proxy: use postgres_protocol scram/sasl code (#4748)

1) `scram::password` was used in tests only. can be replaced with
`postgres_protocol::password`.
2) `postgres_protocol::authentication::sasl` provides a client impl of
SASL which improves our ability to test

proxy/src/proxy/tests.rs

@@ -132,9 +132,8 @@ struct Scram(scram::ServerSecret);
 
 impl Scram {
     fn new(password: &str) -> anyhow::Result<Self> {
-        let salt = rand::random::<[u8; 16]>();
-        let secret = scram::ServerSecret::build(password, &salt, 256)
-            .context("failed to generate scram secret")?;
+        let secret =
+            scram::ServerSecret::build(password).context("failed to generate scram secret")?;
         Ok(Scram(secret))
     }
 

proxy/src/scram.rs

@@ -12,9 +12,6 @@ mod messages;
 mod secret;
 mod signature;
 
-#[cfg(any(test, doc))]
-mod password;
-
 pub use exchange::{exchange, Exchange};
 pub use key::ScramKey;
 pub use secret::ServerSecret;
@@ -59,27 +56,21 @@ fn sha256<'a>(parts: impl IntoIterator<Item = &'a [u8]>) -> [u8; 32] {
 
 #[cfg(test)]
 mod tests {
+    use postgres_protocol::authentication::sasl::{ChannelBinding, ScramSha256};
+
     use crate::sasl::{Mechanism, Step};
 
-    use super::{password::SaltedPassword, Exchange, ServerSecret};
+    use super::{Exchange, ServerSecret};
 
     #[test]
-    fn happy_path() {
+    fn snapshot() {
         let iterations = 4096;
-        let salt_base64 = "QSXCR+Q6sek8bf92";
-        let pw = SaltedPassword::new(
-            b"pencil",
-            base64::decode(salt_base64).unwrap().as_slice(),
-            iterations,
-        );
+        let salt = "QSXCR+Q6sek8bf92";
+        let stored_key = "FO+9jBb3MUukt6jJnzjPZOWc5ow/Pu6JtPyju0aqaE8=";
+        let server_key = "qxJ1SbmSAi5EcS0J5Ck/cKAm/+Ixa+Kwp63f4OHDgzo=";
+        let secret = format!("SCRAM-SHA-256${iterations}:{salt}${stored_key}:{server_key}",);
+        let secret = ServerSecret::parse(&secret).unwrap();
 
-        let secret = ServerSecret {
-            iterations,
-            salt_base64: salt_base64.to_owned(),
-            stored_key: pw.client_key().sha256(),
-            server_key: pw.server_key(),
-            doomed: false,
-        };
         const NONCE: [u8; 18] = [
             1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
         ];
@@ -121,4 +112,33 @@ mod tests {
             ]
         );
     }
+
+    fn run_round_trip_test(server_password: &str, client_password: &str) {
+        let scram_secret = ServerSecret::build(server_password).unwrap();
+        let sasl_client =
+            ScramSha256::new(client_password.as_bytes(), ChannelBinding::unsupported());
+
+        let outcome = super::exchange(
+            &scram_secret,
+            sasl_client,
+            crate::config::TlsServerEndPoint::Undefined,
+        )
+        .unwrap();
+
+        match outcome {
+            crate::sasl::Outcome::Success(_) => {}
+            crate::sasl::Outcome::Failure(r) => panic!("{r}"),
+        }
+    }
+
+    #[test]
+    fn round_trip() {
+        run_round_trip_test("pencil", "pencil")
+    }
+
+    #[test]
+    #[should_panic(expected = "password doesn't match")]
+    fn failure() {
+        run_round_trip_test("pencil", "eraser")
+    }
 }

proxy/src/scram/key.rs

@@ -3,7 +3,7 @@
 /// Faithfully taken from PostgreSQL.
 pub const SCRAM_KEY_LEN: usize = 32;
 
-/// One of the keys derived from the [password](super::password::SaltedPassword).
+/// One of the keys derived from the user's password.
 /// We use the same structure for all keys, i.e.
 /// `ClientKey`, `StoredKey`, and `ServerKey`.
 #[derive(Clone, Default, PartialEq, Eq, Debug)]

proxy/src/scram/secret.rs

@@ -3,7 +3,7 @@
 use super::base64_decode_array;
 use super::key::ScramKey;
 
-/// Server secret is produced from [password](super::password::SaltedPassword)
+/// Server secret is produced from user's password,
 /// and is used throughout the authentication process.
 #[derive(Clone, Eq, PartialEq, Debug)]
 pub struct ServerSecret {
@@ -59,21 +59,10 @@ impl ServerSecret {
     /// Build a new server secret from the prerequisites.
     /// XXX: We only use this function in tests.
     #[cfg(test)]
-    pub fn build(password: &str, salt: &[u8], iterations: u32) -> Option<Self> {
-        // TODO: implement proper password normalization required by the RFC
-        if !password.is_ascii() {
-            return None;
-        }
-
-        let password = super::password::SaltedPassword::new(password.as_bytes(), salt, iterations);
-
-        Some(Self {
-            iterations,
-            salt_base64: base64::encode(salt),
-            stored_key: password.client_key().sha256(),
-            server_key: password.server_key(),
-            doomed: false,
-        })
+    pub fn build(password: &str) -> Option<Self> {
+        Self::parse(&postgres_protocol::password::scram_sha_256(
+            password.as_bytes(),
+        ))
     }
 }
 
@@ -103,20 +92,4 @@ mod tests {
         assert_eq!(base64::encode(parsed.stored_key), stored_key);
         assert_eq!(base64::encode(parsed.server_key), server_key);
     }
-
-    #[test]
-    fn build_scram_secret() {
-        let salt = b"salt";
-        let secret = ServerSecret::build("password", salt, 4096).unwrap();
-        assert_eq!(secret.iterations, 4096);
-        assert_eq!(secret.salt_base64, base64::encode(salt));
-        assert_eq!(
-            base64::encode(secret.stored_key.as_ref()),
-            "lF4cRm/Jky763CN4HtxdHnjV4Q8AWTNlKvGmEFFU8IQ="
-        );
-        assert_eq!(
-            base64::encode(secret.server_key.as_ref()),
-            "ub8OgRsftnk2ccDMOt7ffHXNcikRkQkq1lh4xaAqrSw="
-        );
-    }
 }