mirror of
https://github.com/strongdm/comply
synced 2024-11-13 19:34:54 +00:00
246 lines
8.3 KiB
Go
246 lines
8.3 KiB
Go
// Copyright 2016 The go-github AUTHORS. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// This file provides functions for validating payloads from GitHub Webhooks.
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// GitHub API docs: https://developer.github.com/webhooks/securing/#validating-payloads-from-github
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package github
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import (
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"crypto/hmac"
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"crypto/sha1"
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"crypto/sha256"
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"crypto/sha512"
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"encoding/hex"
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"encoding/json"
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"errors"
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"fmt"
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"hash"
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"io/ioutil"
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"net/http"
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"net/url"
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"strings"
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)
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const (
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// sha1Prefix is the prefix used by GitHub before the HMAC hexdigest.
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sha1Prefix = "sha1"
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// sha256Prefix and sha512Prefix are provided for future compatibility.
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sha256Prefix = "sha256"
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sha512Prefix = "sha512"
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// signatureHeader is the GitHub header key used to pass the HMAC hexdigest.
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signatureHeader = "X-Hub-Signature"
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// eventTypeHeader is the GitHub header key used to pass the event type.
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eventTypeHeader = "X-Github-Event"
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// deliveryIDHeader is the GitHub header key used to pass the unique ID for the webhook event.
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deliveryIDHeader = "X-Github-Delivery"
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)
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var (
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// eventTypeMapping maps webhooks types to their corresponding go-github struct types.
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eventTypeMapping = map[string]string{
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"commit_comment": "CommitCommentEvent",
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"create": "CreateEvent",
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"delete": "DeleteEvent",
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"deployment": "DeploymentEvent",
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"deployment_status": "DeploymentStatusEvent",
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"fork": "ForkEvent",
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"gollum": "GollumEvent",
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"installation": "InstallationEvent",
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"installation_repositories": "InstallationRepositoriesEvent",
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"issue_comment": "IssueCommentEvent",
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"issues": "IssuesEvent",
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"label": "LabelEvent",
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"marketplace_purchase": "MarketplacePurchaseEvent",
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"member": "MemberEvent",
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"membership": "MembershipEvent",
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"milestone": "MilestoneEvent",
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"organization": "OrganizationEvent",
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"org_block": "OrgBlockEvent",
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"page_build": "PageBuildEvent",
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"ping": "PingEvent",
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"project": "ProjectEvent",
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"project_card": "ProjectCardEvent",
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"project_column": "ProjectColumnEvent",
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"public": "PublicEvent",
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"pull_request_review": "PullRequestReviewEvent",
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"pull_request_review_comment": "PullRequestReviewCommentEvent",
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"pull_request": "PullRequestEvent",
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"push": "PushEvent",
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"repository": "RepositoryEvent",
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"release": "ReleaseEvent",
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"status": "StatusEvent",
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"team": "TeamEvent",
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"team_add": "TeamAddEvent",
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"watch": "WatchEvent",
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}
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)
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// genMAC generates the HMAC signature for a message provided the secret key
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// and hashFunc.
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func genMAC(message, key []byte, hashFunc func() hash.Hash) []byte {
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mac := hmac.New(hashFunc, key)
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mac.Write(message)
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return mac.Sum(nil)
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}
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// checkMAC reports whether messageMAC is a valid HMAC tag for message.
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func checkMAC(message, messageMAC, key []byte, hashFunc func() hash.Hash) bool {
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expectedMAC := genMAC(message, key, hashFunc)
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return hmac.Equal(messageMAC, expectedMAC)
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}
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// messageMAC returns the hex-decoded HMAC tag from the signature and its
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// corresponding hash function.
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func messageMAC(signature string) ([]byte, func() hash.Hash, error) {
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if signature == "" {
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return nil, nil, errors.New("missing signature")
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}
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sigParts := strings.SplitN(signature, "=", 2)
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if len(sigParts) != 2 {
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return nil, nil, fmt.Errorf("error parsing signature %q", signature)
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}
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var hashFunc func() hash.Hash
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switch sigParts[0] {
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case sha1Prefix:
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hashFunc = sha1.New
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case sha256Prefix:
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hashFunc = sha256.New
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case sha512Prefix:
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hashFunc = sha512.New
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default:
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return nil, nil, fmt.Errorf("unknown hash type prefix: %q", sigParts[0])
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}
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buf, err := hex.DecodeString(sigParts[1])
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if err != nil {
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return nil, nil, fmt.Errorf("error decoding signature %q: %v", signature, err)
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}
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return buf, hashFunc, nil
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}
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// ValidatePayload validates an incoming GitHub Webhook event request
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// and returns the (JSON) payload.
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// The Content-Type header of the payload can be "application/json" or "application/x-www-form-urlencoded".
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// If the Content-Type is neither then an error is returned.
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// secretKey is the GitHub Webhook secret message.
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//
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// Example usage:
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//
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// func (s *GitHubEventMonitor) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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// payload, err := github.ValidatePayload(r, s.webhookSecretKey)
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// if err != nil { ... }
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// // Process payload...
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// }
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//
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func ValidatePayload(r *http.Request, secretKey []byte) (payload []byte, err error) {
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var body []byte // Raw body that GitHub uses to calculate the signature.
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switch ct := r.Header.Get("Content-Type"); ct {
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case "application/json":
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var err error
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if body, err = ioutil.ReadAll(r.Body); err != nil {
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return nil, err
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}
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// If the content type is application/json,
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// the JSON payload is just the original body.
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payload = body
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case "application/x-www-form-urlencoded":
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// payloadFormParam is the name of the form parameter that the JSON payload
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// will be in if a webhook has its content type set to application/x-www-form-urlencoded.
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const payloadFormParam = "payload"
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var err error
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if body, err = ioutil.ReadAll(r.Body); err != nil {
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return nil, err
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}
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// If the content type is application/x-www-form-urlencoded,
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// the JSON payload will be under the "payload" form param.
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form, err := url.ParseQuery(string(body))
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if err != nil {
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return nil, err
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}
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payload = []byte(form.Get(payloadFormParam))
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default:
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return nil, fmt.Errorf("Webhook request has unsupported Content-Type %q", ct)
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}
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sig := r.Header.Get(signatureHeader)
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if err := validateSignature(sig, body, secretKey); err != nil {
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return nil, err
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}
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return payload, nil
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}
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// validateSignature validates the signature for the given payload.
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// signature is the GitHub hash signature delivered in the X-Hub-Signature header.
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// payload is the JSON payload sent by GitHub Webhooks.
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// secretKey is the GitHub Webhook secret message.
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//
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// GitHub API docs: https://developer.github.com/webhooks/securing/#validating-payloads-from-github
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func validateSignature(signature string, payload, secretKey []byte) error {
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messageMAC, hashFunc, err := messageMAC(signature)
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if err != nil {
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return err
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}
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if !checkMAC(payload, messageMAC, secretKey, hashFunc) {
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return errors.New("payload signature check failed")
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}
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return nil
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}
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// WebHookType returns the event type of webhook request r.
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//
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// GitHub API docs: https://developer.github.com/v3/repos/hooks/#webhook-headers
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func WebHookType(r *http.Request) string {
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return r.Header.Get(eventTypeHeader)
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}
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// DeliveryID returns the unique delivery ID of webhook request r.
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//
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// GitHub API docs: https://developer.github.com/v3/repos/hooks/#webhook-headers
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func DeliveryID(r *http.Request) string {
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return r.Header.Get(deliveryIDHeader)
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}
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// ParseWebHook parses the event payload. For recognized event types, a
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// value of the corresponding struct type will be returned (as returned
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// by Event.ParsePayload()). An error will be returned for unrecognized event
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// types.
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//
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// Example usage:
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//
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// func (s *GitHubEventMonitor) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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// payload, err := github.ValidatePayload(r, s.webhookSecretKey)
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// if err != nil { ... }
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// event, err := github.ParseWebHook(github.WebHookType(r), payload)
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// if err != nil { ... }
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// switch event := event.(type) {
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// case *github.CommitCommentEvent:
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// processCommitCommentEvent(event)
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// case *github.CreateEvent:
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// processCreateEvent(event)
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// ...
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// }
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// }
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//
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func ParseWebHook(messageType string, payload []byte) (interface{}, error) {
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eventType, ok := eventTypeMapping[messageType]
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if !ok {
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return nil, fmt.Errorf("unknown X-Github-Event in message: %v", messageType)
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}
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event := Event{
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Type: &eventType,
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RawPayload: (*json.RawMessage)(&payload),
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}
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return event.ParsePayload()
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}
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