Add gitea webhook support

gitea/gitea.go

@@ -0,0 +1,179 @@
+package gitea
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+)
+
+// parse errors
+var (
+	ErrEventNotSpecifiedToParse    = errors.New("no Event specified to parse")
+	ErrInvalidHTTPMethod           = errors.New("invalid HTTP Method")
+	ErrMissingGiteaEventHeader     = errors.New("missing X-Gitea-Event Header")
+	ErrMissingGiteaSignatureHeader = errors.New("missing X-Gitea-Signature Header")
+	ErrEventNotFound               = errors.New("event not defined to be parsed")
+	ErrParsingPayload              = errors.New("error parsing payload")
+	ErrHMACVerificationFailed      = errors.New("HMAC verification failed")
+)
+
+// Gitea hook types
+// https://github.com/go-gitea/gitea/blob/bf7b083cfe47cc922090ce7922b89f7a5030a44d/models/webhook/hooktask.go#L31
+const (
+	CreateEvent               Event = "create"
+	DeleteEvent               Event = "delete"
+	ForkEvent                 Event = "fork"
+	IssuesEvent               Event = "issues"
+	IssueAssignEvent          Event = "issue_assign"
+	IssueLabelEvent           Event = "issue_label"
+	IssueMilestoneEvent       Event = "issue_milestone"
+	IssueCommentEvent         Event = "issue_comment"
+	PushEvent                 Event = "push"
+	PullRequestEvent          Event = "pull_request"
+	PullRequestAssignEvent    Event = "pull_request_assign"
+	PullRequestLabelEvent     Event = "pull_request_label"
+	PullRequestMilestoneEvent Event = "pull_request_milestone"
+	PullRequestCommentEvent   Event = "pull_request_comment"
+	PullRequestReviewEvent    Event = "pull_request_review"
+	PullRequestSyncEvent      Event = "pull_request_sync"
+	RepositoryEvent           Event = "repository"
+	ReleaseEvent              Event = "release"
+)
+
+// Option is a configuration option for the webhook
+type Option func(*Webhook) error
+
+// Options is a namespace var for configuration options
+var Options = WebhookOptions{}
+
+// WebhookOptions is a namespace for configuration option methods
+type WebhookOptions struct{}
+
+// Secret registers the GitLab secret
+func (WebhookOptions) Secret(secret string) Option {
+	return func(hook *Webhook) error {
+		hook.secret = secret
+		return nil
+	}
+}
+
+// Webhook instance contains all methods needed to process events
+type Webhook struct {
+	secret string
+}
+
+// Event defines a GitLab hook event type by the X-Gitlab-Event Header
+type Event string
+
+// New creates and returns a WebHook instance denoted by the Provider type
+func New(options ...Option) (*Webhook, error) {
+	hook := new(Webhook)
+	for _, opt := range options {
+		if err := opt(hook); err != nil {
+			return nil, errors.New("Error applying Option")
+		}
+	}
+	return hook, nil
+}
+
+// Parse verifies and parses the events specified and returns the payload object or an error
+func (hook Webhook) Parse(r *http.Request, events ...Event) (interface{}, error) {
+	defer func() {
+		_, _ = io.Copy(ioutil.Discard, r.Body)
+		_ = r.Body.Close()
+	}()
+
+	if len(events) == 0 {
+		return nil, ErrEventNotSpecifiedToParse
+	}
+	if r.Method != http.MethodPost {
+		return nil, ErrInvalidHTTPMethod
+	}
+
+	event := r.Header.Get("X-Gitea-Event")
+	if len(event) == 0 {
+		return nil, ErrMissingGiteaEventHeader
+	}
+
+	giteaEvent := Event(event)
+
+	var found bool
+	for _, evt := range events {
+		if evt == giteaEvent {
+			found = true
+			break
+		}
+	}
+	// event not defined to be parsed
+	if !found {
+		return nil, ErrEventNotFound
+	}
+
+	payload, err := ioutil.ReadAll(r.Body)
+	if err != nil || len(payload) == 0 {
+		return nil, ErrParsingPayload
+	}
+
+	// If we have a Secret set, we should check the MAC
+	if len(hook.secret) > 0 {
+		signature := r.Header.Get("X-Gitea-Signature")
+		if len(signature) == 0 {
+			return nil, ErrMissingGiteaSignatureHeader
+		}
+		sig256 := hmac.New(sha256.New, []byte(hook.secret))
+		_, _ = io.Writer(sig256).Write([]byte(payload))
+		expectedMAC := hex.EncodeToString(sig256.Sum(nil))
+
+		if !hmac.Equal([]byte(signature), []byte(expectedMAC)) {
+			return nil, ErrHMACVerificationFailed
+		}
+	}
+
+	// https://github.com/go-gitea/gitea/blob/33fca2b537d36cf998dd27425b2bb8ed5b0965f3/services/webhook/payloader.go#L27
+	switch giteaEvent {
+	case CreateEvent:
+		var pl CreatePayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case DeleteEvent:
+		var pl DeletePayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case ForkEvent:
+		var pl ForkPayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case PushEvent:
+		var pl PushPayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case IssuesEvent, IssueAssignEvent, IssueLabelEvent, IssueMilestoneEvent:
+		var pl IssuePayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case IssueCommentEvent, PullRequestCommentEvent:
+		var pl IssueCommentPayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case PullRequestEvent, PullRequestAssignEvent, PullRequestLabelEvent, PullRequestMilestoneEvent, PullRequestReviewEvent, PullRequestSyncEvent:
+		var pl PullRequestPayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case RepositoryEvent:
+		var pl RepositoryPayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	case ReleaseEvent:
+		var pl ReleasePayload
+		err = json.Unmarshal([]byte(payload), &pl)
+		return pl, err
+	default:
+		return nil, fmt.Errorf("unknown event %s", giteaEvent)
+	}
+}