Preserve 'secret_key' in 'Config' provider data.

Also fixes emission of 'secret_key' warnings when 'secrets' feature is
disabled.

Resolves #1505.
Fixes #1510.

core/http/src/cookies.rs

@@ -24,6 +24,10 @@ mod key {
         pub fn derive_from(_: &[u8]) -> Self { Key }
         pub fn generate() -> Self { Key }
         pub fn try_generate() -> Option<Self> { Some(Key) }
+        pub fn master(&self) -> &[u8] {
+            static ZERO: &'static [u8; 64] = &[0; 64];
+            &ZERO[..]
+        }
     }
 
     impl PartialEq for Key {

core/lib/src/config/config.rs

@@ -223,7 +223,7 @@ impl Config {
             panic!("aborting due to configuration error(s)")
         });
 
-        #[cfg(all(feature = "secrets", not(test), not(rocket_unsafe_secret_key)))] {
+        #[cfg(all(feature = "secrets", not(test), not(rocket_unsafe_secret_key)))]
         if !config.secret_key.is_provided() {
             if figment.profile() != Self::DEBUG_PROFILE {
                 crate::logger::try_init(LogLevel::Debug, true, false);
@@ -235,7 +235,6 @@ impl Config {
             // in debug, generate a key for a bit more security
             config.secret_key = SecretKey::generate().unwrap_or(SecretKey::zero());
         }
-        }
 
         config
     }
@@ -284,6 +283,7 @@ impl Config {
             false => launch_info_!("tls: {}", Paint::default("disabled").bold()),
         }
 
+        #[cfg(all(feature = "secrets", not(test), not(rocket_unsafe_secret_key)))]
         if !self.secret_key.is_provided() {
             warn!("secrets enabled without a configured `secret_key`");
             info_!("disable `secrets` feature or configure a `secret_key`");
@@ -313,7 +313,15 @@ impl Provider for Config {
 
     #[track_caller]
     fn data(&self) -> Result<Map<Profile, Dict>> {
-        Serialized::defaults(self).data()
+        let mut map: Map<Profile, Dict> = Serialized::defaults(self).data()?;
+        // We need to special-case `secret_key` since its serializer zeroes.
+        if !self.secret_key.is_zero() {
+            if let Some(map) = map.get_mut(&Profile::Default) {
+                map.insert("secret_key".into(), self.secret_key.master().into());
+            }
+        }
+
+        Ok(map)
     }
 
     fn profile(&self) -> Option<Profile> {

core/lib/src/config/secret_key.rs

@@ -27,7 +27,10 @@ enum Kind {
 /// let figment = Figment::from(rocket::Config::default())
 ///     .merge(("secret_key", "hPRYyVRiMyxpw5sBB1XeCMN1kFsDCqKvBi2QJxBVHQk="));
 ///
+/// # #[cfg(feature = "secrets")]
 /// assert!(!rocket::Config::from(figment).secret_key.is_zero());
+/// # #[cfg(not(feature = "secrets"))]
+/// # assert!(rocket::Config::from(figment).secret_key.is_zero());
 ///
 /// let figment = Figment::from(rocket::Config::default())
 ///     .merge(("secret_key", vec![0u8; 64]));
@@ -42,16 +45,16 @@ enum Kind {
 ///
 /// [private cookies]: https://rocket.rs/master/guide/requests/#private-cookies
 /// [configuration guide]: https://rocket.rs/master/guide/configuration/#secret-key
-#[derive(PartialEq, Clone)]
+#[derive(Clone)]
 pub struct SecretKey {
     key: Key,
-    kind: Kind,
+    provided: bool,
 }
 
 impl SecretKey {
     /// Returns a secret key that is all zeroes.
     pub(crate) fn zero() -> SecretKey {
-        SecretKey { key: Key::from(&[0; 64]), kind: Kind::Zero }
+        SecretKey { key: Key::from(&[0; 64]), provided: false }
     }
 
     /// Creates a `SecretKey` from a 512-bit `master` key. For security,
@@ -70,12 +73,7 @@ impl SecretKey {
     /// let key = SecretKey::from(&master);
     /// ```
     pub fn from(master: &[u8]) -> SecretKey {
-        let kind = match master.iter().all(|&b| b == 0) {
-            true => Kind::Zero,
-            false => Kind::Provided
-        };
-
-        SecretKey { key: Key::from(master), kind }
+        SecretKey { key: Key::from(master), provided: true }
     }
 
     /// Derives a `SecretKey` from 256 bits of cryptographically random
@@ -94,7 +92,7 @@ impl SecretKey {
     /// let key = SecretKey::derive_from(&material);
     /// ```
     pub fn derive_from(material: &[u8]) -> SecretKey {
-        SecretKey { key: Key::derive_from(material), kind: Kind::Provided }
+        SecretKey { key: Key::derive_from(material), provided: true }
     }
 
     /// Attempts to generate a `SecretKey` from randomness retrieved from the
@@ -108,7 +106,7 @@ impl SecretKey {
     /// let key = SecretKey::generate();
     /// ```
     pub fn generate() -> Option<SecretKey> {
-        Some(SecretKey { key: Key::try_generate()?, kind: Kind::Generated })
+        Some(SecretKey { key: Key::try_generate()?, provided: false })
     }
 
     /// Returns `true` if `self` is the `0`-key.
@@ -123,7 +121,7 @@ impl SecretKey {
     /// assert!(key.is_zero());
     /// ```
     pub fn is_zero(&self) -> bool {
-        self.kind == Kind::Zero
+        self == &Self::zero()
     }
 
     /// Returns `true` if `self` was not automatically generated and is not zero.
@@ -142,7 +140,7 @@ impl SecretKey {
     /// assert!(!key.is_provided());
     /// ```
     pub fn is_provided(&self) -> bool {
-        self.kind == Kind::Provided
+        self.provided && !self.is_zero()
     }
 }
 
@@ -155,6 +153,13 @@ impl Deref for SecretKey {
     }
 }
 
+impl PartialEq for SecretKey {
+    fn eq(&self, other: &Self) -> bool {
+        // `Key::partial_eq()` is a constant-time op.
+        self.key == other.key
+    }
+}
+
 #[crate::async_trait]
 impl<'a, 'r> FromRequest<'a, 'r> for &'a SecretKey {
     type Error = std::convert::Infallible;
@@ -228,10 +233,13 @@ impl<'de> Deserialize<'de> for SecretKey {
 
 impl fmt::Debug for SecretKey {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self.kind {
-            Kind::Zero => f.write_str("[zero]"),
-            Kind::Generated => f.write_str("[generated]"),
-            Kind::Provided => f.write_str("[provided]"),
+        if self.is_zero() {
+            f.write_str("[zero]")
+        } else {
+            match self.provided {
+                true => f.write_str("[provided]"),
+                false => f.write_str("[generated]"),
+            }
         }
     }
 }

core/lib/tests/config-secret-key-1500.rs

@@ -0,0 +1,12 @@
+use rocket::figment::Figment;
+use rocket::config::{Config, SecretKey};
+
+#[test]
+fn secret_key_in_config_not_zero() {
+    let original_key = SecretKey::generate().expect("get key");
+
+    let config = Config { secret_key: original_key.clone(), ..Default::default() };
+    let figment = Figment::from(config);
+    let figment_key: SecretKey = figment.extract_inner("secret_key").unwrap();
+    assert_eq!(original_key, figment_key);
+}