Unicode normalization on input.

This normalizes the following values:

* login names
* passwords
* channel names
* message bodies, because why not

The goal here is to have a canonical representation of these values, so that, for example, the service does not inadvertently host two channels whose names are semantically identical but differ in the specifics of how diacritics are encoded, or two users whose names are identical.

Normalization is done on input from the wire, using Serde hooks, and when reading from the database. The `crate::nfc::String` type implements these normalizations (as well as normalizing whenever converted from a `std::string::String` generally).

This change does not cover:

* Trying to cope with passwords that were created as non-normalized strings, which are now non-verifiable as all the paths to verify passwords normalize the input.
* Trying to ensure that non-normalized data in the database compares reasonably to normalized data. Fortunately, we don't _do_ very many string comparisons (I think only login names), so this isn't a huge deal at this stage. Login names will probably have to Get Fixed later on, when we figure out how to handle case folding for login name verification.

31 files changed, 284 insertions, 83 deletions

diff --git a/src/channel/app.rs b/src/channel/app.rs
index 75c662d..ea60943 100644
--- a/src/channel/app.rs
+++ b/src/channel/app.rs
@@ -2,7 +2,7 @@ use chrono::TimeDelta;
 use itertools::Itertools;
 use sqlx::sqlite::SqlitePool;
 
-use super::{repo::Provider as _, Channel, History, Id};
+use super::{repo::Provider as _, Channel, History, Id, Name};
 use crate::{
     clock::DateTime,
     db::{Duplicate as _, NotFound as _},
@@ -20,14 +20,14 @@ impl<'a> Channels<'a> {
         Self { db, events }
     }
 
-    pub async fn create(&self, name: &str, created_at: &DateTime) -> Result<Channel, CreateError> {
+    pub async fn create(&self, name: &Name, created_at: &DateTime) -> Result<Channel, CreateError> {
         let mut tx = self.db.begin().await?;
         let created = tx.sequence().next(created_at).await?;
         let channel = tx
             .channels()
             .create(name, &created)
             .await
-            .duplicate(|| CreateError::DuplicateName(name.into()))?;
+            .duplicate(|| CreateError::DuplicateName(name.clone()))?;
         tx.commit().await?;
 
         self.events
@@ -134,7 +134,7 @@ impl<'a> Channels<'a> {
 #[derive(Debug, thiserror::Error)]
 pub enum CreateError {
     #[error("channel named {0} already exists")]
-    DuplicateName(String),
+    DuplicateName(Name),
     #[error(transparent)]
     Database(#[from] sqlx::Error),
 }
diff --git a/src/channel/mod.rs b/src/channel/mod.rs
index eb8200b..fb13e92 100644
--- a/src/channel/mod.rs
+++ b/src/channel/mod.rs
@@ -2,8 +2,11 @@ pub mod app;
 pub mod event;
 mod history;
 mod id;
+mod name;
 pub mod repo;
 mod routes;
 mod snapshot;
 
-pub use self::{event::Event, history::History, id::Id, routes::router, snapshot::Channel};
+pub use self::{
+    event::Event, history::History, id::Id, name::Name, routes::router, snapshot::Channel,
+};
diff --git a/src/channel/name.rs b/src/channel/name.rs
new file mode 100644
index 0000000..fc82dec
--- /dev/null
+++ b/src/channel/name.rs
@@ -0,0 +1,30 @@
+use std::fmt;
+
+use crate::nfc;
+
+#[derive(
+    Clone, Debug, Default, Eq, PartialEq, serde::Deserialize, serde::Serialize, sqlx::Type,
+)]
+#[serde(transparent)]
+#[sqlx(transparent)]
+pub struct Name(nfc::String);
+
+impl fmt::Display for Name {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self(name) = self;
+        name.fmt(f)
+    }
+}
+
+impl From<String> for Name {
+    fn from(name: String) -> Self {
+        Self(name.into())
+    }
+}
+
+impl From<Name> for String {
+    fn from(name: Name) -> Self {
+        let Name(name) = name;
+        name.into()
+    }
+}
diff --git a/src/channel/repo.rs b/src/channel/repo.rs
index 27d35f0..3353bfd 100644
--- a/src/channel/repo.rs
+++ b/src/channel/repo.rs
@@ -1,7 +1,7 @@
 use sqlx::{sqlite::Sqlite, SqliteConnection, Transaction};
 
 use crate::{
-    channel::{Channel, History, Id},
+    channel::{Channel, History, Id, Name},
     clock::DateTime,
     event::{Instant, ResumePoint, Sequence},
 };
@@ -19,7 +19,7 @@ impl<'c> Provider for Transaction<'c, Sqlite> {
 pub struct Channels<'t>(&'t mut SqliteConnection);
 
 impl<'c> Channels<'c> {
-    pub async fn create(&mut self, name: &str, created: &Instant) -> Result<History, sqlx::Error> {
+    pub async fn create(&mut self, name: &Name, created: &Instant) -> Result<History, sqlx::Error> {
         let id = Id::generate();
         let channel = sqlx::query!(
             r#"
@@ -28,7 +28,7 @@ impl<'c> Channels<'c> {
                 values ($1, $2, $3, $4)
                 returning
                     id as "id: Id",
-                    name as "name!", -- known non-null as we just set it
+                    name as "name!: Name", -- known non-null as we just set it
                     created_at as "created_at: DateTime",
                     created_sequence as "created_sequence: Sequence"
             "#,
@@ -57,7 +57,7 @@ impl<'c> Channels<'c> {
             r#"
                 select
                     id as "id: Id",
-                    channel.name,
+                    channel.name as "name: Name",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
                     deleted.deleted_at as "deleted_at?: DateTime",
@@ -89,7 +89,7 @@ impl<'c> Channels<'c> {
             r#"
                 select
                     id as "id: Id",
-                    channel.name,
+                    channel.name as "name: Name",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
                     deleted.deleted_at as "deleted_at: DateTime",
@@ -125,7 +125,7 @@ impl<'c> Channels<'c> {
             r#"
                 select
                     id as "id: Id",
-                    channel.name,
+                    channel.name as "name: Name",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
                     deleted.deleted_at as "deleted_at: DateTime",
@@ -235,7 +235,7 @@ impl<'c> Channels<'c> {
             r#"
                 select
                     channel.id as "id: Id",
-                    channel.name,
+                    channel.name as "name: Name",
                     channel.created_at as "created_at: DateTime",
                     channel.created_sequence as "created_sequence: Sequence",
                     deleted.deleted_at as "deleted_at?: DateTime",
diff --git a/src/channel/routes/channel/post.rs b/src/channel/routes/channel/post.rs
index b489a77..d0cae05 100644
--- a/src/channel/routes/channel/post.rs
+++ b/src/channel/routes/channel/post.rs
@@ -9,7 +9,7 @@ use crate::{
     clock::RequestedAt,
     error::{Internal, NotFound},
     login::Login,
-    message::{app::SendError, Message},
+    message::{app::SendError, Body, Message},
 };
 
 pub async fn handler(
@@ -29,7 +29,7 @@ pub async fn handler(
 
 #[derive(serde::Deserialize)]
 pub struct Request {
-    pub body: String,
+    pub body: Body,
 }
 
 #[derive(Debug)]
diff --git a/src/channel/routes/post.rs b/src/channel/routes/post.rs
index a05c312..d354f79 100644
--- a/src/channel/routes/post.rs
+++ b/src/channel/routes/post.rs
@@ -6,7 +6,7 @@ use axum::{
 
 use crate::{
     app::App,
-    channel::{app, Channel},
+    channel::{app, Channel, Name},
     clock::RequestedAt,
     error::Internal,
     login::Login,
@@ -29,7 +29,7 @@ pub async fn handler(
 
 #[derive(serde::Deserialize)]
 pub struct Request {
-    pub name: String,
+    pub name: Name,
 }
 
 #[derive(Debug)]
diff --git a/src/channel/snapshot.rs b/src/channel/snapshot.rs
index 2b7d89a..dc2894d 100644
--- a/src/channel/snapshot.rs
+++ b/src/channel/snapshot.rs
@@ -1,13 +1,13 @@
 use super::{
     event::{Created, Event},
-    Id,
+    Id, Name,
 };
 use crate::clock::DateTime;
 
 #[derive(Clone, Debug, Eq, PartialEq, serde::Serialize)]
 pub struct Channel {
     pub id: Id,
-    pub name: String,
+    pub name: Name,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub deleted_at: Option<DateTime>,
 }
diff --git a/src/invite/app.rs b/src/invite/app.rs
index ee7f74f..285a819 100644
--- a/src/invite/app.rs
+++ b/src/invite/app.rs
@@ -6,7 +6,7 @@ use crate::{
     clock::DateTime,
     db::{Duplicate as _, NotFound as _},
     event::repo::Provider as _,
-    login::{repo::Provider as _, Login, Password},
+    login::{repo::Provider as _, Login, Name, Password},
     token::{repo::Provider as _, Secret},
 };
 
@@ -42,7 +42,7 @@ impl<'a> Invites<'a> {
     pub async fn accept(
         &self,
         invite: &Id,
-        name: &str,
+        name: &Name,
         password: &Password,
         accepted_at: &DateTime,
     ) -> Result<(Login, Secret), AcceptError> {
@@ -68,7 +68,7 @@ impl<'a> Invites<'a> {
             .logins()
             .create(name, &password_hash, &created)
             .await
-            .duplicate(|| AcceptError::DuplicateLogin(name.into()))?;
+            .duplicate(|| AcceptError::DuplicateLogin(name.clone()))?;
         let secret = tx.tokens().issue(&login, accepted_at).await?;
         tx.commit().await?;
 
@@ -92,7 +92,7 @@ pub enum AcceptError {
     #[error("invite not found: {0}")]
     NotFound(Id),
     #[error("name in use: {0}")]
-    DuplicateLogin(String),
+    DuplicateLogin(Name),
     #[error(transparent)]
     Database(#[from] sqlx::Error),
     #[error(transparent)]
diff --git a/src/invite/routes/invite/post.rs b/src/invite/routes/invite/post.rs
index c072929..8160465 100644
--- a/src/invite/routes/invite/post.rs
+++ b/src/invite/routes/invite/post.rs
@@ -9,7 +9,7 @@ use crate::{
     clock::RequestedAt,
     error::{Internal, NotFound},
     invite::app,
-    login::{Login, Password},
+    login::{Login, Name, Password},
     token::extract::IdentityToken,
 };
 
@@ -31,7 +31,7 @@ pub async fn handler(
 
 #[derive(serde::Deserialize)]
 pub struct Request {
-    pub name: String,
+    pub name: Name,
     pub password: Password,
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index 73a2cb0..4d0d9b9 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -16,6 +16,7 @@ mod id;
 mod invite;
 mod login;
 mod message;
+mod nfc;
 mod setup;
 #[cfg(test)]
 mod test;
diff --git a/src/login/app.rs b/src/login/app.rs
index b6f7e1c..ebc1c00 100644
--- a/src/login/app.rs
+++ b/src/login/app.rs
@@ -1,6 +1,6 @@
 use sqlx::sqlite::SqlitePool;
 
-use super::{repo::Provider as _, Login, Password};
+use super::{repo::Provider as _, Login, Name, Password};
 use crate::{
     clock::DateTime,
     event::{repo::Provider as _, Broadcaster, Event},
@@ -18,7 +18,7 @@ impl<'a> Logins<'a> {
 
     pub async fn create(
         &self,
-        name: &str,
+        name: &Name,
         password: &Password,
         created_at: &DateTime,
     ) -> Result<Login, CreateError> {
diff --git a/src/login/mod.rs b/src/login/mod.rs
index 98cc3d7..71d5bfc 100644
--- a/src/login/mod.rs
+++ b/src/login/mod.rs
@@ -4,11 +4,13 @@ pub mod event;
 pub mod extract;
 mod history;
 mod id;
+mod name;
 pub mod password;
 pub mod repo;
 mod routes;
 mod snapshot;
 
 pub use self::{
-    event::Event, history::History, id::Id, password::Password, routes::router, snapshot::Login,
+    event::Event, history::History, id::Id, name::Name, password::Password, routes::router,
+    snapshot::Login,
 };
diff --git a/src/login/name.rs b/src/login/name.rs
new file mode 100644
index 0000000..d882ff9
--- /dev/null
+++ b/src/login/name.rs
@@ -0,0 +1,28 @@
+use std::fmt;
+
+use crate::nfc;
+
+#[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize, sqlx::Type)]
+#[serde(transparent)]
+#[sqlx(transparent)]
+pub struct Name(nfc::String);
+
+impl fmt::Display for Name {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self(name) = self;
+        name.fmt(f)
+    }
+}
+
+impl From<String> for Name {
+    fn from(name: String) -> Self {
+        Self(name.into())
+    }
+}
+
+impl From<Name> for String {
+    fn from(name: Name) -> Self {
+        let Name(name) = name;
+        name.into()
+    }
+}
diff --git a/src/login/password.rs b/src/login/password.rs
index 14fd981..f9ecf37 100644
--- a/src/login/password.rs
+++ b/src/login/password.rs
@@ -4,6 +4,8 @@ use argon2::Argon2;
 use password_hash::{PasswordHash, PasswordHasher, PasswordVerifier, SaltString};
 use rand_core::OsRng;
 
+use crate::nfc;
+
 #[derive(sqlx::Type)]
 #[sqlx(transparent)]
 pub struct StoredHash(String);
@@ -31,7 +33,7 @@ impl fmt::Debug for StoredHash {
 
 #[derive(serde::Deserialize)]
 #[serde(transparent)]
-pub struct Password(String);
+pub struct Password(nfc::String);
 
 impl Password {
     pub fn hash(&self) -> Result<StoredHash, password_hash::Error> {
@@ -56,9 +58,8 @@ impl fmt::Debug for Password {
     }
 }
 
-#[cfg(test)]
 impl From<String> for Password {
     fn from(password: String) -> Self {
-        Self(password)
+        Password(password.into())
     }
 }
diff --git a/src/login/repo.rs b/src/login/repo.rs
index 7d0fcb1..204329f 100644
--- a/src/login/repo.rs
+++ b/src/login/repo.rs
@@ -3,7 +3,7 @@ use sqlx::{sqlite::Sqlite, SqliteConnection, Transaction};
 use crate::{
     clock::DateTime,
     event::{Instant, ResumePoint, Sequence},
-    login::{password::StoredHash, History, Id, Login},
+    login::{password::StoredHash, History, Id, Login, Name},
 };
 
 pub trait Provider {
@@ -21,7 +21,7 @@ pub struct Logins<'t>(&'t mut SqliteConnection);
 impl<'c> Logins<'c> {
     pub async fn create(
         &mut self,
-        name: &str,
+        name: &Name,
         password_hash: &StoredHash,
         created: &Instant,
     ) -> Result<History, sqlx::Error> {
@@ -34,7 +34,7 @@ impl<'c> Logins<'c> {
                 values ($1, $2, $3, $4, $5)
                 returning
                     id as "id: Id",
-                    name,
+                    name as "name: Name",
                     created_sequence as "created_sequence: Sequence",
                     created_at as "created_at: DateTime"
             "#,
@@ -62,7 +62,7 @@ impl<'c> Logins<'c> {
             r#"
                 select
                     id as "id: Id",
-                    name,
+                    name as "name: Name",
                     created_sequence as "created_sequence: Sequence",
                     created_at as "created_at: DateTime"
                 from login
@@ -88,7 +88,7 @@ impl<'c> Logins<'c> {
             r#"
                 select
                     id as "id: Id",
-                    name,
+                    name as "name: Name",
                     created_sequence as "created_sequence: Sequence",
                     created_at as "created_at: DateTime"
                 from login
diff --git a/src/login/routes/login/post.rs b/src/login/routes/login/post.rs
index 67eaa6d..7a685e2 100644
--- a/src/login/routes/login/post.rs
+++ b/src/login/routes/login/post.rs
@@ -8,7 +8,7 @@ use crate::{
     app::App,
     clock::RequestedAt,
     error::Internal,
-    login::{Login, Password},
+    login::{Login, Name, Password},
     token::{app, extract::IdentityToken},
 };
 
@@ -29,7 +29,7 @@ pub async fn handler(
 
 #[derive(serde::Deserialize)]
 pub struct Request {
-    pub name: String,
+    pub name: Name,
     pub password: Password,
 }
 
diff --git a/src/login/snapshot.rs b/src/login/snapshot.rs
index 1a92f5c..85800e4 100644
--- a/src/login/snapshot.rs
+++ b/src/login/snapshot.rs
@@ -1,6 +1,6 @@
 use super::{
     event::{Created, Event},
-    Id,
+    Id, Name,
 };
 
 // This also implements FromRequestParts (see `./extract.rs`). As a result, it
@@ -10,7 +10,7 @@ use super::{
 #[derive(Clone, Debug, Eq, PartialEq, serde::Serialize)]
 pub struct Login {
     pub id: Id,
-    pub name: String,
+    pub name: Name,
     // The omission of the hashed password is deliberate, to minimize the
     // chance that it ends up tangled up in debug output or in some other chunk
     // of logic elsewhere.
diff --git a/src/message/app.rs b/src/message/app.rs
index 4e50513..af87553 100644
--- a/src/message/app.rs
+++ b/src/message/app.rs
@@ -2,7 +2,7 @@ use chrono::TimeDelta;
 use itertools::Itertools;
 use sqlx::sqlite::SqlitePool;
 
-use super::{repo::Provider as _, Id, Message};
+use super::{repo::Provider as _, Body, Id, Message};
 use crate::{
     channel::{self, repo::Provider as _},
     clock::DateTime,
@@ -26,7 +26,7 @@ impl<'a> Messages<'a> {
         channel: &channel::Id,
         sender: &Login,
         sent_at: &DateTime,
-        body: &str,
+        body: &Body,
     ) -> Result<Message, SendError> {
         let mut tx = self.db.begin().await?;
         let channel = tx
diff --git a/src/message/body.rs b/src/message/body.rs
new file mode 100644
index 0000000..a415f85
--- /dev/null
+++ b/src/message/body.rs
@@ -0,0 +1,30 @@
+use std::fmt;
+
+use crate::nfc;
+
+#[derive(
+    Clone, Debug, Default, Eq, PartialEq, serde::Deserialize, serde::Serialize, sqlx::Type,
+)]
+#[serde(transparent)]
+#[sqlx(transparent)]
+pub struct Body(nfc::String);
+
+impl fmt::Display for Body {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self(body) = self;
+        body.fmt(f)
+    }
+}
+
+impl From<String> for Body {
+    fn from(body: String) -> Self {
+        Self(body.into())
+    }
+}
+
+impl From<Body> for String {
+    fn from(body: Body) -> Self {
+        let Body(body) = body;
+        body.into()
+    }
+}
diff --git a/src/message/mod.rs b/src/message/mod.rs
index a8f51ab..c2687bc 100644
--- a/src/message/mod.rs
+++ b/src/message/mod.rs
@@ -1,4 +1,5 @@
 pub mod app;
+mod body;
 pub mod event;
 mod history;
 mod id;
@@ -6,4 +7,6 @@ pub mod repo;
 mod routes;
 mod snapshot;
 
-pub use self::{event::Event, history::History, id::Id, routes::router, snapshot::Message};
+pub use self::{
+    body::Body, event::Event, history::History, id::Id, routes::router, snapshot::Message,
+};
diff --git a/src/message/repo.rs b/src/message/repo.rs
index 85a69fc..4cfefec 100644
--- a/src/message/repo.rs
+++ b/src/message/repo.rs
@@ -1,6 +1,6 @@
 use sqlx::{sqlite::Sqlite, SqliteConnection, Transaction};
 
-use super::{snapshot::Message, History, Id};
+use super::{snapshot::Message, Body, History, Id};
 use crate::{
     channel,
     clock::DateTime,
@@ -26,24 +26,24 @@ impl<'c> Messages<'c> {
         channel: &channel::History,
         sender: &Login,
         sent: &Instant,
-        body: &str,
+        body: &Body,
     ) -> Result<History, sqlx::Error> {
         let id = Id::generate();
         let channel_id = channel.id();
 
         let message = sqlx::query!(
             r#"
-				insert into message
-					(id, channel, sender, sent_at, sent_sequence, body)
-				values ($1, $2, $3, $4, $5, $6)
-				returning
-					id as "id: Id",
+                insert into message
+                    (id, channel, sender, sent_at, sent_sequence, body)
+                values ($1, $2, $3, $4, $5, $6)
+                returning
+                    id as "id: Id",
                     channel as "channel: channel::Id",
                     sender as "sender: login::Id",
                     sent_at as "sent_at: DateTime",
                     sent_sequence as "sent_sequence: Sequence",
-					body
-			"#,
+                    body as "body: Body"
+            "#,
             id,
             channel_id,
             sender.id,
@@ -76,7 +76,7 @@ impl<'c> Messages<'c> {
                     message.channel as "channel: channel::Id",
                     message.sender as "sender: login::Id",
                     id as "id: Id",
-                    message.body,
+                    message.body as "body: Body",
                     message.sent_at as "sent_at: DateTime",
                     message.sent_sequence as "sent_sequence: Sequence",
                     deleted.deleted_at as "deleted_at: DateTime",
@@ -113,7 +113,7 @@ impl<'c> Messages<'c> {
                     message.channel as "channel: channel::Id",
                     message.sender as "sender: login::Id",
                     id as "id: Id",
-                    message.body,
+                    message.body as "body: Body",
                     message.sent_at as "sent_at: DateTime",
                     message.sent_sequence as "sent_sequence: Sequence",
                     deleted.deleted_at as "deleted_at: DateTime",
@@ -150,7 +150,7 @@ impl<'c> Messages<'c> {
                     message.channel as "channel: channel::Id",
                     message.sender as "sender: login::Id",
                     id as "id: Id",
-                    message.body,
+                    message.body as "body: Body",
                     message.sent_at as "sent_at: DateTime",
                     message.sent_sequence as "sent_sequence: Sequence",
                     deleted.deleted_at as "deleted_at?: DateTime",
@@ -256,7 +256,7 @@ impl<'c> Messages<'c> {
                     message.sender as "sender: login::Id",
                     message.sent_at as "sent_at: DateTime",
                     message.sent_sequence as "sent_sequence: Sequence",
-                    message.body,
+                    message.body as "body: Body",
                     deleted.deleted_at as "deleted_at?: DateTime",
                     deleted.deleted_sequence as "deleted_sequence?: Sequence"
                 from message
@@ -293,7 +293,7 @@ impl<'c> Messages<'c> {
                     message.sender as "sender: login::Id",
                     message.sent_at as "sent_at: DateTime",
                     message.sent_sequence as "sent_sequence: Sequence",
-                    message.body,
+                    message.body as "body: Body",
                     deleted.deleted_at as "deleted_at: DateTime",
                     deleted.deleted_sequence as "deleted_sequence: Sequence"
                 from message
diff --git a/src/message/snapshot.rs b/src/message/snapshot.rs
index 7300918..53b7176 100644
--- a/src/message/snapshot.rs
+++ b/src/message/snapshot.rs
@@ -1,6 +1,6 @@
 use super::{
     event::{Event, Sent},
-    Id,
+    Body, Id,
 };
 use crate::{channel, clock::DateTime, event::Instant, login};
 
@@ -11,7 +11,7 @@ pub struct Message {
     pub channel: channel::Id,
     pub sender: login::Id,
     pub id: Id,
-    pub body: String,
+    pub body: Body,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub deleted_at: Option<DateTime>,
 }
diff --git a/src/nfc.rs b/src/nfc.rs
new file mode 100644
index 0000000..70e936c
--- /dev/null
+++ b/src/nfc.rs
@@ -0,0 +1,103 @@
+use std::{fmt, string::String as StdString};
+
+use sqlx::{
+    encode::{Encode, IsNull},
+    Database, Decode, Type,
+};
+use unicode_normalization::UnicodeNormalization as _;
+
+#[derive(Clone, Debug, Default, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
+#[serde(from = "StdString", into = "StdString")]
+pub struct String(StdString);
+
+impl fmt::Display for String {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Self(value) = self;
+        value.fmt(f)
+    }
+}
+
+impl From<StdString> for String {
+    fn from(value: StdString) -> Self {
+        let value = value.nfc().collect();
+
+        Self(value)
+    }
+}
+
+impl From<String> for StdString {
+    fn from(value: String) -> Self {
+        let String(value) = value;
+        value
+    }
+}
+
+impl std::ops::Deref for String {
+    type Target = StdString;
+
+    fn deref(&self) -> &Self::Target {
+        let Self(value) = self;
+        value
+    }
+}
+
+// Type is manually implemented so that we can implement Decode to do
+// normalization on read. Implementation is otherwise based on
+// `#[derive(sqlx::Type)]` with the `#[sqlx(transparent)]` attribute.
+impl<DB> Type<DB> for String
+where
+    DB: Database,
+    StdString: Type<DB>,
+{
+    fn type_info() -> <DB as Database>::TypeInfo {
+        <StdString as Type<DB>>::type_info()
+    }
+
+    fn compatible(ty: &<DB as Database>::TypeInfo) -> bool {
+        <StdString as Type<DB>>::compatible(ty)
+    }
+}
+
+impl<'r, DB> Decode<'r, DB> for String
+where
+    DB: Database,
+    StdString: Decode<'r, DB>,
+{
+    fn decode(value: <DB as Database>::ValueRef<'r>) -> Result<Self, sqlx::error::BoxDynError> {
+        let value = StdString::decode(value)?;
+        let value = value.nfc().collect();
+        Ok(Self(value))
+    }
+}
+
+impl<'q, DB> Encode<'q, DB> for String
+where
+    DB: Database,
+    StdString: Encode<'q, DB>,
+{
+    fn encode_by_ref(
+        &self,
+        buf: &mut <DB as Database>::ArgumentBuffer<'q>,
+    ) -> Result<IsNull, sqlx::error::BoxDynError> {
+        let Self(value) = self;
+        value.encode_by_ref(buf)
+    }
+
+    fn encode(
+        self,
+        buf: &mut <DB as Database>::ArgumentBuffer<'q>,
+    ) -> Result<IsNull, sqlx::error::BoxDynError> {
+        let Self(value) = self;
+        value.encode(buf)
+    }
+
+    fn produces(&self) -> Option<<DB as Database>::TypeInfo> {
+        let Self(value) = self;
+        value.produces()
+    }
+
+    fn size_hint(&self) -> usize {
+        let Self(value) = self;
+        value.size_hint()
+    }
+}
diff --git a/src/setup/app.rs b/src/setup/app.rs
index d015813..9fbcf6d 100644
--- a/src/setup/app.rs
+++ b/src/setup/app.rs
@@ -4,7 +4,7 @@ use super::repo::Provider as _;
 use crate::{
     clock::DateTime,
     event::{repo::Provider as _, Broadcaster, Event},
-    login::{repo::Provider as _, Login, Password},
+    login::{repo::Provider as _, Login, Name, Password},
     token::{repo::Provider as _, Secret},
 };
 
@@ -20,7 +20,7 @@ impl<'a> Setup<'a> {
 
     pub async fn initial(
         &self,
-        name: &str,
+        name: &Name,
         password: &Password,
         created_at: &DateTime,
     ) -> Result<(Login, Secret), Error> {
diff --git a/src/setup/routes/post.rs b/src/setup/routes/post.rs
index 34f4ed2..6a3fa11 100644
--- a/src/setup/routes/post.rs
+++ b/src/setup/routes/post.rs
@@ -8,7 +8,7 @@ use crate::{
     app::App,
     clock::RequestedAt,
     error::Internal,
-    login::{Login, Password},
+    login::{Login, Name, Password},
     setup::app,
     token::extract::IdentityToken,
 };
@@ -30,7 +30,7 @@ pub async fn handler(
 
 #[derive(serde::Deserialize)]
 pub struct Request {
-    pub name: String,
+    pub name: Name,
     pub password: Password,
 }
 
diff --git a/src/test/fixtures/channel.rs b/src/test/fixtures/channel.rs
index a1dda61..024ac1b 100644
--- a/src/test/fixtures/channel.rs
+++ b/src/test/fixtures/channel.rs
@@ -8,7 +8,7 @@ use rand;
 
 use crate::{
     app::App,
-    channel::{self, Channel},
+    channel::{self, Channel, Name},
     clock::RequestedAt,
     event::Event,
 };
@@ -21,13 +21,13 @@ pub async fn create(app: &App, created_at: &RequestedAt) -> Channel {
         .expect("should always succeed if the channel is actually new")
 }
 
-pub fn propose() -> String {
-    rand::random::<Name>().to_string()
+pub fn propose() -> Name {
+    rand::random::<NameTemplate>().to_string().into()
 }
 
-struct Name(String);
+struct NameTemplate(String);
 faker_impl_from_templates! {
-    Name; "{} {}", CityName, FullName;
+    NameTemplate; "{} {}", CityName, FullName;
 }
 
 pub fn events(event: Event) -> future::Ready<Option<channel::Event>> {
diff --git a/src/test/fixtures/login.rs b/src/test/fixtures/login.rs
index b6766fe..0a42320 100644
--- a/src/test/fixtures/login.rs
+++ b/src/test/fixtures/login.rs
@@ -4,7 +4,7 @@ use uuid::Uuid;
 use crate::{
     app::App,
     clock::RequestedAt,
-    login::{self, Login, Password},
+    login::{self, Login, Name, Password},
 };
 
 pub async fn create_with_password(app: &App, created_at: &RequestedAt) -> (Login, Password) {
@@ -29,16 +29,16 @@ pub async fn create(app: &App, created_at: &RequestedAt) -> Login {
 pub fn fictitious() -> Login {
     Login {
         id: login::Id::generate(),
-        name: name(),
+        name: propose_name(),
     }
 }
 
-pub fn propose() -> (String, Password) {
-    (name(), propose_password())
+pub fn propose() -> (Name, Password) {
+    (propose_name(), propose_password())
 }
 
-fn name() -> String {
-    rand::random::<internet::Username>().to_string()
+fn propose_name() -> Name {
+    rand::random::<internet::Username>().to_string().into()
 }
 
 pub fn propose_password() -> Password {
diff --git a/src/test/fixtures/message.rs b/src/test/fixtures/message.rs
index eb00e7c..c450bce 100644
--- a/src/test/fixtures/message.rs
+++ b/src/test/fixtures/message.rs
@@ -8,7 +8,7 @@ use crate::{
     clock::RequestedAt,
     event::Event,
     login::Login,
-    message::{self, Message},
+    message::{self, Body, Message},
 };
 
 pub async fn send(app: &App, channel: &Channel, login: &Login, sent_at: &RequestedAt) -> Message {
@@ -20,8 +20,8 @@ pub async fn send(app: &App, channel: &Channel, login: &Login, sent_at: &Request
         .expect("should succeed if the channel exists")
 }
 
-pub fn propose() -> String {
-    rand::random::<Paragraphs>().to_string()
+pub fn propose() -> Body {
+    rand::random::<Paragraphs>().to_string().into()
 }
 
 pub fn events(event: Event) -> future::Ready<Option<message::Event>> {
diff --git a/src/token/app.rs b/src/token/app.rs
index 0dc1a46..d4dd1a0 100644
--- a/src/token/app.rs
+++ b/src/token/app.rs
@@ -12,7 +12,7 @@ use super::{
 use crate::{
     clock::DateTime,
     db::NotFound as _,
-    login::{Login, Password},
+    login::{Login, Name, Password},
 };
 
 pub struct Tokens<'a> {
@@ -27,7 +27,7 @@ impl<'a> Tokens<'a> {
 
     pub async fn login(
         &self,
-        name: &str,
+        name: &Name,
         password: &Password,
         login_at: &DateTime,
     ) -> Result<(Login, Secret), LoginError> {
diff --git a/src/token/repo/auth.rs b/src/token/repo/auth.rs
index 88d0878..c621b65 100644
--- a/src/token/repo/auth.rs
+++ b/src/token/repo/auth.rs
@@ -3,7 +3,7 @@ use sqlx::{sqlite::Sqlite, SqliteConnection, Transaction};
 use crate::{
     clock::DateTime,
     event::{Instant, Sequence},
-    login::{self, password::StoredHash, History, Login},
+    login::{self, password::StoredHash, History, Login, Name},
 };
 
 pub trait Provider {
@@ -19,12 +19,12 @@ impl<'c> Provider for Transaction<'c, Sqlite> {
 pub struct Auth<'t>(&'t mut SqliteConnection);
 
 impl<'t> Auth<'t> {
-    pub async fn for_name(&mut self, name: &str) -> Result<(History, StoredHash), sqlx::Error> {
+    pub async fn for_name(&mut self, name: &Name) -> Result<(History, StoredHash), sqlx::Error> {
         let found = sqlx::query!(
             r#"
 				select
 					id as "id: login::Id",
-					name,
+					name as "name: Name",
 					password_hash as "password_hash: StoredHash",
                     created_sequence as "created_sequence: Sequence",
                     created_at as "created_at: DateTime"
diff --git a/src/token/repo/token.rs b/src/token/repo/token.rs
index c592dcd..960bb72 100644
--- a/src/token/repo/token.rs
+++ b/src/token/repo/token.rs
@@ -3,7 +3,7 @@ use uuid::Uuid;
 
 use crate::{
     clock::DateTime,
-    login::{self, History, Login},
+    login::{self, History, Login, Name},
     token::{Id, Secret},
 };
 
@@ -128,7 +128,7 @@ impl<'c> Tokens<'c> {
                 select
                     token.id as "token_id: Id",
                     login.id as "login_id: login::Id",
-                    login.name as "login_name"
+                    login.name as "login_name: Name"
                 from login
                 join token on login.id = token.login
                 where token.secret = $1