| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Utilities for verifying constant-time programming |
| 4 | * |
| 5 | * (c) 2017 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software: you can redistribute it and/or modify it |
| 13 | * under the terms of the GNU Library General Public License as published |
| 14 | * by the Free Software Foundation; either version 2 of the License, or |
| 15 | * (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, but |
| 18 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 20 | * Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb. If not, write to the Free Software |
| 24 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, |
| 25 | * USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include "config.h" |
| 31 | |
| 32 | #include "ct.h" |
| 33 | |
| 34 | #ifdef HAVE_VALGRIND_H |
| 35 | # include <valgrind/valgrind.h> |
| 36 | # include <valgrind/memcheck.h> |
| 37 | #endif |
| 38 | |
| 39 | /*----- Main code ---------------------------------------------------------*/ |
| 40 | |
| 41 | /* --- @ct_poison@ --- * |
| 42 | * |
| 43 | * Arguments: @const void *p@ = pointer to a secret |
| 44 | * @size_t sz@ = size of the secret |
| 45 | * |
| 46 | * Returns: --- |
| 47 | * |
| 48 | * Use: Ordinarily, does nothing. If the process is running under |
| 49 | * the control of Valgrind's `memcheck' utility, then mark the |
| 50 | * secret as `uninitialized', so that Valgrind warns about |
| 51 | * conditional execution or memory addressing based on the value |
| 52 | * of the secret. |
| 53 | * |
| 54 | * Credit for this idea goes to Adam Langley, who described it |
| 55 | * in https://www.imperialviolet.org/2010/04/01/ctgrind.html, |
| 56 | * though this implementation doesn't require patching Valgrind. |
| 57 | */ |
| 58 | |
| 59 | void ct_poison(const void *p, size_t sz) |
| 60 | { |
| 61 | #ifdef HAVE_VALGRIND_H |
| 62 | VALGRIND_MAKE_MEM_UNDEFINED(p, sz); |
| 63 | #endif |
| 64 | } |
| 65 | |
| 66 | /* --- @ct_remedy@ --- * |
| 67 | * |
| 68 | * Arguments: @const void *p@ = pointer to a secret |
| 69 | * @size_t sz@ = size of the secret |
| 70 | * |
| 71 | * Returns: --- |
| 72 | * |
| 73 | * Use: Ordinarily, does nothing. If the process is running under |
| 74 | * the control of Valgrind's `memcheck' utility, then mark the |
| 75 | * secret as `initialized'. This is intended to reverse the |
| 76 | * effect of @ct_poison@ so that a test program can verify |
| 77 | * function outputs wihtout Valgrind warning. |
| 78 | */ |
| 79 | |
| 80 | void ct_remedy(const void *p, size_t sz) |
| 81 | { |
| 82 | #ifdef HAVE_VALGRIND_H |
| 83 | VALGRIND_MAKE_MEM_DEFINED(p, sz); |
| 84 | #endif |
| 85 | } |
| 86 | |
| 87 | /*----- That's all, folks -------------------------------------------------*/ |