feat: Search queries by mail attribute

src/ldap/client_state.rs

@@ -1,4 +1,4 @@
-use crate::ldap::Dn;
+use crate::ldap::BindDn;
 
 /// Whether a client is successfully logged in (bound).
 ///
@@ -6,7 +6,7 @@ use crate::ldap::Dn;
 #[derive(Clone, Debug)]
 pub enum LdapClientState {
     Unbound,
-    Bound(Dn),
+    Bound(BindDn),
 }
 
 impl LdapClientState {
@@ -18,11 +18,11 @@ impl LdapClientState {
         *self = Self::Unbound;
     }
 
-    pub fn bind(&mut self, dn: Dn) {
+    pub fn bind(&mut self, dn: BindDn) {
         *self = Self::Bound(dn);
     }
 
-    pub fn bound_dn(&self) -> Option<&Dn> {
+    pub fn bound_dn(&self) -> Option<&BindDn> {
         match self {
             Self::Unbound => None,
             Self::Bound(dn) => Some(dn),
@@ -30,6 +30,6 @@ impl LdapClientState {
     }
 
     pub fn bound_dn_string(&self) -> String {
-        self.bound_dn().map_or(String::new(), Dn::to_dn_string)
+        self.bound_dn().map_or(String::new(), BindDn::to_dn_string)
     }
 }

src/ldap/dn.rs

@@ -1,8 +1,6 @@
 use dn_escape::dn_escape;
-use ldap3_proto::LdapResultCode;
 
-use crate::db::UserRef;
-use crate::ldap::LdapReturnError;
+use crate::db::User;
 
 /// A simple multi-value Map powered by a vector, to respect
 /// order of first appearance of keys.
@@ -52,30 +50,7 @@ impl VecMap {
 }
 
 #[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)
-    }
-}
+pub struct MalformedDn;
 
 /// A Dn is a key-value mapping which can contain the same key several times.
 ///
@@ -96,7 +71,7 @@ impl Dn {
     ///
     /// 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> {
+    pub fn from_dn_str(input: &str) -> Result<Self, MalformedDn> {
         let mut keys = VecMap::new();
 
         if input.is_empty() {
@@ -108,7 +83,7 @@ impl Dn {
             // Here we have key=val pairs
             if query_parts.clone().count() != 2 {
                 // Bad request
-                return Err(InvalidDnError(input.to_string()));
+                return Err(MalformedDn);
             }
 
             let key = query_parts.next().unwrap();
@@ -169,21 +144,15 @@ impl Dn {
         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()));
+    pub fn from_user(user: &User) -> Self {
+        let mut keys = VecMap::new();
+        keys.insert_or_append("uid", &user.username);
+        keys.insert_or_append("ou", "people");
+        for domain_component in user.domain.split('.') {
+            keys.insert_or_append("dc", domain_component);
         }
-        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 })
+        Self { keys }
     }
 }
 

src/ldap/filter/mail.rs

@@ -0,0 +1,248 @@
+use ldap3_proto::{LdapFilter, LdapResultCode};
+
+use std::fmt;
+
+use crate::db::UserRef;
+use crate::ldap::LdapReturnError;
+
+#[derive(Clone, Debug)]
+pub struct MailFilter {
+    pub complete: String,
+    pub username: String,
+    pub domain: String,
+}
+
+impl fmt::Display for MailFilter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", self.complete)
+    }
+}
+
+impl MailFilter {
+    /// Tries to parse a string into an email address.
+    ///
+    /// This method is not really RFC-compliant because it merely splits by `@`,
+    /// but is good enough for what we do.
+    pub fn new(value: &str) -> Result<Self, MailDomainError> {
+        let original = value;
+        // Here we normalize the mail attribute to lowercase to prevent
+        // useless mismatches.
+        // TODO: investigate if that's supposed to be a problem for anyone?
+        let value = value.to_lowercase();
+        if value != original {
+            tracing::debug!("Normalized search email from {original} to {value}");
+        }
+
+        let mut parts = value.split('@');
+        let username = parts.next().unwrap();
+        let Some(domain) = parts.next() else {
+            tracing::debug!("Not a valid username@domain email: {value}");
+            return Err(MailDomainError::InvalidMail);
+        };
+
+        if parts.next().is_some() {
+            tracing::debug!("Too many parts in mail address");
+            return Err(MailDomainError::InvalidMail);
+        }
+
+        Ok(Self {
+            complete: value.clone(),
+            username: username.to_string(),
+            domain: domain.to_string(),
+        })
+    }
+
+    /// Extract any mail filter from an LDAP search filter
+    /// which may contain other criteria, which we overall don't care about
+    /// at the moment.
+    pub fn from_search_filter(filter: &LdapFilter) -> Result<Self, MailDomainError> {
+        let res = match filter {
+            LdapFilter::And(filters) | LdapFilter::Or(filters) => {
+                Self::from_multiple_filters(filters)
+            }
+            LdapFilter::Equality(attr, value) => {
+                if let Some(domain) = Self::from_equality_filter(attr, value)? {
+                    Ok(domain)
+                } else {
+                    Err(MailDomainError::NoMailFilter)
+                }
+            }
+            _ => Err(MailDomainError::InvalidFilter),
+        };
+
+        match &res {
+            Ok(mail) => tracing::debug!("Found email in search filter: {mail}"),
+            Err(e) => tracing::debug!("Not found email in search filter: {}", e.message()),
+        }
+
+        res
+    }
+
+    /// Extract any mail filter from a bunch of LDAP filters.
+    ///
+    /// Any filter that is not an equality check is discarded.
+    fn from_multiple_filters(filters: &[LdapFilter]) -> Result<Self, MailDomainError> {
+        for filter in filters {
+            if let LdapFilter::Equality(attr, value) = filter {
+                // Here if we receive None, it means the filter was not checking for the
+                // `mail` attr so we continue iterating.
+                if let Some(found) = Self::from_equality_filter(attr, value)? {
+                    return Ok(found);
+                }
+            }
+        }
+
+        Err(MailDomainError::NoMailFilter)
+    }
+
+    /// Extract any mail filter from an LDAP search equality filter extracted
+    /// from a global search filter.
+    fn from_equality_filter(attr: &str, value: &str) -> Result<Option<Self>, MailDomainError> {
+        if attr != "mail" {
+            return Ok(None);
+        }
+
+        let mail = Self::new(value)?;
+        Ok(Some(mail))
+    }
+
+    pub fn to_user_ref(&self) -> UserRef {
+        UserRef {
+            username: self.username.clone(),
+            domain: self.domain.clone(),
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum MailDomainError {
+    /// mail value not user@domain format
+    InvalidMail,
+    /// No mail filter found in the search query
+    NoMailFilter,
+    /// Filter is not And/Or/Equality for which we can find a mail filter
+    InvalidFilter,
+}
+
+impl fmt::Display for MailDomainError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let msg = match self {
+            Self::InvalidMail => {
+                "No valid email address requested in mail filter in search request"
+            }
+            Self::NoMailFilter => "No mail filter found in search request",
+            Self::InvalidFilter => "No AND/OR/EQUALITY filter found in search request",
+        };
+        write!(f, "{msg}")
+    }
+}
+
+impl LdapReturnError for MailDomainError {
+    fn code(&self) -> LdapResultCode {
+        match self {
+            Self::InvalidMail => LdapResultCode::InvalidAttributeSyntax,
+            Self::NoMailFilter => LdapResultCode::InappropriateMatching,
+            Self::InvalidFilter => LdapResultCode::UnwillingToPerform,
+        }
+    }
+
+    fn message(&self) -> String {
+        self.to_string()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::filter::{search_filter_and, search_filter_eq};
+
+    use super::*;
+
+    #[test]
+    fn no_mail_filter() {
+        let filter = search_filter_and(&[
+            search_filter_eq("uid", "a"),
+            search_filter_eq("objectClass", "inetOrgPerson"),
+        ]);
+
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let e = mail_filter.unwrap_err();
+        assert_eq!(e, MailDomainError::NoMailFilter);
+    }
+
+    #[test]
+    fn invalid_filter() {
+        let filter = LdapFilter::Approx("mail".to_string(), "a@a.localhost".to_string());
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let e = mail_filter.unwrap_err();
+        assert_eq!(e, MailDomainError::InvalidFilter);
+    }
+
+    #[test]
+    fn invalid_mail_no_domain() {
+        let filter = search_filter_eq("mail", "a");
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let e = mail_filter.unwrap_err();
+        assert_eq!(e, MailDomainError::InvalidMail);
+    }
+
+    #[test]
+    fn invalid_mail_too_many_parts() {
+        let filter = search_filter_eq("mail", "a@a.localhost@a.localhost");
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let e = mail_filter.unwrap_err();
+        assert_eq!(e, MailDomainError::InvalidMail);
+    }
+
+    #[test]
+    fn valid_basic() {
+        let filter = search_filter_eq("mail", "a@a.localhost");
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let mail = mail_filter.unwrap();
+        assert_eq!(mail.complete, "a@a.localhost");
+        assert_eq!(mail.username, "a");
+        assert_eq!(mail.domain, "a.localhost");
+    }
+
+    #[test]
+    fn valid_basic_normalization() {
+        let filter = search_filter_eq("mail", "A@A.localhost");
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let mail = mail_filter.unwrap();
+        assert_eq!(mail.complete, "a@a.localhost");
+        assert_eq!(mail.username, "a");
+        assert_eq!(mail.domain, "a.localhost");
+    }
+
+    #[test]
+    fn stalwart_default() {
+        // (&(objectClass=inetOrgPerson)(mail=?))
+        let filter = search_filter_and(&[
+            search_filter_eq("mail", "a@a.localhost"),
+            search_filter_eq("objectClass", "inetOrgPerson"),
+        ]);
+
+        let mail_filter = MailFilter::from_search_filter(&filter);
+        println!("{:?}", mail_filter);
+        let mail = mail_filter.unwrap();
+        assert_eq!(mail.complete, "a@a.localhost");
+        assert_eq!(mail.username, "a");
+        assert_eq!(mail.domain, "a.localhost");
+    }
+
+    // fn stalwart_lldap_example() {
+    //     // &(|(objectClass=person)(member=cn=mail,ou=groups,dc=example,dc=org))(uid=?))
+    //     let filter = search_filter_and(&[
+    //         search_filter_eq("uid", "a"),
+    //         search_filter_or(&[
+    //             search_filter_eq("objectClass", "person"),
+    //             search_filter_eq("member", "cn=mail,ou=groups,dc=a,dc=localhost"),
+    //         ]),
+    //     ]);
+    // }
+}

src/ldap/filter/mod.rs

@@ -0,0 +1 @@
+pub mod mail;

src/ldap/handler.rs

@@ -2,7 +2,9 @@ use ldap3_proto::LdapMsg;
 use ldap3_proto::proto::LdapOp;
 
 use crate::db::{Database, DatabaseInterface};
-use crate::ldap::{LdapClientState, LdapStream, LdapStreamError, op_bind, op_ext};
+use crate::ldap::{
+    LdapClientState, LdapStream, LdapStreamError, op_bind, op_ext, search_by_mail_filter,
+};
 
 #[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>) {
@@ -79,11 +81,21 @@ pub async fn ldap_handler_inner<D: DatabaseInterface>(
                 client_state.bind(bound_dn);
                 Ok(true)
             } else {
-                tracing::debug!("Unsuccessful bind");
-                // TODO: abort connection here?
-                Ok(false)
+                client_state.unbind();
+                tracing::debug!("Failed bind or anonymous bind");
+                // We keep the connection open in case it's an anonymous bind
+                Ok(true)
             }
         }
+        LdapMsg {
+            msgid,
+            op: LdapOp::SearchRequest(sr),
+            // TODO: ctrl for pagination
+            ctrl: _,
+        } => {
+            search_by_mail_filter(stream, db, sr, msgid).await?;
+            Ok(true)
+        }
         // Unsupported message
         _ => {
             tracing::warn!("Unsupported client message, closing connection");

src/ldap/mod.rs

@@ -1,12 +1,14 @@
 mod client_state;
 pub use client_state::LdapClientState;
 mod dn;
-pub use dn::{Dn, InvalidDnError, NotUserDnError};
+pub use dn::{Dn, MalformedDn};
+mod filter;
 mod handler;
 mod op;
 pub use handler::ldap_handler;
-pub use op::bind::op_bind;
+pub use op::bind::{BindDn, op_bind};
 pub use op::ext::op_ext;
+pub use op::search::search_by_mail_filter;
 mod return_error;
 pub use return_error::LdapReturnError;
 mod stream;

src/ldap/op/bind.rs

@@ -2,17 +2,91 @@ use ldap3_proto::proto::{LdapBindCred, LdapBindRequest, LdapBindResponse, LdapOp
 use ldap3_proto::{LdapMsg, LdapResultCode};
 
 use crate::db::error::BoxedError;
-use crate::db::{Database, DatabaseInterface};
-use crate::ldap::{
-    Dn, InvalidDnError, LdapReturnError, LdapStream, LdapStreamError, NotUserDnError,
+use crate::db::{Database, DatabaseInterface, UserRef};
+use crate::ldap::{Dn, LdapReturnError, LdapStream, LdapStreamError, MalformedDn};
+
+#[derive(Debug)]
+pub struct InvalidBindDn {
+    dn: String,
+    kind: InvalidBindDnKind,
+}
+
+#[derive(Debug)]
+pub enum InvalidBindDnKind {
+    Malformed(MalformedDn),
+    NoUid,
+    MultipleUid,
+    NoDc,
+}
+
+impl LdapReturnError for InvalidBindDn {
+    fn code(&self) -> LdapResultCode {
+        LdapResultCode::InvalidDNSyntax
+    }
+
+    fn message(&self) -> String {
+        match &self.kind {
+            InvalidBindDnKind::Malformed(_e) => format!("Malformed dn: {}", self.dn),
+            InvalidBindDnKind::NoUid => format!("Missing `uid` in bind dn: {}", self.dn),
+            InvalidBindDnKind::MultipleUid => {
+                format!("Multiple `uid` accounts provided in bind dn: {}", self.dn)
+            }
+            InvalidBindDnKind::NoDc => format!("Missing `dc` in bind dn: {}", self.dn),
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct BindDn(Dn);
+
+impl BindDn {
+    pub fn from_dn_str(input: &str) -> Result<Self, InvalidBindDn> {
+        let dn = Dn::from_dn_str(input).map_err(|e| InvalidBindDn {
+            dn: input.to_string(),
+            kind: InvalidBindDnKind::Malformed(e),
+        })?;
+
+        let Some(uid) = dn.keys.get("uid") else {
+            return Err(InvalidBindDn {
+                dn: input.to_string(),
+                kind: InvalidBindDnKind::NoUid,
+            });
         };
 
+        if uid.len() != 1 {
+            return Err(InvalidBindDn {
+                dn: input.to_string(),
+                kind: InvalidBindDnKind::MultipleUid,
+            });
+        }
+
+        if dn.get_hostname().is_none() {
+            return Err(InvalidBindDn {
+                dn: input.to_string(),
+                kind: InvalidBindDnKind::NoDc,
+            });
+        }
+
+        Ok(Self(dn))
+    }
+
+    pub fn to_dn_string(&self) -> String {
+        self.0.to_dn_string()
+    }
+
+    pub fn to_user_ref(&self) -> UserRef {
+        let username = self.0.keys.get("uid").unwrap()[0].clone();
+        let domain = self.0.keys.get("dc").unwrap().join(".");
+
+        UserRef { username, domain }
+    }
+}
+
 #[derive(Debug)]
 pub enum BindError {
     Db(BoxedError),
     InvalidCredentials,
-    InvalidDn(InvalidDnError),
-    NotUserDn(NotUserDnError),
+    InvalidDn(InvalidBindDn),
     UnsupportedSASL,
 }
 
@@ -42,19 +116,12 @@ impl BindError {
     }
 }
 
-impl From<InvalidDnError> for BindError {
-    fn from(e: InvalidDnError) -> Self {
-        Self::InvalidDn(e)
-    }
-}
-
 impl LdapReturnError for BindError {
     fn code(&self) -> LdapResultCode {
         match self {
             Self::Db(_e) => LdapResultCode::Unavailable,
             Self::InvalidCredentials => LdapResultCode::InvalidCredentials,
             Self::InvalidDn(e) => e.code(),
-            Self::NotUserDn(e) => e.code(),
             Self::UnsupportedSASL => LdapResultCode::OperationsError,
         }
     }
@@ -64,7 +131,6 @@ impl LdapReturnError for BindError {
             Self::Db(e) => format!("Database error: {e}"),
             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(),
         }
     }
@@ -98,8 +164,14 @@ pub async fn op_bind<D: DatabaseInterface>(
     db: &Database<D>,
     req: LdapBindRequest,
     msgid: i32,
-) -> Result<Option<Dn>, LdapStreamError> {
-    let dn = match Dn::from_dn_str(&req.dn) {
+) -> Result<Option<BindDn>, LdapStreamError> {
+    // Anonymous bind
+    if req.dn.is_empty() {
+        bind_success(stream, msgid).await?;
+        return Ok(None);
+    }
+
+    let dn = match BindDn::from_dn_str(&req.dn) {
         Ok(dn) => dn,
         Err(e) => {
             BindError::InvalidDn(e).error_message(stream, msgid).await?;
@@ -114,15 +186,7 @@ pub async fn op_bind<D: DatabaseInterface>(
         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);
-        }
-    };
-
-    let success = match db.check_password(&user_ref, &password).await {
+    let success = match db.check_password(&dn.to_user_ref(), &password).await {
         Ok(success) => success,
         Err(e) => {
             // tracing::error!(error = &*e as &dyn std::error::Error, "Database failure");

src/ldap/op/mod.rs

@@ -1,2 +1,3 @@
 pub mod bind;
 pub mod ext;
+pub mod search;

src/ldap/op/search.rs

@@ -0,0 +1,217 @@
+use ldap3_proto::control::LdapControl;
+use ldap3_proto::proto::{
+    LdapOp, LdapPartialAttribute, LdapResult, LdapSearchRequest, LdapSearchResultEntry,
+};
+use ldap3_proto::{LdapMsg, LdapResultCode};
+
+use crate::db::error::BoxedError;
+use crate::db::{Database, DatabaseInterface, User};
+use crate::ldap::filter::mail::{MailDomainError, MailFilter};
+use crate::ldap::{Dn, LdapReturnError, LdapStream, LdapStreamError, MalformedDn};
+
+#[derive(Debug)]
+pub struct InvalidSearchDn {
+    dn: String,
+    kind: InvalidSearchDnKind,
+}
+
+#[derive(Debug)]
+pub enum InvalidSearchDnKind {
+    Malformed(MalformedDn),
+    NoOu,
+    MultipleOu,
+}
+
+impl LdapReturnError for InvalidSearchDn {
+    fn code(&self) -> LdapResultCode {
+        LdapResultCode::InvalidDNSyntax
+    }
+
+    fn message(&self) -> String {
+        match &self.kind {
+            InvalidSearchDnKind::Malformed(_e) => format!("Malformed dn: {}", self.dn),
+            InvalidSearchDnKind::NoOu => format!("Missing `ou` in search dn: {}", self.dn),
+            InvalidSearchDnKind::MultipleOu => {
+                format!("Multiple `ou` tables provided in search dn: {}", self.dn)
+            }
+        }
+    }
+}
+
+#[derive(Clone, Debug)]
+pub struct SearchDn(Dn);
+
+impl SearchDn {
+    pub fn from_dn_str(input: &str) -> Result<Self, InvalidSearchDn> {
+        let dn = Dn::from_dn_str(input).map_err(|e| InvalidSearchDn {
+            dn: input.to_string(),
+            kind: InvalidSearchDnKind::Malformed(e),
+        })?;
+
+        let Some(ou) = dn.keys.get("ou") else {
+            return Err(InvalidSearchDn {
+                dn: input.to_string(),
+                kind: InvalidSearchDnKind::NoOu,
+            });
+        };
+
+        if ou.len() != 1 {
+            return Err(InvalidSearchDn {
+                dn: input.to_string(),
+                kind: InvalidSearchDnKind::MultipleOu,
+            });
+        }
+
+        Ok(Self(dn))
+    }
+}
+
+#[derive(Debug)]
+pub enum SearchError {
+    Db(BoxedError),
+    InvalidDn(InvalidSearchDn),
+    MailDomain(MailDomainError),
+}
+
+impl SearchError {
+    pub async fn error_message(
+        &self,
+        stream: &mut LdapStream,
+        msgid: i32,
+    ) -> Result<(), LdapStreamError> {
+        let resp_msg = LdapMsg {
+            msgid,
+            op: LdapOp::SearchResultDone(LdapResult {
+                code: self.code(),
+                matcheddn: String::new(),
+                message: self.message(),
+                referral: vec![],
+            }),
+            ctrl: vec![],
+        };
+
+        stream.send(resp_msg).await?;
+        Ok(())
+    }
+}
+
+impl LdapReturnError for SearchError {
+    fn code(&self) -> LdapResultCode {
+        match self {
+            Self::Db(_e) => LdapResultCode::Unavailable,
+            Self::InvalidDn(e) => e.code(),
+            Self::MailDomain(e) => e.code(),
+        }
+    }
+
+    fn message(&self) -> String {
+        match self {
+            Self::Db(e) => format!("Database error: {e}"),
+            Self::InvalidDn(e) => e.message(),
+            Self::MailDomain(e) => e.message(),
+        }
+    }
+}
+
+pub async fn search_success(
+    stream: &mut LdapStream,
+    msgid: i32,
+    entries: Vec<(LdapSearchResultEntry, Vec<LdapControl>)>,
+) -> Result<(), LdapStreamError> {
+    let count = entries.len();
+
+    for (entry, ctrl) in entries {
+        tracing::debug!("Search result: {entry:?}");
+        stream
+            .send(LdapMsg {
+                msgid,
+                op: LdapOp::SearchResultEntry(entry),
+                ctrl,
+            })
+            .await?;
+    }
+
+    stream
+        .send(LdapMsg {
+            msgid,
+            op: LdapOp::SearchResultDone(LdapResult {
+                code: LdapResultCode::Success,
+                matcheddn: String::new(),
+                message: format!("Found {count} result(s)"),
+                referral: vec![],
+            }),
+            // TODO: implement LdapControl for pagination
+            ctrl: vec![],
+        })
+        .await?;
+
+    Ok(())
+}
+
+fn search_entry_from_user(user: &User, req_attrs: &[String]) -> LdapSearchResultEntry {
+    let mut res: Vec<LdapPartialAttribute> = vec![];
+    for attr in req_attrs {
+        if let Some(attr_value) = match attr.as_str() {
+            "uid" => Some(user.username.clone()),
+            "cn"|"mail" => Some(user.mail.clone()),
+            _ => {
+                tracing::warn!("Ignoring unknown attr in search query: {attr}");
+                None
+            }
+        } {
+            res.push(LdapPartialAttribute {
+                atype: attr.clone(),
+                // TODO: there may be multiple values here in the future,
+                // eg. mailaliases
+                vals: vec![Vec::from(attr_value)],
+            });
+        }
+    }
+
+    LdapSearchResultEntry {
+        dn: Dn::from_user(user).to_dn_string(),
+        attributes: res,
+    }
+}
+
+pub async fn search_by_mail_filter<D: DatabaseInterface>(
+    stream: &mut LdapStream,
+    db: &Database<D>,
+    sr: LdapSearchRequest,
+    msgid: i32,
+) -> Result<(), LdapStreamError> {
+    // TODO: We should probably reuse the search DN somehow
+    if let Err(e) = SearchDn::from_dn_str(&sr.base) {
+        SearchError::InvalidDn(e)
+            .error_message(stream, msgid)
+            .await?;
+        return Ok(());
+    }
+
+    let mail_filter = match MailFilter::from_search_filter(&sr.filter) {
+        Ok(mail_filter) => mail_filter,
+        Err(e) => {
+            SearchError::MailDomain(e)
+                .error_message(stream, msgid)
+                .await?;
+            return Ok(());
+        }
+    };
+
+    let maybe_user = match db.get_user(&mail_filter.to_user_ref()).await {
+        Ok(maybe_user) => maybe_user,
+        Err(e) => {
+            SearchError::Db(e).error_message(stream, msgid).await?;
+            return Ok(());
+        }
+    };
+
+    if let Some(user) = maybe_user {
+        let entry_ctrl = (search_entry_from_user(&user, &sr.attrs), vec![]);
+        search_success(stream, msgid, vec![entry_ctrl]).await?;
+    } else {
+        search_success(stream, msgid, vec![]).await?;
+    }
+
+    Ok(())
+}