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              : pub use exchange::{exchange, Exchange};
      16              : pub use key::ScramKey;
      17              : pub use secret::ServerSecret;
      18              : 
      19              : use hmac::{Hmac, Mac};
      20              : use sha2::{Digest, Sha256};
      21              : 
      22              : const SCRAM_SHA_256: &str = "SCRAM-SHA-256";
      23              : const SCRAM_SHA_256_PLUS: &str = "SCRAM-SHA-256-PLUS";
      24              : 
      25              : /// A list of supported SCRAM methods.
      26              : pub const METHODS: &[&str] = &[SCRAM_SHA_256_PLUS, SCRAM_SHA_256];
      27              : pub const METHODS_WITHOUT_PLUS: &[&str] = &[SCRAM_SHA_256];
      28              : 
      29              : /// Decode base64 into array without any heap allocations
      30           88 : fn base64_decode_array<const N: usize>(input: impl AsRef<[u8]>) -> Option<[u8; N]> {
      31           88 :     let mut bytes = [0u8; N];
      32              : 
      33           88 :     let size = base64::decode_config_slice(input, base64::STANDARD, &mut bytes).ok()?;
      34           88 :     if size != N {
      35            0 :         return None;
      36           88 :     }
      37           88 : 
      38           88 :     Some(bytes)
      39           88 : }
      40              : 
      41              : /// This function essentially is `Hmac(sha256, key, input)`.
      42              : /// Further reading: <https://datatracker.ietf.org/doc/html/rfc2104>.
      43           32 : fn hmac_sha256<'a>(key: &[u8], parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
      44           32 :     let mut mac = Hmac::<Sha256>::new_from_slice(key).expect("bad key size");
      45          160 :     parts.into_iter().for_each(|s| mac.update(s));
      46           32 : 
      47           32 :     mac.finalize().into_bytes().into()
      48           32 : }
      49              : 
      50           32 : fn sha256<'a>(parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
      51           32 :     let mut hasher = Sha256::new();
      52           46 :     parts.into_iter().for_each(|s| hasher.update(s));
      53           32 : 
      54           32 :     hasher.finalize().into()
      55           32 : }
      56              : 
      57              : #[cfg(test)]
      58              : mod tests {
      59              :     use postgres_protocol::authentication::sasl::{ChannelBinding, ScramSha256};
      60              : 
      61              :     use crate::sasl::{Mechanism, Step};
      62              : 
      63              :     use super::{Exchange, ServerSecret};
      64              : 
      65            2 :     #[test]
      66            2 :     fn snapshot() {
      67            2 :         let iterations = 4096;
      68            2 :         let salt = "QSXCR+Q6sek8bf92";
      69            2 :         let stored_key = "FO+9jBb3MUukt6jJnzjPZOWc5ow/Pu6JtPyju0aqaE8=";
      70            2 :         let server_key = "qxJ1SbmSAi5EcS0J5Ck/cKAm/+Ixa+Kwp63f4OHDgzo=";
      71            2 :         let secret = format!("SCRAM-SHA-256${iterations}:{salt}${stored_key}:{server_key}",);
      72            2 :         let secret = ServerSecret::parse(&secret).unwrap();
      73            2 : 
      74            2 :         const NONCE: [u8; 18] = [
      75            2 :             1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
      76            2 :         ];
      77            2 :         let mut exchange = Exchange::new(
      78            2 :             &secret,
      79            2 :             || NONCE,
      80            2 :             crate::config::TlsServerEndPoint::Undefined,
      81            2 :         );
      82            2 : 
      83            2 :         let client_first = "n,,n=user,r=rOprNGfwEbeRWgbNEkqO";
      84            2 :         let client_final = "c=biws,r=rOprNGfwEbeRWgbNEkqOAQIDBAUGBwgJCgsMDQ4PEBES,p=rw1r5Kph5ThxmaUBC2GAQ6MfXbPnNkFiTIvdb/Rear0=";
      85            2 :         let server_first =
      86            2 :             "r=rOprNGfwEbeRWgbNEkqOAQIDBAUGBwgJCgsMDQ4PEBES,s=QSXCR+Q6sek8bf92,i=4096";
      87            2 :         let server_final = "v=qtUDIofVnIhM7tKn93EQUUt5vgMOldcDVu1HC+OH0o0=";
      88              : 
      89            2 :         exchange = match exchange.exchange(client_first).unwrap() {
      90            2 :             Step::Continue(exchange, message) => {
      91            2 :                 assert_eq!(message, server_first);
      92            2 :                 exchange
      93              :             }
      94            0 :             Step::Success(_, _) => panic!("expected continue, got success"),
      95            0 :             Step::Failure(f) => panic!("{f}"),
      96              :         };
      97              : 
      98            2 :         let key = match exchange.exchange(client_final).unwrap() {
      99            2 :             Step::Success(key, message) => {
     100            2 :                 assert_eq!(message, server_final);
     101            2 :                 key
     102              :             }
     103            0 :             Step::Continue(_, _) => panic!("expected success, got continue"),
     104            0 :             Step::Failure(f) => panic!("{f}"),
     105              :         };
     106              : 
     107            2 :         assert_eq!(
     108            2 :             key.as_bytes(),
     109            2 :             [
     110            2 :                 74, 103, 1, 132, 12, 31, 200, 48, 28, 54, 82, 232, 207, 12, 138, 189, 40, 32, 134,
     111            2 :                 27, 125, 170, 232, 35, 171, 167, 166, 41, 70, 228, 182, 112,
     112            2 :             ]
     113            2 :         );
     114            2 :     }
     115              : 
     116            4 :     fn run_round_trip_test(server_password: &str, client_password: &str) {
     117            4 :         let scram_secret = ServerSecret::build(server_password).unwrap();
     118            4 :         let sasl_client =
     119            4 :             ScramSha256::new(client_password.as_bytes(), ChannelBinding::unsupported());
     120            4 : 
     121            4 :         let outcome = super::exchange(
     122            4 :             &scram_secret,
     123            4 :             sasl_client,
     124            4 :             crate::config::TlsServerEndPoint::Undefined,
     125            4 :         )
     126            4 :         .unwrap();
     127            4 : 
     128            4 :         match outcome {
     129            2 :             crate::sasl::Outcome::Success(_) => {}
     130            2 :             crate::sasl::Outcome::Failure(r) => panic!("{r}"),
     131              :         }
     132            2 :     }
     133              : 
     134            2 :     #[test]
     135            2 :     fn round_trip() {
     136            2 :         run_round_trip_test("pencil", "pencil")
     137            2 :     }
     138              : 
     139            2 :     #[test]
     140              :     #[should_panic(expected = "password doesn't match")]
     141            2 :     fn failure() {
     142            2 :         run_round_trip_test("pencil", "eraser")
     143            2 :     }
     144              : }