Correctly pad bytes with zero in hex conversion

When reading a secret in ascii or base32 format from the user, we
perform a conversion of the potentially decoded string into hexadecimal
bytes, because that is what libnitrokey expects.
The format string we used in the conversion, however, did not account
for padding with a leading zero for single digit results. E.g., the
newline/line feed symbol '\n', which has a decimal value of 10 would
result in the string 'a' being produced, whereas '0a' would be the
correct result.
This change corrects the format string to fix this problem.

nitrocli/CHANGELOG.md

@@ -7,6 +7,7 @@ Unreleased
 - Removed `storage status` subcommand
  - Moved its output into `status` command
 - Removed previously deprecated `--ascii` option from `otp set` command
+- Fixed wrong hexadecimal conversion used in `otp set` command
 - Bumped `libc` dependency to `0.2.62`
 - Bumped `cc` dependency to `1.0.40`
 

nitrocli/src/commands.rs

@@ -616,7 +616,7 @@ pub fn otp_get(
 fn format_bytes(bytes: &[u8]) -> String {
  bytes
  .iter()
- .map(|c| format!("{:x}", c))
+ .map(|c| format!("{:02x}", c))
  .collect::<Vec<_>>()
  .join("")
 }
@@ -956,4 +956,11 @@ mod tests {
  let result = prepare_ascii_secret("Österreich");
  assert!(result.is_err());
  }
+
+ #[test]
+ fn hex_string() {
+ assert_eq!(format_bytes(&[b' ']), "20");
+ assert_eq!(format_bytes(&[b' ', b' ']), "2020");
+ assert_eq!(format_bytes(&[b'\n', b'\n']), "0a0a");
+ }
 }