Align API behaviour with upstream and return errors on malformed input (#7810)

- Attachments: reject a declared v2 attachment size above the upload limit,
  keep display sizes within the largest unit, and make download links valid
  for 1 minute like upstream.
- Ciphers: moving a personal cipher into an organization needs collection
  write access or full access, like upstream.
- Events: /events/collect only accepts the client event types upstream accepts.
- Client IP: for list headers like X-Forwarded-For, use the rightmost address
  that isn't in IP_HEADER_TRUSTED_PROXIES, reading every occurrence.
- Prelogin: unknown emails get stable KDF settings from upstream's list.
- Login with device: an auth request can be used for one login, like upstream.
- Directory Connector import: never revokes, restores or removes Owners,
  like upstream.
- SSO: check the PKCE verifier again when the code exchange is reused during
  2FA, and accept the same redirect URIs as upstream (desktop localhost
  callback for AppImage and dev builds, CLI on ports 8065-8070).
- Identity: send the merged master password policy in the 2FA response and
  use PascalCase policy keys in identity responses, like upstream.
  Organization API key login no longer needs device fields. Recovery code
  login normalises the code, uses upstream's error message, logs a failed 2FA
  event and sends a "two-step login recovered" email.
- Add GET /api/accounts/keys.
- Return errors instead of panicking on malformed event dates, cipher data,
  key rotation cipher ids, bulk confirm entries and YubiKey OTPs.

src/auth.rs

@@ -14,6 +14,7 @@ use ipnet::IpNet;
 use jsonwebtoken::{Algorithm, DecodingKey, EncodingKey, Header, errors::ErrorKind};
 use num_traits::FromPrimitive;
 use openssl::rsa::Rsa;
+use ring::hmac;
 use serde::{de::DeserializeOwned, ser::Serialize};
 
 use rocket::{
@@ -65,6 +66,7 @@ static JWT_2FA_REMEMBER_ISSUER: LazyLock<String> = LazyLock::new(|| format!("{}|
 
 static PRIVATE_RSA_KEY: OnceLock<EncodingKey> = OnceLock::new();
 static PUBLIC_RSA_KEY: OnceLock<DecodingKey> = OnceLock::new();
+static PRELOGIN_KDF_KEY: OnceLock<hmac::Key> = OnceLock::new();
 
 pub async fn initialize_keys() -> Result<(), Error> {
     use std::io::Error as IoError;
@@ -99,9 +101,22 @@ pub async fn initialize_keys() -> Result<(), Error> {
     if PUBLIC_RSA_KEY.set(dec).is_err() {
         err!("PUBLIC_RSA_KEY must only be initialized once")
     }
+
+    // Derived from the RSA key, so it stays the same across restarts without storing another secret
+    let prelogin_kdf_key = hmac::sign(&hmac::Key::new(hmac::HMAC_SHA256, &priv_key_buffer), b"prelogin-kdf");
+    if PRELOGIN_KDF_KEY.set(hmac::Key::new(hmac::HMAC_SHA256, prelogin_kdf_key.as_ref())).is_err() {
+        err!("PRELOGIN_KDF_KEY must only be initialized once")
+    }
     Ok(())
 }
 
+/// Returns an index in `0..len` derived from the email, the same for every request
+pub fn prelogin_kdf_index(email: &str, len: usize) -> usize {
+    let tag = hmac::sign(PRELOGIN_KDF_KEY.wait(), email.as_bytes());
+    let tag = tag.as_ref();
+    usize::from(u16::from_be_bytes([tag[0], tag[1]])) % len
+}
+
 pub fn encode_jwt<T: Serialize>(claims: &T) -> String {
     match jsonwebtoken::encode(&JWT_HEADER, claims, PRIVATE_RSA_KEY.wait()) {
         Ok(token) => token,
@@ -422,7 +437,7 @@ pub fn generate_file_download_claims(cipher_id: CipherId, file_id: AttachmentId)
     let time_now = Utc::now();
     FileDownloadClaims {
         nbf: time_now.timestamp(),
-        exp: (time_now + TimeDelta::try_minutes(5).unwrap()).timestamp(),
+        exp: (time_now + TimeDelta::try_minutes(1).unwrap()).timestamp(),
         iss: JWT_FILE_DOWNLOAD_ISSUER.to_string(),
         sub: cipher_id,
         file_id,
@@ -1091,6 +1106,31 @@ fn ip_header_is_trusted(remote: Option<IpAddr>) -> bool {
     trusted.split(',').filter_map(parse_trusted_proxy).any(|net| net.contains(&remote))
 }
 
+/// Each proxy appends the address it received the request from to a list header (`X-Forwarded-For: client, proxy1`).
+/// Like ASP.NET's ForwardedHeaders, walk the entries of every occurrence of the header from the right and take the
+/// first one that isn't a trusted proxy. If they all are, the leftmost one is the client.
+fn client_ip_from_header(req: &Request<'_>, header: &str, is_trusted: impl Fn(IpAddr) -> bool) -> Option<IpAddr> {
+    let values: Vec<&str> = req.headers().get(header).collect();
+    client_ip_from_header_values(&values, header, is_trusted)
+}
+
+fn client_ip_from_header_values(values: &[&str], header: &str, is_trusted: impl Fn(IpAddr) -> bool) -> Option<IpAddr> {
+    let entries: Vec<&str> = values.iter().flat_map(|value| value.split(',')).map(str::trim).collect();
+
+    let mut client_ip = None;
+    for entry in entries.into_iter().rev() {
+        let Ok(ip) = entry.parse() else {
+            warn!("'{header}' header is malformed: {entry}");
+            break;
+        };
+        client_ip = Some(ip);
+        if !is_trusted(ip) {
+            break;
+        }
+    }
+    client_ip
+}
+
 #[rocket::async_trait]
 impl<'r> FromRequest<'r> for ClientIp {
     type Error = ();
@@ -1099,15 +1139,7 @@ impl<'r> FromRequest<'r> for ClientIp {
         let remote = req.remote().map(|r| r.ip());
 
         let ip = if CONFIG._ip_header_enabled() && ip_header_is_trusted(remote) {
-            req.headers().get_one(&CONFIG.ip_header()).and_then(|ip| {
-                match ip.find(',') {
-                    Some(idx) => &ip[..idx],
-                    None => ip,
-                }
-                .parse()
-                .map_err(|_| warn!("'{}' header is malformed: {ip}", CONFIG.ip_header()))
-                .ok()
-            })
+            client_ip_from_header(req, &CONFIG.ip_header(), |ip| ip_header_is_trusted(Some(ip)))
         } else {
             if CONFIG._ip_header_enabled() && req.headers().get_one(&CONFIG.ip_header()).is_some() {
                 // Log the canonical IP, which is what the user filter will need to match against
@@ -1226,7 +1258,7 @@ impl AuthMethod {
         match scope {
             None => err!("Missing scope"),
             Some(scope) if scope == &method_scope => Ok(method_scope),
-            Some(scope) => err!(format!("Scope ({scope}) not supported")),
+            Some(scope) => err!(format!("Scope ({}) not supported", scope.escape_debug())),
         }
     }
 }
@@ -1345,3 +1377,52 @@ pub async fn refresh_tokens(
 
     Ok((device, auth_tokens))
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn client_ip(values: &[&str]) -> Option<IpAddr> {
+        let is_trusted = |ip: IpAddr| match ip {
+            IpAddr::V4(v4) => v4.is_private() || v4.is_loopback(),
+            IpAddr::V6(v6) => v6.is_loopback(),
+        };
+        client_ip_from_header_values(values, "X-Forwarded-For", is_trusted)
+    }
+
+    fn ip(s: &str) -> Option<IpAddr> {
+        Some(s.parse().unwrap())
+    }
+
+    #[test]
+    fn ip_header_single_value() {
+        assert_eq!(client_ip(&["203.0.113.5"]), ip("203.0.113.5"));
+        assert_eq!(client_ip(&["10.0.0.7"]), ip("10.0.0.7"));
+        assert_eq!(client_ip(&["2001:db8::1"]), ip("2001:db8::1"));
+    }
+
+    #[test]
+    fn ip_header_uses_rightmost_untrusted_entry() {
+        // Entries already in the request come before the one the proxy appended
+        assert_eq!(client_ip(&["198.51.100.1, 203.0.113.5"]), ip("203.0.113.5"));
+        // Trusted proxies on the right are skipped
+        assert_eq!(client_ip(&["198.51.100.1, 203.0.113.5, 10.0.0.2, 127.0.0.1"]), ip("203.0.113.5"));
+        // All trusted, so the leftmost entry is the client
+        assert_eq!(client_ip(&["192.168.1.10, 10.0.0.2"]), ip("192.168.1.10"));
+    }
+
+    #[test]
+    fn ip_header_reads_every_occurrence() {
+        assert_eq!(client_ip(&["198.51.100.1", "203.0.113.5"]), ip("203.0.113.5"));
+        assert_eq!(client_ip(&["198.51.100.1", "203.0.113.5, 10.0.0.2"]), ip("203.0.113.5"));
+    }
+
+    #[test]
+    fn ip_header_malformed_entries() {
+        assert_eq!(client_ip(&[]), None);
+        assert_eq!(client_ip(&[""]), None);
+        assert_eq!(client_ip(&["203.0.113.5, not-an-ip"]), None);
+        // Stops at the malformed entry and keeps the closest proxy
+        assert_eq!(client_ip(&["not-an-ip, 10.0.0.2"]), ip("10.0.0.2"));
+    }
+}