1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
// Copyright 2016 The go-github AUTHORS. All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file provides functions for validating payloads from GitHub Webhooks.
// GitHub docs: https://developer.github.com/webhooks/securing/#validating-payloads-from-github
package github
import (
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"crypto/sha512"
"encoding/hex"
"encoding/json"
"errors"
"fmt"
"hash"
"io/ioutil"
"net/http"
"strings"
)
const (
// sha1Prefix is the prefix used by GitHub before the HMAC hexdigest.
sha1Prefix = "sha1"
// sha256Prefix and sha512Prefix are provided for future compatibility.
sha256Prefix = "sha256"
sha512Prefix = "sha512"
// signatureHeader is the GitHub header key used to pass the HMAC hexdigest.
signatureHeader = "X-Hub-Signature"
// eventTypeHeader is the Github header key used to pass the event type.
eventTypeHeader = "X-Github-Event"
)
var (
// eventTypeMapping maps webhooks types to their corresponding go-github struct types.
eventTypeMapping = map[string]string{
"commit_comment": "CommitCommentEvent",
"create": "CreateEvent",
"delete": "DeleteEvent",
"deployment": "DeploymentEvent",
"deployment_status": "DeploymentStatusEvent",
"fork": "ForkEvent",
"gollum": "GollumEvent",
"integration_installation": "IntegrationInstallationEvent",
"integration_installation_repositories": "IntegrationInstallationRepositoriesEvent",
"issue_comment": "IssueCommentEvent",
"issues": "IssuesEvent",
"member": "MemberEvent",
"membership": "MembershipEvent",
"page_build": "PageBuildEvent",
"public": "PublicEvent",
"pull_request_review_comment": "PullRequestReviewCommentEvent",
"pull_request": "PullRequestEvent",
"push": "PushEvent",
"repository": "RepositoryEvent",
"release": "ReleaseEvent",
"status": "StatusEvent",
"team_add": "TeamAddEvent",
"watch": "WatchEvent",
}
)
// genMAC generates the HMAC signature for a message provided the secret key
// and hashFunc.
func genMAC(message, key []byte, hashFunc func() hash.Hash) []byte {
mac := hmac.New(hashFunc, key)
mac.Write(message)
return mac.Sum(nil)
}
// checkMAC reports whether messageMAC is a valid HMAC tag for message.
func checkMAC(message, messageMAC, key []byte, hashFunc func() hash.Hash) bool {
expectedMAC := genMAC(message, key, hashFunc)
return hmac.Equal(messageMAC, expectedMAC)
}
// messageMAC returns the hex-decoded HMAC tag from the signature and its
// corresponding hash function.
func messageMAC(signature string) ([]byte, func() hash.Hash, error) {
if signature == "" {
return nil, nil, errors.New("missing signature")
}
sigParts := strings.SplitN(signature, "=", 2)
if len(sigParts) != 2 {
return nil, nil, fmt.Errorf("error parsing signature %q", signature)
}
var hashFunc func() hash.Hash
switch sigParts[0] {
case sha1Prefix:
hashFunc = sha1.New
case sha256Prefix:
hashFunc = sha256.New
case sha512Prefix:
hashFunc = sha512.New
default:
return nil, nil, fmt.Errorf("unknown hash type prefix: %q", sigParts[0])
}
buf, err := hex.DecodeString(sigParts[1])
if err != nil {
return nil, nil, fmt.Errorf("error decoding signature %q: %v", signature, err)
}
return buf, hashFunc, nil
}
// ValidatePayload validates an incoming GitHub Webhook event request
// and returns the (JSON) payload.
// secretKey is the GitHub Webhook secret message.
//
// Example usage:
//
// func (s *GitHubEventMonitor) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// payload, err := github.ValidatePayload(r, s.webhookSecretKey)
// if err != nil { ... }
// // Process payload...
// }
//
func ValidatePayload(r *http.Request, secretKey []byte) (payload []byte, err error) {
payload, err = ioutil.ReadAll(r.Body)
if err != nil {
return nil, err
}
sig := r.Header.Get(signatureHeader)
if err := validateSignature(sig, payload, secretKey); err != nil {
return nil, err
}
return payload, nil
}
// validateSignature validates the signature for the given payload.
// signature is the GitHub hash signature delivered in the X-Hub-Signature header.
// payload is the JSON payload sent by GitHub Webhooks.
// secretKey is the GitHub Webhook secret message.
//
// GitHub docs: https://developer.github.com/webhooks/securing/#validating-payloads-from-github
func validateSignature(signature string, payload, secretKey []byte) error {
messageMAC, hashFunc, err := messageMAC(signature)
if err != nil {
return err
}
if !checkMAC(payload, messageMAC, secretKey, hashFunc) {
return errors.New("payload signature check failed")
}
return nil
}
// WebHookType returns the event type of webhook request r.
func WebHookType(r *http.Request) string {
return r.Header.Get(eventTypeHeader)
}
// ParseWebHook parses the event payload. For recognized event types, a
// value of the corresponding struct type will be returned (as returned
// by Event.Payload()). An error will be returned for unrecognized event
// types.
//
// Example usage:
//
// func (s *GitHubEventMonitor) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// payload, err := github.ValidatePayload(r, s.webhookSecretKey)
// if err != nil { ... }
// event, err := github.ParseWebHook(github.WebHookType(r), payload)
// if err != nil { ... }
// switch event := event.(type) {
// case CommitCommentEvent:
// processCommitCommentEvent(event)
// case CreateEvent:
// processCreateEvent(event)
// ...
// }
// }
//
func ParseWebHook(messageType string, payload []byte) (interface{}, error) {
eventType, ok := eventTypeMapping[messageType]
if !ok {
return nil, fmt.Errorf("unknown X-Github-Event in message: %v", messageType)
}
event := Event{
Type: &eventType,
RawPayload: (*json.RawMessage)(&payload),
}
return event.Payload(), nil
}
|
