gitea/routers/api/v1/activitypub/reqsignature.go

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// Copyright 2022 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.
package activitypub
import (
"context"
"crypto"
"crypto/x509"
"encoding/pem"
"fmt"
"io"
"net/http"
"net/url"
"time"
"code.gitea.io/gitea/modules/activitypub"
gitea_context "code.gitea.io/gitea/modules/context"
"code.gitea.io/gitea/modules/json"
"code.gitea.io/gitea/modules/setting"
"github.com/go-fed/activity/pub"
"github.com/go-fed/activity/streams"
"github.com/go-fed/activity/streams/vocab"
"github.com/go-fed/httpsig"
)
type publicKeyer interface {
GetW3IDSecurityV1PublicKey() vocab.W3IDSecurityV1PublicKeyProperty
}
func getPublicKeyFromResponse(ctx context.Context, b []byte, keyID *url.URL) (p crypto.PublicKey, err error) {
m := make(map[string]interface{})
err = json.Unmarshal(b, &m)
if err != nil {
return
}
var t vocab.Type
t, err = streams.ToType(ctx, m)
if err != nil {
return
}
pker, ok := t.(publicKeyer)
if !ok {
err = fmt.Errorf("ActivityStreams type cannot be converted to one known to have publicKey property: %T", t)
return
}
pkp := pker.GetW3IDSecurityV1PublicKey()
if pkp == nil {
err = fmt.Errorf("publicKey property is not provided")
return
}
var pkpFound vocab.W3IDSecurityV1PublicKey
for pkpIter := pkp.Begin(); pkpIter != pkp.End(); pkpIter = pkpIter.Next() {
if !pkpIter.IsW3IDSecurityV1PublicKey() {
continue
}
pkValue := pkpIter.Get()
var pkID *url.URL
pkID, err = pub.GetId(pkValue)
if err != nil {
return
}
if pkID.String() != keyID.String() {
continue
}
pkpFound = pkValue
break
}
if pkpFound == nil {
err = fmt.Errorf("cannot find publicKey with id: %s in %s", keyID, b)
return
}
pkPemProp := pkpFound.GetW3IDSecurityV1PublicKeyPem()
if pkPemProp == nil || !pkPemProp.IsXMLSchemaString() {
err = fmt.Errorf("publicKeyPem property is not provided or it is not embedded as a value")
return
}
pubKeyPem := pkPemProp.Get()
var block *pem.Block
block, _ = pem.Decode([]byte(pubKeyPem))
if block == nil || block.Type != "PUBLIC KEY" {
err = fmt.Errorf("could not decode publicKeyPem to PUBLIC KEY pem block type")
return
}
p, err = x509.ParsePKIXPublicKey(block.Bytes)
return
}
func fetch(iri *url.URL) (b []byte, err error) {
var req *http.Request
req, err = http.NewRequest(http.MethodGet, iri.String(), nil)
if err != nil {
return
}
req.Header.Add("Accept", activitypub.ActivityStreamsContentType)
req.Header.Add("Accept-Charset", "utf-8")
clock, err := activitypub.NewClock()
if err != nil {
return
}
req.Header.Add("Date", fmt.Sprintf("%s GMT", clock.Now().UTC().Format(time.RFC1123)))
var resp *http.Response
client := &http.Client{}
resp, err = client.Do(req)
if err != nil {
return
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
err = fmt.Errorf("url IRI fetch [%s] failed with status (%d): %s", iri, resp.StatusCode, resp.Status)
return
}
b, err = io.ReadAll(resp.Body)
return
}
func verifyHTTPSignatures(ctx *gitea_context.APIContext) (authenticated bool, err error) {
r := ctx.Req
// 1. Figure out what key we need to verify
var v httpsig.Verifier
v, err = httpsig.NewVerifier(r)
if err != nil {
return
}
ID := v.KeyId()
var idIRI *url.URL
idIRI, err = url.Parse(ID)
if err != nil {
return
}
// 2. Fetch the public key of the other actor
var b []byte
b, err = fetch(idIRI)
if err != nil {
return
}
pKey, err := getPublicKeyFromResponse(*ctx, b, idIRI)
if err != nil {
return
}
// 3. Verify the other actor's key
algo := httpsig.Algorithm(setting.Federation.Algorithms[0])
authenticated = nil == v.Verify(pKey, algo)
return
}
// ReqSignature function
func ReqSignature() func(ctx *gitea_context.APIContext) {
return func(ctx *gitea_context.APIContext) {
if authenticated, err := verifyHTTPSignatures(ctx); err != nil {
ctx.Error(http.StatusInternalServerError, "verifyHttpSignatures", err)
} else if !authenticated {
ctx.Error(http.StatusForbidden, "reqSignature", "request signature verification failed")
}
}
}