[#290] object/rangehash: Add salt to RangeHashPrm structure

Add binary salt field to RangeHashPrm struct. Implement field setter. Set
salt from the request in v2 service.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/object/get/prm.go

@@ -28,6 +28,8 @@ type RangeHashPrm struct {
 	hashGen func() hash.Hash
 
 	rngs []*objectSDK.Range
+
+	salt []byte
 }
 
 // HeadPrm groups parameters of Head service call.
@@ -88,6 +90,11 @@ func (p *RangeHashPrm) SetHashGenerator(v func() hash.Hash) {
 	p.hashGen = v
 }
 
+// SetSalt sets binary salt to XOR object's payload ranges before hash calculation.
+func (p *RangeHashPrm) SetSalt(salt []byte) {
+	p.salt = salt
+}
+
 // SetCommonParameters sets common parameters of the operation.
 func (p *commonPrm) SetCommonParameters(common *util.CommonPrm) {
 	p.common = common

pkg/services/object/get/v2/util.go

@@ -83,6 +83,7 @@ func (s *Service) toHashRangePrm(req *objectV2.GetRangeHashRequest) (*getsvc.Ran
 	}
 
 	p.SetRangeList(rngs)
+	p.SetSalt(body.GetSalt())
 
 	switch t := body.GetType(); t {
 	default: