From 63963e3fa5131113b1442d1fd22e40e9d571f32e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=96zg=C3=BCr=20Kesim?= <oec-taler@kesim.org>
Date: Tue, 19 Oct 2021 10:56:33 +0200
Subject: [PATCH] output encoding of keys with crockford (the Taler flavor)
 done

---
 cmd/taler-auditor-offline-signing/main.go | 118 ++++++++++++++++++++--
 1 file changed, 108 insertions(+), 10 deletions(-)

diff --git a/cmd/taler-auditor-offline-signing/main.go b/cmd/taler-auditor-offline-signing/main.go
index bbab9fb..2f192c7 100644
--- a/cmd/taler-auditor-offline-signing/main.go
+++ b/cmd/taler-auditor-offline-signing/main.go
@@ -28,11 +28,9 @@ import (
 	"os"
 	"regexp"
 	"strconv"
-
-	"github.com/davecgh/go-spew/spew"
 )
 
-type Data struct {
+type Input struct {
 	Operation string `json:"operation"`
 	Arguments struct {
 		Version             string         `json:"version"`
@@ -90,6 +88,20 @@ func (ep *EdDSAPublicKey) UnmarshalJSON(in []byte) (e error) {
 	return nil
 }
 
+func (ep *EdDSAPublicKey) MarshalJSON() ([]byte, error) {
+	enc, e := crockfordEncode([]byte(*ep))
+	if e != nil {
+		return nil, e
+	}
+
+	buf := make([]byte, len(enc)+2)
+	buf[0] = '"'
+	buf[len(buf)-1] = '"'
+	copy(buf[1:], enc)
+
+	return buf, nil
+}
+
 const (
 	CURRENCY_LEN     = 12
 	CURRENCY_LEN_STR = "12"
@@ -246,10 +258,39 @@ func getValue(a byte) int {
 	return -1
 }
 
+// Copy of GNUNET_STRINGS_data_to_string from gnunet/src/util/strings.c
+func crockfordEncode(in []byte) ([]byte, error) {
+	const encTable = "0123456789ABCDEFGHJKMNPQRSTVWXYZ"
+
+	var (
+		out              []byte
+		rpos, bits, vbit int
+	)
+
+	for rpos < len(in) || vbit > 0 {
+		if rpos < len(in) && vbit < 5 {
+			bits = (bits << 8) | int(in[rpos]) // eat 8 more bits
+			rpos++
+			vbit += 8
+		}
+		if vbit < 5 {
+			bits <<= (5 - vbit) // zero-padding
+			if vbit != (len(in)*8)%5 {
+				return nil, fmt.Errorf("vbit (%d) != (len(in)*8)%%5 (%d)", vbit, (len(in)*8)%5)
+			}
+			vbit = 5
+		}
+		vbit -= 5
+		out = append(out, encTable[(bits>>vbit)&31])
+	}
+
+	return out, nil
+}
+
 func (es *EdDSASignature) UnmarshalJSON(in []byte) (e error) {
 	var buf []byte
 
-	// 1. decode crockford.base32
+	// Decode crockford.base32, the Taler flavour
 	if buf, e = crockfordDecode(bytes.Trim(in, `"`)); e != nil {
 		return fmt.Errorf("couldn't decode EdDSASignature as crockford.base32: %v (%v)", e, string(in))
 	} else if len(buf) != 64 {
@@ -262,13 +303,31 @@ func (es *EdDSASignature) UnmarshalJSON(in []byte) (e error) {
 	return nil
 }
 
+func (es *EdDSASignature) MarshalJSON() (b []byte, e error) {
+	var buf = make([]byte, len(es.R)+len(es.S))
+	copy(buf, es.R)
+	copy(buf[len(es.R):], es.S)
+
+	enc, err := crockfordEncode(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	b = make([]byte, len(enc)+2)
+	b[0] = '"'
+	b[len(b)-1] = '"'
+	copy(b[1:], enc)
+
+	return b, nil
+}
+
 type RSAPublicKey rsa.PublicKey
 
 // following gnunet/src/json/json_helper.c and gnunet/src/util/crypto_rsa.c
 func (ep *RSAPublicKey) UnmarshalJSON(in []byte) (e error) {
 	var buf []byte
 
-	// 1. decode crockford.base32
+	// 1. decode crockford.base32, the Taler flavour
 	if buf, e = crockfordDecode(bytes.Trim(in, `"`)); e != nil {
 		return fmt.Errorf("couldn't decode EncodedRSAPublicKey as crockford.base32: %v (%v)", e, string(in))
 	}
@@ -296,16 +355,55 @@ func (ep *RSAPublicKey) UnmarshalJSON(in []byte) (e error) {
 	return nil
 }
 
+func (ep *RSAPublicKey) MarshalJSON() (b []byte, e error) {
+	nb := ep.N.Bytes()
+	eb := big.NewInt(int64(ep.E)).Bytes()
+	if len(nb) > 2<<16-1 || len(eb) > 2<<16-1 {
+		return nil, fmt.Errorf("values too large")
+	}
+
+	buf := make([]byte, 4+len(nb)+len(eb))
+	binary.BigEndian.PutUint16(buf, uint16(len(nb)))
+	binary.BigEndian.PutUint16(buf[2:], uint16(len(eb)))
+	copy(buf[4:], nb)
+	copy(buf[4+len(nb):], eb)
+
+	enc, err := crockfordEncode(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	b = make([]byte, len(enc)+2)
+	b[0] = '"'
+	b[len(b)-1] = '"'
+	copy(b[1:], enc)
+
+	return b, nil
+}
+
+type Output []SignOperation
+
+type SignOperation struct {
+	Operation string `json:"operation"`
+	Arguments struct {
+		HDenumPub  RSAPublicKey   `json:"h_denum_pub"`
+		AuditorSig EdDSASignature `json:"auditor_sig"`
+	} `json:"arguments"`
+}
+
 func main() {
-	data := new(Data)
+	input := new(Input)
 	dec := json.NewDecoder(os.Stdin)
-	e := dec.Decode(data)
+	e := dec.Decode(input)
 	if e != nil {
 		log.Fatal(e)
 	}
 
-	spew.Dump(data)
 	enc := json.NewEncoder(os.Stdout)
-	enc.SetIndent("Data:", "  ")
-	enc.Encode(data)
+	enc.SetIndent("Input:", "  ")
+	e = enc.Encode(input)
+	if e != nil {
+		log.Fatal(e)
+	}
+
 }