From 8ebbdab5079f803567297af842c87ce012b7ea11 Mon Sep 17 00:00:00 2001
From: Andrew <saintruler@gmail.com>
Date: Wed, 28 Apr 2021 20:31:16 +0400
Subject: Added cryptography functions and completed client and server.

---
 http-client/cryptography.go | 60 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 http-client/cryptography.go

(limited to 'http-client/cryptography.go')

diff --git a/http-client/cryptography.go b/http-client/cryptography.go
new file mode 100644
index 0000000..175e60b
--- /dev/null
+++ b/http-client/cryptography.go
@@ -0,0 +1,60 @@
+package main
+
+import (
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha256"
+	"crypto/x509"
+	"encoding/asn1"
+	"encoding/base64"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+)
+
+const KeyBitSize = 4096
+
+// Приватный ключ - отдаётся серверу
+// Публичный ключ - сохраняется на клиенте
+
+func signRequest(req Request, key *rsa.PublicKey) (string, error) {
+	body, _ := json.Marshal(req)
+	based := base64.StdEncoding.EncodeToString(body)
+	h := sha256.Sum256([]byte(based))
+	requestHash := fmt.Sprintf("%x", h)
+
+	ciphertext, err := rsa.EncryptPKCS1v15(rand.Reader, key, []byte(requestHash))
+	if err != nil {
+		return "", nil
+	}
+
+	signature := base64.StdEncoding.EncodeToString(ciphertext)
+	return fmt.Sprintf("%s.%s", based, signature), nil
+}
+
+func parseKey(keyBytes []byte) (*rsa.PublicKey, error) {
+	block, _ := pem.Decode(keyBytes)
+	return x509.ParsePKCS1PublicKey(block.Bytes)
+}
+
+func generateKeys() (private []byte, public []byte, err error) {
+	key, err := rsa.GenerateKey(rand.Reader, KeyBitSize)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var privateKey = &pem.Block{
+		Type:  "PRIVATE KEY",
+		Bytes: x509.MarshalPKCS1PrivateKey(key),
+	}
+
+	asn1Bytes, _ := asn1.Marshal(key.PublicKey)
+	var publicKey = &pem.Block{
+		Type:  "PUBLIC KEY",
+		Bytes: asn1Bytes,
+	}
+
+	bytePrivate := pem.EncodeToMemory(privateKey)
+	bytePublic := pem.EncodeToMemory(publicKey)
+	return bytePrivate, bytePublic, nil
+}
-- 
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