feat: Implement LDAP bind/whoami

Cargo.lock

@@ -63,6 +63,10 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
+[[package]]
+name = "dn_escape"
+version = "0.1.0"
+
 [[package]]
 name = "futures-core"
 version = "0.3.34"
@@ -100,6 +104,7 @@ checksum = "0d50a92467f8ba5dd6e3ee5d4bd04d73ab2e4e1c44474a0674821dfce14b79bc"
 dependencies = [
  "futures-core",
  "futures-macro",
+ "futures-sink",
  "futures-task",
  "pin-project-lite",
  "slab",
@@ -172,6 +177,7 @@ version = "0.1.0"
 dependencies = [
  "argh",
  "camino",
+ "dn_escape",
  "futures-util",
  "ldap3_proto",
  "serde",

Cargo.toml

@@ -6,7 +6,8 @@ edition = "2024"
 [dependencies]
 argh = "0.1.19"
 camino = "1.2.5"
-futures-util = "0.3.34"
+dn_escape = { path = "vendor/dn_escape" }
+futures-util = { version = "0.3.34", features = ["sink"] }
 ldap3_proto = "0.8.1"
 serde = { version = "1.0.229", features = ["derive"] }
 tokio = { version = "1.53.1", features = ["macros", "net", "rt", "time", "sync"] }

src/db/common.rs

@@ -26,11 +26,13 @@ impl<D: DatabaseInterface> Database<D> {
     /// TODO: we may want to make sure the method runs in constant time
     ///       to avoid leaking information about existing users...
     ///       or maybe we do not care.
-    async fn check_password(&self, user: &UserRef, password: &str) -> bool {
+    pub async fn check_password(&self, user: &UserRef, password: &str) -> bool {
         let Some(user) = self.get_user(user).await else {
+            tracing::debug!("check_password: User not found {user}");
             return false;
         };
 
+        tracing::debug!("Comparing {} and {}", user.password, password);
         user.password == password
     }
 }

src/db/interface.rs

@@ -1,4 +1,4 @@
-use crate::db::error::*;
+use crate::db::error::UserAlreadyExists;
 use crate::db::{Database, User, UserRef};
 
 impl<D: DatabaseInterface> DatabaseInterface for Database<D> {

src/db/memory.rs

@@ -1,6 +1,6 @@
 use std::future::{Future, ready};
 
-use crate::db::error::*;
+use crate::db::error::UserAlreadyExists;
 use crate::db::{Database, DatabaseInterface, Group, User, UserRef};
 
 #[derive(Clone, Debug, Default)]

src/ldap/client_state.rs

@@ -0,0 +1,35 @@
+use crate::ldap::Dn;
+
+/// Whether a client is successfully logged in (bound).
+///
+/// As it is, this is currently only used for the whoami operation.
+#[derive(Clone, Debug)]
+pub enum LdapClientState {
+    Unbound,
+    Bound(Dn),
+}
+
+impl LdapClientState {
+    pub fn new() -> Self {
+        Self::Unbound
+    }
+
+    pub fn unbind(&mut self) {
+        *self = Self::Unbound;
+    }
+
+    pub fn bind(&mut self, dn: Dn) {
+        *self = Self::Bound(dn);
+    }
+
+    pub fn bound_dn(&self) -> Option<&Dn> {
+        match self {
+            Self::Unbound => None,
+            Self::Bound(dn) => Some(dn),
+        }
+    }
+
+    pub fn bound_dn_string(&self) -> String {
+        self.bound_dn().map_or(String::new(), Dn::to_dn_string)
+    }
+}

src/ldap/dn.rs

@@ -0,0 +1,222 @@
+use dn_escape::dn_escape;
+use ldap3_proto::LdapResultCode;
+
+use crate::db::UserRef;
+use crate::ldap::LdapReturnError;
+
+/// A simple multi-value Map powered by a vector, to respect
+/// order of first appearance of keys.
+#[derive(Clone, Debug)]
+pub struct VecMap {
+    inner: Vec<(String, Vec<String>)>,
+}
+
+impl VecMap {
+    pub fn new() -> Self {
+        Self { inner: vec![] }
+    }
+
+    pub fn get(&self, key: &str) -> Option<&Vec<String>> {
+        for (prev_key, prev_values) in &self.inner {
+            if key == prev_key {
+                return Some(prev_values);
+            }
+        }
+
+        None
+    }
+
+    pub fn insert_or_append(&mut self, key: &str, value: &str) {
+        for (prev_key, prev_values) in &mut self.inner {
+            if key == prev_key {
+                prev_values.push(value.to_string());
+                return;
+            }
+        }
+
+        self.inner.push((key.to_string(), vec![value.to_string()]));
+    }
+
+    pub fn insert(&mut self, key: &str, values: Vec<String>, overwrite: bool) {
+        for (prev_key, prev_values) in &mut self.inner {
+            if key == prev_key {
+                if overwrite {
+                    *prev_values = values;
+                }
+                return;
+            }
+        }
+
+        self.inner.push((key.to_string(), values));
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct InvalidDnError(pub String);
+
+impl LdapReturnError for InvalidDnError {
+    fn code(&self) -> LdapResultCode {
+        LdapResultCode::InvalidDNSyntax
+    }
+
+    fn message(&self) -> String {
+        format!("Invalid dn: {}", self.0)
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct NotUserDnError(pub String);
+
+impl LdapReturnError for NotUserDnError {
+    fn code(&self) -> LdapResultCode {
+        LdapResultCode::InvalidDNSyntax
+    }
+
+    fn message(&self) -> String {
+        format!("Not a user dn containing uid/dc: {}", self.0)
+    }
+}
+
+/// A Dn is a key-value mapping which can contain the same key several times.
+///
+/// This implementation is not fully RFC compliant and will only parse simple DNs for
+/// basic attribute manipulation.
+///
+/// Keys are lowercased, but scrambled keys in a broken order will be reordered. For example,
+/// `dc=example,ou=people,dc=com` will become `dc=example,dc=com,ou=people`.
+#[derive(Clone, Debug)]
+pub struct Dn {
+    pub keys: VecMap,
+}
+
+impl Dn {
+    /// Parse a DN string. Here parsing escaped characters is not critical, if a
+    /// client sends us funny characters, the domain name simply won't match
+    /// and their request won't go anywhere.
+    ///
+    /// However, if we find a really funny request such as `dc=foo=bar`, then
+    /// we return an error to the client.
+    pub fn from_dn_str(input: &str) -> Result<Self, InvalidDnError> {
+        let mut keys = VecMap::new();
+
+        if input.is_empty() {
+            return Ok(Self { keys });
+        }
+
+        for query in input.split(',') {
+            let mut query_parts = query.split('=');
+            // Here we have key=val pairs
+            if query_parts.clone().count() != 2 {
+                // Bad request
+                return Err(InvalidDnError(input.to_string()));
+            }
+
+            let key = query_parts.next().unwrap();
+            let val = query_parts.next().unwrap();
+            keys.insert_or_append(key, val);
+        }
+
+        Ok(Self { keys })
+    }
+
+    pub fn to_dn_string(&self) -> String {
+        let mut s = String::new();
+        let mut first = true;
+        for (key, values) in &self.keys.inner {
+            for value in values {
+                if first {
+                    first = false;
+                } else {
+                    s.push(',');
+                }
+                s.push_str(key);
+                s.push('=');
+                s.push_str(value);
+            }
+        }
+
+        s
+    }
+
+    /// Gets the hostname defined in the `dc` fields of the DN.
+    ///
+    /// For example, `dc=example,dc=com` becomes `Some(example.com)`.
+    ///
+    /// The returned domain is not normalized and may require casing treatment
+    /// to compare meaningfully.
+    pub fn get_hostname(&self) -> Option<String> {
+        let domain_components = self.keys.get("dc")?;
+
+        // We don't populate the dc key if there was no value at all, so
+        // we have at least one component.
+        let mut domain_components = domain_components.iter();
+        let mut s = String::from(domain_components.next().unwrap());
+        for domain_component in domain_components {
+            s.push('.');
+            s.push_str(domain_component);
+        }
+
+        Some(s)
+    }
+
+    /// Overrides the DN hostname (`dc` fields) with the provided host.
+    ///
+    /// When no `dc` fields are present, they are only added when `force` is true.
+    pub fn set_hostname(&mut self, host: &str, force: bool) {
+        let domain_components: Vec<String> =
+            host.split('.').map(|x| dn_escape(x).to_string()).collect();
+
+        self.keys.insert("dc", domain_components, force);
+    }
+
+    pub fn to_user_ref(&self) -> Result<UserRef, NotUserDnError> {
+        let Some(username_vals) = self.keys.get("uid") else {
+            return Err(NotUserDnError(self.to_dn_string()));
+        };
+        if username_vals.len() != 1 {
+            return Err(NotUserDnError(self.to_dn_string()));
+        }
+        let username = username_vals[0].clone();
+
+        let Some(domain_vals) = self.keys.get("dc") else {
+            return Err(NotUserDnError(self.to_dn_string()));
+        };
+        let domain = domain_vals.join(".");
+
+        Ok(UserRef { username, domain })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic_dn_str() {
+        let s = "cn=admin,ou=people,dc=example,dc=com";
+        let mut dn = Dn::from_dn_str(s).unwrap();
+
+        assert_eq!(&dn.to_dn_string(), s);
+        assert_eq!(dn.get_hostname().as_deref(), Some("example.com"));
+        dn.set_hostname("a.localhost", false);
+        assert_eq!(dn.get_hostname().as_deref(), Some("a.localhost"));
+        assert_eq!(&dn.to_dn_string(), "cn=admin,ou=people,dc=a,dc=localhost");
+    }
+
+    #[test]
+    fn test_empty_dn_str() {
+        let s = "";
+        let mut dn = Dn::from_dn_str(s).unwrap();
+
+        assert_eq!(&dn.to_dn_string(), s);
+        assert!(dn.get_hostname().is_none());
+
+        dn.set_hostname("a.localhost", false);
+        assert_eq!(dn.get_hostname().as_deref(), None);
+        assert_eq!(&dn.to_dn_string(), s);
+
+        dn.set_hostname("a.localhost", true);
+        assert_eq!(dn.get_hostname().as_deref(), Some("a.localhost"));
+        assert_eq!(&dn.to_dn_string(), "dc=a,dc=localhost");
+    }
+}

src/ldap/handler.rs

@@ -1,26 +1,35 @@
 use ldap3_proto::LdapMsg;
+use ldap3_proto::proto::LdapOp;
 
 use crate::db::{Database, DatabaseInterface};
-use crate::ldap::{LdapStream, LdapStreamError};
+use crate::ldap::{LdapClientState, LdapStream, LdapStreamError, op_bind, op_ext};
 
-#[tracing::instrument(name = "ldap", skip(s, db), fields(session = %s.session))]
-pub async fn ldap_handler<D: DatabaseInterface>(mut s: LdapStream, db: Database<D>) {
+#[tracing::instrument(name = "ldap", skip(stream, db), fields(session = %stream.session))]
+pub async fn ldap_handler<D: DatabaseInterface>(mut stream: LdapStream, mut db: Database<D>) {
     tracing::info! {
-        remote_addr = ?s.remote_addr,
+        remote_addr = ?stream.remote_addr,
         "New client connection"
     };
 
+    let mut state = LdapClientState::new();
+
     loop {
-        match s.next().await {
-            Ok(msg) => {
-                if let Err(e) = ldap_handler_inner(msg).await {
+        match stream.next().await {
+            Ok(msg) => match ldap_handler_inner(&mut stream, msg, &mut state, &mut db).await {
+                Ok(should_keep_alive) => {
+                    if !should_keep_alive {
+                        tracing::debug!("Finished connection");
+                        return;
+                    }
+                }
+                Err(e) => {
                     tracing::debug!(
                         reason = ?e,
                         "Failed to respond"
                     );
                     return;
                 }
-            }
+            },
             Err(e) => {
                 tracing::debug!(
                     reason = ?e,
@@ -32,7 +41,53 @@ pub async fn ldap_handler<D: DatabaseInterface>(mut s: LdapStream, db: Database<
     }
 }
 
-pub async fn ldap_handler_inner(msg: LdapMsg) -> Result<(), LdapStreamError> {
+/// Return true to keep the connection going, false to close it.
+#[tracing::instrument(name = "ldap-handler", skip(client_state, db, stream))]
+pub async fn ldap_handler_inner<D: DatabaseInterface>(
+    stream: &mut LdapStream,
+    msg: LdapMsg,
+    client_state: &mut LdapClientState,
+    db: &mut Database<D>,
+) -> Result<bool, LdapStreamError> {
     tracing::debug!(msg = ?msg, "Received LDAP message");
-    Ok(())
+    match msg {
+        // Disconnect
+        LdapMsg {
+            msgid: _,
+            op: LdapOp::UnbindRequest,
+            ctrl: _,
+        } => {
+            client_state.unbind();
+            // TODO: keep the connection open?
+            Ok(true)
+        }
+        LdapMsg {
+            msgid,
+            op: LdapOp::ExtendedRequest(ler),
+            ctrl: _,
+        } => {
+            op_ext(stream, ler, msgid, client_state).await?;
+            Ok(true)
+        }
+        LdapMsg {
+            msgid,
+            op: LdapOp::BindRequest(lbr),
+            ctrl: _,
+        } => {
+            if let Some(bound_dn) = op_bind(stream, db, lbr, msgid).await? {
+                tracing::debug!("Successful bind");
+                client_state.bind(bound_dn);
+                Ok(true)
+            } else {
+                tracing::debug!("Unsuccessful bind");
+                // TODO: abort connection here?
+                Ok(false)
+            }
+        }
+        // Unsupported message
+        _ => {
+            tracing::warn!("Unsupported client message, closing connection");
+            Ok(false)
+        }
+    }
 }

src/ldap/mod.rs

@@ -1,4 +1,15 @@
+mod client_state;
+pub use client_state::LdapClientState;
+mod dn;
+pub use dn::{Dn, InvalidDnError, NotUserDnError};
 mod handler;
+mod op;
 pub use handler::ldap_handler;
+pub use op::bind::op_bind;
+pub use op::ext::op_ext;
+mod return_error;
+pub use return_error::LdapReturnError;
 mod stream;
-pub use stream::{LdapStream, LdapStreamError};
+pub use stream::LdapStream;
+mod stream_error;
+pub use stream_error::LdapStreamError;

src/ldap/op/bind.rs

@@ -0,0 +1,129 @@
+use ldap3_proto::proto::{LdapBindCred, LdapBindRequest, LdapBindResponse, LdapOp, LdapResult};
+use ldap3_proto::{LdapMsg, LdapResultCode};
+
+use crate::db::{Database, DatabaseInterface};
+use crate::ldap::{
+    Dn, InvalidDnError, LdapReturnError, LdapStream, LdapStreamError, NotUserDnError,
+};
+
+pub enum BindError {
+    // TODO: DB Error
+    InvalidCredentials,
+    InvalidDn(InvalidDnError),
+    NotUserDn(NotUserDnError),
+    UnsupportedSASL,
+}
+
+impl BindError {
+    pub async fn error_message(
+        &self,
+        stream: &mut LdapStream,
+        msgid: i32,
+    ) -> Result<(), LdapStreamError> {
+        let resp_msg = LdapMsg {
+            msgid,
+            op: LdapOp::BindResponse(LdapBindResponse {
+                res: LdapResult {
+                    code: self.code(),
+                    matcheddn: String::new(),
+                    message: self.message(),
+                    referral: vec![],
+                },
+                saslcreds: None,
+            }),
+            ctrl: vec![],
+        };
+
+        stream.send(resp_msg).await?;
+        Ok(())
+    }
+}
+
+impl From<InvalidDnError> for BindError {
+    fn from(e: InvalidDnError) -> Self {
+        Self::InvalidDn(e)
+    }
+}
+
+impl LdapReturnError for BindError {
+    fn code(&self) -> LdapResultCode {
+        match self {
+            Self::InvalidCredentials => LdapResultCode::InvalidCredentials,
+            Self::InvalidDn(e) => e.code(),
+            Self::NotUserDn(e) => e.code(),
+            Self::UnsupportedSASL => LdapResultCode::OperationsError,
+        }
+    }
+
+    fn message(&self) -> String {
+        match self {
+            Self::InvalidCredentials => "Wrong username or password".to_string(),
+            Self::InvalidDn(e) => e.message(),
+            Self::NotUserDn(e) => e.message(),
+            Self::UnsupportedSASL => "SASL login is not supported".to_string(),
+        }
+    }
+}
+
+pub async fn bind_success(stream: &mut LdapStream, msgid: i32) -> Result<(), LdapStreamError> {
+    let resp_msg = LdapMsg {
+        msgid,
+        op: LdapOp::BindResponse(LdapBindResponse {
+            res: LdapResult {
+                code: LdapResultCode::Success,
+                matcheddn: String::new(),
+                message: String::new(),
+                referral: vec![],
+            },
+            saslcreds: None,
+        }),
+        ctrl: vec![],
+    };
+
+    stream.send(resp_msg).await?;
+    Ok(())
+}
+
+/// Tries to bind the user.
+///
+/// On success, returns `Ok(Some(bound_dn))`. `Ok(None)` means credentials failed,
+/// either because the account does not exist, or the password is wrong.
+pub async fn op_bind<D: DatabaseInterface>(
+    stream: &mut LdapStream,
+    db: &Database<D>,
+    req: LdapBindRequest,
+    msgid: i32,
+) -> Result<Option<Dn>, LdapStreamError> {
+    let dn = match Dn::from_dn_str(&req.dn) {
+        Ok(dn) => dn,
+        Err(e) => {
+            BindError::InvalidDn(e).error_message(stream, msgid).await?;
+            return Ok(None);
+        }
+    };
+
+    let LdapBindCred::Simple(password) = req.cred else {
+        BindError::UnsupportedSASL
+            .error_message(stream, msgid)
+            .await?;
+        return Ok(None);
+    };
+
+    let user_ref = match dn.to_user_ref() {
+        Ok(user_ref) => user_ref,
+        Err(e) => {
+            BindError::NotUserDn(e).error_message(stream, msgid).await?;
+            return Ok(None);
+        }
+    };
+
+    if db.check_password(&user_ref, &password).await {
+        bind_success(stream, msgid).await?;
+        Ok(Some(dn))
+    } else {
+        BindError::InvalidCredentials
+            .error_message(stream, msgid)
+            .await?;
+        Ok(None)
+    }
+}

src/ldap/op/ext.rs

@@ -0,0 +1,43 @@
+use ldap3_proto::proto::{LdapExtendedRequest, LdapExtendedResponse, LdapOp, LdapResult};
+use ldap3_proto::{LdapMsg, LdapResultCode};
+
+use crate::ldap::{LdapClientState, LdapStream, LdapStreamError};
+
+pub async fn op_ext(
+    stream: &mut LdapStream,
+    ler: LdapExtendedRequest,
+    msgid: i32,
+    client_state: &LdapClientState,
+) -> Result<(), LdapStreamError> {
+    let response = match ler.name.as_str() {
+        "1.3.6.1.4.1.4203.1.11.3" => LdapOp::ExtendedResponse(LdapExtendedResponse {
+            res: LdapResult {
+                code: LdapResultCode::Success,
+                matcheddn: String::new(),
+                message: String::new(),
+                referral: vec![],
+            },
+            name: None,
+            value: Some(Vec::from(client_state.bound_dn_string())),
+        }),
+        _ => LdapOp::ExtendedResponse(LdapExtendedResponse {
+            res: LdapResult {
+                code: LdapResultCode::OperationsError,
+                matcheddn: String::new(),
+                message: "Unsupported extended operation".to_string(),
+                referral: vec![],
+            },
+            name: None,
+            value: None,
+        }),
+    };
+
+    stream
+        .send(LdapMsg {
+            msgid,
+            op: response,
+            ctrl: vec![],
+        })
+        .await?;
+    Ok(())
+}

src/ldap/op/mod.rs

@@ -0,0 +1,2 @@
+pub mod bind;
+pub mod ext;

src/ldap/return_error.rs

@@ -0,0 +1,6 @@
+use ldap3_proto::LdapResultCode;
+
+pub trait LdapReturnError {
+    fn code(&self) -> LdapResultCode;
+    fn message(&self) -> String;
+}

src/ldap/stream.rs

@@ -1,32 +1,12 @@
-use futures_util::StreamExt;
+use futures_util::{SinkExt, StreamExt};
 use ldap3_proto::{LdapCodec, LdapMsg};
 use tokio::time::{Duration, timeout};
 use tokio_util::codec::Framed;
 use uuid::Uuid;
 
-use std::fmt;
-
+use crate::ldap::LdapStreamError;
 use crate::stream::{AbstractSocketAddr, AbstractStreamKind};
 
-#[derive(Debug)]
-pub enum LdapStreamError {
-    ClientClosed,
-    Timeout(Duration),
-    LdapError(std::io::Error),
-}
-
-impl fmt::Display for LdapStreamError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Self::ClientClosed => write!(f, "Client closed the connection"),
-            Self::Timeout(d) => write!(f, "Client timeout after {}ms", d.as_millis()),
-            Self::LdapError(e) => write!(f, "Failed to parse LDAP message: {e:?}"),
-        }
-    }
-}
-
-impl std::error::Error for LdapStreamError {}
-
 pub struct LdapStream {
     pub remote_addr: AbstractSocketAddr,
     pub inner: Framed<AbstractStreamKind, LdapCodec>,
@@ -66,4 +46,12 @@ impl LdapStream {
         // because of transient IO error, or any other error condition.
         msg.map_err(LdapStreamError::LdapError)
     }
+
+    pub async fn send(&mut self, msg: LdapMsg) -> Result<(), LdapStreamError> {
+        tracing::debug!(msg=?msg, "Sending to client");
+        self.inner
+            .send(msg)
+            .await
+            .map_err(LdapStreamError::ClientSend)
+    }
 }

src/ldap/stream_error.rs

@@ -0,0 +1,26 @@
+use std::fmt;
+use std::time::Duration;
+
+/// A non-normal condition to close the LDAP stream.
+///
+/// For an error result that does not abort the connection, see [`LdapReturnError`](crate::ldap::LdapReturnError).
+#[derive(Debug)]
+pub enum LdapStreamError {
+    ClientClosed,
+    Timeout(Duration),
+    LdapError(std::io::Error),
+    ClientSend(std::io::Error),
+}
+
+impl fmt::Display for LdapStreamError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::ClientClosed => write!(f, "Client closed the connection"),
+            Self::Timeout(d) => write!(f, "Client timeout after {}ms", d.as_millis()),
+            Self::LdapError(e) => write!(f, "Failed to parse LDAP message: {e:?}"),
+            Self::ClientSend(e) => write!(f, "Failed to send message to the client: {e:?}"),
+        }
+    }
+}
+
+impl std::error::Error for LdapStreamError {}

vendor/dn_escape/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "dn_escape"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

vendor/dn_escape/MIT_LICENSE

@@ -0,0 +1,22 @@
+The MIT License (MIT)
+
+Copyright (c) 2017 Ivan Nejgebauer <inejge@gmail.com>
+Copyright (c) 2014-2017 Gregor Reitzenstein <dean4devil@paranoidlabs.org>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

vendor/dn_escape/README.md

@@ -0,0 +1,4 @@
+# dn_escape
+
+Borrowed from the ldap3 project at version v0.12.1, under MIT license. A copy
+of the license can be found in [MIT_LICENSE](MIT_LICENSE).

vendor/dn_escape/src/lib.rs

@@ -0,0 +1,69 @@
+// CODE DEVELOPED BY THE LDAP3 PROJECT, UNDER MIT LICENSE.
+
+use std::borrow::Cow;
+
+/// Escape an attribute value in a relative distinguished name (RDN).
+///
+/// When a literal string is used to represent an attribute value in an RDN,
+/// some of its characters might need to be escaped according to the rules
+/// of [RFC 4514](https://tools.ietf.org/html/rfc4514).
+///
+/// The function is named `dn_escape()` instead of `rdn_escape()` because of
+/// a long-standing association of its intended use with the handling of DNs.
+///
+/// The argument, `val`, can be owned or borrowed. The function doesn't
+/// allocate the return value unless there's need to escape the input.
+pub fn dn_escape<'a, S: Into<Cow<'a, str>>>(val: S) -> Cow<'a, str> {
+    #[inline]
+    fn always_escape(c: u8) -> bool {
+        c == b'"'
+            || c == b'+'
+            || c == b','
+            || c == b';'
+            || c == b'<'
+            || c == b'='
+            || c == b'>'
+            || c == b'\\'
+            || c == 0
+    }
+
+    #[inline]
+    fn escape_leading(c: u8) -> bool {
+        c == b' ' || c == b'#'
+    }
+
+    #[inline]
+    fn escape_trailing(c: u8) -> bool {
+        c == b' '
+    }
+
+    #[inline]
+    fn xdigit(c: u8) -> u8 {
+        c + if c < 10 { b'0' } else { b'a' - 10 }
+    }
+
+    let val = val.into();
+    let mut output = None;
+    for (i, &c) in val.as_bytes().iter().enumerate() {
+        if always_escape(c)
+            || i == 0 && escape_leading(c)
+            || i + 1 == val.len() && escape_trailing(c)
+        {
+            if output.is_none() {
+                output = Some(Vec::with_capacity(val.len() + 12)); // guess: up to 4 escaped chars
+                output.as_mut().unwrap().extend(val[..i].as_bytes());
+            }
+            let output = output.as_mut().unwrap();
+            output.push(b'\\');
+            output.push(xdigit(c >> 4));
+            output.push(xdigit(c & 0xF));
+        } else if let Some(ref mut output) = output {
+            output.push(c);
+        }
+    }
+    if let Some(output) = output {
+        Cow::Owned(String::from_utf8(output).expect("dn escaped"))
+    } else {
+        val
+    }
+}