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opensend/keyCrypto.go

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2020-12-03 10:12:43 +00:00
package main
import (
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"github.com/rs/zerolog"
"github.com/rs/zerolog/log"
"io/ioutil"
"net/http"
"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(senderAddr string) []byte {
// Use ConsoleWriter logger
log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr}).Hook(FatalHook{})
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// Get server address by getting the IP without the port, prepending http:// and appending :9898
serverAddr := "http://" + strings.Split(senderAddr, ":")[0] + ":9898"
// GET /key on the sender's HTTP server
response, err := http.Get(serverAddr + "/key")
if err != nil { log.Fatal().Err(err).Msg("Error getting key") }
// Close response body at the end of this function
defer response.Body.Close()
// If server responded with 200 OK
if response.StatusCode == http.StatusOK {
// Read response body into key
key, err := ioutil.ReadAll(response.Body)
if err != nil { log.Fatal().Err(err).Msg("Error reading HTTP response") }
// Return key
return key
// Otherwise
} else {
// Fatally log status code
if err != nil { log.Fatal().Int("code", response.StatusCode).Msg("HTTP Error Response Code Received") }
}
// 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
}