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// This file is part of gnunet-go, a GNUnet-implementation in Golang.
// Copyright (C) 2019-2022 Bernd Fix >Y<
//
// gnunet-go is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License,
// or (at your option) any later version.
//
// gnunet-go is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// SPDX-License-Identifier: AGPL3.0-or-later
package blocks
import (
"errors"
"fmt"
"gnunet/crypto"
"gnunet/util"
"github.com/bfix/gospel/data"
)
// Error messages
var (
ErrBlockNotDecrypted = fmt.Errorf("GNS block not decrypted")
)
//----------------------------------------------------------------------
// Query key for GNS lookups
//----------------------------------------------------------------------
// GNSQuery specifies the context for a basic GNS name lookup of an (atomic)
// label in a given zone identified by its public key.
type GNSQuery struct {
GenericQuery
Zone *crypto.ZoneKey // Public zone key
Label string // Atomic label
derived *crypto.ZoneKey // Derived zone key from (pkey,label)
}
// Verify the integrity of the block data from a signature.
func (q *GNSQuery) Verify(b Block) (err error) {
switch blk := b.(type) {
case *GNSBlock:
// Integrity check performed
blk.checked = true
// verify derived key
dkey := blk.DerivedKeySig.ZoneKey
dkey2, _ := q.Zone.Derive(q.Label, "gns")
if !dkey.Equal(dkey2) {
return fmt.Errorf("invalid signature key for GNS Block")
}
// verify signature
var buf []byte
if buf, err = data.Marshal(blk.Body); err != nil {
return
}
blk.verified, err = blk.DerivedKeySig.Verify(buf)
default:
err = errors.New("can't verify block type")
}
return
}
// Decrypt block data with a key derived from zone key and label.
func (q *GNSQuery) Decrypt(b Block) (err error) {
switch blk := b.(type) {
case *GNSBlock:
// decrypt GNS payload
blk.data, err = q.Zone.Decrypt(blk.Body.Data, q.Label, blk.Body.Expire)
blk.decrypted = true
return
default:
err = errors.New("can't decrypt block type")
}
return
}
// NewGNSQuery assembles a new Query object for the given zone and label.
func NewGNSQuery(zkey *crypto.ZoneKey, label string) *GNSQuery {
// derive a public key from (pkey,label) and set the repository
// key as the SHA512 hash of the binary key representation.
// (key blinding)
pd, _ := zkey.Derive(label, "gns")
gq := crypto.Hash(pd.Bytes()).Bits
return &GNSQuery{
GenericQuery: *NewGenericQuery(gq),
Zone: zkey,
Label: label,
derived: pd,
}
}
//----------------------------------------------------------------------
// GNS blocks
//----------------------------------------------------------------------
// SignedGNSBlockData represents the signed content of a GNS block
type SignedGNSBlockData struct {
Purpose *crypto.SignaturePurpose `` // Size and purpose of signature (8 bytes)
Expire util.AbsoluteTime `` // Expiration time of the block.
Data []byte `size:"*"` // Block data content
}
// GNSBlock is the result of GNS lookups for a given label in a zone.
// An encrypted and signed container for GNS resource records that represents
// the "atomic" data structure associated with a GNS label in a given zone.
type GNSBlock struct {
GenericBlock
// persistent
DerivedKeySig *crypto.ZoneSignature // Derived key used for signing
Body *SignedGNSBlockData
// transient data (not serialized)
checked bool // block integrity checked
verified bool // block signature verified (internal)
decrypted bool // block decrypted (internal)
data []byte // decrypted data
}
// Data block interface implementation
func (b *GNSBlock) Data() []byte {
buf, _ := data.Marshal(b)
return buf
}
// String returns the human-readable representation of a GNSBlock
func (b *GNSBlock) String() string {
return fmt.Sprintf("GNSBlock{Verified=%v,Decrypted=%v,data=[%d]}",
b.verified, b.decrypted, len(b.Body.Data))
}
// NewBlock instantiates an empty GNS block
func NewBlock() *GNSBlock {
return &GNSBlock{
DerivedKeySig: nil,
Body: &SignedGNSBlockData{
Purpose: new(crypto.SignaturePurpose),
Expire: *new(util.AbsoluteTime),
Data: nil,
},
checked: false,
verified: false,
decrypted: false,
data: nil,
}
}
// Verify the integrity of the block data from a signature.
// Only the cryptographic signature is verified; the formal correctness of
// the association between the block and a GNS label in a GNS zone can't
// be verified. This is only possible in Query.Verify().
func (b *GNSBlock) Verify() (err error) {
// verify signature
var buf []byte
if buf, err = data.Marshal(b.Body); err != nil {
return
}
_, err = b.DerivedKeySig.Verify(buf)
return
}
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