Accept RS384 and RS512 JWT tokens.

Previously, we only accepted RS256. Seems like a pointless limitation,
and when I was testing it with RS512 tokens, it took me a while to
understand why it wasn't working.

libs/utils/src/auth.rs

@@ -9,14 +9,26 @@ use std::path::Path;
 
 use anyhow::Result;
 use jsonwebtoken::{
-    decode, encode, Algorithm, DecodingKey, EncodingKey, Header, TokenData, Validation,
+    decode, encode, Algorithm, Algorithm::*, DecodingKey, EncodingKey, Header, TokenData,
+    Validation,
 };
 use serde::{Deserialize, Serialize};
 use serde_with::{serde_as, DisplayFromStr};
 
 use crate::id::TenantId;
 
-const JWT_ALGORITHM: Algorithm = Algorithm::RS256;
+/// Algorithms accepted during validation.
+///
+/// Accept all RSA-based algorithms. We pass this list to jsonwebtoken::decode,
+/// which checks that the algorithm in the token is one of these.
+///
+/// XXX: It also fails the validation if there are any algorithms in this list that belong
+/// to different family than the token's algorithm. In other words, we can *not* list any
+/// non-RSA algorithms here, or the validation always fails with InvalidAlgorithm error.
+const ACCEPTED_ALGORITHMS: &[Algorithm] = &[RS256, RS384, RS512];
+
+/// Algorithm to use when generating a new token in [`encode_from_key_file`]
+const ENCODE_ALGORITHM: Algorithm = Algorithm::RS256;
 
 #[derive(Debug, Serialize, Deserialize, Clone)]
 #[serde(rename_all = "lowercase")]
@@ -33,6 +45,7 @@ pub enum Scope {
     SafekeeperData,
 }
 
+/// JWT payload. See docs/authentication.md for the format
 #[serde_as]
 #[derive(Debug, Serialize, Deserialize, Clone)]
 pub struct Claims {
@@ -55,7 +68,8 @@ pub struct JwtAuth {
 
 impl JwtAuth {
     pub fn new(decoding_key: DecodingKey) -> Self {
-        let mut validation = Validation::new(JWT_ALGORITHM);
+        let mut validation = Validation::default();
+        validation.algorithms = ACCEPTED_ALGORITHMS.into();
         // The default 'required_spec_claims' is 'exp'. But we don't want to require
         // expiration.
         validation.required_spec_claims = [].into();
@@ -86,5 +100,5 @@ impl std::fmt::Debug for JwtAuth {
 // this function is used only for testing purposes in CLI e g generate tokens during init
 pub fn encode_from_key_file(claims: &Claims, key_data: &[u8]) -> Result<String> {
     let key = EncodingKey::from_rsa_pem(key_data)?;
-    Ok(encode(&Header::new(JWT_ALGORITHM), claims, &key)?)
+    Ok(encode(&Header::new(ENCODE_ALGORITHM), claims, &key)?)
 }