milestone 1: parsing of input.json seems to work

3 files changed, 263 insertions, 39 deletions

diff --git a/cmd/taler-auditor-offline-signing/main.go b/cmd/taler-auditor-offline-signing/main.go
index f9050e1..bbab9fb 100644
--- a/cmd/taler-auditor-offline-signing/main.go
+++ b/cmd/taler-auditor-offline-signing/main.go
@@ -1,35 +1,94 @@
+/*
+taler-auditor-offline will become a standalone offline signing tool for GNU
+Taler.  It is an implementation in Go of
+https://git.taler.net/exchange.git/tree/src/exchange-tools/taler-auditor-offline.c
+in order to simplify portability (to ARM f.e.).
+
+TODOs:
+  - implement sign operation
+  - implement JSON-encoding of
+     - hashes
+     - keys
+     - signatures
+  - factor out types and helper functions to own package codeblau.de/taler
+  - implement full functionality from origin
+
+*/
 package main
 
 import (
+	"bytes"
+	"crypto/ed25519"
 	"crypto/rsa"
-	"encoding/base32"
 	"encoding/binary"
+	"encoding/json"
 	"fmt"
+	"log"
 	"math/big"
+	"os"
+	"regexp"
+	"strconv"
+
+	"github.com/davecgh/go-spew/spew"
 )
 
-type Keys struct {
-	Denoms          []DenomKey      `json:"denoms"`
-	MasterPublicKey MasterPublicKey `json:"master_public_key"`
+type Data struct {
+	Operation string `json:"operation"`
+	Arguments struct {
+		Version             string         `json:"version"`
+		Currency            string         `json:"currency"`
+		MasterPublicKey     EdDSAPublicKey `json:"master_public_key"`
+		ReserveClosingDelay RelativeTime   `json:"reserve_closing_delay"`
+		Signkeys            []SignKey      `json:"signkeys"`
+		Denoms              []DenomKey     `json:"denoms"`
+		// Recoup []??? `json:"recoup"`
+	} `json:"arguments"`
 }
 
-type MasterPublicKey [256 / 8]byte
+type SignKey struct {
+	MasterSig   EdDSASignature `json:"master_sig"`
+	StampStart  AbsoluteTime   `json:"stamp_start"`
+	StampExpire AbsoluteTime   `json:"stamp_expire"`
+	StampEnd    AbsoluteTime   `json:"stamp_end"`
+	Key         EdDSAPublicKey `json:"key"`
+}
 
 type DenomKey struct {
-	DenomPub            EncodedRSAPublicKey `json:"denom_pub"`
-	Value               Amount              `json:"value"`
-	FeeWithdraw         Amount              `json:"fee_withdraw"`
-	FeeDeposit          Amount              `json:"fee_deposit"`
-	FeeRefresh          Amount              `json:"fee_refresh"`
-	FeeRefund           Amount              `json:"fee_refund"`
-	StampStart          AbsoluteTime        `json:"stamp_start"`
-	StampExpireWithdraw AbsoluteTime        `json:"stamp_expire_withdraw"`
-	StampExpireDeposit  AbsoluteTime        `json:"stamp_expire_deposit"`
-	StampExpireLegal    AbsoluteTime        `json:"stamp_expire_legal"`
-	MasterSig           EdDSASignature      `json:"master_sig"`
+	DenomPub            RSAPublicKey   `json:"denom_pub"`
+	Value               Amount         `json:"value"`
+	FeeWithdraw         Amount         `json:"fee_withdraw"`
+	FeeDeposit          Amount         `json:"fee_deposit"`
+	FeeRefresh          Amount         `json:"fee_refresh"`
+	FeeRefund           Amount         `json:"fee_refund"`
+	StampStart          AbsoluteTime   `json:"stamp_start"`
+	StampExpireWithdraw AbsoluteTime   `json:"stamp_expire_withdraw"`
+	StampExpireDeposit  AbsoluteTime   `json:"stamp_expire_deposit"`
+	StampExpireLegal    AbsoluteTime   `json:"stamp_expire_legal"`
+	MasterSig           EdDSASignature `json:"master_sig"`
+}
+
+type AbsoluteTime struct {
+	// TODO: en-/decode "never"
+	TMs uint64 `json:"t_ms"`
+}
+
+type RelativeTime struct {
+	// TODO: en-/decode "forever"
+	DMs uint64 `json:"d_ms"`
 }
 
-type EncodedRSAPublicKey []byte
+type EdDSAPublicKey ed25519.PublicKey
+
+func (ep *EdDSAPublicKey) UnmarshalJSON(in []byte) (e error) {
+	var buf []byte
+	// decode crockford.base32
+	if buf, e = crockfordDecode(bytes.Trim(in, `"`)); e != nil {
+		return fmt.Errorf("couldn't decode EncodedRSAPublicKey as crockford.base32: %v (%v)", e, string(in))
+	}
+
+	*ep = EdDSAPublicKey(buf)
+	return nil
+}
 
 const (
 	CURRENCY_LEN     = 12
@@ -37,55 +96,216 @@ const (
 )
 
 type Amount struct {
-	Value    uint64             `json:"value"`
-	Fraction uint32             `json:"fraction"`
-	Currency [CURRENCY_LEN]byte `json:"currency"`
+	Value    uint64 `json:"value"`
+	Fraction uint32 `json:"fraction"`
+	Currency string `json:"currency"`
 }
 
-type AbsoluteTime uint64
+// Amount comes in as something like "CHF:0.32"
+// see https://docs.taler.net/core/api-common.html#amounts
+var nonAllowedCharsRX = regexp.MustCompile("[^a-zA-Z]")
+
+func (a *Amount) UnmarshalJSON(in []byte) (e error) {
+	// split and parse Currency
+	parts := bytes.Split(bytes.Trim(in, `"`), []byte(":"))
+	if len(parts) != 2 {
+		return fmt.Errorf("invalid amount sequence")
+	} else if len(parts[0]) >= CURRENCY_LEN || nonAllowedCharsRX.Match(parts[0]) {
+		return fmt.Errorf("invalid currency")
+	}
+	a.Currency = string(parts[0])
+
+	// split and parse Value
+	parts = bytes.Split(parts[1], []byte("."))
+	if len(parts) > 2 || len(parts[0]) == 0 {
+		return fmt.Errorf("invalid decimal value")
+	} else if a.Value, e = strconv.ParseUint(string(parts[0]), 10, 64); e != nil {
+		return e
+	} else if a.Value > 2<<52 {
+		return fmt.Errorf("decimal value too large")
+	}
+
+	// parse Fraction
+	if len(parts) == 2 {
+		if len(parts[1]) == 0 || len(parts[1]) > 8 {
+			return fmt.Errorf("invalid fraction")
+		} else if v, e := strconv.ParseUint(string(parts[1]), 10, 32); e != nil {
+			return e
+		} else {
+			a.Fraction = uint32(v)
+		}
+	}
+
+	return nil
+}
 
 type EdDSASignature struct {
-	R [256 / 8]byte `json:"r"`
-	S [256 / 8]byte `json:"s"`
+	R []byte `json:"r"`
+	S []byte `json:"s"`
 }
 
+// copy of GNUNET_STRINGS_string_to_data from gnunet/src/util/strings.c
+func crockfordDecode(enc []byte) ([]byte, error) {
+	if len(enc) == 0 {
+		return nil, nil
+	}
+
+	out_size := (len(enc) * 5) / 8
+	if out_size > 2<<24 {
+		return nil, fmt.Errorf("input too large")
+	}
+
+	var (
+		out                    = make([]byte, out_size)
+		encoded_len            = out_size * 8
+		rpos                   = len(enc)
+		vbit, bits, ret, shift int
+	)
+
+	if encoded_len%5 > 0 {
+		vbit = encoded_len % 5 // padding! !?
+		shift = 5 - vbit
+		rpos--
+		ret = getValue(enc[rpos])
+		bits = ret >> shift
+	} else {
+		vbit = 5
+		shift = 0
+		rpos--
+		ret = getValue(enc[rpos])
+		bits = ret
+	}
+
+	if ((encoded_len + shift) / 5) != len(enc) {
+		return nil, fmt.Errorf("encoding length mismatch: %d vs %d (%v)", (encoded_len+shift)/5, len(enc), enc)
+	} else if ret == -1 {
+		return nil, fmt.Errorf("invalid character? getValue returned -1")
+	}
+
+	for wpos := out_size; wpos > 0; {
+		if 0 == rpos {
+			return nil, fmt.Errorf("incomplete encoding")
+		}
+		rpos--
+		ret = getValue(enc[rpos]) << vbit
+		bits = ret | bits
+		if -1 == ret {
+			return nil, fmt.Errorf("incorrect encoding")
+		}
+		vbit += 5
+		if vbit >= 8 {
+			wpos--
+			out[wpos] = byte(bits)
+			bits >>= 8
+			vbit -= 8
+		}
+	}
+
+	if 0 != rpos || 0 != vbit {
+		return nil, fmt.Errorf("incorrectly ended")
+	}
+
+	return out, nil
+}
+
+func getValue(a byte) int {
+	// exluded letters
+	switch a {
+	case '0', 'o':
+		a = '0'
+	case 'i', 'I', 'l', 'L':
+		a = '1'
+	case 'u', 'U':
+		a = 'V'
+	}
+
+	if a >= '0' && a <= '9' {
+		return int(a - '0')
+	}
+	if a >= 'a' && a <= 'z' {
+		a = a - 'a' + 'A'
+	}
+
+	dec := 0
+	if a >= 'A' && a <= 'Z' {
+		if 'I' < a {
+			dec++
+		}
+		if 'L' < a {
+			dec++
+		}
+		if 'O' < a {
+			dec++
+		}
+		if 'U' < a {
+			dec++
+		}
+		return int(a) - 'A' + 10 - dec
+	}
+
+	return -1
+}
+
+func (es *EdDSASignature) UnmarshalJSON(in []byte) (e error) {
+	var buf []byte
+
+	// 1. decode crockford.base32
+	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 {
+		return fmt.Errorf("unknown data as signature: %v", buf)
+	}
+
+	es.R = buf[0:32]
+	es.S = buf[32:64]
+
+	return nil
+}
+
+type RSAPublicKey rsa.PublicKey
+
 // following gnunet/src/json/json_helper.c and gnunet/src/util/crypto_rsa.c
-func (ep *EncodedRSAPublicKey) Decode() (p rsa.PublicKey, e error) {
+func (ep *RSAPublicKey) UnmarshalJSON(in []byte) (e error) {
 	var buf []byte
 
-	// 1. decode base32
-	_, e = base32.StdEncoding.Decode(buf, *ep)
-	if e != nil {
-		return
+	// 1. decode crockford.base32
+	if buf, e = crockfordDecode(bytes.Trim(in, `"`)); e != nil {
+		return fmt.Errorf("couldn't decode EncodedRSAPublicKey as crockford.base32: %v (%v)", e, string(in))
 	}
 
 	// 2. parse header
 	if len(buf) < 4 {
-		e = fmt.Errorf("byte array too small for RSA public key header")
-		return
+		return fmt.Errorf("byte array too small for RSA public key header")
 	}
 	modulus_length, public_exponent_length := binary.BigEndian.Uint16(buf[0:]), binary.BigEndian.Uint16(buf[2:])
 	if len(buf[4:]) != int(modulus_length)+int(public_exponent_length) {
-		e = fmt.Errorf("byte array has wrong size according to encoded length's for modulus and public exponent")
-		return
+		return fmt.Errorf("byte array has wrong size according to encoded length's for modulus and public exponent")
 	}
 
 	// 3. parse RSA public key
-	// BUG! This is most likely wrong.
 	// Consult _gcry_mpi_set_buffer from libgcrypt-1.9.4/mpi/mpicoder.c
 	buf = buf[4:]
-	p.N = big.NewInt(0).SetBytes(buf[:modulus_length])
+	ep.N = big.NewInt(0).SetBytes(buf[:modulus_length])
 	buf = buf[modulus_length:]
 	ex := big.NewInt(0).SetBytes(buf[:public_exponent_length]) // binary.BigEndian.Uint64 instead?
 	if !ex.IsInt64() {
-		e = fmt.Errorf("public exponent is not int64")
-		return
+		return fmt.Errorf("public exponent is not int64")
 	}
-	p.E = int(ex.Int64())
+	ep.E = int(ex.Int64())
 
-	return p, e
+	return nil
 }
 
 func main() {
-	panic("nothing implemented yet.")
+	data := new(Data)
+	dec := json.NewDecoder(os.Stdin)
+	e := dec.Decode(data)
+	if e != nil {
+		log.Fatal(e)
+	}
+
+	spew.Dump(data)
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("Data:", "  ")
+	enc.Encode(data)
 }
diff --git a/go.mod b/go.mod
index 66c8161..25da996 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,5 @@
 module codeblau.de/taler
 
 go 1.17
+
+require github.com/davecgh/go-spew v1.1.1 // indirect
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..b5e2922
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,2 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=