Equal(t, "http://cfg-host", GuessCurrentHostURL(t.Context()))
+
+		// legacy: "Host" is not used when there is no "X-Forwarded-Proto" header
+		ctx := context.WithValue(t.Context(), RequestContextKey, &http.Request{Host: "req-host:3000"})
+		assert.Equal(t, "http://cfg-host", GuessCurrentHostURL(ctx))
+
+		// if "X-Forwarded-Proto" exists, then use it and "Host" header
+		ctx = context.WithValue(t.Context(), RequestContextKey, &http.Request{Host: "req-host:3000", Header: headersWithProto})
+		assert.Equal(t, "https://req-host:3000", GuessCurrentHostURL(ctx))
+	})
+
+	t.Run("Auto", func(t *testing.T) {
+		defer test.MockVariableValue(&setting.PublicURLDetection, setting.PublicURLAuto)()
+
+		assert.Equal(t, "http://cfg-host", GuessCurrentHostURL(t.Context()))
+
+		// auto: always use "Host" header, the scheme is determined by "X-Forwarded-Proto" header, or TLS config if no "X-Forwarded-Proto" header
+		ctx := context.WithValue(t.Context(), RequestContextKey, &http.Request{Host: "req-host:3000"})
+		assert.Equal(t, "http://req-host:3000", GuessCurrentHostURL(ctx))
+
+		ctx = context.WithValue(t.Context(), RequestContextKey, &http.Request{Host: "req-host", TLS: &tls.ConnectionState{}})
+		assert.Equal(t, "https://req-host", GuessCurrentHostURL(ctx))
+
+		ctx = context.WithValue(t.Context(), RequestContextKey, &http.Request{Host: "req-host:3000", Header: headersWithProto})
+		assert.Equal(t, "https://req-host:3000", GuessCurrentHostURL(ctx))
+	})
+}
+
+func TestMakeAbsoluteURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.Protocol, "http")()
+	defer test.MockVariableValue(&setting.AppURL, "http://cfg-host/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+
+	ctx := t.Context()
+	assert.Equal(t, "http://cfg-host/sub/", MakeAbsoluteURL(ctx, ""))
+	assert.Equal(t, "http://cfg-host/foo", MakeAbsoluteURL(ctx, "foo"))
+	assert.Equal(t, "http://cfg-host/foo", MakeAbsoluteURL(ctx, "/foo"))
+	assert.Equal(t, "http://other/foo", MakeAbsoluteURL(ctx, "http://other/foo"))
+
+	ctx = context.WithValue(ctx, RequestContextKey, &http.Request{
+		Host: "user-host",
+	})
+	assert.Equal(t, "http://cfg-host/foo", MakeAbsoluteURL(ctx, "/foo"))
+
+	ctx = context.WithValue(ctx, RequestContextKey, &http.Request{
+		Host: "user-host",
+		Header: map[string][]string{
+			"X-Forwarded-Host": {"forwarded-host"},
+		},
+	})
+	assert.Equal(t, "http://cfg-host/foo", MakeAbsoluteURL(ctx, "/foo"))
+
+	ctx = context.WithValue(ctx, RequestContextKey, &http.Request{
+		Host: "user-host",
+		Header: map[string][]string{
+			"X-Forwarded-Host":  {"forwarded-host"},
+			"X-Forwarded-Proto": {"https"},
+		},
+	})
+	assert.Equal(t, "https://user-host/foo", MakeAbsoluteURL(ctx, "/foo"))
+}
+
+func TestIsCurrentGiteaSiteURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	ctx := t.Context()
+	good := []string{
+		"?key=val",
+		"/sub",
+		"/sub/",
+		"/sub/foo",
+		"/sub/foo/",
+		"http://localhost:3000/sub?key=val",
+		"http://localhost:3000/sub/",
+	}
+	for _, s := range good {
+		assert.True(t, IsCurrentGiteaSiteURL(ctx, s), "good = %q", s)
+	}
+	bad := []string{
+		".",
+		"foo",
+		"/",
+		"//",
+		"\\\\",
+		"/foo",
+		"http://localhost:3000/sub/..",
+		"http://localhost:3000/other",
+		"http://other/",
+	}
+	for _, s := range bad {
+		assert.False(t, IsCurrentGiteaSiteURL(ctx, s), "bad = %q", s)
+	}
+
+	setting.AppURL = "http://localhost:3000/"
+	setting.AppSubURL = ""
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "//"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "\\\\"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "http://localhost"))
+	assert.True(t, IsCurrentGiteaSiteURL(ctx, "http://localhost:3000?key=val"))
+
+	ctx = context.WithValue(ctx, RequestContextKey, &http.Request{
+		Host: "user-host",
+		Header: map[string][]string{
+			"X-Forwarded-Host":  {"forwarded-host"},
+			"X-Forwarded-Proto": {"https"},
+		},
+	})
+	assert.True(t, IsCurrentGiteaSiteURL(ctx, "http://localhost:3000"))
+	assert.True(t, IsCurrentGiteaSiteURL(ctx, "https://user-host"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "https://forwarded-host"))
+}
+
+func TestParseGiteaSiteURL(t *testing.T) {
+	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
+	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	ctx := t.Context()
+	tests := []struct {
+		url string
+		exp *GiteaSiteURL
+	}{
+		{"http://localhost:3000/sub?k=v", &GiteaSiteURL{RoutePath: ""}},
+		{"http://localhost:3000/sub/", &GiteaSiteURL{RoutePath: ""}},
+		{"http://localhost:3000/sub/foo", &GiteaSiteURL{RoutePath: "/foo"}},
+		{"http://localhost:3000/sub/foo/bar", &GiteaSiteURL{RoutePath: "/foo/bar", OwnerName: "foo", RepoName: "bar"}},
+		{"http://localhost:3000/sub/foo/bar/", &GiteaSiteURL{RoutePath: "/foo/bar", OwnerName: "foo", RepoName: "bar"}},
+		{"http://localhost:3000/sub/attachments/bar", &GiteaSiteURL{RoutePath: "/attachments/bar"}},
+		{"http://localhost:3000/other", nil},
+		{"http://other/", nil},
+	}
+	for _, test := range tests {
+		su := ParseGiteaSiteURL(ctx, test.url)
+		assert.Equal(t, test.exp, su, "URL = %s", test.url)
+	}
+}