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, Exchange};
      19              : pub use key::ScramKey;
      20              : pub use secret::ServerSecret;
      21              : 
      22              : use hmac::{Hmac, Mac};
      23              : use sha2::{Digest, Sha256};
      24              : 
      25              : const SCRAM_SHA_256: &str = "SCRAM-SHA-256";
      26              : const SCRAM_SHA_256_PLUS: &str = "SCRAM-SHA-256-PLUS";
      27              : 
      28              : /// A list of supported SCRAM methods.
      29              : pub const METHODS: &[&str] = &[SCRAM_SHA_256_PLUS, SCRAM_SHA_256];
      30              : pub const METHODS_WITHOUT_PLUS: &[&str] = &[SCRAM_SHA_256];
      31              : 
      32              : /// Decode base64 into array without any heap allocations
      33          462 : fn base64_decode_array<const N: usize>(input: impl AsRef<[u8]>) -> Option<[u8; N]> {
      34          462 :     let mut bytes = [0u8; N];
      35              : 
      36          462 :     let size = base64::decode_config_slice(input, base64::STANDARD, &mut bytes).ok()?;
      37          462 :     if size != N {
      38            0 :         return None;
      39          462 :     }
      40          462 : 
      41          462 :     Some(bytes)
      42          462 : }
      43              : 
      44              : /// This function essentially is `Hmac(sha256, key, input)`.
      45              : /// Further reading: <https://datatracker.ietf.org/doc/html/rfc2104>.
      46         8438 : fn hmac_sha256<'a>(key: &[u8], parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
      47         8438 :     let mut mac = Hmac::<Sha256>::new_from_slice(key).expect("bad key size");
      48         9216 :     parts.into_iter().for_each(|s| mac.update(s));
      49         8438 : 
      50         8438 :     mac.finalize().into_bytes().into()
      51         8438 : }
      52              : 
      53          141 : fn sha256<'a>(parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
      54          141 :     let mut hasher = Sha256::new();
      55          156 :     parts.into_iter().for_each(|s| hasher.update(s));
      56          141 : 
      57          141 :     hasher.finalize().into()
      58          141 : }
      59              : 
      60              : #[cfg(test)]
      61              : mod tests {
      62              :     use crate::sasl::{Mechanism, Step};
      63              : 
      64              :     use super::{password::SaltedPassword, Exchange, ServerSecret};
      65              : 
      66            2 :     #[test]
      67            2 :     fn happy_path() {
      68            2 :         let iterations = 4096;
      69            2 :         let salt_base64 = "QSXCR+Q6sek8bf92";
      70            2 :         let pw = SaltedPassword::new(
      71            2 :             b"pencil",
      72            2 :             base64::decode(salt_base64).unwrap().as_slice(),
      73            2 :             iterations,
      74            2 :         );
      75            2 : 
      76            2 :         let secret = ServerSecret {
      77            2 :             iterations,
      78            2 :             salt_base64: salt_base64.to_owned(),
      79            2 :             stored_key: pw.client_key().sha256(),
      80            2 :             server_key: pw.server_key(),
      81            2 :             doomed: false,
      82            2 :         };
      83            2 :         const NONCE: [u8; 18] = [
      84            2 :             1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
      85            2 :         ];
      86            2 :         let mut exchange = Exchange::new(
      87            2 :             &secret,
      88            2 :             || NONCE,
      89            2 :             crate::config::TlsServerEndPoint::Undefined,
      90            2 :         );
      91            2 : 
      92            2 :         let client_first = "n,,n=user,r=rOprNGfwEbeRWgbNEkqO";
      93            2 :         let client_final = "c=biws,r=rOprNGfwEbeRWgbNEkqOAQIDBAUGBwgJCgsMDQ4PEBES,p=rw1r5Kph5ThxmaUBC2GAQ6MfXbPnNkFiTIvdb/Rear0=";
      94            2 :         let server_first =
      95            2 :             "r=rOprNGfwEbeRWgbNEkqOAQIDBAUGBwgJCgsMDQ4PEBES,s=QSXCR+Q6sek8bf92,i=4096";
      96            2 :         let server_final = "v=qtUDIofVnIhM7tKn93EQUUt5vgMOldcDVu1HC+OH0o0=";
      97              : 
      98            2 :         exchange = match exchange.exchange(client_first).unwrap() {
      99            2 :             Step::Continue(exchange, message) => {
     100            2 :                 assert_eq!(message, server_first);
     101            2 :                 exchange
     102              :             }
     103            0 :             Step::Success(_, _) => panic!("expected continue, got success"),
     104            0 :             Step::Failure(f) => panic!("{f}"),
     105              :         };
     106              : 
     107            2 :         let key = match exchange.exchange(client_final).unwrap() {
     108            2 :             Step::Success(key, message) => {
     109            2 :                 assert_eq!(message, server_final);
     110            2 :                 key
     111              :             }
     112            0 :             Step::Continue(_, _) => panic!("expected success, got continue"),
     113            0 :             Step::Failure(f) => panic!("{f}"),
     114              :         };
     115              : 
     116            2 :         assert_eq!(
     117            2 :             key.as_bytes(),
     118            2 :             [
     119            2 :                 74, 103, 1, 132, 12, 31, 200, 48, 28, 54, 82, 232, 207, 12, 138, 189, 40, 32, 134,
     120            2 :                 27, 125, 170, 232, 35, 171, 167, 166, 41, 70, 228, 182, 112,
     121            2 :             ]
     122            2 :         );
     123            2 :     }
     124              : }