Fix/auth fallback (#347)

The [authentication](prefix-dev/pixi#334)
issue was a result of the `~` not being recognized transformed in an
actual home directory. This fixes that.

This also creates a set of defaults, so `pixi` can use the same function
as rattler.

---------

Co-authored-by: Bas Zalmstra <zalmstra.bas@gmail.com>

crates/rattler_networking/src/authentication_storage/fallback_storage.rs

@@ -63,6 +63,10 @@ impl FallbackStorage {
     /// does not exist
     fn read_json(&self) -> Result<std::collections::HashMap<String, String>, FallbackStorageError> {
         if !self.path.exists() {
+            tracing::warn!(
+                "Can't find path for fallback storage on {}",
+                self.path.to_string_lossy()
+            );
             return Ok(std::collections::HashMap::new());
         }
         let file = std::fs::File::open(&self.path)?;

crates/rattler_networking/src/authentication_storage/storage.rs

@@ -19,8 +19,8 @@ pub struct AuthenticationStorage {
     /// in a global dictionary in the operating system
     pub store_key: String,
 
-    /// Fallback Storage
-    fallback_storage: fallback_storage::FallbackStorage,
+    /// Fallback Storage that will be used if the is no key store application available.
+    pub fallback_storage: fallback_storage::FallbackStorage,
 
     /// A cache so that we don't have to access the keyring all the time
     cache: Arc<Mutex<HashMap<String, Option<Authentication>>>>,

crates/rattler_networking/src/lib.rs

@@ -2,16 +2,18 @@
 
 //! Networking utilities for Rattler, specifically authenticating requests
 
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
+use std::sync::OnceLock;
 
 pub use authentication_storage::{authentication::Authentication, storage::AuthenticationStorage};
 use reqwest::{Client, IntoUrl, Method, Url};
 
 pub mod authentication_storage;
 pub mod retry_policies;
 
-/// A client that can be used to make authenticated requests, based on the [`reqwest::Client`]
-#[derive(Clone)]
+/// A client that can be used to make authenticated requests, based on the [`reqwest::Client`].
+/// By default it uses the fallback storage in the default [`default_auth_store_fallback_directory`].
+#[derive(Clone, Default)]
 pub struct AuthenticatedClient {
     /// The underlying client
     client: Client,
@@ -20,12 +22,24 @@ pub struct AuthenticatedClient {
     auth_storage: AuthenticationStorage,
 }
 
-impl Default for AuthenticatedClient {
+/// Returns the default auth storage directory used by rattler.
+/// Would be placed in $HOME/.rattler, except when there is no home then it will be put in '/rattler/'
+pub fn default_auth_store_fallback_directory() -> &'static Path {
+    static FALLBACK_AUTH_DIR: OnceLock<PathBuf> = OnceLock::new();
+    FALLBACK_AUTH_DIR.get_or_init(|| {
+        dirs::home_dir()
+            .map(|home| home.join(".rattler/"))
+            .unwrap_or_else(|| {
+                tracing::warn!("using '/rattler' to store fallback authentication credentials because the home directory could not be found");
+                // This can only happen if the dirs lib can't find a home directory this is very unlikely.
+                PathBuf::from("/rattler/")
+            })
+    })
+}
+
+impl Default for AuthenticationStorage {
     fn default() -> Self {
-        AuthenticatedClient {
-            client: Client::default(),
-            auth_storage: AuthenticationStorage::new("rattler", &PathBuf::from("~/.rattler")),
-        }
+        AuthenticationStorage::new("rattler", default_auth_store_fallback_directory())
     }
 }
 
@@ -113,6 +127,8 @@ impl AuthenticatedClient {
 
 #[cfg(feature = "blocking")]
 /// A blocking client that can be used to make authenticated requests, based on the [`reqwest::blocking::Client`]
+/// By default it uses the fallback storage in the default [`default_auth_store_fallback_directory`].
+#[derive(Default)]
 pub struct AuthenticatedClientBlocking {
     /// The underlying client
     client: reqwest::blocking::Client,
@@ -135,16 +151,6 @@ impl AuthenticatedClientBlocking {
     }
 }
 
-#[cfg(feature = "blocking")]
-impl Default for AuthenticatedClientBlocking {
-    fn default() -> Self {
-        AuthenticatedClientBlocking {
-            client: Default::default(),
-            auth_storage: AuthenticationStorage::new("rattler", &PathBuf::from("~/.rattler")),
-        }
-    }
-}
-
 #[cfg(feature = "blocking")]
 impl AuthenticatedClientBlocking {
     /// Create a GET request builder for the given URL (see also [`reqwest::blocking::Client::get`])