Fix for RSA Keys which are read only (#4744)

* Fix for RSA Keys which are read only

Sometimes an RSA Key file could be read only.
We currently failed because we also wanted to write.
Added an extra check if the file exists already and is not 0 in size.
If it does already exists and is larger then 0, then open in read only
mode.

Fixes #4644

* Updated code to work atomically

- Changed the code to work atomically
- Also show the alert generated from `Io`

* Fix spelling

2 files changed, 29 insertions, 22 deletions

diff --git a/src/auth.rs b/src/auth.rs
index 4ee9c188..0f4a3076 100644
--- a/src/auth.rs
+++ b/src/auth.rs
@@ -1,13 +1,18 @@
 // JWT Handling
 //
 use chrono::{TimeDelta, Utc};
+use jsonwebtoken::{errors::ErrorKind, Algorithm, DecodingKey, EncodingKey, Header};
 use num_traits::FromPrimitive;
 use once_cell::sync::{Lazy, OnceCell};
-
-use jsonwebtoken::{errors::ErrorKind, Algorithm, DecodingKey, EncodingKey, Header};
 use openssl::rsa::Rsa;
 use serde::de::DeserializeOwned;
 use serde::ser::Serialize;
+use std::{
+    env,
+    fs::File,
+    io::{Read, Write},
+    net::IpAddr,
+};
 
 use crate::{error::Error, CONFIG};
 
@@ -31,27 +36,36 @@ static PRIVATE_RSA_KEY: OnceCell<EncodingKey> = OnceCell::new();
 static PUBLIC_RSA_KEY: OnceCell<DecodingKey> = OnceCell::new();
 
 pub fn initialize_keys() -> Result<(), crate::error::Error> {
-    let mut priv_key_buffer = Vec::with_capacity(2048);
+    fn read_key(create_if_missing: bool) -> Result<(Rsa<openssl::pkey::Private>, Vec<u8>), crate::error::Error> {
+        let mut priv_key_buffer = Vec::with_capacity(2048);
 
-    let priv_key = {
-        let mut priv_key_file =
-            File::options().create(true).truncate(false).read(true).write(true).open(CONFIG.private_rsa_key())?;
+        let mut priv_key_file = File::options()
+            .create(create_if_missing)
+            .truncate(false)
+            .read(true)
+            .write(create_if_missing)
+            .open(CONFIG.private_rsa_key())?;
 
         #[allow(clippy::verbose_file_reads)]
         let bytes_read = priv_key_file.read_to_end(&mut priv_key_buffer)?;
 
-        if bytes_read > 0 {
+        let rsa_key = if bytes_read > 0 {
             Rsa::private_key_from_pem(&priv_key_buffer[..bytes_read])?
-        } else {
+        } else if create_if_missing {
             // Only create the key if the file doesn't exist or is empty
             let rsa_key = openssl::rsa::Rsa::generate(2048)?;
             priv_key_buffer = rsa_key.private_key_to_pem()?;
             priv_key_file.write_all(&priv_key_buffer)?;
-            info!("Private key created correctly.");
+            info!("Private key '{}' created correctly", CONFIG.private_rsa_key());
             rsa_key
-        }
-    };
+        } else {
+            err!("Private key does not exist or invalid format", CONFIG.private_rsa_key());
+        };
 
+        Ok((rsa_key, priv_key_buffer))
+    }
+
+    let (priv_key, priv_key_buffer) = read_key(true).or_else(|_| read_key(false))?;
     let pub_key_buffer = priv_key.public_key_to_pem()?;
 
     let enc = EncodingKey::from_rsa_pem(&priv_key_buffer)?;
@@ -803,12 +817,6 @@ impl<'r> FromRequest<'r> for OwnerHeaders {
 //
 // Client IP address detection
 //
-use std::{
-    env,
-    fs::File,
-    io::{Read, Write},
-    net::IpAddr,
-};
 
 pub struct ClientIp {
     pub ip: IpAddr,
diff --git a/src/main.rs b/src/main.rs
index ecc4f320..8a3f0eb8 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -73,11 +73,9 @@ async fn main() -> Result<(), Error> {
     });
     init_logging(level).ok();
 
-    let extra_debug = matches!(level, LF::Trace | LF::Debug);
-
     check_data_folder().await;
-    auth::initialize_keys().unwrap_or_else(|_| {
-        error!("Error creating keys, exiting...");
+    auth::initialize_keys().unwrap_or_else(|e| {
+        error!("Error creating private key '{}'\n{e:?}\nExiting Vaultwarden!", CONFIG.private_rsa_key());
         exit(1);
     });
     check_web_vault();
@@ -91,6 +89,7 @@ async fn main() -> Result<(), Error> {
     schedule_jobs(pool.clone());
     crate::db::models::TwoFactor::migrate_u2f_to_webauthn(&mut pool.get().await.unwrap()).await.unwrap();
 
+    let extra_debug = matches!(level, LF::Trace | LF::Debug);
     launch_rocket(pool, extra_debug).await // Blocks until program termination.
 }
 
@@ -514,7 +513,7 @@ async fn launch_rocket(pool: db::DbPool, extra_debug: bool) -> Result<(), Error>
 
     tokio::spawn(async move {
         tokio::signal::ctrl_c().await.expect("Error setting Ctrl-C handler");
-        info!("Exiting vaultwarden!");
+        info!("Exiting Vaultwarden!");
         CONFIG.shutdown();
     });