Fix memory leak in prop176 code

This fixes part of bug4252.  Bug not in any released version.

src/common/tortls.c

@@ -864,8 +864,8 @@ tor_tls_get_my_client_auth_key(void)
 }
 
 /**
- * Return the public key that a cetificate certifies.  Return NULL if the
- * cert's key is not RSA.
+ * Return a newly allocated copy of the public key that a certificate
+ * certifies.  Return NULL if the cert's key is not RSA.
  */
 crypto_pk_env_t *
 tor_tls_cert_get_key(tor_cert_t *cert)

src/or/command.c

@@ -1190,6 +1190,7 @@ command_process_authenticate_cell(var_cell_t *cell, or_connection_t *conn)
     signed_len = crypto_pk_public_checksig(pk, signed_data, keysize,
                                            (char*)auth + V3_AUTH_BODY_LEN,
                                            authlen - V3_AUTH_BODY_LEN);
+    crypto_free_pk_env(pk);
     if (signed_len < 0) {
       tor_free(signed_data);
       ERR("Signature wasn't valid");