fix: various security fixes (#38406)

Addresses a batch of privately reported security issues, grouped by
area:

- **SSRF** - migration PR-patch/asset fetches, OAuth2 avatar & OpenID
discovery, pull-mirror URL re-validation, and the outbound proxy path.
- **Access-token scope** - prevent scope escalation on token creation;
keep public-only tokens confined (feeds, packages, Actions listings,
star/watch lists, limited/private owners).
- **Access control / disclosure** - go-get default-branch leak, webhook
authorization-header leak, watch clearing on private transitions,
label/attachment scoping.
- **Denial of service** - input bounds for npm dist-tags, Debian control
files, Arch file lists, and SSH keys.

### 📌 Attention for site admins

Not breaking - existing configs keep working - but two changes are worth
a look:

- **New SSRF protection** Outbound requests (migrations, OAuth2 avatars,
OpenID discovery, pull mirrors, proxy path) are now validated against
the allow/block host lists. If your instance legitimately reaches
internal hosts, you may need to add them to
`[security].ALLOWED_HOST_LIST` (and the relevant `ALLOW_LOCALNETWORKS`
settings).
- **Deprecation** `[webhook].ALLOWED_HOST_LIST` is deprecated and will
be removed in a future release. Use `[security].ALLOWED_HOST_LIST`
instead; the old key still works for now.

---------

Co-authored-by: TheFox0x7 <thefox0x7@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>

modules/auth/openid/openid.go

@@ -4,8 +4,14 @@
 package openid
 
 import (
+	"net/http"
+	"sync"
 	"time"
 
+	"gitea.dev/modules/hostmatcher"
+	"gitea.dev/modules/proxy"
+	"gitea.dev/modules/setting"
+
 	"github.com/yohcop/openid-go"
 )
 
@@ -19,11 +25,23 @@ import (
 var (
 	nonceStore     = openid.NewSimpleNonceStore()
 	discoveryCache = newTimedDiscoveryCache(24 * time.Hour)
+
+	// openIDInstance does discovery/verification via an SSRF-protected client, so a user-supplied
+	// OpenID identifier can't reach internal/loopback/reserved addresses. It honors the operator's
+	// [security] ALLOWED_HOST_LIST (empty defaults to "external"), matching the avatar/webhook/migration
+	// clients, and validates the proxy path too. Lazy: reads proxy/settings once.
+	openIDInstance = sync.OnceValue(func() *openid.OpenID {
+		allowList := hostmatcher.ParseHostMatchList("security.ALLOWED_HOST_LIST", setting.Security.AllowedHostList)
+		return openid.NewOpenID(&http.Client{
+			Timeout:   30 * time.Second,
+			Transport: hostmatcher.NewHTTPTransport("openid", allowList, nil, proxy.Proxy(), setting.Proxy.ProxyURLFixed, nil),
+		})
+	})
 )
 
 // Verify handles response from OpenID provider
 func Verify(fullURL string) (id string, err error) {
-	return openid.Verify(fullURL, discoveryCache, nonceStore)
+	return openIDInstance().Verify(fullURL, discoveryCache, nonceStore)
 }
 
 // Normalize normalizes an OpenID URI
@@ -33,5 +51,5 @@ func Normalize(url string) (id string, err error) {
 
 // RedirectURL redirects browser
 func RedirectURL(id, callbackURL, realm string) (string, error) {
-	return openid.RedirectURL(id, callbackURL, realm)
+	return openIDInstance().RedirectURL(id, callbackURL, realm)
 }

modules/auth/openid/openid_test.go

@@ -0,0 +1,29 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package openid
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"sync/atomic"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestOpenIDDiscoveryBlocksInternalHost(t *testing.T) {
+	var reached atomic.Bool
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		reached.Store(true)
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer srv.Close()
+
+	// RedirectURL performs server-side discovery of the identifier URL; a loopback URL
+	// must be refused at dial time instead of reaching the internal server
+	_, err := RedirectURL(srv.URL, "http://example.com/callback", "http://example.com/")
+	require.Error(t, err)
+	assert.False(t, reached.Load(), "OpenID discovery must not reach an internal/loopback host")
+}

modules/hostmatcher/http.go

@@ -5,8 +5,10 @@ package hostmatcher
 
 import (
 	"context"
+	"crypto/tls"
 	"fmt"
 	"net"
+	"net/http"
 	"net/url"
 	"syscall"
 	"time"
@@ -63,3 +65,17 @@ func NewDialContext(usage string, allowList, blockList *HostMatchList, proxy *ur
 		return dialer.DialContext(ctx, network, addrOrHost)
 	}
 }
+
+// NewHTTPTransport builds an http.Transport that validates the request target against the allow/block
+// lists on the direct-dial path (DialContext). When an HTTP proxy is configured the proxy resolves and
+// dials the target itself, so restricting the proxied target is the proxy server's responsibility, not
+// Gitea's. proxyFunc selects the proxy URL per request (the http.Transport.Proxy selector, e.g.
+// proxy.Proxy()); proxyURLFixed is the fixed proxy address the dialer must always permit; tlsConfig may
+// be nil. blockList may be nil for callers that only maintain an allow-list.
+func NewHTTPTransport(usage string, allowList, blockList *HostMatchList, proxyFunc func(*http.Request) (*url.URL, error), proxyURLFixed *url.URL, tlsConfig *tls.Config) *http.Transport {
+	return &http.Transport{
+		TLSClientConfig: tlsConfig,
+		Proxy:           proxyFunc,
+		DialContext:     NewDialContext(usage, allowList, blockList, proxyURLFixed),
+	}
+}

modules/packages/arch/metadata.go

@@ -13,6 +13,7 @@ import (
 	"strconv"
 	"strings"
 
+	"gitea.dev/modules/packages"
 	"gitea.dev/modules/util"
 	"gitea.dev/modules/validation"
 
@@ -46,6 +47,11 @@ var (
 	namePattern = regexp.MustCompile(`\A[a-zA-Z0-9@._+-]+\z`)
 	// (epoch:pkgver-pkgrel)
 	versionPattern = regexp.MustCompile(`\A(?:\d:)?[\w.+~]+(?:-[-\w.+~]+)?\z`)
+
+	// caps on the accumulated package file list (vars so tests can lower them); far above
+	// any legitimate package, but low enough to stop metadata amplification
+	maxFileEntries   = 100000
+	maxFileNameBytes = 16 * 1024 * 1024
 )
 
 type Package struct {
@@ -124,7 +130,7 @@ func ParsePackage(r io.Reader) (*Package, error) {
 	}
 
 	var p *Package
-	files := make([]string, 0, 10)
+	files := packages.NewBoundedFileList(maxFileEntries, maxFileNameBytes)
 
 	tr := tar.NewReader(inner)
 	for {
@@ -147,7 +153,9 @@ func ParsePackage(r io.Reader) (*Package, error) {
 				return nil, err
 			}
 		} else if !strings.HasPrefix(filename, ".") {
-			files = append(files, hd.Name)
+			if err := files.Add(hd.Name); err != nil {
+				return nil, err
+			}
 		}
 	}
 
@@ -155,7 +163,7 @@ func ParsePackage(r io.Reader) (*Package, error) {
 		return nil, ErrMissingPKGINFOFile
 	}
 
-	p.FileMetadata.Files = files
+	p.FileMetadata.Files = files.Files()
 	p.FileCompressionExtension = compressionType
 
 	return p, nil

modules/packages/arch/metadata_test.go

@@ -10,6 +10,9 @@ import (
 	"io"
 	"testing"
 
+	"gitea.dev/modules/test"
+	"gitea.dev/modules/util"
+
 	"github.com/klauspost/compress/zstd"
 	"github.com/stretchr/testify/assert"
 	"github.com/ulikunitz/xz"
@@ -167,3 +170,25 @@ func TestParsePackageInfo(t *testing.T) {
 		assert.ElementsMatch(t, []string{"usr/bin/paket1"}, p.FileMetadata.Backup)
 	})
 }
+
+// TestParsePackageTooManyFiles ensures the accumulated file list is bounded to prevent
+// metadata amplification from a package with a huge number of (tiny) file entries.
+func TestParsePackageTooManyFiles(t *testing.T) {
+	defer test.MockVariableValue(&maxFileEntries, 3)()
+	buf := test.WriteTarCompression(func(w io.Writer) io.WriteCloser { return gzip.NewWriter(w) }, map[string]string{
+		"file1":    "content1",
+		".PKGINFO": string(createPKGINFOContent(packageName, packageVersion)),
+	})
+	_, err := ParsePackage(buf)
+	assert.NoError(t, err)
+
+	buf = test.WriteTarCompression(func(w io.Writer) io.WriteCloser { return gzip.NewWriter(w) }, map[string]string{
+		"file1":    "content1",
+		"file2":    "content2",
+		"file3":    "content3",
+		"file4":    "content4",
+		".PKGINFO": string(createPKGINFOContent(packageName, packageVersion)),
+	})
+	_, err = ParsePackage(buf)
+	assert.ErrorIs(t, err, util.ErrInvalidArgument)
+}

modules/packages/debian/metadata.go

@@ -135,7 +135,10 @@ func ParsePackage(r io.Reader) (*Package, error) {
 				return nil, GlobalVars().ErrUnsupportedCompression
 			}
 
-			tr := tar.NewReader(inner)
+			// bound the decompressed control archive: it holds only the small control file
+			// and maintainer scripts, so a much larger stream is a decompression bomb
+			const maxControlTarSize = 32 * 1024 * 1024
+			tr := tar.NewReader(io.LimitReader(inner, maxControlTarSize))
 			for {
 				hd, err := tr.Next()
 				if err == io.EOF {
@@ -168,6 +171,7 @@ func ParseControlFile(r io.Reader) (*Package, error) {
 	key := ""
 	var depends strings.Builder
 	var control strings.Builder
+	var description strings.Builder
 
 	// https://www.debian.org/doc/debian-policy/ch-controlfields.html#syntax-of-control-files
 	s := bufio.NewScanner(r)
@@ -189,10 +193,13 @@ func ParseControlFile(r io.Reader) (*Package, error) {
 		control.WriteString(line)
 		control.WriteByte('\n')
 
+		// a leading space or tab marks a folded continuation line that belongs to the previous field
+		// (identified by key), not a new "Key: value" pair; only the multi-line fields append here.
+		// Continuation lines may themselves contain a colon, so they must not be re-split on ":".
 		if line[0] == ' ' || line[0] == '\t' {
 			switch key {
 			case "Description":
-				p.Metadata.Description += line
+				description.WriteString(line)
 			case "Depends":
 				depends.WriteString(trimmed)
 			}
@@ -219,7 +226,8 @@ func ParseControlFile(r io.Reader) (*Package, error) {
 					p.Metadata.Maintainer = a.Name
 				}
 			case "Description":
-				p.Metadata.Description = value
+				description.Reset()
+				description.WriteString(value)
 			case "Depends":
 				depends.WriteString(value)
 			case "Homepage":
@@ -243,6 +251,8 @@ func ParseControlFile(r io.Reader) (*Package, error) {
 		return nil, GlobalVars().ErrInvalidArchitecture
 	}
 
+	p.Metadata.Description = description.String()
+
 	dependencies := strings.Split(depends.String(), ",")
 	for i := range dependencies {
 		dependencies[i] = strings.TrimSpace(dependencies[i])

modules/packages/debian/metadata_test.go

@@ -232,3 +232,15 @@ func TestValidateDistributionOrComponent(t *testing.T) {
 		assert.True(t, IsValidDistributionOrComponent(name), "good=%q", name)
 	}
 }
+
+// TestParseControlFileMultilineDescription verifies a multi-line Description is assembled in order
+// (the parser accumulates it in a strings.Builder); it guards the assembled value, not its timing.
+func TestParseControlFileMultilineDescription(t *testing.T) {
+	var buf bytes.Buffer
+	buf.WriteString("Package: testpkg\nVersion: 1.0\nArchitecture: amd64\nDescription: short summary\n more details\n even more\n")
+
+	p, err := ParseControlFile(&buf)
+	assert.NoError(t, err)
+	assert.NotNil(t, p)
+	assert.Equal(t, "short summary more details even more", p.Metadata.Description)
+}

modules/packages/filelist.go

@@ -0,0 +1,37 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package packages
+
+import "gitea.dev/modules/util"
+
+// BoundedFileList accumulates file names from a package archive while enforcing caps on the number of
+// entries and their total name length, returning an error once either cap would be exceeded.
+type BoundedFileList struct {
+	files     []string
+	nameBytes int
+	maxFiles  int
+	maxBytes  int
+}
+
+// NewBoundedFileList creates a BoundedFileList with the given caps; a non-positive cap falls back to the
+// corresponding default.
+func NewBoundedFileList(maxFiles, maxNameBytes int) *BoundedFileList {
+	return &BoundedFileList{maxFiles: maxFiles, maxBytes: maxNameBytes}
+}
+
+// Add appends name, returning util.ErrInvalidArgument once the entry count or accumulated byte length
+// would exceed the configured cap.
+func (b *BoundedFileList) Add(name string) error {
+	if len(b.files) >= b.maxFiles || b.nameBytes+len(name) > b.maxBytes {
+		return util.NewInvalidArgumentErrorf("package contains too many file entries")
+	}
+	b.nameBytes += len(name)
+	b.files = append(b.files, name)
+	return nil
+}
+
+// Files returns the accumulated file names.
+func (b *BoundedFileList) Files() []string {
+	return b.files
+}

modules/private/internal.go

@@ -8,6 +8,7 @@ import (
 	"crypto/tls"
 	"net"
 	"net/http"
+	"net/url"
 	"os"
 	"strings"
 	"sync"
@@ -53,12 +54,37 @@ func dialContextInternalAPI(ctx context.Context, network, address string) (conn
 	return conn, nil
 }
 
+// internalAPIConnectionIsLocal reports whether the internal API transport connects to a local target,
+// where the self-signed local certificate cannot be verified so skipping verification is safe. It mirrors
+// what dialContextInternalAPI actually dials: a unix socket whenever Protocol is HTTPUnix (always local,
+// whatever LOCAL_ROOT_URL says), otherwise the LOCAL_ROOT_URL host directly. A non-loopback LOCAL_ROOT_URL
+// is a real network hop, so its certificate must be verified, else the internal token can be MITM'd. An
+// unparseable LOCAL_ROOT_URL is a hard misconfiguration and fails closed (verify).
+func internalAPIConnectionIsLocal(protocol setting.Scheme, localURL string) bool {
+	if protocol == setting.HTTPUnix {
+		return true
+	}
+	u, err := url.Parse(localURL)
+	if err != nil {
+		return false
+	}
+	host := u.Hostname()
+	if host == "localhost" {
+		return true
+	}
+	ip := net.ParseIP(host)
+	return ip != nil && ip.IsLoopback()
+}
+
 var internalAPITransport = sync.OnceValue(func() http.RoundTripper {
 	return &http.Transport{
 		DialContext: dialContextInternalAPI,
 		TLSClientConfig: &tls.Config{
-			InsecureSkipVerify: true,
-			ServerName:         setting.Domain,
+			// Skip verification only for a local target (unix socket, or a loopback LOCAL_ROOT_URL), where the
+			// self-signed local cert can't be verified anyway; a non-loopback LOCAL_ROOT_URL is a real network
+			// hop and must be verified so the internal token can't be MITM'd. When verifying, Go's default
+			// ServerName (the dialed LOCAL_ROOT_URL host) is already correct, so it is not overridden.
+			InsecureSkipVerify: internalAPIConnectionIsLocal(setting.Protocol, setting.LocalURL),
 		},
 	}
 })

modules/private/internal_test.go

@@ -0,0 +1,37 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package private
+
+import (
+	"testing"
+
+	"gitea.dev/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestInternalAPIConnectionIsLocal(t *testing.T) {
+	cases := []struct {
+		name     string
+		protocol setting.Scheme
+		localURL string
+		want     bool
+	}{
+		// HTTPUnix always dials the unix socket (a local target), whatever LOCAL_ROOT_URL says
+		{"unix socket", setting.HTTPUnix, "https://gitea.example.com/", true},
+		{"localhost", setting.HTTP, "http://localhost:3000/", true},
+		{"loopback ipv4", setting.HTTPS, "https://127.0.0.1:3000/", true},
+		{"loopback ipv6", setting.HTTPS, "https://[::1]:3000/", true},
+		// a non-loopback LOCAL_ROOT_URL is a real network hop and must be verified
+		{"remote host", setting.HTTPS, "https://gitea.internal:443/", false},
+		{"remote ip", setting.HTTPS, "https://10.0.0.5:3000/", false},
+		// an unparseable LOCAL_ROOT_URL is a hard misconfiguration; fail closed to verification
+		{"invalid url", setting.HTTPS, "://bad", false},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			assert.Equal(t, c.want, internalAPIConnectionIsLocal(c.protocol, c.localURL))
+		})
+	}
+}

modules/setting/security.go

@@ -20,9 +20,11 @@ var Security = struct {
 	XContentTypeOptions string
 
 	ContentSecurityPolicyGeneral string // it only supports empty (default policy) or "unset", maybe it can support more in the future
+	AllowedHostList              string
 }{
 	XFrameOptions:       "SAMEORIGIN",
 	XContentTypeOptions: "nosniff",
+	AllowedHostList:     "external",
 }
 
 var (

modules/setting/security_test.go

@@ -10,13 +10,20 @@ import (
 )
 
 func TestLoadSecurityFrom(t *testing.T) {
+	assert.Equal(t, "SAMEORIGIN", Security.XFrameOptions)
+	assert.Equal(t, "nosniff", Security.XContentTypeOptions)
+	assert.Equal(t, "external", Security.AllowedHostList)
+
 	cfg, err := NewConfigProviderFromData(`[security]
 X_FRAME_OPTIONS = DENY
 X_CONTENT_TYPE_OPTIONS = unset
-CONTENT_SECURITY_POLICY_GENERAL = "script-src *; foo"`)
+ALLOWED_HOST_LIST = foo
+CONTENT_SECURITY_POLICY_GENERAL = "script-src *; foo"
+`)
 	assert.NoError(t, err)
 	loadSecurityFrom(cfg)
 	assert.Equal(t, "DENY", Security.XFrameOptions)
 	assert.Equal(t, "unset", Security.XContentTypeOptions)
+	assert.Equal(t, "foo", Security.AllowedHostList)
 	assert.Equal(t, `"script-src *`, Security.ContentSecurityPolicyGeneral) // holy shit ini package bug
 }

modules/setting/webhook.go

@@ -34,7 +34,10 @@ func loadWebhookFrom(rootCfg ConfigProvider) {
 	Webhook.QueueLength = sec.Key("QUEUE_LENGTH").MustInt(1000)
 	Webhook.DeliverTimeout = sec.Key("DELIVER_TIMEOUT").MustInt(5)
 	Webhook.SkipTLSVerify = sec.Key("SKIP_TLS_VERIFY").MustBool()
-	Webhook.AllowedHostList = sec.Key("ALLOWED_HOST_LIST").MustString("")
+
+	deprecatedSetting(rootCfg, "webhook", "ALLOWED_HOST_LIST", "security", "ALLOWED_HOST_LIST", "v28.0.0")
+	Webhook.AllowedHostList = sec.Key("ALLOWED_HOST_LIST").MustString(Security.AllowedHostList)
+
 	Webhook.Types = []string{"gitea", "gogs", "slack", "discord", "dingtalk", "telegram", "msteams", "feishu", "matrix", "wechatwork", "packagist"}
 	Webhook.PagingNum = sec.Key("PAGING_NUM").MustInt(10)
 	Webhook.ProxyURL = sec.Key("PROXY_URL").MustString("")

modules/uri/uri.go

@@ -23,13 +23,21 @@ func (e ErrURISchemeNotSupported) Error() string {
 
 // Open open a local file or a remote file
 func Open(uriStr string) (io.ReadCloser, error) {
+	return OpenWithClient(uriStr, http.DefaultClient)
+}
+
+// OpenWithClient opens a local file or a remote file, using the given (non-nil) HTTP client
+// for http/https URLs. Callers that must confine remote access (e.g. to defeat SSRF via
+// redirects) should pass a client whose transport validates the peer at dial time; Open
+// passes http.DefaultClient.
+func OpenWithClient(uriStr string, client *http.Client) (io.ReadCloser, error) {
 	u, err := url.Parse(uriStr)
 	if err != nil {
 		return nil, err
 	}
 	switch strings.ToLower(u.Scheme) {
 	case "http", "https":
-		f, err := http.Get(uriStr)
+		f, err := client.Get(uriStr)
 		if err != nil {
 			return nil, err
 		}

modules/uri/uri_test.go

@@ -4,10 +4,18 @@
 package uri
 
 import (
+	"context"
+	"errors"
+	"net"
+	"net/http"
+	"net/http/httptest"
 	"path/filepath"
+	"strings"
+	"sync/atomic"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestReadURI(t *testing.T) {
@@ -17,3 +25,45 @@ func TestReadURI(t *testing.T) {
 	assert.NoError(t, err)
 	defer f.Close()
 }
+
+// TestOpenWithClientValidatesRedirectTarget verifies OpenWithClient routes the
+// whole request chain (including redirects) through the provided client, so a
+// client whose transport refuses to dial an internal target blocks a redirect to
+// it — whereas the default client (old Open behavior) follows it.
+func TestOpenWithClientValidatesRedirectTarget(t *testing.T) {
+	var internalHit atomic.Bool
+	internal := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		internalHit.Store(true)
+		_, _ = w.Write([]byte("secret"))
+	}))
+	defer internal.Close()
+
+	front := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, internal.URL, http.StatusFound)
+	}))
+	defer front.Close()
+
+	internalAddr := strings.TrimPrefix(internal.URL, "http://")
+
+	// a client that refuses to dial the internal target, mimicking the migration
+	// hostmatcher dialer that re-validates every hop
+	blockingClient := &http.Client{Transport: &http.Transport{
+		DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
+			if addr == internalAddr {
+				return nil, errors.New("blocked internal address")
+			}
+			return (&net.Dialer{}).DialContext(ctx, network, addr)
+		},
+	}}
+
+	_, err := OpenWithClient(front.URL, blockingClient)
+	require.Error(t, err)
+	assert.False(t, internalHit.Load(), "the redirect target must not be reached through the validating client")
+
+	// the default client (the previous behavior) follows the redirect to the internal target
+	internalHit.Store(false)
+	rc, err := Open(front.URL)
+	require.NoError(t, err)
+	_ = rc.Close()
+	assert.True(t, internalHit.Load(), "sanity check: the default client follows the redirect")
+}