fix(servo): gate vulnerable RSA private operations

third_party/rsa/src/pkcs1v15/decrypting_key.rs

@@ -0,0 +1,86 @@
+use super::{decrypt, EncryptingKey};
+use crate::{
+    dummy_rng::DummyRng,
+    traits::{Decryptor, EncryptingKeypair, RandomizedDecryptor},
+    Result, RsaPrivateKey,
+};
+use alloc::vec::Vec;
+use rand_core::CryptoRng;
+#[cfg(feature = "serde")]
+use serde::{Deserialize, Serialize};
+use zeroize::ZeroizeOnDrop;
+
+/// Decryption key for PKCS#1 v1.5 decryption as described in [RFC8017 § 7.2].
+///
+/// [RFC8017 § 7.2]: https://datatracker.ietf.org/doc/html/rfc8017#section-7.2
+#[derive(Debug, Clone, PartialEq)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct DecryptingKey {
+    inner: RsaPrivateKey,
+}
+
+impl DecryptingKey {
+    /// Create a new verifying key from an RSA public key.
+    pub fn new(key: RsaPrivateKey) -> Self {
+        Self { inner: key }
+    }
+}
+
+impl Decryptor for DecryptingKey {
+    fn decrypt(&self, ciphertext: &[u8]) -> Result<Vec<u8>> {
+        decrypt::<DummyRng>(None, &self.inner, ciphertext)
+    }
+}
+
+impl RandomizedDecryptor for DecryptingKey {
+    fn decrypt_with_rng<R: CryptoRng + ?Sized>(
+        &self,
+        rng: &mut R,
+        ciphertext: &[u8],
+    ) -> Result<Vec<u8>> {
+        decrypt(Some(rng), &self.inner, ciphertext)
+    }
+}
+
+impl EncryptingKeypair for DecryptingKey {
+    type EncryptingKey = EncryptingKey;
+    fn encrypting_key(&self) -> EncryptingKey {
+        EncryptingKey {
+            inner: self.inner.clone().into(),
+        }
+    }
+}
+
+impl ZeroizeOnDrop for DecryptingKey {}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    #[cfg(all(feature = "hazmat", feature = "serde"))]
+    fn test_serde() {
+        use super::*;
+        use rand::rngs::ChaCha8Rng;
+        use rand_core::SeedableRng;
+        use serde_test::{assert_tokens, Configure, Token};
+
+        let mut rng = ChaCha8Rng::from_seed([42; 32]);
+        let decrypting_key = DecryptingKey::new(
+            RsaPrivateKey::new_unchecked(&mut rng, 64).expect("failed to generate key"),
+        );
+
+        let tokens = [
+            Token::Struct {
+                name: "DecryptingKey",
+                len: 1,
+            },
+            Token::Str("inner"),
+            Token::Str(concat!(
+                "3056020100300d06092a864886f70d010101050004423040020100020900ab",
+                "240c3361d02e370203010001020811e54a15259d22f9020500ceff5cf30205",
+                "00d3a7aaad020500ccaddf17020500cb529d3d020500bb526d6f"
+            )),
+            Token::StructEnd,
+        ];
+        assert_tokens(&decrypting_key.readable(), &tokens);
+    }
+}