TLA  Line data    Source code

       1                 : //! Salted Challenge Response Authentication Mechanism.
       2                 : //!
       3                 : //! RFC: <https://datatracker.ietf.org/doc/html/rfc5802>.
       4                 : //!
       5                 : //! Reference implementation:
       6                 : //! * <https://github.com/postgres/postgres/blob/94226d4506e66d6e7cbf4b391f1e7393c1962841/src/backend/libpq/auth-scram.c>
       7                 : //! * <https://github.com/postgres/postgres/blob/94226d4506e66d6e7cbf4b391f1e7393c1962841/src/interfaces/libpq/fe-auth-scram.c>
       8                 : 
       9                 : mod exchange;
      10                 : mod key;
      11                 : mod messages;
      12                 : mod secret;
      13                 : mod signature;
      14                 : 
      15                 : #[cfg(any(test, doc))]
      16                 : mod password;
      17                 : 
      18                 : pub use exchange::Exchange;
      19                 : pub use key::ScramKey;
      20                 : pub use secret::ServerSecret;
      21                 : pub use secret::*;
      22                 : 
      23                 : use hmac::{Hmac, Mac};
      24                 : use sha2::{Digest, Sha256};
      25                 : 
      26                 : // TODO: add SCRAM-SHA-256-PLUS
      27                 : /// A list of supported SCRAM methods.
      28                 : pub const METHODS: &[&str] = &["SCRAM-SHA-256"];
      29                 : 
      30                 : /// Decode base64 into array without any heap allocations
      31 CBC          87 : fn base64_decode_array<const N: usize>(input: impl AsRef<[u8]>) -> Option<[u8; N]> {
      32              87 :     let mut bytes = [0u8; N];
      33                 : 
      34              87 :     let size = base64::decode_config_slice(input, base64::STANDARD, &mut bytes).ok()?;
      35              87 :     if size != N {
      36 UBC           0 :         return None;
      37 CBC          87 :     }
      38              87 : 
      39              87 :     Some(bytes)
      40              87 : }
      41                 : 
      42                 : /// This function essentially is `Hmac(sha256, key, input)`.
      43                 : /// Further reading: <https://datatracker.ietf.org/doc/html/rfc2104>.
      44            4166 : fn hmac_sha256<'a>(key: &[u8], parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
      45            4166 :     let mut mac = Hmac::<Sha256>::new_from_slice(key).expect("bad key size");
      46            4407 :     parts.into_iter().for_each(|s| mac.update(s));
      47            4166 : 
      48            4166 :     mac.finalize().into_bytes().into()
      49            4166 : }
      50                 : 
      51              39 : fn sha256<'a>(parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
      52              39 :     let mut hasher = Sha256::new();
      53              41 :     parts.into_iter().for_each(|s| hasher.update(s));
      54              39 : 
      55              39 :     hasher.finalize().into()
      56              39 : }
      57                 : 
      58                 : #[cfg(test)]
      59                 : mod tests {
      60                 :     use crate::sasl::{Mechanism, Step};
      61                 : 
      62                 :     use super::{password::SaltedPassword, Exchange, ServerSecret};
      63                 : 
      64               1 :     #[test]
      65               1 :     fn happy_path() {
      66               1 :         let iterations = 4096;
      67               1 :         let salt_base64 = "QSXCR+Q6sek8bf92";
      68               1 :         let pw = SaltedPassword::new(
      69               1 :             b"pencil",
      70               1 :             base64::decode(salt_base64).unwrap().as_slice(),
      71               1 :             iterations,
      72               1 :         );
      73               1 : 
      74               1 :         let secret = ServerSecret {
      75               1 :             iterations,
      76               1 :             salt_base64: salt_base64.to_owned(),
      77               1 :             stored_key: pw.client_key().sha256(),
      78               1 :             server_key: pw.server_key(),
      79               1 :             doomed: false,
      80               1 :         };
      81               1 :         const NONCE: [u8; 18] = [
      82               1 :             1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
      83               1 :         ];
      84               1 :         let mut exchange = Exchange::new(&secret, || NONCE, None);
      85               1 : 
      86               1 :         let client_first = "n,,n=user,r=rOprNGfwEbeRWgbNEkqO";
      87               1 :         let client_final = "c=biws,r=rOprNGfwEbeRWgbNEkqOAQIDBAUGBwgJCgsMDQ4PEBES,p=rw1r5Kph5ThxmaUBC2GAQ6MfXbPnNkFiTIvdb/Rear0=";
      88               1 :         let server_first =
      89               1 :             "r=rOprNGfwEbeRWgbNEkqOAQIDBAUGBwgJCgsMDQ4PEBES,s=QSXCR+Q6sek8bf92,i=4096";
      90               1 :         let server_final = "v=qtUDIofVnIhM7tKn93EQUUt5vgMOldcDVu1HC+OH0o0=";
      91                 : 
      92               1 :         exchange = match exchange.exchange(client_first).unwrap() {
      93               1 :             Step::Continue(exchange, message) => {
      94               1 :                 assert_eq!(message, server_first);
      95               1 :                 exchange
      96                 :             }
      97 UBC           0 :             Step::Success(_, _) => panic!("expected continue, got success"),
      98               0 :             Step::Failure(f) => panic!("{f}"),
      99                 :         };
     100                 : 
     101 CBC           1 :         let key = match exchange.exchange(client_final).unwrap() {
     102               1 :             Step::Success(key, message) => {
     103               1 :                 assert_eq!(message, server_final);
     104               1 :                 key
     105                 :             }
     106 UBC           0 :             Step::Continue(_, _) => panic!("expected success, got continue"),
     107               0 :             Step::Failure(f) => panic!("{f}"),
     108                 :         };
     109                 : 
     110 CBC           1 :         assert_eq!(
     111               1 :             key.as_bytes(),
     112               1 :             [
     113               1 :                 74, 103, 1, 132, 12, 31, 200, 48, 28, 54, 82, 232, 207, 12, 138, 189, 40, 32, 134,
     114               1 :                 27, 125, 170, 232, 35, 171, 167, 166, 41, 70, 228, 182, 112,
     115               1 :             ]
     116               1 :         );
     117               1 :     }
     118                 : }