1 files changed, 13 insertions, 1 deletions
diff --git a/src/lib/crypt_ops/crypto_rsa_nss.c b/src/lib/crypt_ops/crypto_rsa_nss.c
index 612b7a0e64..fd8fda486e 100644
--- a/src/lib/crypt_ops/crypto_rsa_nss.c
+++ b/src/lib/crypt_ops/crypto_rsa_nss.c
@@ -679,9 +679,12 @@ crypto_pk_asn1_encode_private(const crypto_pk_t *pk,
 /** Given a buffer containing the DER representation of the
  * private key <b>str</b>, decode and return the result on success, or NULL
  * on failure.
+ *
+ * If <b>max_bits</b> is nonnegative, reject any key longer than max_bits
+ * without performing any expensive validation on it.
  */
 crypto_pk_t *
-crypto_pk_asn1_decode_private(const char *str, size_t len)
+crypto_pk_asn1_decode_private(const char *str, size_t len, int max_bits)
 {
   tor_assert(str);
   tor_assert(len < INT_MAX);
@@ -731,6 +734,15 @@ crypto_pk_asn1_decode_private(const char *str, size_t len)
     output = NULL;
   }
 
+  if (output) {
+    const int bits = SECKEY_PublicKeyStrengthInBits(output->pubkey);
+    if (max_bits >= 0 && bits > max_bits) {
+      log_info(LD_CRYPTO, "Private key longer than expected.");
+      crypto_pk_free(output);
+      output = NULL;
+    }
+  }
+
   if (slot)
     PK11_FreeSlot(slot);