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

105 lines
2.8 KiB
Go

// 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/httplib"
"code.gitea.io/gitea/modules/setting"
ap "github.com/go-ap/activitypub"
"github.com/go-fed/httpsig"
)
func getPublicKeyFromResponse(ctx context.Context, b []byte, keyID *url.URL) (p crypto.PublicKey, err error) {
person := ap.PersonNew(ap.IRI(keyID.String()))
err = person.UnmarshalJSON(b)
if err != nil {
err = fmt.Errorf("ActivityStreams type cannot be converted to one known to have publicKey property: %T", b)
return
}
pkey := person.PublicKey
if pkey.ID.String() != keyID.String() {
err = fmt.Errorf("cannot find publicKey with id: %s in %s", keyID, b)
return
}
pubKeyPem := pkey.PublicKeyPem
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) {
req := httplib.NewRequest(iri.String(), http.MethodGet)
req.Header("Accept", activitypub.ActivityStreamsContentType)
req.Header("Accept-Charset", "utf-8")
req.Header("Date", fmt.Sprintf("%s GMT", time.Now().UTC().Format(time.RFC1123)))
resp, err := req.Response()
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
v, err := httpsig.NewVerifier(r)
if err != nil {
return
}
ID := v.KeyId()
idIRI, err := url.Parse(ID)
if err != nil {
return
}
// 2. Fetch the public key of the other actor
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")
}
}
}