[Feature request] Clearer message when attr("nonce") is missing

[ColinFay]

Hey,

Thanks a lot for sodium :)

I've been working on a tool that need to encrypt / decrypt data that are sent through http calls to a plumber API and stumble upon something that took me a little while to debug: when trying to decrypt a message, if you don't have attr("nonce"), the function will fail.

library(sodium)
key <- sha256(charToRaw("xyz"))
msg <- charToRaw("secretthing")

cipher <- data_encrypt(msg, key)
cipher
 [1] f6 d6 29 a5 5a c5 ed cd 31 6b cf 4b 19 19 3b 4f 56 9c b7 02 19 02 88 2c bd
[26] e2 14
attr(,"nonce")
 [1] 31 d6 f6 51 90 c7 6b 3a 70 e3 cc 14 94 c3 b5 a1 bf d9 d6 a8 87 0f 44 4e

# works as expected
data_decrypt(cipher, key) |> rawToChar()
[1] "secretthing"

# as I want to sent it via http, I use bin2hex
message_to_send <- bin2hex(cipher)
message_to_send
[1] "f6d629a55ac5edcd316bcf4b19193b4f569cb7021902882cbde214"

# on the other process, I receive a string that 
# I want to decrypt
message_received <- hex2bin(message_to_send)
message_received
 [1] f6 d6 29 a5 5a c5 ed cd 31 6b cf 4b 19 19 3b 4f 56 9c b7 02 19 02 88 2c bd
[26] e2 14

orig <- data_decrypt(message_received, key)
Error in data_decrypt(message_received, key) : 
  Invalid key. Key must be exactly 24 bytes

The error message here is pretty unclear because I haven't touched the key object and I don't understand why it's suddenly not the correct length, and so I spent some time trying to understand this length issue.

The issue here seem to be that the message_received doesn't have a nonce attribute :

attr(message_received, "nonce") <- attr(cipher, "nonce")
orig <- data_decrypt(message_received, key)
orig
 [1] 73 65 63 72 65 74 74 68 69 6e 67

Given that nonce in data_decrypt is attr(bin, "nonce") and that you can't encrypt with NULL (data_encrypt(msg, key, NULL) throws an error), my feature request would be that there should be a clear error message in data_decrypt if nonce is NULL.

[jeroen]

Yes that makes sense; can you send a PR?

[ColinFay]

Sure!