/
hooks.go
105 lines (87 loc) · 2.6 KB
/
hooks.go
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package ghapi
import (
"crypto/hmac"
"crypto/sha1"
"encoding/hex"
"hash"
"io/ioutil"
"net/http"
)
// ReadRequest takes an expected GitHub webhook secret and an *http.Request. If signature validation succeeds the
// GitHubEventType and request body as a byte slice are returned.
func ReadRequest(secret []byte, r *http.Request) (GitHubEventType, []byte, error) {
var body []byte
var err error
var eventType GitHubEventType
if r.Body == nil {
return "", nil, ErrHTTPRequestBodyNil
}
if body, err = ioutil.ReadAll(r.Body); err != nil {
return "", nil, err
}
if err = ValidateEvent(secret, body, r.Header); err != nil {
return "", nil, err
}
if eventType, err = GetEventType(r.Header); err != nil {
return "", nil, err
}
return eventType, body, nil
}
// ValidateEvent takes an expected GitHub webhook secret, a body, and an http.Header. If signature validation succeeds
// nil is returned.
//
// This function may be used when it's necessary to inspect the body of an event before validating its signature; for
// example, if the webhook stores separate secrets per organization but has a single endpoint to receive GitHub events
// it can extract the organization to retrieve the appropriate secret.
func ValidateEvent(secret []byte, body []byte, header http.Header) error {
var err error
if body == nil {
return ErrHTTPRequestBodyNil
}
var messageMAC []byte
if messageMAC, err = getMAC(header); err != nil {
return err
}
sha1hmac := hmac.New(sha1.New, secret)
if ok := checkMAC(sha1hmac, body, messageMAC); !ok {
return ErrSignatureMismatch
}
return nil
}
// GetEventType returns the GitHubEventType based on the "X-Github-Event" header value from a received webhook request.
func GetEventType(header http.Header) (GitHubEventType, error) {
events := header["X-Github-Event"]
if events == nil || len(events) != 1 {
return "", ErrGitHubEventNotFound
}
return GitHubEventType(events[0]), nil
}
func getSignature(header http.Header) (string, error) {
sigs := header["X-Hub-Signature"]
if sigs == nil || len(sigs) != 1 {
return "", ErrSignatureNotFound
}
sig := sigs[0]
if sig[:5] != "sha1=" {
return "", ErrSignatureMarkerNotFound
}
return sig[5:], nil
}
func getMAC(header http.Header) ([]byte, error) {
sig, err := getSignature(header)
if err != nil {
return nil, err
}
messageMAC, err := hex.DecodeString(sig)
if err != nil {
return nil, err
}
return messageMAC, nil
}
func checkMAC(mac hash.Hash, message, messageMAC []byte) bool {
if _, err := mac.Write(message); err != nil {
return false
}
expectedMAC := mac.Sum(nil)
return hmac.Equal(messageMAC, expectedMAC)
}