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opensend/keyCrypto.go

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package main
import (
"bufio"
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"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"encoding/hex"
"fmt"
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"github.com/rs/zerolog"
"github.com/rs/zerolog/log"
"net"
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"os"
"strings"
)
// Generate RSA keypair
func GenerateRSAKeypair() (*rsa.PrivateKey, *rsa.PublicKey) {
// Use ConsoleWriter logger
log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr}).Hook(FatalHook{})
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// Generate private/public RSA keypair
privateKey, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil { log.Fatal().Err(err).Msg("Error generating RSA keypair") }
// Get public key
publicKey := privateKey.PublicKey
// Return keypair
return privateKey, &publicKey
}
// Get public key from sender
func GetKey(connection net.Conn) []byte {
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// Use ConsoleWriter logger
log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr}).Hook(FatalHook{})
// Send key request to connection
_, err := fmt.Fprintln(connection, "key;")
if err != nil { log.Fatal().Err(err).Msg("Error sending key request") }
// Read received message
message, err := bufio.NewReader(connection).ReadString('\n')
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if err != nil { log.Fatal().Err(err).Msg("Error getting key") }
// Process received message
procMessage := strings.Split(strings.TrimSpace(message), ";")
// If ok code returned
if procMessage[0] == "OK" {
// Decode received hex string into key
key, err := hex.DecodeString(procMessage[1])
if err != nil { log.Fatal().Err(err).Msg("Error reading key") }
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// Return key
return key
// Otherwise
} else {
// Fatally log
if err != nil { log.Fatal().Msg("Server reported error") }
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}
// Return nil if all else fails
return nil
}
// Encrypt shared key with received public key
func EncryptKey(sharedKey string, recvPubKey *rsa.PublicKey) []byte {
// Use ConsoleWriter logger
log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr}).Hook(FatalHook{})
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// Encrypt shared key using RSA
encryptedSharedKey, err := rsa.EncryptOAEP(sha256.New(), rand.Reader, recvPubKey, []byte(sharedKey), nil)
if err != nil { log.Fatal().Err(err).Msg("Error encrypting shared key") }
// Return encrypted key
return encryptedSharedKey
}
// Decrypt shared key using private RSA key
func DecryptKey(encryptedKey []byte, privateKey *rsa.PrivateKey) string {
// Decrypt shared key using RSA
decryptedKey, err := rsa.DecryptOAEP(sha256.New(), rand.Reader, privateKey, encryptedKey, nil)
if err != nil { log.Fatal().Err(err).Msg("Error decrypting shared key") }
// Get string of decrypted key
sharedKey := string(decryptedKey)
// Return shared key
return sharedKey
}