8000 Swaps in SHA256 signature (fixes #13) by rjz · Pull Request #15 · rjz/githubhook · GitHub
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Swaps in SHA256 signature (fixes #13) #15

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Merged
merged 1 commit into from
Mar 3, 2023
Merged

Swaps in SHA256 signature (fixes #13) #15

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21 changes: 12 additions & 9 deletions githubhook.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@ package githubhook

import (
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"encoding/hex"
"encoding/json"
"errors"
Expand Down Expand Up @@ -37,11 +37,12 @@ type Hook struct {
Payload []byte
}

const signaturePrefix = "sha1="
const signatureLength = 45 // len(SignaturePrefix) + len(hex(sha1))
const signaturePrefix = "sha256="
const prefixLength = len(signaturePrefix)
const signatureLength = prefixLength + (sha256.Size * 2)

func signBody(secret, body []byte) []byte {
computed := hmac.New(sha1.New, secret)
computed := hmac.New(sha256.New, secret)
computed.Write(body)
return []byte(computed.Sum(nil))
}
Expand All @@ -55,13 +56,15 @@ func (h *Hook) SignedBy(secret []byte) bool {
return false
}

actual := make([]byte, 20)
hex.Decode(actual, []byte(h.Signature[5:]))
actual := make([]byte, sha256.Size)
hex.Decode(actual, []byte(h.Signature[prefixLength:]))

return hmac.Equal(signBody(secret, h.Payload), actual)
expected := signBody(secret, h.Payload)

return hmac.Equal(expected, actual)
}

// Extract unmarshals Payload into a destination interface.
// Extract hook's JSON payload into dst
func (h *Hook) Extract(dst interface{}) error {
return json.Unmarshal(h.Payload, dst)
}
Expand All @@ -73,7 +76,7 @@ func New(req *http.Request) (hook *Hook, err error) {
return nil, errors.New("Unknown method!")
}

if hook.Signature = req.Header.Get("x-hub-signature"); len(hook.Signature) == 0 {
if hook.Signature = req.Header.Get("x-hub-signature-256"); len(hook.Signature) == 0 {
return nil, errors.New("No signature!")
}

Expand Down
16 changes: 8 additions & 8 deletions githubhook_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ package githubhook

import (
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"encoding/hex"
"fmt"
"net/http"
Expand All @@ -29,11 +29,11 @@ func expectParseError(t *testing.T, msg string, r *http.Request) {
}

func signature(body string) string {
dst := make([]byte, 40)
computed := hmac.New(sha1.New, []byte(testSecret))
dst := make([]byte, sha256.Size*2)
computed := hmac.New(sha256.New, []byte(testSecret))
computed.Write([]byte(body))
hex.Encode(dst, computed.Sum(nil))
return "sha1=" + string(dst)
return signaturePrefix + string(dst)
}

func TestNonPost(t *testing.T) {
Expand All @@ -48,20 +48,20 @@ func TestMissingSignature(t *testing.T) {

func TestMissingEvent(t *testing.T) {
r, _ := http.NewRequest("POST", "/path", nil)
r.Header.Add("x-hub-signature", "bogus signature")
r.Header.Add("x-hub-signature-256", "bogus signature")
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-hub-signature-256", "bogus signature")
r.Header.Add("x-github-event", "bogus event")
expectNewError(t, "No event Id!", r)
}

func TestInvalidSignature(t *testing.T) {
r, _ := http.NewRequest("POST", "/path", strings.NewReader("..."))
r.Header.Add("x-hub-signature", "bogus signature")
r.Header.Add("x-hub-signature-256", "bogus signature")
r.Header.Add("x-github-event", "bogus event")
r.Header.Add("x-github-delivery", "bogus id")
expectParseError(t, "Invalid signature", r)
Expand All @@ -72,7 +72,7 @@ func TestValidSignature(t *testing.T) {
body := "{}"

r, _ := http.NewRequest("POST", "/path", strings.NewReader(body))
r.Header.Add("x-hub-signature", signature(body))
r.Header.Add("x-hub-signature-256", signature(body))
r.Header.Add("x-github-event", "bogus event")
r.Header.Add("x-github-delivery", "bogus id")

Expand Down
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