forked from runatlantis/atlantis
/
request_validation.go
72 lines (63 loc) · 1.85 KB
/
request_validation.go
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package bitbucketserver
import (
"crypto/hmac"
"crypto/sha1" // nolint: gosec
"crypto/sha256"
"crypto/sha512"
"encoding/hex"
"fmt"
"hash"
"strings"
"github.com/pkg/errors"
)
// Attribution: This code is taken from https://github.com/google/go-github.
func ValidateSignature(payload []byte, signature string, 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
}
// 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)
// nolint: errcheck
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 "sha1":
hashFunc = sha1.New
case "sha256":
hashFunc = sha256.New
case "sha512":
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
}