8000 Breaks up public API (#6) by rjz · Pull Request #7 · rjz/githubhook · GitHub
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Merged
merged 1 commit into from
Aug 5, 2016
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Breaks up public API (#6) #7

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Breaks up public API (#6) 
Separating `Parse` into separate `New` and `SignedBy` methods will allow
consumers to provisionally extract hook content from an HTTP request
(via `New`) before verifyingt that the hook signature meets
expectations.
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@rjz
rjz committed Aug 5, 2016
commit 424280528717a50ef3a8866f9d7b62aaf885291f
43 changes: 21 additions & 22 deletions githubhook.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,37 +10,38 @@ import (
"strings"
)

// Hook describes an inbound github webhook
type Hook struct {
Signature string
Event string
Id string
Payload []byte
}

const signaturePrefix = "sha1="
const signatureLength = 45 // len(SignaturePrefix) + len(hex(sha1))

func signBody(secret, body []byte) []byte {
computed := hmac.New(sha1.New, secret)
computed.Write(body)
return []byte(computed.Sum(nil))
}

func verifySignature(secret []byte, signature string, body []byte) bool {

const signaturePrefix = "sha1="
const signatureLength = 45 // len(SignaturePrefix) + len(hex(sha1))

if len(signature) != signatureLength || !strings.HasPrefix(signature, signaturePrefix) {
// SignedBy checks that the provided secret matches the hook Signature
func (h *Hook) SignedBy(secret []byte) bool {
if len(h.Signature) != signatureLength || !strings.HasPrefix(h.Signature, signaturePrefix) {
return false
}

actual := make([]byte, 20)
hex.Decode(actual, []byte(signature[5:]))
hex.Decode(actual, []byte(h.Signature[5:]))

return hmac.Equal(signBody(secret, body), actual)
return hmac.Equal(signBody(secret, h.Payload), actual)
}

func Parse(secret []byte, req *http.Request) (*Hook, error) {
hook := Hook{}

// New extracts a Hook from an incoming http.Request
func New(req *http.Request) (hook *Hook, err error) {
hook = new(Hook)
if !strings.EqualFold(req.Method, "POST") {
return nil, errors.New("Unknown method!")
}
Expand All @@ -57,17 +58,15 @@ func Parse(secret []byte, req *http.Request) (*Hook, error) {
return nil, errors.New("No event Id!")
}

body, err := ioutil.ReadAll(req.Body)

if err != nil {
return nil, err
}
hook.Payload, err = ioutil.ReadAll(req.Body)
return
}

if !verifySignature(secret, hook.Signature, body) {
return nil, errors.New("Invalid signature")
// Parse extracts and verifies a hook against a secret
func Parse(secret []byte, req *http.Request) (hook *Hook, err error) {
hook, err = New(req)
if err == nil && !hook.SignedBy(secret) {
err = errors.New("Invalid signature")
}

hook.Payload = body

return &hook, nil
return
}
13 changes: 9 additions & 4 deletions githubhook_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,11 @@ func expectErrorMessage(t *testing.T, msg string, err error) {
}
}

func expectNewError(t *testing.T, msg string, r *http.Request) {
_, err := New(r)
expectErrorMessage(t, msg, err)
}

func expectParseError(t *testing.T, msg string, r *http.Request) {
_, err := Parse([]byte(testSecret), r)
expectErrorMessage(t, msg, err)
Expand All @@ -33,25 +38,25 @@ func signature(body string) string {

func TestNonPost(t *testing.T) {
r, _ := http.NewRequest("GET", "/path", nil)
expectParseError(t, "Unknown method!", r)
expectNewError(t, "Unknown method!", r)
}

func TestMissingSignature(t *testing.T) {
r, _ := http.NewRequest("POST", "/path", nil)
expectParseError(t, "No signature!", r)
expectNewError(t, "No signature!", r)
}

func TestMissingEvent(t *testing.T) {
r, _ := http.NewRequest("POST", "/path", nil)
r.Header.Add("x-hub-signature", "bogus signature")
expectParseError(t, "No event!", r)
expectNewError(t, "No event!", r)
}

func TestMissingEventId(t *testing.T) {
r, _ := http.NewRequest("POST", "/path", nil)
r.Header.Add("x-hub-signature", "bogus signature")
r.Header.Add("x-github-event", "bogus event")
expectParseError(t, "No event Id!", r)
expectNewError(t, "No event Id!", r)
}

func TestInvalidSignature(t *testing.T) {
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