include NaCl error message in the exception raised from verify()

src/sso/sso.h

@@ -37,14 +37,20 @@ namespace sso {
 class sso_error : public std::exception {
 public:
   sso_error(const char *s)
-  : str_(s)
+    : str_(s)
   {}
-  
+
+  sso_error(const std::string& s)
+    : str_(s)
+  {}
+
+  virtual ~sso_error() throw() {}
+
   const char *what() const throw() {
-    return str_;
+    return str_.c_str();
   }
 
-  const char *str_;
+  std::string str_;
 };
 
 std::string read_key_from_file(const std::string& path);

src/sso/verifier.cc

@@ -69,8 +69,11 @@ Ticket *Verifier::verify(const string& ticket_string) throw(sso_error)
  
     // Decode the ticket from the unsigned string.
     ticket = new Ticket(verified_ticket_string);
-  } catch(...) {
-    throw sso_error("signature verification failure");
+  } catch(const char *err) {
+    // Yes, NaCl throws a const char*.
+    string reason("signature verification failure: ");
+    reason += err;
+    throw sso_error(reason);
   }
  
   // Verification phase.