chore(proxy): vendor a subset of rust-postgres (#9930)

Our rust-postgres fork is getting messy. Mostly because proxy wants more
control over the raw protocol than tokio-postgres provides. As such,
it's diverging more and more. Storage and compute also make use of
rust-postgres, but in more normal usage, thus they don't need our crazy
changes.

Idea: 
* proxy maintains their subset
* other teams use a minimal patch set against upstream rust-postgres

Reviewing this code will be difficult. To implement it, I
1. Copied tokio-postgres, postgres-protocol and postgres-types from
00940fcdb5
2. Updated their package names with the `2` suffix to make them compile
in the workspace.
3. Updated proxy to use those packages
4. Copied in the code from tokio-postgres-rustls 0.13 (with some patches
applied https://github.com/jbg/tokio-postgres-rustls/pull/32
https://github.com/jbg/tokio-postgres-rustls/pull/33)
5. Removed as much dead code as I could find in the vendored libraries
6. Updated the tokio-postgres-rustls code to use our existing channel
binding implementation

libs/proxy/postgres-protocol2/src/authentication/mod.rs

@@ -0,0 +1,37 @@
+//! Authentication protocol support.
+use md5::{Digest, Md5};
+
+pub mod sasl;
+
+/// Hashes authentication information in a way suitable for use in response
+/// to an `AuthenticationMd5Password` message.
+///
+/// The resulting string should be sent back to the database in a
+/// `PasswordMessage` message.
+#[inline]
+pub fn md5_hash(username: &[u8], password: &[u8], salt: [u8; 4]) -> String {
+    let mut md5 = Md5::new();
+    md5.update(password);
+    md5.update(username);
+    let output = md5.finalize_reset();
+    md5.update(format!("{:x}", output));
+    md5.update(salt);
+    format!("md5{:x}", md5.finalize())
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn md5() {
+        let username = b"md5_user";
+        let password = b"password";
+        let salt = [0x2a, 0x3d, 0x8f, 0xe0];
+
+        assert_eq!(
+            md5_hash(username, password, salt),
+            "md562af4dd09bbb41884907a838a3233294"
+        );
+    }
+}

libs/proxy/postgres-protocol2/src/authentication/sasl.rs

@@ -0,0 +1,516 @@
+//! SASL-based authentication support.
+
+use hmac::{Hmac, Mac};
+use rand::{self, Rng};
+use sha2::digest::FixedOutput;
+use sha2::{Digest, Sha256};
+use std::fmt::Write;
+use std::io;
+use std::iter;
+use std::mem;
+use std::str;
+use tokio::task::yield_now;
+
+const NONCE_LENGTH: usize = 24;
+
+/// The identifier of the SCRAM-SHA-256 SASL authentication mechanism.
+pub const SCRAM_SHA_256: &str = "SCRAM-SHA-256";
+/// The identifier of the SCRAM-SHA-256-PLUS SASL authentication mechanism.
+pub const SCRAM_SHA_256_PLUS: &str = "SCRAM-SHA-256-PLUS";
+
+// since postgres passwords are not required to exclude saslprep-prohibited
+// characters or even be valid UTF8, we run saslprep if possible and otherwise
+// return the raw password.
+fn normalize(pass: &[u8]) -> Vec<u8> {
+    let pass = match str::from_utf8(pass) {
+        Ok(pass) => pass,
+        Err(_) => return pass.to_vec(),
+    };
+
+    match stringprep::saslprep(pass) {
+        Ok(pass) => pass.into_owned().into_bytes(),
+        Err(_) => pass.as_bytes().to_vec(),
+    }
+}
+
+pub(crate) async fn hi(str: &[u8], salt: &[u8], iterations: u32) -> [u8; 32] {
+    let mut hmac =
+        Hmac::<Sha256>::new_from_slice(str).expect("HMAC is able to accept all key sizes");
+    hmac.update(salt);
+    hmac.update(&[0, 0, 0, 1]);
+    let mut prev = hmac.finalize().into_bytes();
+
+    let mut hi = prev;
+
+    for i in 1..iterations {
+        let mut hmac = Hmac::<Sha256>::new_from_slice(str).expect("already checked above");
+        hmac.update(&prev);
+        prev = hmac.finalize().into_bytes();
+
+        for (hi, prev) in hi.iter_mut().zip(prev) {
+            *hi ^= prev;
+        }
+        // yield every ~250us
+        // hopefully reduces tail latencies
+        if i % 1024 == 0 {
+            yield_now().await
+        }
+    }
+
+    hi.into()
+}
+
+enum ChannelBindingInner {
+    Unrequested,
+    Unsupported,
+    TlsServerEndPoint(Vec<u8>),
+}
+
+/// The channel binding configuration for a SCRAM authentication exchange.
+pub struct ChannelBinding(ChannelBindingInner);
+
+impl ChannelBinding {
+    /// The server did not request channel binding.
+    pub fn unrequested() -> ChannelBinding {
+        ChannelBinding(ChannelBindingInner::Unrequested)
+    }
+
+    /// The server requested channel binding but the client is unable to provide it.
+    pub fn unsupported() -> ChannelBinding {
+        ChannelBinding(ChannelBindingInner::Unsupported)
+    }
+
+    /// The server requested channel binding and the client will use the `tls-server-end-point`
+    /// method.
+    pub fn tls_server_end_point(signature: Vec<u8>) -> ChannelBinding {
+        ChannelBinding(ChannelBindingInner::TlsServerEndPoint(signature))
+    }
+
+    fn gs2_header(&self) -> &'static str {
+        match self.0 {
+            ChannelBindingInner::Unrequested => "y,,",
+            ChannelBindingInner::Unsupported => "n,,",
+            ChannelBindingInner::TlsServerEndPoint(_) => "p=tls-server-end-point,,",
+        }
+    }
+
+    fn cbind_data(&self) -> &[u8] {
+        match self.0 {
+            ChannelBindingInner::Unrequested | ChannelBindingInner::Unsupported => &[],
+            ChannelBindingInner::TlsServerEndPoint(ref buf) => buf,
+        }
+    }
+}
+
+/// A pair of keys for the SCRAM-SHA-256 mechanism.
+/// See <https://datatracker.ietf.org/doc/html/rfc5802#section-3> for details.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct ScramKeys<const N: usize> {
+    /// Used by server to authenticate client.
+    pub client_key: [u8; N],
+    /// Used by client to verify server's signature.
+    pub server_key: [u8; N],
+}
+
+/// Password or keys which were derived from it.
+enum Credentials<const N: usize> {
+    /// A regular password as a vector of bytes.
+    Password(Vec<u8>),
+    /// A precomputed pair of keys.
+    Keys(Box<ScramKeys<N>>),
+}
+
+enum State {
+    Update {
+        nonce: String,
+        password: Credentials<32>,
+        channel_binding: ChannelBinding,
+    },
+    Finish {
+        server_key: [u8; 32],
+        auth_message: String,
+    },
+    Done,
+}
+
+/// A type which handles the client side of the SCRAM-SHA-256/SCRAM-SHA-256-PLUS authentication
+/// process.
+///
+/// During the authentication process, if the backend sends an `AuthenticationSASL` message which
+/// includes `SCRAM-SHA-256` as an authentication mechanism, this type can be used.
+///
+/// After a `ScramSha256` is constructed, the buffer returned by the `message()` method should be
+/// sent to the backend in a `SASLInitialResponse` message along with the mechanism name.
+///
+/// The server will reply with an `AuthenticationSASLContinue` message. Its contents should be
+/// passed to the `update()` method, after which the buffer returned by the `message()` method
+/// should be sent to the backend in a `SASLResponse` message.
+///
+/// The server will reply with an `AuthenticationSASLFinal` message. Its contents should be passed
+/// to the `finish()` method, after which the authentication process is complete.
+pub struct ScramSha256 {
+    message: String,
+    state: State,
+}
+
+fn nonce() -> String {
+    // rand 0.5's ThreadRng is cryptographically secure
+    let mut rng = rand::thread_rng();
+    (0..NONCE_LENGTH)
+        .map(|_| {
+            let mut v = rng.gen_range(0x21u8..0x7e);
+            if v == 0x2c {
+                v = 0x7e
+            }
+            v as char
+        })
+        .collect()
+}
+
+impl ScramSha256 {
+    /// Constructs a new instance which will use the provided password for authentication.
+    pub fn new(password: &[u8], channel_binding: ChannelBinding) -> ScramSha256 {
+        let password = Credentials::Password(normalize(password));
+        ScramSha256::new_inner(password, channel_binding, nonce())
+    }
+
+    /// Constructs a new instance which will use the provided key pair for authentication.
+    pub fn new_with_keys(keys: ScramKeys<32>, channel_binding: ChannelBinding) -> ScramSha256 {
+        let password = Credentials::Keys(keys.into());
+        ScramSha256::new_inner(password, channel_binding, nonce())
+    }
+
+    fn new_inner(
+        password: Credentials<32>,
+        channel_binding: ChannelBinding,
+        nonce: String,
+    ) -> ScramSha256 {
+        ScramSha256 {
+            message: format!("{}n=,r={}", channel_binding.gs2_header(), nonce),
+            state: State::Update {
+                nonce,
+                password,
+                channel_binding,
+            },
+        }
+    }
+
+    /// Returns the message which should be sent to the backend in an `SASLResponse` message.
+    pub fn message(&self) -> &[u8] {
+        if let State::Done = self.state {
+            panic!("invalid SCRAM state");
+        }
+        self.message.as_bytes()
+    }
+
+    /// Updates the state machine with the response from the backend.
+    ///
+    /// This should be called when an `AuthenticationSASLContinue` message is received.
+    pub async fn update(&mut self, message: &[u8]) -> io::Result<()> {
+        let (client_nonce, password, channel_binding) =
+            match mem::replace(&mut self.state, State::Done) {
+                State::Update {
+                    nonce,
+                    password,
+                    channel_binding,
+                } => (nonce, password, channel_binding),
+                _ => return Err(io::Error::new(io::ErrorKind::Other, "invalid SCRAM state")),
+            };
+
+        let message =
+            str::from_utf8(message).map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
+
+        let parsed = Parser::new(message).server_first_message()?;
+
+        if !parsed.nonce.starts_with(&client_nonce) {
+            return Err(io::Error::new(io::ErrorKind::InvalidInput, "invalid nonce"));
+        }
+
+        let (client_key, server_key) = match password {
+            Credentials::Password(password) => {
+                let salt = match base64::decode(parsed.salt) {
+                    Ok(salt) => salt,
+                    Err(e) => return Err(io::Error::new(io::ErrorKind::InvalidInput, e)),
+                };
+
+                let salted_password = hi(&password, &salt, parsed.iteration_count).await;
+
+                let make_key = |name| {
+                    let mut hmac = Hmac::<Sha256>::new_from_slice(&salted_password)
+                        .expect("HMAC is able to accept all key sizes");
+                    hmac.update(name);
+
+                    let mut key = [0u8; 32];
+                    key.copy_from_slice(hmac.finalize().into_bytes().as_slice());
+                    key
+                };
+
+                (make_key(b"Client Key"), make_key(b"Server Key"))
+            }
+            Credentials::Keys(keys) => (keys.client_key, keys.server_key),
+        };
+
+        let mut hash = Sha256::default();
+        hash.update(client_key);
+        let stored_key = hash.finalize_fixed();
+
+        let mut cbind_input = vec![];
+        cbind_input.extend(channel_binding.gs2_header().as_bytes());
+        cbind_input.extend(channel_binding.cbind_data());
+        let cbind_input = base64::encode(&cbind_input);
+
+        self.message.clear();
+        write!(&mut self.message, "c={},r={}", cbind_input, parsed.nonce).unwrap();
+
+        let auth_message = format!("n=,r={},{},{}", client_nonce, message, self.message);
+
+        let mut hmac = Hmac::<Sha256>::new_from_slice(&stored_key)
+            .expect("HMAC is able to accept all key sizes");
+        hmac.update(auth_message.as_bytes());
+        let client_signature = hmac.finalize().into_bytes();
+
+        let mut client_proof = client_key;
+        for (proof, signature) in client_proof.iter_mut().zip(client_signature) {
+            *proof ^= signature;
+        }
+
+        write!(&mut self.message, ",p={}", base64::encode(client_proof)).unwrap();
+
+        self.state = State::Finish {
+            server_key,
+            auth_message,
+        };
+        Ok(())
+    }
+
+    /// Finalizes the authentication process.
+    ///
+    /// This should be called when the backend sends an `AuthenticationSASLFinal` message.
+    /// Authentication has only succeeded if this method returns `Ok(())`.
+    pub fn finish(&mut self, message: &[u8]) -> io::Result<()> {
+        let (server_key, auth_message) = match mem::replace(&mut self.state, State::Done) {
+            State::Finish {
+                server_key,
+                auth_message,
+            } => (server_key, auth_message),
+            _ => return Err(io::Error::new(io::ErrorKind::Other, "invalid SCRAM state")),
+        };
+
+        let message =
+            str::from_utf8(message).map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))?;
+
+        let parsed = Parser::new(message).server_final_message()?;
+
+        let verifier = match parsed {
+            ServerFinalMessage::Error(e) => {
+                return Err(io::Error::new(
+                    io::ErrorKind::Other,
+                    format!("SCRAM error: {}", e),
+                ));
+            }
+            ServerFinalMessage::Verifier(verifier) => verifier,
+        };
+
+        let verifier = match base64::decode(verifier) {
+            Ok(verifier) => verifier,
+            Err(e) => return Err(io::Error::new(io::ErrorKind::InvalidInput, e)),
+        };
+
+        let mut hmac = Hmac::<Sha256>::new_from_slice(&server_key)
+            .expect("HMAC is able to accept all key sizes");
+        hmac.update(auth_message.as_bytes());
+        hmac.verify_slice(&verifier)
+            .map_err(|_| io::Error::new(io::ErrorKind::InvalidInput, "SCRAM verification error"))
+    }
+}
+
+struct Parser<'a> {
+    s: &'a str,
+    it: iter::Peekable<str::CharIndices<'a>>,
+}
+
+impl<'a> Parser<'a> {
+    fn new(s: &'a str) -> Parser<'a> {
+        Parser {
+            s,
+            it: s.char_indices().peekable(),
+        }
+    }
+
+    fn eat(&mut self, target: char) -> io::Result<()> {
+        match self.it.next() {
+            Some((_, c)) if c == target => Ok(()),
+            Some((i, c)) => {
+                let m = format!(
+                    "unexpected character at byte {}: expected `{}` but got `{}",
+                    i, target, c
+                );
+                Err(io::Error::new(io::ErrorKind::InvalidInput, m))
+            }
+            None => Err(io::Error::new(
+                io::ErrorKind::UnexpectedEof,
+                "unexpected EOF",
+            )),
+        }
+    }
+
+    fn take_while<F>(&mut self, f: F) -> io::Result<&'a str>
+    where
+        F: Fn(char) -> bool,
+    {
+        let start = match self.it.peek() {
+            Some(&(i, _)) => i,
+            None => return Ok(""),
+        };
+
+        loop {
+            match self.it.peek() {
+                Some(&(_, c)) if f(c) => {
+                    self.it.next();
+                }
+                Some(&(i, _)) => return Ok(&self.s[start..i]),
+                None => return Ok(&self.s[start..]),
+            }
+        }
+    }
+
+    fn printable(&mut self) -> io::Result<&'a str> {
+        self.take_while(|c| matches!(c, '\x21'..='\x2b' | '\x2d'..='\x7e'))
+    }
+
+    fn nonce(&mut self) -> io::Result<&'a str> {
+        self.eat('r')?;
+        self.eat('=')?;
+        self.printable()
+    }
+
+    fn base64(&mut self) -> io::Result<&'a str> {
+        self.take_while(|c| matches!(c, 'a'..='z' | 'A'..='Z' | '0'..='9' | '/' | '+' | '='))
+    }
+
+    fn salt(&mut self) -> io::Result<&'a str> {
+        self.eat('s')?;
+        self.eat('=')?;
+        self.base64()
+    }
+
+    fn posit_number(&mut self) -> io::Result<u32> {
+        let n = self.take_while(|c| c.is_ascii_digit())?;
+        n.parse()
+            .map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))
+    }
+
+    fn iteration_count(&mut self) -> io::Result<u32> {
+        self.eat('i')?;
+        self.eat('=')?;
+        self.posit_number()
+    }
+
+    fn eof(&mut self) -> io::Result<()> {
+        match self.it.peek() {
+            Some(&(i, _)) => Err(io::Error::new(
+                io::ErrorKind::InvalidInput,
+                format!("unexpected trailing data at byte {}", i),
+            )),
+            None => Ok(()),
+        }
+    }
+
+    fn server_first_message(&mut self) -> io::Result<ServerFirstMessage<'a>> {
+        let nonce = self.nonce()?;
+        self.eat(',')?;
+        let salt = self.salt()?;
+        self.eat(',')?;
+        let iteration_count = self.iteration_count()?;
+        self.eof()?;
+
+        Ok(ServerFirstMessage {
+            nonce,
+            salt,
+            iteration_count,
+        })
+    }
+
+    fn value(&mut self) -> io::Result<&'a str> {
+        self.take_while(|c| matches!(c, '\0' | '=' | ','))
+    }
+
+    fn server_error(&mut self) -> io::Result<Option<&'a str>> {
+        match self.it.peek() {
+            Some(&(_, 'e')) => {}
+            _ => return Ok(None),
+        }
+
+        self.eat('e')?;
+        self.eat('=')?;
+        self.value().map(Some)
+    }
+
+    fn verifier(&mut self) -> io::Result<&'a str> {
+        self.eat('v')?;
+        self.eat('=')?;
+        self.base64()
+    }
+
+    fn server_final_message(&mut self) -> io::Result<ServerFinalMessage<'a>> {
+        let message = match self.server_error()? {
+            Some(error) => ServerFinalMessage::Error(error),
+            None => ServerFinalMessage::Verifier(self.verifier()?),
+        };
+        self.eof()?;
+        Ok(message)
+    }
+}
+
+struct ServerFirstMessage<'a> {
+    nonce: &'a str,
+    salt: &'a str,
+    iteration_count: u32,
+}
+
+enum ServerFinalMessage<'a> {
+    Error(&'a str),
+    Verifier(&'a str),
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn parse_server_first_message() {
+        let message = "r=fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j,s=QSXCR+Q6sek8bf92,i=4096";
+        let message = Parser::new(message).server_first_message().unwrap();
+        assert_eq!(message.nonce, "fyko+d2lbbFgONRv9qkxdawL3rfcNHYJY1ZVvWVs7j");
+        assert_eq!(message.salt, "QSXCR+Q6sek8bf92");
+        assert_eq!(message.iteration_count, 4096);
+    }
+
+    // recorded auth exchange from psql
+    #[tokio::test]
+    async fn exchange() {
+        let password = "foobar";
+        let nonce = "9IZ2O01zb9IgiIZ1WJ/zgpJB";
+
+        let client_first = "n,,n=,r=9IZ2O01zb9IgiIZ1WJ/zgpJB";
+        let server_first =
+            "r=9IZ2O01zb9IgiIZ1WJ/zgpJBjx/oIRLs02gGSHcw1KEty3eY,s=fs3IXBy7U7+IvVjZ,i\
+             =4096";
+        let client_final =
+            "c=biws,r=9IZ2O01zb9IgiIZ1WJ/zgpJBjx/oIRLs02gGSHcw1KEty3eY,p=AmNKosjJzS3\
+             1NTlQYNs5BTeQjdHdk7lOflDo5re2an8=";
+        let server_final = "v=U+ppxD5XUKtradnv8e2MkeupiA8FU87Sg8CXzXHDAzw=";
+
+        let mut scram = ScramSha256::new_inner(
+            Credentials::Password(normalize(password.as_bytes())),
+            ChannelBinding::unsupported(),
+            nonce.to_string(),
+        );
+        assert_eq!(str::from_utf8(scram.message()).unwrap(), client_first);
+
+        scram.update(server_first.as_bytes()).await.unwrap();
+        assert_eq!(str::from_utf8(scram.message()).unwrap(), client_final);
+
+        scram.finish(server_final.as_bytes()).unwrap();
+    }
+}