/
ref.go
164 lines (143 loc) · 3.52 KB
/
ref.go
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package bigblob
import (
"bytes"
"context"
"crypto/hmac"
"encoding/base64"
"encoding/json"
"fmt"
"io"
"strings"
"github.com/brendoncarroll/go-state/cadata"
"golang.org/x/crypto/chacha20"
"lukechampine.com/blake3"
)
var encoding = base64.NewEncoding(cadata.Base64Alphabet)
const DEKSize = 32
type DEK [DEKSize]byte
func (dek DEK) MarshalJSON() (ret []byte, _ error) {
return json.Marshal(encoding.EncodeToString(dek[:]))
}
func (dek *DEK) UnmarshalJSON(data []byte) error {
var s string
if err := json.Unmarshal(data, &s); err != nil {
return err
}
data, err := encoding.DecodeString(s)
if err != nil {
return err
}
copy(dek[:], data)
return nil
}
// RefSize is the size of a Ref marshalled to binary
const RefSize = cadata.IDSize + DEKSize
// Ref is a reference to data in a content-addressed store
type Ref struct {
CID cadata.ID `json:"cid"`
DEK DEK `json:"dek"`
}
func RefFromBytes(x []byte) (*Ref, error) {
if len(x) < RefSize {
return nil, fmt.Errorf("too small to be ref len=%d", len(x))
}
r := Ref{}
br := bytes.NewReader(x)
for _, slice := range [][]byte{
r.CID[:],
r.DEK[:],
} {
if _, err := io.ReadFull(br, slice); err != nil {
return nil, err
}
}
return &r, nil
}
func (r Ref) MarshalBinary() ([]byte, error) {
buf := make([]byte, 0, RefSize)
buf = append(buf, r.CID[:]...)
buf = append(buf, r.DEK[:]...)
return buf, nil
}
func (r Ref) Key() (ret [32]byte) {
buf, _ := r.MarshalBinary()
return blake3.Sum256(buf[:])
}
func (r1 Ref) Equals(r2 Ref) bool {
return hmac.Equal(r1.CID[:], r2.CID[:]) && hmac.Equal(r1.DEK[:], r2.DEK[:])
}
func marshalRef(x Ref) []byte {
data, _ := x.MarshalBinary()
return data
}
func (ag *Agent) post(ctx context.Context, s cadata.Poster, salt *[32]byte, ptext []byte) (*Ref, error) {
buf := ag.acquireBuffer(len(ptext))
defer ag.releaseBuffer(buf)
ctext := make([]byte, len(ptext))
dek := encrypt(salt, ctext, ptext)
cid, err := s.Post(ctx, ctext)
if err != nil {
return nil, err
}
return &Ref{
CID: cid,
DEK: dek,
}, nil
}
func (ag *Agent) getF(ctx context.Context, s cadata.Getter, ref Ref, fn func([]byte) error) error {
if value, ok := ag.cache.Get(ref.Key()); ok {
return fn(value.([]byte))
}
buf := make([]byte, s.MaxSize())
n, err := s.Get(ctx, ref.CID, buf)
if err != nil {
return err
}
if err := cadata.Check(s.Hash, ref.CID, buf[:n]); err != nil {
return err
}
cryptoXOR(ref.DEK, buf[:n], buf[:n])
data := buf[:n]
ag.cache.Add(ref.Key(), data)
return fn(data)
}
func encrypt(salt *[32]byte, ctext, ptext []byte) DEK {
if len(ctext) != len(ptext) {
panic("len(ctext) != len(ptext)")
}
dek := makeDEK(salt, ptext)
cryptoXOR(dek, ctext, ptext)
return dek
}
func cryptoXOR(key DEK, dst, src []byte) {
nonce := [chacha20.NonceSize]byte{} // 0
ciph, err := chacha20.NewUnauthenticatedCipher(key[:], nonce[:])
if err != nil {
panic(err)
}
ciph.XORKeyStream(dst, src)
}
func makeDEK(salt *[32]byte, ptext []byte) (dek DEK) {
DeriveKey(dek[:], salt, ptext)
return dek
}
// DeriveKey uses BLAKE3 keyed with salt, to absorb input, and derive a new key into out
func DeriveKey(out []byte, salt *[32]byte, input []byte) {
h := blake3.New(len(out), salt[:])
if _, err := h.Write(input); err != nil {
panic(err)
}
xof := h.XOF()
if _, err := io.ReadFull(xof, out); err != nil {
panic(err)
}
}
func dumpStore(x cadata.Store) string {
sb := strings.Builder{}
cadata.ForEach(context.TODO(), x, cadata.Span{}, func(x cadata.ID) error {
sb.WriteString(x.String())
sb.WriteString("\n")
return nil
})
return sb.String()
}