Reject 128-byte keys that are not 1024-bit

When we added the check for key size, we required that the keys be
128 bytes.  But RSA_size (which defers to BN_num_bytes) will return
128 for keys of length 1017..1024.  This patch adds a new
crypto_pk_num_bits() that returns the actual number of significant
bits in the modulus, and uses that to enforce key sizes.

Also, credit the original bug3318 in the changes file.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/common/crypto.c b/src/common/crypto.c
index 1ecc24ce23..d8e6619c9f 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -777,6 +777,17 @@ crypto_pk_keysize(crypto_pk_env_t *env)
   return (size_t) RSA_size(env->key);
 }
 
+/** Return the size of the public key modulus of <b>env</b>, in bits. */
+int
+crypto_pk_num_bits(crypto_pk_env_t *env)
+{
+  tor_assert(env);
+  tor_assert(env->key);
+  tor_assert(env->key->n);
+
+  return BN_num_bits(env->key->n);
+}
+
 /** Increase the reference count of <b>env</b>, and return it.
  */
 crypto_pk_env_t *