tordam

commit 4476e4b3a62aa25d375bd1fde5a1087aff54d77c
parent e2de1893f1c13c07b2394820fd224e1f58655a0f
Author: parazyd <parazyd@dyne.org>
Date:   Wed, 13 Dec 2017 00:57:35 +0100

Implement ed25519 functionality.

This will come handy later on when Tor v3 hidden services are supported
in ControlPort spec.

Diffstat:
M
README.md
 | 
2
++
A
pkg/damlib/crypto_25519.go
 | 
108
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 110 insertions(+), 0 deletions(-)
diff --git a/README.md b/README.md
@@ -18,6 +18,8 @@ go get -u github.com/parazyd/tor-dam/...
 #### Go
 
 ```
+golang.org/x/crypto/ed25519
+golang.org/x/crypto/sha3
 golang.org/x/net/proxy
 github.com/go-redis/redis
 ```
diff --git a/pkg/damlib/crypto_25519.go b/pkg/damlib/crypto_25519.go
@@ -0,0 +1,108 @@
+package damlib
+
+// See LICENSE file for copyright and license details.
+
+import (
+	"crypto/rand"
+	"encoding/base32"
+	"io/ioutil"
+	"log"
+	"strings"
+
+	"golang.org/x/crypto/ed25519"
+	"golang.org/x/crypto/sha3"
+)
+
+// GenEd25519 generates an ed25519 keypair. Returns error on failure.
+func GenEd25519() (ed25519.PublicKey, ed25519.PrivateKey, error) {
+	log.Println("Generating ed25519 keypair...")
+	rng := rand.Reader
+	pk, sk, err := ed25519.GenerateKey(rng)
+	if err != nil {
+		return nil, nil, err
+	}
+	return pk, sk, nil
+}
+
+// SavePubEd25519 writes a ed25519.PublicKey type to a given string filename.
+// Returns error upon failure.
+func SavePubEd25519(filename string, key ed25519.PublicKey) error {
+	log.Println("Writing ed25519 public key to", filename)
+	const pkprefix = "== ed25519v1-public: type0 =="
+	var pub []byte
+	for _, i := range []byte(pkprefix) {
+		pub = append(pub, i)
+	}
+	for _, i := range []byte(key) {
+		pub = append(pub, i)
+	}
+	if err := ioutil.WriteFile(filename, pub, 0600); err != nil {
+		return err
+	}
+	return nil
+}
+
+// SavePrivEd25519 writes a ed25519.PrivateKey type to a given string filename.
+// Returns error upon failure.
+func SavePrivEd25519(filename string, key ed25519.PrivateKey) error {
+	log.Println("Writing ed25519 private key to", filename)
+	const skprefix = "== ed25519v1-secret: type0 =="
+	var sec []byte
+	for _, i := range []byte(skprefix) {
+		sec = append(sec, i)
+	}
+	for _, i := range []byte(key) {
+		sec = append(sec, i)
+	}
+	if err := ioutil.WriteFile(filename, sec, 0600); err != nil {
+		return err
+	}
+	return nil
+}
+
+// OnionFromPubkeyEd25519 generates a valid onion address from a given ed25519
+// public key. Returns the onion address as a slice of bytes.
+//
+// Tor Spec excerpt from https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt
+// ---
+// 6. Encoding onion addresses [ONIONADDRESS]
+// The onion address of a hidden service includes its identity public key, a
+// version field and a basic checksum. All this information is then base32
+// encoded as shown below:
+//
+//		onion_address = base32(PUBKEY | CHECKSUM | VERSION) + ".onion"
+//		CHECKSUM = H(".onion checksum" | PUBKEY | VERSION)[:2]
+//
+//		where:
+//			- PUBKEY is the 32 bytes ed25519 master pubkey of the hidden service.
+//			- VERSION is an one byte version field (default value '\x03')
+//			- ".onion checksum" is a constant string
+//			- CHECKSUM is truncated to two bytes before inserting it in onion_address
+func OnionFromPubkeyEd25519(pubkey ed25519.PublicKey) []byte {
+	const hashConst = ".onion checksum"
+	const versConst = '\x03'
+
+	var h []byte
+	for _, i := range []byte(hashConst) {
+		h = append(h, i)
+	}
+	for _, i := range []byte(pubkey) {
+		h = append(h, i)
+	}
+	h = append(h, byte(versConst))
+
+	csum := sha3.Sum256(h)
+	checksum := csum[:2]
+
+	var enc []byte
+	for _, i := range []byte(pubkey) {
+		enc = append(enc, i)
+	}
+	for _, i := range checksum {
+		enc = append(enc, i)
+	}
+	enc = append(enc, byte(versConst))
+
+	encoded := base32.StdEncoding.EncodeToString(enc)
+	return []byte(strings.ToLower(encoded) + ".onion")
+}