rufuse large RSA keys

Author: Khwahish29

libp2p/crypto/rsa.py

@@ -9,16 +9,36 @@
     pkcs1_15,
 )
 
+from libp2p.crypto.exceptions import (
+    CryptographyError,
+)
 from libp2p.crypto.keys import (
     KeyPair,
     KeyType,
     PrivateKey,
     PublicKey,
 )
 
+MAX_RSA_KEY_SIZE = 4096
+
+
+def validate_rsa_key_size(key: RsaKey) -> None:
+    """
+    Validate that an RSA key's size is within acceptable bounds.
+
+    :param key: The RSA key to validate
+    :raises CryptographyError: If the key size exceeds the maximum allowed size
+    """
+    key_size = key.size_in_bits()
+    if key_size > MAX_RSA_KEY_SIZE:
+        msg = f"RSA key size {key_size} "
+        msg += f"exceeds maximum allowed size {MAX_RSA_KEY_SIZE}"
+        raise CryptographyError(msg)
+
 
 class RSAPublicKey(PublicKey):
     def __init__(self, impl: RsaKey) -> None:
+        validate_rsa_key_size(impl)
         self.impl = impl
 
     def to_bytes(self) -> bytes:
@@ -27,6 +47,7 @@ def to_bytes(self) -> bytes:
     @classmethod
     def from_bytes(cls, key_bytes: bytes) -> "RSAPublicKey":
         rsakey = RSA.import_key(key_bytes)
+        validate_rsa_key_size(rsakey)
         return cls(rsakey)
 
     def get_type(self) -> KeyType:
@@ -43,10 +64,15 @@ def verify(self, data: bytes, signature: bytes) -> bool:
 
 class RSAPrivateKey(PrivateKey):
     def __init__(self, impl: RsaKey) -> None:
+        validate_rsa_key_size(impl)
         self.impl = impl
 
     @classmethod
     def new(cls, bits: int = 2048, e: int = 65537) -> "RSAPrivateKey":
+        if bits > MAX_RSA_KEY_SIZE:
+            msg = f"Requested RSA key size {bits} "
+            msg += f"exceeds maximum allowed size {MAX_RSA_KEY_SIZE}"
+            raise CryptographyError(msg)
         private_key_impl = RSA.generate(bits, e=e)
         return cls(private_key_impl)