token: don't store the CID in the token, symmetric API for sealed

token/read.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/ipfs/go-cid"
 	"github.com/ipld/go-ipld-prime"
 	"github.com/ipld/go-ipld-prime/codec"
 	"github.com/ipld/go-ipld-prime/codec/dagcbor"
@@ -15,12 +16,51 @@ import (
 	"github.com/ucan-wg/go-ucan/token/invocation"
 )
 
+// FromSealed decodes an arbitrary token type from the binary data,
+// verifies that the envelope's signature is correct based on the public
+// key taken from the issuer (iss) field and calculates the CID of the
+// incoming data.
+// Supported and returned types are:
+// - delegation.Token
+// - invocation.Token
+func FromSealed(data []byte) (Token, cid.Cid, error) {
+	tkn, err := FromDagCbor(data)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	id, err := envelope.CIDFromBytes(data)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	return tkn, id, nil
+}
+
+// FromSealedReader is the same as Unseal but accepts an io.Reader.
+func FromSealedReader(r io.Reader) (Token, cid.Cid, error) {
+	cidReader := envelope.NewCIDReader(r)
+
+	tkn, err := FromDagCborReader(cidReader)
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	id, err := cidReader.CID()
+	if err != nil {
+		return nil, cid.Undef, err
+	}
+
+	return tkn, id, nil
+}
+
 // Decode unmarshals the input data using the format specified by the
 // provided codec.Decoder into an arbitrary UCAN token.
 // An error is returned if the conversion fails, or if the resulting
 // Token is invalid.
 // Supported and returned types are:
 // - delegation.Token
+// - invocation.Token
 func Decode(b []byte, decFn codec.Decoder) (Token, error) {
 	node, err := ipld.Decode(b, decFn)
 	if err != nil {
@@ -43,6 +83,7 @@ func DecodeReader(r io.Reader, decFn codec.Decoder) (Token, error) {
 // Token is invalid.
 // Supported and returned types are:
 // - delegation.Token
+// - invocation.Token
 func FromDagCbor(b []byte) (Token, error) {
 	return Decode(b, dagcbor.Decode)
 }
@@ -57,6 +98,7 @@ func FromDagCborReader(r io.Reader) (Token, error) {
 // Token is invalid.
 // Supported and returned types are:
 // - delegation.Token
+// - invocation.Token
 func FromDagJson(b []byte) (Token, error) {
 	return Decode(b, dagjson.Decode)
 }