98 lines
2.8 KiB
Go
98 lines
2.8 KiB
Go
// Copyright 2022 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package activitypub
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import (
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"crypto"
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"crypto/x509"
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"encoding/pem"
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"fmt"
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"io"
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"net/http"
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"net/url"
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"code.gitea.io/gitea/modules/activitypub"
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"code.gitea.io/gitea/modules/httplib"
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"code.gitea.io/gitea/modules/setting"
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gitea_context "code.gitea.io/gitea/services/context"
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ap "github.com/go-ap/activitypub"
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"github.com/go-fed/httpsig"
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)
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func getPublicKeyFromResponse(b []byte, keyID *url.URL) (p crypto.PublicKey, err error) {
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person := ap.PersonNew(ap.IRI(keyID.String()))
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err = person.UnmarshalJSON(b)
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if err != nil {
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return nil, fmt.Errorf("ActivityStreams type cannot be converted to one known to have publicKey property: %w", err)
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}
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pubKey := person.PublicKey
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if pubKey.ID.String() != keyID.String() {
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return nil, fmt.Errorf("cannot find publicKey with id: %s in %s", keyID, string(b))
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}
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pubKeyPem := pubKey.PublicKeyPem
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block, _ := pem.Decode([]byte(pubKeyPem))
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if block == nil || block.Type != "PUBLIC KEY" {
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return nil, fmt.Errorf("could not decode publicKeyPem to PUBLIC KEY pem block type")
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}
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p, err = x509.ParsePKIXPublicKey(block.Bytes)
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return p, err
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}
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func fetch(iri *url.URL) (b []byte, err error) {
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req := httplib.NewRequest(iri.String(), http.MethodGet)
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req.Header("Accept", activitypub.ActivityStreamsContentType)
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req.Header("User-Agent", "Gitea/"+setting.AppVer)
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resp, err := req.Response()
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if err != nil {
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return nil, err
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return nil, fmt.Errorf("url IRI fetch [%s] failed with status (%d): %s", iri, resp.StatusCode, resp.Status)
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}
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b, err = io.ReadAll(io.LimitReader(resp.Body, setting.Federation.MaxSize))
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return b, err
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}
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func verifyHTTPSignatures(ctx *gitea_context.APIContext) (authenticated bool, err error) {
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r := ctx.Req
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// 1. Figure out what key we need to verify
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v, err := httpsig.NewVerifier(r)
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if err != nil {
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return false, err
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}
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ID := v.KeyId()
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idIRI, err := url.Parse(ID)
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if err != nil {
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return false, err
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}
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// 2. Fetch the public key of the other actor
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b, err := fetch(idIRI)
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if err != nil {
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return false, err
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}
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pubKey, err := getPublicKeyFromResponse(b, idIRI)
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if err != nil {
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return false, err
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}
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// 3. Verify the other actor's key
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algo := httpsig.Algorithm(setting.Federation.Algorithms[0])
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authenticated = v.Verify(pubKey, algo) == nil
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return authenticated, err
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}
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// ReqHTTPSignature function
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func ReqHTTPSignature() func(ctx *gitea_context.APIContext) {
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return func(ctx *gitea_context.APIContext) {
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if authenticated, err := verifyHTTPSignatures(ctx); err != nil {
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ctx.ServerError("verifyHttpSignatures", err)
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} else if !authenticated {
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ctx.Error(http.StatusForbidden, "reqSignature", "request signature verification failed")
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}
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}
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}
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