1 files changed, 124 insertions, 0 deletions
diff --git a/modules/activitypub/client.go b/modules/activitypub/client.go
new file mode 100644
index 0000000000..738b1e4737
--- /dev/null
+++ b/modules/activitypub/client.go
@@ -0,0 +1,124 @@
+// 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 (
+	"bytes"
+	"crypto/rsa"
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/proxy"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/go-fed/httpsig"
+)
+
+const (
+	// ActivityStreamsContentType const
+	ActivityStreamsContentType = `application/ld+json; profile="https://www.w3.org/ns/activitystreams"`
+	httpsigExpirationTime      = 60
+)
+
+// Gets the current time as an RFC 2616 formatted string
+// RFC 2616 requires RFC 1123 dates but with GMT instead of UTC
+func CurrentTime() string {
+	return strings.ReplaceAll(time.Now().UTC().Format(time.RFC1123), "UTC", "GMT")
+}
+
+func containsRequiredHTTPHeaders(method string, headers []string) error {
+	var hasRequestTarget, hasDate, hasDigest bool
+	for _, header := range headers {
+		hasRequestTarget = hasRequestTarget || header == httpsig.RequestTarget
+		hasDate = hasDate || header == "Date"
+		hasDigest = hasDigest || header == "Digest"
+	}
+	if !hasRequestTarget {
+		return fmt.Errorf("missing http header for %s: %s", method, httpsig.RequestTarget)
+	} else if !hasDate {
+		return fmt.Errorf("missing http header for %s: Date", method)
+	} else if !hasDigest && method != http.MethodGet {
+		return fmt.Errorf("missing http header for %s: Digest", method)
+	}
+	return nil
+}
+
+// Client struct
+type Client struct {
+	client      *http.Client
+	algs        []httpsig.Algorithm
+	digestAlg   httpsig.DigestAlgorithm
+	getHeaders  []string
+	postHeaders []string
+	priv        *rsa.PrivateKey
+	pubID       string
+}
+
+// NewClient function
+func NewClient(user *user_model.User, pubID string) (c *Client, err error) {
+	if err = containsRequiredHTTPHeaders(http.MethodGet, setting.Federation.GetHeaders); err != nil {
+		return
+	} else if err = containsRequiredHTTPHeaders(http.MethodPost, setting.Federation.PostHeaders); err != nil {
+		return
+	}
+
+	priv, err := GetPrivateKey(user)
+	if err != nil {
+		return
+	}
+	privPem, _ := pem.Decode([]byte(priv))
+	privParsed, err := x509.ParsePKCS1PrivateKey(privPem.Bytes)
+	if err != nil {
+		return
+	}
+
+	c = &Client{
+		client: &http.Client{
+			Transport: &http.Transport{
+				Proxy: proxy.Proxy(),
+			},
+		},
+		algs:        setting.HttpsigAlgs,
+		digestAlg:   httpsig.DigestAlgorithm(setting.Federation.DigestAlgorithm),
+		getHeaders:  setting.Federation.GetHeaders,
+		postHeaders: setting.Federation.PostHeaders,
+		priv:        privParsed,
+		pubID:       pubID,
+	}
+	return
+}
+
+// NewRequest function
+func (c *Client) NewRequest(b []byte, to string) (req *http.Request, err error) {
+	buf := bytes.NewBuffer(b)
+	req, err = http.NewRequest(http.MethodPost, to, buf)
+	if err != nil {
+		return
+	}
+	req.Header.Add("Content-Type", ActivityStreamsContentType)
+	req.Header.Add("Date", CurrentTime())
+	req.Header.Add("User-Agent", "Gitea/"+setting.AppVer)
+	signer, _, err := httpsig.NewSigner(c.algs, c.digestAlg, c.postHeaders, httpsig.Signature, httpsigExpirationTime)
+	if err != nil {
+		return
+	}
+	err = signer.SignRequest(c.priv, c.pubID, req, b)
+	return
+}
+
+// Post function
+func (c *Client) Post(b []byte, to string) (resp *http.Response, err error) {
+	var req *http.Request
+	if req, err = c.NewRequest(b, to); err != nil {
+		return
+	}
+	resp, err = c.client.Do(req)
+	return
+}