send and read a [] byte between two microservices golang - json

Question

I have a data encryption function that returns a [] byte. Of course, what has been encrypted must be decrypted (through another function) in another micro-service.
The problem is created when I send the []byte via JSON: the []byte is transformed into a string and then when I go to read the JSON through the call, the result is no longer the same.
I have to be able to pass the original []byte, created by the encryption function, through JSON or otherwise pass the []byte through a call like the one you can see below. Another possibility is to change the decryption function, but I have not succeeded.
caller function
func Dati_mono(c *gin.Context) {
id := c.Param("id")
oracle, err := http.Get("http://XXXX/"+id)
if err != nil {
panic(err)
}
defer oracle.Body.Close()
oJSON, err := ioutil.ReadAll(oracle.Body)
if err != nil {
panic(err)
}
oracleJSON := security.Decrypt(oJSON, keyEn)
c.JSON(http.StatusOK, string(oJSON))
}
function that is called with the url
func Dati(c *gin.Context) {
var (
person Person
result mapstring.Dati_Plus
mmap []map[string]interface{}
)
rows, err := db.DBConor.Query("SELECT COD_DIPENDENTE, MATRICOLA, COGNOME FROM ANDIP021_K")
if err != nil {
fmt.Print(err.Error())
}
for rows.Next() {
err = rows.Scan(&person.COD_DIPENDENTE, &person.MATRICOLA, &person.COGNOME)
ciao := structs.Map(&person)
mmap = append(mmap, ciao)
}
defer rows.Close()
result = mapstring.Dati_Plus{
len(mmap),
mmap,
}
jsonEn := []byte(mapstring.Dati_PlustoStr(result))
keyEn := []byte(key)
cipherjson, err := security.Encrypt(jsonEn, keyEn)
if err != nil {
log.Fatal(err)
}
c.JSON(http.StatusOK, cipherjson)
}
encryption and decryption functions
func Encrypt(json []byte, key []byte) (string, error) {
k, err := aes.NewCipher(key)
if err != nil {
return "nil", err
}
gcm, err := cipher.NewGCM(k)
if err != nil {
return "nil", err
}
nonce := make([]byte, gcm.NonceSize())
if _, err = io.ReadFull(rand.Reader, nonce); err != nil {
return "nil", err
}
return gcm.Seal(nonce, nonce, json, nil), nil
}
func Decrypt(cipherjson []byte, key []byte) ([]byte, error) {
k, err := aes.NewCipher(key)
if err != nil {
return nil, err
}
gcm, err := cipher.NewGCM(k)
if err != nil {
return nil, err
}
nonceSize := gcm.NonceSize()
if len(cipherjson) < nonceSize {
return nil, errors.New("cipherjson too short")
}
nonce, cipherjson := cipherjson[:nonceSize], cipherjson[nonceSize:]
return gcm.Open(nil, nonce, cipherjson, nil)
}
Everything works, the problem is created when I print cipherjson in c.JSON (): the []byte is translated into a string.
At the time it is taken and read by the calling function it is read as string and ioutil.ReadAll () creates the [] byte of the read string.
Instead I must be able to pass to the Decryot function the return of the Encrypt function used in the called function.
I hope I was clear, thanks in advance

Answer 1

You are not decoding the response before decrypting. In other words, you are handing the JSON encoding of the ciphertext to Decrypt. That is obviously not going to do what you want. To recover the plaintext you have to precisely undo all of the operations of the encryption and encoding in reverse order.
Either decode before decrypting, or don't JSON encode on the server. For instance:
oJSON, err := ioutil.ReadAll(oracle.Body)
if err != nil {
panic(err)
}
var ciphertext string
if err := json.Unmarshal(oJSON, &ciphertext); err != nil {
// TODO: handle error
}
oracleJSON := security.Decrypt(ciphertext, keyEn)
Although it is unclear why you even go through the trouble of JSON encoding in the first place. You might as well just write the ciphertext directly. If you really want to encode the ciphertext, you should not convert it to a string. The ciphertext is just a bunch of random bytes, not remotely resembling a UTF-8 encoded string, so don't treat it like one. encoding/json uses the base64 encoding for byte slices automatically, which is a much cleaner (and probably shorter) representation of the ciphertext than tons of unicode escape sequences.
Independent of the encoding you choose (if any), your Encrypt function is broken.
// The plaintext and dst must overlap exactly or not at all. To reuse
// plaintext's storage for the encrypted output, use plaintext[:0] as dst.
Seal(dst, nonce, plaintext, additionalData []byte) []byte
The first argument is the destination for the encryption. If you don't need to retain the plaintext, pass json[:0]; otherwise pass nil.
Also, Decrypt expects the ciphertext to be prefixed by the nonce, but Encrypt doesn't prepend it.